MCAT metabolism Questions and Correct Answers

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MCAT metabolism Questions and Correct
Answers
Glycolysis Ans: Breakdown of 6-carbon glucose molecule into two
3-carbon molecules of pyruvate

Occurs in cytosol

Can occur with or without oxygen

10 steps

First half of glycolysis Ans: Two phosphate groups from two
different ATP molecules are added to glucose (energy input phase)

AKA 6 carbon phase

Phosphate groups are bulky and charged: trap glucose inside the
cell

They also prime the glucose, allowing the 6-carbon glucose to be
split

Second half of glycolysis Ans: Energy output phase

AKA 3 carbon phase

Two ATP produced per 3-C molecule (4 total)

One NADH produced from NAD per molecule (2 total)



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Net yield from glycolysis Ans: 2 ATP and 2 NADPH

Substrate-level phosphorylation Ans: Production of ATP by the
transfer of a phosphate molecule from a molecule to an ADP

Fructose and galactose in glycolysis Ans: Fructose and galactose
are also able to feed into glycolysis

Usually converted to glucose by liver first

Fermentation Ans: Metabolism in the absence of oxygen

Glucose undergoing anaerobic respiration

Reduction of pyruvate to ethanol (yeast and some microorganisms)
or lactic acid (human muscles and other microorganisms) in order
to restore NADH back to NAD

Ethanol/lactic acid and CO2 expelled as waste products

Yield: 2 ATP per glucose molecule

Pentose phosphate pathway Ans: Diverges and merges back with
glycolysis

Purpose: to create NADPH and some 5 carbon sugars

First half generates NADPH (various synthetic functions)

Second half (non-oxidative branch): Creates 5 C sugars

Active at all times



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