Chapter 12 Flashcards
Recall why water-soluble molecules and ions have difficulty crossing an artificial lipid bilayer.
because its a hydrophibic environment
Review the properties that govern the rate at which a given solute can cross a protein-free lipid bilayer.
Simple Diffusion(no-energy required, crosses slowly)
Facilitated Transport
Active transport
Distinguish between simple diffusion and facilitated transpor
Simple diffusion is slow crossing
Facilitated transport: crossing is accelerated by special transport membrane proteins
Explain why the concentration of ions in the cell differs from that outside the cell.
lipid bilayer are impermeable to inorganic ions
Compare how transporters and channels discriminate among solutes, moving only a select subset across the membrane.
Transporters: has to fit into specific binding sites on the protein
Channels: has to be of a certain size or charge
Distinguish between active and passive transport, and indicate which type of membrane transport protein carries out each.
Passive transport:
No energy required
If there a solute is at a higher concentration outside of the cell than inside it will move through a concentration gradient
Membrane transport protein
Active transport:
Energy required
Moves solute against its concentration gradient
Carried out by special types of transporters called pumps
Review the forces that govern the passive transport of charged and uncharged solutes across a cell membrane.
Charged(inorganic or organic): Depends on voltage, membrane potential tend to pull positively charged solutes into the cell and drive negatively charged ones out
Uncharged: direction of passive transport is determined by concentration gradient
Electrochemical gradient: Combination of concentration gradient and membrane potential. Determines the direction in which each solute will follow across the membrane by passive transport
Describe the ways in which water can move across cell membranes, and articulate what governs whether water will enter or exit a cell.
Can diffuse slowly across or through an aquaporins
Osmosis is what governs whether water will enter or exit the c
Contrast how plant cells, animal cells, and protozoa maintain their osmotic equilibrium.
For animals: a gel like cytoplasm absorb water resists swelling
For protozoa: eliminate excess water using con
Plants: Cell wall and vacuole storage
eview how the sodium pump in animal cells uses the energy supplied by ATP hydrolysis to maintain the concentration gradients of sodium and potassium ions.
Energy form ATP hydrolysis fuels a stepwise series of protein conformational changes that drives the exchange of Na+ and K+ ions
ATP hydrolysis transport Na+ out of the cell as it carries K+
The transport of Na+ ions out and K+ ions in takes place in a cycle where each step depends on the step before. If something happens that prevents one step, the entire cycle comes to a halt.
Differentiate between the following gradient driven pumps: symport and antiport. Contrast to the uniport transporter.
Uniport: Only takes one type of solute across the membrane down its concentration gradient.
Symport: Pump moves two different solutes in the same direction across the membrane(“I’ll cross if he comes with me”)
Antiport: A pump that moves two different solutes in opposite directions(“I’ll leave if he crosses”
Recall that ion channels can be gated by different stimuli
Voltage-gated channel:
Probability of it being opened is controlled by the membrane potential
Ligand-gated channel:
Opening is controlled by the binding of some molecule(a ligand) to the channel
Mechanically-gated channel:
Opening is controlled by a mechanical force applied to the channel
Define “resting membrane potential.”
When the membrane potential is in such a steady-state condition, which means the flow of positive and negative ions across the plasma membrane is precisely balanced
Outline how membrane depolarization triggers an action potential and how the action potential spreads along the membrane.
membrane potential shifts to less neg. if this is large enough will cause opening na channels, influx causes more channels to open causing explosive amplifying entry continues till 40 mV
Compare the roles that Na+-gated and K+-gated ion channels play in an action potential.
Na+ causes inflow of na+ leading to deplolarization
K+ causes outflow of K+ leading to repolarization(doesn’t open as promplty)
Recall how potassium leak channels participate in establishing the cell’s resting membrane potential.
When leak channel open, K leaves and cause unbalanced negative charges
Review the anatomy of a nerve cell and discuss the direction in which electrical signals travel from one neuron to another.
Dendrites recieve signals and flows to axon to nerve terminals
Review how an electrical signal is converted to a chemical signal at a nerve terminal.
neurotransmitter stored in synaptic vesicle at nerve terminal depolarization of plasma membrane around this region causes ca2+ voltage gated channels to open and triggers release of neurotransmitter that’s secreted into synaptic cleft
