Introduction To Metabolism

Question 1

Contrast anabolism and catabolism

Answer 1

1. Anabolism is the synthesis of a more complex molecule by simple precursors
2. Required for growth and repair
3. Involves the reduction of oxidised carbon
4. Catabolism is the breakdown of food to generate the energy and electrons to reduce the precursors for anabolism
   5 it involves the oxidation of reduced carbon

Question 2

Define autotrophs, heterotrophs and phototrophs

Answer 2

1. Autotrophs obtain carbon from carbon dioxide
2. Heterotrophs obtain carbon from organic compounds
3. Phototrophs obtain energy from light
4. Chemotrophs obtain energy from chemical reactions e.g. oxidation of electron donors

Question 3

Explain two types of alternative metabolism

Answer 3

1. Metabolism of CO2 to methane via hydrogenation in methanogen
   -methanogens can only live in anoxic environments
2. Anaerobic metabolism by the oxidation of organic compounds to CO2, or if no oxygen, the reduction of nitrogen to ammonia to produce energy

Question 4

How come oxgyen is often involved in reactions

Answer 4

Since the reduction of oxygen to water is a thermodynamically favourable process, an endergonic reaction can be coupled to carry out essential reactions.

Question 5

Describe the cellular localisation of metabolism

Answer 5

1. Glycolysis occurs in the cell cytoplasm
2. The link reaction, TCA cycle and ETC are carried out in mitochondria

Question 6

Describe the physiology of the double membrane of mitochondria

Answer 6

1. Mitochondrial double membrane has an inner and outer membrane
2. Between both membranes is the intermembrane space, where the matrix lies within the inner membrane
3. Krebs cycle and fatty acid oxidation take place in the matrix
4. The ETC is localised on the inner membrane
5. Inner membrane as a matrix side and cytoplasmic side
6. Electrical potential across the inner membrane with the negative matrix side and positive cytoplasmic side

Question 7

What pieces of evidence to suggest that mitochondria came from bacteria

Answer 7

1. MtDNA is distinct from the nuclear DNA and is exclusively maternally inherited
2. Have lost the capacity for independent replication relying on nuclear genes for many proteins
3. Ribosomes of the mitochondria are structurally similar to prokaryotes