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27 Cards in this Set

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What is metabolism?

Two things...
1. Oxidize food to generate ATP

2. Converting food into other biomolecules (biosynthesis)
What is Anabolism?
BIOSYNTHESIS

-Small, simple precursors are built up into larger and more complex molecules
What is Catabolism?
DEGRADATION

-Organic nutrient molecules are converted into smaller, simpler end products
What are the 3 ways the body avoids opposing cycles of anabolism and catabolism?
1. Distinct pathways: anabolic pathways aren't just catabolic pathways ran backwards
2. Reciprocal regulation
3. Compartmentalization: physical seperation (different cellular areas)
What is reciprocal regulation?
Molecules that are active in an anabolic pathway inhibit the catabolic pathway and vice versa
What are the 2 ways in which metabolic pathways are studied?
1. Blockage of pathways by mutations or specific inhibitors are used to order the reactions
2. Tracing the fate of an added radioactive precursor molecule to identify both intermediate and order of reactions
In what three ways does blocking a pathway help determine the order of reactions?
1. Block with mutation or inhibitor
2. Accumulate intermediates prior to blockage and nothing after blockage
3. Determine order by seeing which intermediates accumulate
What are the three possible fates for glucose?
1. Storage as glycogen, starch, or sucrose
2. Pyruvate (oxidation via glycolysis)
3. Ribose 5-phosphate (biosynthetic precursor for RNA/DNA)
What is another name for glycolysis?

Where did this come form?
Embden-Meyerhof pathway

-Discovered when (Embden & Meyerhof) found glycolysis in muscle extract
Where does glycolysis occur?

How many reactions are there in glycolysis?
Glycolysis occurs in the cytoplasm

There are 10 reactions (2 sets of 5) total in glycolysis
What are the two phases of glycolysis?
1. Prepartory Phase: activate molecules, burn ATP

2. Payoff Phase: Acquire energy
What is the net production of glycolysis?

(Three sets of two...)
1. 2 pyruvate
2. 2 ATP
3. 2 NADH
Glycolysis:

What occurs in Reaction 1?
Glucose to glucose-6-phosphate
*Irreversible & regulate step

Group transfer reaction (PO₄ from ATP)

Enzyme: Hexokinase
WTF is a Kinase?
A kinase adds a phosphate by group transfer using a nucleotide as a donor
Glycolysis:

Why is reaction 1 (hexokinase) reversible?
It has an overall -ΔG’°
Glycolysis:

What occurs in Reaction 2?
Glucose 6-phosphate to fructose 6-phosphate
*Reversible step*

Isomerization (proceeds through C=C; have to open ring to linear form)

-Enzyme: Phosphohexose isomerase
What is an Isomerase?
An isomerase moves a functional group within a molecule
Glycolysis:

What occurs in Reaction 3?
Fructose 6-phosphate to fructose 1,6-biphosphate
*Irreversible & highly regulated (very important reaction)*

Group transfer

Enzyme: phosphofructokinase-1
What is phosphofructokinase-2?

What does it do?
An allosteric regulator

Makes fructose 2,6-biphosphate
Glycolysis:

What occurs in Reaction 4?
Fructose 1,6-biphosphate to dihydroxyacetone phosphate and glyceraldehyde 3-phostphate
*Reversible in vivo*

Enzyme: aldolase
-Has high positive ΔG’° but ΔG is 0
Glycolysis:

What occurs in Reaction 5?
Dihydroxyacetone phosphate to glyceraldehyde 3-phosphate

Isomerization through a C=C bond
*Reversible in vivo*

Enzyme: triose phosphate isomerase
What is the net result of the preparatory phase in Glycolysis?
2 glyceraldehyde 3-phosphate

and

2 ADP
Glycolysis:

What occurs in Reaction 6?
Glyceraldehyde + inorganic phosphate to 1,3-biphosphoglycerate (high energy compound)

Oxidation/reduction and group transfer
*Reversible in vivo

Enzyme: glyceraldhyde 3 Pi dehydrogenase
Describe the process of reaction 6

What two steps?
Two steps:
1. oxidation/reduction
2. group transfer

-Reaction proceeds through a thioester (unstable, good leaving group)
-Addition of mercury will stop the enzyme intermediate from forming
Glycolysis:

What occurs in Reaction 7?
1,3-biphosphoglycerate + ADP to
3-phosphoglycerate + ATP
*Reversible in vivo

Enzyme: phosphoglycerate kinase
-Kinase in reverse
-First ATP generating reaction: substrate level phosphorylation
Why is aresenate a dumb thing to ingest?
Arsenate is an analog to phosphate

-If you replace phosphate with aresenate in reaction 7 of Glycolysis, arsinic becomes the leaving group

-Arsinic is released instead of ATP so lose energy from glycolysis
Glycolysis:

What occurs in Reaction 8?
3-phosphoglycerate to 2-phosphoglycerate

Isomerization reaction (doesn't proceed through C=C)

2 group transfers (move phosphate from 3 to 2)
*Reversible in vivo

Enzyme: phosphoglycerate mutase