ENZYMES Flashcards
Define active site
Indented area on surface of enzyme molecule
Complementary shape to substrate molecules
Define catalyst
Chemical that speeds u the rate of reaction and remains unchanged and reusable at the end of the reaction
Define metabolism/metabolic
Chemical reaction that takes place inside living cells or organisms
Define product
Molecule produced from substrate molecule by an enzyme
Define substrate
Molecule that is altered by an enzyme catalysed reaction
Define metabolites
Reactants immediate and products in enzyme controlled reactions
What type of protein are enzymes?
Globular
Shape determined by tertiary structure
What does intracellular mean?
Enzymes work inside cells, most catalysing reactions that occur in series
What does extracellular mean?
Enzymes work outside the cells, catalysing hydrolysis reactions to break down macromolecules into small, soluble molecules that can be absorbed `
What is an example of intracellular enzymes?
Catalase protects cell from damage by reactive oxygen by breaking down hyperovide into water and oxygen
What is an example of extracellular enzymes?
Amylase- salivary glands, digest starch into maltose
Trypsin- pancreas acts in lumen of small intestines to digest proteins into smaller peptides by hydrolysing peptide bonds
How do enzymes work?
Speed up metabolic reactions
Enzymes make substrates into products and the reactions are either:
Catabolic- substrates broken down
Anabolic- substrate joined to form larger product
What does lactase break down into?
Glucose and galactose monomers
What does catalase break down down?
Hydrogen peroxide to water and oxygen
What is rubisco catalyse?
Binding of carbon dioxide to ribulose biphosphate in plants
What is activation energy?
Energy stored in bonds between atoms
Allow reactions= bonds break
Activation energy required
How is an anabolic reaction started?
If two molecules need to be joined, attaching to the enzyme holds them close together, reducing any repulsion between the molecules so they can bind more easily
How is a catabolic reaction started?
If enzyme is catalysing a breakdown reaction, fitting into active site puts strain on bonds in substrate
Strain means substate molecule breaks up more easily
What is meant by lock and key?
Complementary shape of active site and substrate molecule are like lock and key Enzyme + substrate enters active site Enzyme-substrate complex Enzyme-product complex Product (older model)
What its mean by induced fit?
Enzymes active site changes slightly upon collisions, active site fits closer to substrate Substate entering active site or enzyme Enzyme-substrate complex Enzyme-product complex Product leaving active site or enzyme
What is the kinetic energy and collision theory?
- KE means collisions happen at random
- as fluid heated= more KE= molecules move faster= more frequent collisions
- collisions occur with more energy (travelling faster) so collide with a greater force
- enzyme-substrate complexes only form when substate molecules collide with active site of enzyme
- if KE of both molecules has increased, there will be more collisions= increase rate of reaction and more product formed
What is denaturation?
Where the tertiary structure of enzyme is changed to the point that the enzyme doesn’t work
What is the effect of heating?
- molecules vibrate, vibrations strain bonds holding molecule together
- vibrations can break hydrogen and ionic bonds
- said bonds are vital in keeping active site shape and tertiary structure
- as heat increases, more bonds break and thus lowers the rate of reaction
What is the formula for working out the rate of reaction?
1/time taken to reach end point
What does the temperature coefficient refer to?
The increase in the rate of a process when the temperature is increased by 10 degrees
Q10= rate of reaction (T+10) degrees/rate of reaction at T-degrees
What does pH measure?
Measure of H+ ion concentration
Higher the H+ ion concentration, the lower the pH value
H+ ions affect the ionic and hydrogen bonds in tertiary structure because of their piste charges
0-6= acidic (low pH)
8-14= alkali (high pH)
What are buffers?
Resist changes in pH
Whats the affect of pH on enzymes
Higher the H+ ion concentration the lower the pH value
H+ ions affect the ionic and hydrogen bonds in the tertiary structure because of the positive charge
Explain optimum pH on enzymes
Max rate of reaction
Concentration of H+ ions gives the tertiary structure the best shape- complementary active site to substrate shape
Explain pH and denaturation on enzymes
Minor changes don’t denature enzymes, the bonds are disrupted bu can reform if the pH returns to the optimum
Denaturation only occurs in extreme pH changes away from the optimum
Define a cofactor
Aids certain enzymes as some will only work with a non protein substance bound to them
Explain an inorganic cofactor
Not permanently bound to the enzyme
Help enzyme and substrate bind together, increasing rate of reaction
Don’t participate in reactions so aren’t used up or changed
Explain organic cofactors
Small non protein molecules that bind temporarily to active site
Take part in reactions and are changed in some way
Recycled and used again
Define enzyme inhibitors
Substance or molecule that slows down rate of reaction
Their effects can be reversible or irreversible
How do strength of bonds determine if an inhibitor is reversible or irreversible
Covalent- can’t be easily removed, irreversible
Hydrogen/ionic- weaker, able to be removed, reversible
Explain a competitive inhibitor
Similar shape to substrate
Compete with substrate to bind to active site, no reaction takes place
Block active site
High conc of inhibitor will take up nearly all the active sites
Explain a non-competitive inhibitor
Bind to molecule away from active site- region known as allosteric site
Causes change to tertiary structure
Causing active site to change shape so substate can’t bind to it
Decreases rate of reaction
Increasing conc of inhibitor will make no difference as enzyme will still be inhibited
How do medicinal drugs work
Exploit enzymes to treat illnesses and location they are applied to
Briefly state and explain some drugs and their functions
Aspirin- salicylic acid binds to enzymes to form prostaglandins, lack of prostaglandins means nerve cells and muscle tissues are less sensitive
ATPase inhibitors- Inhibit NA-K pump in cell membranes of heart cells, allowing calcium to enter, calcium increases muscle contractions which strengthens heart beat
Explain metabolic poisons
Interfere with metabolic reactions causing damage or illness
Cyanide- noncompetitive- inhibits cytochrome C (catalyses respiration reactions)
Malonate- competitive- succinate dehydrogenase (catalyses reparation reactions)
What is venom
Mixture of toxins and different enzymes
E.g:
Phosphodiesterase- interferes with heart causing drop in blood pressure
ATPase- breaks down ATP, disrupts prey’s use of energy
