higher human biology unit 1 – cell function and inheritance proteins the role of enzymes
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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