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BIOCHEM 2EE3 Lecture Notes - Lecture 13: Covalent Bond, Delayed Onset Muscle Soreness, Glucokinase

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purplehound890
8 Dec 2017
School
McMaster University
Department
Biochemistry
Course
BIOCHEM 2EE3
Professor
Boris Zhorov

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Document Summary

In this module, we will conduct an in-depth exploration of the metabolic pathways involved in energy production from the metabolism of carbohydrates. That is, the sugars that we consume in our diets or the sugars that are derived from glycogen stored in our muscle and liver. In this module, we will focus on the metabolism of glucose, but other sugars are metabolized through these same pathways. Glucose is broken down sequentially through glycolysis, then through the pyruvate dehydrogenase reaction and citric acid cycle. It is important to note that these pathways are highly regulated to control the breakdown of carbohydrates when the body needs it. Glycolysis can proceed in the absence of oxygen, that is, under anaerobic conditions. In humans, this results in lactate production, and in yeast, ethanol is generated as a bi-product of fermentation rather than lactate. Be(cid:272)ause the (cid:271)rai(cid:374)"s preferred fuel is glu(cid:272)ose, the (cid:271)ody also has the ability to synthesize glucose de novo.

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Related Questions

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 – give enzyme names (1)

c. shared between glycogen synthesis and glycogenolysis – 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)

In this week’s forum article, Nutrient Utilization in Humans: Metabolism Pathways,(http://www.nature.com/scitable/topicpage/nutrient-utilization-in-humans-metabolism-pathways-14234029) the types of molecules and the mechanisms by which the potential chemical energy in those molecules is transformed into the type of energy capable of powering cellular work is discussed. After reading the article, answer the questions listed below. ( Read the article and answer the following questions)

1. What was Antoine Lavoisier’s major contribution to our understanding of energy metabolism in living organisms?

2. Max Rubner showed that carbohydrates and proteins produce approximately 4 Kcal/g of energy when oxidized, whereas lipids generate up to 9 Kcal/g. How can this difference be explained?

3. This article points out that a major misconception, especially for many undergraduates, is that human cells only use glucose as a fuel source. In fact, all three major absorbed end products of the digestion of carbohydrates, lipids and proteins can be utilized by most cells for the generation of ATP. What serves as the major entry point (mechanism) for these different classes of molecules that makes it possible for them to serve as fuel for ATP production? Why does this mechanism not work in the absence of oxygen? Hint: consider glycolysis and fermentation.

4. Although many of the approximately 200 cell types in the human body can utilize all three major classes of food molecules for energy, not all can. Why? Provide an example.

Use the following article to answer these questions:

http://www.nature.com/scitable/topicpage/nutrient-utilization-in-humans-metabolism-pathways-14234029

1)This article points out that a major misconception, especially for many undergraduates, is that human cells only use glucose as a fuel source. In fact, all three major absorbed end products of the digestion of carbohydrates, lipids and proteins can be utilized by most cells for the generation of ATP. What serves as the major entry point (mechanism) for these different classes of molecules that makes it possible for them to serve as fuel for ATP production? Why does this mechanism not work in the absence of oxygen? Hint: consider glycolysis and fermentation.

2)Although many of the approximately 200 cell types in the human body can utilize all three major classes of food molecules for energy, not all can. Why? Provide an example.