Download Cell Organelles

Cell Organelles
Life of a Cell
What you really need to know
Essential knowledge 4.A.2: The structure and function of
subcellular components, and their interactions, provide
essential cellular processes.
Cytosol vs Cytoplasm
• Cytoplasm= cytosol +organelles
- area outside of the nucleus
- mRNA leaves the nucleus and enters the cytosol
• Cytosol=semi-fluid substance
• Jello= cytosol
• Fruit chunks= organelles
• Jello salad (jello +fruit)=
cytoplasm
Prokaryotes
(before the nucleus)
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No membrane bound organelles
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Cell wall
•
DNA in nucleoid region (no nucleus)
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Protein synthesis on ribosomes
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Cellular respiration using plasma membrane •
VERY small cells
•
No cytoskeleton (no cytoplasmic streaming) •
Eukaryotes
(true nucleus)
Membrane bound organelles
Cell wall in plant and some fungal cells
DNA in the nucleus
Protein synthesis on ribosomes
Cellular respiration in mitochondria
Much larger than prokaryotes
Cytoskeleton
Ribosomes: protein factory of the cell
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Made of 2 subunits
– Ribosomal RNA (rRNA) and a
– Protein
Synthesized in the nucleolus
– Regions in the nucleus
Site of protein synthesis
– Translates genetic instructions from mRNA to make specific polypeptides
Bound ribosomes
– attached to the rough endoplasmic reticulum (they make it rough)
– make proteins for the endomembrane system.
– Example:
– proteins that will be embedded in the cell membrane
• Proteins that will be secreted from the cell like insulin.
•
Free ribosomes are in the cytosol
– Make proteins that function in cytosol.
• Ex: catabolic enzymes that are the first steps of glycolysis (sugar
breakdown).
• Cytoskeleton proteins
• Motor proteins
Smooth Endoplasmic Reticulum
• Main job: synthesizes lipids
– Examples:
• phospholipids for the plasma
membrane
• Steroids such as estrogen and
testosterone
– Also contains enzymes that
detoxify drugs and poisons,
especially in liver
• More drugs or alcohol leads to
more smooth ER and thus
increased tolerance and
enlarged liver.
• Often detoxifies by adding
–OH (hydroxyl groups) to make
toxins more water soluble.
Rough Endoplasmic Reticulum
• Part of endomembrane system
compartmentalizes the cell for
specialized functions (the advantage
of membranes!!)
• Synthesis of proteins
– for use in the endomembrane
system
– excreted proteins
– membrane proteins
• Example: Aquaporin, the protein
channel for water in the plasma
membrane.
• Synthesis of new membrane
(proteins included!)
• Intracellular transport of mainly
proteins via vesicles
Golgi complex (UPS)
• Synthesis and packaging of small molecules
for transport in vesicles
• Modification of molecules such as proteins
bound for membrane
• Production of lysosomes
• Synthesis of
polysaccharides
Lysosomes
• Membrane enclosed sacs
containing hydrolytic
enzymes
– intracellular digestion
– Destruction of germs
(pathogens)
– Recycling of cell’s organic
materials (dead organelles
and more)
– Programmed cell death
(apoptosis)
• Separations of fingers and toes
during human development
• Aging cells that don’t work
well any more or are
potentially cancerous
• One mechanism: when
signaled, organelles, can
release all their digestive
enzymes and essentially
“digest” the cell.
• Intracellular
digestion:
• Lysosomes
– contain digestive, or
hydrolytic enzymes,
and fuse with food
vacuoles to digest
larger organic
molecules.
• Remember – all organic
molecules break down
(catabolism) by
hydrolysis, or adding an
H2O molecule.
• Hydro = water
• Lysis = break apart
Vacuoles
• In Animals
• Food vacuoles when cells phagocytize
nutrients (endocytosis)
• In Protists
• Contractile vacuoles in fresh water
To get rid of excess water
Vacuoles in plants (or fungal cells)
– Membrane bound sac.
Membrane called the
tonoplast
• Typically large central
vacuoles in plants
– Carry out hydrolysis like
lysosomes for digestion
– Release of waste
products
– Storage of pigments
(flower color!)
– Storage of poisons
(Poison Ivy!)
– Part of cell growth by
absorption of water
– Large surface area to
volume ratio
Mitochondria
• Main job: Energy capture
and transformation
• Structure:
– Outer membrane smooth
– Inside membrane highly
convoluted forming folds
called cristae
• Increase surface area for
multiple sites for enzymes
of the electron transport
chain to make ATP
Chloroplasts
• More on these with the
photosynthesis unit but:
• Contain chlorophyll
– Green light trapping
molecules in
photosynthesis
• Double membrane
• Contain thylakoids
– membrane bound
structures in chloroplasts
• Thylakoids in stacks called
“grana”.
The Plasma Membrane
• Fluid Mosaic Model
– Phospholipid bilayer
• Hydrophilic heads,
hydrophobic tails
• Move laterally within
membrane
• Unsaturated fatty acid
keeps membrane from
freezing solid – can’t stack
tightly and stays fluid
Inner Life of a Cell Challenge!
Endomembrane system focus!
With your partner, draw the pathway! Use
arrows. Be ready to explain! (use homework,
book)
• Imagine a protein that functions in the
endoplasmic reticulum (ER), but requires
modification in the Golgi apparatus before it
can achieve its function. Describe the protein’s
path through the cell, starting with the mRNA
molecule that specifies the protein.
Inner Life of a Cell!
• Imagine a cell just underwent mitosis and is in
its growth phase. New cell membrane is
required. Describe the where it is made and
its pathway to its destination on the outer cell
membrane.
Inner Life of a Cell!
• A bacteria has been phagocytized (what is
that?). Describe what happens next.
Inner Life of a Cell!
• Imagine an enzyme that will be involved in
glycolysis (remember where does this
happen?). Describe the protein’s path through
the cell, starting with the mRNA molecule that
specifies the protein.
Inner Life of a Cell!
• Imagine an enzyme that synthesizes steroids
such as testosterone or estrogen. Trace the
path through the cell from the mRNA that
specifies the enzyme (what molecule is an
enzyme made of?).
What else besides phospholipids and
proteins?
• Cholesterol
– At moderate temps,
reduces fluidity by
reducing phospholipid
movement
– At low temps, hinders
solidification – disrupts
tight packing of
phospholipids
What else?
• Glycoproteins and Glycolipids- cell
“nametags”!
– Carbohydrates (glyco!) -short, branched, < 15
sugar units- bonded to proteins or to lipids in cell
membrane
– Cell to cell recognition
Plasma Membrane
• Embedded proteins
– Regions with hydrophilic
charged and polar side
groups and hydrophobic
nonpolar side groups
– Transport proteins
(some are channel
proteins)
• Span the membrane
• Allow passage of large
polar molecules and ions
• AQUAPORINS
– channel protein for
water
Transport summary
simple
diffusion
facilitated
diffusion
This is a:
Channel protein
special one for water
called an:
aquaporin
active
transport
Polar and larger
molecules (not
too big) and ions
such as H2O and
C6H12O6
(glucose)
Transporting
ions or
molecules
AGAINST a
gradient
ATP Small, nonpolar
molecules such as
O2, CO2, NH3 ?
How about large molecules?
• Moving large molecules (macromolecules like
proteins) into & out of cell
– through vesicles & vacuoles
– endocytosis
• phagocytosis = “cellular eating”
• pinocytosis = “cellular drinking”
– exocytosis
exocytosis
Endocytosis
phagocytosis
fuse with
lysosome for
digestion
pinocytosis
non-specific
process
receptor-mediated
endocytosis
triggered by
molecular
signal
Managing water balance
• Cell survival depends on balancing water
uptake & loss
freshwater
balanced
saltwater
How does an animal cell maintain
homeostasis in fresh water?
Paramecium contractile vacuole
Diffusion and Osmosis in a mammalian
kidney
What do mammal
kidneys need to do
that aquatic
creatures don’t?
Hold onto water!!
Diffusion and osmosis in mammalian kidneys
Blood enters under
high pressure and
filtrate leaks out of
capillary into
proximal tubule.
Filtrate includes
(needed nutrients
actively or passively
transported out of
filtrate and back to
blood ):
Water
Salts
K+
Bicarbonate (blood
buffer)
H+ ions
Urea (nitrogenous
waste)
Glucose, amino
acids
Some drugs
Urea recycled to keep high solute
concentration outside tube so water
follows. Most leaves in urine.
Antidiuretic
hormone
(ADH) acts
here in
collecting
duct.
Stimulates insertion of
aquaporins in
to plasma
membranes
for
readsorption
of water.
The Power of Water Potential
What chapters to cover
• Chapter 4 – A Tour of the Cell
– Compare and contrast prokaryotes (pro= before,
karyo = kernel, or nucleus) and eukaryotes
– Compare and contrast plant and animal cells
– Review quiz questions –some will be on test
• Chapter 5 – Membrane structure and function
• Review homework from these chapters
(vocabulary too) as well as organelle worksheet
• Diffusion and osmosis including water potential