Ions and membranes Week 5

• For each of the following mechanisms for movement of material across the cell membrane, which of these requires a concentration gradient to occur  -

  1. simple diffusion;
  2. dissolving in the lipid portion of the membrane;
  3. carrier-mediated (facilitated) diffusion; 
  4. active transport.

  1, 2 and 3 only
• For each of the following mechanisms for movement of material across the cell membrane, which of these requires energy derived from the splitting of ATP in order to occur  -

  1. simple diffusion;
  2. dissolving in the lipid portion of the membrane;
  3. carrier-mediated (facilitated) diffusion; 
  4. active transport.

  4 only
• Which of the following graphs best describes the relationship between the rate of movement of material across a cell membrane against increasing concentration of the material occurring by carrier-mediated diffusion? (Rate of movement is shown on the vertical axis, concentration on the horizontal axis):

  Graph D

  
• Which of the following tables represents the relative concentrations of sodium ions (Na+) and potassium ions (K+) inside and outside of the cell?

  (Na+i  = sodium inside cell; Na+o = sodium outside cell; K+i = potassium inside cell; K+o = potassium outside cell).

  Table C

  
• The resting membrane potential depends mostly on the diffusion of which ions across the cell membrane?

  Potassium
• The value of the resting membrane potential of a typical nerve cell has what approximate value?

  -70mv
• Which of the following facts concerning membrane pumps are TRUE?

  1. they are proteins in the cell membrane;
  2. they posess ATP-ase activity;
  3. they can operate passively when required;
  4. they can be blocked by certain drugs;
  5. individual pumps are required to pump individual ions.

  1,2 and 4 only
• In order to enter many body cells, glucose must bind to a specific membrane transport protein which assists glucose to cross the membrane without using ATP. This type of movement is called:

  Facilitated diffusion
• Which of the following statements concerning diffusion is FALSE?

  1. Diffusion speeds up as body temperature rises
  2. A small surface area slows down the rate of diffusion
  3. A low mass particle diffuses faster than a high mass particle
  4. Diffusion moves materials from an area of low concentration ot an area of high concentration
  5. Diffusion over a greater distance takes longer than diffusion over a short distance

  4
• Ionic concentration gradients are maintained across the cell membrane because

  1. ions cannot diffuse across the membrane
  2. The cell membrane generates new ions constantly
  3. Ions are protected by being enclosed in vesicles inside and outside the cell
  4. There is no exchange of ions between extracellular and intracellular fluid
  5. Membrane pumps move different ions into and out of the cell

  5
• fill up

  A) depolarisation

  B) repolarisation

  C) rest

  D) hyperpolarisation