Lecture 8 Metabolism and Catabolism

Question 1

Metabolism requires enzymes describe what enzymes do and name the examples from lectures.

Answer 1

• Acts on substrates, convert to products
• Enzymes increase reaction rates by lowering activation energy.
  Ex.) - Phosphatase, Kinase, Cellulase
• Dehydrogenases - oxidation and reductions reactions

Question 2

What are dehydrogenases used in?

Answer 2

oxidation and reduction reactions (LEO says GER)

Question 3

How do enzymes lower the energy of activation?

Answer 3

• Increase local concentrations

- Orient substrates properly for reactions to proceed

Question 4

Describe Oxidation- Reduction reactions.

Answer 4

• Oxidation - removal of electrons
• Reduction - addition of electrons
• Substance oxidized donor, substance reduced is acceptor (pair = redox couple)
• Redox often involve not just the transfer of electrons but both an electron + proton (H atom, example: NAD+/NADH)

Question 5

What is the Psychrophilic, Obligate Anaerobe that Oxidizes Acetate with the Reduction of Iron.

Answer 5

Rhodoferax metabolins

Question 6

Describe what Reduction Potential is (E0)

Answer 6

• Equilibrium constant for redox reactions
• Measures tendency of donor to lose electrons
• More negative E0 better donor
• More positive E0 better acceptor.

Question 7

Describe what the electron tower is.

Answer 7

Greater the difference –> the more negative the Gibbs free energy is.

Question 8

What are the two classes of electron Carriers in Redox Reactions?

Answer 8

• Freely diffusible (in cytoplasm)
  ex. ) NAD+ and NADH+
• Reduced forms (NADH, NADPH) are the “reducing power” in the cell

Membrane- bound
Ex.) flavoproteins, cytochromes, quinones

Question 9

What are Heterotrophs

Answer 9

A metabolic group

• reduced, preformed organic compounds as C source (animals, many microbes)
• Convert large amount of C to CO2

Question 10

What are Autotrophs

Answer 10

A metabolic group

• CO2 as C source (plants, many microbes)
• synthesize organic compounds used by heterotrophs
• Also called primary producers.

Question 11

Where to phototrophs get there energy from?

Answer 11

light

Question 12

Where do Chemotrophs get there energy from?

Answer 12

oxidize chemical compounds (often same as their C source)

Question 13

Where do lithotrophs get there electrons from?

Answer 13

Inorganic molecules as electron donors

- unique to few bacteria and archaea (prokaryotes)

Question 14

Where do Organotrophs get there electrons from?

Answer 14

Organic molecules as donors

Question 15

Describe the Tricarboxylic acid cycle

Answer 15

• Many different energy sources are funneled into common degradative pathways
• Most pathways generate glucose or intermediates of the pathway used in glucose metabolism
  ATP by 2 means:
  Substrate level Phosphorylation
  Oxidative Phosphorylation

Question 16

What are the two functions of organic energy sources?

Answer 16

• Oxidized the release energy

- Provide building blocks for anabolism

Question 17

What are Amphibolic pathways?

Answer 17

• Metabolic pathways that function both catabolically and Amphibolic pathways

Question 18

Describe Aerobic Respiration

Answer 18

• Process that can completely catabolize an organic energy source to CO2 using
• Glycolytic pathways (glycolysis)
• Tricarboxylic Acid Cycle (TCA)
• Electron transport chain with oxygen as final electron acceptor
• Produces ATP (most indirectly, via electron transport)

Question 19

Breakdown of glucose to pyruvate

Answer 19

• Three paths
• Emden - Meyerhof (glycolysis)
• Pentose Phosphate
• Entner-Doudoroff

Question 20

Embden-Meyerhof Pathway (Glycolysis)

Answer 20

• Most common form of glucose breakdown
• Occurs in cytoplasm
• Functions in presence or absence of 02
• Ten reactions, in two stages.
  Review this pathway

Question 21

Describe in painstaking detail Glycolysis, What are the Key reactions, what is the net yield

Answer 21

-6C Stage: glucose phosphorylated twice (requires ATP) generating fructose 1,6-bisphosphate.

• 3 C Stage:
• Fructose 1,6-bisphosphate split into 2 glyceraldehyde 3-P then converted to pyruvate
• Key Reactions
• oxidations –> NADH
• Substrate-level phosphorylated > ATP

-Net yield - 2ATP, 2NADH , 2 Pyruvate

Question 22

What Kind of pathway is Glycolysis?

Answer 22

Amphibolic pathway

Question 23

Describe the NADH and ATP Generating Steps of Glycolysis

Answer 23

Reaction 1

• Glyceraldehyde-3-phosphate oxidized and phosphorylated-generates high-energy P bond
• NAD+ reduced to NADH
• Enzyme used G3P dehydrogenase

Reaction 2

• Phosphorylation of ADP by high energy metabolic substrate
• Generates ATP by substrate level phosphorylation
• Enzyme used 3PG Kinase

The last reaction is also a Substrate-Level Phosphorylation
Enzyme used pyruvate kinase

Question 24

Another Method of Glucose Breakdown is Pentose Phosphate describe it! Bitch!

Answer 24

• Starts by converting Glucose-6-P to Ribulose-5_P (pentose)
• Generates many sugars for biosynthesis
• Yields 6 NADPH(reducing power for biosynthesis) and 1 ATP

Question 25

Another Method of Glucose Breakdown is the Entner - Doudoroff pathway. Describe it Now and if you don’t get it write you will be killed by hundreds of tiny turtles.

Answer 25

• Combines reactions of glycolysis and pentose phosphate

- 1 ATP, 1NADH, 1NADPH

Question 26

Describe the Tricarboxylic Acid Sycle (Citric Acid or Krebs’s)

Answer 26

• Pyruvate completely oxidized to CO2
• In mitochondria of eukaryotes, cytoplasm prokaryotes
• Generates: CO2 and Numerous NADH and FADH2

Question 27

!!!THE TCA CYCLE!!!

Answer 27

!!!THE TCA CYCLE!!!