Lecture 10 -- Central Metabolism I

Question 1

• NAD+/NADH
• NADP+/NADPH
• FMN/FMNH2
• FAD/FADH2

Answer 1

mostly catabolic reactions; mostly anabolic reactions; flavin mononucleotide; flavin adenine dinucleotide

Question 2

• the extra phosphate in NADPH provides enzyme specificity

Answer 2

Difference between Nicotinamide Adenine Dinucleotide molecules

Question 3

1 H+ and 2 e-

Answer 3

NADPH redox rections

Question 4

FAD –> one hydrogen (semiquinone) –> two hydrogens (fully reduced)

Answer 4

FAD process

Question 5

• provide precursor metabolites and energy to all of the other pathways
• metabolize carbohydrates, four carbon dicarboxylic acids, and acetic acid

Answer 5

Function of central metabolic pathways

Question 6

Embden-Meyerhof-Parnas pathway (glycolysis)
Entner-Doudoroff pathway
Pentose phosphate pathway (Pentose Shunt)

note* all three convert glucose to gylyceraldehyde-3-phosphate and then to pyruvate

Answer 6

The three major pathways of central metabolism

Question 7

• cost 2 ATP, make 4 ATP, net 2 ATP and 4 electrons (2 NADH)
• hexoses require ATP, trioses produce ATP
• one 6 carbon mc to two 3 carbon mcs

Answer 7

EMP (Glycolysis) pathway products and components

Question 8

NO

• more ATP is required for gluconeogenesis than glycolysis (4 vs 2)
• it is a psuedocycle
• the regulation of enzymes ensures reaction can only proceed in one direction at a time (by regulatory factors)

Answer 8

Do gluconeogenesis and glycolysis constitute a metabolic cycle?

Question 9

• 1st ATP consumption step, 2nd ATP consumption step, final ATP production step (different enzymes control different directions)

Answer 9

The points of regulation in Glycolysis/Gluconeogenesis

Question 10

• Glucose 6-phosphate –> polysaccharides, sugar phosphates, aromatic amino acids
• Fructose 6-phosphate –> amino sugars
• Glyceraldehyde 3-phosphate –> phospholipids
• 3-Phosphoglycerate –> serine, glycine, cysteine
• phosphoenolpyruvate –> aromatic amino acids, muramic acid
• pyruvate –> alanine, valine, leucine

Answer 10

At which points can glycolysis be considered an anabolic pathway?

Question 11

• bacteria use one or the other

- when growing on gluconate, organisms synthesize enzymes of ED pathway

Answer 11

Important things to remember about EMP and ED

Question 12

• not as efficient as glycolysis
• 2 pyruvate + NADH + NADPH + 2H+ + 1 ATP
• 1 carbon to 2 3 carbon mcs

Answer 12

ED pathway

Question 13

• 3 CO2 + glyceraldehyde-3-P + 6 NADPH
• provides pentose phosphates required for nucleic acid synthesis
• provides 4 c sugars for aromatic amino acid synthesis and cell wall components
• major source of electrons from NADPH needed for other pathways

Answer 13

Pentose Phosphate Pathway

Question 14

• Oxidative decarboxylation (picking up electrons)
• Isomerization (splitting into two five carbon molecules)
• Transketolase/Transaldolase reactions (switches around carbons and eventually produces Glyceraldehyde 3-phosphate, which can enter the TCA cycle

Answer 14

Pentose Phosphate Pathway Steps

Question 15

• every intermediate can be converted to any other intermediate on short supply

Answer 15

relationship between pathways

Question 16

glucose –> 2 pyruvate –> lactate + water + energy

- regenerates electron carriers

Answer 16

Fermentation (Anaerobic Respiration)