Chapter 4

Question 1

Simple diffusion

Answer 1

Occurs through a membrane opening or intermolecular space with no interaction of carrier proteins

Question 2

Rate of simple diffusion is dependent on:

Answer 2

Concentration, velocity of particles, number and size of openings.

Question 3

Facilitated diffusion requires:

Answer 3

interaction of a carrier protein which aids in passage by binding and shuttling of molecules through the membrane.

Question 4

Pores are composed of

Answer 4

-Integral membrane proteins that are always open.

Question 5

How do pores have selectivity to molecules

Answer 5

Through the diameter and charge of the internal pore.

-E.g. Aquaporins which allow the passgae of H2O. Not static, can open and close

Question 6

Facilitated diffusion is also called:

Answer 6

Carrier mediated diffusion.

Question 7

Rate characteristics of a facilitated diffusion:

Answer 7

• It will reach a Vmax as the protein transporters become saturated.
• Also mediated by the rate at which the transporter can change their conformation and actually perform the transport process.

Question 8

E.g. of facilitated diffusion:

Answer 8

Glucose through the GLUT4 receptor.

Question 9

E.g. of Voltage gates

Answer 9

Na+ channels which open as the charge within the membrane becomes less negative (closer to zero).

Question 10

Ligand gated channels:

Answer 10

• Chemical ligands bind the channel and cause it to open.

- E.g. are ACh channels which allow for the transmission of nerve signals.

Question 11

Nerst Equation:

Answer 11

EMF(milivolts)= +/- 61 log(Ci/Co)

Question 12

Factors affecting net diffusion rate:

Answer 12

• Concentration gradient
• Membrane potential
• Pressure gradient (blood/interstitial space)
• Osmotic force

Question 13

Primary active transport:

Answer 13

• energy from ATP hydrolysis

- mainly for Ions (Na/K/Ca/H/Cl) because they are so impermeable to the membrane and this can generate a potential

Question 14

Na/K ATPase Pump

Answer 14

• pumps 3Na out and 2K in
• This net (+) out generates an internal (-) charge as well as a concentration gradient
• Na high outside and low inside
• K high inside and low outside

Question 15

Na/K ATPase Pump affect on cell volume:

Answer 15

• without it the cells would burst

- 3 Na outside of the cell raises the osmolarity to keep the cell from swelling.

Question 16

Ca2+ Pump action:

Answer 16

• ATPase activity pumps Ca out of the cytosol to either the external environment or the sarcoplasmic reticulum.
• overall lowers the [Ca] in the cytosol

Question 17

H pump locations:

Answer 17

-Gastric glands in the stomach and kidneys

Question 18

Secondary active transport: co-transport

Answer 18

• The gradients that are generated by the ATPase activity is exploited
• E.g. is the Na+/glucose symporter which uses the Na gradient generated by Na/K ATPase activity to move glucose into the cell.

Question 19

Secondary active transport: counter-transport

Answer 19

• Movement of Na down its concentration gradient (into the cell) is couples to the movement of another molecule out of the cell
• E.g. is Na-H in the renal tubules and Na-Ca pumps

Question 20

Active transport through cellular sheets

Answer 20

• The gradient generated in the cell from movement through one side is used to couple diffusion on the other side.
• E.g. Sodium actively pumped out of the cells into the tissue while Na diffuses in on the other side with water following it (renal tubules)