Carbohydrate Digestion Process

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Questions and Answers

Where does carbohydrate digestion primarily begin?

In the small intestine

In the esophagus

In the mouth (correct)

In the stomach

What is the main function of salivary a-amylase in carbohydrate digestion?

To catalyze the hydrolysis of a-glycosidic linkages (correct)

To convert disaccharides into monosaccharides

To inactivate polysaccharides

To absorb monosaccharides into the bloodstream

What is the primary site for carbohydrate digestion?

Mouth

Stomach

Small intestine (correct)

Large intestine

Which enzyme is responsible for breaking down maltose into glucose?

Maltase Signup and view all the answers

Which monosaccharide is produced from the hydrolysis of lactose?

Glucose and galactose Signup and view all the answers

How are monosaccharides absorbed into the bloodstream from the intestinal wall?

Active transport via protein carriers Signup and view all the answers

What happens to galactose and fructose after being absorbed in the bloodstream?

They are converted to glucose metabolism products in the liver Signup and view all the answers

In what cellular location does glycolysis occur?

Cytosol Signup and view all the answers

What is the main purpose of glycolysis?

To convert glucose into pyruvate and generate energy Signup and view all the answers

In the first stage of glycolysis, how many ATP molecules are consumed?

Two ATP molecules Signup and view all the answers

Which enzyme catalyzes the conversion of glucose 6-phosphate to fructose 6-phosphate?

Phospho-gluco-isomerase Signup and view all the answers

What molecule is generated as a product during the formation of 1,3-bisphosphoglycerate?

NADH Signup and view all the answers

Which enzyme is involved in the formation of 2-phosphoglycerate from 3-phosphoglycerate?

Phospho-glycero-mutase Signup and view all the answers

What are the resulting molecules after the cleavage of fructose 1,6-bisphosphate?

One glyceraldehyde 3-phosphate and one dihydroxyacetone phosphate Signup and view all the answers

During glycolysis, which reaction is an ATP-producing step?

Formation of 3-phosphoglycerate Signup and view all the answers

Which product is a result of the ATP hydrolysis during the phosphorylation steps of glycolysis?

ADP Signup and view all the answers

Study Notes

Carbohydrate Digestion Process

Digestion involves hydrolysis, breaking down food molecules into simpler chemical units for metabolic use.
Carbohydrate digestion starts in the mouth, although it's minimal due to quick swallowing.
Hydrolysis splits chemical bonds and incorporates water into resulting fragments.
Salivary α-amylase, an enzyme in saliva, initiates the breakdown of starches into smaller polysaccharides and maltose.
Stomach digestion of carbohydrates is limited; salivary α-amylase becomes inactive under acidic conditions, and no other enzymes are present.

Small Intestine and Enzymatic Breakdown

The small intestine is the primary site for carbohydrate digestion.
Pancreatic α-amylase continues the breakdown of polysaccharides into disaccharides like maltose.
Disaccharidases, a group of glycoside hydrolases, convert disaccharides into monosaccharides:
- Maltase: maltose to glucose.
- Sucrase: sucrose to glucose and fructose.
- Lactase: lactose to glucose and galactose.
The resulting monosaccharides (glucose, galactose, and fructose) are absorbed into the bloodstream through intestinal villi, rich in blood capillaries.
Monosaccharide transport across cell membranes is facilitated by protein carriers.
Galactose and fructose are converted to glucose metabolic products in the liver.

Glycolysis Overview

Glycolysis, occurring in the cytosol, is the metabolic pathway converting glucose into two pyruvate molecules, producing energy (ATP and NADH).
It involves two stages: the six-carbon stage and the three-carbon stage.

Six-Carbon Stage of Glycolysis

Initial steps (1-3) involve converting ATP to ADP to transform monosaccharides into their phosphorylated forms.
Step 1: Glucose 6-phosphate is formed via phosphorylation by hexokinase; energy from ATP hydrolysis is required.
Step 2: Glucose 6-phosphate is isomerized to fructose 6-phosphate by phospho-gluco-isomerase.
Step 3: Fructose 1,6-bisphosphate is formed through another phosphorylation reaction, facilitated by phospho-fructo-kinase.

Three-Carbon Stage of Glycolysis

Steps (4-10) focus on the conversion of C6 biphosphate into two C3 monophosphate species.
Step 4: Aldolase catalyzes the splitting of C6 biphosphate into dihydroxyacetone phosphate and glyceraldehyde 3-phosphate.
Step 5: Dihydroxyacetone phosphate is isomerized to glyceraldehyde 3-phosphate by triose-phosphate isomerase.
Step 6: Formation of 1,3-bisphosphoglycerate involves glyceraldehyde 3-phosphate dehydrogenase; NADH is produced and inorganic phosphate is used.
Step 7: ATP production occurs as 1,3-diphosphoglycerate donates a phosphate to ADP, catalyzed by phospho-glycero-kinase.
Step 8: 3-phosphoglycerate is isomerized to 2-phosphoglycerate, moving the phosphate group from carbon 3 to carbon 2, mediated by phospho-glycero-mutase.
Step 9: Formation of phosphoenolpyruvate involves dehydration reactions leading to energy release for later ATP generation.

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Description

This quiz covers the process of carbohydrate digestion, which begins in the mouth and involves hydrolysis to break down food molecules. It also highlights the role of salivary a-amylase in the initial stages of digestion. Test your knowledge on the steps and enzymes involved in carbohydrate breakdown.