Biology - 2011

1. What are the seven food groups and their role in a healthy balanced diet.

2. What the recommended daily amounts of vitamins and minerals are in a healthy diet.

3. The role of the digestive system and its key organs during the physical and chemical breakdown of food.

4. The role of enzymes during the chemical breakdown of foods.

5. How enzymes function as catalysts. 6. The role of the villi tissue in the absorption of

nutrients from the gut into the blood. 7. The fate of these nutrients in the body and

their assimilation into cells and tissues. 8. The health consequences of overeating and

under eating. 9. The importance of getting the balance right.

Nutrition, Nutrients, Food, Groups, Fats, Carbohydrates, Proteins, Minerals, Vitamins, Fibre, Water, Digestive System, Physical, Chemical, Villi, Breakdown, Absorption, Nutrients, Amino acids, Glucose, Fatty acids, Glycerol, Obesity & Malnutrition.

The digestive system is a collection of cells, tissues and organs that function together to breakdown and absorb the daily essential nutrients: carbohydrates, proteins, lipids, minerals and vitamins required for healthy growth and development.

These large food molecules are broken down into smaller molecules by both physical and chemical

Our dietary intake of foods like proteins, carbohydrates and lipids should provide us with the correct amount of caloric energy to maintain our daily activities, growth (if we are children) and repair.

Food Digestive system

ENERGY for the cells

ENERGY for the cells

Respiration

Assimilation

The amount of energy (kJ) we consume through our diet and the recommended daily amount of minerals and vitamins we need for normal healthy growth and development is given by the table below. Notice that these values depend on our age, our sex, when female if we are pregnant or lactating and even our lifestyles.

The three main food groups are:- Proteins- Lipids- Carbohydrates

The other four food groups are:

Physical digestion

Chemical digestion

Mouth- Ingestion takes place- Food is chewed and mixed

with saliva- Saliva is formed by the

salivary glands- Saliva contains an enzyme

called AMYLASE which breaks down starch into maltose

Esophagus

After swallowing food is transported by peristaltic movements to the stomach

Stomach

- Gastric glands produce an enzyme called PEPSIN and hydrochloric acid which makes the perfect environment for the enzyme to work.

- PEPSIN breaks down proteins into peptides

Small intestine- Is divided into two parts- 1. Duodenum- 2. Ileum

Duodenum Most enzymes are found here:

The duodenum secretes ◦ MALTASE, SUCRASE and LACTASE◦ PEPTIDASE: breaks down peptides into amino acids

It receives juices from the liver and pancreas- Liver: releases bile which emulsifies fats- Pancreas: produces and releases pancreatic juice which contains - PANCREATIC AMYLASE: continues the breakdown of starch- TRYPSIN: continues the breakdown of proteins into peptides and

amino acids- LIPASE: breaks down lipids into fatty acids and glycerol

Ileum◦ Contains villi which absorb all the nutrients into

the blood

After the digestion of proteins, carbohydrates and lipids by the digestive system, glucose and amino acids are absorbed across the villi into the hepatic artery. Here they travel to the liver and are either used immediately, stored or assimilated into your cells.

Glucose is either respired or stored in muscle and liver as glycogen.

Amino acids are used to build proteins like enzymes. Excess amino acids are broken down by the liver to form urea.

Fatty acids and glycerol, which are absorbed into the lymph system are used to make cell membranes, some hormones or are stored under the skin.

Large intestine◦ Water is absorbed◦ The substances that have not been absorbed, as

fiber, are eliminated from the body as feces

A healthy balanced diet should provide you with the right amount of chemical energy, vitamins and minerals. It should also be relatively low in fats and protein (adult) and high in carbohydrates. Eating too much fatty or sugary foods, low in vitamins and minerals for long periods of time may lead to health problems later on in life. Diabetes, atherosclerosis, obesity and heart disease are all associated with eating a poor diet.