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MCAT metabolism Questions with
Detailed Verified Answers
Question: Glycolysis
Answer: Breakdown of 6-carbon glucose molecule into two 3-carbon
molecules of pyruvate
Occurs in cytosol
Can occur with or without oxygen
10 steps
Question:
First half of glycolysis
Answer: 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
Question:
Second half of glycolysis
Answer: 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)
Question:
Net yield from glycolysis
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Answer: 2 ATP and 2 NADPH
Question:
Substrate-level phosphorylation
Answer: Production of ATP by the transfer of a phosphate molecule from a
molecule to an ADP
Question:
Fructose and galactose in glycolysis
Answer: Fructose and galactose are also able to feed into glycolysis
Usually converted to glucose by liver first
Question:
Fermentation
Answer: 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
Question:
Pentose phosphate pathway
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Answer: 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
Occurs to some extent in all tissues, most common in tissues involved with
lipid synthesis (liver and adipocytes)
Regulated by NADPH (inhibits the first step)
Question:
Glycogenesis
Answer: Storage of glucose as glycogen
Muscles store glucose for their own use
Liver cells store glucose so they can later release it for use by other cells
Pathway almost exactly the reverse of glycolysis
Substrate for glycogenesis must have 3-C backbone
Question:
Glycogenolysis
Answer: Breakdown of glycogen
Question:
Glucogenesis
Answer: Synthesis of glucose from non-carb products such as proteins and
lactic acid
Liver cells
MCAT metabolism Questions with
Detailed Verified Answers
Question: Glycolysis
Answer: Breakdown of 6-carbon glucose molecule into two 3-carbon
molecules of pyruvate
Occurs in cytosol
Can occur with or without oxygen
10 steps
Question:
First half of glycolysis
Answer: 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
Question:
Second half of glycolysis
Answer: 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)
Question:
Net yield from glycolysis
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Answer: 2 ATP and 2 NADPH
Question:
Substrate-level phosphorylation
Answer: Production of ATP by the transfer of a phosphate molecule from a
molecule to an ADP
Question:
Fructose and galactose in glycolysis
Answer: Fructose and galactose are also able to feed into glycolysis
Usually converted to glucose by liver first
Question:
Fermentation
Answer: 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
Question:
Pentose phosphate pathway
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Answer: 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
Occurs to some extent in all tissues, most common in tissues involved with
lipid synthesis (liver and adipocytes)
Regulated by NADPH (inhibits the first step)
Question:
Glycogenesis
Answer: Storage of glucose as glycogen
Muscles store glucose for their own use
Liver cells store glucose so they can later release it for use by other cells
Pathway almost exactly the reverse of glycolysis
Substrate for glycogenesis must have 3-C backbone
Question:
Glycogenolysis
Answer: Breakdown of glycogen
Question:
Glucogenesis
Answer: Synthesis of glucose from non-carb products such as proteins and
lactic acid
Liver cells
