Nutrition in Humans

Question 1

What is ingestion?

Answer 1

Food is taken into the body.

Question 2

What is digestion?

Answer 2

Digestion is the process whereby large food molecules are broken down into smaller, soluble molecules that can be absorbed into the body cell.

Question 3

What is absorption?

Answer 3

Absorption is the process whereby digested food substances are absorbed into the body cells.

Question 4

What is assimilation?

Answer 4

Assimilation is the process whereby some of the absorbed food substances are converted into new protoplasm or used to provide energy.

Question 5

What is peristalsis and what happens to the antagonistic muscles during peristalsis?

Answer 5

Peristalsis is the rhythmic, wave-like muscular contractions in the wall of the alimentary canal.
Circular muscles contract and longitudinal muscles relax causing the wall to constrict.
Circular muscles relax and longitudinal muscles relax causing the wall to dilate.

Question 6

What are the digestives processes that take place in mouth?

Answer 6

1. Saliva contains an enzyme called salivary amylase which digests starch to maltose.
2. Chewing breaks food into smaller pieces→this increases the S.A to volume ratio for salivary amylase to work on.
3. The tongue rolls the food into bolus and passes down to the oesophagus.

Question 7

What are the digestives processes that take place in stomach?

Answer 7

1.The stomach is a distensible muscular bag, with thick and well-developed muscular walls.
2.Peristalsis in the stomach wall churns and breaks up the food and it also mixes the food well with the gastric juices.
3.Function of dilute hydrochloric acid in the stomach:
Stops the action of salivary amylase by denaturing it.
Changes pepsinogen(inactive) to pepsin(active)
Kills microorganisms in the food.
Provides an optimum pH(2) for the action of pepsin.
Pepsin digests protein into polypeptides.

Question 8

What are the digestive processes that take place in the small intestine?

Answer 8

1.The pancreas secretes pancreatic juice which contains pancreatic amylase, trypsin and lipases. The pancreatic juice passes through the pancreatic duct into the duodenum.
2.The gallbladder releases bile. Bile salts speed up the digestion of fats by emulsifying a big fat droplet into tiny fat droplets.
3.Epithelial cells in the small intestine produce maltase peptidase and lipase.
4.Pancreatic juice, bile and intestinal juice are all alkaline:
It helps neutralize acidic chyme from the stomach.
Provides an optimum pH for the enzymes to work.

Question 9

How is the small intestine adapted for absorption?

Answer 9

1.The surface area to volume ratio is increased in the following ways:
The inner surface of the small intestine is folded.
The folds have numerous minute finger-like projections called villi.
The epithelial cells of the villi have even more numerous microvilli.
2.The villi have one-cell thick walls and membranes→digested food take a shorter time to pass through the thin membrane.
3.The small intestine is long to provide sufficient time for absorption.

Question 10

How does absorption take place in the intestines?

Answer 10

1. Glucose and amino acids are absorbed by diffusion into the blood capillaries of the villi.
2. Glucose and amino acids are also absorbed by active transport.
3. `Glycerol and fatty acids diffuse into the epithelium. Here they combine to form minute fat globules which enter the lacteals.

Question 11

What are the functions of the liver?

Answer 11

1. It regulates the blood glucose concentration level in our blood by secreting insulin and glucagon.
2. It produces bile.
3. Storage of iron. Red blood cells are eventually destroyed in the spleen. Their leftover haemoglobin is brought to the liver. The liver breaks down the haemoglobin and stores the iron produced. During this process bile pigment is also produced.
4. Protein synthesis.
5. Deamination of amino acids. Deamination is the process by which amino groups are removed from amino acids and converted to urea.
6. Detoxification. The liver converts harmful substances into harmless ones.

Question 12

What are the effects of excessive consumption of alcohol?

Answer 12

1. Alcohol stimulates acid in the stomach. Excess stomach acid increases the risk of gastric ulcers. Prolonged alcohol abuse may lead to liver cirrhosis.
2. Liver cirrhosis is a disease where liver cells are destroyed and replaced with fibrous tissue.
3. Alcohol also slows down some brain functions.
4. Alcohol also reduces self-control.
5. Alcohol reduces reaction time.