Proteins Flashcards
Draw the general structure of an amino acid and its’ zwitter ion.
Look at notes.
Why are there two different forms of amino acids and what are they called?
- Asymmetric molecules with a chiral carbon.
- Optical isomers/enantiomers
- Non-superimposable mirror images
What are the 3 protein types and give examples.
Globular - enzymes/antibodies
Fibrous - collagen/keratin
Membrane - channels/receptors
What are prions?
Infectious proteins
How do enzymes increase the rate of reaction?
- Biological catalysts
- Decrease activation energy
How do enzymes decrease activation energy?
- Position substrates in a way that alters bond configuration to resemble their form in the transition state.
- Bring substrates together and position them in the correct orientation to react.
What is an allosteric enzyme?
Allosteric enzymes are enzymes that have an additional binding site for effector molecules other than the active site.
Sketch a graph of an isoteric enzyme with increasing [S] until enzyme is saturated.
Look at images
Sketch a graph of an allosoteric enzyme with increasing [S] until enzyme is saturated.
Look at images
How are allosteric enzymes regulated?
Effector molecule binds to allosteric site which brings about conformational changes - can be an inhibitor or activator.
What is a competitive inhibitor?
Binds to enzyme site instead of the substrate (usually at the active site).
What is a non-competitive inhibitor?
Binds enzyme irrespective of whether substrate is bound (binds at an allosteric site).
List factors that regulate enzyme activity.
- Concentration
- pH
- Temperature
- Post-translational modifications
- Cofactors
What is post-translational modification (type 1)?
Activity of many enzymes is altered (very rapidly) by reversible covalent attachment of a small non-protein group.
What is the most common type of post-translational modification and what does to do?
Phosphorylation - causes changes in the secondary and tertiary structure of the enzyme – alters its catalytic ability.
What is post-translational modification (type 2)?
Proteolytic activation
What is proteolytic activation?
Several enzymes are synthesized as larger, inactive precursor forms (proenzymes or zymogens).
What are co-factors and their function?
- Small non-protein units e.g. inorganic ions like Mg2+ or coenzymes
- Some coenzymes are bound at the active site and are oxidised/reduced by the enzyme during its catalytic reaction
What are proteinases?
Enzymes which cleave proteins.
What are isoenzymes?
- Different forms of an enzyme, which catalyse the same reaction (therefore, active site similar).
- Usually derived from different genes.
What are multi-enzyme complexes?
Aggregation of several enzymes/coenzymes into a single functional unit.
What is the function of multi-enzyme complexes?
Usually perform a multi-step transformation.
Why is it useful to have close proximity of enzymes?
- increases overall reaction rate
- minimizes side reactions
- intermediates immediately available as substrates for next reaction
