T4 (C3,L3): Microbial Metabolism PART 1/4

Question 1

What are the 3 transport mechanisms in prokaryotes?

Answer 1

1. Simple transport
2. Group translocation transport
3. The ABC system (ATP Binding Cassette)

Question 2

Explain Simple Transport

Answer 2

It’s the only membrane-spanning component
Gets its energy from the proton motive force (pmf)
there is a conformational change
1. uniporter
2. antiporter
3. symporter (solute + protein in same direction)

Question 3

Explain Group Translocation

Answer 3

The compound is chemically altered during transport
Energy comes from energy-rich organic compounds (e.g. phospho.enol.pyruvate)
-Enzyme IIc phosphorylates sugar as it enters the cytoplasm
-HPr and Enzyme and Enz IIaI: non-specific cytoplasmic proteins
-Enz IIb peripheral protein
- Enz IIc transmembrane component

Question 4

Explain The ABC system (ATP Binding Cassette)

Answer 4

Three proteins involved:

1. Periplasmic substrate-binding protein
2. Membrane substrate
3. ATP-hydrolyzing protein

• the binding protein interacts with the substrate and has a high affinity for it to bind
• energy is provided by hydrolysis of ATP
• periplasmic binding proteins (in Gram -)
• substrate-binding proteins (in Gram +)

Question 5

Name two ways that simple transport and group translocation differ?

Answer 5

1. transported substances are chemically altered in group translocation, and not altered in simple transport
2. an energy-rich organic compound (phosphoenolpyruvate) is used to drive the reaction in group translocation instead of the proton motive force which drives the simple transporation

Question 6

Define chemotroph, then chemoorganotroph, and chemolithotrophs

Answer 6

Chemtrouph: organisms that conserve energy from molecules

Chemoorganotroph: organisms which conserve energy from the OXIDATION of organic chemicals

Chemolithotrophs: conserve from inorganic compounds

Question 7

Define aerobe, anaerobe, and facultative anaerobe

Answer 7

aerobe: obtain energy from organic compounds IN THE PRESENCE OF OXYGEN

Anaerobe: obtain energy in the absence of oxygen
Facultative anaerobe: can obtain energy in the presence or absence of oxygenj

Question 8

Define phototrophy and give and explain the two classes

Answer 8

Phototrophy: organisms which convert light energy into chemical energy

1. Oxygenic photosynthesis:
   - O2 is made
   - occurs in cyanobacteria and algae
2. Anoxygenic photosynthesis:
   - does NOT yield Oxygen
   - occurs in purple bacteria, green bacteria, heliobacteria

Question 9

with ▲G0 what does - and + mean

Answer 9

Delta G < 0 is - exergoinic

Delta G > 0 is + and endergonic

Question 10

Define activation energy

Answer 10

E. requires to bring molecules in a chemical rxn to a reactive state

Question 11

Describe catalysts

Answer 11

• lowers Activation E., and inc. reaction rate

- only rate is afected, not the energetics

Question 12

1. Name what is required for catalysis to occur:

2. What is the net result?

Answer 12

1. • Enzyme must bind substrate (ES)
     - positive is relative to the active amino acid in the active site
2. The net result: dec acti. energy.
   the energy needed: rxn will be coupled w/ energy-yielding reaction

Question 13

Define prosthetic groups and co-enzymes:

Notes:
names make sense - cellulase = breaks down cellulose,
glucose oxidase = catalyze oxidation of glucose

Answer 13

Prosthetic groups: covalent bonds that bind them tightly to enzymes (like heme in cytochromes)

co-enzymes: loosely bound to enzyme and may be associated with diff. enzymes (e.g NAD/NADH a derivative of VB3 Niacin

Question 14

REDOX RXNS:
Define: oxidation
reduction

Answer 14

oxidation- loss of electron (energy released)

reduction- gain of electron (energy absorbed)

Question 15

Define reduction potential

Answer 15

tendency a substance has to donate or accept an electron, unit V, symbol E0’

Question 16

Name and define the two classes of electron carriers

Answer 16

1. cytoplasmic membrane-bound (prosthetic groups):
function in the membrane-associated electron transport chain

2.freely diffusible (coenzymes): e.g NAD+, NADP+

Question 17

What does ATP bonds consist of

Answer 17

Most energy-rich compound. Has 2 anhydride bonds (high energy)

Question 18

Name derivative of CoEnz A

Answer 18

-AcetylCoA
they have thiodiester bonds
energy FROM ACETYLCOA TRANSFER TO ADP FROM ATP

-NB role in fermentation

Question 19

Name examples of long term energy storers

Answer 19

• polyglucose (starch, glycogen)
• poly.hydroxy.alkanoates
• elemental sulfur