5.6 Respiration

Question 1

Where does glycolysis occur ?

Answer 1

Occurs in the cytoplasm.

Question 2

What is glycolysis ?

Answer 2

Anaerobic process that splits glucose into 2 smaller 3C pyruvate molecules. ATP and reduced NAD are also produced.

Question 3

What is the first step in glycolysis ?

Answer 3

Phosphorylation occurs when 2 ATP molecules react with glucose to form hexose bisphosphate and 2ADP.

Question 4

What occurs in glycolysis when hexose bisphosphate is formed ?

Answer 4

Lysis occurs, which destabilises the molecule causing it to split into 2 trios phosphate molecules.

Question 5

What occurs when triose phosphate is phosphorylised ?

Answer 5

Another phosphate group is added to the triose phosphate to form triose bisphosphate.

Question 6

What occurs when triose bisphosphate becomes dehydrogenated ?

Answer 6

Triose bisphosphate is the oxidised by the removal of the hydrogen atoms to form 2 pyruvate molecules. NAD+ accepts the hydrogen to form NADH. At the same time, 4 ATP molecules are produced using phosphates from triode bisphosphate molecules.

Question 7

What is glycolysis an example of ?

Answer 7

Is an example of substrate - level phosphorylation (the formation of ATP without an electron transport chain).

Question 8

What are the products of glycolysis ?

Answer 8

2 molecules of ATP and 2 reduced NAD molecules.

Question 9

What is the Link Reaction ?

Answer 9

Second step of respiration, where pyruvate turns into acetyl.

Question 10

Where are the pyruvate molecules transported in the Link Reaction ?

Answer 10

Pyruvate molecules are actively pumped into the mitochondria via a pyruvate H+ symport.

Question 11

Where does the Link Reaction occur ?

Answer 11

Occurs in the matrix of mitochondria, when oxygen is present.

Question 12

What does pyruvate react with in the matrix ?

Answer 12

Pyruvate reacts with coenzyme A to form acetyl CoA. Co2 is released and another molecule of NAD+ is reduced.

Question 13

What is the first step in the Krebs cycle ?

Answer 13

Acetate (2C) is removed from acetyl CoA, which joins with oxaloacetate (4C) to form citrate (6C). CoA is reused in the Link Reaction.

Question 14

What occurs to citrate in the Krebs cycle ?

Answer 14

Citrate is decarboxylated releasing CO2. It is also dehydrogenated, releasing 2 H+ ions, which react with NAD+ to form NADH. This leaves behind the 5C compound.

Question 15

What happens to the 5C compound in the Krebs cycle ?

Answer 15

It is decarboxylated and dehydrogenated, releasing CO2 and 2 H+ ions, which react to form NADH and leaves behind a 4C compound.

Question 16

What happens to the first 4C compound in the Krebs cycle ?

Answer 16

It regenerated another molecule of ATP through substrate-level phosphorylation and is then converted to another 4C compound.

Question 17

What happens to the second 4C compound in the Krebs cycle ?

Answer 17

It becomes dehydrogenated and releases 2 hydrogen atoms, which reduce FAD+ to form FADH2 and a different 4C compound.

Question 18

What happens to the final 4C compound in the Krebs cycle ?

Answer 18

Final 4C compound intermediate is converted to oxaloacetate (4C) by dehydrogenation. This produces a molecule of NADH.

Question 19

What is each step of the Krebs cycle activated by ?

Answer 19

Each step is enzyme activated.

Question 20

How are fatty acids broken down for respiration ?

Answer 20

They are broken down to many molecules of acetyl that then enter the Krebs cycle via Acetyl CoA.

Question 21

How is glycerol broken down for respiration ?

Answer 21

It can be converted to pyruvate and then enters the Krebs cycle via the Link Reaction.

Question 22

How are amino acids broken down for respiration ?

Answer 22

After deamination, the rest of the molecule enters Krebs cycle directly or is changed to pyruvate or acetyl CoA.

Question 23

What is the first step in oxidative phosphorylation ?

Answer 23

Reduced NAD and FAD deliver their hydrogen atoms to the electron transport chain, causing these coenzyme to be re-oxidised.

Question 24

Where do the electrons come from in electron transport chain ?

Answer 24

Hydrogen atoms split to produce H+ and e-. The protons go into the solution in the matrix, while electrons are accepted by the first electron carrier protein in ETC.

Question 25

What occurs in the electron carrier protein ?

Answer 25

Iron ion (Fe 3+) at the core of the electron carrier, accepts the electron and becomes reduced (Fe2+). This electron is then donated to the next cytochrome in the chain.

Question 26

How are the H+ ions pumped into the inter membrane space in the ETC ?

Answer 26

The energy released by the electrons flowing down the electron transport chain are used to pump the H+ ions across the inner membrane and into the intermembrane space, which accumulate due to the permeability of the membrane.

Question 27

What change occurs when protons diffuse through the channels ?

Answer 27

The protons diffuse through the channels and cause a conformational change in the ATP synthase enzyme. This catalyses the addition of Pi to ADP to form ATP.

Question 28

What is the final step in the electron transport chain ?

Answer 28

Oxygen combines with the electrons that come off the final proteins in the electron transport chain and with the protons that have diffused down the channel, it forms water.

Question 29

What is fermentation process ?

Answer 29

Process where complex organic compounds are broken down into simpler inorganic compounds.

Question 30

What is the lactate fermentation pathway ?

Answer 30

Pyruvate acts as hydrogen acceptor taking the hydrogen from reduced NAD, catalysed by the enzyme lactate dehydrogenase. Pyruvate is converted to lactate and NAD regenerated.

Question 31

What is lactic acid converted back to ?

Answer 31

Converted back to glucose in the liver but oxygen is needed to complete this.

Question 32

Why can’t the lactate fermentation pathway occur indefinitely ?

Answer 32

-Reduced quantity of ATP produced would not be enough to maintain vital processes for a long period of time.
-Accumulation of lactic acid causes a fall in pH leading to proteins denaturing. Respiratory enzymes and muscle filaments are made from proteins that will cease to function at a low pH.

Question 33

What are obligate anaerobes ?

Answer 33

They cannot survive in the presence of oxygen. Almost all obligate anaerobes are prokaryotes, although there are sone fungi as well.

Question 34

What are facultative anaerobes ?

Answer 34

They synthesise ATP by aerobic respiration if oxygen is present, but can switch to anaerobic respiration in the absence of oxygen, eg yeast.

Question 35

What are obligate aerobes ?

Answer 35

Can only synthesise ATP in the presence of oxygen. The individual cells of some organisms can be described as facultative anaerobes because they can supplement ATP supplies by employing anaerobic in addition to aerobic respiration when oxygen conc is low.

Question 36

Is alcohol fermentation a reversible process ?

Answer 36

No.

Question 37

What is the alcohol fermentation pathway ?

Answer 37

Pyruvate is converted to ethanal. This can then accept a hydrogen atom from reduced NAD, becoming ethanol. The regenerated NAD can then continue to act as a coenzyme and glycolysis can continue.

Question 38

Is the alcohol fermentation pathway a short-term process ?

Answer 38

Not a short-term process and can continue indefinitely in the absence of oxygen. Ethanol is a toxic waste product to yeast cells and they are unable to survive if the ethanol accumulates above 15%. This allowed to happen during the production of alcohol in brewing.

Question 39

What is the respiratory quotient equation ?

Answer 39

RQ = Volume of CO2 given out / Volume of O2 taken in

Question 40

What is the RQ for glucose during anaerobic respiration ?

Answer 40

RQ = bigger than 1

Question 41

What is the RQ for carbohydrates during aerobic respiration ?

Answer 41

RQ = exactly 1

Question 42

What is the RQ for proteins during aerobic respiration ?

Answer 42

RQ = 0.9 approx

Question 43

What is the RQ for lipids during aerobic respiration ?

Answer 43

RQ = 0.7 approx