module 2 - 5.4 active transport

Question 1

what does diffusion lead to?

Answer 1

equilibrium of concentrations

Question 2

how do you maintain a concentration gradient?

Answer 2

molecules must be moved UP the conc. gradient at a rate faster than they diffuse DOWN the conc. gradient

Question 3

what is active transport?

Answer 3

movement of molecules or ions across a cell membrane from lower to higher conc. AGAINST/ UP conc. gradient

Question 4

is active transport selective or non selective?

Answer 4

selective - specific shape of pore

Question 5

what does ‘pump’ mean?

Answer 5

that what’s happening is always an active process

Question 6

what happens if substrate molecules are moving from lower to higher concentration? (active transport)

Answer 6

• specific transmembrane proteins are required
• these proteins have receptor sites that bind to specific molecules and transport them across cell membrane
• energy for this supplied by ATP

Question 7

where does active transport often take place?

Answer 7

internal lining of small intestine

Question 8

which proteins does active transport use?

Answer 8

carrier proteins

Question 9

what do plants need to absorb from the soil, and where do these things exist?

Answer 9

• absorbs mineral salts
• only exist in very dilute solutions in soil water

Question 10

what does active transport enable for the cells in the plant?

Answer 10

enables them to take up salts from dilute solution against direction of conc. gradient

Question 11

what is the possible mechanism for active transport?

Answer 11

1. molecule binds to receptor site on inner wall of the pore on the carrier protein
2. ATP cytoplasm side of carrier protein, then hydrolysed into ADP +Pi, energy is transferred, and Pi is bound, to carrier protein
3. carrier protein changes shape to open the pore to other side of membrane, molecule is released to inside of cell
   - Pi released from carrier protein, carrier protein changes shape again do adopt original shape

Question 12

what are the two types of bulk transport?

Answer 12

• endocytosis
• exocytosis

Question 13

what is endocytosis?

Answer 13

substances moving from out of the cell to in

Question 14

what processes does endocytosis involve?

Answer 14

• phagocytosis
• pinocytosis
• receptor-mediated endocytosis

Question 15

what does phagocytosis form?

Answer 15

phagosome (vacuole)

Question 16

what does pinocytosis form?

Answer 16

vesicles

Question 17

what does receptor-mediated endocytosis form?

Answer 17

coated vesicles

Question 18

what is exocytosis?

Answer 18

substances moving from in the cell to out of it
- also a mechanism where cells are able to insert membrane proteins, lipids etc. into cell membrane

Question 19

what happens during exocytosis?

Answer 19

• membrane-bound secretory vesicles are carried to plasma membrane
• vesicle contents are secreted into extracellular environment
• secretion possible because the vesicle TRANSIENTLY FUSES with plasma membrane
• vesicles containing these membrane components FULLY FUSE & become part of cell surface membrane

Question 20

what is bulk transport?

Answer 20

the movement of WHOLE cell substances, not selective

Question 21

how are vesicles attached to cytoskeleton?

Answer 21

by proteins

Question 22

what is another type of active transport?

Answer 22

bulk transport