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Cell Structures

4/6/09

Cell Biology 1 Cell Structures

A. Cell TheoryCell theory refers to the idea that cells are the basic unit ofstructure of all living things. Development of this theoryduring the 1800's was made possible by advances inmicroscopy. This theory is one of the fundamentalfoundations of biology. The theory says that new cells areformed from other existing cells and the cell is afundamental unit of structure, physiology, and organizationin all living organisms.

Source: http://en.wikipedia.org/wiki/Cell_theory

Basic Tenets1. The cell is the unit of structure and the unit of

function of most living things.- Prokaryoteand Eukaryote

- Endosymbiosis

2. Life is Unicellular (and colonial) orMulticellular 3. Cells arise from pre-existing cells by reproduction.- i.e., Mitosis (Binary fission) and Meiosis

Additionally:- Cells tend to be small .

- !of the Surface Area2 = Volume3 Rule-as you increase the size of a cell, the volume (V)

increases at a proportionally greater rate thanthe surface area (S)

- therefore making it increasing more difficult forthe cell to feed and respire, as its mouthgrows increasingly smaller relative to itsstomach

Notes

(1mm) (2 mm) (4 mm) (8 mm)Surface Area (6 x s

2) 6 mm

224 mm

296 mm

2384 mm

2

Volume (v3) 1 mm

38 mm

364 mm

3512 mm

3

Ratio 6:1 3:1 1.5:1 0.75:1

- Basic Structure- The basic eukaryotic cell contains the following:

Diagram: Review text fordiagrams of animal and plantcells, as well as prokaryotic cell

Reading: Cell Theory7th chp 38

thchp 3

9th chp 3

Basic Tenets of Cell theory:

1. Cells are the basic units ofstructure and function in anorganism.

2. All living things arecomposed of one or morecells (assuming viruses are

not alive).

3. Cells come only from thereproduction of existingcells (since the origin of

life).

Cell Structures


Cell (plasma) membrane - is composed of alipid bilayersurrounding the cell.Proteins areinterspersed in this layer, with carbohydrates on

the surface. The layer is semi-permeable; it ispermeable to water but not to solutes.

Nucleus - is bound by its own doublemembrane, within which the chromatin /chromosomes (DNA) are located.

Cytoplasm (Cytosol) - is all thefluidmaterialin a cell located between the nuclear membraneand the plasma membrane and incorporates the

! Cytoskeleton composed ofmicrofilamentsand microtubules thatanchor organelles, give shape, andallow motion

! Organelles subcellular, mostlymembrane bound, functional units of

the cell

B. Cell Structures

Label all diagrams for review alwaysand dont forget theimage catalogues.

Need some help wi th this one? Tr ythe cell diagram on the last page.

Answers:

1. Nucleolus2. Nucleus3. Ribosome4. Vesicle5. Rough endoplasmic

reticulum6. Golgi apparatus (or "Golgi

body")7. Cytoskeleton8. Smooth endoplasmic

reticulum

9.

Mitochondrion10. Vacuole11. Cytoplasm12. Lysosome13. Centriole (not examinable)14. Cell membrane (add this one

on yourself)


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Cell Structures


- Subcellular, functional units of the cell,- primarily membrane bound

1. Cellular Information

a. The Nucleus- plays a central role in cell reproduction,- directs metabolic activities of the cell- emanates "instructions" that guide the cell's life

processes- large double membrane-bounded organelle

containing the DNA (in the form of chromatin /chromosomes)

b. Chromatin- elongate threads of genetic material that fill the

eukaryotic nucleus- composed primarily of DNA and protein (mainly

histones), and RNA- during cell division it coils and folds to form the

chromosomes

Chromosomes

- are rod-like bodies visible only when the cell isundergoing division

- meiosis = germ cells;- mitosis = somatic cells

- primarily composed of DNA in a double helixform that comprisegenes

- Genes (the units of heredity)- A sequence of DNA that represents a

fundamental unit of heredity- that generally encodes for the synthesis

of a protein, that affects some trait, suchas eye colour

Cell Structures


Source: http://www.accessexcellence.org/AB/GG/

c. Nucleoid- a region, not bounded by a membrane, where the

chromosome is located in a prokaryotic cell

d. Nucleoli (singular, nucleolus)- non-membrane bound structure found in most nuclei

in which ribosomes are synthesized and partiallyassembled- composed of DNA, RNA, and proteins- site of rRNA transcription

e. Nuclear membrane- a

double membrane, inner and outer lipid bilayers

- surrounding the nucleus permits maintenance withinthe nucleus of an environment different from that inthe surrounding cytoplasm

2. Energy-based

" Life is characterized by the ability to assimilate, convert,and utilize energy. Energy is changed from one form toanother via chemical reactions in the mitochondria and


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Cell Structures


chloroplasts ."

a. Photosynthesis-

process by which light energy is converted to andstored as chemical energy glucose

- Chloroplast- energy converting organelle- plants

H2O + CO2light" C6H12O6 + O2 + H2O

Source: Biology 8th

ed., Campbell

b. Cellular Respiration- process by which energy stored (glucose) is

extracted and converted to ATP (energy currency).

O2 + H2O + glucose " ATP + CO2 + H2O

- Mitochondria"While respiration takes place outside themitochondria, it is in these cells that the majorenergy transfer occurs."

- energy converting organelle- the "power plants" of both plant and animal cells- responsible for providing energy from the

metabolic fuel (e.g., glucose)- found in all eukaryotic cells, but may later be lost.

350 ml of water are producedeach day by CellularRespiration.

Caveat: This is a major topic inBiology 11, it is expectedstudents are already familiarwith the steps in photosynthesis

(light and light-independentreactions) and cell respirations(glycolysis, citiric acid / krebs

cycle, electron transport /

respiratory chain)it isrecommended you review thesetopics.

Cell Respiration: Where?

1. Glycolysis

- cytoplasm

2.Krebs (Citric Acid) Cycle - matrix

3.Electron Transpor t Chain-

cristae

Cell Structures


- consists of a smooth outer membrane, separatedby a space from the inner.- inner membrane is folded to form cristae,

which increase the organelle's surface area forElelctron transport chain- surrounding the matrix (Krebs Cycle)

A bit more on ATP- cells focus all their energy resources on making the

nucleotideATP (adenosine triphosphate)

ATP + H2OEnzyme! ADP + Phosphate + Energy

Visit Wikipedia for more background info:

- http://en.wikipedia.org/wiki/Adenosine_triphosphate

- http://en.wikipedia.org/wiki/Nucleotide

Vocabulary Foreshadowing:

Nucleoside - consists of a

nitrogenous base covalently

attached to a (ribose ordeoxyribose ) sugar but withoutthe phosphate group.

Nucleotide - consists of anitrogenous base, a sugar, anda phosphate group, e.g., ATP,DNA, RNA monomers.


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Cell Structures


- which is the universal energy currency($) of all cells

SUN

Chloroplast

Mitochondria

Glucose

ATP CellularWork

Heat

CO + H O2 2

O2

Overview Aerobic Metabolism

3.Protein SynthesisProteins are key biological molecules associated withmany of the support structures of the body, such as bone,and are associated with all metabolic (chemicalreactions) occurring within the body.

a. Ribosomes-

a non-membrane bound organelle- composed of 2 sub-units, and attached to the ER- made of the nucleic acid rRNA, and proteins- site of protein synthesis

b. Polysomes- free-floating cluster of ribosomes within the

cytoplasm- attached to an mRNA strand, a ble to produce

multiple copies of a protein from the single

O2

H2O

CO2

Glucose + 2 ATP

Mitochondria & Chloroplasts

-

both contain t here own DNA(mtDNA, ctDNA) and proteinsynthesizing ribosomes.

cf. visit Wikipedia for more aboutthe Theory of Endosymbiosis

Cell Structures


mRNA strand (cf.Protein Synthesis:Translation)

- generallyproduce proteins that will be

used inside the cell

4. Fluid Mosaic Model and Related

The cell membrane (also called the plasma membrane, or

"phospholipid bilayer") is a semipermeable lipid bilayercommon to all living cells. It contains a variety or mosaic

of biological molecules, primarilyproteins and lipids,

which are involved in a vast array of cellular processes, and

also serves as the attachment point for both the intracellularcytoskeleton and, if present, the cell wall. The membrane

is not solid butfluid, with shifting phospholipids and

proteins.

Source: http://en.wikipedia.org/wiki/Cell_membrane

a. Cell Membrane selectively permeable membrane, that controls what

substances enter or exit the cell, and protects thecytoplasm

primary structural unit is the phosopholipid

cholesterol is also an important

structural element proteins are found throughout

- Phospholipids (pl)

- main structural element

- selectively permeable

- Lipoprotein (lp)

- cholesterol- structural element

cf. Fluid Mosaic model- Biomolecule notes and Cell

Membrane Transport notes


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Cell Structures


- Carrier protein / Channel protein (cp)

- transport thru the cell membrane

- Glycolipid (gl)

- energy

- recognition site for specific chemicals

- cellular Velcro to form tissue

- Glycoprotein (gp)

- are important for immune cell

recognition, e.g., MHC- bind tissues

- mucin, protective coating

b. Cell Wall

semi-rigid, permeable layer that helps the cellmaintain its shape and chemical equilibrium

Plants cellulose (and lignin) mostly algae - cellulose

fungi chitin

some bacteria -peptidoglycan (murein)

archea - various

Notfound in animal cells

Carrier proteins bind to asubstrate to assist it thru the

lipid bilayer- facilitated and active

transport

Channel proteins are poresthrough which a particle simplyglides thru- facilitated diffusion

Cell Structures


c. Cytoskeleton- The network of filamentous protein structures

within the cell that help it maintain shape,

anchor organelles, or help the organelles move

as necessary.

-

The primary constituents of the cytoskeleton aremicrotubules and microfilaments (proteins).

- Microtubules are hollow, cylindrical aggregates of tube-like

structure that help give the cell shape and form; they are also

involved in other cell processes.

- made up of 13 rows of globular proteins arranged to

form a hollow tube

- serve in moving materials within the cell, cellmovement, cytoskeleton structure.

- Microfilaments are long, thin, contractile rods that appear to

be responsible for the movement of cells (both external and

internal movement).

- made up of double filaments arranged in a helical

pattern, with each filament consisting of numerous

globular proteins joined together.

- serve in anchoring organelles and moving them

within the cell, cell movement, cytoskeleton

structure.

Unipoldia: Extensions of the Cell Membrane

d. Cilia- short, hairlike projections that function in cell

movement

- e.g., sweeping up mucus coated debris from the

bronchi and trachea (respiratory tract)

shorter than flagella beat stiffly, like oars


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Cell Structures


consists of a membrane-bound cylinder, with 9+2arrangement of microtubules.

e. Flagella

-

longer than cilia, but with same basic anatomy ascilia (membrane-bound cylinder, with 9+2 arrangement ofmicrotubules).

- beat in undulating whip-like fashion- function in cell movement (e.g. sperm cells)

5. The Endomembrane System

"eukaryotic cells contain several interrelated membrane-bound compartments, known collectively as theendomembrane system."

- plays both an architectural and biochemical role inmany cellular activities

i.Endoplasmic Reticulum (ER)

- present in all nucleated cells- a system of membrane-bounded channels in the

cytoplasm- serves as routes for transport of materials between

various regions of the cytoplasm or between the variousparts of the cytoplasm and nucleus, forming acommunication network

a.Rough ER- ER lined with ribosomes- associated with cells synthesizing protein -

Translation

b. Smooth ER- ER sans the ribosomes- various functions; synthesis (steroids), storage,

transport of material, and detoxification

Cell Structures


ii.Golgi Apparatus- system of membranous compartments

- central role in processing, packaging, anddistribution of material to and from other regionsof the cell and to and from the outside of the cell

- proteins synthesized in rough ER pass through golgicomplex, and are modified and distributed

- forms 2 types of vesicles; lysosomes and secretoryvesicle

a. Lysosomes- small, often-spherical- characterized by the presence ofacid hydrolase, a

hydrolytic digestive enzyme- Hydrolases are proteins made at the rough ER,

then delivered via the Golgi to the lysosome

Suffix ase indicates anenzyme (a protein that acts as abiological cat alyst).

Proteinprotease" peptides(protein fragments)

Peptidespeptidase" a.a.

Nucleic Acidsnu clease"

nucleotides

Lipidslipase" glycerol +fatty acids


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Cell Structures


- Lysosomes contain many hydrolytic enzymesincluding proteases, nucleases, and lipases.- function is to breakdown both materials brought

into the cell from outside, and of other cellularcomponents already present (autodigestion )

b. Vacuole- a large vesicle

- in animals are a part of the processes ofexocytosis and endocytosis.

- a largesecretory vesicle is a vacuole

- Lysosomes fuse with vacuoles anddispense their enzymes into the vacuoles,digesting their contents.

- inplants, the central vacuole maintainsturgor (shape), and for storage of water a ndwater soluble compounds

Other Organelles you might be expected to know if

Cell Division- Centrioles - animal cells have two cylindrical (non-

membrane bound) bodies, called centrioles, locatednear the nucleus.

- are short cylinders with a 9+0 pattern ofmicrotubular (microtubule proteins) triplets.

- centrioles give rise to basal bodies which.

- assist in the formation of the spindle

apparatus in cell division.- direct the formation of cilia and flagella

Cell Structures


Hydrolytic Vesicles- Peroxisomes - like lysosomes are also single-

membrane organelles.

-

Peroxisomal enzymes remove hydrogen atoms fromsmall molecules and join the hydrogen atoms to

oxygen to form hydrogen peroxide, and then break

it down into water and oxygen.

Review: Label the cell below

Hints:4 is the smaller type10 is the larger type

12 contains acid hydrolase

14 add your own arrow to locate the cell (plasma) membrane

answers on page 2Source: http://en.wikipedia.org/wiki/Image:Biological_cell.svg

Reference: http://en.wikipedia.org/wiki/Organelle

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