Metabolism: Catabolism

Question 1

Describe Catabolism vs. Anabolism.

Answer 1

-Catabolism is the metabolic breakdown of complex molecules to simple compounds involving oxidative reactions. Catabolic pathways are degradative and yield energy (gain net energy).
-Catabolism (release chemical energy, intermediates can be used for biosynthesis).
 Polymers> monomers(break down building block)> simple chemicals.

-Anabolism is the biosynthesis of complex molecules from low molecular weight precursors involving reductive reactions. Anabolic pathways require input of high energy.
-Anabolism/biosynthesis (requires energy and electrons reducing power).
 Simple chemicals> monomers> polymers.

Question 2

What compounds do heterotrophs like E. coli use as a carbon source?

Answer 2

Organic compounds as carbon source.

Question 3

Chemoheterotrophs

Answer 3

Derives energy and carbon from organic sources.

Question 4

Photoheterotroph

Answer 4

-Carbon from organic compounds/sources.
-Energy from light.

Question 5

Photoautotrophs (process called photosynthesis)

Answer 5

-CO2 from carbon source

-Energy from light (cyanobacteria and plants).

Question 6

Chemoautotrophs (lithotrophs)

Answer 6

-CO2 from carbon source.
-Energy from reduced simple chemical compound (chemosynthesis). (H3S, CH4, NH4+)

Question 7

How do microbes use insoluble polymers?

Answer 7

-Microbes secrete one/more extracellular enzymes/exoenzymes to breakdown insoluble polymers into soluble monomers.
-Monomers are then transported (active transport/group translocation) into the cell using energy dependent transport processes.

Question 8

List the process microbes use insoluble polymers.

Answer 8

Cellulose (polymers/insoluble)- must be degraded.

Cellobiose (soluble)- degraded or transported.

Glucose (soluble)- transported.

Question 9

Heterotrophs

Answer 9

Organic compounds as carbon source.

Question 10

What are precursors?

Answer 10

Precursor metabolites are typically intermediates of a catabolic pathway that are fed into anabolic pathways and are the building blocks that are used to make more complex molecules.

Question 11

In addition to glucose, what other monomers do bacteria use for generation of precursor metabolites and energy?

Answer 11

Fatty acids and amino acids.

Question 12

Monomers are degraded by enzymes in a series of steps:

Answer 12

Energy released is captured and stored in the form of high energy compounds (ATP) and reducing power (NADH).

Question 13

What are different types of monomers for generation of precursor metabolites and energy used in bacteria?

Answer 13

Glucose, fatty acids, and amino acids.

Question 14

What is deamination and beta-oxidation?

Answer 14

In Catabolism, deamination is the breakdown of amino acids and beta-oxidation is the breakdown of fatty acids and glycerol.

Question 15

Name the 3 catabolic pathways for the conversion of glucose to pyruvate.

Answer 15

Glycolysis/EMP, Entner-douderoff pathway (ED), Pentose phosphate pathway (PPP).

Question 16

Glycolysis/EMP

Answer 16

 Most common pathway in eukaryotes.
 Anaerobic and facultative anaerobic bacteria.
 Glucose + 2ADP + 2Pi + 2NAD+> 2 pyruvate + 2NADH + 2 ATP

Question 17

Entner-Douderoff Pathway

Answer 17

 Many aerobic bacteria, some soil bacteria (not in eukaryotes)
 Also used by E. coli in GI tract.
 Generates NADPH (used for biosynthesis)
 Glucose + 2NADP + ADP + Pi> 2 pyruvate + 2NADPH + ATP

Question 18

Pentose Phosphate Pathway

Answer 18

 Generates riobose-5-P, erythrose-4-P, and NADPH for biosynthesis, source of e-.
 Ribose-5-P (used to make nucleoids and to make ATP)
 Erythrose-4-P (used to make vitamin B12)

Question 19

If a mutant bacterium lacks the pentose phosphate pathway which specific biosynthesis reactions in this cell would be affected?

Answer 19

In the absence of the PPP, this mutant will be unable to generate Ribose-5-P and Erythrose-4-P and hence unable to produce nucleic acids (DNA, RNA, ATP) and aromatic amino acids respectively.

Question 20

List 3 ways to generate ATP in microbes:

Answer 20

1. Substrate level phosphorylation (enzymatic reaction is coupled directly to ATP production)
2. Fermentation (final e- acceptors are organic molecules (pyruvate- terminal electron acceptor)
3. Oxidative phosphorylation - Aerobic and anaerobic respiration (ETC)

Question 21

How is aerobic respiration different from anaerobic respiration?

Answer 21

Both involve the use of the Electron Transport Chain but aerobic respiration uses O2 as the terminal electron acceptor whereas anaerobic respiration (example P. aeruginosa in the lung of a CF patient) uses NO3- as the terminal electron acceptor.

Question 22

Is anaerobic respiration same as fermentation?
If not, why?

Answer 22

No, fermentation is a form of anaerobic catabolism but not the same as anaerobic respiration as it does not involve an Electron Transport Chain. Fermentation pathways use an organic molecule like pyruvate as the terminal electron acceptor.

Question 23

Catabolism

Answer 23

Catabolism is the metabolic breakdown of complex molecules to simple compounds involving oxidative reactions. Catabolic requires the output of energy.
(Involve the breaking of bonds)

Question 24

Anabolism

Answer 24

Anabolism is the biosynthesis of complex molecules from low molecular weight (simple compounds) precursors involving reductive reactions. Anabolic pathways require input of high energy.
(Involve creation of bonds)

Question 25

What are polymers?

Answer 25

Complex molecules made up of building blocks (monomers).

Question 26

Oxidation

Answer 26

Energy is used (compound loses electrons, e-)

Question 27

Reduction

Answer 27

Energy is used (compound gains e-)