Heterotrophic nutrition in humans

Question 1

Ingestion:

Answer 1

the process by which food is taken into the body via the mouth.

Question 2

Digestion:

Answer 2

the process by which food is broken down into simple, soluble food molecules

Question 3

Absorption:

Answer 3

the process by which the soluble food molecules, produced in digestion, move into the body fluids and body cells

Question 4

Assimilation:

Answer 4

the process by which the body uses the soluble food molecules absorbed after digestion.

Question 5

Egestion or defaecation:

Answer 5

the process by which undigested food material is removed from the body.

Question 6

A balanced diet

Answer 6

The food an animal eats is called its diet. Humans must consume a balanced diet each day. This must contain carbohydrates, proteins, lipids, vitamins, minerals, water and roughage in the correct proportions to supply the body with enough energy for daily activities and the correct materials for growth and development, and to keep the body in a healthy state.

Question 7

Carbohydrates

Answer 7

Sweet foods, e.g. fruits, cakes, jams. Starchy foods, e.g. yams, potatoes, rice, pasta, bread.

• To provide energy (17 kJ g−1): energy is easily released when respired.
• For storage: glycogen granules are stored in many cells.

Question 8

Proteins

Answer 8

Fish, lean meat,
milk, cheese, eggs,
peas, beans, nuts.

• To make new cells for growth and to repair damaged tissues.
• To make enzymes which catalyse reactions in the body.
• To make hormones whichcontrol various processes in the body.
• To make antibodies to fight disease.
• To provide energy (17 kJ g−1): used only when stored carbohydrates and lipids have been used up

Question 9

Lipids

butter, vegetable oils, fatty meats, margarine

Answer 9

• To make cell membranes of newly formed cells
• For storage: fat is stored under the skin and around organs
• for insulation: fat under the skin acts as an insulator