CellsBy: Breanna Oquendo, Kitty Katrina I. Timbers,

Anna Huffman, and Kaylon Kennedy

*Word will be defined again in a later chapter

Vocab• Light microscope (LM)-an optical instrument with lenses that

refract (bend) visible light to magnify images of specimens • Electron microscope (EM)-a microscope that uses magnets to

focus an electron beam on or through a specimen, resulting in resolving power a thousandfold greater than that of a light microscope (2 types: scanning and transmission)

• Scanning electron microscope (SEM)-a microscope that uses an electron beam to scan the surface of a sample to study details of its topography; used to study the fine details of cell surfaces

• Transmission electron microscope (TEM)-a microscope that passes an electron beam through very thin sections and is used to study the internal ultrastructure of cells

• Cell fractionation-the disruption of a cell and separation of its parts by centrifugation

• Organelle-any of several membrane-enclosed structures with specialized functions, suspended in the cytosol of eukaryotic cells

• Cytosol-the semifluid portion of the cytoplasm• Cytoplasm-the contents of the cell, exclusive of the nucleus and

bounded by the plasma membrane• Plasma membrane-the membrane at the boundary of every cell that

acts as a selective barrier, regulating the cell’s chemical composition• Ribosomes-a complex of rRNA and protein molecules that

functions as a site of protein synthesis in the cytoplasm; consists of a large and a small subunit. (In eukaryotic cells, each subunit is assembled in the nucleolus)

• Nucleoid-a dense region of DNA in a prokaryotic cell• Nucleus-the chromosome-containing organelle of a eukaryotic cell• Nuclear envelope-the double membrane in a eukaryotic cell that

encloses the nucleus, separating it from the cytoplasm• Nuclear lamina-a netlike array of protein filaments lining the inner

surface of the nuclear envelope; it helps maintain the shape of the nucleus

• Nucleolus-a specialized structure in the nucleus, consisting of chromatin regions containing ribosomal RNA genes along with ribosomal proteins imported from the cytoplasmic site of rRNA synthesis and subunit assembly

• Endoplasmic reticulum (ER)-an extensive membranous network in eukaryotic cells, continuous with the outer nuclear membrane and composed of ribosome-studded (rough) and ribosome-free (smooth) regions

• Smooth ER-that portion of the endoplasmic reticulum that is free of ribosomes

• Rough ER-that portion of the endoplasmic reticulum studded with ribosomes

• *Glycoproteins-a protein with one or more carbohydrates covalently attached to it

• Vesicles-sacs made of membrane in the cytoplasm• Transport vesicle-a tiny membranous sac in a cell’s cytoplasm

carrying molecules produced by the cell• Food vacuoles-membranous sacs formed by phagocytosis of

microorganisms or particles to be used as food by the cell• Contractile vacuole-a membranous sac that helps move excess

water out of certain freshwater protists• Central vacuole-a membranous sac in a mature plant cell with

diverse roles in reproduction, growth, and development

• Endomembrane system-the collection of membranes inside and around a eukaryotic cell, related either through direct physical contact or by the transfer of membranous vesicles; includes the smooth and rough endoplasmic reticulum, the Golgi apparatus, lysosomes, and vacuoles

• Eukaryotic cell-a type of cell with a membrane-enclosed nucleus and membrane-enclosed organelles. Organisms with eukaryotic cells (protists, plants fungi and animals) are called eukaryotes.

• Prokaryotic cell-a type of cell lacking a membrane-enclosed nucleus and membrane-enclosed organelles. Organisms with prokaryotic cells (bacteria and archaea) are called prokaryotes

• *Chromosomes- a cellular structure carrying genetic material, found in the nucleus of eukaryotic cells; consists of one very long DNA molecule and associated proteins (A bacterial chromosome consists of a single circular DNA molecule and associated proteins and is found in the nucleoid region)

• *Chromatin-the complex of DNA and protein that makes up a eukaryotic chromosome (dispersed form, which occurs when the cell is not dividing, is a mass of very long, thin fibers that are not visible with a light microscope)

• Golgi apparatus-an organelle in eukaryotic cells consisting of stacks of flat membranous sacs that modify, store, and route products of the endoplasmic reticulum and synthesize some products, notably non-cellulose carbohydrates

• Lysosome-a membrane-enclosed sac of hydrolytic enzymes found in the cytoplasm of animal cells and some protists

• *Phagocytosis- a type of endocytosis in which large particulate substances are taken up by a cell. It is carried out by some protists and by certain immune cells of animals

• Mitochondrion-an organelle in eukaryotic cells that serves as thee site of cellular respiration

• Chloroplast-an organelle found in plants and photosynthetic protists that absorbs sunlight and uses it to drive the synthesis of organic compounds from carbon dioxide and water

• Peroxisome-an organelle containing enzymes that transfer hydrogen from various substrates to oxygen, producing and then degrading hydrogen peroxide

• Crista-an infolding of the inner membrane of a mitochondrion that houses electron transport chains and molecules of the enzyme catalyzing the synthesis of ATP (ATP synthase)

• Mitochondrial matrix-the compartment of the mitochondrion enclosed by the inner membrane and containing enzymes and substances for the citric acid cycle

• Plastids-one of a family of closely related organelles that includes chloroplasts, chromoplasts, and amyloplasts (leucoplasts) (found in cells of photosynthetic organisms)

• Thylakoids-flattened membranous sacs inside a chloroplast that exist in an interconnected system (contain the molecular “machinery” used to convert light energy to chemical energy)

• Granum-a stack of membrane-bound thylakoids in the chloroplasts that function in the light reactions of photosynthesis

• Stroma-within the chloroplast, the dense fluid of the chloroplast surrounding the thylakoid membrane; involved in the synthesis of organic molecules from carbon dioxide and water

• Cytoskeleton-a network of microtubules, microfilaments, and intermediate filaments that branch throughout the cytoplasm and serve a variety of mechanical, transport, and signaling functions

• Motor proteins-proteins that interact with cytoskeletal elements and other cell components, producing movement of the whole cell or parts of the cell

• Microtubules-hollow rods composed of tubulin proteins that make up part of the cytoskeleton in all eukaryotic cells and are found in cilia and flagella

• *Centrosome-structure made of two centrioles present in the cytoplasm of animal cells, important during cell division; functions as a microtubule-organizing center

• Centriole-a structure in the centrosome of an animal cell composed of a cylinder of microtubule triplets arranged in a 9 + 0 pattern

• Flagellum-a long cellular appendage specialized for locomotion. Like motile cilia, eukaryotic flagella have a core with nine outer doublet microtubules and two inner single microtubules ensheathed in an extension of the plasma membrane. Prokaryotic flagella have a different structure.

• Cilium-a short cellular appendage containing microtubules.~motile cilium-specialized for locomotion and is formed from a core of nine outer doublet microtubules and two inner single microtubules (the “9+2” arrangement) ensheathed in an extension of the plasma membrane~primary cilium-nonmotile; plays a sensory and signaling role; it lacks the two inner microtubules (the “9+0” arrangement)

• Basal body-a eukaryotic cell structure consisting of a 9 + 0 arrangement of microtubule triplets. The basal body may organize the microtubule assembly of a cilium or flagellum and is structurally very similar to a centriole.

• Dyneins-in cilia and flagella, a large contractile protein extending from one microtubule doublet to the adjacent doublet. ATP hydrolysis drives changes in dynein shape that lead to bending of cilia and flagella

• Microfilament (actin filament)-a cable composed of actin proteins in the cytoplasm of almost every eukaryotic cell, making up part of the cytoskeleton and acting alone or with myosin to cause cell contraction

• Actin-a globular protein that links into chains, two of which twist helically about each other, forming microfilaments (actin filaments) in muscle and other kinds of cells

• Cortex-the outer region of cytoplasm in a eukaryotic cell, lying just under the plasma membrane, that has a more gel-like consistency than the inner regions, due to the presence of multiple microfilaments

• Myosin-a type of protein filament that acts as a motor protein with actin filaments to cause cell contraction

• Pseudopodium-a cellular extension of amoeboid cells used in moving and feeding

• Cytoplasmic streaming-a circular flow of cytoplasm, involving myosin and actin filaments, that speeds the distribution of materials with in cells

• Intermediate filament-a component of the cytoskeleton that includes filaments intermediate in size between microtubules and microfilaments

• Cell wall-a protective layer external to the plasma membrane in the cells of plants, prokaryotes, fungi, and some protists (polysaccharides such as cellulose, chitin, and peptidoglycan are an important structural component of cell walls)

• Primary cell wall-in plants, a relatively thin and flexible layer first secreted by a young cell

• Middle lamella-in plants, a thin layer of adhesive extracellular material, primarily pectins, found between the primary walls of adjacent young cells

• Secondary cell wall-in plants, a strong and durable matrix often deposited in several laminated layers for cell protection and support

• Extracellular matrix (ECM)-the substance in which animal cells are embedded, consisting of protein and polysaccharides synthesized and secreted by cells

• Collagen-a glycoprotein in the extracellular matrix of animal cells that forms strong fibers, found extensively in connective tissue and bone; the most abundant protein in the animal kingdom

• Proteoglycan-a glycoprotein consisting of a small core protein with many carbohydrate chains attached, found in the extracellular matrix of animal cells (may consist of up to 95% carbohydrate)

• Fibronectin-a glycoprotein that helps animal cells attach to the extracellular matrix

• Integrins-in animal cells, a transmembrane receptor protein that interconnects the extracellular matrix and the cytoskeleton

• Plasmodesma-an open channel in the cell wall of a plant through which strands of cytosol connect from an adjacent cell

• Tight junction-a type of intercellular junction in animal cells that prevents the leakage of material between cells

• Desmosomes-a type of intercellular junction in animal cells that functions as a rivet

• Gap junctions-a type of intercellular junction in animals that allows the passage of materials between cells

1) Cells Are Studied Under Microscopes

• Cells are the most basic unit of life• Too small to be seen with the naked eye, so

we use microscopes

Light Microscope

• .2 um• 200 nm• Magnifies up to 1000x• Uses light and needs contrast

Scanning Electron Microscope

• .2 um and smaller• Beams of electron• Used for details of surface of specimen

Transmission Electron

• Study internal ultrastructure of cells• Organelle slides can be made by using cell

fractionation• Separates parts of cell

2) Cells Complex Structures/Function

• Nucleus-houses chromosomes(DNA), contains nucleoli

• Ribosome-makes proteins• ER1.Smooth- makes lipids, metabolizes carbs, Ca

2+ storage, detoxifies2.Rough- helps make proteins, produces new

membrane

• Golgi- modifies proteins, makes polysaccharides, packaging/shipping

• Lysosome- breaks down “food” and damaged organelles

• Vacuole- digestion, storage, waste disposal, water balance, cell growth, and protection (plants only)

• Cytosol- contains organelles• Plasma membrane- controls cell intake and

output • Mitochondrion-cellular respiration• Chloroplast-photosynthesis• Peroxisome- produces hydrogen peroxide and

converts it to water• Cytoskeleton- structural support, mobility, and

signal transmission

3) Prokaryotic vs. EukaryoticProkaryotic Eukaryotic

• DNA in nucleoid • DNA found in nucleus

• Has hard capsule and cell wall • Only cell wall in plant; no capsule

• Only free ribosomes • Ribosomes are free and on the ER

4) Extracellular and Intracellular Components

• Cell Wall- 3 layers to add strength and structure

• ECM- complex network outside cell membrane that helps regulate cell behavior

• Plasmodesmata- channels in cell wall that connects plants cells

• Gap Junctions- in animal cells• Tight Junctions and Desmosomes- keep cells

together and protect from leakage

This chart shows the various parts and functions of the cell. It includes the nucleus, cell membrane, cytoplasm, ribosomes, endoplasmic reticulum, mitochondria, golgi bodies, lysosomes, vacuoles, cell wall, and chloroplasts. The nucleus is made up of chromatin and contains nucleoli which is where ribosomal subunits are made. The cell membrane forms the boundary for the cell and selectively permits the passage of materials into and out of the cell. The cytoplasm is a jelly-like substance that helps keep the organelles inside the cell. The ribosomes can be found in the cytoplasm or on the rough ER and are sites of protein synthesis. The ER can be rough or smooth. The smooth ER synthesizes lipids, metabolizes carbs, and detoxifies drugs and poisons while the rough ER transports aids in synthesis of secretory and other proteins from bound ribosomes . Mitochondria is where cellular respiration occurs and most of the ATP is generated. The Golgi Apparatus is active in synthesis, modification, sorting, and secretion of cell products. Lysosomes are digestive organelles where macromolecules are hydrolyzed. Vacuoles function as a storage, hydrolyze macromolecules, and break down waste products in plant cells. The cell wall provides a shape in plant cells. The chloroplasts convert the energy of the sunlight into chemical energy stored in sugar molecules.

Comparison of a Plant and Animal Cell

Animal Cell Plant Cell

These two pictures show the difference between a plant and animal cell. Animal cells have lysosomes, centrosomes, and flagella (some are present in plant sperm) while plant cells do not. The centrosome is an area where the cell’s microtubules are initiated and they contain a pair of centrioles. The function is unknown. Flagella is made up of a cluster of microtubules within an extension of the plasma membrane and allows the animal cell to move. Plant cells have chloroplasts, central vacuoles, cell wall, and plasmodesmata while animal cells do not. The plasmodesmata connect the cytoplasm of adjacent cells and allow the passage of some molecules from cell to cell.

Question 1

All organisms are made out ofA. TissueB. CellsC. BonesD. Blood

Question 2

An organelle present in a prokaryotic cell isA. ERB. Nuclear envelopeC. RibosomesD. Chloroplast

Question 3

The surface to volume ration is used to measure cell

A. SizeB. ShapeC. Size and shapeD. None of the above

Question 4

Active transport happens in theA. Outside of the cellB. The cellC. The cell wallD. Your dog

Question 5

Microscopy includes the use of A. Light microscopesB. Electron microscopesC. Scanning/Transmission microscopesD. All of the above

**Word has been previously defined

Vocab• Selective permeability-a property of biological membranes

that allows them to regulate the passage of substances• Amphipathic-having both a hydrophilic region and a

hydrophobic region• Fluid mosaic model-the currently accepted model of cell

membrane structure, which envisions the membrane as a mosaic of protein molecules drifting laterally in a fluid bilayer of phospholipids

• Integral proteins-typically a transmembrane protein with hydrophobic regions that extend into and often completely span the hydrophobic interior of the membrane and with hydrophilic regions in contact with the aqueous solution on either side of the membrane (or lining the channel in the case of a channel protein)

• Peripheral proteins-a protein loosely bound to the surface of a membrane or to part of an integral protein and not embedded in the lipid bilayer

• Glycolipids-a lipid with covalently attached carbohydrate(s)• **Glycoproteins- a protein with one or more carbohydrates

covalently attached to it• Transport protein-a transmembrane protein that helps a

certain substance or class of closely related substances to cross the membrane

• Aquaporin-a channel protein in the plasma membrane of a plant, animal, or microorganism cell that specifically facilitates osmosis, the diffusion of water across the membrane

• Diffusion-the spontaneous movement of a substance down its concentration gradient, from a region where it is more concentrated to a region where it is less concentrated

• Concentration gradient-a region along which the density of a chemical substance increases or decreases

• Passive transport-the diffusion of a substance across a biological membrane with no expenditure of energy

• Osmosis-the diffusion of water across a selectively permeable membrane

• Tonicity-the ability of a solution surrounding a cell to cause that cell to gain or lose water

• Isotonic-referring to a solution that, when surrounding a cell, has no effect on the passage of water into or out of the cell

• Hypertonic-referring to a solution that, when surrounding a cell, will cause the cell to lose water

• Hypotonic-referring to a solution that, when surrounding a cell, will cause the cell to take up water

• Osmoregulation-regulation of solute concentrations and water balance by a cell or organism

• Turgid-swollen or distended (a walled cell becomes turgid if it has a greater solute concentration than its surroundings, resulting in entry of water)

• Flaccid-limp; lacking in stiffness or firmness• Plasmolysis-a phenomenom in walled cells in which the

cytoplasm shrivels and the plasma membrane pulls away from the cell wall; occurs when the cell loses water to a hypertonic environment

• Facilitated diffusion-the spontaneous passage of molecules or ions across a biological membrane with the assistance of specific transmembrane transport proteins

• Ion channels-a transmembrane protein channel that allows a specific ion to flow across the membrane down its concentration gradient

• Gated channels-a transmembrane protein channel that opens or closes in response to a particular stimulus

• Active transport-the movement of a substance across a cell membrane, with an expenditure of energy, against its concentration or electrochemical gradient; mediated by specific transport proteins

• Sodium-potassium pump-a transport protein in the plasma membrane of animal cells that actively transports sodium out of the cell and potassium into the cell

• Membrane potential-the difference in electrical charge (voltage) across a cell’s plasma membrane, due to the differential distribution of ions; this affects the activity of excitable cells and the transmembrane movement of all charged substances

• Electrochemical gradient-the diffusion gradient of an ion, which is affected by both the concentration difference of the ion across a membrane (a chemical force) and the ion’s tendency to move relative to the membrane potential (an electrical force)

• Electrogenic pump-an ion transport protein that generates voltage across a membrane

• Proton pump-an active transport protein in a cell membrane that uses ATP to transport hydrogen ions out of a cell against their concentration gradient, generating a membrane potential in the process

• Cotransport-the coupling of the “downhill” diffusion of one substance to the “uphill” transport of another against its own concentration gradient

• Exocytosis-the cellular secretion of biological molecules by the fusion of vesicles containing them with the plasma membrane

• Endocytosis-cellular uptake of biological molecules and particulate matter via formation of new vesicles from the plasma membrane

• **Phagocytosis-a type of endocytosis in which large particulate substances are taken up by a cell. It is carried out by some protists and by certain immune cells of animals

• Pinocytosis-a type of endocytosis in which the cell ingests extracellular fluid and its dissolved solutes

• Receptor-mediated endocytosis-the movement of specific molecules into a cell by the inward budding of membranous vesicles containing proteins with receptor sites specific to the molecules being taken in; enables a cell to acquire bulk quantities of specific substances

• Ligand-a molecule that binds specifically to another molecule, usually a larger one

5) Membrane Structure

• Selective permeability- allows some substances to cross it more easily than others

• Amphipathic- has both hydrophilic and hydrophobic

• Fluid Mosaic Model- proteins dispersed in or attached to a bilayer of phospholipids

• Phospholipids can move laterally or flip-flop• Kinks of unsaturated phospholipids cause fluidity• Cholesterol reduces membrane fluidity

6) Osmosis and Diffusion

• Concentration gradient (causes osmosis and diffusion)- substances move to less concentrated areas

Diffusion- movement of a substance goes down the concentration gradient

Osmosis- movement of water down the concentration gradient

• Isotonic– Cell and outside fluid have equal concentration– No effect(flaccid, limp in plants)

• Hypotonic– Less solute outside – Water goes in cell– Cell lyses– Normal in plant

• Hypertonic– More solute outside– Water leaves cell– Cell shrivels– Plasmolyzed in plants

7) Passive vs. Active TransportPassive Active

• Diffusion/osmosis • Energy required (ATP)

• No energy needed • Sodium-Potassium pump

• Aquaporins (water channels) • Electrogenic pump- generates voltage across membrane

• Facilitated Diffusion- aid of proteins (includes channel proteins, carrier proteins, ion channels, and gated channels)

• Co-transport- ATP powered pump transports a solute that indirectly causes active transport of another substance

• Moves down the concentration gradient

• Moves up the concentration gradient

• Proton pump

8) Exocytosis and Endocytosis• Exocytosis- vesicles from Golgi carry waste out of

cell• Endocytosis- molecules taken in by pinching off

part of plasma membrane• Phagocytosis- arm-like pseudopodium engulfs

food • Pinocytosis- cell “gulps” extracellular fluid and

the molecules in it• Receptor mediated endocytosis-attachment of

ligand to receptors on cell membrane causes endocytosis

Animal Cell’s Plasma Membrane

The plasma membrane is selectively permeable (allows some substances to cross it more easily than others) and is made of phospholipids. The proteins held together by weak interactions cause the membrane to be fluid. Some organic molecules found on the membrane are phospholipids, integral proteins, peripheral proteins, and carbohydrates. Phospholipids provide a hydrophobic barrier that separates the cell from its liquid environment. Hydrophilic molecules cannot easily enter the cell, but hydrophobic molecules can enter easily. Integral proteins are embedded in the membrane and peripheral proteins are loosely bound to the membrane’s surface. Carbohydrates are needed in cell-cell recognition and help develop organisms. Cell surface carbohydrates are different from species to species and are the reason that blood transfusions must be type-specific.

Exocytosis and Endocytosis

Large molecules are moved across the cell membrane through exocytosis and endocytosis. In exocytosis, vesicles from the cell’s interior fuse with the cell membrane. In endocytosis, the cell forms new vesicles from the plasma membrane. There are three types of endocytosis: phagocytosis, pinocytosis, and receptor-mediated endocytosis. In phagocytosis, the cell wraps pseudopodia around a solid particle and brings it into the cell. In pinocytosis, the cell takes in small droplets of extracellular fluid within small vesicles. In receptor-mediated endocytosis, certain substances bind to specific receptors on the cell’s surface and this causes a vesicle to form around the substance and then to pinch off into the cytoplasm.

Question 6

Which process includes all othersA. OsmosisB. Diffusion across a membraneC. Passive transportD. Facilitated diffusion

Question 7

Isotonic, hypotonic, and hypertonic areA. Forms of osmosisB. Forms of diffusionC. Forms of meiosisD. Forms of mitosis

Question 8

Exocytosis isA. The transport of lysesB. When transport vesicles migrate to the plasma

membraneC. A totally new way to do osmosisD. None of the above

Question 9

The fluid mosaic model says that cells haveA. Water poresB. Protein pores C. Phosphate bilayerD. Amphipathic proteins

Question 10

Passive transport A. Uses energyB. Does not use energyC. Is considered facilitated diffusion D. All of the above

**Word has been previously defined

Vocab• Signal transduction pathway-a series of steps linking a mechanical

or chemical stimulus to a specific cellular response• Mating type a-cells that secrete a factor which binds to α cells’

specific protein receptors• Mating type α-cells that secrete α factor which binds to a cells’

specific protein receptors• Local regulator-a secreted molecule that influences cells near

where it is secreted• Hormones-in multicellular organisms, one of the many types of

secreted chemicals that are formed in specialized cells, travel in body fluids, and act on specific target cells in other parts of the body to change their functioning

• Reception-the target cell’s detection of a signaling molecule coming from outside the cell

• Transduction-the conversion of a signal from outside the cell to a form that can bring about a specific cellular response

• Response-the change in a specific cellular activity brought about by a transduced signal from outside the cell

• **Ligand- a molecule that binds specifically to another molecule, usually a larger one

• G protein-coupled receptor (G protein-linked receptor)-a signal receptor protein in the plasma membrane that responds to the binding of a signaling molecule by activating a G protein

• G protein-a GTP-binding protein that relays signals from a plasma membrane signal receptor, known as a G protein-coupled receptor, to other signal transduction proteins inside the cell

• Receptor tyrosine kinase-a receptor protein in the plasma membrane, the cytoplasmic (intracellular) part of which can catalyze the transfer of a phosphate group from ATP to a tyrosine on another protein. It responds to the binding of a signaling molecule by dimerizing and then phosphorylating a tyrosine on the cytoplasmic portion of the other receptor in the dimer; the phosphorylated tyrosines on the receptors then activate other signal transduction proteins within the cell

• Ligand-gated ion channel-a protein pore in cellular membranes that opens or closes in response to a signaling chemical (its ligand), allowing or blocking the flow of specific ions

• Protein kinase-an enzyme that transfers phosphate groups from ATP to a protein, thus phosphorylating the protein

• Protein phosphatases-an enzyme that removes phosphate groups from (dephosphorylates) proteins, often functioning to reverse the effect of a protein kinase

• Second messenger-a small, nonprotein, water-soluble molecule or ion that relays a signal to a cell’s interior in response to a signaling molecule bound by a signal receptor protein

• Cyclic AMP (cAMP)-cyclic adenosine monophosphate, a ring-shaped molecule made from ATP that is a common intracellular signaling molecule (second messenger) in eukaryotic cells; also a regulator of some bacterial operons

• Adenylyl cyclase-an enzyme that converts ATP to cyclic AMP in response to a signal

• Inositol trisphosphate (IP3)-a second messenger that functions as an intermediate between certain nonsteroid hormones and a third messenger, a rise in cytoplasmic concentraion of calcium ions

• Diacylglycerol (DAG)-a second messenger produced by the cleavage of a certain kind of phospholipid in the plasma membrane

• Scaffolding protein-a type of large relay protein to which several other relay proteins are simultaneously attached, increasing the efficiency of signal transduction

• Apoptosis-a program of controlled cell suicide, which is brought about by signals that trigger the activation of a cascade of suicide proteins in the cell destined to die

9) Cell Signaling: Reception, Transduction, and Response

• Cells communicate using a signal transduction pathway

1. Reception- cell detection of signaling molecule– G protein-coupled receptor-attachment of ligand, GTP

replaces FDP, it activates an enzyme and the signal is sent

– Receptor tyrosine kinase- ligand binds, dimer formed and phosphorylated, activates relay proteins, cellular response sent

– Ligand-gated ion channel- ligand opens gate, ions come into cell, cellular response sent

2. Transduction- signal transduced through a pathway, with many forms, proteins, and includes phosphorylation cascades (which enzyme phosphotase removes) -second messengers help broadcast signals quickly

3) Response- pathways can activate transcription factors (regulate genes) or can regulate enzyme activity

-scaffolding proteins increase signal transduction efficiency

-unbinding of ligand turns off signal

10) Apoptosis

• Programmed cell death• Orderly and cause no damage to cells around

it• Signals can originate in or outside the cell• Occurs during embryonic development to

form fingers, toes, etc.

Cell Signaling

There are three steps to cell signaling: reception, transduction, and response. Reception is the target cell’s detection of a signaling molecule coming from outside the cell. A chemical signal is detected when the signaling molecule binds to a receptor protein located at the cell’s surface or inside the cell. Transduction begins when the binding of the signaling molecule changes the receptor protein. The transduction stage converts the signal to a form that can bring about a specific cellular response. During response the transduced signal finally triggers a specific cellular response. The response may be almost any imaginable cellular activity.

A G-protein-coupled receptor is a membrane receptor that works with the help of a G protein. The ligand or signaling molecule will bind to the G-protein-coupled receptor. This causes a change in the receptor so that it may now bind to an inactive F protein, causing a GTP to displace the GDP. This activates the F protein. The F protein binds to a specific enzyme and activates it. When the enzyme is activated, it can trigger the next step in a pathway leading to a cellular response. All the molecular shape changes are temporary.

Question 11

The three stages of cell signaling are reception, transduction, and response

a.Trueb.False

Question 12

Apoptosis is scheduled cell birtha.True b.False

Question 13

At each step in the signaling process, the signal is transduced

a.True b.False

Question 14

The activation of receptor tyrosine kinases is characterized by GTP hydrolysis

a.Trueb.False

Question 15

Apoptosis involves the activation of cellular enzymes

a.Trueb.False

*Word will be defined again in a later chapter**Word has been previously defined

Vocab• Cell division-the reproduction of cells• Cell cycle-an ordered sequence of events in the

life of a cell, from its origin in the division of a parent cell until its own division into two; the eukaryotic cell cycle is composed of interphase (including G1, S, and G2 subphases) and M phase (including mitosis and cytokinesis)

• Genome-the genetic material of an organism or virus; the complete complement of an organism’s or virus’s genes along with its noncoding nucleic acid sequences

• **Chromosome-a cellular structure carrying genetic material, found in the nucleus of eukaryotic cells; consists of one very long DNA molecule and associated proteins (A bacterial chromosome consists of a single circular DNA molecule and associated proteins and is found in the nucleoid region)

• *Somatic sells-any cell in a multicellular organism except a sperm or egg

• *Gametes-a haploid reproductive cell. Gametes unite during sexual reproduction to produce a diploid zygote

• **Chromatin- the complex of DNA and protein that makes up a eukaryotic chromosome (dispersed form, which occurs when the cell is not dividing, is a mass of very long, thin fibers that are not visible with a light microscope)

• Sister chromatid-either of two copies of a duplicated chromosome attached to each other by proteins at the centromere and, sometimes, along the arms (two joined sister chromatids make up a chromosome; chromatids are eventually separated during mitosis or meiosis II)

• Centromere-the specialized region of the chromosome where two sister chromatids are most closely attached

• Mitosis-a process of nuclear division in eukaryotic cells conventionally divided into five stages: prophase, prometaphase, metaphase, anaphase, and telophase. Mitosis conserves chromosome number by allocating replicated chromosomes equally to each of the daughter nuclei

• Cytokinesis-the division of the cytoplasm to form two separate daughter cells immediately after mitosis, meiosis I, or meiosis II

• *Meiosis- a modified type of cell division in sexually reproducing organisms consisting of two rounds of cell division but only one round of DNA replication: resulting in cells with half the number of chromosome sets as the original cell

• Mitotic (M) phase-the phase of the cell cycle that includes mitosis and cytokinesis

• Interphase-the period in the cell cycle when the cell is not dividing; the cellular metabolic activity is high, chromosomes and organelles are duplicated, and cell size may increase (accounts for 90% of the cell cycle)

• G1 phase-the first gap, or growth phase, of the cell cycle, consisting of the portion of interphase before DNA synthesis occurs

• S phase-the synthesis phase of the cell cycle; the portion of interphase during which DNA is replicated

• G2 phase-the second gap, or growth phase, of the cell cycle, consisting of the portion of interphase after DNA synthesis occurs

• Prophase-the first stage of mitosis, in which the chromatin condenses, the mitotic spindle begins to form, and the nucleolus disappears, but the nucleus remains intact

• Prometaphase-the second stage of mitosis, in which discrete chromosomes consisting of identical sister chromatids appear, the nuclear envelope fragments, and the spindle microtubules attach to the kinetochores of the chromosomes

• Metaphase-the third stage of mitosis, in which the spindle is complete and the chromosomes, attached to microtubules at their kinetochores, are all aligned at the metaphase plate

• Anaphase-the fourth stage of mitosis, in which the chromatids of each chromosome have separated and the daughter chromosomes are moving to the poles of the cell

• Telophase-the fifth and final stage of mitosis, in which daughter nuclei are forming and cytokinesis has typically begun

• Mitotic spindle-an assemblage of microtubules and associated proteins that is involved in the movements of chromosomes during mitosis

• **Centrosome- structure made of two centrioles present in the cytoplasm of animal cells, important during cell division; functions as a microtubule-organizing center

• Aster-a radial array of short microtubules that extends from each centrosome toward the plasma membrane in an animal cell undergoing mitosis

• Kinetochore-a structure of proteins attached to the centromere that links each sister chromatid to the mitotic spindle

• Metaphase plate-an imaginary plane midway between the two poles of a cell in metaphase on which the centromeres of all the duplicated chromosomes are located

• Cleavage-the process of cytokinesis in animal cells, characterized by pinching of the plasma membrane

• Cleavage furrow-the first sign of cleavage in an animal cell; a shallow groove in the cell surface near the old metaphase plate

• Cell plate-a double membrane across the midline of a dividing plant cell, between which the new cell wall forms during cytokinesis

• Binary fission-a method of asexual reproduction by “division in half.” In prokaryotes, binary fission does not involve mitosis; but in single-celled eukaryotes that undergo binary fission, mitosis is part of the process.

• Origin of replication-site where the replication of a DNA molecule begins, consisting of a specific sequence of nucleotides

• Cell cycle control system-a cyclically operating set of molecules in the eukaryotic cell both triggers and coordinates key events in the cell cycle

• Checkpoint-a control point in the cell cycle where stop and go-ahead signals can regulate the cycle

• G0 phase-a nondividing state occupied by cells that have left the cell cycle

• Cyclin-a cellular protein that occurs in a cyclically-fluctuating concentration and that plays an important role in regulating the cell cycle

• Cyclin-dependent kinase (Cdk)-a protein kinase that is active only when attached to a particular cyclin

• MPF (Maturation-promoting factor/M-phase-promoting factor)-a protein complex required for a cell to progress from late interphase to mitosis. The active form consists of cyclin and a protein kinase

• Growth factor-a protein released by certain cells that stimulates other cells to divide

• Density-dependent inhibition-the phenomenon observed in normal animal cells that causes them to stop dividing when they come into contact with one another

• Anchorage dependence-the requirement that a cell must be attached to a substratum in order to divide

• Transformation-the conversion of a normal animal cell to a cancerous cell

• Benign tumor-a mass of abnormal cells that remains at the site of its origin

• Malignant tumor-a cancerous tumor that is invasive enough to impair the functions of one or more organs

• Metastasis-the spread of cancer cells to locations distant from their original site 

11) Cell Cycle

1. Interphase contains G1, S, and G2, which takes up 90% of the cell cycle, cell grows and organelles and chromosomes duplicate.

2. Mitosis takes up the other 10%3. Cycle is controlled by checkpoints- cell either

receives the go-ahead or stop signal4. If stopped, cell goes into the G0 phase (non-

dividing state)5. Loss of cell cycle controls can lead to cancer

12) Mitosis Steps

1. Prophase-condensing of chromatin, nucleoli gone, sister chromatid cohesion, mitotic spindle form, centrosomes separate

2. Prometaphase- nuclear envelope fragments, chromosomes condensed, kinetochore microtubules formed

3. Metaphase- centrosomes at opposite poles, chromosomes line up at metaphase plate

4. Anaphase- daughter chromosomes separate and more to towards opposite ends of the cell.

5. Telophase/Cytokinesis- organelles and cytoplasm split, 2 cells form and split (genetically identical)

Interphase can be divided into sub-phases: the G1 phase, the S phase, and the G2 phase. In the G1 phase the cell grows while carrying out cell functions unique to its cell type. In the S phase the cell continues to carry out its unique functions and duplicates its chromosomes. This means it makes a copy of the DNA that makes up the cell’s chromosomes. The G2 phase is the gap after the chromosomes have been duplicated and just before mitosis. The cell prepares to divide. The circle graph also shows the M phase(usually the shortest part of the cycle and includes mitosis and cytokinesis). In the M phase, mitosis divides the nucleus and distributes its chromosomes to the daughter nuclei, and cytokinesis divides the cytoplasm, producing two daughter cells.

Interphase:1.A nuclear envelope bounds the nucleus.2.Two centrosomes have formed by replication of a single centrosome.Prophase:1.The chromatin becomes more tightly coiled into discrete chromosomes.2.The nucleoli disappear.3.The mitotic spindle begins to form in the cytoplasm. Metaphase:1.The microtubules move the chromosomes to the metaphase plate at the equator of the cell. 2.The centrioles have migrated to opposite poles in the cell.Anaphase:1.Sister chromatids begin to separate, pulled apart by motor molecules interacting with kinetochore microtubules.2.The cell elongates with the help of motor molecules.3.The opposite ends of the cell both contain complete and equal sets of chromosomes.Telophase:1.The nuclear envelope re-form around the sets of chromosomes located at opposite ends of the cell.2.The chromatin fiver of the chromosomes becomes less condensed.3.Cytokinesis begins, during which the cytoplasm of the cell is divided. In animal cells, a cleavage furrow forms that divides the cytoplasm; in plant cells, a cell plate forms that divides the cytoplasm.

Question 16

The cell is most likely ina.G1b.G2c. Anaphased.Prophase

Question 17

Which of the following doesn’t occur during mitosis

a.Replication of DNAb.Spindle formationc. Separation of sister chromatidsd.Formation of spindle poles

Question 18

How many different phases can a cell be ina.3b.8c. 6d.10

Question 19

Cell division results in genetically identical daughter cells

a.Trueb.False

Question 20

The mitotic phase does not alternate with interphase in the cell cycle

a.Trueb.False

**Word has been previously defined

Vocab• Heredity-the transmission of traits from one generation

to the next• Variation-differences between members of the same

species• Genetics-the scientific study of heredity and hereditary

variation• Gene-a discrete unit of hereditary information

consisting of a specific nucleotide sequence in DNA (or RNA, in some viruses)

• **Gametes- a haploid reproductive cell. Gametes unite during sexual reproduction to produce a diploid zygote

• Locus-a specific place along the length of a chromosome where a given gene is located

• Asexual reproduction-the generation of offspring from a single parent that occurs without the fusion of gametes (by budding, division of a single cell, or division of the entire organism into two or more parts). In most cases, the offspring are genetically identical to the parent

• Clone-a lineage of genetically identical individuals or cells

• Sexual reproduction-a type of reproduction in which two parents give rise to offspring that have unique combinations of genes inherited from the gametes of the parents

• Life cycle-the generation-to-generation sequence of stages in the reproductive history of an organism

• **Somatic cell- any cell in a multicellular organism except a sperm or egg

• Karyotype-a display of the chromosome pairs of a cell arranged by size and shape

• Homologous chromosomes (homologs/homologous pair)-a pair of chromosomes of the same length, centromere position, and staining pattern that possess genes for the same characteristic at corresponding loci. One homologous chromosome is inherited from the father and the other from the mother.

• Sex chromosomes-chromosomes responsible for determining the sex of an individual

• Autosomes-a chromosome that is not directly involved in determining sex; not a sex chromosome

• Diploid cell-a cell containing two sets of chromosomes (2n), one set inherited from each parent

• Haploid cells-a cell containing only one set of chromosomes (n)

• Fertilization-the union of haploid gametes to produce a diploid zygote

• Zygote-the diploid product of the union of the haploid gametes during fertilization; a fertilized egg

• **Meiosis-a modified type of cell division in sexually reproducing organisms consisting of two rounds of cell division but only one round of DNA replication: resulting in cells with half the number of chromosome sets as the original cell

• Alternation of generations-a life cycle in which there is both a multicellular diploid form, the sporophyte, and a multicellular haploid form, the gametophyte; characteristic of plants and some algae

• Sporophyte-in organisms (plants and some algae) that have alternation of generations, the multicellular diploid form that results from the union of gametes.

• Spore-in the cell cycle of a plant or alga undergoing alternation of generations, a haploid cell produced in the sporophyte by meiosis.

• Gametophyte-in organisms (plants and some algae) that have alternation of generations, the multicellular haploid form that produces haploid gametes by mitosis.

• Meiosis I-the first division of a two-stage process of cell division in sexually reproducing organisms that results in cells with half the number of chromosome sets as the original cell

• Meiosis II- the second division of a two-stage process of cell division in sexually reproducing organisms that results in cells with half the number of chromosome sets as the original cell

• Synapsis-the pairing and physical connection of replicated homologous chromosomes during prophase I of meiosis

• Crossing over-the reciprocal exchange of genetic material between nonsister chromatids during prophase I of meiosis

• Chiasma-the X-shaped, microscopically visible region where homologous nonsister chromatids have exchanged genetic material through crossing over during meiosis, the two homologs remaining associated due to sister chromatid cohesion

• Recombinant chromosome-a chromosome created when crossing over combines the DNA from two parents into a single chromosome

13) Chromosomal Information

• Maternal and paternal DNA involved in meiosis• Homologous chromosomes- mom and dad set of the

same chromosome• Meiosis forms gametes/sex cells (haploid) whereas

mitosis forms somatic cells (diploid)• Synapsis-connection between homologous

chromosomes• Crossing over- genetic rearrangement between

nonsister chromatids • Chiasma- physical manifestation of crossing over

14) Meiosis Steps

1. Prophase I- crossing over occurs, chromosomes separate2. Metaphase I- homologous chromosomes line up at

metaphase plate3. Anaphase I- homologous chromosomes separate (now sister

chromatids)4. Telophase I/Cytokinesis- cell splits5. Prophase II- Mitotic Spindle forms6. Metaphase II- sister chromatids line up at metaphase plate7. Anaphase II- sister chromatids separate8. Telophase II/Cytokinesis- 4 haploid genetically different cells

form

Genetic Variation

• Caused by 3 things: 1. Independent assortment- each homologous pair

is positioned independently of the others2. Crossing Over- switching of genes on a

chromosome between maternal and paternal chromosomes causes the daughter chromosome to be genetically individual

3. Random Fertilization- the egg fertilized by the sperm is entirely random

Interphase: Each of the chromosomes makes a copy of itself. The centrosome divides. Prophase I: The chromosomes condense, resulting in two sister chromatids attached at their centromeres. Synapsis and crossing over occurs. Crossing over is when the DNA from one homologue is cut and exchanged with an exact portion of DNA from the other homologue. After crossing over, the centrioles move away from each other, the nuclear envelope disintegrates, and spindle microtubules attach to the kinetochores forming on the chromosomes that begin to move to the to the metaphase plate of the cell.Metaphase I: The homologous pairs of chromosomes are lined up at the metaphase plate, and microtubules from each pole attach to each member of the homologous pairs in preparation for pulling them to opposite ends of the cell. Anaphase I: The spindle apparatus helps to move the chromosomes toward opposite ends of the cell; sister chromatids stay connected and move together toward the poles.Telophase I: The homologous chromosomes move until they reach the opposite poles. Cytokinesis occurs during telophase. A cleavage furrow occurs in animal cells and cell plates occur in plant cells. This produces two haploid cells.

Prophase II: A spindle apparatus forms, and sister chromatids move toward the metaphase plate. Metaphase II: The chromosomes are lined p on the metaphase plate, and the kinetochores of each sister chromatid prepare to move to the opposite poles.Anaphase II: The centromeres of the sister chromatids separate, and individual chromosomes move to opposite ends of the cell.Telophase II and Cytokinesis: The chromatids have moved all the way to opposite ends of the cell, nuclei reappear, and cytokinesis occurs. Each of the four daughter cells has the haploid number of chromosomes and is genetically different from the other daughter cells and from the parent cell.

Question 21

A haploid and diploid cell have a combined ____ chromosomes

a.12b.69c. 22d.68

Question 22

At which phase of meiosis II does the separation of sister chromatids occur?

a.Metaphase IIb.Anaphase Ic. Prophase IId.Anaphase II

Question 23

What life cycle stage is found in plants but not animals?

a.Gameteb.Multicellular haploidc. zygotes d.unicellular diploid

Question 24

Reproductive gametes are called somatic cells.a.Trueb.False

Question 25

A human cell containing 22 autosomes and a Y chromosome is a ____.

a.somatic cell of a femaleb.somatic cell of a malec. a spermd.an egg

Lab 1: Osmosis and Diffusion

Overview: This lab was used to investigate the processes of diffusion and osmosis in a model membrane system. It was also used to discuss water potential in relation to living plant tissues.

Objectives: After doing this lab, you should be able to:

   Measure the water potential of a solution in a controlled experimentDetermine the osmotic concentration of living tissue or an unknown solution from experimental dataDescribe the effects of water gain or loss in plant and animal cellsRelate osmotic potential to solute concentration and water potential

Lab 3:Mitosis and Meiosis

• Lab 3 was used to further our understanding of mitosis, meiosis, and the cell cycle. We looked at onion root tip cells and counted the number of cells at each phase to determine how much time each phase takes in the cell cycle. We found that interphase takes up the most time while mitosis and meiosis take up much less.

Free Response # 1

A) Explain the process of mitosis.B) Explain the process of meiosis. C) Contrast mitosis and meiosis. You may compose a diagram/chart.

All cells come from other cells. New cells are formed from cell division which involves the division of the nucleus and the cytoplasm. There are two main types of nuclear division: mitosis and meiosis. The processes of these are alike yet differ.

Example Answer Part AThere are five phases in mitosis: prophase, prometaphase,

metaphase, anaphase, and telophase. In prophase the chromatin becomes more tightly coiled into discrete chromosomes. The nucleoli disappear and the mitotic spindle begins to form in the cytoplasm. In prometaphase the nuclear envelope begins to fragment, allowing the microtubules to attach to the chromosomes. The two chromatids of each chromosome are held together by protein kinetochores in the centromere region. The microtubules will attach to the kinetochores. In metaphase the microtubules move the chromosomes to the metaphase plate at the equator of the cell. The centrioles have migrated to opposite poles in the cell, riding along the developing spindle. In anaphase the sister chromatids being to separate, pulled apart by motor molecules interacting with kinetochore microtubules. The cell elongates with the help of motor molecules. In telophase the nuclear envelopes re-form around the sets of chromosomes located at opposite ends of the cell. The chromatin fiver of the chromosomes becomes less condensed. Cytokinesis beings and the cytoplasm of the cell is divided. In animal cells, a cleavage furrow forms and in plant cells, a cell plate forms that divides the cytoplasm.

Example Answer Part B

The process of meiosis follows the same basic stages as mitosis except meiosis repeats the stages. The first stage of meiosis is prophase I. Just as in mitosis, the chromosomes condense, centrosomes move, the nuclear envelope breaks down, and spindles form. However, events called synapsis and crossing over occur that are unique to meiosis. Chromosomes become attached in synapsis and exchange segments during crossing over. The homologs are held together by chiasmata—the result of crossing over—and sister chromatid cohesion.

During metaphase I, homologs arrange on the metaphase plate, just as in mitosis. A kinetochore microtubule is attached to each pair of chromatids. The homologs are then pulled apart to opposite poles by the microtubules during anaphase I. Unlike mitosis, the chromatids stay attached during separation.

The first set of stages is brought to an end by telophase I and cytokinesis. The cell splits into two haploid cells with replicated chromosomes. Since the chromosomes are replicated, there is no need for duplication during prophase II. Just the spindle apparatus forms during prophase II.

The chromosomes position themselves on the metaphase plate in metaphase II. Microtubules extending from opposite poles attach themselves to the kinetochores of sister chromatids. In anaphase II, the chromatids are separated and moved toward opposite poles by the microtubules. The process of meiosis ends completely by the formation of four distinct, haploid daughter cells. This, along with the formation of the nuclei and the decondensation of chromosomes, occurs in telophase II and cytokinesis, the final stages of meiosis.

Example Answer Part C

MITOSIS•One division•Two daughter cells (diploid)•Produces somatic cells•Genetically identical to the parent cell

MEIOSIS•Two divisions•Four daughter cells (haploid) •Produces gametes•Reduces number of chromosomes by half•Synapsis of homologs and crossing over between non-sister chromatids during prophase I•Chiasmata

Free Response # 2

A) Define osmosis.B) Define diffusion.C) Compare/contrast the two.D) Explain hypotonic, hypertonic, and isotonic

solutions using: osmosis/diffusion, semi-permeable membrane, flaccid, turgid, plasmolysis, and lysed.

Example Answer Part A, B, and C

A) Osmosis is the moving of water through a semi-permeable membrane down its concentration gradient (against the solute concentration gradient)B) Diffusion is the movement of a solvent down its concentration gradient (high concentration to low concentration) through a semi-permeable membrane. C) Osmosis is the movement of water while diffusion usually refers to movement of a solute. They both have to do with movement down a concentration gradient.

Example Answer Part D

D) When a cell is put in a hypotonic solution, there is less solute on the outside than the inside, so water moves into the cell through the semi-permeable membrane by osmosis. This makes plant cells turgid and animal cells swell and they can even lyse (break). When a cell is put into a hypertonic solution, more solute is outside the cell, so water moves out of the cell (osmosis). Because of this, animal cells shrivel and plant cells are plasmolyzed (cell does not touch walls). In an isotonic solution, no osmosis occurs because the concentration is equal. Animal cells stay the same while plant cells become flaccid (or limp).