Nutrition

Modes of nutrition Heterotrophic nutrition The nutrition obtained by digesting organic compounds. e.g. of heterotrophs include animals and fungi. Autotrophic nutrition The nutrition in which organisms make their own food from inorganic molecules. e.g. of autotrophs include plants and algae.

Biomolecules Organic molecules are the chemicals of life, compounds composed of more than one type of element, that are found in, and produced by, living organisms. What is the difference between an organic and an inorganic molecule? Organic molecules contain carbon-hydrogen bonds, whereas inorganic molecules do not. The four major classes of biomolecules include: carbohydrates, proteins, lipids and nucleic acids.

Carbohydrates contain the elements Carbon, Hydrogen and Oxygen. There are three common classes of carbohydrates: monosaccharides disaccharides polysaccharides Simple sugars e.g. glucose, fructose, galactose, ribose - short chains of two monosaccharide units or residues e.g. sucrose, lactose Contain many monosaccharide residues e.g. starch, glycogen, cellulose, chitin

Monosaccharides e.g.glucose fructose galactose ribose disaccharides e.g.sucrose: glucose + fructose {typical disaccharide: cane sugar} lactose: glucose + galactose { milk sigar} maltose: 2 glucose Polysaccharides e.g.Starch storage forms of monosaccharides: used as fuels Glycogen Cellulose structural elements in plant cell walls and animal Chitin exoskeletons

Carbohydrates Reducing sugars (property is on basis of reaction with Fehlings or Benedict’s reagents) All monosaccharides and the disaccharides, lactose and maltose are reducing sugars

Benedict’s test Benedict's reagent contains blue copper(II) ions (Cu 2+ ) which are reduced to copper(I) (Cu + ). These are precipitated as red copper(I) oxide which is insoluble in water. precipitatedcopper(I) oxide To test for the presence of reducing sugars in food, the food sample is dissolved in water, and a small amount of Benedict's reagent is added. During a water bath, which is usually 4-10 minutes, the solution should progress in the colours of blue (with no glucose present) green yellow orange and then brick red or brown.water bath

Carbohydrates Non-reducing sugars (property is on basis of reaction with Fehlings or Benedict’s reagents) Disaccharide: sucrose They do not react with any of the reducing-sugar test solutions. They can, however, be hydrolysed using dilute hydrochloric acid. After hydrolysis and neutralization of the acid, (e.g. with sodium bicarbonate) the product may be a reducing sugar that gives normal reactions with the test solutions.hydrolysed hydrochloric acid

Carbohydrates Function: They form a major part of your food and help a great deal in building your body strength, by generating energy during the process of respiration. Carbohydrates also form the cell walls of plants (cellulose) and are found in the exoskeleton of insects (chitin). Carbohydrates are found in rice and other cereals, breads, pastas, candy, sodas, wines, ground provisions (dasheen, yam, potato) and fruits.

Lipids Diverse group of organic compounds which include fats, oils, waxes, sterols and fat-soluble vitamins, among others. Play a variety of roles. principal form of stored energy in most organisms serve also as insulation against low temperatures (blubber in seals and whales) forms the cell membranes form special molecules such as pigments (chlorophyll), hormones and vitamins.

Lipids Like carbohydrates, fats contain the elements Carbon, Hydrogen and Oxygen. The chemical ‘building blocks’ of storage lipids: - fatty acids - glycerol. Lipids may be found in such foods as seeds and nuts, oils, butter, margerine, mayonaise, cheese, meats, eggs. This is an example of a triglyceride

Lipids Saturated lipids their fatty acids contain NO double bonds common in food rich in animal fat solid at room temperature Unsaturated lipids their fatty acids contain double bonds more common in plant oils

Proteins These are the most abundant biological macromolecules occurring in all cells and all parts of the cell. Polymers of amino acids (polypeptides): constructed from the same set of 20 common amino acids Occur in great variety (1000’s of different kinds) Exhibit enormous diversity of biological function Biological function depends on its amino acid sequence

Proteins Biological function: (includes among others) a. Structural proteins: collagen and keratin in skin and nails. b. Proteins with specific functions: e.g. i. enzymes (biological catalysts) ii. antibodies (immune system) iii. haemoglobin (in red blood cells)

CarbohydratesLipidsProteins Elements they contain C,H,O (lower proportion of oxygen than carbohydrates) C,H,O,N, (S, P) Building blocks/sub units Monosaccharides Fats Fatty acids + glycerol Amino acids FunctionPrincipal/chief source of energy for metabolism, structural components of plants, arthropods etc. Energy storage molecule, maintaining healthy skin and hair, insulating body organs against shock, maintaining body temperature, and promoting healthy cell function growth and development Some sources Cereals, breads, sugary foods, nuts, ground provisions, Vegetable oils, fish oils, nuts, legumes, lard, butter, margarine, etc. Milk & milk products, meats, fish, beans, nuts legumes, eggs, soya