Chapter 19

28. What is metabolic syndrome?

Metabolic syndrome describes a set of symptoms, including obesity and insulin resistance, that appear to be related"

8. What is the purpose of the glucose/alanine cycle?

Muscle proteins break down during excercis The net effect of the glucose-alanine cycle is to transport nitrogen from muscles to the liver.

27. Although diabetes is a disorder of glucose metabolism, it is also a disorder of _______.

fat metabolism

1. Give an example of how cellular compartmentalization achieves regulation of reciprocal metabolic pathways.

fatty acid oxidation occurs in the mitochondria, but fatty acid synthesis takes place in the cytosol.

25. When cells fail to take up glucose, the body's metabolism responds as if no glucose were available, so liver ______ increases.

gluconeogenesis

26. How does hyperglycemia lead to tissue damage?

glycosylation of proteins

4. How are skeletal and heart muscle different in terms of metabolism?

heart muscle, which maintains a near-constant level of activity, is specialized to burn fatty acids as its primary fuel and is rich in mitochondria to carry out this aerboic activity. For skeletal muscle, muscles use glycogen and break it down to glucose and go thru glycolysis for ATP production. Muscle cells can also burn fatty acid and ketone bodies.

20. What is the mechanism by with high [AMP]/[ATP] ratio activates ATP generating catabolism?

AMP equals needs energy so activates AMPK to produce ATP

23. What is the role of "brown fat" in obesity?

Brown fat has high mitochondrial content; it is perhaps relevant to the ability of individuals to burn off rather than store excess metabolic fuel.

2. LIVER: After a meal, where do carbohydrates get stored? Where do excess carbohydrates and amino acids get stored? Where do fatty acids get stored?

Carbohydrates are primary converted to glycogen for storage. Excess glucose and amino acids are catabolized to acetyl-CoA, which is used to synthesize fatty acids. The fatty acids are esterified to glycerol, and the resulting triacylglycerols, along with dietary triacylglycerols, are exported to other tissues.

3. During a fast, what is the role of the liver in releasing fuels?

During a fast, the liver mobilizes glucose from glycogen stores and releases it into circulation for other tissues to use. Triacylglycerols are broken down to acetyl-CoA, which can be converted to ketone bodies to power the brain and heart when glucose is in short supply.

7. What is the purpose of the Cori cycle?

During periods of high activity, muscle glycogen is broken down into glucose, which undergoes glycolysis to produce the ATP required for muscle contraction. The resulting lactate excreted through the bloodstream to the liver, where it goes through gluconeogenesis. Then, the new glucose goes back to the muscle for ATP production. So overall, The cori cycle transfers free energy from the liver to the muscles.

10. In what tissue(s) is hexokinase replaced by glucokinase? What is the difference in the isozymes, and why is it metabolically important?

Hexokinase is replaced by glucokinase in liver and pancreatic B cells.

12. how does inulin activate glucose uptake by muscle and adipose? How does it signal triacylglyceride uptake?

Insulin increases the number of transporters at the cell surface (called GLUT4) in order to activate glucose intake into muscle and adipose tissues. The translocation of transporters to the cell surface increases the rate at which glucose enters the cell. Insulin stimulates fatty acid uptake as well as glucose uptake. When the hormone binds to its receptors in adipose tissue, it activates the extracellular protein lipoprotein lipase, which helps remove fatty acids from criculate lipoproteins so they can be taken up for storage by adipocytes.

11. Insulin signals fuel abundance by decreasing ______________ while promoting _________.

Insulin signals fuel abundance by decreasing metabolism of stored fuel while promoting fuel storage.

9. Insulin stimulates activities such as _______ and inhibits processes such as _____________.

Insulin stimulates glucose uptake and inhibits process such as glycogen breakdown.

21. During a fast, amino acids are made into glucose. How does the body avoid using up all its proteins?

It switches gradually form glucose to ketone bodies

5. What other organ, besides the liver, does gluconeogenesis? Why?

Kidney; The removal of groups from glutamine leaves alpha-ketoglutarate, which can be converted to glucose.

22. What hormone helps to set the set-point? Why is it hard to maintain weight loss?

Leptin helps to set the set-point. It is hard to maintain weight loss because a high-set point previously established from leptin concentration may influence the weight to return to the high level.

14. Phosphorylation ____________________ glycogen synthase and _________________ glycogen phosphorylase.

Phosphorylation deactivates glycogen synthase and activates glycogen phosphorylase. So what does dephosphorylation do?

19. Leptin is a hormone produced by adipose that has what effect?

Suppresses appetite.

6. Why might it be advantageous for cancer cells to obtain must ATP by glycolysis rather than oxidative phosphorylation.

They can ovide generating O2'- radical, which could cause DNA damage. Also, directing citric acid more toward producing precursors of fatty acids, amino acids, and nucleotides can help cells divide.

24. What is the cause of type-1 diabetes? How is type-2 diabetes different?

Type 1 diabetes is an autoimmune disease in which the immune system destroys pancreatic B cells. As a result, insulin production drops off.