Topic 1 - Proteins Flashcards
What happens in a reaction between two amino acids?
1) OH group from COOH end of amino acid react with H on amine end of 2nd amino acid.
2) In a condensation reaction.
3) Peptide bond forms between carbon and nitrogen.
What are amino acids?
Amino acids are a monomer of proteins.
What determines the type of the amino acid?
The ‘R’ group.
What is the primary structure of a protein?
The sequence of amino acids in a polypeptide chain.
What is the secondary structure of a protein?
Hydrogen bonding between different amino acids to form an alpha helix or beta pleated sheet.
What is the tertiary structure of a protein?
The folding of the polypeptide chain due to interactions such as ionic, hydrogen and disulfide bridges.
What is the quarternary structure of a protein?
More than one polypeptide chain held in 3D structure. Involves prosthetic amino acid groups.
What are the characteristics of fibrous proteins?
Insoluble, Long, Structural e.g keratin and collagen
What are the characteristics of globular proteins?
Soluble, Rounded (3D), Metabolic e.g enzymes and haemoglobin
What are the functions of enzymes?
Enzymes increase the rate of chemical reactions by acting as biological catalysts
What affect to enzymes have on activation energy?
Enzymes lower the activation energy of a reaction.
What is activation energy?
Activation energy is the amount of energy needed to be supplied to the chemicals for a reaction to start.
What determines the shape of the active site of a protein?
The tertiary structure
How can the tertiary structure of a protein be altered?
By changes in pH or temperature
Describe the lock and key model
1) Substrate collides with enzyme active site.
2) Substrate binds to active site.
3) Forms an enzymes substrate complex.
4) Bonds with substrate (reaction).
5) Products are released and the enzyme is unchanged.
Describe the induced fit model
1) Enzyme binds to substrate, forming ESC.
2) Binding causes a change in the bonds between R groups in the active site.
3) Enzyme change tertiary structure by stressing the bonds.
4) Reaction occurs.
5) Products are released, active site changes shape slightly.
How does temperature affect the rate of a reaction?
The rate of an enzyme controlled reaction increases when temperature increases.
How does temperature increase the rate of an enzyme controlled reaction?
1) The rise in temperature makes the enzymes molecules vibrate more.
2) If temperature goes above a certain level, vibration breaks some bonds that hold enzyme in shape.
3) Active site changes shape and enzyme and substrate fit together.
4) Enzyme is now denatured.
How does changes in pH affect a reaction?
Above and below the optimum pH, the H+ and OH- ions found in acids and alkalis can interfere with the ionic bonds and hydrogen bonds that hold the tertiary structure. This makes the enzymes active site change shape so the enzyme is denatured.
How does substrate concentration affect the rate of reaction?
1) The higher the substrate concentration, more substrate molecules, means that a collision between substrate and enzyme is more likely. Only true until the ‘saturation’ point.
2) Substrate concentration decreases with time during a reaction, so I& no other variables are changed, the rate of reaction will decrease over time too.
How does enzyme concentration affect the rate of reaction?
1) More enzyme molecules there are, more likely a substrate is to collide and form ESC. Increase in concentration of enzyme increases rate of reaction.
2) If amount of a substrate is limited, there comes a point where there’s more than enough enzyme to deal with substrate, more enzyme has no further effects.
Describe the process of competitive inhibition
Competitive inhibitor molecules have a similar shape to substrate molecules. They compete for the active site but no reaction takes place. They block the active site.
What affect does a high concentration of inhibitor have on competitive inhibition?
High concentration of inhibitor will take up nearly all active sites and hardly any substrate will get to the enzyme?
What affect does a high concentration of substrate have on competitive inhibition?
Higher concentration of substrate, chance increases, increases rate of reaction.
Describe the process of non-competitive inhibition
1) Non-competitive inhibitor molecules bind to the enzyme away from the active site.
2) This causes the active site to change shape to the substrate no longer binds.
3) They don’t ‘compete’ with the substrate molecules to bind to active site because they are a different shape.
4) Increasing concentration of substrate won’t make any difference to the reaction rate.
