Transcript Tour of the Cell

Tour of the Cell
Types of cells
Eukaryote
animal cells
Prokaryote
bacteria cells
Eukaryote
plant cells
Cell Size
2007-2008
Limits to cell size
• Lower limit
– smallest bacteria
• mycoplasmas
• 0.1 to 1.0 micron (µm = micrometer)
– most bacteria
• 1-10 microns
• Upper limit
– eukaryotic cells
• 10-100 microns
 micron = micrometer = 1/1,000,000 meter
 diameter of human hair = ~20 microns
What limits cell size?
• Surface to volume ratio
– as cell gets bigger its volume increases (x3) faster
than its surface area (x2)
• smaller objects have greater
ratio of surface area to volume
Why is a huge
single-celled
creature not
possible?
s:v
6:1
~1:1
6:1
Limits to cell size
• Metabolic requirements set upper limit
– in large cell, cannot move material in & out of
cell fast enough to support life
aa
aa
What process is this?
CH
NH3
aa
CHO
O2
CH
aa
CO2
CHO
CO2
NH3
O2
NH3
CO2
O2
NH3
CHO
CH
O2
aa
aa
O2
CHO
CO2
CH
aa
What’s the solution?
How to get bigger?
• Become multicellular (cell divides)
But what challenges do you have to solve now?
CO2
CO2
aa
aa
NH3
aa
CHO
CO2
NH3
CHO
CH
O2
aa
O2
aa
NH3
CO2
CO2
NH3
NH3
CO2
CH
CO2
NH3
CO2
NH3
O2
CO2
NH3
CO2
O2
CH
NH3
CHO
CO2
aa
Cell membrane
• Exchange structure
– plasma membrane functions as selective
barrier
• allows passage of O2 & nutrients IN
• allows passage of products & wastes OUT
Phospholipid
Membrane
proteins
Cholesterol
Why organelles?
• Specialized structures
– specialized functions
mitochondria
• cilia or flagella for locomotion
• Containers
– partition cell into compartments
– create different local environments
chloroplast
• separate pH, or concentration of materials
– distinct & incompatible functions
• lysosome & its digestive enzymes
• Membranes as sites for chemical reactions
Golgi
– unique combinations of lipids & proteins
– embedded enzymes & reaction centers
• chloroplasts & mitochondria
ER
The Nucleus
• Nucleus is surrounded by the nuclear envelope
…functions in
• Chromosomes…DNA and protein called chromatin
• Nucleolus- dense structure that synthesizes
ribosomal RNA and protein
• Ribosomes – protein factories
– Free ribosomes…proteins used in the cytosol
– Bound ribosomes…proteins that will be included within
membranes, packaged into organelles, or exported from
the cell. (specialize in protein secretion)
Endomembrane System
• Related by physical continuity
– Nuclear envelope
– ER
– Golgi Apparatus
– Lysosomes
– Vacuoles
– Plasma Membrane
Endoplasmic Reticulum
• Membraneous network of tubes/channels that
connect to the nuclear membrane
1. Smooth ER: lacks ribosomes and synthesizes
lipids, metabolizes carbs, and detoxifies drugs
*produces lipids, steroids, phospholipids, and sex
hormones
Ex: Liver cells store carbs as glycogen, detoxify drugs
and poisons
Muscle cells pumps Ca ions for muscle
contraction
Endoplasmic Reticulum
2. Rough ER: ribosomes on surface,
makes secretory protein…transport vesicles
Ex: Pancreas secrete the protein insulin into blood
Glycoproteins – secretory proteins that are bonded
to carbohydrates, cell receptors
Golgi Apparatus
• Manufacturing warehouse, sorts, modifies and
ships proteins (post office).
Lysosomes
• Contains hydrolytic enzymes used to digest
macromolecules. “stomach of cell”
– Membrane provides space so digestion can
occur w/o destroying cell
Lysosomal enzymes
• Lysosomal enzymes work best at pH 5
– organelle creates custom pH
– how?
• proteins in lysosomal membrane
pump H+ ions from the cytosol
into lysosome
– why?
• enzymes are very sensitive
to pH
– why?
• enzymes are proteins —
pH affects structure
– why is this an adaptation: digestive enzymes which function
at pH different from cytosol?
• digestive enzymes won’t function well if some leak into cytosol
= don’t want to digest yourself!
But sometimes cells need to die…
• Lysosomes can be used to kill cells when they
are supposed to be destroyed
– some cells have to die for proper development in
an organism
• apoptosis
– “auto-destruct” process
– lysosomes break open & kill cell
• ex: tadpole tail gets re-absorbed
when it turns into a frog
• ex: loss of webbing between your
fingers during fetal development
• ex: self-destruct of cancerous cell
syndactyly
Fetal development
6 weeks
15 weeks
When things go wrong…
• Diseases of lysosomes are often fatal
– digestive enzyme not working in lysosome
– picks up biomolecules, but can’t digest one
• lysosomes fill up with undigested material
– grow larger & larger until disrupts cell & organ
function
• lysosomal storage diseases
– more than 40 known diseases
• Ex: Tay-Sachs build up undigested fat
in brain cells
• Ex: Pompe’s – build up of glycogen and
destroys tissues
http://www.youtube.com/watch?v=Yhl3E0Gw
CAQ
http://www.wral.com/lifestyles/healthteam/st
ory/6803470/
http://www.mypompestory.com/
Vacuoles/Vesicles
• Membrane bound sacs
– 1. Food vacuoles…phagocytosis, carry food to be
digested
– 2. Contractile vacuoles…pump excess water out of
cell http://www.linkpublishing.com/video-transport.htm#Blood_-_Hypertonic_Solution
Phagocytosis, and contractile
– 3. Central vacuole…plants, contains cell sap
Membraneous Organelles
• 1. Mitochondria – site of cell respiration
…make ATP “power house”
• 2. Chloroplasts – site of photosynthesis
…make chem food from CO2, H2O and sun.
Both contain DNA, ribosomes and
synthesize their own proteins
Both have double membranes
Both transform energy ….generate ATP
Membrane-bound Enzymes
glucose + oxygen  carbon + water + energy
dioxide
C6H12O6 +
6O2
 6CO2 + 6H2O + ATP
Membrane-bound Enzymes
carbon + water + energy  glucose + oxygen
dioxide
6CO2
+ 6H2O + light

energy
C6H12O6
+ 6O2
Peroxisome
• Single membrane contains enzymes that
produce and convert H2O2 to H2O
– Liver contains peroxisomes
• Do not bud from the endomembrane system
• Grow from taking proteins and lipids made in the
cytosol
• Contain oxidative enzymes
Cytoskeleton
• Provides structural support and shape, cell
motility and regulation of biochem rxns
– 1. Microtubules
– 2. Microfilaments
– 3. Intermediate filaments
 actin
 microtubule
 nuclei
Microtubules
• Thick, straight hollow rods, constructed of α-tubulin
and β tubulin dimers
– Shape and support cell, serve as tracks
– Guide secretory vesicles
– Separate chromosome
Microtubule
Centrosome/Centrioles
• 9 sets of 3 microtubules in a ring
• In animal cells
• Cell division….guide chromosomes
– Fig 7.22
Cilia and Flagella
• Locomotive appendages
– Cilia – many short extensions, wavelike motion
– Flagella – longer, fewer, undulating motion
• Made up of microtubules 9 sets of 2 (p122 Fig 7.24)
• Anchored to cell body by basal body
• Dynein arms that extend from one set of microtubules
to the next….bending motion
“dynein walking”
LE 6-24
0.1 µm
Cross-linking
proteins inside
outer doublets
Microtubules
Plasma
membrane
Basal body
0.5 µm
Outer microtubule
doublet
Dynein arms
Central
microtubule
Radial
spoke
0.1 µm
Triplet
Cross section of basal body
Plasma
membrane
How dynein “walking” moves flagella and cilia:
– Dynein arms alternately grab, move, and release the
outer microtubules
– Protein cross-links limit sliding
– Forces exerted by dynein arms cause doublets to
curve, bending the cilium or flagellum
LE 6-25a
Microtubule
doublets
Dynein arm
Dynein “walking”
ATP
LE 6-25b
Cross-linking
proteins inside
outer doublets
ATP
Anchorage
in cell
Effect of cross-linking proteins
Wavelike motion
Microfilaments
• Solid twisted double chain of actin filaments
– Bears tension
– Helps support cell shape
– Make up microvilli
– Cell motility (muscle, white blood cells)
– Contraction of cells
LE 6-27a
Muscle cell
Actin filament
Myosin filament
Myosin arm
Myosin motors in muscle cell contraction
Amoeba movement
• Pseudopodia (cellular extensions) extend and
contract through the reversible assembly and
contraction of actin subunits into microfilaments
LE 6-27b
http://www.biophysik.unibremen.de/radmacher/animations/amoeba.ht
ml
Cortex (outer cytoplasm):
gel with actin network
Inner cytoplasm: sol
with actin subunits
Extending
pseudopodium
Amoeboid movement
http://200.93.199.34/areas_academicas/biology/
multimedia/animaciones/amoeboid_motion.swf
Cytoplasmic Streaming
• Cytoplasmic streaming is a circular flow of cytoplasm
within cells
• This streaming speeds distribution of materials
within the cell
• In plant cells, actin-myosin interactions and sol-gel
transformations drive cytoplasmic streaming
http://highered.mcgrawhill.com/sites/9834092339/student_view0/chapter4/animation__cytoplasmic_streaming.html
LE 6-27c
Nonmoving
cytoplasm (gel)
Chloroplast
Streaming
cytoplasm
(sol)
Vacuole
Parallel actin
filaments
Cytoplasmic streaming in plant cells
Cell wall
Microfilaments
Intermediate Filaments
• Constructed from keratins, more permanent,
smaller than microtubules but bigger than
microfilaments
– Reinforce shape of cell
– Fix positions of organelles
– Make up nuclear lamina…lines nuclear membrane
Extracellular Structures
• Most cells synthesize and secrete materials that are
external to the plasma membrane
• These extracellular structures include:
– Cell walls of plants
– The extracellular matrix (ECM) of animal cells
– Intercellular junctions
Cell Wall
• Protects, maintains shape, prevents water
uptake, provides support
• Layers of Cell Wall:
– Primary cell wall: thin and flexible
– Middle lamella: thin layer between primary walls of
adjacent cells, rich in pectins (sticky polysaccharide)
– Secondary cell wall (in some cells): added between
the plasma membrane and the primary cell wall
• Plasmodesmata are channels between adjacent plant
cells
LE 6-28
Central
vacuole
of cell
Plasma
membrane
Secondary
cell wall
Primary
cell wall
Central
vacuole
of cell
Middle
lamella
1 µm
Central vacuole
Cytosol
Plasma membrane
Plant cell walls
Plasmodesmata
Extracellular Matrix (animal cells)
• The ECM is made up of glycoproteins and
other macromolecules
• Functions of the ECM:
– Support
– Adhesion
– Movement
– Regulation
Collagen
fiber
EXTRACELLULAR FLUID
Proteoglycan
complex
Fibronectin
Plasma
membrane
Integrin
CYTOPLASM
Microfilaments
Glycoproteins- proteins w/carbs
1. Collagen- strong fibers outside cell
2. Proteoglycans – woven network of carbs
3. Fibronectins- bind to integrin receptors built into cell membrane
(bind to microfilaments)
Intracellular Junctions
• Neighboring cells in tissues, organs, or organ
systems often adhere, interact, and
communicate through direct physical contact
• Intercellular junctions facilitate this contact
Plasmodesmata…Plant junctions
• Plasmodesmata are channels that perforate plant cell
walls
• Through plasmodesmata, water and small solutes
(and sometimes proteins and RNA) can pass from cell
to cell
Cell walls
Interior
of cell
Interior
of cell
0.5 µm
Plasmodesmata
Plasma membranes
Animal Intracellular Junctions
• At tight junctions, membranes of neighboring
cells are pressed together, preventing leakage
of extracellular fluid …ex intestines
• Desmosomes (anchoring junctions) fasten
cells together into strong sheets …ex. skin
• Gap junctions (communicating junctions)
provide cytoplasmic channels between
adjacent cells …ex. heart
Tight junction
Tight junctions prevent
fluid from moving
across a layer of cells
0.5 µm
Tight junction
Intermediate
filaments
Desmosome
1 µm
Space
between
cells
Gap
junctions
Plasma membranes
of adjacent cells
Gap junction
Extracellular
matrix
0.1 µm
Cells gotta live!
• What jobs do cells have to do?
– building proteins
• proteins control
every cell function
– make energy
• for daily life
• for growth
– build more cells
• growth
• reproduction
• repair
Why study protein production?
proteins
cells
DNA
Repeat after me…
organism
DNA gets the glory, but
Proteins do all the work!
Building Proteins
• Organelles involved
– nucleus
– ribosomes
– endoplasmic reticulum
(ER)
– Golgi apparatus
– vesicles
The Protein Assembly Line
nucleus
ribosome
ER
Golgi
apparatus
vesicles
TO:
endoplasmic
reticulum
nucleus
protein
on its way!
DNA
RNA
TO:
vesicle
TO:
TO:
vesicle
ribosomes
TO:
finished
protein
protein
Making Proteins
Golgi
apparatus
Making proteins
Putting it together…
nucleus
nuclear pore
cell
membrane
protein secreted
rough ER
ribosome
vesicle
proteins
smooth ER
transport
vesicle
cytoplasm
Golgi
apparatus
Cells gotta live!
• What jobs do cells have to do?
– make proteins
• proteins control
every cell function
– make energy
• for daily life
• for growth
– build more cells
• growth
• reproduction
• repair
ATP
Cells need power!
• Making energy
– take in food & digest it
– take in oxygen (O2)
– make ATP
– remove waste
ATP
• http://www.khanacademy.org/video/parts-ofa-cell?playlist=Biology
From food to making Energy
• Cells must convert incoming energy to forms
that they can use for work
– mitochondria:
from glucose to ATP
– chloroplasts:
from sunlight to ATP & carbohydrates
• ATP = immediate energy
• carbohydrates = stored energy
ATP
+
ATP
Evolution of Organelles Animation
http://www.sumanasinc.com/webcontent/animations/content/or
ganelles.html
Mitochondria are everywhere!!
animal cells
plant cells
Cells gotta live!
• What jobs do cells have to do?
– building proteins
• proteins control
every cell function
– make energy
• for daily life
• for growth
– build more cells
• growth
• reproduction
• repair
Any Questions??
2007-2008