Cell processes: transport across membranes

Question 1

passive transport of solutes

Answer 1

moves substances down gradient with only kinetic energy
non-mediated - no transport protein/channel (diffusion)
mediated - requires transport protein or protein channels

Question 2

non mediated transport

Answer 2

diffusion through lipid bilayer,
substances soluble in lipid bilayer
non-polar hydrophobic molecules

Question 3

ion channlels - passive mediated transport

Answer 3

*water filled pore that ions can flow through and don’t bind (still selective based on shape and/or charge allows them to harness energy stored in ion different gradients)
*gating - voltage, ligand, cell volume, phosphorylation can open/close gate
*movement through channel generates current

Question 4

carrier mediated transport

Answer 4

molecule binds to transport protein that cause conformational change so that that it can be transported across
they exhibit:
- specificity
- inhibition (something can inhibit binding)
- competition for binding site
- saturation (only so many things can be transport)

Question 5

facilitated diffusion

Answer 5

diffusion via transport proteins

Question 6

active transport of solutes

Answer 6

uses energy to drive substances against their concentration or electrochemical gradient
primary vs secondary

Question 7

primary active transport

Answer 7

energy directly derived form hydrolysis of ATP
30% of cell energy goes to primary active transport

Question 8

why difference in ion concentrations is important

Answer 8

• maintain resting membrane potential
• electron excitability (action potentials)
• contraction of muscle
• maintaining cell volume
• uptake of nutrients via secondary active transported
• pH balance

Question 9

secondary active transport

Answer 9

energy stored in ionic concentration gradient drives active transport against gradient - indirectly use ATP energy
the passive transport of one substance enables the transport of another substance against concentration gradient

Question 10

properties driving water movement across cell membranes

Answer 10

Pd
- small
- mercury insensitive
- temp dependent
Pf:
- large
- mercury sensitive
- temp independent