Digestive System: Small Intestine

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Questions and Answers

What is the function of the sphincter muscle in the stomach?

to absorb nutrients from the food

to produce acidic digestive enzymes

to mix food with digestive enzymes

to release food into the small intestine in small amounts (correct)

Why do herbivores need a longer small intestine?

to allow for the digestion of cellulose (correct)

to digest fats more efficiently

to increase the surface area for absorption

to digest proteins more efficiently

What is the role of bile juice in the digestion process?

to break down carbohydrates into simple sugars

to make the food coming from the stomach acidic

to make the food coming from the stomach alkaline (correct)

to digest proteins into amino acids

What is the function of the pancreatic juice?

to contain enzymes like trypsin and lipase Signup and view all the answers

What is the purpose of the villi in the small intestine?

to increase the surface area for absorption Signup and view all the answers

What is the role of the intestinal juice in the digestion process?

to convert proteins into amino acids and carbohydrates into glucose Signup and view all the answers

What is the end product of carbohydrate digestion in the small intestine?

glucose Signup and view all the answers

What is the significance of the emulsifying action of bile salts?

it breaks down fats into smaller globules Signup and view all the answers

What is the primary function of cellular respiration?

To release energy for cellular activities Signup and view all the answers

Where does the breakdown of glucose into pyruvate take place?

Cytoplasm Signup and view all the answers

What is the byproduct of anaerobic respiration in yeast?

Ethanol and carbon dioxide Signup and view all the answers

Why does the build-up of lactic acid in muscles cause cramps?

Because it leads to muscle fatigue Signup and view all the answers

What is the energy currency of the cell?

ATP Signup and view all the answers

What is the difference between aerobic and anaerobic respiration?

Aerobic respiration uses oxygen, while anaerobic respiration does not Signup and view all the answers

What is the end result of the breakdown of pyruvate in the mitochondria?

Carbon dioxide and water Signup and view all the answers

What is the function of ATP in cellular respiration?

To provide energy for cellular activities Signup and view all the answers

Study Notes

Digestion in the Small Intestine

The small intestine is the longest part of the alimentary canal, fitted into a compact space due to extensive coiling.
The length of the small intestine varies among animals, depending on their diet, with herbivores having a longer small intestine to allow for cellulose digestion.
The small intestine is the site of complete digestion of carbohydrates, proteins, and fats.

Role of Liver and Pancreas

The liver secretes bile juice, which makes the acidic food from the stomach alkaline, allowing pancreatic enzymes to act.
Bile juice breaks down fats into smaller globules, increasing the efficiency of enzyme action.
The pancreas secretes pancreatic juice, containing enzymes like trypsin for protein digestion and lipase for fat breakdown.

Digestion and Absorption

The walls of the small intestine contain glands that secrete intestinal juice, which converts proteins to amino acids, complex carbohydrates to glucose, and fats to fatty acids and glycerol.
The inner lining of the small intestine has numerous finger-like projections called villi, which increase the surface area for absorption.
The villi are richly supplied with blood vessels, taking the absorbed food to every cell of the body for energy, tissue building, and repair.

Unabsorbed Food and Waste Removal

Unabsorbed food is sent to the large intestine, where its wall absorbs more water from the material.
The remaining material is removed from the body via the anus, with the exit of waste material regulated by the anal sphincter.

Nutrition in Organisms

Food material is used in cells to provide energy for various life processes.

Cellular Respiration

Glucose, a six-carbon molecule, is broken down into a three-carbon molecule called pyruvate in the cytoplasm.
Pyruvate may be converted into ethanol and carbon dioxide through anaerobic respiration (in the absence of oxygen), which occurs in yeast during fermentation.
Pyruvate may also be broken down using oxygen in the mitochondria, resulting in three molecules of carbon dioxide and water, through aerobic respiration.
Aerobic respiration releases a lot more energy than anaerobic respiration.

Breakdown of Pyruvate

In the absence of oxygen, pyruvate is converted into lactic acid, a three-carbon molecule, in muscle cells.
The build-up of lactic acid in muscles during sudden activity causes cramps.

Energy Generation

The energy released during cellular respiration is used to synthesise ATP (adenosine triphosphate).
ATP is broken down to release a fixed amount of energy that drives endothermic reactions in the cell.
ATP is used to fuel all other activities in the cell.