IGCSE - Biology

Topics of Revision (year 9) :  

- Nutrition

- Digestion

- Enzyme

Nutrition

Definitions

DEFINITION OF NUTRITION

it is the taking in of nutrients which ar organic substances and minerals and vitamins containing raw materials or energy for growth and tissue repair

WHAT IS A BALANCED DIET?

It is a diet that provides all dietary needs and nutrients in the correct proportions

WHAT IS AN ADEQUATE DIET?

It is a diet that provides sufficient energy to meet the needs of a certain individual

DAILY CALORIE EXPENDITURE

It is an estimate to how many calories an individual burns per day

BMI

It is a standardised ratio of height to weight which indicates the general health of an individual e.g. overweight, obese, underweight or normal

Nutrients

What are the seven different types of nutrients?

Vitamins, minerals, fats, carbohydrates, water, fibre and proteins

DEFICIENCY DISEASES

VITAMIN C

scurvy, the symptoms are bleeding gums, gum inflammation, poor wound healing and loss of teeth. you can prevent it by consuming a lot of green vegetables and citrus fruits. vitamin C is important as it helps produce collagen, which helps heal wound faster.

VITAMIN D

rickets, symptoms are severe asthma, cognitive impairment in older wdults, cancer and increase risk of cardiovascular disease. we can prevent rickets by eating dairy products, fatty fish and going out under the sun, as the sun is one of the best providers of vitamin D. vitamin D is important as it helps to extract calcium from bones, which will then help to treat weaker bones in your body and strengthen them

IRON

the deficiency disease for iron is anemia, and the symptoms are weakness, impaired cognition, pale skin and dizziness. we can prevent it by eating dark green leafy vegetables and dried food. iron is important in the body as it helps produce haemoglobin, which helps transport oxygen throughout the body through red blood cells

CALCIUM

the deficiency disease for calcium is osteoporosis, and the symptoms are weakness, tingling of the fingers, cramps and poor appetite. we can preveng it by eating a lot of dairy foods, as dairy foods have high levels of calcium. calcium is important as is helps grow and strengthen bones and teeth, mineralisation of bones and the relaxation of cardiac muscles.

Food Tests

STARCH - the reagent for testing for starch is iodine. you have to drop a few drops of iodine on top of the food substance. a positive test would be a colour change to blue or black, but a negative test would have no colour change from orange brown.

PROTEINS - the reagent for testing for proteins is biuret solution. we add a few drops of biuret to a food solutin mixed with water. a positive test would be a colour change to lilac or purple.

Molecules

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