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CHAPTER 14 Lipid and Amino Acid Metabolism
Section 1 Section 2 Section 3 Section 4 Section 5 Section 6 Section 7 Section 8 Section 9 Section 10 Section 11
1. Fat, with a caloric value of 9 Calories/g, contains more than twice the energy per gram of glycogen or starch.
The energy derived from fat is nearly ______________ that produced from glycogen or starch.
2. During digestion, triglycerides are hydrolyzed to glycerol, fatty acids, and monoglycerides (one fatty acid attached to glycerol).
Triglycerides are hydrolyzed into ___________, fatty acids and monoglycerides during digestion.
3. For transport within the aqueous environment of the lymph and blood, insoluble lipids are complexed with proteins to form lipoprotein aggregates called chylomicrons (see Figure 14.1).
Lipoprotein aggregates of insoluble lipids and proteins, known as ________________, are vehicles for transport of insoluble lipids in blood and lymph.
4. Adipose tissue is a kind of connective tissue where triglycerides are stored.
Triglycerides are stored in _____________ tissue.
5. Fat mobilization occurs through the hydrolysis of stored triglycerides, followed by the entry of fatty acids and glycerol into the bloodstream.
Hydrolysis of triglycerides acts to mobilize fat for entry of the products, ____________ and ____________ into the bloodstream.
6. The glycerol hydrolyzed from fats can provide energy to cells. Glycerol is converted to dihydroxyacetone phosphate, one of the chemical intermediates of glycolysis (see Reaction 14.1).
________________________ is the product from hydrolysis of glycerol as well as an intermediate in glycolysis.
7. Fatty acids that enter tissue cells cannot be oxidized to produce energy until they pass through the mitochondrial membrane. This can occur when the fatty acid is converted into fatty acyl CoA by reaction with coenzyme A (see Reaction 14.2).
Fatty acids must first be converted to ________________ in order to pass through the mitochondrial membrane for oxidation to produce energy.
8. The energy needed for synthesis of fatty acyl CoA is produced by the hydrolysis of ATP to AMP and PPi and the subsequent hydrolysis of PPi to 2Pi.
Hydrolysis of ____________ and PPi provides the energy for synthesis of fatty acyl CoA.
9. The fatty acyl CoA molecules that enter mitochondria are degraded in a catabolic process called b-oxidation.
_________________ is the process through which fatty acyl CoA molecules are degraded in the mitochondria.
10. The b-oxidation pathway for fatty acid degradation to acetyl CoA is often called the fatty acid spiral (see Figure 14.5).
Another name for the b-oxidation pathway is the ___________________.
11. Every run through the spiral produces one molecule each of acetyl CoA, NADH, and FADH2 until the fatty acyl CoA is only four carbons long.
Each pass through the fatty acid spiral produces one molecule of acetyl CoA, NADH, and __________.
12. In the last spiral, the four-carbon chain of butyryl CoA passes through the b-oxidation sequence, and it produces one molecule of FADH2, one molecule of NADH, and two molecules of acetyl CoA (see Reaction 14.6).
The last pass through the fatty acid spiral produces ________ molecules of acetyl CoA.
13. The breakdown of stearic acid (18 carbons) requires eight passes through the b-oxidation sequence and produces nine molecules of acetyl CoA, eight molecules of FADH2 and eight molecules of NADH (see Reaction 14.7).
_____________ passes through the b-oxidation sequence are needed to breakdown stearic acid (18 carbons) to produce nine molecules of acetyl CoA.
14. Capric acid has ten carbon atoms and is converted to acetyl CoA through b-oxidation.
How many acetyl CoA molecules, FADH2, and NADH molecules are produced from b-oxidation of capric acid?
15. As a stearoyl CoA molecule (18 carbons) passes through the b-oxidation spiral, 120 molecules of ATP are produced (see Table 14.1). Each acetyl CoA enables the production of 10 ATP’s, while each NADH and FADH2 result in 2.5 and 1.5 molecules of ATP, respectively.
b-oxidation of one stearoyl CoA molecule produces 120 _______ molecules.
16. The complete oxidation of 3 six-carbon glucose molecules (also 18 carbons total) yields 96 ATP molecules.
Does the oxidation of glucose yield more or less molecules of ATP per carbon than the oxidation of fatty acyl CoA molecules.
Self Test Questions: 1. Suppose you have a 22 carbon long fatty acid.
17. As the concentration of acetyl CoA builds up, the excess is converted within the liver to three substances called ketone bodies: acetoacetate, b-hydroxybutyrate, and acetone.
a) Acetyl CoA is converted into _______________ bodies in the liver. b) List the three compounds known as ketone bodies.
18. Diabetes mellitus, like a long fast or starvation, also produces an imbalance in carbohydrate and lipid metabolism.
A type of diabetes called diabetes ____________ results in an imbalance in carbohydrate and lipid metabolism.
19. The increase in fatty acid metabolism caused by diabetes mellitus leads to excessive production of acetyl CoA and a substantial increase in the level of ketone bodies in the blood.
Excessive levels of acetyl CoA and ___________in the blood result from increased fatty acid metabolism as a result of diabetes mellitus.
20. A concentration of ketone bodies higher than about 20 mg/ 100 mL of blood is called ketonemia. At a ketone body level greater than 70 mg/100mL of blood, ketonuria will occur (ketone bodies in the urine). The smell of acetone may also occur on the person's breath at these high levels. If an individual exhibits ketonemia, ketonuria and acetone breath, the condition is known as ketosis.
a) If 100 mL of blood contains 250 mg of ketone bodies, the proper clinical diagnosis would be ________________. b) List the symptoms of ketosis.
21. Degradation by the b-oxidation pathway takes place in cellular mitochondria, whereas biosynthesis of fatty acids occurs in the cytoplasm.
Fatty acids are synthesized in a cell’s ______________.
22. One aspect of fatty acid synthesis and fatty acid degradation is the same. Both processes take place in units of two carbon atoms.
Fatty acids are synthesized in units of _________ carbon atoms.
23. The most important function of amino acids is to provide building blocks for the synthesis of proteins in the body. It is estimated that about 75% of amino acid utilization in a normal, healthy adult is for this function.
____________________ are building blocks used in protein biosynthesis.
24. The amino acids used in the maintenance of tissue proteins come from proteins that are eaten and hydrolyzed during digestion, from the body’s own degraded tissue, and from the synthesis in the liver of certain amino acids.
The three sources of amino acids for biosynthesis of proteins come from hydrolysis of proteins, degraded tissues and ________ of amino acids in the liver.
25. The amino acids from digestion, degradation of tissues and synthesis in the liver constitute what is called the amino acid pool.
The ___________________ contains amino acids from digestion of proteins, degradation of the organism’s own tissues, and biosynthesis of amino acids in the liver.
26. The dynamic process in which body proteins are continuously hydrolyzed and resynthesized is called protein turnover.
Protein _____________ is the process through which proteins and amino acids are recycled.
27. The turnover rate of proteins is expressed as a half-life.
A protein’s turnover rate is often expressed as a _____________.
28. The half-life of liver proteins is about 10 days, while muscle protein half-lives are 180 days.
Are the half-lives of muscle proteins longer or shorter than liver protein half-lives.
29. Enzymes and polypeptide hormones have half-lives on the order of a few minutes.
Examples of proteins that have very rapid turnover rates are ________ and polypeptide hormones.
30. The three steps in amino acid catabolism are transamination, deamination and urea formation.
Amino acids are degraded to urea through transamination followed by _____________, then urea formation.
31. Transaminase is an enzyme that catalyzes the transfer of an amino group.
The transfer of amino acid groups is catalyzed by ___________________.
32. Transamination is the enzyme-catalyzed transfer of an amino group to a keto acid.
In transamination, an amino group is transferred to a _________.
33. The net effect of the transamination reactions in the catabolism of amino acids is to use nitrogen from a variety of amino acids to form glutamate and aspartate.
The final products of transamination reactions are ____________ and aspartate.
34. Oxidative deamination is an oxidation process resulting in the removal of an amino group.
Removal of an amino group is referred to as oxidative ________.
35. The ammonium ions (NH4+) released by the glutamate dehydrogenase reaction are toxic to the body and must be prevented from accumulating. In the urea cycle, which occurs only in the liver, ammonium ions are converted to urea (see Figure 14.9).
In the urea cycle, _______________ions are converted to urea.
36. The urea cycle processes the ammonium ions in the form of carbamoyl phosphate, the fuel for the urea cycle.
The fuel for the urea cycle is __________________________.
37. After the amino group is gone, the skeletons of all 20 amino acids are degraded into either pyruvate, acetyl CoA, acetoacetyl CoA (which is degraded to acetyl CoA), or various substances that are intermediates in the citric acid cycle (see Figure 14.10).
Amino acids are degraded to either _____________, acetyl CoA, acetoacetyl CoA, or substances that are intermediates in the citric acid cycle.
38. A glucogenic amino acid is an amino acid whose carbon skeleton can be converted metabolically to an intermediate used in the synthesis of glucose.
Amino acids that can be converted to intermediates in the synthesis of glucose are known as _______________ amino acids.
39. A ketogenic amino acid is an amino acid whose carbon skeleton can be converted metabolically to acetyl CoA or acetoacetyl CoA.
Amino acids that can be converted to acetyl CoA or acetoacetyl CoA are known as _________________ amino acids.
40. Amino acids that can be synthesized in the amounts needed by the body are called nonessential amino acids. Essential amino acids cannot be synthesized by the body and must be provided by food sources.
______________________ amino acids can be synthesized in sufficient quantities to meet the body’s needs.
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