Module 4: Proteins -Enzymes/Immune System Flashcards
Enzymes
catalyze biochemical reactions
make biochemical reactions go faster (reduces Ea)
do not get used up in the reaction
Gibbs Free Energy of Activation (Gǂ)
equal to the difference in Free energy between the Transition state and substrate (S)
Gibbs free energy change (G)
difference between substrate (S) and product (P)
deltaG free energy is negative…
reaction is favourable
proceeds in the forward direction
deltaG free energy is positive…
reaction is unfavourable
proceeds in the backward direction
enthalpy (H)
heat energy in the system
to decrease activation energy, activation enthalpy is more negative while the activation entropy is more positive
entropy (S)
measure of disorder
to decrease activation energy, activation enthalpy is more negative while the activation entropy is more positive
Catalytic site/active site
allows for tight binding of substrate in fixed orientation
How can enthalpy (H) become more negative?
accomplished by weakening C=O bond
can be done by adding positive charge R close to carbonyl ensuring active site scaffold better accommodates tetrahedral TS intermediate
How can entropy (S) become more positive?
binding substrate
free to fixed orientation
Lock and Key model
emphasized enzyme-substrate (ES) complementarity, however it did not delve into the details of how the ES complex goes on to form the product, P
binding not flexible/adaptive
Induced Fit model
conformational flexibility of the enzyme’s binding pocket
1) Conformation change in the enzyme results in moving the substrate towards its highly reactive transition state
2) Formation of the product very quickly leads to dissociation of the product from the enzyme active site and subsequent recycling of the enzyme for another reaction
Immune System
protect us from pathogens like bacteria, viruses and other foreign material that we encounter
Anatomical barriers
innate response
encounters pathogens before they get into our bloodstream and our cells
ex: skin, mucous membrane, stomach acid
Humoral barriers
innate response
mediated by substances found in our humours or body fluids
ex: inflammatory response
WBCs
separated from blood by centrifugation
found in a distinct white, fluffy layer between the red blood cells and plasma
B cells
involved in humoral immunity
synthesize and secretes the antibodies which can then bind to specific parts of the invading pathogen
results in aggregation of the pathogen (marked for destruction)
T cells
involved in cell-mediated immunity
Antibody
Y shaped protein molecule produced by B-cells whose function is to recognize and bind to specific antigens
Antigens
specific parts on an invading pathogen that antibodies bind to
elicits an immune response
Immunoglobulin G (IgG) (Antibody structure)
abundant protein in blood serum
- 2 identical light chains and 2 identical heavy chains
- Disulfide bonds hold the two heavy chains and the heavy and light chains together
- Hinge region that affords flexibility
- Constant domain: identical in all antibodies of a given class
- Variable domains: variable region important for antigen recognition and binding
- Y fork contains 4 variable regions=2 identical antigen binding sites
Fab fragments
contain the antigen binding sites of the antibody
only one binding site/fragment
Fc fragments
contains remainder of two heavy chains
contain the constant domains
No antigen bound…
closed conformation of antigen binding cleft
Antigen bound…
conformation change
hydrophilic region enlarged and shift of aa
