chapter 3 - microbial metabolism overview

Question 1

What is metabolism?

Answer 1

the sum total of all chemical reactions needed for life

Question 2

What are the two main types of metabolism?

Answer 2

1. catabolisms: reaction used to break complex molecules to obtain energy
2. anabolism: reactions used to synthesize cellular materials

Question 3

Explain how the types of metabolisms are defined by source of energy

Answer 3

autotrophs obtain carbon from CO2
heterotrophs obtain carbon from inorganic matter
chemoorganotrophs obtain energy and reducing power from organic matter
chemolithotrophs obtain energy and reducing power from inorganics

Question 4

How does energy conservation work with electron flow?

Answer 4

catabolism uses exergonic (releasing energy) reaction to drive synthesis of ATP

anabolism uses endergonic reactions which consumes ATP to drive biosynthesis of cellular material

Question 5

What are the main components of redox reactions?

Answer 5

1. electrons are transferred from an electron donor
   loss of electrons is called oxidation, electron donor is oxidized
2. electron acceptor gains the transferred electrons
   the gain of electrons is called reduction, electron acceptor is reduced.

Question 6

What is reduction potential?

Answer 6

-catabolism is depended on directed flow of electron, from electron donor to electro acceptor
- it is the affinity of substance for electrons

Question 7

What are the components of the redox tower?

Answer 7

-strongest electron donors are at the top, and strongest electron acceptors are at the bottom

Question 8

What is an example of an electron carrier?

Answer 8

NAD+ / NADH

Question 9

How is NAD+/NADH cycled?

Answer 9

1. enzyme I reacts with electron donor and oxidized form of coenzyme NAD
2. NADH and reaction product are formed
3. enzyme II reacts with electron acceptor and reduced form of coenzyme NADH
4. NAD+ is released

Question 10

How do you calculate free energy?

Answer 10

delta Eo is proportional to delta Go
delta Go = n (# of electrons transferred) x 96.5 kJ/V x delta Eo

Question 11

What are the components that surround catalysis?

Answer 11

• energy of activation: minimum energy required to initiate a chemical reaction
• catalyst: required to overcome the energy activation

Question 12

What does enzymes are biocatalysts?

Answer 12

lowers activation energy, increasing enzyme rate
enzyme binds substrate, forming enzyme-substrate complex, then releases product and enzyme

Question 13

What is a summary of the glycolysis pathway?

Answer 13

glucose oxidized to pyruvate
1. preparative stage
2. oxidative stage
3. reductive stage

Question 14

What is a summary of the citric acid cycle?

Answer 14

pyruvate is oxidized to CO2
Products for 1 pyruvate:
- 1 ATP
- 3 CO2
- 4 NADH
- 1 FADH2

Question 15

What are the essentials of fermentation?

Answer 15

1- substrate-level phosphorylation
2- redox balance via pyruvate reduction
3- excretion of waste

Question 16

How is redox balance maintained?

Answer 16

1- conserve energy - producing energy rich compounds
2- redox balance - donate electrons back to an electron acceptor derived from original organic donor
- NADH back to NAD+
- dumping electrons onto some intermediates

Question 17

What is a summary of respiration?

Answer 17

• electrons transferred from reduced electron donors to external electron acceptors
• reoxidation:
  1- electron transport using electron carriers
  2- electron transport occurs in cytoplasmic membrane
  3- forms electrochemical gradient conserves energy through ATP synthesis

Question 18

What is the overview of proton motive force?

Answer 18

1- NADH processes electrons with high reduction potential
2- oxidation of NADH releases large amount of energy
3- electrons from NADH transferred through redox reactions
4- protons are transported from insaide to outside cellular membrane ( - to +)
5- oxidative phosphorylation where synthesis of ATP at the expense of proton motive force

Question 19

What are two types of electron carriers?

Answer 19

1- NADH dehydrogenase: active site binds NADH, two electrons and one proto from NADH plus proton from cytoplams
2- Flavoproteins: contains flavin
accepts 2 electrons and 2 protons from NADH dehydrogenase and donates one electron with the proton released into cytoplasm

Question 20

What is complex I of proton motive force?

Answer 20

NADH dehydrogenase
1- primary electron donor enter at complex I or II
2- NADH oxidized to NAD+, ubiquinone(Q) reduced to QH2 and diffuses to complex III
3- four H+ released outside - contribute to proton motive force

Question 21

What is complex II of proton motive force?

Answer 21

succinate dehydrogenase
1- alternate entry point for primary electron donor
2- 2 electrons from FADH2 and 2 protons from cytoplasm transferred to Q to QH2
3- less energy conserved due to lack of H+ translocation

Question 22

What is complex III of proton motive force?

Answer 22

cytochromes
1. transfers electron from QH2 to cytochrome c
2. pumps 2 H+ from QH2 to outside cytoplasmic membrane
3. cytochrome c shuttles to complex IV

Question 23

What is complex IV of proton motive force?

Answer 23

cytochrome a and a3
1. terminal oxidase reduces O2 to H2O
2. needs 4 electrons and 4 protons from cytoplasm
3. pumps a proton per electron outside

Question 24

How is ATP generated from proton motive force?

Answer 24

• F1: multiprotein complex extending to the cytoplasm that catalyzes ATP synthesis
• F0: membrane integrated proton translocating multiprotein complex
• H+ passing through F0 is coupled to the rotation of F1