CellsCells

Plant & Animal CellsPlant & Animal Cells

CellsCells

How many cells do we have in us?How many cells do we have in us?Brain has estimated 1,000,000,000 neurons Brain has estimated 1,000,000,000 neurons

(one type of cell)(one type of cell)http://www.cybernetics.demon.co.uk/brainsim.htmlhttp://www.cybernetics.demon.co.uk/brainsim.html

Within each cell, there are smaller parts Within each cell, there are smaller parts called called organellesorganelles,, which play different which play different roles in a functioning cell.roles in a functioning cell.

Within each cell, there are smaller parts Within each cell, there are smaller parts called called organellesorganelles,, which play different roles which play different roles in a functioning cell.in a functioning cell.

Cheek cells Onion cells

CellsCells

Animal cellAnimal cell

Cell membraneCell membrane NucleusNucleus Nuclear membraneNuclear membrane CytoplasmCytoplasm MitochondrionMitochondrion Small vacuoleSmall vacuole

Animal cellAnimal cell Cell membraneCell membrane NucleusNucleus Nuclear membraneNuclear membrane NucleolusNucleolus Nuclear poreNuclear pore CytoplasmCytoplasm MitochondrionMitochondrion Small vacuoleSmall vacuole Endoplasmic reticulumEndoplasmic reticulum RibosomesRibosomes Golgi apparatusGolgi apparatus Centrosomes (w centrioles)Centrosomes (w centrioles)

http://distance.stcc.edu/AandP/AP/AP1pages/introduction/cells.htm

Plant cellPlant cell Cell membraneCell membrane NucleusNucleus Nuclear membraneNuclear membrane NucleolusNucleolus Nuclear poreNuclear pore CytoplasmCytoplasm MitochondrionMitochondrion Endoplasmic reticulumEndoplasmic reticulum RibosomesRibosomes Golgi apparatusGolgi apparatus Centrosome (w/o centrioles)Centrosome (w/o centrioles) Cell wallCell wall ChloroplastChloroplast Large vacuole (contains cell sap)Large vacuole (contains cell sap) Starch grains (inside chloroplast)Starch grains (inside chloroplast)

Plant cellPlant cell

Cell membrane Cell membrane

Always presentAlways present Thin boundary enclosing Thin boundary enclosing

cytoplasmcytoplasm Stops cell contents from escapingStops cell contents from escaping Controls substances allowed to Controls substances allowed to

enter and leave cellenter and leave cell Oxygen, food & water allowed inOxygen, food & water allowed in Waste products allowed to leaveWaste products allowed to leave Harmful substances kept OUT!Harmful substances kept OUT!

Thus able to maintain Thus able to maintain structurestructure and and chemical reactionschemical reactions in in cytoplasmcytoplasm

CytoplasmCytoplasm

Always presentAlways present Under light microscope, looks Under light microscope, looks

like thick liquid with particles in itlike thick liquid with particles in it These particles are the cell’s These particles are the cell’s

organellesorganelles..

Site of many chemical reactionsSite of many chemical reactions Liquid part is about 90% water, Liquid part is about 90% water,

with dissolved salts and sugarswith dissolved salts and sugars Proteins (e.g. enzymes) & lipids Proteins (e.g. enzymes) & lipids

are suspended withinare suspended within

NucleusNucleus Present in most cellsPresent in most cells

Exception: e.g. red blood cellException: e.g. red blood cell

Usually only ONE is presentUsually only ONE is present Contains DNA wound up into Contains DNA wound up into

chromosomeschromosomes Controls:Controls:

type and quantity of enzymes type and quantity of enzymes produced in cytoplasmproduced in cytoplasm

Hence determines what the cell Hence determines what the cell will be, e.g. liver cell, muscle cell, will be, e.g. liver cell, muscle cell, nerve cellnerve cell

cell divisioncell division

Nuclear membrane & poresNuclear membrane & pores

Substances may pass Substances may pass through the pores into the through the pores into the cytoplasmcytoplasm mRNA is transcribed in the mRNA is transcribed in the

nucleusnucleus Passes out into cytoplasm Passes out into cytoplasm

where is it translatedwhere is it translated

NucleolusNucleolus

Thought to be region where RNA is madeThought to be region where RNA is made

MitochondrionMitochondrion

Present in majority of cellsPresent in majority of cells Able to move about within Able to move about within

cellcell Internal membrane highly Internal membrane highly

foldedfolded Contains enzymes that Contains enzymes that

control respirationcontrol respiration Are main energy converters Are main energy converters

of the cellof the cell

RibosomeRibosome

Can be free or attached Can be free or attached to the endoplasmic to the endoplasmic reticulumreticulum

Site where proteins are Site where proteins are made (i.e. made (i.e. translationtranslation of of mRNA in proteins)mRNA in proteins)

Endoplasmic ReticulumEndoplasmic Reticulum

Series of tubes & Series of tubes & flattened sacs extending flattened sacs extending throughout cytoplasmthroughout cytoplasm

May change shape and May change shape and connectionsconnections

Enzymes reactions take Enzymes reactions take place on the surfaceplace on the surface

2 types:2 types: Smooth (SER)Smooth (SER) Rough (RER)Rough (RER)

Endoplasmic ReticulumEndoplasmic Reticulum

SERSER Involved in detoxification of Involved in detoxification of

poisons & production of poisons & production of lipids (e.g. filtration and lipids (e.g. filtration and secretion of steroid secretion of steroid hormones)hormones)

E.g. in kidney & liverE.g. in kidney & liver

RERRER Involved in protein Involved in protein

productionproduction

http://www-class.unl.edu/bios201a/spring97/group6/er.html

Golgi ApparatusGolgi Apparatus

Consists of flattened Consists of flattened membrane sacsmembrane sacs

Final packaging location Final packaging location for proteins and lipidsfor proteins and lipids

Vesicles containing these Vesicles containing these substances break away substances break away from the endsfrom the ends

CentrosomeCentrosome

Microtubule organizing Microtubule organizing centre (place where centre (place where microtubules are microtubules are produced)produced)

Animal centrosomes Animal centrosomes have centrioles; plant have centrioles; plant cells don’tcells don’t

When the cell divides, When the cell divides, the centrosome divides the centrosome divides and the centrioles and the centrioles replicate replicate

CentriolesCentrioles

Have a role in Have a role in building cilia and building cilia and flagella, during which flagella, during which time they are referred time they are referred to as basal bodiesto as basal bodies

ChloroplastChloroplast

Present in plant cells & certain single-Present in plant cells & certain single-celled organisms and algaecelled organisms and algae

Has system of membranes thatHas system of membranes thatcarries chlorophyllcarries chlorophyllCarries enzymes that conduct first stages of Carries enzymes that conduct first stages of

photosynthesisphotosynthesisLiquid material between membranes Liquid material between membranes

contains enzymes that continue contains enzymes that continue photosynthesisphotosynthesis

ChloroplastChloroplast

Section through chloroplast (x12000)Section through chloroplast (x12000)

VideoVideo

What is protoplasm?

nucleus

cytoplasm

cell membrane

-living materials of the cell

Cell Organization

PlantPlant AnimalAnimal

Organelles Organelles Nucleus, vacuole, Nucleus, vacuole, chloroplasts.chloroplasts.

Nucleus, cytoplasm,Nucleus, cytoplasm,vacuolevacuole

CellsCells epidermal cellepidermal cell epithelial cellepithelial cell

TissuesTissues epidermal layerepidermal layer epithelial layerepithelial layer

OrgansOrgans LeafLeaf SkinSkin

SystemsSystems NutritionNutrition ProtectiveProtective

OrganismOrganism Balsam plantBalsam plant MouseMouse

Differences between Plant and Animal Cells

PlantPlant AnimalAnimal

1.1. Cellulose cell wall is presentCellulose cell wall is present AbsentAbsent

2.2. Chloroplast is presentChloroplast is present AbsentAbsent

3.3. One or a few large, central One or a few large, central permanent vacuole/spermanent vacuole/s

Many, small, variable size, Many, small, variable size, temporary vacuolestemporary vacuoles

4.4. Larger cell and distinctive Larger cell and distinctive outlineoutline

Smaller cell and not so Smaller cell and not so distinctive outlinedistinctive outline

5.5. Starch granulesStarch granules Glycogen granulesGlycogen granules

Evidence?Evidence?

Break cell membranesBreak cell membranes Centrifuge cell fragments in salt solutionCentrifuge cell fragments in salt solution Spin are varying speeds (slow to fast)Spin are varying speeds (slow to fast) Heaviest organelles settle firstHeaviest organelles settle first

Nuclei, chloroplasts, mitochondria, membrane Nuclei, chloroplasts, mitochondria, membrane fragments, ribosomesfragments, ribosomes

Each fraction studied in isolationEach fraction studied in isolation

NB.NB. Activities of isolated organelles may not be the Activities of isolated organelles may not be the same as their activities in a whole living cell.same as their activities in a whole living cell.

ArtefactsArtefacts

Tissues often undergo drastic treatment Tissues often undergo drastic treatment before examination.before examination.FixationFixationDehydrationDehydrationStainingStaining

Cell structures may be distorted; may not Cell structures may be distorted; may not represent structures found in living cells.represent structures found in living cells.

ArtefactsArtefacts

These artificial features are called These artificial features are called artefactsartefacts..

Take what you’ve learnt with a pinch of Take what you’ve learnt with a pinch of salt; salt; seeingseeing is not always is not always believingbelieving in in these circumstances.these circumstances.

Differentiated Animal CellsDifferentiated Animal Cells

white blood cell

red blood cell

cheek cells

sperm

nerve cell

muscle cell

Amoeba

Paramecium

Differentiated Plant CellsDifferentiated Plant Cells

Onion Epidermal Cells

Root Hair Cell

root hair

Guard Cells

Identify the organelles!Identify the organelles!

A:A: cell wallcell wallB:B: cell membranecell membraneC:C: mitochondrionmitochondrionD:D: nuclear nuclear

membrane/nuclmembrane/nucleuseus

F:F: Nuclear poreNuclear poreG:G:NucleolusNucleolusH:H: VacuoleVacuoleI:I: Golgi Golgi

apparatusapparatus

Modification of Cell Structure for Specific Functions

Differentiation- the process of change into new type of cells/tissues

Root Hair Cell

Red Blood Cell

Xylem vessels

water and minerals enter a plant through the

tiny root hairs

water and minerals enter a plant through the

tiny root hairs

xylemxylem soil particlessoil particles

Root Hair CellRoot Hair Cell

Type of cellsType of cells

FunctionFunction

Cells with elongated protrusion and a large vacuole

absorbs water and dissolved minerals from the roots to all parts of the plantprovide large surface area to volume ratio for efficient absorption

Red Blood CellRed Blood Cell

Type of cellsType of cells

FunctionFunction

Biconcave disc cells without nucleus packed with red pigment, haemoglobin

absorbs oxygen from the lungs to all parts of the bodyprovide large surface area to volume ratio for efficient absorption

XylemXylem

Type of cellsType of cells

FunctionFunction

phloemxylem

cross-section of stem

dead cells thickened with lignin forming a long hollow tube

carries water and dissolved minerals from the roots to all parts of the plantprovide mechanical support to the plant