Lecture 17-18

Question 1

Passive Transport

Answer 1

• no energy needed

- solute travels down concentration gradient

Question 2

Active Transport

Answer 2

• coupled to ATP hydrolysis

- solute travels against concentration gradient

Question 3

What are the three modes of transport?

Answer 3

antiporter, symporter, uniporter

Question 4

Three categories of transporters

Answer 4

1. pumps: perform primary active transport
2. carriers: traverse membrane without needing extra energy
3. channels: are used in passive transport

Question 5

Primary active transport

Two types of pumps

Answer 5

P-type pumps: phosphorylate themselves

ABC transporter: ATP binding cassette

Question 6

Secondary Active Transport

Na-Glucose Cotransport

Answer 6

After primary active transport creates a gradient, a passive channel or carrier allows ions/molecules to fall back down the gradient with a high value stowaway

Question 7

Simple Diffusion

Answer 7

molecules flow down their concentration gradients

Question 8

Factors that affect diffusion rates

Answer 8

• gradient magnitude (larger=faster)
• size of the molecule (larger=slower)
• surface area:volume ratio (higher=faster)
• temperature (higher=faster)
• density of the solvent (higher=slower)
• solubility of solute (nonpolar=soluble)
• distance to destination (longer=slower)

Question 9

Facilitated Diffusion

Answer 9

Ion channels: Gated:
Voltage gated, ligand gated (either intra or extracellularly), mechanically gated
Ungated: selectivity filter

Question 10

Selectivity Filter

Answer 10

The ion in the vestibule or selectivity filter must have H-bonds that are just right, in order to move the ion along through the channel. if the bonds are too long, all sides wont connect so the ion doesn’t move. depends on size of molecule.

Question 11

Aquaporins

Answer 11

let water through but not ions

Question 12

Gap Junctions

Answer 12

Allow cytoplasm sharing but do not have a selectivity filter

Question 13

Facilitated diffusion examples

Answer 13

gap junctions and aquaporins

Question 14

Ion Channels in Human Phys

Answer 14

neuromuscular transmission:

muscle contraction

Question 15

What 5 ion channels work together to contract muscles?

Answer 15

1. depolarization opens voltage-gated Ca channels
2. exocytosed acetylcholine opens ligand-gated Na channels
3. local depolarization opens adjacent voltage-gated Na channels
4. as depol spreads, voltage-gated Ca channels open
5. coupled Ca release channels embedded in the Sarcoplasmic reticulum open