Nutrition and Metabolism of Bacteria

Question 1

Why does ATP hydrolysis release energy?

Answer 1

1. ATP is an unstable, high-energy molecule due to the presence on 2 phosphoanhydride bonds.
2. Its hydrolysis is an exergenic reaction, releasing energy.
3. Upon enzyme-catalysed hydrolysis, ATP dissociates into ADP and phosphate, releasing energy and allowing coupled thermodynamically unfavoured reactions to take place (free energy input required).

Question 2

Why does ATP hydrolysis release energy?

Answer 2

1. ATP is an unstable, high-energy molecule due to the presence on 2 phosphoanhydride bonds.
2. Its hydrolysis is an exergenic reaction, releasing energy.
3. Upon enzyme-catalysed hydrolysis, ATP dissociates into ADP and phosphate, releasing energy and allowing coupled thermodynamically unfavoured reactions to take place.

Question 3

How is ATP formed from ADP?

Answer 3

Energy obtained from the oxidation of nutrients is used to convert ADP into ATP.

Question 4

Bacteria can be classified based on their source of energy. What are the 4 sources of energy?

Answer 4

sunlight
chemical
radioactive
oxygen requirements

Question 5

Bacteria can be classified based on oxygen requirements. There are obligate aerobes, obligate anaerobes, facultative anaerobes, aerotolerant anaerobes and microaerophiles. What does each term mean?

Answer 5

Obligate aerobes - require Oxygen for growth
Obligate anaerobes - Oxygen is toxic
Facultative anaerobes - can live without oxygen
Aerotolerant anaerobes - can tolerate oxygen
Microaerophiles - need some Oxygen

Question 6

Bacteria can be classified based on oxygen requirements. There are obligate aerobes, obligate anaerobes, facultative anaerobes, aerotolerant anaerobes and microaerophiles. What does each term mean?

Answer 6

Obligate aerobes - require Oxygen for growth
Obligate anaerobes - Oxygen is toxic
Facultative anaerobes - can live without oxygen
Aerotolerant anaerobes - can live with oxygen
Microaerophiles - need some Oxygen

Question 7

What is selective media?

Answer 7

Selective media - suppress growth of unwanted bacteria and promotes growth of target bacteria.

Question 8

What is differential media?

Answer 8

Differential media - used to distinguish one bacteria from another - all bacteria grow but only certain bacteria can metabolise a dye and cause a colour change.

Question 9

What did Robert Koch come up with?

Answer 9

Provided proof that microorganisms were the cause of infectious diseases.

Question 10

Koch’s postulates show that certain microorganisms can be the cause of disease. Describe the 4 steps in Koch’s postulates process.

Answer 10

1. Organism must be present in all cases of the disease (not in healthy individuals)
2. Organism is isolated from infected animal and cultivated in pure culture away from healthy body.
3. Cells from the pure culture, when inoculated into healthy animal, must give rise to characteristic symptoms of disease.
4. Organism must then be re-isolated and grown and shown to be the same as the original organism.

Question 11

What are the main environmental determinants of microbial growth?

Answer 11

Temperature, pH, oxygen, light, moisture, nutrient type and availability, environment.

Question 12

Describe Psychrophiles.

Answer 12

Microbes which grow best at low temperatures.
Optimum = -10 to 20
Enzymes denatured at moderate temperatures.
Fluidity and flexibility of membranes are maintained by polyunsaturated fatty acids in lipid membranes.

Question 13

Describe Mesophiles.

Answer 13

Microbes which grow at moderate temperatures.
Optimum = 20 to 45
Most common = are pathogens of mammals
Can survive at lower temperatures but will have slow rate of growth.

Question 14

Describe Thermophiles.

Answer 14

Microbes which grow at very high temperatures.
Optimum = >45
Enzymes tolerate near boiling temperatures.
Enzymes used in industry for faster reaction.

Question 15

Name 3 enzymes which can breakdown the toxic metabolites created when some microbes are exposed to oxygen.

Answer 15

Superoxide dismutase, catalase, and peroxidase

Question 16

What is the optimal pH range for most bacteria?

Answer 16

pH 7.4 - 7.6

Question 17

What is the optimal pH range for Enterobacteriaceae?

Answer 17

pH 4.3 - 9.5

Question 18

What is the optimal pH range for moulds and yeasts?

Answer 18

pH 4 - 6

Question 19

What are halophiles?

Answer 19

Microbes that require a salt rich environment for growth and survival.

Question 20

What are osmophiles?

Answer 20

Organisms that can grow in very high solute conditions.

Question 21

What happens when eubacteria is exposed to UV light?

Answer 21

UV light is lethal to eubacteria = non-photosynthetic bacteria - results in genetic mutation and cell death.

Question 22

Certain bacteria produce pigments to protect themselves from strong sunlight/UV. What are these pigments called? How does it work?

Answer 22

Carotenoids.

They absorb sunlight and dissipate the energy thereby protecting themselves.

Question 23

Metabolism fact.

Answer 23

Catabolic reactions provide the energy to drive the anabolic reactions which result in growth.

Question 24

Many enzymes require cofactors in order to function. What are cofactors?

Answer 24

A cofactor is an inorganic non-protein chemical compound or metallic ion that is required for an enzyme’s activity as a catalyst, a substance that increases the rate of a chemical reaction.
Many co-factors are vitamins (nicotinic acid/niacin or vitamin B1 (thiamine) or B2 (riboflavin).

Question 25

Many enzymes require cofactors in order to function. What are cofactors?

Answer 25

A cofactor is a non-protein chemical compound or metallic ion that is required for an enzyme’s activity as a catalyst, a substance that increases the rate of a chemical reaction.
Many co-factors are vitamins (nicotinic acid/niacin or vitamin B1 (thiamine) or B2 (riboflavin).

Question 26

What is a coenzyme?

Answer 26

Coenzymes work by binding to the active side of the enzymes, the site that works in the reaction. Since enzymes and coenzymes are nonmetal organic molecules, they bind together by forming covalent bonds.

Question 27

What are the 3 metabolic pathways which bacteria use to produce energy?

Answer 27

EMP of glycolysis
Aerobic respiration
Fermentation

Question 28

What 2 ways can phosphorylation of ADP occur?

Answer 28

Substrate-level phosphorylation

Oxidative level phosphorylation

Question 29

What is substrate-level phosphorylation?

Answer 29

ATP synthesis by substrate-level phosphorylation involves the transfer of phosphate onto ADP from another chemical compound (substrate).
The energy required for ATP synthesis comes from chemical bond breakage.

Question 30

What is oxidative phosphorylation?

Answer 30

ATP synthesis by oxidative phosphorylation involves the transfer of phosphate onto ADP directly by a membrane-bound enzyme called ATP synthase. The energy required for this process comes from oxidation of cofactors NADH and FADH2 which produces transmembrane proton motive force used by ATP synthase.

Question 31

Name the 2 electron transfer coenzymes.

Answer 31

FAD and NAD

Question 32

What is a prosthetic group?

Answer 32

A prosthetic group is a tightly bound catalytic group which is not part of the protein framework but is an integral part of the enzyme structure.

Question 33

Krebs cycle is an amphibolic pathway. What does this mean?

Answer 33

Involves catabolic and anabolic processes.