Nutrition

Modes of nutritionHeterotrophic 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.

BiomoleculesOrganic 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

fructosegalactoseribose

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

CarbohydratesCarbohydratesReducing 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 testBenedict's reagent contains blue copper(II) ions

(Cu2+) which are reduced to copper(I) (Cu+). These are precipitated as red copper(I) oxide which is insoluble in water.

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.

CarbohydratesCarbohydratesNon-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.

CarbohydratesCarbohydratesFunction: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.

LipidsDiverse 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

organismsserve also as insulation against low temperatures

(blubber in seals and whales)forms the cell membranesform special molecules such as pigments

(chlorophyll), hormones and vitamins.

LipidsLike 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

LipidsSaturated lipids

their fatty acids contain NO double bondscommon in food rich in animal fatsolid at room temperature

Unsaturated lipidstheir fatty acids contain double bondsmore common in plant oils

ProteinsThese 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

ProteinsBiological 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)

Carbohydrates

Lipids Proteins

Elements they contain

C,H,O C,H,O(lower proportion of oxygen than carbohydrates)

C,H,O,N, (S, P)

Building blocks/sub units

Monosaccharides

FatsFatty acids + glycerol

Amino acids

Function Principal/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