Capillaries I Flashcards
Solute exchange
Functions of cell membranes [4 marks]
- Provide support and protection
- Cell-to-cell recognition
- Regulates entry/exit of substances to and from the cell
- Regulates cell function
What is passive transport? [2 marks]
- Movement DOWN a gradient
- Doesn’t require energy
What is active transport? [2 marks]
- Movement AGAINST a gradient
- Requires energy
What gradient does diffusion go through? [1 mark]
Concentration
What gradient does convection go through? [1 mark]
Pressure
What gradient does osmosis go through? [1 mark]
Osmotic pressure
What gradient does electrochemical flux go through? [1 mark]
Electrical & concentration
What does the concept of permeability include? [3 marks]
- Passive diffusion properties (e.g. conc, rate)
- Solute and membrane properties (e.g. Fick’s law)
- Capillaries properties
What is the formula for time taken to move a specific distance for diffusion? [4 marks]
time = (net distance)^2/2 x diffusion coefficent
What properties of the solute affect transport? [3 marks]
- Concentration gradient
- Size of solute
- Lipid solubility
What properties of the membrane affect transport? [4 marks]
- Membrane thickness/composition
- Aqueous pores
- Carriers
- Active transport mechanisms
What does Fick’s law consider? [1 mark]
Properties of solutes and membranes affecting transport
What factors determine Fick’s law? [4 marks]
- Diffusion coefficient
- Area that solute diffuses through
- Concentration gradient
- Distance between point A and B
What is the diffusion coefficient? [1 mark]
How easily a solute can move through the solvent
What are the structure of continuous capillaries? [2 marks]
- Continuous basement membrane
- Tight junctions between epithelial cells
What are the structure of fenestrated capillaries? [2 marks]
- Disruption of membrane
- Fenestrated structures
What are the structure of discontinuous capillaries? [2 marks]
- Very large fenestrated structures
- Disrupted membrane
What are structures of capillaries that can affect solute transfer? [4 marks]
- Fibrous basement membrane
- Caveolae and vesicles
- Intercellular clefts
- Glycocalyx
What is the glycocalyx? [2 marks]
- Negatively charged carbohydrates
- Dynamic barrier that covers endothelium and blocks solute permeation
What is permeability? [2 marks]
- The rate of solute transfer by diffusion across unit area of membrane per unit concentration difference
- How freely a solute crosses a membrane
How does a porous membrane interfere with diffusion of lipid insoluble solute? [3 marks]
- Reduce area for diffusion
- Increases path length through membrane
- Restricted diffusion in pore produces hydrostatic issues
What is the formula for Fick’s law? [4 marks]
Rate of solute transport = Permeability x Area available for membrane x concentration gradient
