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Structure and

Function of the Cell

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Blood Cells

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Sperm Cells

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How did we find out about

cells?

Robert Hooke in 1665

Described little boxes thatlooked like the CELLS  thatmonks lived in

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8 Years later...

Dutch microscope maker Anton vanLeeuwenhoek was the first toobserve living cells in 1673

Also observed some

microorganisms

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Observations recorded in over 200 letters

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Who Discovered the Cell

Theory?Schwann, Schleiden, and Virchow

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Matthias Schleiden 1838

German Botanist

Concluded thatall plants weremade of cells

Observed crosssections ofstems

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Theodore Schwann 1839

Germancytologist and

physiologist

Concluded thatall animalswere made upof cells

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Rudolf Virchow 1855

All cells comefrom previously

existing cells

Described the“

human body as acell state in whicheach cell is acitizen” 

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The Cell Theory

1. All living things are made ofcells

2. A cell is the smallest unit of life3. All cells come from pre-existing

cells

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Cell Size

Some are tiny (bacteria)and some are long (nervecells)

All are microscopicLargest cells by volume

are eggs

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Cell Shapes

Different shapes for different functions!Nerve Cells are long to transmit information

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Red Blood Cells are shaped like a Frisbee toslip through small openings while still having

lots of membrane surface

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•Muscle Cells are tightly packed to work together

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Life Begins with the Cell 

BiosphereEcosystemsCommunitiesPopulationsOrganismsOrgan Systems

TissuesCells Molecules

Atoms

Life 

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Internal Organization

All cells haveA cell membraneDNA

CytoplasmRibosomes

Only some cells have a nucleusProkaryotic -noEukaryotic -yes “ you are a eukaryote” 

Only some cells have organelles, cellcomponents that performs specific

functions 

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Classification of Life is Based

on Cell Structure

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Prokaryotic Cells

“Pro-no” – no nucleus or membranesaround organelles

These are bacterial orarchaebacterial cells

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Bacterial cells have strong protective

capsules and compact shapes

Streptococcus, Bacillus subtilis, Borrelia burgdorferi (Lyme Disease)

CocciBacilli

Spirochaete

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Structure of Prokaryotes

Cell wall (also sometimes a capsule)

Protection from outside

environmentSupport/stiffness

Some have pilli for attachment

Cell membraneRegulate what enters/leaves cell

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Structure of Prokaryotes

A single DNA strand (geneticmaterial)

Ribosomes in cytoplasm makeproteins

Some have flagella for

movement

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A

ProkaryoticCell

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Bacterial cells on the

head of a pin

http://www.cellsalive.com/howbig.htm animation

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Ribosomes

Make proteins

May be 100’s to

1,000’s per cellFound in all cells

Made only of rRNAand proteinsShaped roughly like a

donut

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Cytoplasm

A jelly-like material that fills the cell

Mostly water

Contains molecules, nutrients,organelles

Allows particles to meet and mix

Sometimes called Cytosol (cellsolution)

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Eukaryotic Cells

Eukaryotes

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Eukaryotes

Eukaryotic cells have a nucleus

More complex structure with “rooms” 

Start at 1,000 times larger thanprokaryotes

All multicellular organisms areeukaryotesKingdoms Animalia, Plantae, fungi, and

Protista are all eukaryotes

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Eukaryotic Cells

NucleusOrganelles with their own

membranesCytoskeletonComplex fluid mosaic

membraneMuch larger size

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Parts of the Eukaryotic Cell

Chapter 4 Section 2

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Cell Membrane

Isolate the cytoplasm from theenvironmentRegulates what enters and leaves

the cellNutrients in and wastes out

Selectively permeable – only lets

certain things in and outFlexible and changeable fluid

mosaic

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Phospholipid Bilayer

Membrane has embedded proteinsPeripheral- located on the

interior/exterior surface of membrane

Integral- are embedded in themembrane

Proteins play a vital

role in transportingmaterials across a

membrane!

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Membrane StructurePhospholipids have both hydrophilic and

hydrophobic regionsNonpolar tails (hydrophobic) are directed

inward, polar heads (hydrophilic) are

directed outward to face bothextracellular and intracellular fluid

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Nucleus

Contains instructions for makingeverything the cell needsThis is chromatin, DNA wrapped around

proteins

The red circles

are histones

(proteins), the

DNA wraps

around the

histones. The

histone DNA

combo wraps

around itself toeventually form

chromosomes!

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Nucleus

Is an inner chamber surrounded byits own membrane

Pores allow mRNA, signal moleculesto enter and leaveNucleolus is a ball of RNA that makes

ribosomes

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Nucleus

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Mitochondria

“Powerhouse” of the cell

Breaks apart glucose to load ATPmolecules with energyCellular Respiration

Some cells have thousands ofthem

A membrane-bound organelle

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Mitochondrion

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Endoplasmic Reticulum

(ER)A system of bubbles and chambers

that form and change constantly

Act like moveable rooms inside thecellContain and transport molecules

Stays near the nucleusRough ER-ribosomesSmooth ER

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Endoplasmic Reticulum

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Golgi Apparatus

Also called Golgi complex or Golgibody

Made of layers of smoothmembranesA cell that does a lot of exporting

has many golgiThink of a golgi as the UPS station

of the cell

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Golgi Apparatus

Stays near the outer cell membrane

Packages and processes proteins

Accepts the polypeptide from RERPackages/folds it into a final shape

Labels it with destination marker

Processes it through the cell andreleases it as a protein

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Golgi Body

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Lysosomes

Bubbles of membranematerial

Have enzymes tobreak down unwantedmaterials like wastes

and toxinsThese are like little

cell “stomachs” 

Th E d b S

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The Endomembrane System 

 NOTE: Endo= internal

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Cell animation 

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Cytoskeleton

Maintains shape andsize of cell

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Cytoskeleton

Made from stiffmolecules which worktogether for internaland external cellmovementMicrofilaments made

of actin proteinMicrotubules made

of tubulin protein

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Cytoskeleton

Only animal cells have an extensive cytoskeleton.

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Cilia and Flagella

Hair-like structures on theoutside of a cell

Function is movement

Cilia are like many small oars

Flagella are like whips, one or fewBoth are extensions of the

cytoskeleton

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Cilia and Flagella

cilia

flagellum

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Centrioles

Consist of 2 shortcylinders ofmicrotubules at right

angles to each otherand are situated in thecytoplasm near thennuclear env.

Found in animal cells;organize microtubulesof the cytoskeletonduring cell division

l ll

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Prokaryotic

CellsCell membrane

Cell wall/capsule

CytoplasmDNA in a loop

Ribosomes

Very small

Animal CellsComplex cell membrane

with proteinsNo cell wallCytoplasmDNA as chromatin,

inside nucleusRibosomesMembrane-bound

organelles like ER,Golgi, mitochondriaCytoskeleton1,000s times larger

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You

will

needto

know

all

theseparts!

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How Plants Cells Differ from

Animal CellsThey also havea cell wall

large vacuoleplastids (chloroplasts, chromoplasts,

leucoplasts)

Plant cells lack Cilia, FlagellaFully developed cytoskeleton

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Plant Cell Walls

Made from cellulose

Outside of the cell membrane

Acts as support

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Vacuoles

Large sac that takes

up the majority of aplant cell

Stores water

May store poisonsand wastes as well

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Turgor Pressure 

Pressure of a full vacuole againstcell wall

Holds plant up

Wilting is loss of turgor pressure

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Plastids

Double membrane organelles that canstore starch or fatMost common plastid is the

chloroplastOrganelle that conducts

photosynthesis

Numerous in some cells and absentin others

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Chloroplasts

Use light energy to make carbs from CO2

and water

Contains a system of flattened memb. Sacs(thylakoids)

Thylakoids contain green pigment(chlorophyll) which absorbs light and

captures light energy for the cellGranum – stack of thylakoids

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Chloroplast

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Lysosome 

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Animal vs Plant Cells

Organelle Function Animal PlantCytoskeleton Support,

movementYes Yes,

but

Cilia/flagella Movement Yes NoCell wall Support No Yes

Plastids Photosynth

esis;storage

No Yes

Centralvacuole

Storage,support

No Yes

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Multicellular Organization

Chapter 4 Sect 3

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C l i l O i ti

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Colonial Organization

Unicellular organisms mayhave begun to live intemporary groups orcolonies

Some cells in the colonieshave specialized inperforming certainfunctions

Colonial organisms are acollection of geneticallyidentical cells that live in a

One volvox can contain

500-60,000 cells, each

which maintain their own

existence!