2.5.4 how substances cross membranes using active processes

Question 1

active transport

Answer 1

movement of substance against their concentration gradient (low to high) across cell membrane, usingATP & protein carriers

Question 2

endocytosis

Answer 2

bulk transport of molecules (too large to pass through cell membrane through channel/carrier proteins) into cell

Question 3

exocytosis

Answer 3

bulk transport of proteins out of cell, which are too large to pass through cell membrane via channel/carrier proteins

Question 4

energy for active transport

Answer 4

provided by hydrolysis of ATP

Question 5

describe carrier proteins

Answer 5

• membrane proteins
• have specific regions/sites which combine reversibly with certain solute molecules & ions
• have region which binds to/allows hydrolysis of ATP

Question 6

how does ATP (energy) help carrier proteins

Answer 6

helps it change its conformation, so it can carry ions/solute molecule from 1 side of the membrane to the other

Question 7

describe endocytosis

Answer 7

-segment of plasma membrane surrounds & encloses particle
- brings it into cell
- enclosed in vesicle

Question 8

is ATP needed for endocytosis

Answer 8

yes
- to provide energy to form vesicles & move them, using molecular motor proteins, along cytoskeleton threads into cell interior

Question 9

pino(endo)cytosis

Answer 9

cells ingest liquids by endocytosis

Question 10

describe exocytosis

Answer 10

• large molecules exported out of cells
• vesicle containing them moved towards & fuses with plasma membrane

Question 11

is ATP needed for exocytosis

Answer 11

yes
- needed to fuse membranes together & move vesicle using molecular motor proteins along cytoskeleton threads

Question 12

describe steps of exocytosis (3)

Answer 12

1. membrane-bound vesicle, containing substance to be secreted, moved towards cell surface membrane
2. cell surface membrane & membrane of vesicle fuse
3. fused site opens, releasing contents of secretory vesicle