respiration

Question 1

Why does aerobic respiration yield fewer molecules of ATP than the theoretical
maximum? (4)

Answer 1

Pyruvate is actively transported into the mitochondria (from the cytoplasm).
Hydrogen ions (formed in glycosides) are actively transported into mitochondria. reduced NAD is actively moved into the mitochondria. some of the H+ ions leak out of the lumen without passing through ATP synthase enzyme.

Question 2

Suggest why, even though blood carries oxygen, parasites in the blood are adapted to respire
anaerobically. (3)

Answer 2

Hb has a higher affinity for oxygen then the parasite. There is little oxygen dissolved in the blood plasma. oxygen is not very soluble.

Question 3

Explain why the anaerobic respiration pathway in animal cells can be reversed, but the anaerobic respiration pathway in yeast cells cannot be reversed.

Answer 3

In animals, lactase dehydrogenase enzyme is available to reverse the reaction. It is a single step reaction, nothing is lost or gained. In plants, decarboxylase enzymes is not able to undergo the reverse reaction. Carbon dioxide is lost and it’s a two step reaction so it’s irreversible.

Question 4

Suggest why this lactate is converted into pyruvate by the hepatocytes (liver cells) rather than by the respiring cells in which it is produced. (3)

Answer 4

the liver cells have enzymes to metabolism lactate. they can tolerate low pH. They require oxygen, muscle cells don’t have enough but liver cells do.

Question 5

What is the hydrogen acceptor and intermediate in the anaerobic respiration pathway of plants?

Answer 5

ethanal.

Question 6

Describe what a co enzyme is an give details on their importance in respiration. (6)

Answer 6

A non protein organic molecule which help enzymes to work (especially redox reactions).
coenzymes NAD and FAD are derived from vitamin B3 in your diet. we only require trace amounts as they can be reused. symptoms of low B3 are tiredness and fatigue.
they release hydrogen atoms to the cristae for Oxidative phosphorylation. hydrogen atoms split into H+ and e- crucial for production of ATP. Electrons pass along the ETC releasing energy need to pump H+ ions into the inter membrane space. co enzyme A is also needed to carry acetyl group into the Krebs cycle.

Question 7

describe the differences between NAD and FAD

Answer 7

NAD accepts hydrogen atoms from glucose/krebs/link, FAD only accepts hydrogen atoms in Krebs. NAD is deoxidised at the start of the ETC where as FAD is reoxidised further along the ETC. NAD passes through more electrons carriers and produces more ATP.