Organization of the CellOrganization of the Cell

Cell theoryCell theoryCells are the basic living units Cells are the basic living units of organization and functionof organization and function

All cells come from other cellsAll cells come from other cellsWork of Schleiden, Schwann, Work of Schleiden, Schwann, and Virchow contributed to this and Virchow contributed to this theorytheory

Each cell is a microcosm of lifeEach cell is a microcosm of life

Cell organization and size Cell organization and size permit homeostasispermit homeostasis

Homeostasis:Homeostasis: The The balanced internal balanced internal environment of the body; environment of the body; the automatic tendency of the automatic tendency of an organism to maintain an organism to maintain such a steady state.such a steady state.

Cell surface area-to-Cell surface area-to-volume ratiovolume ratioPlasma membrane must Plasma membrane must be large enough relative be large enough relative to cell volume to regulate to cell volume to regulate passage of materialspassage of materials

Organization is basically the Organization is basically the same in all cellssame in all cells

All cells have a plasma membrane, All cells have a plasma membrane, which is a selective barrierwhich is a selective barrier

Cells have internal organelles that are Cells have internal organelles that are specialized for various functionsspecialized for various functions

Cell size is limited by the surface to Cell size is limited by the surface to volume ratio, so cells remain smallvolume ratio, so cells remain small

Cell shape and size are related to Cell shape and size are related to function. function.

Surface to volume ratioSurface to volume ratio

As the cell size As the cell size increases, the increases, the volume volume becomes too becomes too large for the large for the surface surface membrane to membrane to handle.handle.

Cell surface area-to-volume ratioCell surface area-to-volume ratio

Biological size and cell diversityBiological size and cell diversity

Small size… (add)Small size… (add)

Molecules must be transported to the Molecules must be transported to the locations where they are converted locations where they are converted into other formsinto other forms

With small cell size, distances With small cell size, distances molecules travel within them are molecules travel within them are relatively short which speeds up relatively short which speeds up many cellular activitiesmany cellular activities

Cells are studied by a Cells are studied by a combination of methodscombination of methods

Robert Hooke: identified the Robert Hooke: identified the cell walls and gave the cell walls and gave the structure the name “cell”.structure the name “cell”.

Study of the cell was not Study of the cell was not possible until microscopes. possible until microscopes.

MicroscopesMicroscopes Light microscopeLight microscope, referred to as , referred to as

compoundcompound microscope, used by microscope, used by most studentsmost students

Two features determine how Two features determine how clearly an object is viewedclearly an object is viewedMagnification: how much largerMagnification: how much largerResolution: how clearResolution: how clear

Light microscope has 500 times Light microscope has 500 times more resolution than human eyemore resolution than human eye

Electron microscopeElectron microscopeDeveloped in the 1950sDeveloped in the 1950sAllows study of the Allows study of the ultrastructure of cellsultrastructure of cells

10,000 times more 10,000 times more resolution than human resolution than human eyeeye

Types of electron microscopeTypes of electron microscope Transmission electron Transmission electron

microscopemicroscope: used for studying : used for studying ultra structure. Specimen must ultra structure. Specimen must be specially prepared and be specially prepared and sliced very thin.sliced very thin.

Scanning electron microscopeScanning electron microscope: : bounces electrons off a thin bounces electrons off a thin metallic coating on the object. metallic coating on the object. Enables surface area to be Enables surface area to be viewed. viewed.

Comparing light and electron microscopyComparing light and electron microscopy

Cell fractionationCell fractionation Used to determine function of Used to determine function of

organelles organelles Cells broken apart and the Cells broken apart and the

resulting cell extract spun in a resulting cell extract spun in a centrifugecentrifuge

Centrifugal force separates Centrifugal force separates extractextractPellet: solid particlePellet: solid particleSupernatant: fluid materialSupernatant: fluid material

Cell fractionationCell fractionation

Types of CellsTypes of Cellshttp://www.tvdsb.on.ca/westmin/science/sbi3a1/Cells/cells.htmhttp://www.tvdsb.on.ca/westmin/science/sbi3a1/Cells/cells.htm

Prokaryotic Cells: Bacteria and ArcheaProkaryotic Cells: Bacteria and Archea

1. lack membrane bound organelles1. lack membrane bound organelles

2. smaller in size than eukaryotes2. smaller in size than eukaryotes

3. DNA is located in nucleoid area and 3. DNA is located in nucleoid area and is not bound by a nuclear membraneis not bound by a nuclear membrane

4. Most have cell walls4. Most have cell walls

5. Have ribosomes and storage 5. Have ribosomes and storage granulesgranules

Eukaryotic cells: all other organismsEukaryotic cells: all other organisms

1. nucleoplasm: contains 1. nucleoplasm: contains chromosomes which package DNAchromosomes which package DNA

2. cytoplasm: area outside the 2. cytoplasm: area outside the nucleus; contains cytosol and nucleus; contains cytosol and organelles, many of which are organelles, many of which are membrane-boundmembrane-bound

3. type of cell determines which 3. type of cell determines which organelles are present and in what organelles are present and in what numbersnumbers

Functions of cell membranesFunctions of cell membranesDivide cell into Divide cell into compartments, allowing for compartments, allowing for specialized activitiesspecialized activities

Interacting membranes Interacting membranes form endomembrane form endomembrane systemsystem

Vesicles transport materials Vesicles transport materials between compartmentsbetween compartments

Diagram ofDiagram ofa a plant cellplant cell

Diagram ofDiagram ofan an animal cellanimal cell

The cell nucleusThe cell nucleus Contains DNAContains DNA Bounded byBounded by

Nuclear envelopeNuclear envelope Double membrane perforated with Double membrane perforated with

nuclear poresnuclear pores DNA forms chromatin, which is DNA forms chromatin, which is

organized into chromosomesorganized into chromosomes NucleolusNucleolus

RNA synthesis and ribosome assemblyRNA synthesis and ribosome assembly

The cellThe cellnucleusnucleus

Endoplasmic reticulum (ER)Endoplasmic reticulum (ER) Network of folded internal Network of folded internal

membranes in the cytosolmembranes in the cytosol Smooth ER Smooth ER

Site of lipid synthesisSite of lipid synthesisSite of detoxifying enzymesSite of detoxifying enzymes

Rough ERRough ERRibosomes manufacture proteinsRibosomes manufacture proteinsProteins may be moved into the Proteins may be moved into the ER lumenER lumen

EndoplasmicEndoplasmicreticulum (ER)reticulum (ER)

Golgi complexGolgi complex Cisternae that process, sort, and Cisternae that process, sort, and

modify proteins modify proteins In animal cells, Golgi complex In animal cells, Golgi complex

also manufactures lysosomes also manufactures lysosomes Glycoproteins transported to Glycoproteins transported to

the cis facethe cis face Golgi modifies carbohydrates Golgi modifies carbohydrates

and lipids and packages into and lipids and packages into vesicles; which then may leave vesicles; which then may leave the cellthe cell

Golgi complexGolgi complex

Lysosomes break down worn-out Lysosomes break down worn-out cell structures, bacteria, and cell structures, bacteria, and other substances other substances Primary lysosomes bud from the Primary lysosomes bud from the

Golgi complexGolgi complex Secondary lysosomes form by Secondary lysosomes form by

fusion of a primary lysosome with a fusion of a primary lysosome with a vesicle containing ingested vesicle containing ingested materialmaterial

Involved in apoptosis (programmed Involved in apoptosis (programmed cell death)cell death)

LysosomesLysosomes

Peroxisomes metabolize small Peroxisomes metabolize small organic compoundsorganic compounds

Transfer hydrogen from various Transfer hydrogen from various compounds to oxygen, forming compounds to oxygen, forming hydrogen peroxidehydrogen peroxide

Catalase is an enzyme that breaks Catalase is an enzyme that breaks down hydrogen peroxidedown hydrogen peroxide

Most common in cells that Most common in cells that synthesize, store, and degrade lipidssynthesize, store, and degrade lipids

Peroxisomes and lysosomesPeroxisomes and lysosomes

VacuolesVacuoles

Large, fluid-filled sacs with a variety Large, fluid-filled sacs with a variety of functions.of functions.

May function in storage of toxins or May function in storage of toxins or pigmentspigments

Plant vacuoles are typically large and Plant vacuoles are typically large and allow the cell to increase in sizeallow the cell to increase in size

Protist vacuoles may involve Protist vacuoles may involve digestion or excretion. digestion or excretion.

Mitochondria Mitochondria Sites of aerobic respirationSites of aerobic respiration Organelles enclosed by a double Organelles enclosed by a double

membranemembrane Cristae and matrix contain Cristae and matrix contain

enzymes for aerobic respirationenzymes for aerobic respiration Nutrients broken down and energy Nutrients broken down and energy

packaged in ATPpackaged in ATP Carbon dioxide and water by-productsCarbon dioxide and water by-products

Mitochondria Mitochondria

Chloroplasts Chloroplasts Plastids that carry out Plastids that carry out

photosynthesisphotosynthesis Inner membrane of chloroplast Inner membrane of chloroplast

encloses the stromaencloses the stroma During photosynthesis, During photosynthesis,

chlorophyll traps light energychlorophyll traps light energy Energy converted to chemical Energy converted to chemical

energy in ATP; sugars/food for energy in ATP; sugars/food for the plant are manufactured. the plant are manufactured.

ChloroplastChloroplast

Cellular respiration and photosynthesisCellular respiration and photosynthesis

Equation for photosynthesisEquation for photosynthesis

6H6H22O + 6COO + 6CO22 CC66HH1212OO6 6 ++ 6 O6 O22

If you turn the arrow around, If you turn the arrow around, you have the equation for you have the equation for cellular respiration.cellular respiration.

Cytoskeleton Cytoskeleton Internal framework made ofInternal framework made of

MicrotubulesMicrotubulesMicrofilamentsMicrofilaments Intermediate filamentsIntermediate filaments

Provides structural supportProvides structural support Involved with transport of Involved with transport of

materials in the cellmaterials in the cell

TheThe

CytoskeletonCytoskeleton

Cilia and flagella Cilia and flagella Thin, movable structures Thin, movable structures that project from cell that project from cell surfacesurface

Function in movementFunction in movementMicrotubles anchored in Microtubles anchored in cell by basal bodycell by basal body

StructureStructureof ciliaof cilia

Cilia and flagellaCilia and flagella

Glycocalyx, cell coat formed Glycocalyx, cell coat formed by polysaccarides extending by polysaccarides extending from plasma membranefrom plasma membrane

Many animal cells also Many animal cells also surrounded by an surrounded by an extracellular matrix (ECM)extracellular matrix (ECM)

Most bacteria, fungi, and Most bacteria, fungi, and plant cell walls made of plant cell walls made of carbohydratescarbohydrates

Extracellular matrixExtracellular matrix

PlantPlantcell wallscell walls