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Kaplan: Biochemistry Part I > Chapter 11: Energy Metabolism > Flashcards

Chapter 11: Energy Metabolism Flashcards

1
Q

Energy extraction or catabolism occurs in what 4 stages in the body?

A

Stage 1: metabolic fuels are hydrolyzed in GI tract to monomeric building blocks (glucose, amino acids, and fatty acids) and absorbed

Stage 2: building blocks are degraded to a common metabolic intermediate, acetyl- CoA

Stage 3: the citric acid (Krebs, or tricarboxylic acid) cycle oxidizes acetyl-CoA to CO2. The energy released in this process is primarily conserved by reducing NAD to NADH or FAD to FADH2

Stage 4: The final stage is oxidative phosphorylation in which the energy of NADH and FADH2 is released via the ETC and used by an ATP synthase to produce ATP. This process requires O2

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2
Q

The action of insulin is opposed by what hormones?

A

glucagon, epinephrine, cortisol, and growth hormone

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3
Q

Anabolic and catabolic pathways are controlled at 3 important levels. What are they?

A

Allosteric inhibitors and activators of rate-limiting enzymes

Control of gene expression by insulin and glucagon

Phosphorylation (glucagon) and dephosphorylation (insulin) of rate limiting enzymes

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4
Q

What are the 3 major target tissues for insulin?

A

liver,
muscle
adipose tissue

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5
Q

After a meal, most of the energy needs of the liver are met by what metabolic process?

A

by the oxidation of excess amino acids

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6
Q

Which 2 tissues are insensitive to insulin (insulin independent)?

A

The brain and RBCs

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7
Q

Be able to draw out basic energy metabolism of those in a well-fed (absorptive) state.

A

Place diagram here

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8
Q

Be able to draw out basic energy metabolism of postabsorptive state.

A

Place diagram here

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9
Q

What is the RDA for carbs?

A

4 kcal/gm

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10
Q

What is the RDA for protein?

A

4 kcal/gm

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11
Q

What is the RDA for fat?

A

9 kcal/gm

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12
Q

What is the RDA for alcohol?

A

7 kcal/gm

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13
Q

What is the recommended daily calorie budget?

A

2100 kcal diet

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14
Q

Complete combustion of ketones uses about how many kcal/g?

A

4 kcal/g

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15
Q

What is the preferred fuel of the liver in the well-fed state?

A

glucose and amino acids are

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16
Q

What is the preferred fuel of the sk. muscle in the well-fed state?

A

glucose

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17
Q

What is the preferred fuel of cardiac muscle in the well fed state?

A

fatty acids

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18
Q

What is the preferred fuel of adipose tissue in the well fed state?

A

glucose

19
Q

What is the preferred fuel of the brain in the well-fed state?

A

glucose

20
Q

What is the preferred fuel of the RBCs in the well-fed state?

A

glucose

21
Q

What is the preferred fuel of the liver in the fasting state?

A

fatty acids

22
Q

What is the preferred fuel of the sk. muscle in the fasting state?

A

fatty acids, ketones

23
Q

What is the preferred fuel of cardiac muscle in the fasting state?

A

fatty acids, ketones

24
Q

What is the preferred fuel of adipose tissue in the fasting state?

A

fatty acids

25
Q

What is the preferred fuel of the brain in the fasting state?

A

glucose (ketones in prolong fast)

26
Q

What is the preferred fuel of the RBCs in the fasting state?

A

glucose

27
Q

What are the 2 major roles of the liver in fuel metabolism?

A

maintain a constant level of blood glucose under a wide range of conditions

synthesize ketones when excess fatty acids are being oxidized

28
Q

What 3 things in the liver provide C skeletons for glucose synthesis?

A

lactate, glycerol, and amino acids

29
Q

LPL, an enzyme found in the capillary bed of adipose tissue is induced by what hormone?

A

insulin

30
Q

During the fasting state, the decrease in insulin and increase in epinephrine activate what hormone in fat cells?

A

hormone sensitive lipase

31
Q

Explain what is happening in the liver after a meal to maintain glucose levels?

A
  1. After a meal, the glucose concentration in portal blood is elevated
  2. The liver extracts excess glucose and uses it to replenish its glycogen stores. Any glucose remaining in the iver is then converted to acetyl-CoA and used for fatty acid synthesis
  3. The increase in insulin after a meal stimulates both glycogen synthesis and fatty acid synthesis in the liver. The fatty acids are converted to triglycerides and released into the blood as very low-density lipoproteins (VLDLs). In the well-fed state, the liver derives most of its energy from the oxidation of excess amino acids
32
Q

In general, what is going in between meals in the liver for this organ to help maintain blood glucose and synthesize ketones?

A
  1. Between meals and during prolonged fasts, the liver releases glucose into the blood. The increase in glucagon during fasting promotes both glycogen degradation and gluconeogenesis.
  2. Lactate, glycerol, and amino acids provide C skeletons for glucose
33
Q

After a meal explain the major metabolic actions of adipose tissue.

A
  1. After a meal, the elevated insulin stimulates glucose uptake by adipose tissue. Insulin also stimulates fatty acid release from VLDL and chylomicron triglyceride
  2. LPL lipoprotein lipase, an enzyme found in the capillary bed of adipose tissue, is induced by insulin
  3. The fatty acids that are released from lipoproteins are taken up by adipose tissue and re-esterified to triglyceride for storage
  4. the glycerol phosphate required for triglyceride synthesisz comes from glucose metabolized in the adipocyte
  5. Insulin also very effective in suppressing the release of fatty acids from adipose tissue
34
Q

Another name for triglyceride?

A

triglycerol

35
Q

During the fasting state, the adipose tissue has what major metabolic functions to maintain homeostasis in the body?

A

During the fasting state, the decrease in insulin and the increase in epinephrine activate hormone-sensitive lipase in fat cells, allowing fatty acids to be released in to the circulation

36
Q

Where does lactate go once secreted in the blood?

A

goes to be converted back to glucose in the liver

37
Q

What type of glycolysis do fast twitch muscles participate in?

A

In anaerobic glycolysis

38
Q

Describe fast twitch muscles.

A

involved in primarily short-term activities and high intensity exercise; quick to fatigue

39
Q

Describe slow twitch muscles. (Where they are found, what type of exercise, fatigue level, vascularization)

A

found in the arms and leg

are heavily vascularized and primarily oxidative

used during prolonged low to moderate intensity exercise and resist fatigue

40
Q

During the fetal life the cardiac muscle primarily uses what as an energy source?

A

glucose

41
Q

Post-natally what energy source does cardiac muscle use?

A

B-oxidation of fatty acids

42
Q

In the failing heart what are the major sources of energy for the heart?

A

glucose oxidation increases and B oxidation of fatty acids decreases

43
Q

In hypoglycemic conditions how does the brain regulate glucose levels in the blood?

A

centers in the hypothalamus sense a fall in blood glucose level (<70 mg/dL) , and the release of glucagon and epinephrine is triggered

Kaplan: Biochemistry Part I (27 decks)

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