Active transport of substances through membranes. Primary and secondary active transport.

Question 1

primary active transport points

Answer 1

key features
mechanism
factors
examples

Question 2

primary active transport - key features list

Answer 2

1 - energy supply
2 - transport proteins
3 - against gradient

Question 3

primary active transport - key feature 1

Answer 3

energy supply

relies on ATP which is hydrolyses by ATPase

to move substances from low conc to high conc

Question 4

primary active transport - key feature 2

Answer 4

transporter proteins

relies on transporter proteins called carrier proteins or pumps

these carrier proteins undergo conformational changes to move transported substance to other side

Question 5

primary active transport - key feature 3

Answer 5

against gradient

movement of transported substances happens AGAINST conc/ electrochemical gradient as it is low to high conc

Question 6

primary active transport - mechanism

Answer 6

1 - binding
- cell membrane binds to transported substances via carrier protein

2 - conformational changes
- protein undergoes conformational changes to release transported substance to other side
- this is achieved by ATP hydrolysing by ATP-ase

3 - relocation
- protein takes transported molecule to other side of membrane

4 - release
- protein releases transported molecules

5 - reformation
- proteins reforms back to original shape/ location

Question 7

primary active transport - factors list

Answer 7

atp availability
ion concentration gradient
temperature
pH
inhibitors
genetic factors

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Question 8

primary active transport - factor 1

Answer 8

atp availability

there must be sufficient levels of ATP for PAT to occur as it is an ATP-dependent process

Question 9

primary active transport - factor 2

Answer 9

ion concentration gradient

greater differences between area 1 and area 2
= more carrier protein activity
= more rate of PAT

Question 10

primary active transport - factor 3

Answer 10

ATPase enzyme requires optimal pH 7 to prevent denaturation of carrier protein amino acid residues

Question 11

primary active transport - factor 4

Answer 11

genetic mutations

genetic mutations lead to lack of protein expression in carrier proteins

no carrier protein = no PAT

Question 12

primary active transport - factor 5

Answer 12

inhibitors

presence of inhibitors inhibit carrier protein action

e.g. oubain inhibit Na+/K+ ATPase activity

Question 13

primary active transport - factor 6

Answer 13

temperature

higher temperature = higher rate of KE of molecules/ higher rate of enzymic activity = greater rate of PAT

Question 14

primary active transport - examples list

Answer 14

sodium-potassium pump
calcium pump
proton pump

Question 15

primary active transport - example 1

Answer 15

sodium-potassium pump

function- x3 Na+ out/ x2 K+ in

location - plasmamembrane of animal cells

importance - maintain electrochemical gradient in muscle contraction/ nerve impulse transmission

Question 16

primary active transport - example 2

Answer 16

calcium pump

function - pump Ca2+ out of cytoplasm into ECM or SER

location - plasmamembrane or SER

importance - excitation-coupling mechanism for muscle contraction

Question 17

primary active transport - example 3

Answer 17

proton pump

function - exchanges H+ with K+

location - gastric epithelial cells

importance - maintain acidic pH of gaster to kill pathogens

Question 18

secondary active transport - points

Answer 18

key features
mechanism
factors
example

Question 19

secondary active transport - key features list

Answer 19

energy supply
transported protein
types

Question 20

secondary active transport - key feature 1

Answer 20

energy supply

• uses ATP energy generated by PAT
• stored in electrochemical gradient of transported substances

so indirectly uses ATP

Question 21

secondary active transport - key feature 2

Answer 21

transporter protein

uses specific transmembrane proteins called co-transporters

Question 22

secondary active transport - key feature 3

Answer 22

types

symport = same direction of cell membrane
antiport = different direction of cell membrane

Question 23

secondary active transport - mechanism

Answer 23

1 - driving force = electrochemical gradient generated by PAT

2 - proteins undergo conformational changes by using energy ATP

3 - release of energy triggers another process

Question 24

secondary active transport - factors list

Answer 24

electrochemical gradient

cotransporter specificity

hormonal modulation

Question 25

secondary active transport - factor 1

Answer 25

electrochemical gradient

steeper gradient = more energy available

Question 26

secondary active transport - factor 2

Answer 26

cotransporter specificity

greater specificity between cotransporter and transported substance = more efficient transport

Question 27

secondary active transport - factor 3

Answer 27

hormonal modulation

SAT influenced by hormones like insulin which affect cotransporter activity

Question 28

secondary active transport - examples list

Answer 28

sodium-glucose cotransporter
sodim-calcium cotransporer

chloride bicarbonate exchanger

Question 29

secondary active transport - example 1

Answer 29

sodium-glucose cotransport

function - transports glucose INTO cell by the action of sodium moving down its electrochemical gradient

location - SGLT 1 - small intestine / SGLT 2 - proximal renal tubules

importance - nutrient uptake and maintaining blood glucose levels.

Question 30

secondary active transport - example 2

Answer 30

sodium-calcium contransport

function - transports calcium OUT of cell by the action of sodium moving down its electrochemical gradient

location - cardiac/ smooth muscle cells + neurones

importance - muscle contraction / neuronal action

Question 31

secondary active transport - example 3

Answer 31

chloride-bicarbonate exchanger

function - exchanges HCO3- with Cl-

location - RBC AEL1 base 3 protein

importance - maintain acid-base balance in RBCs