Biochemistry 2280A Lecture Notes - Pentose, Gluconeogenesis, Adipocyte

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25 Aug 2013

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When blood glucose is high, the pancreas secretes insulin. Initially, the flux through glycolysis and citric acid cycle is high due to the high concentration of substrate (glucose derivatives) and insulin present. Eventually, the concentration of atp and other energy indicators of the cell increase, inhibiting glycolysis and the citric acid cycle. In this state, fatty acid synthesis, the pentose phosphate pathway and biosynthesis are favoured. When blood glucose is low, the pancreas secretes glucagon. Glucose is produced from glycogen and gluconeogenesis (from amino acids obtained from protein degradation). Adipocytes release fatty acids from storage and eventually, the liver produces ketone bodies. All of these actions occur simultaneously when the body is in the unfed state. Biosynthesis is not favoured as the focus of tissues is on energy conservation. The liver will always pump out some glucose (packaged correctly) in order to sustain the brain.

Related Questions

74) Several steps in glycolysis are highly regulated. Overallreactions of glycolysis are regulated by insulin and glucagon. Whatdo they do?

75) Calcium ion (Ca++) stimulates isocitrate to a-ketoglutarateand a-ketoglutarate to succinyl CoA reactions. Where does Ca++ comefrom?

76) Number of amino acids can participate in energy metabolism.How do protein metabolism and carbohydrate metabolismintersect?

77) During fasting, glycogenolysis starts first and then largeamount of fatty acids are released from adipose tissue into theblood. The liver receives large part of it and use for b-oxidation.As a result of b-oxidation, how gluconeogenesis is regulated?

78) Glycogenolysis is regulated by insulin to glucagon ratio.The enzyme that degrades glycogen is active when it isphosphorylated by another kinase that is active when phosphorylatedalso by PKA. How does high and low insulin-to-glucagon ratioinfluence degradation of glycogen?

salmonjackal375

16- When the body is deficient in oxaloacetate

a) acetyl CoA from the b-oxdiation pathway cannot enter the citric acid cycle

b) oxaloacetate is diverted to gluconeogenesis

c) acetyl CoA is diverted to form the ketone bodies

d) all of the above are true

e) none of the above

17- The synthesis of ketone bodies involves

a) synthesis of acetoacetyl-CoA by reversal of the thiolase reaction of fatty oxidation

b) synthesis of b-hydroxy-b-methylglutaryl-CoA (HMG-CoA)

c) cleavage of HMG-CoA to acetoacetate.

d) b-Hydroxybutyrate is produced by reduction of acetoacetate.

e) all of the above

18- Which of the statements about ketone body production is FALSE?

a) Ketone bodies are produced when there is more acetyl-CoA in the liver than can be oxidized in the citric acid cycle.

b) Ketone bodies production is not a normal process, and occurs only in diabetes or starvation

c) The ketone bodies produced in the body are the free acids and not the CoA esters.

d) When fatty acid oxidation in the liver is uncontrolled, ketone body production becomes excessive and life-threatening because these acidic compounds lower the pH of blood

e) When fatty acid oxidation

19- In which of the following ways can the 4-carbon compound acetoacetyl CoA produced in fatty acid degradation be further metabolized?

a) It can break down further to form acetyl CoA,

b) It can be converted to the ketone bodies

c) It can be used for synthesis of cholesterol and its many derivÂatives.

d) It can do all of the above

e) It can do none of the above

20- Acetyl CoA from the beta-oxidation pathway cannot enter the citric acid cycle in which of these circumstances?

a) periods of fasting

b) periods of starvation

c) diabetes

d) when the body is deficient in oxaloacetate

e) all of the above

taupemarten625

10- With respect to regulation of fatty acid metabolism chose the FALSE statement from those below?

a) ACC and FAS synthesis is stimulated by Insulin

b) ACC and FAS synthesis is stimulated by the well-fed state

c) Starvation leads to an increase in the synthesis of ACC and FAS.

d) Adipose tissue levels of lipoprotein lipase also are increased by insulin and decreased by starvation.

e) The long-term regulation of fat metabolism is achieved by alteration of the rate of enzyme synthesis and turn-over

14-With respect to the clinical significance of ketogenesis, which of the statements below are FALSE?

a) The Ketone bodies are relatively strong acids

b) The increase of ketone bodies in the blood lowers the pH of the blood.

c) The acidification of the blood by an increase of ketone bodies in the blood is dangerous because it impairs the ability of hemoglobin to bind oxygen

d) A severe increase of ketone bodies in the blood occurs in untreated insulin-dependent diabetes mellitus.

e) none of the above

15-With respect to ketogenesis, which statement below is FALSE?

a) Acetoacetate and b-hydroxybutyrate are major substrates for the biosynthesis of neonatal cerebral lipids.

b) In early stages of starvation, the heart and skeletal muscle consumes primarily ketone bodies to preserve glucose for use by the brain.

c) The fate of the products of fatty acid metabolism is determined by an individual's physiological status.

d) Ketogenesis takes place only in the liver.

e) all of the above

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Biochemistry 2280A Lecture Notes - Pentose, Gluconeogenesis, Adipocyte

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