U4AOS2 - Metabolism of food in the human body Flashcards
(46 cards)
Structure of Enzymes (inc. how specific they are)
Made up of Proteins
Contain an active site - where the substrate (reactant(s) of a reaction) can bond.
Molecules that the active site will accept are very specific - therefore, enzymes will often only catalyze one or a very small number of reactions (this is unlike inorganic catalysts - which are generally not specific)
Enzyme-Substrate Complex
Purpose of Enzymes (inc. how they accomplish it)
To act as biological catalysts, and to increase the rate of reaction in the body
They accomplish it by providing alternate reaction pathways with a lower activation energy
- this means a greater proportion of molecules will have enough KE to breach the activation energy
- speeds the reaction up
Do enzymes change the amount of product produced?
No - they only increase the rate of reaction
3x Main Points for Enzyme Function
- Specific Active Site for a Specific Substrate
- Interactions weaken the intermolecular bonds of the products, lowering activation energy
- this allows the reaction to occur - forming the products
Are enzymes modified over the course of a catalyzation
No - the enzyme remains unchanged at the end of the reaction (regardless if lock-and-key, induced fit, coenzymes)
Effect of optical isomers on enzymes
Enzymes typically will not accept optical isomers - generally two separate enzymes will be required
Enzyme Lock-and-Key Model
States that only substrates that perfectly fit the active site can bond
(like a lock and key)
Enzyme Induced Fit Model
Suggests that the active site of an enzyme is more flexible
Suggests that the shape of the active site may change shape slightly to fit the substrate
however - at the end of the reaction - the substrate will return to its original position
Why do enzymes experience denaturation?
Because, enzymes themselves, are proteins
Effect of Temperature on Enzymes (inc. high/low/optimal temp)
If temp is lowered - rate of reaction will be too slow
If temp is raised - the protein will begin to denature (as a result of more vibration)
This results in optimum temperatures - where the rate of reaction is highest, without any breakdown in the structure of the protein (generally body temp for humans)
Effect of pH on Enzymes
Changing pH will modify the structure of the enzyme (same with proteins in acids or bases).
Given that enzymes and substrates can bond ionic-ly, if the pH becomes acidic or basic, the enzyme may be unable to bond to substrates
Hydrolysis of Proteins (inc. process and purpose)
Process of chemically digesting proteins
Amide Links (peptide links) will be broken, splitting the protein into amino acids (and consuming water).
(PRIMARY STRUCTURE)
Purpose: to allow the amino acids, which are polar, to travel through the bloodstream, where they can be assembled into a new protein at the required location
Enzyme that catalyzes the hydrolysis of proteins
Protease - type of enzyme that will help to break down proteins
A common one is pepsin
Effect of adding HCl (in the presence of pepsin) to Proteins (and sometimes heating)
Results in the hydrolysis of the protein
- the HCl is the source of H+,
- the enzyme catalyses the reaction
- the heat can increase the rate of reaction
heat and change in pH are the two main reasons for denaturation
Denaturation
disruption or destruction of the secondary, tertiary, (and quaternary only if it’s present)
results in the unfolding of the protein, disrupts the 3D shape, and disables the functionality of a protein
Denaturation vs Hydrolysis of Proteins
Denaturation disrupts secondary, tertiary (and quanternary structures - if present)
VS
Hydrolysis which only disrupts the primary structures
Heat as a cause of denaturation (inc. reversibility)
heat -> increases kinetic energy of molecules
if the kinetic energy is high enough -> the molecules can vibrate so rapidly that the secondary and above bonds can be disrupted
if the heat is raised high enough - this is not reversible
Real life example of heat based denaturation
heating medical supplies to denature the proteins in bacteria - as denatured proteins have less biological activity - and so are no longer harmful
pH as a cause of denaturation (inc. reversibility)
when pH changes, the ionic interactions change (as the acid/base properties change)
if the pH deviates too far from its optimum pH, the denaturation may be irreversible
Real life example of pH based denaturation
Vinegar is often used when boiling an egg, as it’s an acid
this lowers the pH of the solution, denaturing the eggs proteins
Step 1 of Hydrolysis of Starch
Occurs in the mouth, starch (either amylose or amylopectin) is hydrolyzed by saliva in the mouth, which contains the enzyme amylase
This converts starch into maltose (a disaccharide)
Step 2 of Hydrolysis of Starch
The maltose is then hydrolyzed into glucose, with maltase as the enzyme
Why can amylase operate in the mouth, but not the stomach?
The optimum pH of Amylase is 6, but the pH in the stomach is about 1.5
so the amylase enzyme undergoes denaturation
