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Biology 12 Enzymes Cheat Sheet (DRAFT) by

This is a draft cheat sheet. It is a work in progress and is not finished yet.

Enzymes Beginning

Enzyme
This is basic defini­tions for enzyme
 
Is a catalyst basically substance that speeds up a reaction without being consumed
 
Are proteins are reusable
 
Work in low concen­tra­tions
 
Speed up reaction rate
 
Allow reactions to proceed at lower temper­atures than they would normally occur
 
Reactants that enzymes act upon is known as substrates
 
Enzyme work by forming very temporary complex with substrate
 
This is called enzyme substrate complex
 
Are large globular proteins
 
Very specific 3d shapes tertiary structure
 
They have groves or pockets which contain chemically functional groups
 
(Relating to above defini­tion) These are called active sites, this is where substrate attaches
What goes into what
If amylase added
Starch ---> Glucose
If lipase added
Lipids ---> Fatty acids and glycerol
If protease added
Proteins ---> Amino Acids

Feedback Inhibition & control of metabolic rate

Feedback inhibition
 
When concen­tration of final product gets low again there will be less inhibition on the enzymes and the metabolic pathway is reacti­vated
 
Thyroxin the hormone that controls the metabolic rate of all of the cells in your body, is producde by the hyroid gland in the neck
 
Thyroid gland is stimulated to release thyroxine by a hormone produced in the pituitary gland called TSA (thyroid stimul­ating hormone)
 
Enzymes in cell of the pituitary that make TSH are inhibited by thyroxin
 
Therefore if thyroxin levels are high the pituitary stops producing THS and if thyroxin levels are low the pituitary makes the TSH
 
Thus metabolic rate of cells in your body are maintained by the feedback inhibition of an enzyme

Metabolism and ATP

Metabolism and ATP
 
Most cell reactions (Metab­olism) require energy to occur.The energy 'currency' of cells is a molecule called ATP
 
ATP has 3 phosphates the last two of which are held together by a high energy bond
 
It takes a lot of energy to make this phosphate bond and energy is released when bond breaks
 

Lock and Key Model

Lock and Key Model
This model is now incorrect
 
Enzymes have goove shapes and chemical groups
 
Groove shapes and chemical groups are in active site
 
Therfore enzymes can only bond with one specific substrate or reactive
 
When substrate and enzyme join together the shape of the enzyme changes which makes it more reactive
 
This is called induced fit not one to one
 
Why Wrong
 
Because there can be more than one substrate

Anabolism & Catabolism Metabolism

Anabolism & Catabolism
 
The active site of an enzyme is not an exact perfect fit to substrate
 
When substrate attaches to enzyme this causes stress in the substrate which causes
 
Catabo­lism:Is when substrate to break apart in a hydrolysis reaction molecules into smaller ones
 
Anabol­ism­:When two substrates to form a bond in a synthesis reaction putting small molecules together to make bigger ones
 
Anabolism + Catabolism = Metabolism
Metabolism
 
Metabolism is the constantly occurring chemical reaction that take place in a cell
 
These chemical reactions occur in organized sequences from reactants to end products with help of enzymes
 
This organized sequence of reactions is known as a metabolic pathway
 

Coenzymes

Coenzymes
 
Made up of two pieces
 
Apoenzyme - Protein portion (Inactive)
 
Co-enzyme - a non-pr­otein porton
 
When these two pieces join enzyme becomes active
 
Then substrate will now 'fit' into active site
 
Coenzymes usually fit into the allosteric site
 
allosteric site changes the shape of the active site so substrate 'fit'
 
co-enzymes are often large molecules
 
co-enzymes usually are things the body can't make on its own
 
most co-enzymes come from vitamens, which we get from food or supple­ments

Enzyme Action

Enzyme action
 
Usally heat can be used to speed up chemical reactions
 
Heat increases the number of collisions that occur between reactants
 
Excessive heat, however, destroys the tertiary structure of protein denatures it
 
So heat cannot be used to speed up reactions within living organisms
 
Enzymes operate by lowering energy of activation needed for reaction to occur
 
Enzymes act as catalyst and are not consumed in a reaction
 
This means they can be used over and over again
Factors affecting reaction rates
 
Concen­tra­tio­n:The amount of enzyme or substrate available to react can affect enzyme activity
 
The reactions speeds up as substrate increases
 
It levels out when the enzymes working at the speed (subst­rate)
 
So to increase reactions rates add enzymes
 
Reaction speeds up as you increase substrate the enzyme slows down as the enzymes are working at the maximum speed (Satur­ation)
 
Temper­atu­re:As temp rises reaction rate will increase cuz enzymes and substrates bump into each other more often (kinetic molecular theory)
 
The rate of these collisions will be at the fastest rate this is optimum temper­ature
 
If you get above the optimum temper­ature the enzyme becomes denatured (Changes shape) no longer functions properly
 
Most enzymes have an optimal temper­ature of 37C (Body temper­ature)
 
PH:3D shape of an enzyme can be affected by PH.
 
All enzymes have an optimal pG to work at depending on where they are in the body
 
Saliva pH 7
 
Stomach pH 2.5
 
Intestines pH 8.5
 
Vagina pH 3.8-4.0
 
When pH is too low the positive hydrogen ion with negative r group in protein and tear them away
 
The denatures the enzyme by changing its shape
 
When pH is too high the negative hydroxide interact with the positive r groups in protein and tear them away
 
This denatures the enzyme by changing its shape
 
Inhibi­tor­s:C­hem­icals that interfere with the enzyme action
 
Two types of Inhibitors
Compet­itive inhibitors
 
Are chemicals that so closely resemble an enzymes normal substrate that it can attach to the enzymes active site.
 
The substrate and inhibitor compete
 
If the inhibitor occupies the active site of enzyme substrate will not be able to join and no product will from that enzyme
 
If inhibitor is removed the enzyme will become active again
Non-Co­mpe­titive inhibitors
 
Atoms or molecules that attach to an enzyme at an allosteric site this denatures the enzyme
 
Will sometimes destroy an enzyme by perman­ently binding to the allosteric site
 
examples are:heavy metals, lead in nervous system
Other type of Non-Co­mpe­titive inhibitor
 
Inhibition is when a metabolic product can feedback on a metabolic pathway to control how much product is made
 
Final product can tempor­arily attach to the allosteric site on the first enzyme
 
Enzyme will be denatu­reated and the reaction will stop