Proteins and enzymes

What’s the monomer that makes up proteins?

Amino acids

What’s the general structure of an amino acid?

Amine group, carboxyl group, R group and hydrogen joined to central carbon

What bond holds amino acids together?

Peptide bond

What makes up a dipeptide, polypeptide and protein?

Dipeptide = 2 amino acids; Polypeptide = more than 2 amino acids; Proteins = one or more polypeptides

What’s the primary structure of a protein?

Sequence of amino acids

What’s the secondary structure of a protein?

Primary structure/chain of amino acids coiled and folded with hydrogen bonds into an alpha helix or beta sheet

What’s the tertiary structure of a protein?

3D structure; Chain of amino acids coiled or folded further; Hydrogen and ionic bonds between dipoles on molecule; Disulphide bridges between sulphur atoms; Hydrophobic interactions

What’s the quaternary structure of a protein?

Several different polypeptide chains interacting together with prosthetic group (e.g., haem group in haemoglobin)

What are enzymes and their function?

Proteins and biological catalysts that lower the activation energy

How do enzymes increase rate of reaction through lowering activation energy?

Enzyme-substrate complexes formed; In a joining reaction, they hold the two substrate close reducing repulsion so they bond more easily; In a breakdown reaction, the active site puts strain on bonds and breaks/distorts them so they break up more easily

What are the two types of enzyme inhibitors and what is their function?

Competitive: similar shape as the substrate, occupy active sites so no more enzyme-substrate complexes are formed; Non-competitive: binds to an area that’s not on the active site and alters its shape so no enzyme-substrate complexes form

What’s the effect of increasing substrate concentration when competitive and non-competitive inhibitors are involved?

Competitive inhibitor: increases rate of reaction because it’s more probable for enzyme-substrate complexes to form; Non-competitive inhibitor: little effect because the inhibitor doesn’t compete with substrates but still prevents enzyme-substrate complexes

What are the 3 factors affecting enzymes and their rate of reaction?

Temperature (optimum usually 37°C, denatures after this causing active site to change shape); pH (optimum pH 7, can denature if too acidic or alkaline); Substrate concentration

Describe induced fit model

Substrate binds to active site and enzyme-substrate complex is formed; Active site shape is slightly changed to mould around the substrate and become complementary; Substrate bonds are broken/made/distorted to lower activation energy