MDS PREP
The biochemical defect in Osteogenesis Imperfecta, type II is:
1. a mutation in the alpha 1 chain of Type I collagen.
2. a deficiency in collagenase.
3. a deficiency in lysyl oxidase.
4. a deficiency in lysyl hydroxylase.
Biochemistry
Answer: 4
The biochemical defect in Osteogenesis Imperfecta, type II is a deficiency in lysyl hydroxylase.
An alpha helix of a protein is most likely to be disrupted if a missense mutation introduces the following armino acid within the alpha helical structure:
1. Alanine.
2. Aspartic acid.
3. Tyrosine.
4. Glycine.
Glycine and proline introduce a bend in structure of protein, hence alpha helix disrupted
Approximately 3 hours following a well-balanced meal, blood levels of which of the following are elevated?
1) Fatty acids
2) Glucagon
3) Glycerol
4) Chylomicrons
Biochemistry Answer: 4
Following digestion, the products of digestion enter the bloodstream.
These include glucose, amino acids, triacylglycerides packaged into chylomicrons from the intestine, and very low density lipoproteins from the liver.
The hormone of anabolism, insulin, is also elevated because of the signaling of the glucose and amino acids in the blood, which allows release of insulin from the β-cells of the pancreas. Insulin aids the movement of glucose and amino acids into cells. In contrast, all the hormones and energy sources associated with catabolism are decreased in the blood during this time. Long-chain fatty acids and glycerol released by lipolysis from adipocytes are not elevated. Glucagon and epinephrine are not released. The only time glucose levels rise significantly above approximately 80 mM is following a well-balanced meal when glucose is obtained from the diet. The concentration of glucose reaches a peak 30 to 45 minutes after a meal and returns to normal within 2 hours after eating. This response of blood glucose after eating (mimicked by giving 50 g of oral glucose) is the basis for the glucose tolerance test. In the event of insulin deficiency (diabetes mellitus), the peak glucose concentration is abnormally high and its return to normal is delayed.
The concentration of ketones is increased in body due to:
1. Starvation
2. High fat diet
3. Diabetes mellitus
4. All of the above
Biochemistry
Answer: 4
The concentration of ketones is increased in body due to:
1. Starvation
2. High fat diet
3. Diabetes mellitus
Prothrombin production in the liver is dependent upon an adequate dietary supply of
1 Vitamin A
2 Vitamin E
3 Vitamin K
4 None of the above
Biochemistry
Answer: 3
Prothrombin production in the liver is dependent upon Vitamin K intake
The rate limiting step in glycolysis is catalyzed by:
1. Hexokinase
2. Phosphofructokinase
3. Enolase
4. Pyruvate kinase
Biochemistry
Answer: 2
The rate limiting step in glycolysis is catalyzed by Phosphofructokinase
Glutamate-pyruvate trans-aminase is predominantly present In:
1. Skeletal muscle
2. Cardiac muscle
3. Brain
4. Liver
Biochemistry
Answer: 4
Glutamate-pyruvate trans-aminase is predominantly present In Liver
Which of the following enzymes is active in adipocytes following a heavy meal?
1) Glycogen phosphorylase
2) Glycerol kinase
3) Hormone-sensitive triacylglyceride lipase
4) Phosphatidate phosphatase
Biochemistry Answer: 4
The enzyme phosphatidate phosphatase converts phosphatidic acid to diacylglycerol during synthesis of triacylglycerides.
The function of adipose tissue is the storage of fatty acids as triacylglycerols in times of plenty and the release of fatty acids during times of fasting or starvation.
Fatty acids taken in by adipocytes are stored by esterification to glycerol-3-phosphate. Glycerol-3-phosphate is derived almost entirely from the glycolytic intermediate dihydroxyacetone phosphate through the action of glycerol-3-phosphate dehydrogenase. Glycolytic enzymes are active in adipocytes during triglyceride synthesis, but those of glycogen degradation (low levels in adipocytes) and gluconeogenesis (ie, glucose-6-phosphatase) are not.
Glycerol kinase is not present to any great extent in adipocytes, so that glycerol freed during lipolysis is not used to reesterify the fatty acids being released.
The enzyme triacylglyceride lipase is turned on by phosphorylation by a cyclic AMP-dependent protein kinase following epinephrine stimulation.