Membrane Transport

Question 1

What is Osmosis?

Answer 1

It is the net diffusion of water down its own concentration gradient through a selectively permeable membrane

Question 2

What is Osmolarity?

Answer 2

Its the concentration of osmotically active particles present in a solution. That can be calculated or measured.
Units are Osmoles (Osm) of solute per litre.

Question 3

What is Tonicity?

Answer 3

Is the effect a solution has on cell volume.
Iso-, Hypo-, or Hypertonic.

Question 4

What is electrochemical gradient?

Answer 4

The net effect of simultaneous electrical and concentration gradients on this ion. Which contributes to the electrical properties of the plasma membrane

Question 5

What is facilitated diffusion?

Answer 5

Uses a carrier to facilitate the transfer pf a substance across the membrane ‘downhill’ from high to low concentration

Question 6

What is Active transport?

Answer 6

Requires the carrier to expand energy to transfer a substance ‘uphill’ against gradient.

Question 7

What is Primary Active Transport?

Answer 7

Energy is directly required to move a substance against its concentration gradient.

Question 8

What is Secondary active transport?

Answer 8

Energy is required, but it is not used directly to produce ‘uphill’ movement

Question 9

What is an example of Primary Active transport?

Answer 9

Sodium Potassium pump

Question 10

What is the vesicular transport - Exocytosis?

Answer 10

Pinching off of the membrane to engulf the substances

Question 11

What is the vesicular transport - Endocytosis?

Answer 11

A vesicle fuses with the plasma membrane releasing its contents to the Extra Cellular Fluid

Question 12

Compare transport rates between carrier-mediated transport and simple diffusion down a concentration gradient

Answer 12

As the concentration of transported molecules in the ECF increases it will eventually level off, which is the carrier-mediated transport concentration gradient (facilitated diffusion). The inital increase before it levels off is the simple diffusion down concentration gradient

Question 13

What is the type of Lipid Bilayer?

Answer 13

Asymmetry

Question 14

What is membrane fluidity determined by?

Answer 14

1. Lipid concentration
2. temperature
3. cholesterol content

Question 15

Why is Asymmetry functionally important?

Answer 15

• unequal distribution of
  specific lipids
• created by lack of flip-
  flopping
• allows the cell to have a
  different intracellular
  environment from the
  existing extracellular
  environment
• signalling proteins bind
  to head groups on
  inner side
• charge asymmetry

Question 16

How the composition of a membrane affects its properties?

Answer 16

Molecules are able to move around freely (diffuse) within each cellular compartment. However, it is more challenging for some molecules to cross membranes. This is because biological membranes have specific chemical properties, which determine when and how molecules cross the membrane.

Question 17

What is the Ficj’s Law of Diffusion?

Answer 17

𝑁𝑒𝑡 𝑟𝑎𝑡𝑒 𝑜𝑓 𝑑𝑖𝑓𝑓𝑢𝑠𝑖𝑜𝑛 (𝑄)=(Δ𝐶×𝐴×β)/√(𝑀𝑊×Δ𝑋)

Question 18

What is integral membrane proteins?

Answer 18

Have membrane spanning alpha-helices which form hydrophobic interactions with lipid tails, contain hydrophobic regions that extend into the intracellular and extracellular environments

Question 19

What is peripheral proteins?

Answer 19

they are held at the cell surface by polar or charged amino acid R-groups. they have a small number of hydrophobic interactions

Question 20

What is Diffusion in solution?

Answer 20

Occurs when particles move from an area of higher concentration to one of lower concentration until equilibrium is reached

Question 21

What is diffusion through a membrane?

Answer 21

a solute can move down a concentration gradient across a semi-permeable membrane, driven by diffusion alone in a thermodynamically favorable process, either by itself, in a process called passive diffusion, or with the assistance of a membrane protein, in a process called facilitated diffusion.