Membrane Transport Flashcards
What is the total body water in an adult male, adult female and an infant?
- MALE - 60% body weight
-FEMALE - 50% bodyweight (lower due to higher fat percentage) - INFANT - 75% bodyweight (because more prone to dehydration)
What are the two comparments of TBW?
Intra- and extracellular compartments
Describe the three compartments within extracellular water.
- Interstitial fluid
- Plasma
- Transcellular fluid - surrounded by epithelial cells e.g synovial fluid
Why is fluid found in the bladder and GI tract not included in TBW?
Already considered out of the body
What is responsible for the electrical properties of the membrane?
Uneven distribution of ions and their movement across plasma membrane
Describe the extracellular fluid
Higher sodium and chloride ion concentration in relation to intracellular
Describe the intracellular fluid.
Higher potassium, protein and phosphate concentration in relation to extracellular fluid
Define osmosis.
Passive movement of solvent to a region of high solute concentratioon across a semipermeable membrane (impermeable to solutes)
Define osmolarity
Total concentration of dissolved particles in a litre of solution
Define osmotic pressure
Force produced due to differences in osmolarity
Define osmolality.
Total concentration of dissolved particles in a kilogram of solution
Define tonicity.
Measure of effect a solution has on cells placed on it
What is the effect of adding a solute to a compartment of water?
Reduced water concentration
Define the following terms
- Hyper-osmolar
- Hypo-osmolar
- Iso-osmolar
- HYPER-OSMOLAR - High water concentration
- (OPPOSITE FOR HYPO-OSMOLAR)
- ISO-OSMOLAR - same osmotic pressure
In what direction will water move?
HYPO-OSMOLAR TO HYPER-OSMOLAR
Define the following terms
- ISOTONIC
- HYPOTONIC
- HYPERTONIC
- ISOTONIC - same solute concentration
- HYPOTONIC - Higher solute concentration intracellularly (OPPOSITE FOR HYPERTONIC)
What are three rules regarding osmolality?
- Osmolality of ECF and ICF will be in equilibrium
- Isotonicity equivalent to normal saline
What does it mean for a membrane to be impermeable to a protein?
- Protein will not be able to cross the membrane
What is special about the charge that proteins carry?
- Negatively charged
- Greater negative charge than anions
- For example, charge by large number of chloride ions = charge by a few proteins
There is a higher chloride concentration outside the cell compared to within. What is the effect of chloride moving down its concentration gradient?
- 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
What occurs at equilibrium?
- Equilibrium potential established
- Concentration and electrical gradients in balance - no net movement of ions across membrane
Give three consequences of the Gibbs-Donnan effect.
- 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
Define passive diffusion.
Passive transport of small and nonpolar molecules across biological membrane
Define facilitated diffusion
Passive movement of molecules or ions across membrane mediated by a channel or carrier protein
Give an example of primary active transport.
- Sodium-potassium ATPase moves 3 Na+ out of cell and 2 K+ into cell using energy from ATP hydrolysis
Give two examples of secondary active transport.
- 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
Give three effects of the sodium-potassium ATPase.
- Affects transport
- Regulates cellular volume
- Maintain resting membrane potential
Define endocytosis.
Internalisation of molecules from outside of cell
Give 2 examples of endocytosis.
- PINOCYTOSIS - uptake of small soluble molecules through vesicles
- PHAGOCYTOSIS - uptake of large insoluble molecules
Define exocytosis.
- Release of molecules outside of cell e.g proteins to the plasma membrane
- 2 types - constitutive and regulated secretion
Outline the difference between constitutive and regulated secretion.
- CONSTITUTIVE - transfer of molecules from Golgi to outer surface of cell
- REGULATED - in response to specific conditions and biochemical triggers
Thinking of Fick’s law, what factors determine rate of diffusion?
- Size of difference in concentration gradient
- Thickness and permeability of membrane
- Distance of diffusion
What is the main difference between primary and secondary active transport?
- PRIMARY - direct transportation of molecules against concentration gradient
- SECONDARY - transport driven by the concentration gradient established in primary active transport
