cells all organisms are made up of cells the cell is the unit of structure and function of all...
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CELLS
• All organisms are made up of cells
• The cell is the unit of structure and function of all living things
• Life arises from the interaction of all cellular components.
There is correlation between the structure of cells and their function
Ex: The shapes of muscles cells, sperm cells, red blood cells,, nerve cells are appropriate for their function.
Example: the flat tile like epithelial cells of the skin fit closely together making a barrier to bacterial entrance, water loss etc.
Another way to say this is that
“shape reflects function”
How small are cells?
Most cells are microscopic– Cells vary in size and shape
Human height
Length of somenerve andmuscle cells
Chicken egg
Frog egg
Un
aid
ed e
ye
Lig
ht m
icro
sco
pe
Ele
ctro
n m
icro
scop
e
10 m
1 m
100 mm(10 cm)
10 mm(1 cm)
1 mm
100 m
10 m
1 m
100 nm
10 nm
1 nm
0.1 nmAtoms
Proteins
Small molecules
Lipids
Viruses
Ribosome
Nucleus
Mycoplasmas(smallest bacteria)
Most plant andanimal cells
Most bacteria
Mitochondrion
History• Robert Hook (1665) named “cells” after observing tiny
compartments in cork .• Anton VanLeeuwenhoek (1600’s) improved the
primitive microscopes and observed one celled organisms, even bacteria. He documented his findings with letters and diagrams to the Royal Society (of Science) in London.
• Robert Brown (1600’s)discovered the nucleus• Electron microscope was developed in the late 1930’s
and allows scientist to see up to 0.5 nanometers. About 1000 times larger than regular microscopes.
How are cells studied?
Microscopes and Biochemistry– The light microscope (LM) magnify cells up to 1000 times
• Enables us to see the overall shape and structure of a cell
Eyepiece
Ocularlens
Objective lens
Specimen
Condenserlens
Lightsource
Figure 4.1A
– The electron microscope• Allows greater magnification and reveals cellular
details
SE
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Figure 4.1C Figure 4.1D
The cell theory (mid-1800’s)
• Mathew Schleiden and Theodor Schwann examined plant and animal tissues and came to the conclusion that they both consist of cells
• Rudolph Virchow came to the conclusion that young cells come from the division of other cells
• 1. All organisms are made up of cells• 2. Cells are the units of structure and function of all
living things, that is cells have all the properties of life.• 3. All cells come from pre-existing cells
• Prokaryotic cells are structurally simpler than • eukar yotic cells
– There are two kinds of cells• Prokaryotic- No nucleus- Bacteria and Archeae• Eukaryotic- have nucleus- plants, animals and fungi
Prokaryotic cell
Nucleoidregion
Nucleus
Eukar yotic cell Organelles
Co
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00
Figure 4.3A
– TYPE OF CELLS: Prokaryotic and Eukaryotic
– Prokaryotic cells are small, relatively simple cells • That do not have a membrane-bound nucleus
Prokar yoticflagella
Ribosomes
Capsule
Cell wallPlasmamembrane
Nucleoid region (DNA)
Pili
Eukaryotic cells have a nucleus and are
par titioned into functional compar tments.– All other forms of life( plants and animals) are
composed of complex eukaryotic cells– Membranes form compartments inside
eukaryotic cells to facilitate metabolic activities
– A small cell has a greater ratio of sur face area to volume
• Than a large cell of the same shape
30 m 10 m
30 m 10 m
Surface areaof one large cube 5,400 m2
Total surface areaof 27 small cubes 16,200 m2
– A typical animal cell• Contains a variety of membranous organelles
NucleusSmooth endoplasmicreticulum
Roughendoplasmicreticulum
Ribosomes
Golgiapparatus
Plasma membrane
Mitochondrion
Flagellum
Not in mostplant cells Lysosome
Centriole
Microtubule
CytoskeletonIntermediatefilament
Microfilament
Peroxisome
THE CYTOSKELETON AND RELATED STRUCTURES
The cell’s internal skeleton helps organize its structure and activities– A network of protein fibers
• Make up the cytoskeleton.
Actin subunit
Microfilament
7 nm
Fibrous subunits
10 nm
Intermediate filament Microtubule
25 nm
Tubulin subunit
Functions of the cytoskeleton
– Tubules and filaments are made up of protein fibers
– Microfilaments of actin • Enable cells to change shape and move
– Intermediate filaments • Reinforce the cell and anchor organelles
– Microtubules give the cell rigidity• provide anchors for organelles and act as tracks for
organelle movement
Over view: Many cell organelles are connected through the endomembrane system
– All cells on earth are enclosed in membranes that maintain internal conditions different from the surroundings, have DNA as their genetic material and can convert forms of energy from one to another.
– Membranes form the boundaries of many eukar yotic cells
• Compartmentalizing the interior of the cell and facilitating a variety of metabolic activities
– The nucleus is the cellular control center• Containing the cell’s DNA, which directs cellular
activities NucleusChromatin
Nucleolus
Pore
Ribosomes
Roughendoplasmicreticulum
Two membranesof nuclearenvelope
Figure 4.5
ORGANELLES OF THE ENDOMEMBRANE SYSTEM
The nucleus is the cell’s genetic control center– The largest organelle is usually the nucleus
• Which is separated from the cytoplasm by the nuclear envelope
Inside the nucleus• Chromatin fibers made up of DNA
These thin fibers coil up during cell division becoming thicker and visible. They are called now a chromosome
Nucleolus makes ribosomes
– Ribosomes on the sur face of the rough ER• Produce proteins that are secreted,
inser ted into membranes, or transpor ted in vesicles to other organelles
Secretory(glyco-) proteininside trans-port vesicle
4Transport vesiclebuds off
Sugar chain
3
Rough ER
Glycoprotein2Polypeptide
Ribosome
1
The endomembrane system is a collection of membranous organelles
• That manufactures and distributes cell products\
Smooth endoplasmic reticulum has a variety of functions – Smooth endoplasmic reticulum, or smooth ER
• Synthesizes lipids
• Processes toxins and drugs in liver cells
• Stores and releases calcium ions in muscle cells
Smooth ER
Rough ER
Nuclearenvelope
Rough ERRibosomes
Smooth ER
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– A typical animal cell• Contains a variety of membranous organelles
NucleusSmooth endoplasmicreticulum
Roughendoplasmicreticulum
Ribosomes
Golgiapparatus
Plasma membrane
Mitochondrion
Flagellum
Not in mostplant cells Lysosome
Centriole
Microtubule
CytoskeletonIntermediatefilament
Microfilament
Peroxisome
The Golgi apparatus finishes, sorts, and ships cell products– Stacks of membranous sacs receive and modify ER
products• Then ship them to other organelles or the cell sur face
Figure 4.9
Golgi apparatus
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Transportvesicle fromthe Golgi“Shipping” side
of Golgi apparatus
Golgiapparatus
“Receiving” side ofGolgi apparatus
Transportvesiclefrom ER
New vesicleforming
The endomembrane system– The various organelles of the endomembrane system
• Are interconnected structurally and functionally
Nucleus
Smooth ER Nuclear envelope Golgi apparatus
Lysosome
Vacuole
Plasmamembrane
Rough ERTransport vesiclefrom ER to Golgi
Transport vesicle fromGolgi to plasma membrane
Mitochondria gets chemical energy from food– Mitochondria carry out cellular respiration
It uses the chemical energy in food to make ATP for cellular work
Mitochondrion
Outermembrane
Intermembranespace
Matrix
Innermembrane
Cristae
TE
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80
Lysosomes are digestive compar tments within a cell– Lysosomes are sacs of enzymes that function in
digestion within a cell
Golgiapparatus
Plasmamembrane
“Food”
Foodvacuole
Lysosomes
2Lysosomeengulfingdamagedorganelle
5
Digestion4
3
Engulfmentof particle
Transport vesicle(containing inactivehydrolytic enzymes)
1
Rough ER
– Lysosomes in white blood cells• Destroy bacteria that have been ingested
• lysosomes also help to digest worn out , damaged cell parts, recycle materials within the cell and fuse with food vacuoles to digest nutrients.
Figure 4.10B
Lysosome
Nucleus
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Lysosomes in white blood cells destroy bacteria and lysosomes also can digest other parts of the
cell
Abnormal lysosomes can cause fatal diseases– Lysosomal storage diseases. These are rare.
• Inter fere with various cellular functions
• Ex: Tay- Sachs, does not break down lipids in nerve cell membranes. Lipids accumulate
• Pompe’s disease, lysosomes cannot digest glycogen and it accumulates in muscle and liver cells
Peroxisomes• Specialized vesicles that contains enzymes
(catalase) that digest hydrogen peroxide H2O2
• Our cells produce hydrogen peroxide during metabolism and the enzymes in peroxisomes break it down into water and oxygen gas which are harmless to the cell.
Plant Cells
• Three organelles animals do not have
Chloroplasts
Cell wall
Central vacuole
– A typical plant cell has some structures that an animal cell lacks
• Such as chloroplasts and a rigid cell wall
CentralvacuoleNot in
animalcells
Chloroplast
Cell wall
Golgiapparatus
Nucleus
Microtubule
CytoskeletonIntermediatefilament
Microfilament
Ribosomes
Smoothendoplasmicreticulum
Mitochondrion
Peroxisome
Plasma membrane
Roughendoplasmicreticulum
ENERGY-CONVERTING ORGANELLES
Chloroplasts conver t solar energy to chemical energy. This is where PHOTOSYNTHESIS takes place– Chloroplasts, found in plants and some protists
Conver t solar energy to chemical energy in sugars
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Chloroplast
Stroma
Intermembranespace
Inner and outermembranes
Granum
Vacuoles function in the general maintenance of the cell– Plant cells contain a large central vacuole,
• Which has lysosomal and storage functions
Chloroplast
Centralvacuole
Nucleus
Col
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ed T
EM
8,7
00
Central vacuoles in plants
Also help increase the size of cells by absorbing water
Are mostly water, minerals and nutrients
• Store color pigments (that attract insects)
• Store waste products and poisons
– Some protists have contractile vacuoles • That pump out excess water
LM
65
0
Nucleus
Contractilevacuoles
Organelles• NAME LOCATION FUNCTION
• Cytoskeleton cytoplasm Maintains cell shape
facilitates movement and move
materials within the cell
• Cytosol cytoplasm Protein rich fluid in which
organelles and cytoskeleton
are immersed
• Nucleus Inside nuclear envelope Site of most of cell’s DNA
and nucleolus
• Nucleolus Inside the nucleus Synthesis of ribosomal RNA
ORGANELLES
NAME LOCATION FUNCTION
• Rough Endoplasmic Reticulum cytoplasm Protein synthesis,Cell metabolism,
• Smooth Endoplasmic Reticulum cytoplasm Lipid synthesis, storage of calcium, Detoxification of toxic substances
• Ribosomes Rough ER and Protein synthesis free in the cytoplasm
• Vesicles move through cytoplasm Transport
• Golgi Bodies cytoplasm Processing, sorting, shipping of proteins and lipids
• Mitochondria cytoplasm Gets energy from food (makes ATP during aerobic respiration)
ORGANELLES
NAME LOCATION FUNCTION
• Lysosomes cytoplasm Digestion and breaking down of materials
(only in animal cells) ( including the cell’s own)
• Peroxisomes cytoplasm Sacs of enzymes that break down substances
(alcohol, amino acids) into hydrogen peroxide
and then the hydrogen peroxide into water
and oxygen.
• Plasma Membrane all around the cell Controls substances and signals that go in
and out of cells. Maintains shape and
volume
• Cell wall ( plant cells) cytoplasm Keeps water inside and limits water
uptake, protects from outside influences,
maintains shape.
ORGANELLES
NAME LOCATION FUNCTION
• Central vacuoles center of plant cell water maintenance, stores waste
(plant cells only)
• Plastids cytoplasm plastids provide nutrients and
(plant cells only) pigmentation
• Chloroplast many throughout carry out photosynthesis
(plant cells only) the cytoplasm contain chlorophyll
CELL JUNCTIONS
• What are junctions? Protein or cytoplasmic bridges that serve as physical links between cells.
• The junctions between cells help integrate cells into tissues and higher levels of functioning. Junctions make cells living units greater than each individual part.
• Junctions serve to send and receive signals and materials and to cement itself to other cells and junctions coordinate cell activities.
Plant cellsPlants are covered by cell walls composed of
cellulose fibers.
Cell walls have plasmodesmata, these are channels that pass through adjoining cell walls connecting plant cell to plant cell.
Animal cells:Junctions
• There are different kinds of intracellular junctions between animal cells, integrating each cell into a greater unit.
• Tight junctions
• Desmosomes or Anchoring juctions:
• Gap or Communication junctions:
Tight junctions
They fuse cell to cell to prevent leakage. Ex: cells of the lining of the intestines keeping the fluid inside. All cells of most tissues are joined this way. The skin and the lining of internal cavities (epithelial).
Gap or Communication junctions:
Link the cytoplasm of neighboring cells. They are open channels that allow a flow of materials and signals between cells.
• Very common in embryos and in heart tissue to allow for the passage of ions to cause contraction
Desmosomes or Anchoring juctions:
Joins cells in tissues of the skin, heart and other organs such as the bladder subject to stretching.
– Tight junctions can bind cells together into leakproof sheets
– Anchoring junctions link animal cells into strong tissues
– Gap junctions allow substances to flow from cell to cell
Anchoring junction
Tight junctions
Gap junctions
Extracellular matrix
Space between cells
Plasma membranes of adjacent cellsFigure 4.18B
Cilia and flagella• move when microtubules bend
– Eukaryotic cilia and flagella are locomotor appendages that protrude from some cells
LM
60
0
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0
Figure 4.17A Figure 4.17B
Clusters of microtubules Drive the whipping action of these organelles
. FlagellumElectron micrographsof cross sections:
Flagellum
Basal body
Basal body(structurally identical to centriole)
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00
Plasmamembrane
Dynein arms
Radial spoke
Centralmicrotubules
Outer microtubuledoublet
PLASMA MEMBRANE• Function:
The cell’s “gate keeper”. Very important.
It controls what goes in and out of a cell.
Keeps equilibrium between the inside of cells and the outside and promotes homeostasis.
Web site to check:http://www.wisc-online.com/objects/index_tj.asp?objid=AP1101
• Function:
The cell’s “gate keeper”. Very important.
It controls what goes in and out of a cell.
Keeps equilibrium between the inside of cells and the outside and promotes homeostasis.
Web site to check:http://www.wisc-online.com/objects/index_tj.asp?objid=AP1101
Membranes
• http://www.wiley.com/legacy/college/boyer/0470003790/animations/membrane_transport/membrane_transport.htm
The plasma membrane of the cell is selectively permeable
Controlling the flow of substances into or out of the cell
Cytoplasm
Outside of cell
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PLASMA MEMBRANE
STRUCTURE:
It is a LIPID BILAYER. Its main component is a PHOSPHOLIPID molecule.
• A phospholipid is made up of a hydrophilic head (water loving) and two hydrophobic fatty acid tails (dislike water). These are arranged in two layers with the fatty acids tails sandwiched between the hydrophilic heads.
• The membrane is “fluid”, it moves about, tails twist and wave
• Embedded in the phospholipid bilayer are the surface proteins.
• The membrane is “a mosaic” of different proteins embedded in the fluid matrix of the lipid bilayer.
What makes up the plasma membrane?
– Phospholipids are the main structural components of membranes
Membrane phospholipids form a bilayer• Have a hydrophilic head
and two hydrophobic tails
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH3
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CHCH
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH3
CH2
CH2
CH3
CH3
CH3N+
OO O–P
OCH2
CHCH2
C O C OO O
Phosphategroup
Symbol
Hydrophilic head
Hydrophobic tails
Phospholipids form a two-layer sheetCalled a phospholipid bilayer, with the heads facing outward and the tails facing
inward
Water
Water
Hydrophilicheads
Hydrophobictails
How does it work?• Membrane is selectively permeable or semi-
permeable. Small molecules that are electrically neutral diffuse easily in and out such as O2, CO2, and alcohols.
• The non-polar phospholipid tails of the bilayer repel charged molecules but allow lipid soluble molecules to pass easily.
• Sugars need to be transported through a channel as well as charged ions such as H+, Na+, K+, Cl
• Large molecules (like proteins) cannot diffuse through and must enter the cell by other mechanisms such as active transport. Active transport uses energy (ATP) to “push” the molecules in and out.
• Serious diseases associated with cell membrane defects:Multiple Sclerosis, there is a myelin cover on axons of nerve
cells. Because it is defective muscle control is lostCystic Fibrosis, The channels for chloride to pass through the
membrane do not work. Chloride ion are not able to leave the cell. Results in thick mucus in respiratory track and other ducts in the body.
Proteins found in the plasma membrane:
• Integral penetrate the hydrophobic core of the lipid bilayer
• Peripheral are loosely bound to the surface of the membrane
• Transport proteins
• Receptor proteins
• Recognition proteins
• Adhesion proteins
Proteins found in the plasma membrane:
• Transport proteins: These are open on both sides making a channel, a passage. Water soluble
substances pass through it. It is very specific for the substance that it moves.
• Receptor proteins: Grab or bind substances to pass them through. Have a binding site with a
specific shape that fits the shape of another molecule. It can bind a chemical messenger such as a hormone which then causes a change in the shape of the protein that relays the message to the inside of the cell.
• Recognition proteins: These are glycoproteins. Have a short chain of sugars attached to it. Are like fingerprints. Serve as identification tags that are recognized by other
cells. Your cells recognize “your own”
• Adhesion proteins: Like “glue”, make cells stick together.
The membrane is a fluid mosaic of phospholipids with proteins and other molecules embedded in a
phospholipid bilayer
Fibers of the extracellular matrix
Carbohydrate(of glycoprotein)
Glycoprotein
Microfilamentsof cytoskeleton
Phospholipid
CholesterolProteins
Plasmamembrane
Glycolipid
Cytoplasm
Membrane proteins also function in transportMoving substances across the membrane
ATP
Other membrane proteinsFunction as receptors for chemical
messages from other cells
Messenger molecule
Receptor
Activatedmolecule
Many membrane proteins Function as enzymes
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