ENZYMES Flashcards
What is an enzyme?
an enzyme is a biological catalyst. Catalysts are substances that speed up the reaction rate of chemical reactions without themselves being used up in the reaction
What are enzymes?
enzymes are globular proteins that are typically water soluble and spherical in shape, this is due to the amino acids with polar heads that are exposed at surface
What are monomeric enzymes ?
monomeric enzymes are enzymes which consist of a single polypeptide chain that is formed by amino acids. The folding and twisting of the polypeptide chain is the tertiary structure of structure which is stabilised by bonds
What are oligomers ?
Is when the enzyme consists of two or more polypeptide chains/subunits. The majority have this structure. Oligomers have a quaternary structure as they are made of subunits stabilised by covalent bonds. can have multiple active sites
What is an active site?
is a small pocket or cleft in an enzyme that binds temporarily with specific substrate of that enzyme. consists of 3-12 amino acids organised into a shape. small in comparison
Define substrate
is any compound which an enzyme acts on. input to enzyme catalysed reaction
Define product
is the output of enzyme catalysed reactions
What bonds are the enzyme and substrate held together by
weak hydrogen bonds
How is the specificity of enzymes demonstrated ?
- absolute or substrate specify
- bond specific
- group specificity
Define absolute or substrate specificity
an enzyme can only act on one substrate only e.g. lactase can only hydrolyses fat sugar lactose
Define bond specificity
an enzyme can only act on one type of chemical bond
Define group specificity
an enzyme can only act on molecules with particular functional groups surrounding them e.g trypsin can only act on peptide bonds adjacent to amino acids
When and where does enzyme reactions occur?
Mosts enzymes act on substrates in solutions within cella of particular human tissues, therefore most enzymes are intercellular
Define proenzymes
Is the state in which enzymes exist inactively in cells. These are enzymes that are only activate sin response to relevant signals
What do proenzymes help achieve?
prevents enzyme activity occurring at inappropriate times or places causing damage
What are the two theories related to enzyme specificity
- Lock and Key
- Induced fit model
What are the key ideas of the lock and key model
- Lock = enzyme, Key= substrate
- only correctly shaped key can fit in lock
- identifies the importance of the complimentary shapes of active site of enzyme and specific substrate
- assumes active site is fixed and rigid
What are the key ideas of the induced fit model
- active site has a defined shape although with a degree of flexibility
- changes shape to tightly fit around substrate
- bingeing site of enzyme- not exactly complimentary
- when reaction is complete the empty active site returned stock relaxed state
Define metabolism
metabolism is the total of all chemical l reactions occurring in an organism. almost without exception every step in metabolic pathway is catalysed by enzyme
What are the two ain aspects of metabolism
catabolism and anabolism
Describe anabolism
Is a series to cellular reactions in which complex molecules required by cells are synthesised from smaller building blocs-> requires energy
Describe catabolism
Is a series of cellular reactions that release useful energy from the breakdown of complex molecules
Define exergonic
metabolic reactions which release energy
Define endogenic
metabolic reactions which require energy
Define activation energy
is the minimum amount of energy required to initiate a reaction
What is the relationship between enzymes and activation energy ?
enzymes lower the energy required to activate reactant molecules. they do this by binding to the molecules and positioning or bending them in a way that enables the breaking of existing bonds and formation of new ones more readily
What does the enzyme substrate complex dictate?
- the substrate it will bind to
- the reaction it will catalyse
- products that will be made
What are the main factors which effect enzyme activity ?
- Temp
- Enzyme concentration
- pH
- Substrate concentration
What happens to enzyme activity as temperature increases to 37 degrees?humans
an increase in tramper would cause an increase in the reaction rate. this is because the heating of the reactants cause the particles to move faster and more likely to collide with sufficient energy to overcome Ae.
What begins to happen as the temp increases over optimum temp ?
The level of reactions will decrease and become less effective. at some point in time denaturing of the protein begins to occur permanently damaging the active site of an enzyme
what happens to enzyme activity when temp decreases to below optimum level?
Rate of reaction decreases as the enzyme and substrate molecules do not have sufficient energy to interact
What is pH?
concentration of hydrogen ions per litre of solution
How does a change in pH levels from optimum level effect enzyme reaction ?
If the pH levels changes from optimum levels it can result in the intermolecular bonds being altered which in turn may change the shape and efficiency or even permanently damage the acute site
What is the effect of substrate concentration on enzyme activity ?
The addition of more substrates to an enzyme solution initially increases the rate of reactions provided that some on the active sites are not occupies. reaction tapers once all enzymes are occupied
What is the effect of enzyme concentration on enzyme activity ?
Enzymes are not usually consumed in reaction and therefore do not need large amounts. provided that substrate concentration is high and temp and pH are kept constant rate or reaction is proportional to enzyme,es
Define enzyme inhibiotor
is a molecule that binds to an enzyme, reducing activity by interfering with the enzyme in some way
What is irreversible inhibition ?
of an enzyme occurs when a compound binds covalently to one or amino acids ad alters the structure of the enzyme,e therefore affecting the active site. this permanently inhibits the enzyme as the bond is too strong to be reversed
What is reversible inhibition?
when the enzyme is not permanently damaged . Inhibit enzymes through non covalent interactions that can be reversed. were are two types competitive and non-competitive
Define competitive inhibition
competitive enzyme inhibitors have a similar shape to the usual substrate molecule and binds to the active site to prevent ES complex. as a. result fewer substrates binding to active site
Define non-competitive inhibitors
do not bind to the active site but bind to another site on the enzyme molecule called the allosteric site.the binding of the non competitive inhibitor distorts the 3D shape of the active site
What are cofactors ?
Additional non protein groups that are needed for enzymes to function properly. important to contributing to stabilising and activity
What are inorganic cofactors ?
metal ions such as Fe^2+ or Mg^2+
What are organic cofactors ?
prosthetic= tightly bound heme group groups and coenzymes , NAD, NADP, ATP
