Cell Structure & Function

Cell TheoryAll living things are made up of cells. Cells are the smallest working units of all

living things. All cells come from preexisting( قبلي (وجود

cells through cell division.

Definition of Cell

A cell is the smallest unit that is capable of performing life functions.

Examples of CellsAmoeba Proteus

Plant Stem

Red Blood Cell

Nerve Cell

Bacteria

Two Types of Cells•Prokaryotic•Eukaryotic

ProkaryoticDo not have

structures surrounded by membranes

Few internal structures

One-celled organisms, Bacteria

EukaryoticContain organelles surrounded by

membranesMost living organismsPlant Animal

“Typical” Animal Cell

A animal cell

Rough ER Smooth ER

Centrosome

CYTOSKELETON

Microfilaments

Microtubules

Microvilli

Peroxisome

Lysosome

Golgi apparatus

Ribosomes

In animal cells but not plant cells:LysosomesCentriolesFlagella (in some plant sperm)

Nucleolus

Chromatin

NUCLEUS

Flagelium

Intermediate filaments

ENDOPLASMIC RETICULUM (ER)

Mitochondrion

Nuclear envelope

Plasma membrane

A plant cell

In plant cells but not animal cells:ChloroplastsCentral vacuole and tonoplastCell wallPlasmodesmata

CYTOSKELETON

Ribosomes (small brwon dots)

Central vacuole

Microfilaments

Intermediate filaments

Microtubules

Rough endoplasmic reticulum Smooth

endoplasmic reticulum

ChromatinNUCLEUS

Nuclear envelope

Nucleolus

Chloroplast

PlasmodesmataWall of adjacent cell

Cell wall

Golgi apparatus

Peroxisome

Tonoplast

Centrosome

Plasma membrane

Mitochondrion

Cell PartsOrganelles

Surrounding the Cell

Cell MembraneOuter membrane of

cell that controls movement in and out of the cell

Double layer

Inside the Cell

Nucleus Directs cell activitiesSeparated from cytoplasm by nuclear

membraneContains genetic material - DNA

Nuclear MembraneSurrounds nucleusMade of two layersOpenings allow

material to enter and leave nucleus

The nuclear envelope Encloses the nucleus, separating its contents

from the cytoplasm Nucleus

NucleusNucleolus

Chromatin

Nuclear envelope:Inner membrane

Outer membrane

Nuclear pore

Rough ER

Porecomplex

Surface of nuclear envelope.

Pore complexes (TEM). Nuclear lamina (TEM).

Close-up of nuclearenvelope

Ribosome

1 µm

1 µm

0.25 µm

ChromosomesIn nucleusMade of DNAContain

instructions for traits & characteristics

NucleolusInside nucleusContains RNA to

build proteins

CytoplasmGel-like mixtureSurrounded by cell membraneContains hereditary material

Endoplasmic ReticulumMoves materials

around in cellSmooth type: lacks

ribosomesRough type (pictured):

ribosomes embedded( جزءا (يجعلهin surface

The ER membraneIs continuous with the nuclear envelope

Smooth ER

Rough ER

ER lumenCisternae

RibosomesTransport vesicleSmooth ER

Transitional ER

Rough ER 200 µm

Nuclearenvelope

RibosomesEach cell contains

thousandsMake proteinsFound on

ribosomes & floating throughout the cell

MitochondriaProduces energy

through chemical reactions – breaking down fats & carbohydrates

Controls level of water and other materials in cell

Recycles and decomposes(يحلل) proteins, fats, and carbohydrates

Mitochondria are enclosed by two membranesA smooth outer membraneAn inner membrane folded into cristae

Mitochondrion

Intermembrane space

Outermembrane

Freeribosomesin the mitochondrialmatrix

MitochondrialDNA

Innermembrane

Cristae

Matrix

100 µm

Golgi BodiesProtein 'packaging

plant'Move materials

within the cellMove materials

out of the cell

Golgiapparatus

TEM of Golgi apparatus

cis face(“receiving” side ofGolgi apparatus)

Vesicles movefrom ER to Golgi Vesicles also

transport certainproteins back to ER

Vesicles coalesce toform new cis Golgi cisternae

Cisternalmaturation:Golgi cisternaemove in a cis-to-transdirection

Vesicles form andleave Golgi, carryingspecific proteins toother locations or tothe plasma mem-brane for secretion

Vesicles transport specificproteins backward to newerGolgi cisternae

Cisternae

trans face(“shipping” side ofGolgi apparatus)

0.1 0 µm16

5

2

3

4

Functions of the Golgi apparatus

LysosomeDigestive 'plant' for

proteins, fats, and carbohydrates

Transports undigested material to cell membrane for removal

Cell breaks down if lysosome explodes

Lysosomes carry out intracellular digestion by

Phagocytosis(بلعم) (قووتدان)

(a) Phagocytosis: lysosome digesting food

1 µm

Lysosome containsactive hydrolyticenzymes

Food vacuole fuses with lysosome

Hydrolyticenzymes digestfood particles

Digestion

Food vacuole

Plasma membraneLysosome

Digestiveenzymes

Lysosome

Nucleus

ChloroplastUsually found in

plant cellsContains green

chlorophyllWhere

photosynthesis takes place

The cytoskeletonIs a network of fibers extending throughout the

cytoplasmMicrotubule

0.25 µm Microfilaments

Contains a pair of centrioles

Centrosome

Microtubule

Centrioles

0.25 µm

Longitudinal sectionof one centriole

Microtubules Cross sectionof the other centriole

In Summary

There are two major types of cellsProkaryotic

Found in Domains Bacteria and Archaea Kingdoms Eubacteria and Archaebacteria

EukaryoticFound in Domain Eukarya

Kingdoms Plantae Animalia

Major CharacteristicsProkaryotes

SmallSimple cellsHave cell membrane, cytoplasm, ribosomes,

DNA in form of “nucleoid”Sometimes have cell wall, capsule, other

projections from wall (bacterial cilia, pili)DO NOT HAVE internal organelles or nucleus

Major CharacteristicsEukaryotes

LargerComplex cellsHave cell membrane, cytoplasm, ribosomes,

DNA in form of “chromosomes”Sometimes have cell wall (plants and fungi)

and structures for movement (cilia and flagella)HAVE internal organelles and nucleus