Topic 5: Energy For Biological Processes

Question 1

Respiration

Answer 1

release of energy in the form of ATP from food, occurs in all living cells partly in the cytoplasm and partly in mitochondria

Question 2

ATP

Answer 2

hydrolysis of ATP form ADP and Pi which releases energy for movement, metabolic reactions, active transport, cell division, protein synthesis and the process generates heat

Question 3

Cristae

Answer 3

folds of inner membrane of mitochondria which increases the surface area

Question 4

Aerobic respiration

Answer 4

needs oxygen to produce carbon dioxide, water and a lot of ATP

Question 5

Glycolysis

Where does it occur
Overall
Steps (4)
Net ATP for one glucose molecule

Answer 5

Occurs in the cytoplasm

Splitting of one 6C glucose molecule into two 3C pyruvate molecules

Hydrolysis of ATP produces phosphate molecules
Glucose is phosphorylated and becomes more reactive
- (Ea is lowered) -2ATP
Phosphorylated glucose splits into two 3C glycerate 3-phosphate (GP) molecules
Two GP molecules convert into two 3C pyruvate molecules
- (+2ATP and NAD -> NADH + 3ATP) x2

Net ATP for one glucose molecule: +8

Question 6

Link reaction

Where does it occur
Steps (3)
Net ATP for one glucose molecule

Answer 6

Occurs in the mitochondrial matrix

Two pyruvate molecules are actively transported into the matrix of mitochondria
Two pyruvates combine with two co-enzyme A to form two 2C Acetyl coA molecules
Each releases one CO2 and NAD -> NADH + 3ATP

Net ATP for one glucose molecule: +6

Question 7

Krebs cycle

Where does it occur
Steps (3)
Net ATP for one glucose molecule

Answer 7

• Occurs in the mitochondrial matrix

For each molecule of 2C Acetyl coA joins with 4C oxaloacetate to form 6C citrate
6C citrate -> 5C + CO2
    - NAD -> NADH + 3ATP
    - ADP + Pi -> ATP
5C -> 4C oxaloacetate + CO2
    - 2NAD -> 2NADH + 6ATP
    - FAD -> FADH + 2ATP

• Net ATP for one glucose molecule: +24

Question 8

Total net ATP for one glucose molecule in aerobic respiration

Answer 8

8+6+24= 38

Question 9

Oxidative phosphorylation

Where does it occur
Generally wth is it
Steps (6)

Answer 9

Occurs in the inner mitochondrial membrane: cristae

Transfer of electrons along a series of electron carriers generates ATP

Reduced NAD (NADH) is oxidised to NAD and releases hydrogen ions to the electron transport chain and returns to the Krebs cycle
Electrons are carried along a chain of electron carriers in a series of redox reactions
Released energy is used to pump protons from the matrix to intermembrane by active transport, creating a diffusion gradient
Chemiosmosis: protons diffuse back into matrix via pores with protein channels and ATP synthase
Energy is released which is used for ADP + Pi -> ATP
Oxygen is the terminal electron acceptor which forms water

Question 10

Anaerobic respiration

Answer 10

partial break down of hexoses to produce a limited yield of ATP in the absence of oxygen

Question 11

What stage of respiration only occurs in anaerobic respiration

Answer 11

Glycolysis

Question 12

Anaerobic respiration in animals (4)

Answer 12

each pyruvate accepts 2H from NADH to form lactic acid + NAD
- lactic acid affects mammalian muscle contraction as it is poisonous causing acidosis which stops enzymes working
- fatigue and cramp
reversible reaction so energy from lactic acid can be retrieved when oxygen is available

Question 13

Anaerobic respiration in plants and fungi (3)

Answer 13

each pyruvate loses 1CO2 and accepts H from NADH to form ethanol + carbon dioxide + NAD
irreversible so energy from ethanol cannot be retrieved
pyruvate must accept H from NADH to regenerate NAD to be used again for glycolysis