Lecture 5

Question 1

What is Membrane Permeability?

Answer 1

The net rate of diffusion of a given substance through each unit area of the membrane for a unit [] difference on either side.

Question 2

What are the 5 factors affecting membrane permeability and why?

Answer 2

1) Membrane Thickness: Increased thickness, decreased diffusion rate

2)Lipid Solubility: Greater solubility, greater diffusion rate (hydrophobicity.. greater increased lipid solubility)

3) Number of Protein Channels: increased rate of transport with greater channel density (# channel/area)

4)Temperature: Diffusion increases in direct proportion with temperature.

5) Molecular Weight of Diffusing Substance; V = velocity of thermal motion (heavier substance will move slower)

Question 3

What is exocytosis?

Answer 3

Movement from inside to outside of cell

Question 4

What are the three functions of exocytosis?

Answer 4

1) Membrane Components
- Adds molecules from vesicle interior
- GLUT4 (monosaccharide)

2) Recycle Endocytosis Products (engulf)
- Adds to cell membrane

3) Secretion
- Interior to Exterior
- White blood cells for antibodies
- Neurons… release neurotransmitters
- Mucus…respiratory and digestive systems

Question 5

What do Junctional Folds do?

Answer 5

Increase SA (membrane tissue)

Question 6

What do vesicles house?

Answer 6

Neurotransmitters

Question 7

What is a terminal axon?

Answer 7

A motor axon of motor neuron

Question 8

What are the three types of transporters?

Answer 8

1) Uniporter
2) Symporter
3) Antiporter

Question 9

What is a uniporter?

Answer 9

Transports only 1 solute (molecule or ion)

Question 10

What is a Symporter?

Answer 10

A co-transporter - transport of 1 solute COUPLED to the transport of a SECOND solute in the same direction.

Question 11

What is a Antiporter?

Answer 11

A exchanger - Transport of 1 solute coupled to the transport of a SECOND solute… in the opposite direction.

Question 12

What is primary active transport?

Answer 12

• Harness stored chemical energy… ATP
• ATP used directly to move ions.. uphill (against a concentration gradient)
• Na+/K+ ATPase

Question 13

What is secondary active transport?

Answer 13

Uses stored chemical energy.. ATP indirectly

Harnesses stored electrochemical gradient energy.

Question 14

What is an example of an ATP pump?

Answer 14

SERCA (Sarco Endoplasmic Reticulum Ca++ ATPase

Question 15

What are P-type Pumps?

Answer 15

• Phosphorylate themselves during cycle
• Ion pumps for NA+,K+, H+, Ca2+
• Uses ATP
• Primary Active Transport

Question 16

What is the reaction that happens with a ATP driven pump?

Answer 16

ATP —-> ADP + Pi + E

Question 17

In SERCA where does the Calcium go?

Answer 17

Calcim is pumped from the Cytoplasm to the Lumen SR (it is stored in very small concentrations in cytoplasm)

Question 18

What are F-Type Pumps?

Answer 18

• Don’t spend ATP but MAKES ATP
• Turbine-like proteins.. multiple sub units
• Bacteria (plasma membrane)
• Mitochondrion (inner membrane)

Question 19

What is Membrane Potential?

Answer 19

• Refers to the Electrical energy separation difference across the cell membrane.. sets up the potential to do physical work (i.e, moving ions across the membrane).. measured in Vm (potential difference)

Question 20

What happens if the Membrane Potential is 0mV?

Answer 20

You have an equal amount of electrical charge on both sides of the membrane

Question 21

What is Equilibrium in Cell Membranes?

Answer 21

• Combination of electrical and concentration gradients coupled together
• Even balance of ions with no net movement (equal and opposite)

Question 22

What are the three key points about cell membranes?

Answer 22

1) Small changes in ion concentration induces large changes in membrane potential

2) The difference in electrical charges are close to the membrane.

3) The balance of ions is maintained by active “pumps”

Question 23

What is the three mechanisms of bioelectrical signalling?

Answer 23

1.) Gated Channels.. membrane embedded proteins

2.) Facilitated Transport..ions move through pores in proteins

3.) Proteins contain gates which exist in 2 states (opened or closed)

Question 24

What are the 3 types of ion channels?

Answer 24

1) Voltage-gated: electrical environmental determines OPEN OR CLOSED states.

2) Ligand-Gated: a ligand (molecule) binds to an ion channel which opens or closes the gate (example: neurotransmitter)

3) Mechanically-Gated: stretch receptors, requires application of force (mechanical)

Question 25

What is a Catabolic Rxn?

Answer 25

• Breaking down of structure
• Referred to as “cation”

Question 26

What does sodium have?

Answer 26

1 lone valence electron that wants to leave causing an electrical imbalance.