Higher Human BiologyUnit 1 – Cell Function and Inheritance

ProteinsThe Role of Enzymes

Success criteria

By the end of this lesson we will be able to:

1. State what elements are found in proteins

2. Describe what is meant by primary, secondary and tertiary structure of proteins.

3. Give examples of different types of proteins and their uses.

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Protein structureAim: The aim of this lesson is to

understand the structure of proteins, their component parts and their functions.

Success criteria

By the end of this lesson we will be able to:

1. State what elements are found in proteins

2. Describe what is meant by primary, secondary and tertiary structure of proteins.

3. Give examples of different types of proteins and their uses.

Protein elementsProteins are large organic

molecules made up of the elements Carbon, Hydrogen, Oxygen and Nitrogen.

Proteins will also often contain sulphur.

The whole pictureBall and stick model

Grey = CarbonRed = OxygenBlue = NitrogenYellow = Sulphur

Hydrogen not shown

Primary structureThe sub-units of proteins are

known as amino acids which are linked together into long chains by peptide bonds

Valine Leucine Isovaline Alanine

Valine Leucine IsovalineAlanine

Peptide bond

Primary structureThere are 20 exciting amino

acids to choose from when building a protein.

Build a proteinUse the amino acid blocks to

build a chain which is 20 amino acids long.

You can use an amino acid more than once.

Primary structureThe amino acids in the chain and

the order in which they appear is the primary structure of a protein.

In living things, this primary structure does not happen by chance but is coded for by DNA.

Valine Leucine Isovaline Alanine

Secondary structure

When the chain is complete it will be long.

Secondary structureWeak hydrogen bonds will form

between some amino acids in the chain making it coil into a helix.

Hydrogen bond

Secondary structureThe way a protein coils up into a

helix is the secondary structure.

When a protein winds up into a coil. This is called an ∂ Helix.Proteins with secondary structure are fibrous e.g. Collagen found in cartilage,tendon, skin, and bone.

Secondary structureHelices can also be twisted around each other layers with ‘thicken’ the connective fibres e.g. • Collagen – 3 alpha helices twisted together• Keratin which makes up hair -7 alpha helices twisted togetherThe diagram above shows the

three collagen helices twisted together

Tertiary structureProteins can also wind up into tangled shapes using a variety of additional bonds. This will form a globular protein.

Enzymes, hormones and antibodies all have a globular structure

Keratin in hair has disulphide bonds. If you light a single hair you will smell the sulphur

Tertiary structure

A globular protein can sometimes contain non protein parts in the tertiary structure. This forms a conjugated protein.

Non protein parts

Haemoglobin is an important oxygen carrying pigment with a conjugated structure containing iron

Examples of proteins

Protein name Type of protein Role

Collagen Fibrous Found in skin

Actin Fibrous Muscle cell filaments

Myosin Fibrous Muscle cell filaments

Amalase (Enzyme) Globular Breakdown of starch into maltose

Testosterone (Hormone)

Globular Produces male gender characteristics

Haemoglobin Conjugated globular

Found in red blood cells. Carries oxygen.

Now try the following

1. Name the elements are found in all proteins

2. Describe what is meant by each of the primary structure of proteins.

3. Name the bond between amino acids.4. What additional bond gives secondary

structures their shape?5. What is the main shape formed using

secondary structure?6. Give two examples of proteins made up

exclusively from proteins with secondary structure

7. Proteins can also take up a more complex tertiary structure. Describe this.

8. Give two examples of proteins with a tertiary structure and state what each protein is used for.

9. Haemoglobin is an example of a protein with a conjugated structure. Explain what is meant by this.

10. Give the level of structure and the function of each of the following

proteins:-

Actin Testosterone Keratin Haemoglobin