Proteins

This deck contains content from 3.1.4 Proteins

What is the structure of an amino acid?

• Amino group

• Carboxyl group

• Central carbon and hydrogen atom

• Variable R-group

What is the biological term for proteins?

Polypeptide

What is the monomer for proteins?

Amino acids

What bond is formed between the monomers of proteins?

Peptide bond

Where does the peptide bond form?

Between the hydroxyl from the OH from the carboxyl group of one amino acid and the H from the amino group of another one

How does a peptide bond form to make a dipeptide?

Condensation reaction

What are the four structures of proteins?

• Primary

• Secondary

• Tertiary

• Quaternary

What is the primary structure of a protein?

The specific sequence of amino acids in a polypeptide chain

What bonds are present in the primary structure?

Only peptide

What does the primary structure determine?

The shape and function of the protein

What is the primary structure determined by?

The sequence of DNA bases

What is the secondary structure of proteins?

The basic level of folding in a protein

What bonds are within the secondary structure?

• Hydrogen bonds

• Peptide bonds

Where did the hydrogen bonds form in the secondary structure?

Between the carboxyl groups and the amino groups in the polypeptide backbone

What are the two types of secondary structure?

• alpha-helix

• beta-pleated sheet

What is the tertiary structure of proteins?

The further folding of the alpha-helix into a complex, 3D structure

When is a polypeptide classified as a protein?

In the tertiary structure

What bonds are within the tertiary structure?

• Peptide bonds'

• Hydrogen bonds

• Ionic bonds

• Disulfide bonds

• Hydrophobic interactions

What do the positions of the bonds depend on?

The primary structure

What are stronger, Ionic bonds or disulfide bonds?

Disulfide bonds

What is the quaternary structure of a protein?

More than one polypeptide chain with a prosthetic group

What is a prosthetic group?

Non-protein groups associated with the molecule

What are the two types of protein?

• Fibrous

• Globular

What are fibrous proteins?

Structural proteins

What are globular proteins?

Functional proteins

What are the four functions of proteins?

• Enzymes

• Antibodies

• Transport Proteins

• Structural Proteins

What is the test for proteins called?

The Biuret Test

What is the method for the test for proteins?

1. Place a sample in a test tube and add NaOH

2. Add a few drops of biuret solution and mix gently

What is the positive result for the test for proteins?

A colour change from blue to lilac

What shape are globular proteins?

Roughly circular

What shape are fibrous proteins?

Long strands

What is the amino acid sequence of globular proteins like?

Irregular, with a wide range of R-groups

What is the amino acid sequence of fibrous proteins like?

Repetitive, with a limited range of R-groups

What is the functionality of globular proteins?

Physiological/functional

What is the functionality of fibrous proteins?

Structural

What are some examples of globular proteins?

• Haemoglobin

• Enzymes

• Insulin

• Immunoglobin

What are some examples of fibrous proteins?

• Collagen

• Keratin

• Actin

• Myosin

Are globular proteins soluble?

Yes, generally

Are fibrous proteins soluble in water?

Generally no

How many polypeptide chains are in collagen?

3 (triple helix)

What is the shape of collagen?

Long and thin

What type of protein is collagen?

Fibrous

What is the main function of collagen?

Structural (connective tissue)

Does collagen contain a prosthetic group?

No

What is haemoglobin made up of?

4 polypeptide chains, 2 alpha-globin and 2 beta-globin

What shape is haemoglobin?

Spherical

What is the function of haemoglobin?

Functional (transport of oxygen)

Does haemoglobin contain a prosthetic group?

Yes, a haem group