Proteins
Food Preparation & Nutrition: AQA GCSE, topic 2.1.1
Why Do We Need Protein?
Protein is a type of macronutrient. A macronutrient is a type of food that we need lots of in our diet. Foods like eggs, chicken, salmon and milk all contain protein.
Amino acids
- Amino acids, which are sometimes referred to as the body's 'building blocks', make up proteins.
- The human body can only produce some types of amino acids (non-essential) so we must eat the ones our bodies can't produce (essential).
Uses of proteins
- Growth - general body growth as well as the growth of specific body parts, like muscles, bones and skin.
- Repair - mending organs, muscles and tissues after we get ill or are injured.
- Maintenance - producing antibodies to prevent illness and enzymes to help digestion.
- Secondary source of energy - if the body doesn't have enough carbohydrates and fats, protein can be used as a reserve energy source.
Low and High Biological Value Proteins
Not all proteins have the same biological value.
High biological value (HBV) proteins
- Have all the essential amino acids that humans need.
- Mostly located in animal sources (like chicken, salmon etc.)
- Soya beans also contain HBV proteins.
Low biological value (LBV) proteins
- Don't contain all the essential amino acids that humans need.
- Only located in plant-based foods.
- E.g. cereals, pulses, nuts etc.
Protein complementation
- Protein complementation is a way of making sure that we get all the essential amino acids we need in our diets. It involves combining various LBV proteins.
- E.g. peanut butter and wholegrain bread are both lacking some essential amino acids. But a peanut butter sandwich gives us all the necessary essential amino acids.
Test yourself on Proteins
What are proteins made up of?
What are HBV proteins?
In which type of food would you find high biological value proteins?