Chapter 4: Cell Structure and Function

Chapter 4:

Cell Structure and Function

Cytoskeleton

? The cytoskeleton is a network

of fibers that organizes

structures and activities in the

cell.


Microtubules (the largest)


Intermediate fibers


Microfilaments (the smallest)

Think tube vs filaments ¨C tubes are

always larger

Provide shape and support for the cell

MTs

MFs

IFs

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Other functions of the cytoskeleton

? Provide movement


if the organism has flagellum or

cilia

? Intracellular movement


Transports organelles, proteins

and other cell components along

microtubule ¡°rails¡±.

Nucleus

? Only present in eukaryotic cells

? Location of the organism¡¯s

genome


DNA

? Nuclear envelope


Membrane that surrounds the

nucleus


Semipermeable

 does not allow DNA out, but

messenger RNA does leave the

nucleus.

Nucleolus

? Darkly stained regions within

the nucleus

? Ribosome assembly takes

place in this organelle.

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Ribosomes

? Ribosomes


Protein factories


Synthesizes most proteins.

? Two types


Free ribosomes

Found in all cells


Ribosomes attached to the

endoplasmic reticulum (ER)

Endoplasmic reticulum (ER)

? Rough endoplasmic

reticulum


Place where most

ribosomes attach


Protein synthesis &

transportation

? Smooth endoplasmic reticulum


Lipid production, including

steroids.


In liver cells, it detoxify drugs and

alcohol


Also in liver cells, it breaks down

Golgi apparatus

? The warehouse of the cell


Stores, sorts, and transports

proteins and other molecules

within the cell


Directs transportation of

proteins and other molecules

to the outside of the cell.


Also synthesizes cellulose

and pectin (plants)

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Lysosomes

? Made by the golgi

apparatus

? Highly acidic

environments


Due to digestive enzymes.

? Digest waste particles &

malfunctioning

organelles.

Vacuoles

? Food vacuoles


Transport food from cell

membrane to other parts of

the cell.


This process is known as

phagocytosis.

Vacuoles

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Contractile vacuoles

? Freshwater protists need these vacuoles to pump excess

water out of the cell.


Otherwise the cell continues to expand until it explodes.

Paramecium

Central vacuoles

? Found in plant cells

? Storage organelle


Water


May store proteins and

carbohydrates


Provides turgor, giving

plants strength


Wilted plants have little

turgor due to lack of water

Plant turgor

Plant needs water to fill

central vacuoles.

Normal plant

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