SPM Biology Form 4 Notes – Nutrition (Part I)
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.
* 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
* 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
Carnivorous plants (Holozoic nutrition)
| Venus traps and pitcher plants
| Lice and fleas
* 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)
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...
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