Carbohydrate Digestion and Glycolysis Flashcards
Does any carbohydrate digestion occur in the mouth? Why / why not?
Small amount of carb digestion occurs in mouth due to presence of the alpha-amylase enzyme in saliva.
Alpha-amylase cuts some glycosidic bonds of carbs, producing shorter polysaccharides (and maltose).
End result is partial digestion of starch in the mouth.
What role does the stomach play in digestion?
No digestion of carbohydrates occurs in the stomach due to the lack of carbohydrate digestive enzymes.
What enzyme(s) help facilitate carb digestion in the small intestine? What do these enzymes do to assist carb digestion?
The small intestine contains many enzymes that cleave the glycosidic bonds within different poly/disaccharides.
Each carb requires a specific enzyme in order to break bonds to form simple sugars.
For example, lactase is required to breakdown lactose.
Why is it necessary to break carbs down into monosaccharides in the small intestine?
Only carbs in monosaccharide form can be absorbed by the lining of the small intestine (via active transport), which allows monosaccharides to enter the blood.
Carbs in the di/polysaccharide form cannot be absorbed.
How are the carbohydrate digestion products transported into the bloodstream? Where are the monosaccharides taken once in the bloodstream?
Carbohydrates in monosaccharide form are absorbed into the blood through the small intestine, via active transport.
Once in the blood, monosaccharides are taken to the liver to be metabolised, Other cell types can use the glucose produced in digestion, but not fructose and galactose).
Why does glycolysis occur in the cytosol where all of the enzymes needed for
the glycolysis reactions are located?
Each of the steps of glycolysis requires a specific enzyme to facilitate the
chemical reaction.
The enzymes needed for glycolysis are located in the
cytosol, so that is where the glycolysis reaction occurs.
A metabolic reaction always occurs where the enzymes needed for the reaction are located.
What is the starting input (reactant) for glycolysis and what is the final output (end
products)?
Glucose is the input required for glycolysis to begin.
Two pyruvate compounds are produced in the last step of
glycolysis (step 10).
Two ATP and 1 NADH are also produced in glycolysis.
Where does the input required for glycolysis come from?
The glucose used in glycolysis is gained from the digestion of complex
carbohydrates.
Once glucose entered the blood after digestion, the release of insulin promotes the movement of glucose into the cell.
Once inside the cell,
glucose can be used in glycolysis.
What is the final output of glycolysis used for under anaerobic and aerobic conditions?
For what purpose?
Pyruvate is the final output of glycolysis.
Aerobic Conditions:
Pyruvate is converted to acetyl CoA (producing 1 NADH). Acetyl CoA is central metabolite in the citric acid cycle.
Citric acid cycle connects to the electron transport chain where large amounts of ATP is produced.
Anaerobic Conditions:
Pyruvate is converted to lactate. NADH is also converted to NAD+.
NAD+ can then be used in glycolysis to produce another 2 ATP in the absence of oxygen.
Why is it necessary for us to perform the glycolysis reaction?
Glycolysis is necessary to produce pyruvate, which is converted to acetyl CoA, in order to continue the bioenergetic pathway, producing ample ATP.
Glycolysis itself also produces small amounts of ATP (2 units per reaction) which can be used to power cellular processes.
