Chapter 4

Structure and Function of the Cell

4-1 Introduction to the Cell Biology – The study of life

Bio – life Ology – study of

Cell – smallest unit of matter that can carry on all life functions

I. Discovery of the cell Early 17th century (a.k.a. 1600’s) –

discovery of the microscope 1665:

ROBERT HOOKE The man the

discovered cells! Looked at a slice of

cork Plant cells

Saw “little boxes” Reminded him of small

rooms that monks lived in called cells

So that is how cells got their name!

Cell Theory 150 years later …. Cell theory – 3 parts

1. All living things are composed of at least one cell

2. Cells are the basic unit of structure and function in an organism

3. Cells come from other cells

II. Cell diversity

A. Size Most are microscopic few are seen by the

naked eye Size is limited by: Ratio of surface area to volume

Nutrients must enter the cell If it is too large – materials won’t enter the

cell fast enough

B. Shape Shape reflects function

Examples:

Nerve cell Branched and long Job: Transmit

information

Skin cells Flat and layers of

dead cells Job: Protection

White Blood Cells Blob – move through

small openings and eat bacteria

Job: kill bad things

C. Internal Organization Organelles – cell component that performs

a specific function Like organs of the body – “Itty bitty baby

organs”

EUKARYOTIC CELL Eukaryotic cell – has a nuclear membrane

and membrane- bound organelles Just like you and me!! All cells that are not bacteria

PROKARYOTIC CELL No membrane – bound organelles No nuclear membrane Example: bacteria cells

4-2 Parts of the eukaryotic cell

Eukaryotic cells are different Three main parts

1. Cell membrane

2. Organelles

3. Nucleus

I. Cell Membrane Holds everything inside the cell Semipermeable – (selectively permeable) –

Only allows some things through

Cell Mem. Make-up Made of:

Phospholipid bilayer – fat with a phosphate group attached

Proteins – allows certain things through

The phospholipid Hydrophilic end Hydrophobic end Latin:

Hydro=__________ Philic=__________ Phobic=__________

The cell membrane Proteins Some proteins

go all the way through the mem.

These serve as channels or pores

Fluid Mosaic Model of cell mem What is a mosaic?

Fluid Mosaic Model of cell mem For many years scientists thought that

proteins were static (stuck in 1 place)

The phospholipid bilayer behaves more like a fluid than a solid Proteins can move Cell membrane is always changing

II. Organelles of eukaryotic cells Organelles – Parts that make-up the cell

1. Cytoplasm Area between cell mem. and nucleus Also called cytosol

2. Mitochondria (MIGHTY) Powerhouse of the cell

(Makes energy) Makes ATP (adenosine

triphosphate) -molecule that gives us energy

Double membrane with series of folds (Cristae)

Highly active cells= lots of mitochondria

Has own DNA Comes from your mama

Mitochondria

3. Ribosome Help make proteins Most numerous NOT membrane bound (in bth eukaryotic

and prokaryotic cells) Some are free others are attached to the

endoplasmic reticulum

Ribosome

4. Endoplasmic Reticulum System of tubules and sacs Function= path for molecules Two types:

1. Rough E.R. – has ribosomes

2. Smooth E.R.- no ribosomes

Smooth Endoplasmic Reticulum Forms channels

within the cell Breaks down and

make lipids Helps detoxify

chemicals

Rough Endoplasmic Reticulum Rough b/c of

ribosomes on the outside

Ribosomes help make proteins

RER connects to the nucleus and helps make proteins

E.R.

5. Golgi Body (apparatus) Processing,

packaging, and shipping proteins

Stacked membranes Vesicles (membrane

bound bags) carry materials.

Golgi

Protein from rough E.R to golgi

6. Lysosome Latin: Lys – to break or split Sac filled with digestive enzymes Digests anything bad – like the garbage

disposal of the cell. Suicide sac-can kill a cell

Human hand begins as a solid and lysosome kills cells to make spaces btwn fingers

Lysosome

7. Cytoskeleton Provides support Move organelles within the cytoplasm Two types:

1. Microfilaments – play a role in cellular movement

2. Microtubules – form spindle fibers (attach to centrioles and chromosome during cellular division

Microtubules/Spindle fibers

8. Cilia Short hair like extensions that help with

movement (made of microtubules) Single-celled organisms use it to move Multi-cellular organisms use it to clean

Ex: Respiratory system

Paramecium w/ cilia

9. Flagella One up to a few long whip – like

extensions Whip around to move a cell

Flagellum example:

A SPERM CELL!!!

Cilia and Flagella

III. Nucleus

Filled with Nucleoplasm

Three main parts1. Surrounded by semi permeable membrane

(Nuclear membrane/ envelope) Double mem. That surrounds the nucleus Has pores

2. Nucleolus Helps make ribosomes

3. DNA

DNA (Deoxyribonucleic acid) Two forms of DNA

1. Chromosome )( - DNA is condensed around proteins – ONLY during cellular reproduction

2. Chromatin – DNA is all spread out like a plate of spaghetti

Nucleus

The Cell

IV. Plant Cell

Plant cells have all the other organelles + three others

1. Cell Wall Outside the cell membrane Helps support and protect

2. Vacuole Storage for water and

food Much larger in plant

cells May not exist in some

animal cells

3. Chloroplasts

Contain chlorophyll Chlorophyll is the

pigment that allows plants to make food