Lecture 9: Metabolism

Question 1

Most organisms we will study are in what group?

Answer 1

chemoheterotrophs

Question 2

chemoheterotrophs

Answer 2

Organisms that use organic carbon compounds
as sources of both carbon and energy

Question 3

What category do all pathogens and many well categorized bacteria fall into?

Answer 3

chemoheterotrophs

Question 4

saprophyte

Answer 4

an organism that uses dead
organic material for nutrients

Question 5

parasite

Answer 5

an organism that feeds of living organic matter

Question 6

Metabolic pathways for energy storage

Answer 6

• glycolysis (Embden Meyerhoff Pathway)
• photosynthesis
• cellular respiration

Question 7

alternatives to glycolysis in bacteria

Answer 7

• pentose phosphate pathway
• Entner Doudroff pathway

Question 8

photosynthesis

Answer 8

conversion of incident light into ATP
- two pathways: cyclic and non-cyclic

Question 9

Cellular respiration

Answer 9

• aerobic respiration (Krebs cycle)
• anaerobic respiration: uses a different terminal electron acceptor (sulfate or nitrate)

Question 10

Non-photosynthetic metabolism (aerobic and anaerobic)

Answer 10

 Respiration is the
aerobic process
 Fermentation is the
anaerobic process

Question 11

Glycolysis pathway to pyruvate differences between respiration and fermentation

Answer 11

it is the same in both

Question 12

What are all metabolic pathways regulated by?

Answer 12

enzymes

Question 12

How many stages in glycolysis?

Answer 12

2
- preparatory stage
- conversion to pyruvate

Question 12

Preparatory stage of glycolysis

Answer 12

The preparatory
stage is enzymatic
processing of
glucose
 The addition of
phosphate groups
costs the cell energy
in the form of ATP

Question 13

Glycolysis - conversion to pyruvate: step occurrence, net gain, and what the products do

Answer 13

• in this
  set of steps, all
  reactions occur
  twice
   Net gain from
  glycolysis is 2
  molecules of ATP
  and 2 molecules
  of NADH which
  can donate electrons in the electron transport chain

Question 14

Pentose phosphate pathway anaerobic or aerobic?

Answer 14

either

Question 15

What is pentose phosphate pathway important for?

Answer 15

important in biosynthesis as well

Question 16

what can pentose phosphate pathway operate in tandem with?

Answer 16

glycolytic

Question 17

What do the early steps of pentose phosphate pathway produce?

Answer 17

NADPH + H+ (energy)

Question 18

What do the later steps of pentose phosphate pathway do?

Answer 18

Later steps shunt to
biosynthesis or TCA
cycle

Question 19

Entner-Doudoroff

Answer 19

• Similar role to
  Embden-Meyerhof
  glycolysis
   Instead of using 2
  ATP, uses 1 ATP in 6
  carbon stages
   Key intermediate
  KDPG 2-keto-3-deoxy-
  6-phosphogluconate
   Found mainly in some
  G- as substitute for
  glycolysis

Question 20

Why do we care about Entner-Doudoroff pathway

Answer 20

the key intermediate allows us to tell specific bacteria apart, just by their use of KDPG (because a lot of bacteria all look the same)

Question 21

Fermentation

Answer 21

• anaerobic
• pyruvate degraded to form organic end products (like ethanol)
• general mechanism is widespread in bacteria
• makes food, chemicals, and medicine

Question 22

What does chemiosmosis use and what for?

Answer 22

 Use electrons to generate proton gradient

Question 23

What does chemiosmosis allow for?

Answer 23

Allow protons to flow across membrane, use
ATPase running backwards to generate ATP

Question 24

Where does chemiosmosis happen?

Answer 24

• cellular membrane in bacteria
• inner membrane of mitochondria (alpha proteobacteria)

Question 25

What is the point of proton motive force?

Answer 25

Goal of this system is
to create a proton
gradient

Question 26

What is going on in proton motive force?

Answer 26

(protons are pumped across the membrane coupled to oxidation of carriers (NADH, NADPH, FADH2)
- protons flow through F1F0 ATPase
- 2 or 3 H+ yields 1 ATP

Question 30

Best electron acceptors

Answer 30

• oxygen (the best e- acceptor)
  -> allows many starting materials

Question 30

What alternative e- acceptor is useful in anaerobic niche?

Answer 30

TEA
-> but not as high energy

Question 31

Electron transport in different bacteria

Answer 31

E. coli:
 Use NADH, FADH2
 Uses at least 5 cytochromes
 Oxygen as terminal electron acceptor
 Uses different cytochromes depending on PO2
 Fairly inefficient, gets ~1.3 ATP per Oxygen
molecule (P/O) ratio

Paracoccus denitrificans:
-  Can grow
heterotrophically
or autotrophically
 Autotrophy- uses
H2, CO2, NO2
 NO2 is terminal
electron acceptor
anaerobically
 Reduced to N2

Question 32

How to study ETC

Answer 32

• P/O ratio describes efficiency of aerobic respiration (ATP produced per O2)
• proton motive force can be studied using uncouplers (ionophore)
• molecules that interfere with gradient or inhibit..)