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MCAT Biology Review I
Molecular Biology: Enzymes and Metabolism (Enzyme Structure and Function, Control of Enzyme Activity, and Basic Metabolism) KREB'S CYCLE AND E.T.C. NOT FULLY COVERED
16
Medical
Undergraduate 2
01/03/2010

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Term
Lock and Key Analogy.
Definition
Just as a uniquely shaped key will fit into, and open, a lock, a substrate (the key) acts the same with the active site on an enzyme (the lock). The wrong "key" may fit into the lock but nothing will happen because the shapes do not match.
Term
Define Enzyme Specificity.
Definition
Due to an enzyme's functional shape, its substrate binds only at a unique location on the enzyme's surface called the active site where the chemical action occurs. The Lock & Key analogy is used to explain the phenomenon.
Term
Definition and function of an enzyme.
Definition
Enzymes are globular proteins that participate in cellular metabolic processes. Their main function is to enhance the rate of a reaction by lowering the activation energy (Ea). On a similar thought, enzymes can induce a reaction to occur that otherwise would not occur by lowering the energy of activation to an "affordable" level for the cells.
Term
Define Feedback Inhibition.
Definition
A cellular control mechanism by which an enzyme that regulates a reaction is inhibited when the produced substance has accumulated to a certain density, thereby keeping an overall sort of balance.
Term
Define Competitive Inhibition.
Definition
A cellular control mechanism in which competitive inhibitors (a.k.a. analogues) chemically mimic the true substrate close enough to fit into the active site of an enzyme, however, these competitive inhibitors do not activate the enzyme (as if putting in a second key that fits inside the lock but cannot open the door).
Term
Define Noncompetitive Inhibition.
Definition
A cellular control mechanism that is classified into two subcategories, specific and non-specific. Nonspecific inhibitors inhibit a lot of different enzymes by methods such as denaturing them (some nonspecific inhibitors include heavy metals (iron, nickel, mercury, cadmium), cyanide, and carbon monoxide). Specific noncompetitive inhibitors are organic molecules (or allosteric inhibitors) bind to the active site and influence the enzyme. However, sine the allosteric inhibitors are not permanently bound to the active site, the allosteric effect is reversible and the enzyme may resume it's function at a later time (used for homeostasis).
Term
Define Cofactors.
Definition
SMALL molecules that enzymes sometimes require in order to function properly. There are two types of cofactors, organic (a.k.a. Vitamins) and inorganic (a.k.a. Minerals). Cofactors act like "gofers" for the enzyme, carrying pieces of molecules from one place to another (molecules such as methyl groups, electrons, and protons).
Term
Define the net reaction for glycolysis.
Definition

 

 

Glucose + 2 ADP + NAD+ → 2 Pyruvic Acid + 2 NADH + 2 ATP 

Term

Label the correct terms on the glycolysis diagram


Glucose (C6H12O6)

          ↓←2 ATP

           ↓→ 2 ADP

(A)

↓  ↓

(B)    (B)

 2 (C)→↓        ↓← 2 (C)

2 NADH ←↓        ↓→ 2 NADH

2 ADP →↓        ↓← 2 ADP

2 (D) →↓        ↓→ 2 (D)

 (E)       (E)

Definition

Glucose (C6H12O6)

          ↓←2 ATP

           ↓→ 2 ADP

(Fructose Diphosphate)

↓  ↓

(PGAL)  (PGAL)

 2 (NAD+)→↓        ↓← 2 (NAD+)

2 NADH ←↓        ↓→ 2 NADH

2 ADP →↓        ↓← 2 ADP

2 (ATP) →↓        ↓→ 2 (ATP)

 (Pyruvic Acid) (Pyruvic Acid)

Term
Glycolysis occurs where in the cell?
Definition
Glycolysis occurs in the cytoplasm of the cell.
Term
How many net ATP and NADH are gained by glycolysis?
Definition
2 ATP and 2 NADH
Term
Formation of Acetyl CoA occurs where in the cell?
Definition
The Formation of Acetyl CoA occurs in the matrix of the mitochondria.
Term
Formation of Acetyl CoA occurs where in the cell?
Definition
The Formation of Acetyl CoA occurs in the matrix of the mitochondria.
Term
There is a net gain of how many NADH and carbon dioxide molecules by the formation of Acetyl CoA?
Definition
2 NADH and 2 carbon dioxide
Term

Label the correct terms for the Formation of Acetyl CoA

 

2 (A)

           ↓→ 2 (B)

   2 (C) →↓

    2 (D) ←↓              

                     ↓← (E)

 2 (F)

Definition

2 Pyruvate

            ↓→ 2 CO2

2 NAD→↓

2 NADH ←↓              

                     ↓← Coenzyme A

 2 acetyl CoA

Term
How many net ATP, NADH, and FADH2 are gained by the citric acid cycle?
Definition

 3 NADH, 12 ATP, and 1 FADH

( 3 ATP result for every NAD+ to NADH and 2 ATP result for every FAD to FADH2)

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