Membrane Transport

Question 1

What is the total body water in an adult male, adult female and an infant?

Answer 1

• MALE - 60% body weight
  -FEMALE - 50% bodyweight (lower due to higher fat percentage)
• INFANT - 75% bodyweight (because more prone to dehydration)

Question 2

What are the two comparments of TBW?

Answer 2

Intra- and extracellular compartments

Question 3

Describe the three compartments within extracellular water.

Answer 3

• Interstitial fluid
• Plasma
• Transcellular fluid - surrounded by epithelial cells e.g synovial fluid

Question 4

Why is fluid found in the bladder and GI tract not included in TBW?

Answer 4

Already considered out of the body

Question 5

What is responsible for the electrical properties of the membrane?

Answer 5

Uneven distribution of ions and their movement across plasma membrane

Question 6

Describe the extracellular fluid

Answer 6

Higher sodium and chloride ion concentration in relation to intracellular

Question 7

Describe the intracellular fluid.

Answer 7

Higher potassium, protein and phosphate concentration in relation to extracellular fluid

Question 8

Define osmosis.

Answer 8

Passive movement of solvent to a region of high solute concentratioon across a semipermeable membrane (impermeable to solutes)

Question 9

Define osmolarity

Answer 9

Total concentration of dissolved particles in a litre of solution

Question 10

Define osmotic pressure

Answer 10

Force produced due to differences in osmolarity

Question 11

Define osmolality.

Answer 11

Total concentration of dissolved particles in a kilogram of solution

Question 12

Define tonicity.

Answer 12

Measure of effect a solution has on cells placed on it

Question 13

What is the effect of adding a solute to a compartment of water?

Answer 13

Reduced water concentration

Question 14

Define the following terms
- Hyper-osmolar
- Hypo-osmolar
- Iso-osmolar

Answer 14

• HYPER-OSMOLAR - High water concentration
• (OPPOSITE FOR HYPO-OSMOLAR)
• ISO-OSMOLAR - same osmotic pressure

Question 15

In what direction will water move?

Answer 15

HYPO-OSMOLAR TO HYPER-OSMOLAR

Question 16

Define the following terms
- ISOTONIC
- HYPOTONIC
- HYPERTONIC

Answer 16

• ISOTONIC - same solute concentration
• HYPOTONIC - Higher solute concentration intracellularly (OPPOSITE FOR HYPERTONIC)

Question 17

What are three rules regarding osmolality?

Answer 17

• Osmolality of ECF and ICF will be in equilibrium
• Isotonicity equivalent to normal saline

Question 18

What does it mean for a membrane to be impermeable to a protein?

Answer 18

• Protein will not be able to cross the membrane

Question 19

What is special about the charge that proteins carry?

Answer 19

• Negatively charged
• Greater negative charge than anions
• For example, charge by large number of chloride ions = charge by a few proteins

Question 20

There is a higher chloride concentration outside the cell compared to within. What is the effect of chloride moving down its concentration gradient?

Answer 20

• Electrical potential difference across membrane
• Electrical gradient will act against concentration gradient - pull some of the chloride ions back across membrane.
• Potassium ions will move down electrical gradient - attracted by negative charge. Same process as chloride ions - continues until equilibrium reached

Question 21

What occurs at equilibrium?

Answer 21

• Equilibrium potential established
• Concentration and electrical gradients in balance - no net movement of ions across membrane

Question 22

Give three consequences of the Gibbs-Donnan effect.

Answer 22

• Small diffusible ions are not equal in the two compartments.
• The total concentration of charge equivalents is higher in intracellular spaces.
• Electrical neutrality is maintained in both compartment

Question 23

Define passive diffusion.

Answer 23

Passive transport of small and nonpolar molecules across biological membrane

Question 24

Define facilitated diffusion

Answer 24

Passive movement of molecules or ions across membrane mediated by a channel or carrier protein

Question 25

Give an example of primary active transport.

Answer 25

- Sodium-potassium ATPase moves 3 Na+ out of cell and 2 K+ into cell using energy from ATP hydrolysis

Question 26

Give two examples of secondary active transport.

Answer 26

- Co-transport - movement of molecules in same direction using symporters e.g sodium drives glucose transport against concentration gradient - Counter transport - molecules move in opposite directions using antiporters

Question 27

Give three effects of the sodium-potassium ATPase.

Answer 27

- Affects transport - Regulates cellular volume - Maintain resting membrane potential

Question 28

Define endocytosis.

Answer 28

Internalisation of molecules from outside of cell

Question 29

Give 2 examples of endocytosis.

Answer 29

- PINOCYTOSIS - uptake of small soluble molecules through vesicles - PHAGOCYTOSIS - uptake of large insoluble molecules

Question 30

Define exocytosis.

Answer 30

- Release of molecules outside of cell e.g proteins to the plasma membrane - 2 types - constitutive and regulated secretion

Question 31

Outline the difference between constitutive and regulated secretion.

Answer 31

- CONSTITUTIVE - transfer of molecules from Golgi to outer surface of cell - REGULATED - in response to specific conditions and biochemical triggers

Question 32

Thinking of Fick's law, what factors determine rate of diffusion?

Answer 32

- Size of difference in concentration gradient - Thickness and permeability of membrane - Distance of diffusion

Question 33

What is the main difference between primary and secondary active transport?

Answer 33

- PRIMARY - direct transportation of molecules against concentration gradient - SECONDARY - transport driven by the concentration gradient established in primary active transport