Post on 04-Jan-2016
CAMPBELL AND REECE
Chapter 6A Tour of the Cell
Cell Theory
All living organisms are made of cellsCells are the smallest unit of structure &
function in living organismsAll cells come from other cells
Anton van Leewenhoek
made best lenses of his day
pond water: animalcules
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
Light Microscopy
TEM SEM
beam e- thru specimen
beam e- across surfaces
Electron Microscopy
Common to all cells
1. cytosol2. ribosomes3. DNA4. plasma membrane
Prokaryotic Cell Eukaryotic Cell
DNA concentrated in nucleoid
smallersimpler(-) internal
membranesolderasexual
reproduction
DNA in nucleuslarger more complex(+) internal
membranesasexual or sexual
reproduction
Compare & Contrast
ProkaryoticNucleoid
EukaryoticNucleus
Images
Cell Size Limitations
Eukaryotic Cell Details: Plant Cell
Nucleus
contains most of the DNA5 microns across on averageenclosed by dbl membrane: nuclear
envelope
Chromatin
Ribosomes
rRNA & proteinscarry out protein synthesisfree ribosomes or ribosomes embedded
in membranepolysomes: string of ribosomes
Ribosomes Polysomes
The Endomembrane System
includes all membranes in cellnuclear envelopeEndoplasmic reticulumGolgi apparatusvesicles, vacuoles lysosomesplasma membrane
The Endomembrane System
functions:synthesis of proteins (ribosomes in
membrane) transport of proteins into membranes
& organelles (or out of cell)movement of lipids detoxification of poisonsall membranes “related” either by
proximity or by transfer of membrane segments via vesicles
The Endomembrane System
Endoplasmic Reticulum
>50% of membrane in a cell“endoplasmic” means within the
cytoplasm“reticulum” means little netmade of network of tubules & sacs
Endoplasmic Reticulum
cisternae spaces contiguous with nuclear envelope
RER
ribosomes on outer surface of membranemost proteins made shipped out of cellas polypeptide grows (into cisternae) it
folds into its 2’ then 3’ structuremost secretory proteins are glycoproteins
so that carbohydrate attachment is done by enzymes in RER membrane
RER
protein made for use in cytosol kept separate from those meant for export
transport vesicles carry new secretory protein/glycoprotein away from RER
Secretory Vesicles
SER
functions: lipid synthesismetabolism of carbohydratesdetoxification of drugs & poisonsstorage of Ca++ (muscle fibers)
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)
Detox by SER
SER Stores Ca++ in Muscle Fibers
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
Golgi Apparatus
ER products modified on trip thru Golgicisternae membrane has unique
“team”of enzymes that moves from cis to trans
modifies the monomers in carb part of glycoproteins
modifies phospholipids destined for membrane
makes some macromolecules: polysaccharides
Golgi Apparatus Vesicles
when leave trans vesicles have molecular ID tags that indicates where they are going
vesicles have receptor proteins on external surface that “recognize” where vesicle is supposed to dock (other organelles, plasma membrane)
Lysosomes
membranous sac filled with hydrolytic enzymes
digests macromolecules use acidic pHmade in RER Golgi cytosol
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
Lysosmes
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 autosomal recessive
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
Large Central Vacuoles in Plant Cells
develops by coalescence of smaller vacuoles
solution inside it called cell sap
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
Endosymbiosis Theory
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
cristae has enzymes that make ATP
Chloroplasts
a plastiddbl membrane separates inside 2 parts3-6 micronsin green parts of plants (chlorophyll)thylakoids: inner membrane folds in disc-
shapes: 1 stack of discs = granumfluid in inner folds = stroma
Plastids
group of plant organelles other examples:1. amyloplast
colorless in roots & tubers stores starch
2. chromoplast1. pigments that give fruits & flowers
their colors
Peroxisomes
specialized metabolic compartment with 1 membrane
contain enzymes that remove H atoms from various molecules to O2 H2O2
H2O2 2 H2O by enzymes in liver peroxisomes
functions:break down fatty acids in hepatocytes detoxify alcohol,
poisons
Glyoxysomes
specialized peroxisomes in fat-storing tissues of plant seeds
contain enzymes that start catabolism of fatty acids sugars
seed uses these sugars for energy to plant
Cytoskeleton
organizes the structure & activities of a cell
3 types:1. Microtubules2. Microfilaments3. Intermediate Filaments
Functions of the Cytoskeleton
1. mechanical support2. maintain cell shape3. provides anchor for organelles & cytosol
enzymes4. cell motility
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
Motor Protein Animation
https://www.google.com/webhp?sourceid=chrome-instant&rlz=1C1WLXB_enUS512US585&ion=1&espv=2&ie=UTF-8#q=motor%20protein%20animation
Types of Cytoskeleton
Cell Surface Projections Formed by Cytoskeleton
http://www.sinauer.com/cooper5e/micrograph1202.html
Microvilli
https://www.youtube.com/watch?v=iK8MOA32vAY
Cytoskeleton Animation
http://www.bmc.med.utoronto.ca/bmc/images/stories/videos/eddy_xuan.mov
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)
Microtubules
Assembly of Microfilaments
http://sites.sinauer.com/cooper6e/animation1203.html
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
in animal cells: microtubules made in centrosome
Centrioles
pair w/in each centrosomeeach made of 9 sets of triplet
microtubulesonly in animal cells
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
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
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
Flagella & Cilia Animation
http://biology-animations.blogspot.com/2008/02/flagell-and-cilia-animation-video.html
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
Microfilaments
with myosin (another contractile protein) make muscle fibers contractAmoeboid movement (pseudopods)
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
Intermediate Filaments
Extracellular
materials made by cell but put into extracellular space:
Cell WallExtracellular MatrixCell Junctions
Plant Cell Walls
functions:protectionmaintains shapeprevents excessive uptake of waterDetailsexact chemical composition varies
from species to speciesall have microfibrils made of cellulose
Plant Cell Wall Basic Design
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 together
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
Primary & Secondary Cell Walls
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
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
ECM
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
Plasmodesmata
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
Tight Junctions
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
Desmosomes
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
Gap Junctions
Cell Animation
http://vcell.ndsu.nodak.edu/animations/flythrough/movie-flash.htm