Central Carbon Metabolism

Question 1

substrates of glycolysis

Answer 1

• 6 carbon sugars
• glucose
• investment of 2 ATP

Question 2

substrates of pentose phosphate

Answer 2

• 5 carbon sugars

Question 3

products of glycolysis

Answer 3

• 2 pyruvate (3 carbons)
• 2 NADH
• 2 ATP

Question 4

Nonreversible steps of glycolysis

Answer 4

• Glucose to glucose-6-phosphate. 1 ATP used. Hexokinase
• Fructose-6-phosphate to Fructose-1,6-Bisphosphate. 1 ATP used. PFK 1
• Phosphoenol pyruvate to pyruvate. 2 ATP produced. pyruvate kinase

Question 5

Substrates of gluconeogenesis

Answer 5

• 2 Pyruvate (3 carbons)

Question 6

Products of gluconeogenesis

Answer 6

• Glucose

Question 7

Nonreversible steps of gluconeogenesis

Answer 7

• Pyruvate to Oxaloacetate. 2 ATP used. pyruvate carboxylase
• Oxaloacetate to PEP. 2 GTP used. PEP carboxykinase
• Fructose-1,6-Bisphosphate to Fructose-6-phosphate. F-1,6-Bpase
• Glucose-6-phosphate to glucose. Glucose-6-phosphatase

Question 8

If you try to synthesize carbs on amino acids or lipids

Answer 8

• start with GAP and avoid expense of investing 2 ATP

Question 9

Substrates of TCA

Answer 9

• pyruvate (3 carbons) to acetyl-CoA (2 carbons)

Question 10

Products of TCA

Answer 10

• 3 CO2
• 12 NADH
• 3 FADH2
• 3 GTP

Question 11

Substrates of pentose-phosphate

Answer 11

• Glucose-6-phosphate

- 12 NADP

Question 12

products of pentose-phosphate

Answer 12

• 6 CO2
• 12 NADPH
• 12 H+
• Pi
• Fructose-6-Phosphate
• Glyceraldehyde-3-Phosphate

Question 13

Source of the amino group of amino acids

Answer 13

• glutamate

- done by glutamate dehydrogenase

Question 14

Glutamate family

Precursor

Answer 14

• Glutamine
• Proline
• Arginine
• alpha-ketoglutarate (5 carbons) from TCA

(GPA)

Question 15

Aspartate family

Precursor

Answer 15

• Asparagine
• Methionine
• Threonine
• Isoleucine (only made from pyruvate)
• Lysine
• Oxaloacetate (4 carbons) from TCA
  (TAMIL)

Question 16

Serine family

Precursor

Answer 16

• Cysteine
• Glycine
• 3-phosphoglycerate from glycolysis
  (Super Cool Guy)

Question 17

Pyruvate family

Precursor

Answer 17

• Valine
• Alanine
• Leucine
• from pyruvate in glycolysis
  (VAL)

Question 18

Aromatic family

Precursor

Answer 18

• Tryptophan
• Tyrosine
• Phenylalanine
• from phosphoenolpyruvate (from glycolysis) and Erythrose-4-phosphate (from pentose phosphate)
  (ATTP)

Question 19

Histidine family

Precursor

Answer 19

• Histidine

- from ribose-5-phosphate from pentose phosphate

Question 20

Beta oxidation of fatty acids

Yields

Answer 20

• catabolizes 2 carbons at a time
• costs 1 ATP to prime fatty acid with CoA
• 1 FADH
• 1 NADH
• 1 Acetyl-CoA

Question 21

Where glycerol from Beta oxidation enters

Answer 21

• enters glycolysis at glycerol phosphate

Question 22

Where acetyl from Beta oxidation enters

Answer 22

• enters TCA condensing with oxaloacetate to form citrate

Question 23

Glyoxylate cycle

Answer 23

• many of the same steps of TCA but the CO2 yielding steps are gone
• isocitrate cleaved to form succinate and glyoxylate instead of proceeding to alpha-ketoglutarate and succinyl-CoA
• glyoxylate combined with another acetyl-CoA to form malate
• two acetyl-CoA molecules have now entered the cycle, and no CO2 has been produced - oxaloacetate
• 1 oxaloacetate used in biosynthesis. the other can be used in TCA to accept acetyl-CoA

Question 24

Glyoxylate cycle purpose

Answer 24

• allows cells to use simple carbon compounds (2C) when glucose isn’t available to put into TCA

Question 25

Nucleotides

Answer 25

• Carbon:
  
  • Glycine
  • Aspartate
    Nitrogen:
  • Glutamine

Question 26

Why use pentose phosphate?

Answer 26

1. When the need for reducing power in the form of NADPH is greater than the need for NADH
2. When erythrose-4-phosphate or ribose-5-phosphate are needed as a precursor for amino acids.