Biological Molecules

This lesson covers:

  1. What the different biological molecules (nutrients) are, including carbohydrates, lipids, proteins, vitamins, mineral ions, fibre and water. 
  2. Which foods each biological molecule is found in
  3. Why we need each type of biological molecule

Note that you do not need to know all of the details of the vitamins and minerals, we have included them as examples to help you understand what they do. 

Illustration of a basket containing healthy foods including vegetables, cheese, and fruits.

Balanced Diet


A balanced diet is a diet that includes appropriate proportions of all the different biological molecules, including carbohydrates, proteins, lipids, vitamins, minerals, dietary fibre, and water. 

Too much or too little of any of these could lead to problems. For example, too much food in general could lead to obesity, but a lack of any particular one could lead to a deficiency disease such as scurvy.

Illustration showing blueberries, cheese, and an apple as sources of energy.

How much energy do we need?

We get energy from the food we eat. Although carbohydrates are our main source of energy, lipids are also used for energy, and even proteins can be broken down for energy if necessary.

As in physics, we can measure energy in Joules (J). However, in the case of food, we often use calories instead.

Illustration showing the energy content of an apple with 502 kJ and 120 kcal.

How much energy we need each day depends on a lot of things, but there are 3 main factors to consider:

  1. Activity level - The more active you are, e.g. if you're an athlete, the more energy you need.
  2. Age - Teenagers often need a lot of energy because they're growing, whereas elderly people need less. 
  3. Pregnancy - Pregnant women need more energy because the baby growing inside them requires a lot of energy.


Which 3 of the biological molecules below do we need in large quantities?

(Select all that apply)

Lipids 

Carbohydrates 

Vitamins 

Proteins 

Minerals 

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Diagram showing the molecular structure of a carbohydrate.

Why do we need carbohydrates?

To help food move through our intestines 

To insulate us and regulate our body temperature

To provide energy for chemical reactions 

To repair damaged tissue

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Fats and oils together make the food group known as:

Lipids

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Why do we need lipids?

(Select 2 options from the list below)

To insulate us and regulate our body temperature

To help food move through our intestines 

To provide energy for chemical reactions 

To repair damaged tissue

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lipids / carbohydrates / proteins 

 

  1. Starchy foods like potatoes, bread, and pasta contain a lot of .
  2. Meat, fish, and legumes contain a lot of .
  3. Cheese, nuts, and avocados contain a lot of .
carbohydrates
proteins
lipids

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Illustration showing various food groups in a basket and their role in producing new cells.

Which food group is the most important for growth and producing new cells? 

Mineral ions 

Proteins 

Carbohydrates

Lipids 

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Which vitamin or mineral ion is important for good vision and healthy hair and skin?

Vitamin D

Calcium 

Vitamin A

Vitamin C

Iron

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Illustration of a bone representing the importance of minerals for strong bones.

Which mineral is important for strong bones?

Calcium

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Illustration of vitamin C deficiency with vitamin C tablets.

Which disease can be caused by lack of vitamin C?

Scurvy

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Illustration showing the importance of iron in the diet with a focus on iron-rich vegetables.

Explain why it is important that we get enough iron in our diet. 

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Why do we need fibre?

To provide energy for chemical reactions 

To help food move through our intestines 

To reduce the risk of dehydration

To prevent us from getting rickets 

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Illustration of a water droplet with a blue outline.

What are the 3 main ways by which we lose water from the body? 

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Illustration of a person cycling in sunlight to represent vitamin D absorption.

Which vitamin or mineral ion helps us to absorb calcium, and can be made by the body, using sunlight?

Vitamin C

Vitamin A

Calcium 

Iron

Vitamin D

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