L12: Intro to Metabolism

Question 1

Why form reducing agents? Or: What are the roles of reduced electron carriers?

Answer 1

• Generation of ATP via oxphos - Biosynthesis

Question 1

What are the reducing agents formed during catabolic reactions?

Answer 1

• NADH, NADPH, FADH2, FMNH2

Question 1

What reducing agents are used to produce more ATP in oxphos?

Answer 1

• NADH, FADH2 and FMNH2

Question 2

What are ways that ATP is generated?

Answer 2

• Oxidative phosphorylation - Substrate-level phosphorylation

Question 3

How is anabolism linked to catabolism?

Answer 3

• Anabolism uses the following products formed during catabolism to proceed in its biosynthetic reactions: - A.) ATP - B.) reducing agents - C.) small precursor molecules

Question 4

What is the primary reducing agent used in anabolic biosynthetic reactions?

Answer 4

• NADPH

Question 5

What are key metabolic intermediates that tie anabolic and catabolic pathways together?

Answer 5

• Acetyl-CoA - Glucose-6-phosphate - Pyruvate - CAC (citric acid cycle) intermediates

Question 7

What are important roles of catabolism?

Answer 7

• Conversion of free energy into ATP - Formation of reducing agents (electron carriers) - Creation of smaller products for precursors in anabolism (eg. Pyruvate/lactate)

Question 8

What is the importance of Acetyl-CoA?

Answer 8

• It is a key integrator of pathways involving all 3 macronutrients.

Question 9

Define metabolism. What are two major types of pathways?

Answer 9

• Metabolism is defined as the sum of all the biochemical reactions in a living system. - A.) Catabolic pathway: degradative pathway that take larger molecules and degrade them into smaller components. - B.) Anabolic pathway: biosynthetic pathway that convert small precursors into larger molecules.

Question 9

Why type of reactions play a role in releasing free energy in catabolism?

Answer 9

• Oxidation reactions (OIL = oxidation removes electrons)

Question 10

How do newborns become riboflavin deficient?

Answer 10

• If a newborn is jaundiced, treatment requires use of “bili-lights”. As riboflavin is light-sensitive, newborns become riboflavin deficient.

Question 10

What deficiency results from the treatment of jaundiced newborns with bili-lights? Why?

Answer 10

• Riboflavin deficiency. Riboflavin is light-sensitive.

Question 13

In what forms can electrons be removed during metabolic processes?

Answer 13

• Free, naked electron (Fe2+ – Fe3+ + e-) - Hydrogen atom (electron plus protein, denoted as Hdot) - Hydride ion (hydrogen atom with extra electron, H:- formed when 2Hdot – hydride + hydrogen proton)

Question 14

What is pellagra?

Answer 14

• Deficiency in niacin, leading to diarrhea, dementia, dermatitis and death.

Question 15

What are two important B vitamins and what are their roles in metabolism?

Answer 15

• Niacin (aka B3): part of structure of NAD+ (oxidized and reduced) and NADP+ (oxidized and reduced). - Riboflavin (aka B2): part of structure of FAD and FMN (reduced and oxidized forms).

Question 16

What does a niacin deficiency lead to?

Answer 16

• Pellagra, which has symptoms of 4 Ds (diarrhea, dementia, dermatitis, death)

Question 18

Catabolic and anabolic processes are intimately coupled. How do the ratios of these processes change during fasting/starvation and a well-fed state? Provide examples.

Answer 18

• Catabolic processes are enhanced / increased during fasting/starvation state. Glycogen, fats and proteins are broken down. - Anabolic processes are enhanced / increased during the well-fed state. Glycogen, fats and protein are biosynthesized.

Question 19

What are some mechanisms used to regulate activity of metabolic reactions/pathways?

Answer 19

• Substrate availability - Regulation of enzyme activity (allosteric effects, reversible phosphorylation, regulatory subunits, zymogen activation) - Compartmentalization - Regulation of enzyme concentration via gene expression