Biological molecules - Proteins ( enzymes ) Flashcards
What is an amino acid?
The monomer from which a protein is made
What is the structure of an amino acid?
They contain an amino group (NH2), carboxylic acid group (-COOH) and a variable R group which is a carbon-containing chain. The different amino acids are determined by their R-group.
How do amino acids join together?
By peptide bonds formed through condensation reactions.
What are dipeptides and polypeptides?
Dipeptides contain two amino acids and polypeptides contain 3 or more amino acids
How is the structure of a protein determined?
The order and number of amino acids, bonding present and the shape of the protein.
What is the primary structure of protein?
The number and order of the amino acids in a protein.
What is the secondary structure of a protein?
The shape that the chain of amino acids makes. The hydrogen in the -NH has a slightly positive charge and the oxygen in the -CO has a slightly negative charge. As a result weak hydrogen bonds can form leading to alpha helixes and beta pleated sheets.
What is the tertiary structure of proteins?
The 3D shape of a protein that is formed from twisting and folding. It involves disulfide bridges, ionic bonds and hydrogen bonds
Describe the bonds in the tertiary structure of proteins
Disulfide bridges - Interactions between sulphur in the R group of the amino acid cysteine.
Ionic bonds - Form between carboxyl and amino group that are not involved in the peptide bond. They are easily broken by pH and are weaker than disulfide bridges.
Hydrogen bonds - numerous and easily broken.
What are fibrous proteins?
Tertiary or quaternary proteins with a long rope-like shape. They are formed of polypeptide chains which are twisted around each other.
What are the properties of fibrous proteins?
- Stable structure
- Insoluble in water
- Strength gives structural function
Give examples of fibrous proteins.
Collagen in bone and keratin in hair.
What is a globular protein?
Tertiary or quaternary proteins with a spherical shape, formed by polypeptide chains rolling up.
What are the properties of globular proteins?
-Relatively unstable structure
- Soluble
- Metabolic functions
Give examples of globular proteins.
Enzymes, antibodies, some hormones and hemoglobin.
What is the function of an enzyme?
To increase the rate of reaction by lowering the activation energy.
What is the induced fit model of enzyme action?
When the enzyme-substrate complex forms, the structure of the enzyme is altered so that the active site of the enzyme fits around the substrate.
What is the effect of temperature on enzyme action?
The rate of reaction increases to the optimum temperature as the kinetic energy of the enzyme increases. Above the optimum temperature the rate decreases as the enzymes denature.
What is the effect of pH on enzyme action?
A pH that is too high or low will denature the enzyme. All enzymes have different optimum pH’s.
What is the effect of enzyme and substrate concentration on enzyme action?
Both will decrease the rate of reaction. If there is too little substrate, the enzymes can’t bind to them, and if there are too few enzymes the active sites will become saturated with substrate and unable to work any faster.
What is a competitive inhibitor?
An inhibitor that is the same shape as the substrate and can bind to the enzyme’s active site.
What is the effect of the addition of a competitive inhibitor on enzyme action?
The competitive inhibitors binding to the active site will prevent the substrate from binding to that active site, stopping the reaction from occuring. If enough substrate is added the inhibitor will be knocked out of the active site.
What is a non-competitive inhibitor?
An inhibitor that binds to the allosteric ( away from the active site ) site. This causes the active site to change shape, and therefore the substrate can no longer bind, regardless of how much substrate is added.
