Unit 1: Human Cells - Key Area 7 - Cellular Respiration

Question 1

What is the word equation for aerobic respiration?

Answer 1

Glucose + oxygen -> energy + water + carbon dioxide.

Question 2

What must be present for aerobic respiration to occur?

Answer 2

Oxygen.

Question 3

What happens if no oxygen is present in respiration?

Answer 3

The glucose is broken down by a process called fermentation.

Question 4

What is the word equation for fermentation?

Answer 4

glucose -> little energy + lactate

Question 5

What does ATP stand for?

Answer 5

Adenosine triphosphate.

Question 6

What is ATP?

Answer 6

A high energy molecule that provides the energy required in the body

Question 7

What is ATP made up of?

Answer 7

Adenosine and three inorganic phosphate (Pi) groups.

Question 8

When is energy released from ATP?

Answer 8

Energy stored in ATP is released when the bond attaching the last phosphate (Pi) group is broken.

Question 9

What is formed when the energy is released from ATP?

Answer 9

Adenosine diphosphate and an inorganic phosphate.

Question 10

Where does the energy come from to make ATP from ADP + Pi in respiration?

Answer 10

The breakdown of glucose in during respiration.

Question 11

Why is there a constant supply of ATP in our cells?

Answer 11

There is a constant supply of ATP in our cells as it is synthesised as fast as it is used.

Question 12

What is phosphorylation?

Answer 12

Phosphorylation is an enzyme controlled process by which a phosphate group is added to a molecule.

Question 13

What is an example of phosphorylation?

Answer 13

Phosphorylation occurs when Pi is added to ADP to make ATP.
Phosphorylation also occurs when phosphate (Pi) and energy are transferred from ATP to the molecules of a reactant in a metabolic pathway making them more reactive. Due to this some steps in a pathway can only proceed if a reactant becomes phosphorylated and energised, like when glucose is phosphorylised to form glucose - 1 phosphate (more details about this on another slide.

Question 14

What are the 3 stages of aerobic respiration?

Answer 14

1) Glycolysis
2) Citric Acid Cycle
3) Electron Transport Chain (ETC)

Question 15

What is glycolysis?

Answer 15

The breakdown of glucose into 2 pyruvate in the cytoplasm.

Question 16

Where does glycolysis occur?

Answer 16

In the Cytoplasm.

Question 17

What happens in glycolysis?

Answer 17

Glucose (6C) is broken down first into an intermediate compound then into two molecules of pyruvate (3C).

Question 18

What are the 2 phosphorylation reactions that occur in glycolysis called?

Answer 18

The energy investment stage and the energy pay off stage.

Question 19

What happens in the energy investment stage of glycolysis?

Answer 19

2 ATP are used up per molecule of glucose and it involves two phosphorylation reactions. The first is the phosphorylation of glucose and the second is the phosphorylation of the intermediate compound produced into another intermediate compound. In both cases the Pi that is required comes from a molecule of ATP being broken down to ADP and Pi - thus 2 ATP molecules are required in the energy investment phase.

Question 20

What happens in the energy pay off stage of glycolysis?

Answer 20

In the energy pay off stage, enough energy is produced to be able to regenerate 4 ATP molecule. During this dehydrogenase removes hydrogen ions and passes them to the co-enzyme NAD to form NADH which is taken to the electron transport chain.

Question 21

What does glycolycis not require that aerobic respiration does?

Answer 21

Oxygen

Question 22

What is the net gain of ATP in glycolysis?

Answer 22

2ATP

Question 23

What does dehydrogenase do in glycolysis?

Answer 23

Dehydrogenase enzymes remove hydrogen ions from the intermediate compound along with it’s associated electrons and passes them to the coenzyme NAD forming NADH.

Question 24

What is the word equation for dehydrogenase in glycolysis?

Answer 24

2NAD -> 2NADH

Question 25

What is the general purpose of dehydrogenase?

Answer 25

To remove hydrogen ions and electrons and pass them to the co-enzyme NAD, forming NADH.

Question 26

Where does the NADH from glycolycis go?

Answer 26

NADH then travels to the (ETC) electron transport chain.

Question 27

Where does the dehydrogenase enzyme appear in aerobic respiration?

Answer 27

In both glycolysis and the citric acid cycle.

Question 28

Where does most of the NADH produced go to?

Answer 28

The electron transport chain.

Question 29

In aerobic conditions what is pyruvate broken down into?

Answer 29

An acetyl group.

Question 30

What is released from the break down of pyruvate into an acetyl group?

Answer 30

CO2 is released and dehydrogenase removes hydrogen ions and passes them to its co-enzyme NAD to form NADH.

Question 31

What does the acetyl group combine with during aerobic respiration and what does this produce?

Answer 31

The acetyl group combines with co-enzyme A to form acetyl co-enzyme A.

Question 32

What does acetyl co-enzyme A combine with and what does this form?

Answer 32

Acetyl co-enzyme A combines with oxaloacetate to form citrate.

Question 33

What happens to the citrate in the citric acid cycle?

Answer 33

During a series of enzyme controlled steps, citrate is gradually converted back into oxaloacetate which results in the generation of a small amount of ATP, NADH and release of CO2.

Question 34

What is citrate broken down into and what does this release?

Answer 34

A 5C compound and releases NADH and CO2.

Question 35

What is the 5C compound broken down into and what does this release?

Answer 35

A 4C compound. Produces a small amount of ATP, NADH and releases CO2.

Question 36

What is the 4C compound broken down into and what does this release?

Answer 36

Another 4C compound produces NADH.

Question 37

What is the other 4C compound broken down into and what does this release?

Answer 37

Oxaloacetate and produces NADH.

Question 38

Where does the citric acid cycle occur?

Answer 38

In the matrix of the mitochondria.

Question 39

Where does the electron transport chain occur?

Answer 39

In the inner membrane of a mitochondrion.

Question 40

What happens in the electron transport chain?

Answer 40

NADH produced during glycolysis and the citric acid cycle releases the hydrogen ions. The electrons from these are cascaded down the chain releasing energy which is used to pump hydrogen ions across the inner membrane. The return flow of hydrogen ions drives the membrane protein ATP synthase and produce the bulk of the ATP generated by cellular respiration. The final electron acceptor is oxygen which combines with hydrogen ions and low energy electrons to form water.

Question 41

How much ATP is produced per glucose molecule?

Answer 41

38 ATP