Biology – Nutrition Essay Sample

Biology – Nutrition Pages
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Type of Nutrition
* Nutrition – process by which organisms obtain energy and nutrients from food, for growth, maintenance and repair of damaged tissues. * Nutrients – the important substances which are required for nourishment of an organisms. * Living organisms are divided into two groups (based on the nutritional habits): autotrophs and heterotrophs.

(i) Autotroph
* Autotrophs – organisms that are able to synthesise complex organic compounds from raw, simple inorganic substances (water and air) by using light or chemical energy. These organisms manufacture their own food by photosynthesis or chemosynthesis. * Photoautotrophs – chlorophyll containing organisms that utilise solar energy for building organic substance. * Photoautotropic nutrition = holophytic nutrition.

* Chemoautotrophs – organisms synthesise organic substances by utilising chemical energy. Autotrophs Example
Photoautotroph Trees
Chemoautotroph Bacteria

(ii) Heterotroph
* Heterotrophs – organisms that are not able to synthesise their own nutrients but they obtain the nutrients from other organisms. * Holozoic nutrition – organisms feed by ingesting solid organic matter that digested and absorbed into the bodies. * Saprophytism – organisms feed on dead and decaying organic matter. * Parasitism – organisms obtains nutrients (absorbs readily digested food) by living on / in the body of another living organisms (the host) Heterotrophs Example

Saprophyte Fungi
Holozoic nutrition Carnivores
Carnivorous plants (Holozoic nutrition) Venus traps and pitcher plants
Parasites Lice and fleas

Human Teeth
Balanced Diet
* Diet – the food and drink that we consume.
* Balanced diet – diet contains the correct proportions of all the different classes of foods for the requirement of body. * Metabolisms – the sum of all biochemical reactions that occur in the cells of living organisms. * Metabolic rate – a measure of the energy demands of the living body over a specified period of time. Unit – kilojoule (kJ) * Energy value / calorific value of food – the quantity of heat produced when one gram of food is completely oxidised. Unit – Joules per gram (J g-1) or calories. * Energy value = (Mass of water x Increase in temperature x 4.2 ) / Mass of food * Energy value = (g)(˚C)(J g-1˚C-1) / (g) = J g-1

Seven Important Classes of Food
1. Carbohydrates (provide energy)
2. Proteins (Build new tissues / important in growth and repairing damaged tissues) 3. Fats (provide energy / storage of extra foods)
4. Water (act as medium for biochemical reaction / transportation of substances) 5. Vitamins (prevent diseases / efficient metabolism / important for normal growth) 6. Minerals (important for normal growth and development of teeth, bones and muscles) 7. Roughage / Dietary fiber (prevent constipation / stimulate peristalsis)

Nutrition Tag
Factors Affecting Daily Energy Requirement
Balance diet is essential for healthy growth and development of the body. 1. Age – children and teenagers need more energy due to their high metabolic rate. 2. Sex – male adult needs more energy due to in males have high metabolic rate. 3. Pregnancy and lactation – pregnant women need more energy due to support the growing foetuses and produce milk for their babies. 4. Occupation – an active person requires high energy due to the person does a lot of heavy work. 5. Size or body weight – a person smaller in size has a larger surface area per unit volume. Thus, the rate of heat loss is high. 6. Climate – people living in cold countries need more energy to maintain body temperature. 7. Genetics – genetics disposition in certain person may decide different metabolic rate. 8. Health – In sufficient secretion of thyroxine hormone may cause lower in metabolic rate. 9. Lifestyle – An active person requires higher energy than a passive person

Energy Content of Food
* Bomb calorimeter – used to calculate the energy value of various types of food samples. * One calorie (cal) = 4.2 joules (J)
* Energy value of food (kJ g-1) = (4.2 x mass of water x increase in temperature) (mass of food sample x 1000) * specific heat capacity of water, C = 4.2 J g-1 ˚C-1; mass of water in g; temperature in ˚C and mass of food sample in g.

Classes of Food Nutrients
Classes of Food Nutrients
Test Reagent Observation Conclusion
Benedict’s test Food sample + Benedict’s solution (Place in boiling water bath) The solution turns from blue to green / yellow / brick-red precipitate formed (depend on sugar concentration). Food sample contains reducing sugar Benedict’s test Food sample + Benedict’s solution + Dilute hydrochloric acid (Place in boiling water bath) + neutralise by sodium hydrogen carbonate powder The solution turns from blue to green / yellow / brick-red precipitate formed (depend on sugar concentration). Food sample contains non-reducing sugar Iodine / Starch test Food sample + Iodine solution The solution turns frombrownish-yellow to blue-black. Food sample contains starch Emulsion test Food sample + ethanol

The fat droplets formed on the surface and the solution become cloudy. Food sample contains oil (lipid) Sudan III test Food sample + Sudan III stain A red-stained oil layer separates out and float on the water surface Food sample contains oil (lipid) Fat test Food sample + filter paper A translucent mark formed Food sample contains oil (lipid) Millon’s test Food sample + Millon’s reagent + 1% sodium nitrite (Place in boiling water bath) The solution turns brick-redprecipitate. Food sample contains protein Biuret test Food sample + 20% sodium hydroxide solution and 1% copper(II) sulphate solution The solution turns from blueto purple colour. Food sample contains protein

Vitamin Cod oil
* It is a group of complex organic compounds that are needed in small quantities by living organisms because vitamins can be reused in body metabolisms. * Vitamins do not provide energy to body metabolism and vitamins are non-protein organic compounds. * Living organisms cannot synthesise vitamins.

* Vitamins can be only obtained from diet.
* It is essential to maintenance of good health, normal growth and efficient metabolism. * There are two categories in vitamins: fat-soluble vitamins and water-soluble vitamins.

Fat-soluble Vitamins
Types of Vitamins Sources Functions Effect of deficiency A (retinol) Milk, carrots, tomatoes, eggs, fish oil, green vegetables, butter – Builds visual pigments on retina for night vision- Immunity- Growth of epithelial cells- Antioxidant- Build body resistance to diseases – Night blindness- Xerophthalmia (cornea becomes dry)- Scaly skin D (calciferol) Formed (skin) during the presence of sunlight, fish liver oil, egg yolk, cheese – Enhances absorption of calcium and phosphorus- Build strong bones and healthy teeth – Rickets (weak bones)- Osteomalacia (softening of bones) E (tocopherol) Palm oil, cereals, nuts, green vegetables, olive oil, milk- – Preserves healthy muscular system, blood circulatory (red blood cells) and nervous system- Antioxidant- Maintain healthy function of the reproduction system – Premature aging- Low fertility- Slow wound healing K (phylloquinone) Green vegetable, totatoes – Helps in blood clotting – Detective blood clotting- Anaemia

Cod fish oil
Water-soluble Vitamins
Types of Vitamins Sources Functions Effect of deficiency B1 (thiamine) Milk, legumens, wheatgerm, yeast extract, nuts, whole grains – Precursor of a coenzyme – Coenzyme for carbohydrates metabolisme – Beri-beri (muscle weakness, nerve disorder)- Fatigue B2 (riboflavin) Milk, wheatgerm, liver, eggs – Component of coenzyme – Healthy nervous system – Sore eyes- Skin lesions at the corner of mouth, nose and ears- Inflammation of tongue and lips B3 (niacin) Liver, rice, legumes, fish, yeast extract – Component of coenzyme- Healthy nervous system, skin and intestines – Pellagra (skin and gastrointestinal lesions) B5 (pantothenic acid) Fish, egg yolk, liver, meat – Component of coenzyme for carbohydrates, protein and fatty acids metabolism – Muscle cramps- Fatigue- Grey hair- Low immunity B6 (pyridoxine) Fish, liver, milk, potatoes – Coenzyme in amino acid metabolism- For red blood cell formation – Kidney stone- Muscular twitching- Diarrhea B9 (folic acid)

Green vegetables – For DNA and RNA- For red blood cells formation- Regulating the function of iron – Miscarriage birth- Cleft lips- Limb defects of babies B12 (cobalamin) Cheese, milk, egg, meat – Coenzyme in nucleic acid metabolism – For red blood cells formation – Pernicious anaemia- Neurological disorders H (biotin) Legumes, vegetables – Coenzyme in the synthesis of fat, glycogen and amino acid – Nausea- Fatigue- Muscular pains C (ascorbic acid) Orange, tomatoes, broccoli, cauliflower – Fats and protein metabolism – Energy production – Scurvy (bleeding gums and bruised skin)

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