Chapter 25: Metabolism

The breakdown of glucose to pyruvate is an _________ process.

Anaerobic & Oxidative

The citric acid cycle must turn ____ times to completely metabolize the pyruvate produced from one glucose molecule.

2

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

Absorptive

Charlies 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?

Based just on the information given, Charlie would appear to be in good health, at least relative to his diet and probable exercise. Problems are associated with elevated levels of LDLs, which carry cholesterol to peripheral tissues and make it available for the formation of atherosclerotic plaques in blood vessel.s High levels of HDLs indicate that a considerable amount of cholesterol is being removed from the peripheral tissues and carried to the liver for disposal. You would encourage Charlie not to change, and keep up the good work.

How do the absorptive and post absorptive state maintain normal blood glucose levels?

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

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

In lipid catabolism, a triglyceride is hydrolyzed, yielding glycerol and fatty acids. Glycerol is converted to pyruvate and enter the citric cycle. Fatty acids are broken into 2-carbon fragments by beta-oxidation inside mitochondria. The 2-carbon compounds then enter the citric acid cycle.

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

It appears that Jill is suffering from ketoacidosis as a consequence of her anorexia. Because she is literally starving herself, her body is metabolizing large amounts of fatty acids and amino acids to provide energy, and i the process is producing large quantities of ketone bodies (normal metabolites from these catabolic processes). One of the ketones formed is acetone, which can be eliminated through the lungs. Acetone has a fruity aroma, so her breath would also smell fruity. The ketones are also converted into ketonuria acids such as acetic acid. In large amounts, this lowers the body's pH. This is probably the cause of her arrhythmias.

What is a lipoprotein? What are the major groups of lipoproteins and how do they differ?

Lipoproteins are lipid-protein complexes that contain large insoluble glycerides and cholesterol, with a superficial coating of phospholipids and proteins. The major groups are chylomicrons, which consist of 95% triglyceride, are the largest lipoproteins, and carry absorbed lipids from the intestinal tract to the bloodstream; very low density lipoproteins (VLDLs), which consist of triglyceride, phospholipid, and cholesterol, and transport triglycerides to peripheral tissues; intermediate-density lipoproteins (IDLs), which are intermediate in size and composition between VLDLs and LDLs; low-density lipoproteins (LDLs, or "bad cholesterol"), which are mostly cholesterol and deliver cholesterol to peripheral tissues; and high-density lipoproteins (HDLs, or "good cholesterol"), which are equal parts protein and lipid (cholesterol and phospholipids) and transport excess cholesterol to the liver for storage or excretion in bile.

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

Liver cells can break down or synthesize most carbohydrate, 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.

Catabolism

The breakdown of organic substrates

Triglycerides

The largest metabolic reserves for the average adult are stored as these.

Oxidative Phosphorylation

The process that produces more than 90% of the ATP used by our cells.

Beta Oxidation

The sequence of reactions responsible for the breakdown of fatty acid molecules m.

Fat Soluble Vitamins

The vitamins generally associated with vitamin toxicity

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.

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

Why are vitamins and minerals essential components of the diet?

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

What is oxidative phosphorylation? Explain how the electron transport system is involved in this process.

What is oxidative phosphorylation? Explain how the electron transport system is involved in this process. Oxidative phosphorylation is 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 (metalloproteins) called cytochromes, embedded in the inner mitochondria membrane. Energy from the stepwise passage of electrons (from H atoms) along the cytochrome molecules is used to pump hydrogen ions from the matrix into the intermembrane space. This forms a proton gradient across the inner mitochondrial membrane. The hydrogen ions diffused back through ATP synthase and generate ATP. The electrons, hydrogen ions, and oxygen combine to produce water as a byproduct.