transport across cell membrane Exam Qs Flashcards
name and describe 5 ways substances can move across the cell surface membrane into a cell
- Simple diffusion of small non-polar molecules down a concentration gradient
- facilitated diffusion or large charged molecules down a concentration gradient via a protein channel/ carrier
- osmosis of water down a water potential gradient
- active transport against a concentration gradient via a protein carrier using ATP
- co-transport of two different substances using a carrier protein
explain function of ATP hydrolase at sodium potassium pump
catalyses ATP = ADP + Pi
releases energy which allow ions to be moved against a concentration gradient
OR allows active transport of ions
explain how movement of Na+ out of cell allows absorption of glucose into the cell lining the ileum
maintains a concentration gradient for Na+
Na+ moves in by facilitated diffusion/ cotransport, brings glucose in with it
describe 2 features expected in a cell specialised for absorption
2 of:
- folded membrane/ microvilli so large surface area
- large number of channel/ carrier proteins so fast rate of absorption/ active transport/ facilitated diffusion
- large number of mitochondria to release energy for active transport
The movement of substances across cell membranes is affected by membrane structure. Describe how.
5 of :
- phospholipid bilayer allows movement/ diffusion of non-polar and lipid soluble substances
- phospholipid bilayer prevents movement of polar/ charged, water-soluble substances
- carrier proteins allow active transport
- channel/ carrier proteins allow facilitated diffusion/ co-transport
- shape of channel or carrier determines which substances move
- number of channels/ carriers determine how much substance can move
- membrane surface area determines how much movement
- cholesterol affects fluidity/ rigidity/ permeability
2 similarities in movement of substances by diffusion and by osmosis
movement down a gradient
passive not active processes
