Food and Diet Why do we need food: Energy Growth Keep body functioning properly and healthy All need food Autotrophs ( green plants) make own food Heterotrophs (animals)– take in ready made food

Energy in Food Released during cellular respiration Glucose and oxygen broken down in mitochondria into carbon dioxide and water and chemical energy released in form of ATP to be used for work in the cell

Food types Carbohydrates Proteins Fats Vitamins and minerals (Water needed)

Carbohydrates Sugars (glucose and fructose) found in fruits and some vegetables, cane sugar (sucrose) in jams, cakes. Starch is found in potatoes, rice, pasta, mielies and other grains (cereals). Cheapest, ready form of energy. Elements = C, H, O. Starch is a big molecule formed when many glucose molecules join together

Carbohydrates cont. Excess converted to Glycogen ( formed when glucose molecules join together) is stored in liver and muscles Fat stored in fat depots under skin (adipose tissue) or around kidneys and in abdomen. Cellulose (plant cell walls). Important as dietary fibre, acts as roughage to maintain healthy digestive system; it keeps food moving in gut.

Proteins Found in meat, fish, eggs, milk, cheese. Beans, wheat and maize. Needed to build cells and tissues, needed for growth. Elements = C, H, O and Nitrogen ( and sometimes Sulphur). Long chains of amino acids join together to form proteins. Different chains of amino acids form different proteins.

Proteins cont. Amino acids cannot be stored. Those not used to form new cells have the Nitrogen removed and the remaining part is converted to glycogen to be stored or used to release energy.

Fats Animal in meat, milk, cheese, butter, egg yolk. Plant fats as oils – olive, sunflower. Lipids = fats, oils. Fat = solid at room temperature Oils = liquid at room temperature Provides most energy. Forms cell membranes. Elements = C, H, O. Stored as adipose tissues under skin.

Vitamins Help the body to use proteins, carbohydrates and fats Found in food we eat, especially fruit and vegetables. A,D,E,K – soluble in fats B,C- water soluble – can’t be stored Needed in small quantities See table in notes – do not need to learn detail – data response questions.

Minerals Needed in small quantities Present in food we eat Needed to help nerves and muscles work. See table in notes – do not need to learn detail – data response questions.

Water Body = 70% water Vital for life. ½ comes from food. Drink 6-8 glasses of water a day

Dietary Fibre Plant cell walls Fruit, vegetables, cereals Becomes bulky when absorbs water. Helps you feel full. Helps food move along gut and push waste out. Prevents diseases like cancer of colon.