4: Week sections 3.1-3.5, 4.1-4.3
What do proteins do?
- Defense. Proteins called antibodies and complement proteins attack and destroy viruses
and bacteria that cause disease
- Movement. Motor proteins and contractile proteins are responsible for moving the cell
- Catalysis
- Signalling
- Structure
- Transport
Amino acids and Polymerization:
- In every amino acid, a carbon atom is linked to a hydrogen atom , an amini group a
carboxyl group and a R group
- Amino acids link together to form proteins, nucleotides attach to one another to form
nucleic acid, and single sugars connect to form complex carbohydrates.
- Monomers polymerise through condensation reactions aka dehydration reactions,
Hydrolysis: water in, monomer out.
- The polypeptide babckbone , side chains present in each residue extend from it, it has
directionality and it is flexible.
- Oligeopeptide fewer than 50 or more amino acid
- 50 or more amino acids are called proteins
- Proteins can serve diverse functions in cells because they are diverse sizes and shape as
well as in the chemical properties of their amino acids.
- Every protein has a unique set of amino acids,
- Amount of free energy required to reach transition state = activation A energy
- substance that lowes the activation energy of a reaction and increases the rate of the
reaction is called a catalyst
- Interaction with the R groups at the active site stabilize the transition state and thus lower
the activation energy required for the reaction to proceed.
- Enzyme catalysis:
o Initiation: enzymes orient reactant precisely as they bind at specific locations
within the active site
o Transition state facilitation: stabalized by : change in enzyme shape, Interaction
b/w substrate and R groups lower activation E
o Termination: The reaction produce have considerably less affinity for the active
site than the transition state. Thus binding ends and enzymes return to thuer
original conformation and the products are released.
- Enzymes act with cofactors such as metal ions or small organic molecules call
coenzymes, they stabilize the transition state
- Competititive inhibition: a molecule similar in size and shape competes with substrates
for the active site of enzymes
- Allosteric regulation: regulatory molecule binds at a location other than the active site,
changes the shape of the enzyme
-
The activity of an enzyme often changes trastically as a function of temp and pH