Chapter 6 A Tour of the Cell

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CAMPBELL AND REECE Chapter 6 A Tour of the Cell

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Chapter 6 A Tour of the Cell. Campbell and Reece. Cell Theory. All living organisms are made of cells Cells are the smallest unit of structure & function in living organisms All cells come from other cells. Microscopes. 1665: Hooke sees cell walls . Anton van Leewenhoek. - PowerPoint PPT Presentation

Transcript of Chapter 6 A Tour of the Cell

Page 1: Chapter 6 A Tour of the Cell

CAMPBELL AND REECE

Chapter 6A Tour of the Cell

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Cell Theory

All living organisms are made of cellsCells are the smallest unit of structure &

function in living organismsAll cells come from other cells

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Light Microscopy

light goes through specimen and is refracted by glass lenses so image is magnified as it is projected toward eye

magnification: ratio of image size to real size

resolution: a measure of clarity , the minimum distance 2 pts can be separated & seen as 2 pts (can’t do better than 200 nm)

contrast: accentuate pts in different parts of specimen

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Prokaryotic Cell Eukaryotic Cell

DNA concentrated in nucleoid

smallersimpler(-) internal

membranesolderasexual

reproduction

DNA in nucleuslarger more complex(+) internal

membranesasexual or sexual

reproduction

Compare & Contrast

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Cell Size Limitations

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Eukaryotic Cell Details: Plant Cell

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Nucleus

contains most of the DNA5 microns across on averageenclosed by dbl membrane: nuclear

envelope

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Chromatin

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Ribosomes

rRNA & proteinscarry out protein synthesisfree ribosomes or ribosomes embedded

in membranepolysomes: string of ribosomes

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The Endomembrane System

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Endoplasmic Reticulum

cisternae spaces contiguous with nuclear envelope

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RER

protein made for use in cytosol kept separate from those meant for export

transport vesicles carry new secretory protein/glycoprotein away from RER

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Secretory Vesicles

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SER

functions: lipid synthesismetabolism of carbohydratesdetoxification of drugs & poisonsstorage of Ca++

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SER

cells with lots SER: endocrine glands

synthesize steroid hormonesovaries, testes, adrenals

hepatocytes detoxify by adding –OH, increases solubility cleared by kidneys

alcohol, drug abusers (legal or not) have increased amts of SER in their hepatocytes (also increases drug tolerance)

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Detox by SER

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SER Stores Ca++ in Muscle Fibers

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Golgi Apparatus

receives, sorts, packages, ships also does a little modifying of proteinsextensive in cells that secrete made of flattened membranous sacs with

a curve (has directionality cis & trans)internal space = cisternae

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Lysosomes

membranous sac filled with hydrolytic enzymes

digests macromolecules use acidic pHmade in RER Golgi cytosol

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Lysosome Functions

digest food vacuoles ingested by phagocytosis in protists or by macrophages (WBCs that ingest bacteria or debris and recycle nutrients in them)

autophagy: hydrolytic enzymes in lysosomes recycle cell’s own organic material in worn out organelles

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Lysosmes

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Lysosomal Storage Diseases

autosomal recessive diseaseslack a functioning hydrolytic enzyme

whatever that enzyme would have chemically broken down builds up in lysosome (called a residual body) lysosomes fill up interferes with cell functions example: Tay Sachs disease

lipid-digesting enzyme malfunction affects neurons

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Vacuoles

are large vesicles from ER or Golgisolution inside different from cytosol due

to its selectively permeable membraneTypes:

food vacuolescontractile vacuoles

remove excess water in plant cells act like

lysosomes storage bins

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Endosymbiont Theory

early ancestor of eukaryotic cells engulfed an oxygen-using nonphotosynthetic prokaryotic cell = mitochondrion

over time prokaryotic cell became an endosymbiont (a cell living w/in another cell)

some time later some or 1 of these engulfed a photosynthetic prokaryotic cell and developed same relationship = chloroplast

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Endosymbiosis Theory

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Mitochondria

in nearly all cells, 1- 10 microns# correlates with metabolic activity of celldbl membraneinner membrane folded (cristae) & divides

mitochondria into 2 separate inner compartments (intermembrane space & matrix)

matrix contains enzymes for cellular respiration, DNA, ribosomes

intermembrane has enzymes that make ATP

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Cytoskeleton

organizes the structure & activities of a cell

3 types:1. Microtubules2. Microfilaments3. Intermediate Filaments

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Functions of the Cytoskeleton

1. mechanical support2. maintain cell shape3. provides anchor for organelles & cytosol

enzymes4. cell motility

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Cytoskeleton & Cell Motility

involves interaction between cytoskeleton & motor proteinsboth work with plasma membrane to

move cellmake flagella or cilia movemuscle fiber contractionmigration of neurotransmitter vesicles

to axon tips

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Motor Protein Animation

http://www.sinauer.com/cooper5e/animation1204.html

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Types of Cytoskeleton

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Assembly of Microfilaments

http://www.sinauer.com/cooper5e/animation1201.html

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Cell Surface Projections Formed by Cytoskeleton

http://www.sinauer.com/cooper5e/micrograph1202.html

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Microvilli

http://www.sinauer.com/cooper5e/micrograph1201.html

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Cytoskeleton Animation

http://www.bmc.med.utoronto.ca/bmc/images/stories/videos/eddy_xuan.mov

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Microtubules

in all eukaryotic cellshollow rods 25 nm across, 200 nm – 25

microns longmade from a globular protein: tubulin, a

dimer (made of 2 subunits)

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Microtubules

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Assembly of Microtubules

http://www.sinauer.com/cooper5e/animation1203.html

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Microtubule Functions

shape & support cell (compression-resistant role)

serve as tracks other organelles with motor proteins can move along

guide secretory vesicles from Golgi plasma membrane

in mitotic spindle to separate chromosomes

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in animal cells: microtubules made in centrosome

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Centrioles

pair w/in each centrosomeeach made of 9 sets of triplet

microtubulesonly in animal cells

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Micrograph of Centrioles

http://www.sinauer.com/cooper5e/micrograph1206.html

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Cilia

locomotor appendage on some cellsmove fluid over surfaceare usually many on cell surface0.25 microns across & 2 – 20 microns

longmove like oars (alternating power

/recovery strokes)generate force perpendicular to cilium’s

axis

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Cilia & Flagella Structure

locomotor appendage share common structure with cilia: 9

doublets of microtubules in ring with 2 single microtubules in center then covered with plasma membrane

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Cilia & Flagella Structure

dyneins: large motor proteins extending from one microtubule doublet to adjacent doublet

ATP hydrolysis drives changes in dynein shape so cilia or flagella bend

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Flagella & Cilia Animation

http://biology-animations.blogspot.com/2008/02/flagell-and-cilia-animation-video.html

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Microfilaments

are really actin: globular protein that links with others into chains, which twist helically around each other, forming microfilaments

in all eukaryotic cellsfunction: bears tensionmany found just inside plasma

membrane (support cell shape) which gives cytosol gel-like consistency just inside plasma membrane

make up core of microvilli

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Microfilaments

with myosin (another contractile protein) make muscle fibers contractAmoeboid movement (pseudopods)

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Intermediate Filaments

8 – 12 nm acrosstension bearingnot assembled/disassembled like

microtubules & microfilamentsmade of proteins, one is keratinline interior of nuclear envelope, axonssupport framework of cell shape

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Intermediate Filaments

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Extracellular

materials made by cell but put into extracellular space:

Cell WallExtracellular MatrixCell Junctions

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Plant Cell Walls

functions:protectionmaintains shapeprevents excessive uptake of waterDetailsexact chemical composition varies

from species to speciesall have microfibrils made of cellulose

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Plant Cell Wall Basic Design

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Plant Cell Walls

secreted by cell membraneyoung plant cell secretes primary cell

wall: thin, flexiblemiddle lamella: lies between primary

cell walls of adjacent cells made of pectin: glues adjacent cells togeher

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Plant Cell Walls

when cell stops growing either:1. secrete hardening substances into

primary wall2. secrete a secondary wall between

plasma membrane & primary cell wall has strong & durable matrix wood is mostly secondary cell wall

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Primary & Secondary Cell Walls

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Extracellular Matrix (ECM)

in animals main ingredient: glycoproteins

collagen embedded in proteoglycans (protein with many carbohydrates attached) 40% of all the protein in human body is collagen

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ECM

fibronectin: ECM glycoprotein binds to cell-surface receptor proteins called integrins

integrins: span plasma membrane transmitting signals from ECM microfilaments on inner border of plasma membrane

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ECM

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Cell Junctions

1. plasmodesmata: perforations in plant cell walls lined with plasma membrane, filled with cytoplasm

cytosol flows from cell to cell plasma membranes of adjacent

cells contiguous

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Plasmodesmata

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Cell Junctions in Animal Cells

3 main types1. Tight Junctions

plasma membranes of adjacent cells tightly pressed against each other

bound together by proteins form continuous seal around cell example: tight jcts around skin cells

make skin water proof

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Tight Junctions

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Cell Junctions in Animal Cells

2. Desmosomes function like rivets fastens cells together anchored in cytoplasm by

intermediate filamentsexample: attach muscle cells to each

other

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Desmosomes

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Cell Junctions in Animal Cells

3. Gap Junctionscytoplasmic channels from 1 cell to

anothermade of membrane proteins that

surround a pore open to ions, sugars, a.a.

necessary for communication between cells like cardiac muscle and in animal embryos

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Gap Junctions

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