Exchange Of Substances Flashcards
Explain why betalain molecules cannot move through intact cell membranes (3)
- Betalain molecules are too large
- there are no carrier proteins for betalain molecules
- betalain molecules are polar and cannot move through fatty acid tails
Explain how the blood-gas barrier of the chicken is adapted to give more efficient gas exchange than the blood-gas barrier of the dog (3)
- thinner blood-gas barrier
- therefore reduced diffusion distance
-> faster rate of diffusion
Compare and contrast diffusion and active transport (3)
- similarities:
• both move molecules through phospholipid bilateral
• in both, molecules can move through proteins - differences:
• diffusion occurs down conc gradient
AT occurs against conc gradient
•
Compare and contrast endocytosis and exocytosis (3)
Similarities:
- both processes involve vesicles
- both involve energy from ATL
Differences:
- exocytosis involves molecules leaving cell
endocytosis involves molecules entering the cell
Describe the function of carrier proteins in a cell surface membrane (5)
- involved in facilitated diffusion
- movement of molecules
- from a high conc to a low conc
- involved in active transport
Explain the differences in the uptake of substance K and substance L. (2)
- substance K is taken up by active transport because active transport goes against the concentration gradient
- substance L is taken up by diffusion until the concentration inside the cell and outside the cell are equal
Explain why the membrane is able to change its shape when cytoplasm flows towards it (2)
- the membrane is fluid
- so phospholipids and proteins can move within the membrane
Explain how the uptake of substances would be affected if the amoeba increased its number of pseudopodia (2)
- more pseudopodia increased the surface area
- therefore diffusion would be faster
