Cell StructureCell Structure

Chapter 3Chapter 3

3.1 Looking at Cells3.1 Looking at Cells 1600’s the microscope 1600’s the microscope

was inventedwas invented Robert Hooke 1665 Robert Hooke 1665

looked at cork and saw looked at cork and saw little boxes he called little boxes he called “cells”“cells”

Anton Van Anton Van Leeuwenhoek later Leeuwenhoek later looked at pond water looked at pond water and saw tiny animals and saw tiny animals he called “animalcules”he called “animalcules”

Measuring Cell StructuresMeasuring Cell Structures

Based on metric systemBased on metric systemgiga- giga- mega- mega- kilo- hecto- deka- BASE deci- centi- milli- kilo- hecto- deka- BASE deci- centi- milli- micro- micro-

nano-nano-

Giga = G

Mega = M

Micro = µ

Nano = n

Characteristics of MicroscopesCharacteristics of Microscopes Light Microscope – light Light Microscope – light

passes through 1 or more passes through 1 or more lenseslenses

Electron Microscope – Electron Microscope – image made by beams of image made by beams of electronselectrons

Micrograph – image from a Micrograph – image from a microscopemicroscope– Labeled with what kind of Labeled with what kind of

microscope and microscope and magnification valuemagnification value

Magnification – how many Magnification – how many times larger it appearstimes larger it appears

Resolution – measure of Resolution – measure of clarityclarity

Electron Micrograph Ebola Virus

160,000 x magnification

Types of MicroscopesTypes of Microscopes Compound Light Compound Light

MicroscopeMicroscope– 2 lenses with light bulb 2 lenses with light bulb

shining through slideshining through slide– Objective lens in close Objective lens in close

to slideto slide– Ocular lens is near eyeOcular lens is near eye– 40x x 10x = 400x 40x x 10x = 400x

magnificationmagnification– Third lens hurts Third lens hurts

resolutionresolution– Most powerful = 2,000xMost powerful = 2,000x– See something 0.5 See something 0.5 µm µm

in diameterin diameter

40 x

400 x

Electron MicroscopeElectron Microscope– Up to 200,000xUp to 200,000x– Beam and specimen Beam and specimen

must be in vacuum so must be in vacuum so e- don’t bounce off gas e- don’t bounce off gas (no living things)(no living things)

– Transmission Electron Transmission Electron MicroscopeMicroscope Stained with metal ionsStained with metal ions Very thin slices of Very thin slices of

specimenspecimen Internal structuresInternal structures Black and white but Black and white but

computers add colorcomputers add color– Scanning Electron Scanning Electron

MicroscopeMicroscope Specimen coated with Specimen coated with

thin layer of metalthin layer of metal 3-D cell surface3-D cell surface Artificial colorArtificial color

Scanning Scanning Tunneling Tunneling MicroscopeMicroscope– Needlelike probe Needlelike probe

measures measures differences in differences in voltage caused voltage caused by e- that tunnel by e- that tunnel from surface of from surface of objectobject

– 3-D image3-D image– Used on living Used on living

thingsthings

3.2 Cell Features3.2 Cell Features

Cell TheoryCell Theory– All living things are made of cellsAll living things are made of cells– Cells are the basic units of structure and Cells are the basic units of structure and

function in organismsfunction in organisms– All cells arise from existing cellsAll cells arise from existing cells

Cell SizeCell Size Smaller is more efficientSmaller is more efficient Everything must cross cells surfaceEverything must cross cells surface Surface area to volume ratioSurface area to volume ratio

– Too low - substances cannot enter and leave in large Too low - substances cannot enter and leave in large enough numbersenough numbers

– Small cells have a high ratioSmall cells have a high ratio

Common Features of CellsCommon Features of Cells Cell MembraneCell Membrane

– Outer boundary Outer boundary enclosing cell that enclosing cell that separates interiorseparates interior

– Controls flow in and outControls flow in and out

CytoplasmCytoplasm– Cell interiorCell interior

CytoskeletonCytoskeleton– System of microscopic System of microscopic

fibersfibers– Act as support Act as support

structuresstructures

RibosomesRibosomes– Where proteins are Where proteins are

mademade

DNA DNA – All cells have itAll cells have it– Protein instructionsProtein instructions– Regulate cellular Regulate cellular

activitiesactivities– Allows for reproductionAllows for reproduction

ProkaryotesProkaryotes Smallest, simplest, single-Smallest, simplest, single-

celled organismcelled organism No nucleus (and other No nucleus (and other

parts missing)parts missing) Cannot carry out many Cannot carry out many

special functions due to special functions due to missing partsmissing parts

Around at least 3.5 billion Around at least 3.5 billion years ago (bya)years ago (bya)

Nearly 2 bya were only Nearly 2 bya were only organisms on earthorganisms on earth

Very small from 1 – 15 Very small from 1 – 15 µmµm Bacteria Bacteria

– Subset that causes infection Subset that causes infection and food spoilingand food spoiling

CharacteristicsCharacteristics

Large range of Large range of environmentsenvironments

Many grow and Many grow and divide rapidlydivide rapidly

Some don’t need Some don’t need oxygen, others oxygen, others can’tcan’t have it have it

Some make own Some make own foodfood

Everything inside cell Everything inside cell membrane is in cytoplasmmembrane is in cytoplasm

Enzymes and ribosomes free Enzymes and ribosomes free to move aroundto move around

Singular, circular DNA Singular, circular DNA located in centerlocated in center

Cell Wall – surround Cell Wall – surround membranemembrane– Provides structure and Provides structure and

supportsupport No cytoskeleton so cell wall No cytoskeleton so cell wall

gives shapegives shape– Cell wall made of Cell wall made of

polysaccharides connected polysaccharides connected by short amino acid chainsby short amino acid chains

– Some cell walls surrounded Some cell walls surrounded by capsule = by capsule = polysaccharides (allows polysaccharides (allows them to cling to many things)them to cling to many things)

Flagella – long, threadlike structures that provide Flagella – long, threadlike structures that provide movementmovement

Eukaryotic CellsEukaryotic Cells Internal compartmentsInternal compartments Evolved about 2.5 byaEvolved about 2.5 bya Have an internal Have an internal

compartment for DNA = compartment for DNA = nucleusnucleus

Have structures that Have structures that carry out specific carry out specific activities = organellesactivities = organelles

Cytoplasm = everything Cytoplasm = everything inside membrane but inside membrane but outside nucleusoutside nucleus

Membranes connect Membranes connect organelles and provide organelles and provide channelschannels– Form envelopes called Form envelopes called

vesicles that move vesicles that move proteins between proteins between organellesorganelles

FlagellaFlagella CiliaCilia

– – short, hair-like structuresshort, hair-like structures– Used for cell movement Used for cell movement

or movement of or movement of materials over cellmaterials over cell

CytoskeletonCytoskeleton– Protein fibersProtein fibers– Holds cell together, Holds cell together,

keeps it from collapsingkeeps it from collapsing Cytosol – fluid Cytosol – fluid

surrounding surrounding organelles, internal organelles, internal membranes and membranes and cytoskeletoncytoskeleton

The CytoskeletonThe Cytoskeleton Interior framework of animal cellInterior framework of animal cell Protein fibers anchored to inside Protein fibers anchored to inside

of plasma membraneof plasma membrane 3 kinds of fibers3 kinds of fibers

– Actin FibersActin Fibers Long, slender Long, slender

microfilaments microfilaments Made of the protein actinMade of the protein actin Determine shape of Determine shape of

animal cellsanimal cells– MicrotubulesMicrotubules

Hollow tubesHollow tubes Made of protein tubulinMade of protein tubulin Highway for transport Highway for transport

from nucleus to parts of from nucleus to parts of cellcell

– Intermediate fibersIntermediate fibers Thick ropes of proteinThick ropes of protein Frame for ribosomes and Frame for ribosomes and

enzymes keeping them enzymes keeping them in certain locationsin certain locations

The Cell MembraneThe Cell Membrane Fluid, like a soap bubbleFluid, like a soap bubble Lipids form a barrier allowing Lipids form a barrier allowing

only certain things through - only certain things through - selective permeabilityselective permeability

Phospholipid = 2 fatty acids Phospholipid = 2 fatty acids and a phosphate groupand a phosphate group– Polar head – phosphate group; Polar head – phosphate group;

attracted to Hattracted to H2200– 2 nonpolar fatty acid tails; 2 nonpolar fatty acid tails;

repelled by Hrepelled by H2200 Phospholipids are in a Phospholipids are in a

double layer so called the double layer so called the lipid bilayerlipid bilayer

Allows lipids and nonpolar Allows lipids and nonpolar substances to pass throughsubstances to pass through

Membrane ProteinsMembrane Proteins Proteins are made of Proteins are made of

amino acidsamino acids– Some are polar and some Some are polar and some

are nonpolarare nonpolar– Some move aroundSome move around

Marker proteins attached Marker proteins attached to carbohydrate tell what to carbohydrate tell what kind of cell it is (liver, kind of cell it is (liver, heart)heart)

Receptor proteins bind Receptor proteins bind specific substances (signal specific substances (signal molecules)molecules)

Enzymes in cell membrane Enzymes in cell membrane important in biochemical important in biochemical reactionsreactions

Transport Proteins help Transport Proteins help move things in and outmove things in and out

3.3 Cell Organelles3.3 Cell Organelles NucleusNucleus

– Controls most cell functionsControls most cell functions– Surrounded by nuclear envelopeSurrounded by nuclear envelope

Double membrane (two lipid Double membrane (two lipid bilayers)bilayers)

Nuclear pores = small Nuclear pores = small channels allow passage channels allow passage throughthrough

– Nucleolus – ribosomes partially Nucleolus – ribosomes partially assembled hereassembled here

– Most DNA stored hereMost DNA stored here Wound around proteins but in Wound around proteins but in

elongated thin strandselongated thin strands When about to divide they When about to divide they

become more compact into become more compact into chromosomes and form dense chromosomes and form dense rod shaped structuresrod shaped structures

Number of chromosomes Number of chromosomes depends on speciesdepends on species

– Humans = 46Humans = 46– Peas = 14Peas = 14

Ribosomes and Endoplasmic Ribosomes and Endoplasmic ReticulumReticulum

RibososmesRibososmes– Where proteins are madeWhere proteins are made– Made of dozens of different proteins and RNAMade of dozens of different proteins and RNA– May be free in cytosol but proteins made there stay in May be free in cytosol but proteins made there stay in

cellcell

Production of ProteinsProduction of Proteins Endoplasmic Reticulum is a Endoplasmic Reticulum is a

system of internal system of internal membranes that move membranes that move proteins and other structures proteins and other structures through the cellthrough the cell

It is a lipid bilayer with It is a lipid bilayer with embedded proteinsembedded proteins

Rough ERRough ER– Attached ribosomesAttached ribosomes– Proteins made enter ERProteins made enter ER– Pinched off and form Pinched off and form

vesiclesvesicles– Keep separateKeep separate

Smooth ERSmooth ER– No ribosomesNo ribosomes– Make lipidsMake lipids– Break down toxic Break down toxic

substancessubstances

Packaging and Distribution of Packaging and Distribution of ProteinsProteins

Vesicles go from ER to Vesicles go from ER to Golgi ApparatusGolgi Apparatus

Golgi Apparatus Golgi Apparatus – Flattened membrane-Flattened membrane-

bound sacsbound sacs– Enzymes inside modify Enzymes inside modify

proteinsproteins– Modified proteins Modified proteins

repackaged by GA and repackaged by GA and bud offbud off

Lysosomes – vesicle that Lysosomes – vesicle that contains digestive contains digestive enzymesenzymes

Steps of Protein Steps of Protein packaging and packaging and distributiondistribution1)1)Ribosomes on Rough Ribosomes on Rough

ER make proteins ER make proteins and they are and they are packagedpackaged

2)2)Go from ER to GAGo from ER to GA3)3)In the GA proteins In the GA proteins

are modified and are modified and repackagedrepackaged

4)4)Many vesicles move Many vesicles move to cell membrane and to cell membrane and release cargorelease cargo

5)5)Other vesicles remain Other vesicles remain in cell and go a jobin cell and go a job

MitochondriaMitochondria Harvests energy from Harvests energy from

organic compounds to organic compounds to make ATP which is make ATP which is used as energy by cellused as energy by cell

Most ATP is made hereMost ATP is made here Cells that use ATP have Cells that use ATP have

lots of mitochondrialots of mitochondria 2 membranes2 membranes

– Outer = smoothOuter = smooth– Inner = folded; large Inner = folded; large

surface areasurface area Forms 2 compartmentsForms 2 compartments

Mitochondrial DNAMitochondrial DNA DNA and ribosomes DNA and ribosomes

make their own make their own proteins though most proteins though most come from cytosolcome from cytosol

Mitochondrial DNA Mitochondrial DNA (mDNA) is independent (mDNA) is independent from nuclear DNA, from nuclear DNA, similar to circular DNA similar to circular DNA of prokaryotic cellof prokaryotic cell– Believe prokaryotes Believe prokaryotes

were ancestors to were ancestors to mitochondriamitochondria

Structure of Plant CellsStructure of Plant Cells Cell WallCell Wall

– Surrounds cell Surrounds cell membranemembrane

– Made of proteins and Made of proteins and carbohydrates carbohydrates (cellulose)(cellulose)

– Helps support and Helps support and maintain shapemaintain shape

– ProtectionProtection– Connects to other cellsConnects to other cells

ChloroplastsChloroplasts– Use light to make carbohydrates from COUse light to make carbohydrates from CO22 and H and H2200

– Along with mitochondria supplies much of energy Along with mitochondria supplies much of energy needed to power cellneeded to power cell

– 2 membranes2 membranes– Contain their own DNA (ancient prokaryotes)Contain their own DNA (ancient prokaryotes)

Central VacuoleCentral Vacuole– Stores waterStores water– May contain ions, May contain ions,

nutrients, or wastesnutrients, or wastes– When full, cell is rigidWhen full, cell is rigid