Lecture 14 - Energy Balance and Metabolism I

Question 1

What sugars are capable of entering the glycolytic pathway?

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Answer 1

Hexoses:

• glucose
• fructose
• galactose (through conversion to glucose)

Question 2

How are disaccharides absorbed into the body?

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Answer 2

Disaccharides cannot be absorbed through the intestinal walls and must be broken down first.

Question 3

What are the mechanisms of glucose transport across membranes?
What factors increase/decrease glucose transport?

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Answer 3

• secondary active transport through sodium-glucose co-transport (GI tract and renal tubules)
• facilitated diffusion (most cells)

Insulin increases transport by 10x

Phosphorylation blocks diffusion out of cells (except in liver, kidney, and intestine)

Question 4

What is the net reaction of glycolysis?

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Answer 4

Reactants:

• 1 glucose
• 2 ADP

Products:

• 2 pyruvate
• 4 hydrogens
• 2 ATP`

Question 5

What is the net reaction for the citric acid cycle?

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Answer 5

Products:

• 2 acetyl-CoA
• 6 H2O
• 2 ADP

Reactants:

• 4 CO2
• 16 hydrogens
• 2 CoA
• 2 ATP

Question 6

What is the hydrogen acceptor used in oxidative phosphorylation?

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Answer 6

NAD+ -> NADH

Question 7

What component of the electron transport chains gives up electrons to oxygen?

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Answer 7

Cytochrome A3

Question 8

What is the net number of ATP produced from glycolysis to oxidative phosphorylation?
What is the total energy efficiency?

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Answer 8

Glycolysis: 2 ATP
Citric acid cycle: 2 ATP
Oxidative phosphorylation: 34
——————————————————
Total: 38

Energy efficiency:
-66%

Question 9

What is the net reaction of the pentose phosphate pathway?
How many glucose are used and regenerated in the pentose phosphate pathway?

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Answer 9

Reactants:

• glucose
• 12 NADP+
• 6 H2O

Products:

• 6CO2
• 12 hydrogen
• 12 NADPH

6 glucose are used but 5 are regenerated

Question 10

What process allows for fats to cross the intestine and how do they enter the blood stream?

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Answer 10

Bile salts complex with lipid to for micelles which can cross the intestine (bile salts on fatty acids and lipids on the inside).

Lipids then enter the lymph as chylomicrons and eventually enters the blood.

Question 11

What are the compositions of VLDLs, LDLs, and HDLs?

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Answer 11

VLDL:

• high triglyceride
• moderate cholesterol
• moderate phospholipids

LDL:

• high cholesterol
• moderate phospholipids

HDL:

• high proteins
• low cholesterol
• low fatty acid

Question 12

What are the symptoms of metabolic syndrome?

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Answer 12

• obesity
• fasting hyperglycemia
• hypertension