Respiration

Question 1

what is aerobic respiration

Answer 1

splitting of a respiratory substrate to release energy and carbon dioxide as a waste product

Question 2

what are the four steps of respiration

Answer 2

1. Glycolysis
2. Link reaction
3. Krebs cycle
4. Oxidative phosphorylation

Question 3

what happens in glycolysis in aerobic respiration

Answer 3

Glucose is phosphorylated to produce 2 molecules of pyruvate, 2 molecules of ATP and 2 molecules of NADH

Question 4

what happens in glycolysis in anaerobic respiration

Answer 4

pyruvate is further converted into lactate with the help of NADH. Lactate is then converted back to pyruvate in the liver. From one molecule of glucose, 2 molecules of ATP (net), 2 molecules of reduced NAD (NADH) and 2 molecules of pyruvate

Question 5

what happens in the link reaction

Answer 5

2 molecules of pyruvate are actively transported into the mitochondria. decarboxylase then removes a molecule of CO2 with a hydrogen also being lost, going on to reduce NAD. acetate formed then combines with
coenzyme A to form a molecule of acetyl coenzyme A. Per glucose molecule 2 molecules of acetyl coenzyme A are formed

Question 6

where does the krebs cycle take place

Answer 6

matrix of mitochondria

Question 7

what happens in the krebs cycle

Answer 7

2 carbon (2C) Acetyl CoA enters the circular pathway from the link reaction in glucose metabolism. 4 carbon (4C) oxaloacetate accepts the 2C acetyl fragment from acetyl CoA to form the 6 carbon (6C) citrate.
Citrate is then converted back to oxaloacetate through a series of oxidation-reduction (redox) reactions. Krebs cycle turns 2 times per molecule of glucose and therefore per molecule of glucose 2 ATP molecules, 6 NADH molecules, 2 FADH molecules and 4 CO2 molecules are produced.

Question 8

what happens in the first stage of oxidative phosphorylation

Answer 8

reduced NAD (NADH) from the Krebs cycle binds to protein Complex I, releasing its hydrogen atoms as protons and electrons. The NAD hydrogen carrier then goes back to the Krebs cycle to be used again. Reduced FAD (FADH) binds to Complex II. It also releases it hydrogen atoms as protons and electrons. The protons move into the mitochondrial matrix whilst the electrons released go into the electron chain.

Question 9

what happens in the second stage of oxidative phosphorylation

Answer 9

electrons are then passed down a chain of protein complexes (Complex I to IV) each having a higher affinity than the previous. In Complexes I, III and IV the energy from the electron is used to pump across protons. For each hydrogen released by NADH 4 protons are pumped across. The protons are pumped into the intermembrane space

Question 10

what happens in the third stage of oxidative phosphorylation

Answer 10

After the electrons have pumped across the protons they are accepted by the final acceptor oxygen. The electrons combine with a proton to form a hydrogen atom, which then combines with oxygen to form water.

Question 11

what happens in the fourth stage of oxidative phosphorylation

Answer 11

pumping of the protons from the mitochondrial matrix to the intermembrane space creates a proton gradient. The protons therefore move across the membrane through protein channel called a stalked particle. The proton motive force provides energy for ATP synthase to produce ATP