Key Knowledge 5

Question 1

cellular respiration 

Answer 1

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

Question 2

cellular respiration equation

Answer 2

glucose + oxygen —> carbon dioxide + water + energy

C6H12O6 + 6 O2 —> 6 CO2 + 6 H2O + 36 or 38 ATP

Question 3

Animals: lactic acid fermentation

Answer 3

Glucose —> Lactic acid + ATP

C6H12O6 2 C3H6O3 2 ATP

Question 4

Plants and yeast: alcohol fermentation

Answer 4

Glucose —> Ethanol + Carbon dioxide + ATP

C6H12O6 C2H5 H 2 CO2 2 ATP

Question 5

glycolysis 

Answer 5

the first stage of aerobic cellular respiration in which glucose is converted to two pyruvate molecules. location is in the cytosol

Question 6

Krebs cycle 

Answer 6

the second stage of aerobic cellular respiration, where multiple reactions occur to create ATP, NADH, FADH2, and the waste product CO2. Also known as the citric acid cycle or TCA cycle. The location is in the mitochondrial matrix

Question 7

electron transport chain 

Answer 7

the third stage of aerobic cellular respiration, in which a series of protein complexes embedded in the inner membrane of a mitochondrion harness the stored energy in NADH and FADH2 to generate large amounts of ATP. The location is the cristae of the mitochondria

Question 8

Mitochondria

Answer 8

crucial to aerobic cellular respiration as they are the site of the second and third stages, with the first stage (glycolysis) occurring in the cytosol of the cell.

Question 9

glycolysis inputs

Answer 9

• 1 glucose (C6H12O6)
• 2 ADP + 2 Pi
• 2 NAD+ + 2 H+

Question 10

glycolysis outputs

Answer 10

• 2 pyruvate
• 2 ATP
• 2 NADH

Question 11

krebs cycle inputs

Answer 11

• 2 acetyl-CoA (derived from 2 pyruvate)
• 2 ADP + 2 Pi
• 6 NAD + 6 H+
• 2 FAD + 4 H+

Question 12

Krebs cycle outputs

Answer 12

• 4 carbon dioxide (CO2)
• 2 ATP
• 6 NADH
• 2 FADH2

Question 13

overall results from krebs cycle

Answer 13

• By breaking down acetyl-CoA, protons and high-energy electrons are released. These protons and electrons are loaded onto NAD+ and FAD molecules to generate high-energy coenzymes NADH and FADH2.
• The Krebs cycle produces two CO2 molecules for every one acetyl-CoA molecule. When added to the single CO2 molecule produced from each of the two pyruvates undergoing the link reaction, this means a total of six CO2 molecules are produced for every original glucose molecule.
• The Krebs cycle produces a small amount of energy in the form of two ATP (one per acetyl-CoA molecule).

Question 14

ETC inputs

Answer 14

• 6 oxygen (O2) + 12 H+
• 26 or 28 ADP + Pi
• 10 NADH
• 2 FADH2

Question 15

ETC outputs

Answer 15

• 6 water (H2O)
• 26 or 28 ATP
• 10 NAD+ + 10 H+
• 2 FAD + 4 H+

Question 16

ETC steps

Answer 16

1. NADH and FADH2 unload electrons and protons at the first and second protein complexes of the electron transport chain that reside in the inner mitochondrial membrane. The following reactions take place:
   (1) NADH —> NAD+ + H+ + 2 e–
   (2) FADH2 —> FAD + 2 H+ + 2 e–.
2. The excited electrons (from NADH and FADH2) are transferred through a number of different protein complexes embedded in the electron transport chain, powering the active transport of protons (H+) from the mitochondrial matrix into the narrow intermembrane space.
3. This leads to a build-up of protons in the intermembrane space.
4. To move down their concentration gradient, these protons must travel through the specialised protein channel ATP synthase
5. This process produces large amounts of ATP, but also leads to many free protons and electrons building up in the matrix.

Question 17

Enzymes and coenzymes in cellular respiration

Answer 17

The tightly controlled sequence of biochemical reactions in cellular respiration relies heavily on the use of enzymes and coenzymes to ensure they happen at a fast rate.

Question 18

unloaded coenzymes

Answer 18

• ADP
• NAD+
• FAD

Question 19

loaded coenzymes

Answer 19

• ATP
• NADH
• FADH2

Question 20

anaerobic fermentation 

Answer 20

a metabolic pathway that occurs in the absence of oxygen. Involves glycolysis, followed by further reactions that convert pyruvate into lactic acid in animals, or ethanol and CO2 in yeasts

Question 21

lactic acid fermentation

Answer 21

the process of anaerobic fermentation in animals, where pyruvate produced via glycolysis is converted to lactic acid

Question 22

ethanol fermentation 

Answer 22

the process of anaerobic fermentation in yeasts, where pyruvate produced via glycolysis is converted to ethanol and carbon dioxide. Also known as alcohol fermentation

Question 23

temperature and pH

Answer 23

Temperature and pH have a large effect on the rate at which cellular respiration occurs due to their effect on enzymes, which are essential in cellular respiration

Question 24

glucose

Answer 24

Increasing glucose availability increases the rate of cellular respiration until the enzymes reach the saturation point.

Question 25

oxygen

Answer 25

Increasing the concentration of oxygen will increase the rate of aerobic respiration.

Question 26

Enzyme inhibition 

Answer 26

Enzyme inhibitors decrease the rate of cellular respiration by reducing the activity of enzymes involved in the process.

Question 27

biofuel

Answer 27

Biofuels are made from organic material known as biomass, which is plant and animal material that can be sourced from many of our existing industries. They offer an alternative to traditional fossil fuels like coal and gas, which are non-renewable

Question 28

The process of creating bioethanol

Answer 28

1. Deconstruction 2. Digestion by enzymes 3. Ethanol fermentation 4. Purification and dehydration

Question 29

Deconstruction

Answer 29

a process that involves breaking down the cell wall and cellulose of wood, paper, plastic and other plant fibres.

Question 30

Digestion by enzymes

Answer 30

the break down the starch and cellulose and convert them into glucose and other sugars. This breaking down of polysaccharides is aided by the presence of water in a process known as hydrolysis.

Question 31

Ethanol fermentation

Answer 31

Ethanol diffuses out of the yeast cells and is harnessed for biofuel production. The ethanol is produced as a product of this process, rather than coming from within the plant.

Question 32

Purification and dehydration

Answer 32

The ethanol is distilled via the removal of water, converting it into a usable form called biofuel. The biofuel is then purified and is ready to be used as liquid fuel.