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Biology 11

A. Allen

Cytoplasm (cytosol): a cell's inner space

cytosol

Cytosol: large fluid-filled space (mostly water + proteins that control

most of the cell metabolisms): glycolysis, transcription

factors, intracellular receptors etc.

Plasma

membrane

Organelles

• Nucleus

• Protein production machine: the ribosomes

• Mitochondria and Chloroplasts

• Endoplasmic Reticulum and the Golgi apparatus

• Lysosomes and Peroxisomes

• Adapted and/or specialized for carrying out one or more vital functions

Reminder! Membrane-bound

organelles are only found in

eukaryotes.

Nucleus: a cell's center

Function of the nucleus:

• Stores the chromosomes (genetic material) Note: Two kinds of genetic material:

– deoxyribonucleic acid (DNA)

– ribonucleic acid (RNA)

• Keeps the DNA molecules separated from metabolic machinery of cytoplasm.

• Makes it easier to organize

DNA and to copy it before

parent cells divide into

daughter cells

• DNA replication and

synthesis of messenger

RNA (mRNA). The

mRNA is allowed to leave

the nucleus. It is read by

the ribosomes during

protein synthesis.

...Nucleus: a cell's center Nucleolus

• Dense mass of

material in nucleus

• Cluster of DNA and

proteins

• Subunits must pass

through nuclear pores

to reach cytoplasm

• production of

ribosomes in nucleolus

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• Two outer membranes (lipid bilayers)

• Pores span bilayer and controls what

enters/leaves nucleus.

Nuclear Membrane (Envelope) Chromatin

• Cell’s collection of DNA and associated proteins

• A chromosome is one DNA molecule and its associated proteins

• Appearance changes as cell divides

FUNCTION:

• With the help of tRNA, ribosomes use information in mRNA to assemble proteins

• small semi-spherical, black dots

• some are free in cytoplasm (cytoplasmic ribosomes), others are attached to the ER (ER ribosomes)

Ribosomes

STRUCTURE

• ER is a continuation of the outer nuclear membrane.

• Two types: Smooth and Rough. (Rough ER has ribosomes on it)

• Network of membrane that connects nuclear envelope to the cell

membrane

Endoplasmic Reticulum (ER)

…Endoplasmic Reticulum (ER)

FUNCTION:

• Smooth ER (no ribrosomes): responsible for lipid and membrane

protein modifications)

• Rough ER (has ribosomes on it) responsible for the synthesis of

other proteins). The ribosomes assemble the proteins within the

rough ER. Once assembled, the proteins pinch off the ER and are

released in a vesicle.

Endoplasmic Reticulum (ER)

…Endoplasmic Reticulum (ER)

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FUNCTION:

• processes, packages, and, secretes cell products (lipids & proteins)

• Put finishing touches on proteins and lipids that arrive from ER

• Package finished material for shipment to final destinations. (Exocytosis)

• Material arrives

and leaves in vesicles

Golgi Body (Golgi Apparatus) …Golgi Body (Golgi Apparatus)

STRUCTURE

• Double membrane. Inner membrane is

folded for greater surface area. Folds

are called cristae.

• Interior is called the matrix.

• Contain their own genome (distinct

from nuclear genome)

• Self-replicating

FUNCTION

• ‘burns’ food, i.e. glucose to release

energy. Energy is used to make ATP.

ATP is a high-energy molecule that

can be directly used by the cell.

Mitochondria

The “powerhouse” of the cell

…Mitochondria

STRUCTURE

• Formed by Golgi bodies

• Bound by a single membrane

FUNCTIONS

• Digests the food particles inside the cell with help of enzymes. These enzymes work at low pH.

• Involved in autolysis (suicide of cell)

• Digest foreign bacteria that invade a cell

• Recycling of membrane components

• Repair damage to plasma membrane

Lysosomes

• Made by Golgi

• Surrounded by a single membrane

• Get rid of toxic substances

• Many in the liver/ brain

lysosome

Peroxisomes

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FUNCTION:

• maintains the shape of a

plant cell

• found in plants, some fungi,

some protists

• In plants, cell walls are made

of a polysaccharide called

cellulose.

• Structural component that

wraps around the plasma

membrane

Cell Wall …Cell Wall

FUNCTION:

• Photosynthesis: converts sunlight, carbon dioxide,

and water into sugar (makes food for plants)

Chloroplasts

• A large membrane bound sac

FUNCTION:

• storage area for proteins and

water

• Maintain structure in plant cells by means of turgor pressure

Vacuole

• very complex and dynamic cell component!

• organizes and maintains the cell's shape (e.g. epithelial cells of the

gut)

• anchors the organelles in place

• helps during the uptake of external material (endocytosis)

• involvement in cell movement

• growth

Cytoskeleton: a cell's scaffold

microtubules microfilamentsintermediate filaments

tubulin actin keratin family

All help maintain cell shape

Cilia, flagellaChromosome movementOrganelle movement

Cytoplasmic streamingPseudopodiaCell division

Nuclear laminaAnchorage of nucleus and some other organelles

...Cytoskeleton

video

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...Cytoskeleton ...Cytoskeleton

Molecular

motors

...Cytoskeleton

Macrophage attacks bacteria

Microfilaments (actin) allow formation of pseudopods

...Cytoskeleton

Striated Muscle

...Cytoskeleton

Centrosome:Made up of centriole pairs

...Cytoskeleton

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Bibliography

• http://users.ipfw.edu/mustafaa/PQ_B100-02-ppt-Chapter4-Cell%20Structures%20and%20Functions.ppt

• http://images.google.ca/imgres?imgurl=http://biology.dbs.umt.edu/biol101/labs/lab_6_images/sect05and02/cheek%25

20cell%25201000x.jpg&imgrefurl=http://biology.dbs.umt.edu/biol101/labs/lab_6_images/sect05and02/section_2and5

_cellimages.htm&h=768&w=1024&sz=316&tbnid=OxmCr18W6AQJ:&tbnh=112&tbnw=149&start=1&prev=/imag

es%3Fq%3Dcheek%2Bcell%26hl%3Den%26lr%3D

• www.ops.org/burke/02science/organelles.ppt

• file:///C:/WINDOWS/Temporary%20Internet%20Files/Content.IE5/UPK3G94Z/266,12,Diffusion

• http://bioweb.wku.edu/courses/biol22000/11Organelles/images/F05-43A.JPG

• http://cellbio.utmb.edu/cellbio/nucleus.html

• http://www.cellsalive.com/cells/er.htm

• cellbio.utmb.edu/cellbio/ribosome.htm

• http://cellbio.utmb.edu/cellbio/golgi.htm