Metabolism & Energetics - Chapter 25

Question 1

Catabolism refers to

Answer 1

the breakdown of organic substrates.

Question 2

The breakdown of glucose to pyruvate is an _______ process.

Answer 2

Anaerobic and Oxidative

Question 3

The process that produces more than 90 percent of the ATP used by our cells is:

Answer 3

Oxidative Phosphorylation

Question 4

The sequence of reactions responsible for the breakdown of fatty acid molecules is

Answer 4

Beta-Oxidation

Question 5

The citric acid cycle must turn _______ time(s) to completely metabolize the pyruvate produced from one glucose molecule.

Answer 5

2

Question 6

The largest metabolic reserves for the average adult are stored as:

Answer 6

Triglycerides

Question 7

The Vitamins generally associated with vitamin toxicity are

Answer 7

Fat Soluble Vitamins

Question 8

What is a lipoprotien?

Answer 8

lipid-protein complexes that contain large, insoluble glycerides and cholesterol with a superficial coating of phospholipids and proteins.

Question 9

What are the major groups of lipoprotiens and how do they differ?

Answer 9

1. Chylomicrons - largest lipid proteins, consist of 95% triglyceride, and carry absorbed lipids from the intestinal tract to the blood stream.
2. VLDLs (Very Low Density Lipoproteins) - consistof triglyceride, phospholipid, and cholesterol. They transport triglycerides to peripheral tissues
3. IDLs (Intermediate-density Lipoproteins) are intermediate in size and composition between VLDLs and LDLs.
4. LDLs (Low-Density Lipoproteins) are bad cholesterol, mostly cholesterol and deliver cholesterol to peripheral tissues.
5. HDLs (HIgh Density Lipoproteins are GOOD cholesterol and are equal parts protein and lipid (cholesterol and phospholipids). They transport exces cholesterol to the liver for storage or excretion in bile.

Question 10

What is oxidative phosphorylation?

Answer 10

The generation of ATP within mitochondria, through a process called ‘chemiosmosis’ that requires coenzymes, ATP synthase, and consumes oxygen. The electron transport system consists of a sequence of metal ion-containing proteins called cytochromes, embedded in the inner mitochondral membrane. Energy from the stepwise passage of electrons along the cytochrome molecules is used to pump hydrogen ions from the matric into the intermembrane space. This forms a proton gradient across the inner mitochondrial membrane. The hydrogen ions diffuse back through ATP synthase and generate ATP. The electrons, hydrogen ions, and oxygen combine to produce water as a byproduct.

Question 11

What is oxidative phosphorylation?

Answer 11

The generation of ATP within mitochondria, through a process called ‘chemiosmosis’ that requires coenzymes, ATP synthase, and consumes oxygen. The electron transport system consists of a sequence of metal ion-containing proteins called cytochromes, embedded in the inner mitochondral membrane. Energy from the stepwise passage of electrons along the cytochrome molecules is used to pump hydrogen ions from the matric into the intermembrane space. This forms a proton gradient across the inner mitochondrial membrane. The hydrogen ions diffuse back through ATP synthase and generate ATP. The electrons, hydrogen ions, and oxygen combine to produce water as a byproduct.

Question 12

Explain how the electron transport system is involved in the process of oxidative phosphorylation.

Answer 12

A triglyceride is hydrolyzed, yielding glycerol and fatty acids. Glycerol is converted to pyruvate and enters the citric acid cycle. Fatty acids are broken into 2-carbon compounds then enter the citric acid cycle.

Question 13

11. How are lipids catabolized in the body? How is beta-oxidation involved in lipid catabolism?

Answer 13

In lipid catabolism, a triglyceride is hydrolyzed, yeilding glycerol and fatty acids. Glycerol is converted into pyruvate and enters the citric acid cycle. Fatty acids are broken into 2 -carbon compounds then enter the citric acid cycle.

Question 14

12. How do the absorptive and postabsorptive states maintain normal blood glucose levels?

Answer 14

During the absorptive state, insulin prevents a large surge in blood glucose after a meal by causing the liver to remove glucose from the hepatic portal circulation. During the postabsorptive state, blood glucose begins the decline, triggering the liver to release glucose produced through glycogenolysis.

Question 15

13. Why is the liver the focal point for metabolic regulation and control?

Answer 15

Liver cells can break down or synthesize most carbohydrates, lipids, and amino acids. Because the liver has an extensive blood supply, it can easily monitor blood composition of these nutrients and regulate them accordingly. The liver also stores energy in the form of glycogen.

Question 16

14. Why are vitamins and minerals essential components of the diet?

Answer 16

Vitamins and minerals are essential components of the diet because the body cannot synthesize most of the vitamins and minerals it requires.

Question 17

15. Some articles in the popular media refer to ‘good cholesterol’ and ‘bad cholesterol.’ To which types and functions of cholesterol do these terms refer? Explain your answer.

Answer 17

These terms refer to lipoproteins in the blood that transport cholesterol. “Good cholesterol” (high-density lipoprotiens) which transports excess cholesterol to the liver for storage or breakdown, whereas “bad cholesterol”, LDLs trasport cholesterol to peripheral tissues… which unfortunately may include the arteries. The buildup of cholesterol in the arteries is linked to cardiovascular disease.

Question 18

When blood levels of glucose, amino acids, and insulin are high, and glycogenesis is occurring in the liver, the body is in the _______ state.

Answer 18

Absorptive

Question 19

Charlie has a blood test that shows a normal level of LDLs but an elevated level of HDLs in his blood. Given that his family has a history of cardiovascular disease, he wonders if he should modify his lifestyle. What would you tell him?

Answer 19

Not to change his diet and keep up the good work. High level of HDL’s indicate that cholesterol is being removed at a considerable rate.

Question 20

Jill suffers from anorexia nervosa. One afternoon, she is rused to the emergency room because of cardiac arrhythmia’s. Her breath smells fruity and her blood and urine samples contain high levels of ketone bodies. Why do you think she is having the arrhythmia?

Answer 20

She is suffering from Ketoacidosis.

Starvation causes the body to metabolize large amounts of fatty acids and amino acids to provide energy. In that process, the body is producing large quantities of ketone bodies.

One of the ketones formed is acetone, which can be eliminated through the lungs. Aceton has a fruity aroma, so her breath would smell fruity.

Ketones are also convered into keto acids, like acetic acid. In large amounts, this lowers the body’s pH which can cause arrhythmias.