Sonoma State University                                                                                           Animal Physiology

Department of Biology                                                                                                February 22, 2002

EXAMINATION I

                                          Last 4 SS #_____________________________ (104 pts)

 

 

1.       List everything you know about the Na+‑K+ exchange pump. (10 pts) (1 pt each correct statement)

 

A through membrane protein

Can be limited to the serosal side of membrane

Requires Na+ on inside

Requires K+ outside

Requires ATP

Regulated by Na concentration inside cell

Causes a depolarization of a few millivolts

Blocked by Ouabain

Will not pump lithium

In all cells

Exchanges 3 Na+ for 2 K+

Pumps against concentration gradients

 

 

 

 

 

 

 

 

2.  Explain the meanings of isotonic and isosmotic. How can a solution be isosmotic, but not isotonic to another solution? (6 pts)

 

 

A solution is isotonic to a cell if when the cell is placed into the solution, it does not shrink or swell.

 

A solution is isosmotic to another solution is it has the same concentration of dissolved particles (has the same osmotic pressure)

 

The term isosmotic implies that there is a perfect semipermeable membrane and only water can pass it.  If a membrane passes some other molecule besides water it is selectively permeable.  Cell membranes pass many other chemicals and thus a cells contents may be isotonic to its surrounding solution, but not isosmotic.

 

 

 

3. Circle all of the correct answers. There may be no correct answers or all correct answers to each set. (10 pts; ½ pt each)

 

    The following is true of facilitate transport and not true of simple diffusion.

A. Facilitated transport can move materials against a concentration  gradient.

B *Facilitated transport of a specific chemical can be blocked by a competitive inhibitor.

C.* Facilitated transport involves a membrane protein

D. Facilitated transport requires ATP energy

 

     Diffusion

A. *Can take place through the lipid membrane.

B. *Can take place through protein channels.

C. *Rate is increased by increased temperature

D. Rate is increased by decreased gradient

 

     Active transport

A. *Can transport material against the concentration gradient.

B. *Can be blocked by a competitive inhibitor

C. *Has a maximum rate that can not be increased by increasing the gradient.

D. *Can be inhibited by metabolic inhibitors.

 

     A non‑competitive inhibitor

A. *Could be effective at blocking facilitated transport

B. Is one that blocks metabolic processes

C.* Is one that reacts permanently to the carrier molecule

D. *Binds with carrier molecules, but not on the active site

 

     In some cells, Ca++ is transported against its concentration gradient

A. By Cotransport

B. *By Countertransport

C. By Pinocytosis

D. By Exocytosis

 

 

 

 

 

 

 

 

 

 

  1. You have on your laboratory bench an artificial system of two aqueous saline solutions separated by a selectively permeable membrane. The solutions contain the same ions, but are different concentrations and the membrane is permeable to only one of the ions in solution. Will there be a stable electrical potential difference across the membrane? Why or why not? Does the sign of the permeant ion affect the outcome of this experiment? (5 pts)

 

Stable – yes (1 pt)

 

The permeable ion will diffuse down its concentration gradient until the force of the voltage produced is equal to the force of the diffusion gradient. (3 pt)

 

Yes, it would reverse the sign of the voltage. (1 pt)

 

 

 

 

 

 

 

 

 

 

 

 

  1. What factors determine whether a neurotransmitter depolarizes or hyperpolarizes a post-synaptic membrane? (4 pts)

 

If the gate it opens is selective for K+ or Cl-, it will hyperpolarize the cell. (2 pts)

 

If the gate is selective for Na+ or Ca++, it will depolarize the cell. (2 pts)

 

 

 

 

 

 

  1. What prevents ACh released from the presynaptic terminal from persisting and interfering with subsequent synaptic transmission? What happens if ACh remains in the synaptic cleft? (4 pts)

 

It is broken down by cholinesterase. (2 pts)

            It would continue to stimulate the receptor – at least for awhile (2 Pts)

  1. Define the following terms: (4 pts each)

 

Equilibrium potential

 

The voltage at which a particular ion will maintain its concentration difference when gates are open to it.  Or The voltage at which there is not net diffusion of an ion through open gates.

 

 

 

 

Negative feedback

 

A condition in which a perturbation is detected and corrected. or

For instance, if body temperature rises, it is detected by the body and a mechanism is employed that will reduce the temperature to a homeostatic state.

 

 

 

 

Saltatory Conduction

 

A movement of action potential from node of Ranvier to node of Ranvier where the Na+ gates are located.  Or A jumping movement.

 

 

 

 

Spatial Summation

 

An added response in a post-synaptic nerve if two or more nerves attaching to the post-synaptic nerve fire at about the same time.

 

 

 

 

Voltage

 

            A potential energy caused by unequal concentrations of electrons.

 

 

 

 

 

 

  1. Draw and label the following on a nerve cell: (10 pts)

 

Soma, dendrite, axon, bouton, node of Ranvier, Schwann cell, vesicle, microtubule, ion gate, Na+ gate

 

 

 

 

 

 

 

 

 

 

 

  1. List what you know about phospholipids (8 pts) (up to 8 pts)

 

Amphipathic

Contains glycerol

Contains 2 fatty acids

Contains a phosphate group

9 Kcal/g

mixed in water makes micells

comprises cell membranes

can be broken to make IP3 and DAG

 

 

 

 

 

 

 

 

 

 

  1. With what parts of a nerve cell do you associate the following chemicals? (10 pts)

 

Ouabain

                        Sodium-potassium pump

 

Tetrodotoxin

                        Sodium gates

 

Tetraethylammonium

                        Potassium gates

 

Bungarotoxin

                        Ach receptors or nicotinic receptors

 

Curare

                        Ach receptors or nicotinic receptors

 

 

 

  1. Describe how a Na+ gate works. (17 pts) (2 pts each up to 17 pts)

 

Depolarization causes m gate to open

Open m gate causes Na+ to enter

Open m gate causes depolarization

Open m gate from shift of one electron on protein

Depolarization causes h gate to close

Closing h gate causes repolarization

Closing h gate caused by shift of 3 electrons

Depolarization causes k+ gate to open

K+ gate opening causes hyperpolarization

M gate is positive feedback

H gate is negative feedback

Repolarization causes m gate to shut

Repolarization causes h gate to open

Blocked by TTX

Allows inward flow of Na+