Lecture 8 Flashcards
1
Q
Describe the quaternary structure
A
- some proteins contain more than 1 polypeptide chain
- interact through non covalent interactions and covalent bonds
- each polypeptide chain in a protein is called a subunit
- subunits can be identical or different
2
Q
Name 2 proteins with a quaternary structure
A
- CAP: composed of 2 identical subunits
- Hemoglobin: composed of two identical a subunits and two identical b subunits
3
Q
What are protein families? And give an example
A
- proteins that are grouped in protein families where each member has an amino acid sequence and 3D conformation that closely resembles each other
- arise over time during evolution
Ex. chymotrypsin and elastase (differ in substrate specificity)
4
Q
How do proteins form large assemblies
A
- through subunits which bind to one another
5
Q
What is a ligand?
A
- any substance bound by a protein
- protein ligand interactions are dictated by non-covalent bonds
6
Q
What is a binding site?
A
- region of protein that associates with a ligand
- formed by a specific arrangement of amino acid side chains that may not immediately adjacent to one another in the polypeptide chain
7
Q
What are antibodies
A
- Y shaped molecules that are composed of two heavy chain and two light chains
- binds very specifically to a target molecule called an antigen
- it has to antigen binding sites where the amino acid sequence is highly variable
- there are billions of different possible antibodies
8
Q
Why are antibodies important?
A
- important for fighting infections
- important laboratory tool
(identification, quantification, localization)
9
Q
What is an enzyme
A
- it is a biological catalyst which speeds up the rate of a reaction by lowering the activation energy
10
Q
Enzyme bind to a _____________ forming a ________________. After the reaction has proceeded, the enzyme will be in contact with the product as an _________ and will eventually release a _______________
A
- substrate
- enzyme-substrate complex
- enzyme-product complex
- product
11
Q
What is an active site
A
- the region of an enzyme that binds and catalyzes the substrate
12
Q
Why are enzymes so large?
A
- to provide folding framework for active site
- precisely align active site residues
- optimize binding energy in the transition state
13
Q
What is the activation energy
A
- the energy required to go from ground state to transition state
14
Q
What is a transition state
A
- the maximum energy species formed on the reaction coordinate
15
Q
How do enzymes lower the activation energy
A
- align substrate in favourable orientation
- rearrange the electron distribution
- physically strain the substrate to induce a reaction
