BIOL 2083 Study Guide - Dihydroxyacetone Phosphate, Lactate Dehydrogenase, Anaerobic Glycolysis

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18 Jun 2014

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Alcoholic fermentation: the anaerobic pathway that converts glucose to ethanol. Aldolase: in glycolysis, the enzyme that catalyzes the reverse aldol condensation of fructose-1,6- bisphosphate. Anaerobic glycolysis: the pathway of conversion of glucose to lactate; distinguished from glycolysis, which is the conversion of glucose to pyruvate. Committed step: in a metabolic pathway, the formation of a substance that can play no other role in metabolism but to undergo the rest of the reactions of the pathway. Glyceraldehyde-3-phosphate: a key intermediate in the reactions of sugars. Glyceraldehyde-3-phosphate dehydrogenase: an important enzyme in glycolysis and gluconeogenesis. Glycolysis: the anaerobic breakdown of glucose to three-carbon compounds. Kinase: a phosphate-transfer enzyme, with atp as the usual source of the phosphate. Lactate dehydrogenase: an nadh-linked dehydrogenase that catalyzes the conversion of pyruvate to lactate. Phosphofructokinase: the key allosteric control enzyme in glycolysis; it catalyzes the phosphorylation of fructose-6- phosphate. Pyruvate kinase: the enzyme that catalyzes the final step common to all forms of glycolysis.

Related Questions

During glycolytic metabolism under anaerobic conditions, animals make lactate and yeast make ethanol from pyruvate. During anaerobic glycolysis, E. coli can make acetate from the pyruvate that is made from glucose. Using radical non-redox chemistry, these bacteria convert pyruvate and coenzyme A to formate and acetyl CoA using the enzyme pyruvate formate lyase. Based on your knowledge of why animals make lactate and yeast make ethanol, explain first why this enzyme is used by these bacteria rather than pyruvate dehydrogenase under anaerobic conditions. Second, explain what these acetate producing bacteria must be able to do in order to solve the problem that animals/yeast do by making lactate/ethanol (hint â itâs the âredox balanceâ problem). Finally, propose reasonable catalytic mechanisms for the next two steps in acetate production, those catalyzed by phosphate acetyltransferase and acetate kinase (include likely functional groups provided by enzymes).

1. Integrated metabolism

A. A molecule of glucose that you eat can eventually be transformed into part of a fatty acid that you store. Circle the pathways/cycles below that are part of this overall flow of carbon atoms. Cross out any that are not.

Gluconeogenesis, beta-oxidation, citric acid cycle, glycolysis, urea cycle, fatty acid synthesis

B. Trace the metabolic path of this glucose molecule through the enzymes it encounters along the way to being made into fat. Write all the enzymes in the list below into the proper places in the figure below. If the enzyme is not used, write its name in a ânot used" column. If it is used, write the enzyme in the order that the carbon atoms from glucose encounter the enzymes.

Pyruvate dehydrogenase, fumarase, aldolase, lactate dehydrogenase, pyruvate kinase, acetyl CoA carboxylase, fatty acid synthase, hexokinase, carnitine acyltransferase, ATP synthase

B. What is the minimum number of glucose molecules that would be necessary to be the carbon source for synthesis of a 16-carbon fatty acid through this pathway?

C. How many net glucose can be made from one molecule of a 16-carbon fatty acid?

2. Describe each cycle/transport system (compounds, compartments, tissues) and explain its purpose:

A. citrate transport system

B. Cori cycle

C. glucose/alanine cycle

Explain the logic of these pathway regulations:

A. Phosphofructokinase, not hexokinase, is the main regulation site of glycolysis.

B. SuccinylCoA inhibits the entry of acetyl CoA into the citric acid cycle.

C. NADH inhibits pyruvate dehydrogenase.

D. Citrate inhibits the citric acid cycle and activates acetyl-CoA carboxylase.

E. Insulin leads to activation of glycogen synthase.

ochrereindeer904

1. Consider all the pathways of carbohydrate metabolism discussed in biochemisty. List all the reactions that are:

a. unique to glycolysis (1)

b. unique to gluconeogenesis â give enzyme names (1)

c. shared between glycogen synthesis and glycogenolysis â give enzyme names (1)

2. Consider the enzyme hexokinase.

d. Hexokinase activity is regulated by glucose-6-phosphate by the process of _________________________. (1)

e. The liver isozyme of hexokinase, called glucokinase, is not susceptible to this type of regulation. Explain why this makes sense, considering the role of the

liver in maintaining the glucose balance for the organism. (2)

f. Glucokinase has a much higher Km for glucose than does hexokinase. How does this property help the liver act as a glucose storage organ? (2)

3. Lactate is a waste product in rapidly contracting muscle, but a fuel for resting muscle. Explain, with reference to the metabolic pathways through which lactate proceeds in each

case. (2)

g. When lactate is used as a fuel by muscle, how much ATP can the muscle obtain by complete oxidation of lactate? (1)

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BIOL 2083 Study Guide - Dihydroxyacetone Phosphate, Lactate Dehydrogenase, Anaerobic Glycolysis

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