Flashcards in Membranes Deck (74):
Semi-permeable layer that separates the cell from the external environment
Controls the passage of material into and out of the cell (gate keeper but does not protect)
Name the 5 components of cellular membranes.
1. phospholipid bilayer
3. integral and peripheral proteins
They form bi-layer framework
It stabilizes phospholipid fluidity
Bio-molecules found in membranes
What is glycolipid?
A complex of oligosaccharide bound to lipid used in tissue recognition
What is glycoprotein?
A complex of oligosaccharide bound to protein used in cell (“self”) recognition
Describes the membrane organization
Fluid mosaic model
Has AMPHIPATHIC properties (molecule is both polar and non-polar) which will influence what can cross the membrane
It has different effects on membrane fluidity at different temperatures
At warm temperatures, it restrains movement of phospholipids
At cool temperatures, it maintains fluidity by preventing tight packing
Proteins that are embedded within the membrane
Proteins that are temporarily bound to surface of bilayer
Membrane protein functions (6)
1. transporters: control movement of material
2. enzymes: catalyze
3. cell surface receptors: bind signal molecules
4. cell surface identity markers: ID a cell type
5. cell-to-cell adhesion proteins: bind cells
6. attachments to the cytoskeleton: structure and guide
Carrier, protein changes shape to move molecules, ATP needed (requires cellular energy)
Channel, selected ions (NA+) channels in heart, moves by diffusion (from high concentrartion to low), no energy needed
Special channel protein passively transports water
Determine shape of the cell
Anchor certain proteins to specific sites, especially on the exteriror plasma membrane in receptor-mediated endocytosis
Complex active mechanism
It is a response to a concentration gradient
Due to motion of bilayer: phospholipids slide along each other.
Associated mix of molecules: globular proteins (cholesterol and glycolipids & glycoproteins).
Name transport proteins (3)
What is passive transport?
Movement of molecules through the plasma membrane
Is energy required for passive transport?
No energy required for this type of transportation protein.
Molecules move in response to a concentration gradient (igh to low) in this type of transport protein.
What is diffusion?
Movement of molecules from high concentration to low concentration.
Permeability of the plasma membrane.
-Small, nonpolar molecules readily pass directly through the plasma membrane
-Hydrophobic interior of the plasma membrane obstruct passage of charged or polar molecules
What is a selectively permeable membrane?
Membrane proteins choose which molecules can pass through the plasma membrane
What do channel proteins permit to pass through the membrane?
Only specific solutes (water, hydrophilic solutes some ions).
How do carrier proteins do to carry a molecule to the other side of the plasma membrane?
Change their shape, binding a specific molecule to move it across the pm (i.e. glucose)
Facilitated diffusion is a type of _______ transport.
-requires no energy (is passive)
- is specific
- saturates when all carriers are occupied
Channel or carrier protein (passive)
What is osmosis?
Movement of water across selectively permeable PM from an area of high to low concentration of water.
When osmosis, through what does water move?
Low solute concentration, so high water concentration
High solute concentration, so low water concentration
Does water move towards hyper or hypo tonic?
What does isotonic mean?
Solutes concentrations are equal on both sides
Water ejected from cell through vacuoles
Keeping cells isotonic with their environment, salts balanced
What do cells use to push the cell membrane against the cell wall and keep the cell rigid (blocking entry of too much water)
The contractile vacuoles in paramecium, euglena and amoeba, pump excell water out
Rate of diffusion can be affected by____
What does carrier protein do?
What does channel protein do?
No shape change
What does active transport need asbolutely?
Does active transport require energy?
Require the use of carrier proteins.
Can move a single type of molecule
Can move two different molecules in the same direction
Can move two different molecules in opposite directions.
ATP energy is used to do what?
Change the shape of the carrier protein
How does the sodium potassium pump work?
1- Sodium gets inside the protein carrier from the inside
2-ATP phosphorylates (shape changes)
3-Sodium leaves outside the cell
4-Potassium from outside gets inside the carrier
5-Phosphate group leaves the carrier (dephosphorylates, shape changes)
6-Potassium leaves the carrier to get into the cell
A coupled transport: energy released by a molecule moving by simple diffusion is used to supply energy to actively transport a different molecule, which is moving through the membrane against a concentration gradient.
Example of cotransport
Glucose moves across the membrane against a concentration gradient
Movement of bulk substances into the cell
Movement of bulk materials out of the cell
When does endocytosis occur?
When the plasma membrane envelops food particles and/or liquids to ring then into the cell
The cell takes in particulate matter
The cell takes in only fluid
Specific molecules are taken in after thet bind to a receptor
When does exocytosis occur?
It occurs when material is discharged from the cell (such as waste).
During exocytosis, what fuses with the cell membrane and release their contents to the exterior of the cell?
What is used in plants to export cell wall material?