24 Questions
What is the primary usage of ethanol produced through anaerobic fermentation?
All of the above
Lactate produced in muscles during physical activity is converted back to glucose in the liver.
True
What enzyme is used by the body to metabolize ethanol?
alcohol dehydrogenase
Lactate is converted to _______________ in the liver.
glucose
What type of fermentation is used to produce ethanol?
Anaerobic fermentation
Glycolysis is more energy-efficient than anaerobic fermentation.
True
Match the following sugars with their breakdown products:
Lactose = Glucose and Galactose Fructose = Glucose Glucose = Glucose
What is the energy efficiency of anaerobic fermentation compared to glycolysis?
not so much
What happens when NADPH accumulates in the cell?
It inhibits the first enzyme in the PPP pathway
The non-oxidative phase of the PPP is necessary for generating NADPH.
False
What is the result of NADPH inhibiting the first enzyme in the PPP pathway?
This results in more glucose 6-phosphate being available for glycolysis. The cell is then able to use glycolysis to generate energy instead of going through the PPP pathway.
The ______ barked
dog
What is the function of the PPP pathway in an active muscle cell?
To make ribose for nucleotide synthesis
Glycolysis is a feeder pathway for the PPP.
True
Match the following terms with their descriptions:
Glycolysis = Breakdown of glucose to pyruvate PPP = Generation of NADPH and 5-carbon sugars Gluconeogenesis = Synthesis of glucose from pyruvate
What is the purpose of the oxidative phase of the PPP in an active muscle cell?
The oxidative phase of the PPP generates NADPH, which is needed in tissues that are generating NADPH, because the oxidative phase would generate more 5C sugars than the cell needs.
What is the net balance of glycolysis?
Glucose + 2 NAD+ + 2 ADP + 2 Pi → 2 Pyruvate + 2 NADH + 2 H+ + 2 ATP + 2 H2O
In aerobic conditions, NADH is reoxidized to NAD+ by transfer of electrons to the respiratory chain in the mitochondrion.
True
What is the purpose of lactate dehydrogenase in lactate fermentation?
Lactate dehydrogenase uses up NADH to reduce the carbonyl of pyruvate to lactate.
In yeast, pyruvate is fermented to _________________.
ethanol
Match the following compounds with their respective products in fermentation:
Glucose = Pyruvate Pyruvate = Lactate Lactate = Ethanol Ethanol = Glucose
What is the fate of pyruvate in human fermentation?
It is converted to lactate
Under aerobic conditions, glycolysis cannot continue because NADH cannot be reoxidized to NAD+.
False
What is the purpose of regenerating NAD+ from NADH in glycolysis?
To allow glycolysis to continue.
Study Notes
Energy Metabolism
- During short bursts of physical activity, lactate is produced in muscles and transported to the liver, where it's converted back to glucose.
Cori Cycle
- In the liver, an enzyme converts lactate into pyruvate, then into glucose.
- This process is not as efficient as glucose production.
Fermentation
- Fermentation is used to make alcoholic beverages, industrial ethanol, and CO2 for bread to rise.
- In the body, alcohol dehydrogenase is used to metabolize ethanol into acetaldehyde, which is further metabolized.
Anaerobic Fermentation
- Not as energy-efficient as aerobic respiration.
Glycolysis
- Glucose + 2 ATP + 2 NAD+ + 4 ADP + 2 Pi → 2 Pyruvate + 2 ADP + 2 NADH + 2 H+ + 4 ATP + 2 H2O (net balance)
- To continue glycolysis, organisms must reoxidize NADH back to NAD+.
Fate of Pyruvate
- Pyruvate can be fermented into lactate or ethanol, regenerating NAD+ from NADH.
- Human cells ferment pyruvate into lactate, while yeast ferments it into ethanol.
Lactate Fermentation and Cori Cycle
- Under hypoxic or anaerobic conditions, NADH generated by glycolysis cannot be reoxidized by O2.
- Lactate dehydrogenase reduces pyruvate to lactate, using up NADH.
Non-oxidative Phase of PPP Reactions
- PPP reactions are needed in tissues generating NADPH.
- Non-oxidative phase shuffles 5C sugars to 2 6C sugars and glyceraldehyde 3-p.
Metabolic Control of PPP by NADPH
- NADPH regulates the partitioning of glucose 6-phosphate between glycolysis and the PPP.
- When NADPH accumulates, it inhibits glucose-6-phosphate dehydrogenase, diverting glucose 6-phosphate to glycolysis.
Pathway Integration in an Active Muscle Cell
- During exercise, glucose is metabolized through glycolysis, with pyruvate converted to lactate or used for energy production.
- The Cori cycle is an important pathway for lactate produced in muscles, which is then converted back to glucose in the liver.
Understand how lactate is produced and converted during short bursts of physical activity in the Cori cycle. Learn about muscle metabolism and saccharide transportation.
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