Cellular respiration - unit 3 AOS 2

Question 1

cellular respiration

Answer 1

the process by which cells create energy in the form of ATP from a series of biochemical reactions involving the breakdown of glucose.

Question 2

aerobic cellular respiration

Answer 2

Cells convert glucose into energy in the form of ATP in the presence of oxygen

Question 3

cellular respiration equation

Answer 3

C6H12O6 + 6O2 → 6H2O + 6CO2 + 30-32ATP

Question 4

the role of the mitochondria in cellular respiration

Answer 4

• the mitochondria is a double membrane bound organelle that is the site of the second and third stages of cellular respiration
• mitochondrial matrix - the space inside the inner membrane of the mitochondria which is the site of the Krebs cycle
• Cristae - the folds of the inner membrane and the site of the electron transport chain.

Question 5

stage 1: glycolysis

Answer 5

• involves the breakdown of glucose into two pyruvate molecules, creating two ATP and two NADH molecules
• the pyruvate molecules will be moves to the mitochondria at the end of glycolysis.
• occurs in the cytosol of the cell

Question 6

inputs and outputs of glycolysis

Answer 6

• inputs - glucose, 2ADP + 2Pi and 2NAD+
• outputs - 2 pyruvate, 2 ATP and 2 NADH

Question 7

stage 2: the Krebs cycle

Answer 7

• the Krebs cycle involves the production of carbon dioxide and the loading of high energy coenzymes FADH2 and NADH which can be used in the electron transport chain.
• occurs in the mitochondrial matrix

Question 8

Krebs cycle inputs and outputs

Answer 8

inputs
- 2 acetyl-CoA derived from 2 pyruvate
- 2 ADP + 2Pi
- 6 NAD+
- 2 FAD

outputs
- 4Co2 (+2 from link reaction)
- 2 ATP
- 2FADH2
- 6 NADH (+2 from link reaction)

Question 9

Krebs cycle - link reaction

Answer 9

• pyruvate produced in glycolysis is oxidised to form acetyl-CoA. This releases carbon dioxide and produces a small amount of NADH.

Question 10

stage 3: the electron transport chain

Answer 10

• electrons from the loaded coenzymes NADH and FADH2 are unloaded, crearting a proton gradient across the inner mitochondrial membrane.
• As protons are then pumped back across the membrane, it drives significant ATP production
• it occurs in the cristae or inner membrane of the mitochondria
• oxygen acts as the final electron acceptor, forming water

Question 11

electron transport chain inputs and outputs

Answer 11

inputs
- 6 O2
- 26ADP +26 pi
- 10 NADH
- 2 FADH2

outputs
- 6H20
- 26 ATP
- 10 NAD+
- 2 FAD

Question 12

enzymes in cellular respiration

Answer 12

• pyruvate kinase catalyses the final step in glycolysis producing pyruvate and ATP

Question 13

Coenzymes in cellular respiration

Answer 13

• NAD+, FAD and ADP
• these will cycle between their loaded and unloaded form, helping catalyse reactions in cellular respiration.
• unloaded in reactions that need energy and loaded in reactions that produce energy

Question 14

anaerobic fermentation

Answer 14

• a metabolic pathway involving the breakdown of glucose and ATP production in the absence of oxygen
• begins with glycolysis, producing 2 pyruvate, 2 NADH and 2 ATP
• this is followed by add on stages to regenerate NAD+
• all stages occur in the cytosol

Question 15

anaerobic fermentation in animals

Answer 15

• lactic acid fermentation involves breaking pyruvate down into lactic acid, while cycling NADH back into NAD+

Question 16

anaerobic fermentation in yeast

Answer 16

• involves converting pyruvate into carbon dioxide and ethanol, while cycling NADH back into NAD+

Question 17

enzymes in anaerobic cellular respiration (edrolo)

Question 18

factors affecting the rate of cellular respiration- temperature

Answer 18

• as temperature increases, the rate of cellular respiration will increases to a certain point
• this is because there is more kinetic energy between particles and so more collisions occur between enzymes and substrates
• above the optimal temperature, enzymes will begin to denature and cellular respiration will decrease

Question 19

factors affecting the rate of cellular respiration- oxygen

Answer 19

• as the concentration of oxygen increases, the rate of cellular respiration will increase until a certain point
• aerobic cellular respiration requires oxygen for the electron transport chain as it is the final acceptor of electrons
• the presence of oxygen encourages cells to respire aerobically
• the absence of oxygen causes cells to respire anaerobically
• its rate will eventually plateau when enzymes reach their saturation point.

Question 20

factors affecting the rate of cellular respiration- glucose concentration

Answer 20

• as glucose concentration increases, so does the rate of photosynthesis up until a certain point
• this is because glucose is an input of cellular respiration
• it will eventually plateau when enzymes reac their saturation point

Question 21

biofuel

Answer 21

• a renewable fuel source derives from biomass such as organic material including lant and animal by-products
• they are typically carbon neutral because the carbon dioxide released during combustion is taken back in by plants during photosynthesis.

Question 22

production of bioethanol

Answer 22

• sourcing and deconstruction of the biomass
• breaking down starch and cellulose into glucose molecules via enzymatic hydrolysis
• ethanol production via anaerobic fermentation
• dehydration and purification of bioethanol.

Question 23

biofuels advantages

Answer 23

• biofuels help to reduce carbon emissions and lower the greenhouse effect
• biofuels are more sustainable as they are renewable meaning they can be produced at the rate they are consumes. They reduce the reliance on fossil fuels which are non- renewable.

Question 24

biofuel disadvantages

Answer 24

• using agricultural land for biofuel production conflicts with growing food demands
• carbon emissions can still occur due to the fossil fuels used to produce bio fuels.