Membranes Flashcards
Semi-permeable layer that separates the cell from the external environment
Plasma membrane
Controls the passage of material into and out of the cell (gate keeper but does not protect)
Plasma membrane
Name the 5 components of cellular membranes.
- phospholipid bilayer
- cholesterol
- integral and peripheral proteins
- glycoproteins
- glycolipids
They form bi-layer framework
Phospholipids
It stabilizes phospholipid fluidity
Cholesterol
Bio-molecules found in membranes
- Lipid
- Protein
- Glyco-molecules (carbs)
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
Phospholipid
Lipid bilayer
Plasma membrane
It has different effects on membrane fluidity at different temperatures
Cholesterol
At warm temperatures, it restrains movement of phospholipids
Cholesterol
At cool temperatures, it maintains fluidity by preventing tight packing
Cholesterol
Proteins that are embedded within the membrane
Integral Proteins
Proteins that are temporarily bound to surface of bilayer
Peripheral Proteins
Membrane protein functions (6)
- transporters: control movement of material
- enzymes: catalyze
- cell surface receptors: bind signal molecules
- cell surface identity markers: ID a cell type
- cell-to-cell adhesion proteins: bind cells
- attachments to the cytoskeleton: structure and guide
Active transport
Carrier, protein changes shape to move molecules, ATP needed (requires cellular energy)
Passive transport
Channel, selected ions (NA+) channels in heart, moves by diffusion (from high concentrartion to low), no energy needed
Special channel protein passively transports water
Aquaporin, osmosis
Determine shape of the cell
Spectrins
Anchor certain proteins to specific sites, especially on the exteriror plasma membrane in receptor-mediated endocytosis
Clathrins
Self recognition
Glycoproteins
Tissue recognition
Glycolipid
Bulk transport
Complex active mechanism
It is a response to a concentration gradient
Movement
Due to motion of bilayer: phospholipids slide along each other.
Fluid
Associated mix of molecules: globular proteins (cholesterol and glycolipids & glycoproteins).
Mosaic
Name transport proteins (3)
Carriers
Channels
Receptors
What is passive transport?
Movement of molecules through the plasma membrane
Is energy required for passive transport?
No
No energy required for this type of transportation protein.
Passive transport
Molecules move in response to a concentration gradient (igh to low) in this type of transport protein.
Passive transport
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.
Passive
- 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?
Aquaporins channels
Hypotonic
Low solute concentration, so high water concentration
Hypertonic
High solute concentration, so low water concentration
Does water move towards hyper or hypo tonic?
Hypertonic
What does isotonic mean?
Solutes concentrations are equal on both sides
Water ejected from cell through vacuoles
Extrusion
Keeping cells isotonic with their environment, salts balanced
Isosmotic regulation
What do cells use to push the cell membrane against the cell wall and keep the cell rigid (blocking entry of too much water)
Turgor pressure
The contractile vacuoles in paramecium, euglena and amoeba, pump excell water out
Extrusion
Rate of diffusion can be affected by____
Temperature, concentration
What does carrier protein do?
Shape change
What does channel protein do?
No shape change
What does active transport need asbolutely?
ATP
Does active transport require energy?
YES
Require the use of carrier proteins.
Active transport
Can saturate
Active transport
Can move a single type of molecule
Uniporters
Can move two different molecules in the same direction
Symporters
Can move two different molecules in opposite directions.
Antiporters
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.
Cotransport
Example of cotransport
Glucose moves across the membrane against a concentration gradient
Movement of bulk substances into the cell
Endocytosis
Movement of bulk materials out of the cell
Exocytosis
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
Phagocytosis
The cell takes in only fluid
Pinocytosis
Specific molecules are taken in after thet bind to a receptor
Receptor-mediated endocytosis
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?
Vesicles
What is used in plants to export cell wall material?
Bulk transport
What is used in animals to secrete hormones, neurotransmitters, digestive enzymes?
Bulk transport
