Unit 3

Glucose binds an enzyme involved in its production and decreases the activity of that pathway. What type of metabolic regulation is taking place?

allosteric regulation

The biosynthesis of triacylglycerols from acetate occurs mainly

after ingestion of excess carbohydrate.

Glutamate and pyruvate are reactants in a transamination reaction that results in the formation of:

alanine and alpha-ketoglutarate

When triacylglycerols are hydrolyzed, the fatty acids that are released are most often used

as a substrate for the citric acid cycle for energy production

All of the amino acids can be used as precursors for gluconeogenesis.

false

Bile acids are more hydrophobic than cholesterol.

false

Mammals can synthesize all 20 amino acids.

false

During times of fasting, which type of 'fuel molecule' do liver cells use to generate energy for its own use?

fatty acids

Which of the following hormones will stimulate glycogen breakdown?

glucagon

Glycogen is directly converted to monosaccharide units by:

glycogen phosphorylase

What amino acids is derived from the glycolysis intermediate 3-phosphoglycerate?

serine

A mutation in GLUT4 changes the Kt value from 5 mM (wild type) to 3 mM (mutant). The velocity of glucose entry into a mutant cell would be higher than a cell expressing the wild type version at a blood glucose concentration of 5mM.

true

In prolonged fasting conditions acetyl-CoA generated from the breakdown of amino acids and fatty acids does not enter the citric acid cycle in the liver, but acetyl-CoA derived from ketone bodies can enter the citric acid cycle in the brain.

true

Salvage pathways in nucleotide synthesis utilize preformed bases (pyrimidines and purines) recovered from nucleic acid breakdown, to attach to an activated PRPP.

true

Treatment for a person with Type I diabetes includes periodic injections of insulin.

true

Which molecules in the pentose phosphate pathway is also an intermediate in glycolysis?

- Glyceraldehyde 3-phosphate - Fructose 6-phosphate

Cells that have a high level of reactive oxygen species would need which of the following pathway(s) to be active in order to reduce the high level of oxidative stress? A. Oxidative Phase of PPP B. Non-Oxidative Phase of PPP C. Glycolysis D. Gluconeogenesis

A, B, D

Fatty acid synthesis requires which of the following molecules?

ATP / NADPH

Anabolic (biosynthesis) pathways in animals use the following to produce large biomolecules:

ATP and NADH/NADPH

In beta cells of the pancreas, closure of which of the following membrane proteins results in the eventual release of insulin?

ATP-gated K+ channel

Which of the following is the rate-limiting enzyme in fatty acid synthesis?

Acetyl-CoA carboxylase

Which of these statements about eicosanoid synthesis is true? - Aspirin acts by blocking the synthesis of arachidonate - Arachidonate is derived mainly by hydrolysis of triacylglycerols - An early step in the path to thromboxanes is blocked by ibuprofen - Plants can synthesize prostaglandins, but humans cannot

An early step in the path to thromboxanes is blocked by ibuprofen

What is a substrate of ribonucleotide reductase?

GDP

If a drug that was an inhibitor of PP1 activity was ingested by a person, then which of the following would occur?

Glycogen phosphorylase would remain phosphorylated and retain some activity.

Which reaction of glycolysis is bypassed in gluconeogenesis by using two enzymes?

Phosphoenolpyruvate (PEP) to pyruvate

What happens upon eating a carbohydrate-rich meal?

Phosphoprotein phosphatase 1 (PP1) is activated by insulin and de-phosphorylates acetyl-CoA carboxylase, resulting in the production of malonyl-CoA

Which of the following types of regulation is considered the major way liver cells activate glycogen phosphorylase?

Post translational modification

Tetrahydrofolate is important for the activity of which enzyme?

Thymidylate synthase

What is the main function of VLDL particles?

To transport triacylglycerols to adipose and muscle tissue.

Cellulose and glycogen are both homopolymers of glucose units. Humans cannot digest cellulose, but can break down glycogen into individual glucose units. Which type of enzyme is lacking in humans that would allow them to break down cellulose?

beta-glucosidase remember: the glycosidic bonds within cellulose are beta-1,4-glycosidic bonds, which would require a glucosidase that can bind that bond in order to catalyze the breakage of that bond

Which of the following statements regarding lipoproteins is INCORRECT? - Of the four main classes of lipoproteins, chylomicrons contain the highest percentage of triacylglycerols. - The four main classes of lipoproteins are chylomicrons, VLDL, LDL and HDL. - Lipoproteins have proteins embedded in their phospholipid bilayer. - Of the four main classes of lipoproteins, LDL contains the highest percentage of cholesteryl esters.

correct: - Of the four main classes of lipoproteins, LDL contains the highest percentage of cholesteryl esters. - The four main classes of lipoproteins are chylomicrons, VLDL, LDL and HDL - Of the four main classes of lipoproteins, chylomicrons contain the highest percentage of triacylglycerols. incorrect: - Lipoproteins have proteins embedded in their phospholipid bilayer.

Which of the following statements regarding hypercholesterolemia is INCORRECT? - People with hypercholesterolemia can develop lipid deposits on the hands and face. - The disease may result from genetic variants in the LDL receptor. - Plasma cholesterol levels are higher for heterozygotes than for homozygotes.

correct: - People with hypercholesterolemia can develop lipid deposits on the hands and face. - The disease may result from genetic variants in the LDL receptor. incorrect: - Plasma cholesterol levels are higher for heterozygotes than for homozygotes.

Which of the following statements regarding glucose 6-phosphate dehydrogenase is INCORRECT? - Glucose 6-phosphate dehydrogenase reduces NADP+. - High levels of NADPH activate Glucose 6-phosphate dehydrogenase - The NADPH produced by glucose 6-phosphate dehydrogenase can be used to combat oxidative damage, synthesize fatty acids or synthesize cholesterol. - Glucose 6-phosphate dehydrogenase deficiencies are most prevalent in areas afflicted with malaria.

correct: - The NADPH produced by glucose 6-phosphate dehydrogenase can be used to combat oxidative damage, synthesize fatty acids or synthesize cholesterol. - Glucose 6-phosphate dehydrogenase deficiencies are most prevalent in areas afflicted with malaria. - Glucose 6-phosphate dehydrogenase reduces NADP+. incorrect: - High levels of NADPH activate Glucose 6-phosphate dehydrogenase

What is the cellular location for fatty acid synthesis in animal cells?

cytosol

Which of the following statements regarding deoxy-nucleoside triphosphate synthesis is CORRECT? - dATP can inhibit ribonucleotide reductase through feedback inhibition - In the cell, ribonucleotide reductase catalyzes the formation of ribonucleotides from deoxyribonucleotides. - The substrates for ribonucleotide reductase are AMP, CMP, GMP, and UMP - UTP is synthesized from CTP.

dATP can inhibit ribonucleotide reductase through feedback inhibition

You finish eating a large, diverse meal that includes carbohydrates, fats, and proteins. You measure your blood glucose levels one hour later. The concentration of glucose is within the hyperglycemic range. What does hyperglycemia mean and which hormone would the pancreas release in response?

high blood glucose; insulin

Which of the following statements regarding gluconeogenesis is INCORRECT?

incorrect: Cellular conditions do not exist that allow lactate dehydrogenase to catalyze the formation of pyruvate from lactate. correct: - When gluconeogenesis is occurring, the levels of oxaloacetate in the liver are greatly diminished because it is being used as a precursor in gluconeogenesis. - Cellular conditions do not exist that allow pyruvate dehydrogenease to catalyze the formation of pyruvate from acetyl-CoA.

Which of the following statements regarding fructose 2,6-bisphosphate (F26bP) is INCORRECT?

incorrect: Fructose 2,6-bisphosphate (F26bP) is formed when fructose 1,6-bisphosphatase-1 (FBPase-1) removes the phosphate from the 1' position of fructose 1,6-bisphosphate. correct: - Fructose 6-phosphate is formed when Fructose 2,6-bisphosphatase (FBPase-2) removes a phosphate from the 2' position of fructose 2,6-bisphosphate (F2,6-bP). - Fructose 2,6-bisphosphate (F26bP) is not a member of the glycolysis or gluconeogenesis pathway, but it is a regulator of the pathways.

Which of the following hormones will stimulate glycogen synthesis?

insulin

What is the cellular location of triacylglycerols when stored?

lipid droplet