Chapter 11: Membrane Transport of Small Molecules and the Electrical Properties of Membranes

Question 1

Membrane Transport Proteins

Answer 1

Transfer solutes across cell membranes

Question 2

Transporters

Answer 2

Bind the specific solute to be transported and undergo a series of conformational changes to transfer the bound solute across the membrane

Question 3

Channels

Answer 3

Form aqueous pores that extend across the bilayer; when open they pores allow specific solutes to pass through them.

Question 4

Passive Transport

Answer 4

aka facilitated diffusion

in the case of a single uncharged molecule concentration gradient determines its direction

If the solute has a net charge the membrane potential influences gradient

Question 5

Electrochemical gradient

Answer 5

The concentration gradient and the electrical gradient form a net driving force called the electrochemical gradient.

Question 6

Active Transport

Answer 6

transport proteins that actively pump certain solutes across the membrane against their electrochemical gradients

utilizes ATP or an ion gradient

Question 7

Coupled transporters

Answer 7

Couple the uphill transport of one solute across to the downhill transport of another

Question 8

ATP driven pumps

Answer 8

couple uphill transport to the hydrolysis of ATP

Question 9

Light driven pumps

Answer 9

Couple uphill transport to an input of energy from light

Question 10

Uniporters

Answer 10

Mediates the movement of a single solute from one side to the other

Question 11

Symporters

Answer 11

Coupled transport involving the transfer of solute in the same direction

Question 12

Antiporters

Answer 12

Coupled transport involving the transfer of solute in the opposite direction

Question 13

Three types of ATP-Driven Pumps

Answer 13

1. P-Type pumps
2. F-Type pumps
3. ABC transporters

Question 14

P-type pumps

Answer 14

Phosphorylate during the pumping cycle. This class includes many of the ion pumps that are responsible for setting up and maintaining gradients of Na, K, H, Ca across the membranes

Question 15

F-type pumps

Answer 15

Found in the plasma membrane of bacteria and inner membrane of mitochondria

ATP synthatases

Question 16

ABC Transporters

Answer 16

Primarily pump small molecules across the cell membranes, in contrast to P-type and the F-type which exclusively transport ions

Question 17

Ca +2 pump

Answer 17

P-type ATPase found on the sarcoplasmic reticulum of skeletal muscle cells

Question 18

Na+-K+ pump

Answer 18

Also called the Na pump / Na K ATPase

Found in the plasma membrane of virtually all animal cells and provides the concentration of Na and K differences.

ATP driven antiporter pumping 3 Na+ out and 2 K+ in

Question 19

Electrogenic

Answer 19

A net current across a membrane creates an electrical potential with the cell being negative relative to the outside

Question 20

Ouabain

Answer 20

Inhibits the Na-K pump

Question 21

MDR protein

Answer 21

multidrug resistance protein

A ABC transporter that has the ability to pump hydrophobic drugs out of the cytosol

overexpressed in cancer cells

Question 22

Ion Channels

Answer 22

Transport inorganic ions

100 million ions can pass through one open channel each second.

Ion selective, and gated

Question 23

Name the 3 types of ion channels

Answer 23

1. Voltage gated ion channels
2. Mechanically gated ion channels
3. Ligand-gated channels

Question 24

Name the 3 types of ligand-gated channels

Answer 24

1. Transmitter-gated channel
2. Ion gated channels
3. Nucleotide-gated channels

Question 25

K+ leak channels

Answer 25

Make the plasma membrane much more permeable to K+ than to other ions, have a crucial role in maintaining the membrane potential across the plasma membrane.

When K+ leaves the interior of the cell it results in a net negative charge within the cell

Question 26

Membrane potential

Answer 26

Arises when there is a difference in the electrical charge on the two sides of a membrane, due to a slight excess of positive ions over negative ones.

Question 27

Resting membrane potential

Answer 27

The equilibrium condition in which there is no net flow of ions across the plasma membrane

Question 28

Aquaporins

Answer 28

A water channel; allows water to move readily across the membrane.

Question 29

Axon

Answer 29

Conducts signals away from the cell body toward distant targets

Question 30

Dendrites

Answer 30

Receive signals from the axons of other neurons

Question 31

Action Potential

Answer 31

A travelling wave of electrical excitation

Triggered by a depolarization of the plasma membrane

Question 32

Voltage gated cation channels

Answer 32

Responsible for generating the action potentials,

Question 33

Myelin sheath

Answer 33

An insulation that greatly increases the rate at which an axon can conduct an action potential.

Formed by specialized supporting cells called glial cells. i.e. schwann cells and oligiodendrocytes

Question 34

Saltatory condiction

Answer 34

An axon potential the propagates along a myelinated axon by jumping from node to node

tHis requires less energy and is faster

Question 35

Synapses

Answer 35

Neuronal signals are transmitted from cell to cell at synapses.

Presynaptic cell into the synaptic cleft to the postsynaptic cell

Question 36

Neurotransmitters

Answer 36

Small signal molecules that are stored in membrane enclosed synaptic vesicles.

They are either destroyed by enzymes in the synaptic cleft or taken up by the nerve terminal that released it or by glial cells.

Question 37

Transmitter-gated ion channels

Answer 37

Specialized for rapidly converting extracellular chemical signals into electrical signals at chemical synapses.

Produce local permeability changes and hence changes of membrane potential.