Ch.7 (Membrane Structure and Function) Flashcards
Properties of Membranes (6)
-flexibility
-self-sealing
-fluidity
-can fuse with one another, can bud off vesicles
-exhibit selective permeability
-work like capacitors: opposite charges separate and align for membrane potential
Membrane Prop1. Flexibility
membranes can take any shape as long as there is a cytoskeleton or cell wall
Membrane Prop2. Self-sealing
Phospholipids of membrane will form enclosed environment. NO OPEN ENDS
Membrane Prop3. Fluidity
there are factors that affect fluidity
Factors that affect fluidity (5)
-Temperature (higher means more liquid-y)
-Saturation of hydrophobic tails (saturated means solid, unsaturated means more liquid)
-[ONLY ANIMAL] cholesterol levels lower gelling temperature and increase melting temperature
-lateral movements of phospholipids (NO FLIPFLOP movement)
-integral membrane proteins
Membrane Prop4. fuse with each other
Endocytic vesicles arise.
Secretory vesicles fuse with PM to release contents to exterior.
Membrane Prop5. selective permeability
Easier for cells to maintain homeostasis.
Membrane Prop6. capacitors
opposite charges (ions) separate and align along membranes for membrane potential
Membrane associated proteins - integral membrane proteins
orientation of membrane associated with proteins within bilayer is asymmetric
Membrane associated proteins - integral membrane proteins - FUNCTIONS (6)
-attachement-anchoring proteins (integrin)
-transport: passive and active
-enzymes : synthesis/modifiy fatty acids and metabolic enzymes
-receptors and signal transduction: homeostasis + response to environment
-junctions [gap junctions in animal]
-recognition proteins [antigens]
Transport of small molecules across membrane (5)
sugars
ions
water
gases
aa
*NO PROTEINS. NO MACROMOLECULES.
Factors that affect transport (2)
-concentration of solutes across membrane
-nature of solutes and water (size and polarity)
Passive Transport (6)
-movement of water by osmosis occurs through aquaporins
-water moves from LOW to HIGH
-simple diffusion (HIGH TO LOW)
-facilitated diffusion (HIGH TO LOW)
-no energy required
-diffusion of solute is independent of other solutes
Aquaporins
channels which allow water to pass by osmosis (passive)
Paramecium
unicellular eukaryote (protist)
What do paramecia use to expel water? Is it passive or active?
Active.
Contractile vacuoles.
Simple Diffusion (3)
Passive.
HIGH TO LOW
movement of soluble non-polar across membrane
Facilitated Diffusion (3)
Passive.
HIGH TO LOW
movement of hydrophilic molecules via channels and transporters
Channels (4)
for ions and water
neurons - nervous impulse transmission
direction of transport determined by electrochemical potentials
rapid
Transporters (4)
for large and polar molecules : sugars and aa
muscle, fat & liver - glucose import
direction of transport determined by chemical potential
slow ; change of shape of transporter involved
Hypotonic (2)
water moves in
lower external concentration than the solute so water moves in to balance out
Isotonic (2)
equal concentrations - equilibrium
water moves in and out
Hypertonic (2)
water moves out
higher external concentration than the solute so water moves out to balance out
Which of the three solution conditions is best fit for ANIMAL cells [i.e. red blood cells] ?
Isotonic
Which of the three solution conditions is best fit for PLANT cells ?
Hypotonic (called Turgid [firm])
Hypotonic - Animal
Lysed (burst)
Hypertonic - Animal
Shriveled
Hypertonic - Plant
Plasmolyzed
Isotonic - Plant
Flaccid
Active Transport (2)
Solutes move against their gradients : LOW TO HIGH
Requires energy
What form of energy is required for active transport? (2)
ATP hydrolysis and/or equivalent
Active transport types (3)
Na+/K+ ATPase pumps
H+/ATPase pump
Electrogenic Pumps
Where are Na+/K+ ATPase pumps located?
in PM of animal cells
Where are H+/ATPase pumps? (3)
in PM of plant cells
across lysosome (animal)
vacuole (plant)
What are electrogenic pumps?
pump that creates a membrane potential or charge separation across membrane
Co-transporters (2) [active transport]
Na+/glucose (animal)
H+/sucrose (plant)
What are co-transporters also called?
Secondary active transport
Bulk transport [definition]
For in and out movement of large macromolecules like proteins in cells
Does bulk transport require energy (is it active)?
Requires energy. Active.
What is out of cell movement called? [bulk transport] (2)
Exocytosis or secretion
What is into cell movement called? [bulk transport]
Endocytosis
Exocytosis (3)
uses endomembrane system
via fusion of synaptic vesicles with PM (junction of neurons)
via fusion of secretory vesicles containing waste with PM (lysosomes, vacuoles)
What is the trajectory using the edomembrane system in exocytosis?
RER –> Golgi –> secretory vesicle –> PM
Endocytosis (3)
phagocytosis
pinocytosis
receptor-mediated endocytosis
Phagocytosis (3)
cell eating
ingestion of large food particles or bacteria
involves pseudopod formation by specialized cells (macrophages or immune cells)
Pinocytosis (3)
cell drinking
drinking of dissolved materials
no pseudopods but vesicles pinch off from PM fold
receptor-mediated endocytosis
uptake of cholesterol
