Download BIO201 Lecture 5

Lecture 5: January 26, 2004
Review:
Metabolism – an organisms complete set of chemical reactions
*catabolism – degradative
*anabolism - synthetic
Chemical reactions with free energy changes:
*exergonic – “energy outward”
*endergonic – “energy inward”
ATP
Enzymes speed up metabolic reactions
Physical and chemical properties
affect enzyme activity:
*Temperature
*Enzyme concentration
*pH
Control of Metabolism:
allosteric regulation
feedback inhibition
coopertivity
*activators and inhibitors
Chapter 7: A Tour of the Cell
How we study cells:
microscope – series of lenses used to magnify a specimen
*magnification – ratio of object’s image to real size
*resolving power – clarity of the image
*magnification = 1,000X
*Light microscope
*Electron microscope
*resolution = 0.1nm
Two basic types:
*Transmission (TEM)
*Scanning (SEM)
*magnification = 1,000X
*resolution = 0.2µm
*Review Table 7.1
How we study cells:
Cell fractionation:
*assay each for
composition and
function
Why are cells so small?
*exchange b/w cell
and its environment
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A view of the cell:
*All cells are membrane bound, possess ribosomes and contain DNA
plasma membrane – boundary of every cell, acts as a selective barrier
outside of cell
Hydrophilic
region
inside of cell
Hydrophobic
region
Hydrophilic
region
Red blood cell
Proteins
Phospholipid Carbohydrate
side chain
A view of the cell:
*All cells possess ribosomes
ribosomes – particles
that carry out protein
synthesis, composed
of rRNA and proteins
Large Subunit
Small Subunit
*All cells contain DNA (at some point in their life cycle)
*Two categories of cells:
prokaryotic -NO membrane enclosed nucleus
eukaryotic -membrane enclosed nucleus
nucleus – chromosome containing organelle
chromosome – gene carrying structure composed of DNA and protein
organelle – formed body w/ specialized functions
*Additional components of any cell:
cytoplasm – entire contents of the cell
cytosol – semifluid portion of the cytoplasm
A view of the prokaryotic cell:
Kingdom Monera – archaebacteria and eubacteria
alternative – Domain Archaea and Bacteria
*plasma membrane –
membrane enclosing
the cytoplasm
*ribosomes –
synthesize proteins
*nucleoid – region
containing DNA (not
membrane bound)
*cell wall – rigid
structure outside
plasma membrane
*capsule – outer coating of many bacteria
*pili –attachment structures on some bacteria
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A view of the eukaryotic cell:
Elaborately compartmentalized systems
*Generalized animal cell
*Generalized plant cell
A view of the eukaryotic cell:
nucleus – chromosome containing organelle of eukaryotic cells
nucleolus – specialized
structure of the nucleus,
site of ribosome synthesis
chromatin
nucleolus
chromatin – complex of
DNA and proteins, makes
up eukaryotic chromosome
outer membrane
inner
membrane
pore
complex
nuclear
lamina
nuclear lamina – a netlike
array of protein filaments
that maintains nuclear shape
nuclear envelope
A view of the eukaryotic cell:
ribosomes – particle composed of rRNA and proteins which carry out
protein synthesis
*free
*membrane-bound
free
endoplasmic
reticulum
bound
endomembrane system – membranes inside and around a eukaryotic
cell, related through direct contact or by transfer of membranous
vesicles
*vesicles – sac made of membrane, found within a cell
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A view of the eukaryotic cell:
endoplasmic reticulum – extensive membranous network
cisteranl space – internal compartment
cisternae – network of tubules and sacs
smooth ER – lacks ribosomes
synthesis of:
*lipids
*phospholipids
*steroids
*glycogen metabolism
*detoxification
*Ca+ 2 fluxes - signaling
rough ER – ribosomes bound to cytoplasmic
surface
synthesis of:
*secretory proteins
*membranes
A view of the eukaryotic cell:
Golgi apparatus – stacks of flat membranous sacs which modify, store
and route ER products
*manufacturing *warehousing *sorting *modifying *shipping
cisternae
trans
face
cis
face
transport
vesicle
from ER
*transport vesicle – membrane bound sac
A view of the eukaryotic cell:
Lysosome – contains hydrolytic enzymes to digest macromolecules
*all major classes of macromolecules hydrolyzed
*transport vesicle with
inactive hydrolytic enzymes
*Golgi apparatus
activates enzymes
*lysosomes bud off
Golgi membrane
*autophagy – lysosome
engulfs damaged organelle
*food vacuole fuses w/
lysosome
*enzymes digest particles
*engulfing of food particle
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A view of the eukaryotic cell:
Vacuoles – large membrane bound sacs
*Food *Contractile *Central (plants)
Paramecium - osmoregulation
Review: endomembrane system
A view of the eukaryotic cell:
Other membranous organelles:
mitochondria and chloroplasts
*possess ribosomes
*DNA
mitochondria – sites of cellular
respiration
*double membrane system
*cristae increase surface area
Family plant organelles - plastids
*amyloplasts – store starch
*chromoplasts – pigments
*chloroplasts – sites of
photosynthesis
*double membrane system
A view of the eukaryotic cell:
peroxisomes – organelle which contains enzymes that transfer H from
various substrates to O2, producing and then degrading H2O 2
*break down fatty acids for fuel in cellular respiration
*detoxification
The Cytoskeleton
cytoskeleton – network of fibers that branch through the cytoplasm
functions include:
*structural support
*cell motility
*regulation of biochemical activities
Cytoskeleton consists of:
*microtubules
*microfilaments
*intermediate filaments
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Table 7.2 The Structure and Function of the Cytoskeleton
The Cytoskeleton
Microtubules
centrosome – microtubule organizing center
centrioles – organize microtubule assembly
*Cilia and flagella –
locomotor appendages
“9 + 2”
basal body
The Cytoskeleton
dynein – motor molecules
Microfilaments
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Cell Surfaces and Junctions
Plant cells have cell walls
Extracellular matrix –
substance which animal
cells are embedded,
consisting of protein
and polysaccyarides
Integrin – membrane proteins
bound to cytoskeleton and ECM
Fibronectin – attaches the ECM
to plasma membrane
Collagen – strong fibers
embedded in ECM
Proteoglycans – complexes to form
long polysaccharide molecules
Cell Surfaces and Junctions
Intercellular junctions
Tight Junction –
fuses
membranes of
adjacent cells
Desmosomes –
fastens cells
into strong
sheets
Gap Junction –
provides channel
between adjacent
cells just large
enough for
passage of small
ions and molecules
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