(5.7) Respiration

Question 1

What are the 4 stages of respiration?

Answer 1

• glycolysis
• the link reaction
• the krebs cycle
• oxidative phosphorylation

Question 2

What is essentially happening during respiration?

Answer 2

Glucose is being burnt through chemical reactions (with oxygen) to produce carbon dioxide, water and energy in the form of ATP

Question 3

Where does glycolysis take place?

Answer 3

In the cytoplasm

Question 4

What happens during glycolysis?

Answer 4

Glucose (6 carbon molecule) is converted into 2 pyruvates (3 carbon molecule)

Question 5

Describe the steps of glycolysis

Answer 5

• glucose is phosphorylated (from 2 ATP molecules) creating hexose phosphate
• because the hexose phosphate is unstable, this is immediately broken down into 2 triose phosphate molecules
• hydrogen is removed from 2 triose phosphate to create 2 pyruvate molecules
• this means triose phosphate has been oxidised

Question 6

What happens to the hydrogen removed from the hexose phosphate molecule in glycolysis?

Answer 6

It is transferred to the coenzyme NAD to create reduced NAD (NADH)

Question 7

What happens to the NADH created in glycolysis?

Answer 7

It is then used in oxidative phosphorylation

Question 8

What is the ATP production in glycolysis?

Answer 8

• the conversion of triose phosphate to pyruvate produces 4 molecules of ATP
• 2 ATP molecules are used for the phosphorylation of glucose
• There is a net gain of 2 ATP molecules

Question 9

Define Phosphorylation

Answer 9

Adding a phosphate group to a molecule

Question 10

Where does the link reaction take place?

Answer 10

In the mitochondrial matrix

Question 11

What happens during the link reaction?

Answer 11

Converts pyruvate into acetyl coenzyme a

Question 12

How much ATP is produced during the link reaction?

Answer 12

There is no ATP created however NADH is produced for oxidative phosphorylation and coenzyme a for the krebs cycle

Question 13

Describe the steps of the link reaction

Answer 13

• a carbon atom is removed from pyruvate forming carbon dioxide
• this removal of carbon from pyruvate creates acetate (2 carbon molecule)
• when making pyruvate into acetate, hydrogen is removed creating more NADH
• the acetate joins with co-enzyme A to form acetyl co-enzyme A

Question 14

What happens during the Krebs cycle?

Answer 14

A series of reactions used to generate NADH and FADH needed for oxidative phosphorylation

Question 15

Describe the steps of the Krebs cycle

Answer 15

• acetyl CoA reacts with oxaloacetate
• CoA is removed from acetyl CoA and returned to the link reaction to be reused
• Citrate is produced (6 carbon molecule)
• Carbon dioxide and hydrogen are removed from citrate creating more CO2 and NADH and citrate becomes a 5 carbon molecule
• decarboxylation and dehydrogenation occurs again which converts the 5 carbon compound into a 4 carbon compound called oxaloacetate
• ATP, 2 molecules of NADH,1 molecule of FAD and 1 CO2 molecule

Question 16

How many times does the krebs cycle take place for each aerobically respired glucose molecule?

Answer 16

twice

Question 17

Where does oxidative phosphorylation take place?

Answer 17

The mitochondrial matrix

Question 18

Describe the steps of oxidative phosphorylation

Answer 18

• NADH and FADH release H atoms which split into H ions and electrons
• electrons passed onto electron carries (embedded in the inner-mitochondrial membrane)
• series of these creates an electron transport chain
• energy is lost as travel between electron carriers
• lost energy is used to pump hydrogen ions from the mitochondrial matrix across the inner membrane
• H ions accumulate in the intermembrane space and generates a proton gradient
• H ions flow back into the matrix through enzyme ATP synthase
• the movement of the of H ions is used to add a phosphate group onto ADP and form ATP (proton movement force)
• once the electrons reach the end of the transport chain passed onto oxygen (final electron acceptor)
• oxygen form with electrons and hydrogen ions to form water

Question 19

What is the final electron acceptor is oxidative phosphorylation?

Answer 19

Oxygen

Question 20

What reactions take place in the mitochondrial matrix?

Answer 20

The Link reaction and Krebs cycle

Question 21

What does the mitochondrial matrix contain?

Answer 21

• enzymes that catalyse the link reaction and krebbs cycle
• NAD and FAD
• oxaloacetate which accepts the acetyl group during the link reaction
• mitochondrial DNA which codes for enzymes and other proteins
• mitochondrial ribosomes - where mitochondrial proteins are assembled