1. Food and Nutrition in Humans Classes of Food Substances Food Storage

2. Syllabus Objectives Students must be able to  perform tests to identify classes of food substances  Discuss the role of food storage in living organisms  Identify the products stored and the sites of storage

3. Classes of Food Substances All organisms require organic substances for their living processes Green plants make organic compounds from raw materials that are inorganic Animals are supplied with organic compounds in the form of food

4. Classes of Food Substances - Nutrition Nutrition is the process of obtaining or making food Living organisms require food for  Growth  To provide energy  To maintain health

5. Classes of Food Substances Carbohydrates Fats and Oils Proteins Minerals Vitamins

6. Classes of Food Substances - Carbohydrates Provide energy There are 3 types of carbohydrates  Monosaccharides (simple sugars) e.g. glucose, frustose  Disaccharides (complex sugars) e.g. maltose, sucrose  Polysaccharides e.g. starch, cellulose, glycogen

7. Classes of Food Substances - Fats and Oils Provide energy Usually stored as food reserves Animals store fats Plants store oils

8. Classes of Food Substances - Proteins Required for growth Required for repair of damaged or worn out tissues

9. Classes of Food Substances - Vitamins and Minerals Essential for the maintenance of good health Control metabolism Prevent diseases

10. The role of food storage in plants and animals Plants and animals use food for  providing energy  Growth and tissue repair  Controlling metabolism  Preventing disease Food which is taken in in excess of an organism’s needs is stored in some form after poisonous or useless materials are disposed of The stored material can be utilized in many ways

11. The role of food storage in plants and animals cont’d Food is stored for the following reasons:  Survival when food is scarce or unavailable Can you give examples of this?  Organisms can survive unfavourable periods of time without making or taking in food  For use during rapid growth when conditions become favourable  Storage takes place in seeds, fruits and in animals in eggs. These perform reproductive functions ensuring dispersal and development of a growing embyro.  Stored products in plants and animals make useful food for man and other organisms. E.g. cassava, yam, potato, onion

12. Storage products and sites of storage Storage in Plants  Storage in plants occur in vegetative organs ( roots, stems and leaves ) and reproductive structures ( fruits and seeds )  Temporary storage of starch occur during the day in leaf cells as the products of photosynthesis accumulate

13. Storage in Roots Food produced by the leaves in the growing season passes downward and is stored in roots They can be distinguished from stem tubers because they lack buds and scale leaves There are 2 types of vegetative root storage  Root tubers e.g. sweet potato, cassava  Tap root e.g. carrot, radish turnip, beetroot

14. Root tubers Sweet potato (Ipomoea batatas) and cassava (Manihot esculenta) both store starch and very small amounts of protein Sweet potato also stores maltose sugar

15. Tap root A swollen tap root is the main root in carrot, radish turnip and beetroot Carrots store glucose in the phloem

16. Storage in Stems A variety of stem storage organs is found in nature  Stem tuber  Rhizome  Corm

17. Stem tuber Swollen underground stem Possesses scale leaves or leaf scars (which distinguish them from root tubers) The scale leaves have buds in the axils (called eyes) These buds can grow into shoots utilizing the stored food in the tuber Examples include:  Yam (Dioscorea)  Irish potato (Solanum) - mainly stores starch

18. Rhizome Swollen, horizontal growing underground stem Has nodes at which scale leaves and axillary buds are present A terminal bud is present at one end Adventitious and contractile roots grow from the rhizome Examples include:  Canna lily  Ginger (Zingiber), Stores starch and oils (gives characteristic smell)

19. Corm Short, swollen underground stem Grows vertically Covered by scale leaves which grow from nodes Buds are present in the axils of the leaf bases Adventitious and contractile roots arise from the base of the corm A terminal bud is found at the top Examples include:  Dasheen (Colocasia), cocoyam which both store starch

20. Other Storage Stems Sugar cane has a swollen stem growing above ground It stores sucrose sugar It is cultivated in many tropical countries It is of great economic importance

21. Storage in leaves All plants store food temporarily in their leaves Most store starch Onions chives (escallion) store sugar Some plants develop underground storage organs of swollen leaves which are called bulbs Storage leaves grow from a flattened stem and are enclosed by dry, scaly outer leaves. The stem bears adventitious roots Tiny lateral buds are found in the axils of some of the storage leaves

22. Storage in Fruits and Seeds SEEDS  Provide food for young developing embryos for early growth  Young plants are unable to make their own food until they form green leaves and are able to photosynthesize FRUITS  Food reserves in fruits are important for attracting animals which disperse their seeds. Fruits and seeds contain varying amounts of carbohydrates, fats, proteins, vitamins, minerals and water.

23. Storage in Fruits Storage can occur in the fruit wall (pericarp) or receptacle of fruits Mango (Mangifera indica) and the West Indian cherry store sugar in the mesocarp Sugar is stored in the hairs of the endocarp in the orange (Citrus sinensis)

24. Storage in Seeds Most seeds store food in the cotyledons Some seeds store food in the endosperm  Endospermic seeds develop another storage tissue in addition to the cotyledons  This is more common in monocotyledons whose seeds have only cotyledon E.g. corn and other cereals and coconut  It is found in some dicotyledons (seeds with two cotyledons) E.g. castor oil

25. Can you identify the different types of storage organs (a) to (f) represent?

26. Storage in Animals Storage in animals occurs mainly in the liver and muscles  In fat deposits  In eggs

27. The Liver When excess carbohydrates are eaten, the surplus is converted to glycogen by the liver and stored in liver and muscle cells Liver cells also store Fat Vitamin A, B 12 and D Iron from the breakdown of red blood cells

28. Fat deposits… Excess carbohydrates not converted to glycogen is converted to FAT for long term storage in animals Animals can make fat from any excess sugar, fat or protein in the diet Fat stored in special fat deposits under the skin of animals like pig and humans around organs such as the kidney, heart, ovaries and the gut.

29. Fat deposits cont’d Large animals like the polar bear, seals and whales have thick fat layers under the skin which provide insulation against heat loss. In whales and seals this fat layer is called blubber The hump of a camel, an animal of the hot desert, is a fat store which when metabolized yields large amounts of energy and water.

30. Eggs Eggs store  Protein  Fat The fat being concentrated mainly in the yolk.  Some eggs also store simple sugars

31. Summary Questions People trying to lose weight eat egg whites only…why? What other specific foods would you recommend for someone trying to lose weight? Give reasons for your answer.

32. Site references http://homepage.smc.edu/hodson_kent/plant _growth/Angiosperms/ID/basics.htm http://homepage.smc.edu/hodson_kent/plant _growth/Angiosperms/ID/basics.htm http://www.cccmkc.edu.hk/~kei- kph/Food%20storage%20organ/Food%20sto rage%20organ.htm http://www.cccmkc.edu.hk/~kei- kph/Food%20storage%20organ/Food%20sto rage%20organ.htm