Cell Structure

& Function

http://koning.ecsu.ctstateu.edu/cell/cell.html

Definition of Cell

A cell is the smallest unit that is

capable of performing life

functions.

Examples of Cells

Amoeba Proteus

Plant Stem

Red Blood Cell

Nerve Cell

Bacteria

Two Types of Cells

•Prokaryotic

•Eukaryotic

Prokaryotic • Do not have

membrane bound organelles (structures surrounded by membranes)

• Few internal structures

• One-celled organisms

• Example: Bacteria

http://library.thinkquest.org/C004535/prokaryotic_cells.html

Eukaryotic Cells • Contain organelles surrounded by membranes

• Includes most living organisms both single & multi-cellular

• Carry out more specialized functions than prokaryotic cells

b/c of their complex organization

Plant Animal

http://library.thinkquest.org/C004535/eukaryotic_cells.html

“Typical” Animal Cell

http://web.jjay.cuny.edu/~acarpi/NSC/images/cell.gif

http://waynesword.palomar.edu/images/plant3.gif

“Typical” Plant Cell

Cell Parts

Organelles “little organs”

Surrounding the Cell

Cell Membrane

• Outer membrane of cell that controls movement

in and out of the cell

• Double layer called the phospholipid bilayer

http://library.thinkquest.org/12413/structures.html

• Also called the Plasma Membrane

Cell Wall

• Most commonly found

in plant cells, fungi

cells & bacteria

• Supports & protects

cells

• Double layer

http://library.thinkquest.org/12413/structures.html

Flagella & Cilia

Flagella- whip-like projections

Cilia- hair-like projections

Both are used for movement;

composed of cytoskeleton

filaments & protein; covered in an

extension of the cell membrane

Inside the Cell

Nucleus • Directs cell activities

• Separated from cytoplasm by nuclear

membrane

• Contains genetic material (DNA) inside the

nucleolus

Nuclear Membrane

• Surrounds nucleus

• Made of two layers

• Openings called

nuclear pores allow

material to enter and

leave nucleus

http://library.thinkquest.org/12413/structures.html

Chromatin/Chromosomes

• In nucleus

• Chromatin is DNA &

protein in a loose

network of bumpy

threads (condenses

to form chromosomes

during cell division)

• Contain instructions

for traits &

characteristics

http://library.thinkquest.org/12413/structures.html

Nucleolus

• Inside nucleus

• Contains RNA to build

proteins

• ribosome parts are

made here

http://library.thinkquest.org/12413/structures.html

Cytoplasm

• Gel-like mixture

• surrounded by cell membrane

• Organelles are supported by the

cytoplasm

• Site of most cellular activities (like the

factory area of the cell)

Endoplasmic Reticulum • System of canals that

coils & twists through the

cytoplasm

• Moves materials around

in cell

• Smooth ER: lacks

ribosomes, functions in

lipid metabolism (making

& breaking down

cholesterol and fats) and

detoxification of drugs

and pesticides http://library.thinkquest.org/12413/structures.html

Endoplasmic reticulum (cont.)

Rough ER:

•Has ribosomes on the surface

•Proteins made by the ribosomes

enter the rough ER then fold into

their functional 3-dimensional

shape. They are then transported

to other areas of the cell in

vesicles.

Ribosomes

• Each cell contains

thousands

• Makes proteins

• Floating free

throughout the cell

• Composed of 2

subunits

http://library.thinkquest.org/12413/structures.html

Mitochondria • Produces energy (ATP)

by breaking down food

(cellular respiration)

• Regulates cellular

metabolism

• Surrounded by 2

membranes

• Has its own DNA &

ribosomes!

• „busy‟ cells have

hundreds of mitochondria http://library.thinkquest.org/12413/structures.htl

Golgi Bodies or Golgi Apparatus • Stack of flattened

membrane bound

sacs

• Major function is to

modify & package

proteins

• Modifies, sorts, and

packages materials

for export from the

cell

http://library.thinkquest.org/12413/structures.html

Lysosome • Contains powerful

digestive enzymes

• Digestive „factory' for

proteins, fats, and

carbohydrates

• Abundant in cells that

dispose of bacteria &

cell debris

• Cell is digested if a

lysosome explodes

http://library.thinkquest.org/12413/structures.html

Peroxisomes

•Most important

function is to convert

free radicals into

hydrogen peroxide

(H2O2)

•If left to accumulate,

free radicals can have

devastating effects on

cells

Vacuoles/ Central Vacuole

• Membrane-bound

sacs for storage,

digestion, and waste

removal

• Contains water, ions,

nutrients, & wastes

• Very large in plants;

maintain plant shape

by holding lots of

water

http://library.thinkquest.org/12413/structures.html

Chloroplast

• A plastid found in

plant & algae cells

• Contains green

chlorophyll

• Where

photosynthesis takes

place

http://library.thinkquest.org/12413/structures.html

Cytoskeleton

•Elaborate network of protein structures that

extends throughout the cytoplasm

•Acts as the cells “bones & muscles” by providing

an internal framework that determines cell shape,

supports other organelles, and provides a route

for intracellular transport

•Made up of microfilaments,

micrtubules, & intermediate

filaments

Centrioles •Rod-shaped structures that direct

the formation of spindle fibers

during mitosis & meiosis

•Made of microtubles

Vesicles

These are not actually organelles.

This is a generic term for any

material that is enclosed in a

membrane. Vesicles are pinched

off from the golgi body, cell

membrane, and ER. They may

contain hormones, proteins,

nutrients, etc.