chapter 3 brock

Question 1

what elements are cells primarily composed of?

Answer 1

H, O, C, N, P and S

Question 2

macronutrients

Answer 2

nutrients required in large amounts

Question 3

micronutrients

Answer 3

nutrients required in very small amounts eg trace elements or growth factors

Question 4

What types of media can you remember?

Answer 4

Culture, selective, differential, enriched

Question 5

All microorganisms conserve energy from either the oxidation of chemicals or from light.
Distinguish between chemoorganotrophs and chemolithotrophs…

Answer 5

Chemoorganotrophs use organic chemicals as their electron donors, chemolithotrophs use inorganic chemicals.

Question 6

How do phototrophic organisms conserve energy?

Answer 6

Phototrophic organisms convert light energy into chemical energy (ATP) and include both the oxygenic and anoxygenic phototrophs.

Question 7

Oxidation-reduction reactions require electron donors and electron acceptors.
What is the reduction potential of a compound?

Answer 7

The tendency of a compound to accept or release electrons.

Redox reactions in a cell use intermediaries like NAD+/NADH as electron shuttles.

Question 8

How is the energy released in redox reactions conserved?

Answer 8

The energy is conserved in compounds that contain energy-rich phosphate or sulphur bonds.
Most commonly, ATP. Longer term storage = polymers which can be consumed to yield ATP.

Question 9

Describe glucose catabolism in microbes

Answer 9

Glycolytic pathway - breaks down glucose to pyruvate; small amount of ATP, generates fermentation products (ethanol, lactic acid etc) according to organism. Yeast - fermentation and respiration.
Extra ATP can be obtained from glucose fermentation if fatty acids derived from coenzyme-A derivatives are fermentation products.

Question 10

Describe electron transport chains

Answer 10

ETC are composed of membrane-associated proteins arranged in order of their increasing reduction potential values - integrated function - to carry electrons from the primary electron donor to the terminal electron acceptor (O2 in aerobic respiration)

Question 11

How does electron transport make things happen?

Answer 11

When electrons are transported through an ETC, protons are extruded to the outside of the membrane, forming the PMF (proton motive force).

Question 12

Name some examples of key protein carriers

Answer 12

Key protein carriers include flavins, quinones, the cytochrome bc1 complex, and other cytochromes.

Question 13

How is the PMF harnessed?

Answer 13

The cell uses the PMF to make ATP through the activity of ATPase, in all forms of respiration and photosynthesis

Question 14

Compare the products of fermentation and respiration

Answer 14

Respiration > fermentation energy yield.
Citric acid cycle generates CO2 and electrons for the ETC, as well as biosynthetic intermediates.
The glyoxylate cycle is needed for the catabolism of 2C electron donors eg acetate.

Question 15

How does anoxia impact on respiration?

Refer to chemolithotrophs and phototrophs.

Answer 15

Several terminal electron acceptors can substitute for oxygen in anaerobic respiration.
Chemolithotrophs use inorganic compounds as electron donors; phototrophs use light energy.

Question 16

What’s gluconeogenesis?

Answer 16

The production of glucose from nonsugar precursors.

Question 17

What are lipids in Bacteria and Eukaryotes composed of?

Answer 17

Only lipids of Bacteria and Eukarya contain fatty acids (C12-C18 typically), which are attached to glycerol.

Question 18

What is nitrogen fixation?

Answer 18

The reduction of N2 to NH3 is nitrogen fixation - it’s catalysed by nitrogenase (2 proteins, dinitrogenase and dinitrogenase reductase).

Question 19

What is ATPase (ATP synthase)?

Answer 19

It’s a multiprotein enzyme complex embedded in the cytoplasmic membrane that catalyses the synthesis of ATP coupled to the dissipation of the proton motive force.

Question 20

What’s an autotroph?

Answer 20

An organism capable of biosynthesising all cell material from CO2 as the sole carbon source.

Question 21

What’s a chemolithotroph?

Answer 21

An organism that can grow with inorganic compounds as electron donors in energy metabolism.

Question 22

What’s a chemoorganotroph?

Answer 22

An organism that obtains its energy from the oxidatoin of organic compunds.

Question 23

What happens in the citric acid cycle?

Answer 23

It’s a cyclical set of reactions resulting in the conversion of acetate to two molecules of CO2.

Question 24

Define ‘electron acceptor’

Answer 24

A substance that can accept electrons from an electron donor, becoming reduced in the process.

Question 25

Define ‘electron donor’

Answer 25

A substance that can donate electrons to an electron acceptor, becoming oxidised in the process

Question 26

Fermentation is…

Answer 26

anaerobic catabolism in which an organic compound is both an electron donor and an electron acceptor and ATP is produced by substrate-level phosphorylation.

Question 27

Respiration is…

Answer 27

the process in which a compound is oxidised with O2 or an O2 substitute as the terminal electron acceptor, usually accompanied by ATP production by oxidative phosphorylation.

Question 28

Anaerobic respiration is…

Answer 28

a form of respiration in which oxygen is absent and alternative electron acceptors are reduced.

Question 29

Substrate-level phosphorylation is…

Answer 29

the production of ATP by the direct transfer of an energy-rich phosphate molecule from a phosphorylated organic compound to ADP.