Transcript Marker Proteins

CELLULAR ORGANIZATION
Organisms Are Made of Cells
• Some organisms are single-celled (unicellular)
– Ex. Bacteria, Protists (euglena, paramecium,
algae), certain types of fungus
• Some are made of many cells (multicellular)
• Everything that an organism does is ultimately
happening at the cellular level.
Some Types of Cells
A. Cells – the smallest functional unit of life
• 1. Eukaryote – organism
with a nucleus,
membrane-bound
organelles, and more
than one chromosome.
Usually either a plant or
an animal. Ex. – anything
BUT bacteria
• 2. Prokaryote – unicellular
organism with NO
nucleus, NO membranebound organelles, and
circular-stranded DNA.
Ex. – bacteria
Differences Between a Plant Cell &
Animal Cell
Plant Cell
• Has both a cell membrane
AND a cell wall
• Has a giant vacuole for
water storage and structure
• Usually a rectangular shape
• Contains chloroplasts for
photosynthesis
Animal Cell
• Has only a cell membrane
• Has several smaller vacuoles
for water, food, or waste
storage
• Can come in any shape
• No chloroplasts, only
mitochondria.
Why are most cells so small?
• Because if they were any bigger, they wouldn’t
be able to take in enough food or get rid of
enough wastes fast enough. (i.e., they would
either starve to death or drown in their own
waste)!
Cell Membrane
• Located around the cell
• Protects the cell and controls what enters or
leaves the cell
• Is selectively permeable - lets some things in but
keeps others out; essential for maintaining
homeostasis.
II. Cell Membranes
How does a substance enter a cell?
• If it’s small enough, like O2 and H2O, it can
pass directly through the phospholipid bilayer.
– This is a type of passive transport called simple
diffusion (O2) or osmosis (H2O). More about this
later!
• If the substance is too big, like C6H12O6, it
needs the help of a special protein embedded
in the phospholipid bilayer.
– This is a type of passive transport called facilitated
diffusion. More about this later!
The indirect route :
Thru cell membrane proteins
Receptor protein
Channel protein
Marker protein
Carrier
Protein
4 types of proteins:
1. Channel Proteins
2. Receptor Proteins
3. Carrier Proteins
4. Marker Proteins
Channel Proteins
• Doughnut shaped
• Allows needed molecules and ions to pass
into cell
• Type of passive transport because it requires
no energy expenditure (moves down the
concentration gradient).
• Facilitated Diffusion
Channel Proteins
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Non-polar
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* Polar
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Polar
Channel Proteins in Action!
• Large molecules like glucose (macromolecule).
Receptor Proteins
“messenger”
usually a
hormone
We have a
match!
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• When a messenger molecule binds to the receptor protein,
the protein induces the pseudopodia to engulf the two and
pull them both into the cell forming a vesicle. If the
messenger molecule doesn’t bind with the receptor
protein, it won’t let it inside of the cell.
• Receptor Mediated Endocytosis
Receptor Proteins in Action!
• Induces pseudopodia
• Forms a vesicle
• Lysosomes will dissolve the unwanted material (the
green dots).
Carrier Proteins in Action
Carrier Proteins
• Shaped like a puzzle piece.
• Work like a lock and key.
• The incoming substance (key) has to fit into the
carrier protein (lock) perfectly. If it does, it induces
the protein to change shape and allow the substance
into the cell.
• If the incoming substance doesn’t fit into the carrier
protein, it won’t be let into the cell.
• Allows needed molecules and ions to pass into cell
• Type of passive transport because it requires no
energy expenditure (moves down the concentration
gradient).
• Facilitated Diffusion
Marker Proteins
• Elongated with short chains of carbohydrates
attached
• “name tags” of the cell
• Every cell has markers that ‘say’ they belong to you
and what type of cell it is
Marker Proteins
Carbohydrate
Chain
Polar
Non-polar
Polar
Diffusion
• The movement of substances from a high
concentration to a low concentration.
• A solution reaches equilibrium when the solute is
the same on both sides of the membrane, and
moves back and forth at a constant rate.
III. Movement Across Membranes
–
Passive
Transport
• A. Simple Diffusion – molecules
that are SMALL ENOUGH to fit
through the phospholipid
bilayer move from areas of
high concentration to low
concentration. Requires no
energy input.
• B. Facilitated Diffusion – a
molecule diffuses through a
channel protein or carrier
protein. Still moving from a
high to low concentration
gradient, requiring no energy
input.
Movement Across Membranes – Active
Transport
• C. Active Transport –
uses a membrane
protein to act as a
pump to move
molecules AGAINST
the concentration
gradient from LOW to
HIGH; requires ATP
(energy).
• Your body often does
this with potassium &
sodium while you are
physically active.
Movement of H2O Across the Cell Membrane – movement of water, from a
Osmosis • Osmosis
high concentration to a low
concentration; requires no energy
input; this is how a cell maintains
homeostasis!
– 1. isotonic – the solute (salt, sugar,
etc) concentration is the same both
inside and outside the cell; a state of
equilibrium. Water moves in and
out of the cell at a constant rate.
– 2. hypertonic (more H2O) – higher
concentration of water inside the
cell, so it moves to a lower
concentration OUT of the cell;
causes the cell to shrink. If this
happens in a plant, it is called
plasmolysis.
– 3. hypotonic (less H2O) – low
concentration of water inside the
cell, so water moves INTO the cell to
even it out; causes the cell to swell
up, if it’s an animal cell, maybe even
burst! This is called cytolysis. If it’s a
plant cell, the cell wall is strong
enough to keep it from bursting.
This called turgor pressure!
Movement Across Membranes Cont’d
•
F. Endocytosis – involves the movement of large or multiple substances into
the cell; often used by white blood cells to engulf bacteria and viruses.
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1. phagocytosis – the intake of solids, “cell eating”; arms of the cell engulf the material and
bring it in.
2. pinocytosis – the intake of fluid, “cell drinking”; arms of the cell engulf the liquid and pull it
in.
3. receptor-mediated endocytosis – involves a specific receptor protein on the cell membrane
that recognizes the molecule and binds with it, allowing it access into the cell. Then, the arms
of the cell surround the material and bring it in.
Movement Across Membranes Cont’d
• Exocytosis – the movement of materials out of
the cell