Balanced Diet   

A balanced diet is one which provides the correct quantities of nutrients for the body's cells tissues and organs and for supporting normal growth and development.  

It requires carbohydrates, proteins, fats, vitamins, minerals, fibre and water.    

Carbohydrate - broken down into slow release energy.

Fat - used for energy, insulation and protection.

Protein - used for growth, repair and the building of amino acids.

Vitamins - used for antioxidants .

Minerals - used for enzyme function

Fiber - used as an aid for digestion

Deficiency Diseases  and Imbalanced Diet Deficiency diseases occur when not enough of a particular substance is consumed by the body. These include :

Scurvy - Lack of vitamin C  

Rickets - Lack of calcium

Anaemia - Lack of Iron

Kwashionka - Lack of Vitamin D

When too much energy is consumed by the body the body converts this excess into fat. This can lead to weight gain and obesity which can be dangerous.

When too little energy is consumed by the body fat is used up. This leads to weight loss which can be dangerous.

Metabolic Rate  

Metabolic rate: The speed at which chemical reactions in the cells occur.  

The higher the amount of muscle the higher the metabolic rate this is because there are more mitochondria in cells.  

 Things that affect metabolic rate:

Pregnancy
Age
Muscle Content
Gender (Males have a higher metabolic rate)

Cholesterol  

Cholesterol is a necessary product of fats found in animal cells which is used to make cell membranes and hormones.  

 Lipoproteins   

Low density lipoproteins are bad as they carry cholesterol to your cells.  
High density lipoproteins are good as they carry excess cholesterol back to your liver.

Testing food You can test to see what food contains. You can test for starch, fat, sugar and protein.

Starch - Add iodine and if colour changes to black then starch is present.
Protein- Biuret test - add a few drops of dilute copper sulphate solution, followed by a few drops of sodium hydroxide. If solution turns violet then protein is present.
Fat - Emulsion test - Dissolve solution is ethanol. Pour this onto water and a white emulsion will form in the presence of fat.
Sugar - Benedict's test - add Benedict's solution to the substance you wish to test and gently heat for 2 minutes using a water bath. A colour change to orange indicates presence of a simple sugar.

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AQA GCSE Biology B1.1.1 Diet and Exercise notes.