Balanced Diet

This lesson covers:

  1. What carbohydrates, proteins, and lipids are made of

This lesson is about 3 types of molecules: carbohydrates, proteins, and lipids.


We call molecules like these 'biological molecules' and 'nutrients'.


Biological molecules are molecules found in living organisms, and are produced by cells.

Nutrients are substances that are needed for growth, repair, and metabolism.


The aim of this lesson is to understand what each of these molecules are made of.

Which of the following are biological molecules?

Carbohydrates

Proteins 

Lipids

Potassium ions

Sodium ions 

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Carbohydrates


Diagram of a carbohydrate molecule showing glucose structure with carbon, hydrogen, and oxygen atoms.

Carbohydrates are molecules made from atoms of carbonhydrogen, and oxygen.

(the carbohydrate in the image is glucose, you don't have to memorise it)

Illustration showing the synthesis of a complex carbohydrate from simple sugars.

Carbohydrates come in different sizes, with the smallest carbohydrates being simple sugars, such as glucose and fructose. We call these simple sugars 'monomers'. Carbohydrate monomers can join together to form carbohydrate polymers, such as glycogen and starch.

Diagram showing chemical bonds in carbohydrates.

In a complex carbohydrate, there are chemical bonds between the monomers. If these chemical bonds are broken, the complex carbohydrate can be broken down into simple carbohydrates (e.g. starch can be broken down into glucose molecules).

Diagram showing the digestion of carbohydrates in the mouth and small intestine.

This break down of complex carbohydrates into simple carbohydrates (simple sugars) is carried out by enzymes in the mouth and small intestine.

Which three elements are found in carbohydrates?

Nitrogen

Hydrogen

Phosphorus 

Carbon

Oxygen

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Carbohydrates are broken down in both the mouth and the small intestine.

True

False

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Is starch a type of carbohydrate, protein or lipid?

Carbohydrate 

Protein

Lipid

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Is glucose a monomer or a polymer?

Monomer

Polymer

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Is glycogen a monomer or a polymer?

Monomer

Polymer

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Proteins

Diagram showing amino acids as monomers forming a protein polymer.

Proteins are made up of long chains of amino acids bonded together. A protein is a polymer, whilst the amino acids it is made from are the monomers.

Icons representing carbon, hydrogen, oxygen, and nitrogen atoms.

Amino acids are mainly made from carbon, hydrogen, oxygen, and nitrogen atoms.

Diagram showing protein digestion into amino acids in the stomach and small intestine.

Enzymes in the stomach and small intestine break proteins down into amino acids.

What are the monomers that join together to form proteins called?

Amino acids

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Proteins are mainly made from carbon, hydrogen, oxygen, and which other element? 

Nitrogen

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Proteins are broken down in two organs, the small intestine and the .

stomach

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Lipids


Diagram showing the structure of a lipid molecule with a glycerol backbone and three fatty acid chains.

The term 'lipids' refers to both fats and oils. A fat is a lipid that's solid at room temperature, whilst an oil is a lipid that's liquid at room temperature. Lipids contain a single glycerol molecule attached to three fatty acid molecules.

Diagram showing the structure of lipids with a glycerol molecule attached to three fatty acid molecules.

These fatty acid molecules are often different lengths, and it's the length and structure of the fatty acid molecules that determines whether a lipid is a fat or an oil.

Diagram showing carbon, hydrogen, and oxygen molecules.

Lipids are made of carbon, hydrogen, and oxygen atoms.

Remember that lipids are not polymers, because they aren't formed from long chains of monomers. This is a key difference between lipids (not polymers), and carbohydrates and proteins (are polymers).

Diagram of the human digestive system highlighting the small intestine.

Enzymes in the small intestine are responsible for breaking lipids down inside the body.

The term 'lipids' refers to two groups of molecules: f and o

ats
ils

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Lipids are made from a single molecule and three fatty molecules.

glycerol
acid

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Lipids are only broken down in the:

small intestine

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