Question 1

Enzyme

Accepted Answer

are substances that act as catalysts->they increase the rate of chemical reactions.-> once prod. is formed they leave active site of enzyme which is left free again->E. are NOT used up in reactions->can be used over and over again.

Question 2

Catalysts

Accepted Answer

increase the rate of chemical reactions

Question 3

Carbonic anhydrase

Accepted Answer

is one of the fastest enzymes-> catalyses following reaction: CO2 + H2O <=> H2CO3 //

Question 4

What does "Enzymes are specific" mean?

Accepted Answer

That each enzyme only catalyses ONE reaction

Question 5

Substrate

Accepted Answer

The substance with which the enzyme combines.

Question 6

Active Site

Accepted Answer

The particulat place where the enzyme combines with the substrate on the enzymes surface. (usually relatively small part of the enzyme->the rest of the enzyme is involved in maintaining the active site)

Question 7

Induced Fit

Accepted Answer

is the process that the shape of some active sites changes when the substrate molecule attaches to it.

Question 8

exotherm

Accepted Answer

chemical reaction which produces heat (ie. combustion)

Question 9

endothermic

Accepted Answer

chemical reaction which "takes" heat->absorb heat.

Question 10

Free energy

Accepted Answer

some energy that is produced dissipate (ie. heat, light) and is therefore not available for other processes. Other forms of energy can be used by organsim to drive other processes=>they are called "Free Energy"

Question 11

Exergonic

Accepted Answer

reaction only occurs spontaneously if "A"G is negative.

Question 12

Endergonic

Accepted Answer

reaction only occurs spontaneously if "A"G is positive->input of free energy is needed to drive reaction.

Question 13

Activation Energy

Accepted Answer

In living cells, most chemical reactions require input of energy before the molecules react together.

Question 14

The overall reactions between an enzyme and its substrate can be represented by following equation:

Accepted Answer

Enzyme + Substrate -> Enzyme-Substrate complex -> Enzyme + Product

Question 15

Turnover Number

Accepted Answer

the number of substrate molecules which an enzyme can act upon in a given time.

Question 16

equilibrium

Accepted Answer

reactions proceed from left to richt (or vice versa)->in time reactions reach a point where reactants and products are in equilibrium with one another. =>Enzymes catalyse the forward and reverse reactions equally.

Question 17

Enzyme concentration

Accepted Answer

enzymes work efficiently at very low concentrations as they may be used again and again. To work efficiently temperature & other conditions must be suitable.

Question 18

Enzyme Specificity

Accepted Answer

enzymes usually work on very specific substrates-> like a key->some are highly specific, others may not be so much: ie. will break particular chemical linkage wherever it occurs wheras others will only act on particular isomers.

Question 19

Substrate concentration

Accepted Answer

For a given amnt of enzyme the rate of an enzyme controlled reaction increases with increasing substrate concentration- up to a point.

Question 20

Enzymes - Temperature

Accepted Answer

has 2 main effects: 1. increase kenetice energy ->faster movement->more often substrate & enz. collide->greater rate of reaction., 2. atoms (which make up enzymes) vibrate->breaking up hydrogen bonds etc. ->shape of enz. is altered->active site no longer

Question 21

Denaturing

Accepted Answer

i.e increase of temperature->. atoms (which make up enzymes) vibrate->breaking up hydrogen bonds etc. ->shape of enz. is altered->active site no longer fits substrate->enzyme is said to be denatured->loses its catalytic property

Question 22

Definition pH

Accepted Answer

is a measure of hydrogen ion concentration (H+)->is usually measured on a scale of 1-14 with pH7 being neutral. pH less than 7 is acid, pH greater than 7 is alkaline

Question 23

Hydrogen ions

Accepted Answer

(H+)

Question 24

Kinetic Energy

Accepted Answer

Energy due to the motion of an object ->be translation (motion along a path from one place to another), rotation about an axis, vibration, or any combination of motions.

Question 25

Inhibitors

Accepted Answer

rate of enzyme reactions may be decreased by their presence->there are 2 main types: 1. reversible inhibtors, 2. non-reversible inhibitors

Question 26

Reversible inhibitors

Accepted Answer

effect is temporary and cause no permanent damage to enzymes, bcs their association with enzymes is loos->can easily be removed.

Question 27

Competetive inhibitors

Accepted Answer

Reversible inhibitors->active site-directed->compete with the substrate for active site of enzyme mol. ->their struct. combines with AS->therefore prevents substrates to occupy site->reduces rate of reaction

Question 28

Non-competetive inhibitors

Accepted Answer

Reversible Inhibitors->attach themselves not to the active site of the enzyme but elsewhere. ->they alter shape of E. that that the AS can no longer properly accomodate the substrate

Question 29

Non-reversible inhibitors

Accepted Answer

leave enzyme permanently damaged->E. are therefore unable to carry out their catalytic function.->ie. heavy metal ions such as mercury (Hg2+) and silver (Ag+) casue sisulphide bonds to break (those bonds help to maintain the shape of E. mol.)->permanent

Question 30

Cofactor

Accepted Answer

is a non-protein substance which is essential for some enzymes to function efficiently

Question 31

Activators

Accepted Answer

are substances which are necessary for the functioning of certain enzymes.

Question 32

Coenzymes

Accepted Answer

are non-protein organic substances which are essential to the efficient functioning of some enzymes, but are NOT themselves bound to enzymes. They are often derived from vitamines.

Question 33

Prosthetic groups

Accepted Answer

are organic molecules (like coenzymes), but they ARE bound to enzymes themselves.

Question 34

Classification of enzymes

Accepted Answer

are classified into 6 groups according to the type of reaction they catalise: 1. Oxidoreductase, 2. Transferases, 3. Hydrolases, 4. Lyases, 5. Isomerases, 6. Ligases

Question 35

negative feedback

Accepted Answer

This occurs where the products of a process can act at an earlier stage in the process to inhibit their own formation.

AS Biology - Enzymes

AS Biology - Enzymes - Chapter 3 - Book Molecules & Cells

Question	Answer	Answer
Enzyme	are substances that act as catalysts->they increase the rate of chemical reactions.-> once prod. is formed they leave active site of enzyme which is left free again->E. are NOT used up in reactions->can be used over and over again.	Enzymes greatly increase the rate of formation of a product ( A + B -> C) by a factor of at least 1 m. ->Enzymes are large globular protein molecules->E. are specific!
Catalysts	increase the rate of chemical reactions	(blank)
Carbonic anhydrase	is one of the fastest enzymes-> catalyses following reaction: CO2 + H2O <=> H2CO3 //	(blank)
What does "Enzymes are specific" mean?	That each enzyme only catalyses ONE reaction	(blank)
Substrate	The substance with which the enzyme combines.	(blank)
Active Site	The particulat place where the enzyme combines with the substrate on the enzymes surface. (usually relatively small part of the enzyme->the rest of the enzyme is involved in maintaining the active site)	The precise shape of AS is important as it is complementary to the shape of substrate molecule->"lock-and-key-mechanism"
Induced Fit	is the process that the shape of some active sites changes when the substrate molecule attaches to it.	(blank)
exotherm	chemical reaction which produces heat (ie. combustion)	Most reactions that occur spontaneously
endothermic	chemical reaction which "takes" heat->absorb heat.	(blank)
Free energy	some energy that is produced dissipate (ie. heat, light) and is therefore not available for other processes. Other forms of energy can be used by organsim to drive other processes=>they are called "Free Energy"	change in free energy is given the symbol "A"G, reaction only occurs spontaneously if "A"G is negative.
Exergonic	reaction only occurs spontaneously if "A"G is negative.	(blank)
Endergonic	reaction only occurs spontaneously if "A"G is positive->input of free energy is needed to drive reaction.	(blank)
Activation Energy	In living cells, most chemical reactions require input of energy before the molecules react together.	(blank)
The overall reactions between an enzyme and its substrate can be represented by following equation:	Enzyme + Substrate -> Enzyme-Substrate complex -> Enzyme + Product	(blank)
Turnover Number	the number of substrate molecules which an enzyme can act upon in a given time.	(blank)
equilibrium	reactions proceed from left to richt (or vice versa)->in time reactions reach a point where reactants and products are in equilibrium with one another. =>Enzymes catalyse the forward and reverse reactions equally.	->and do noth therefore alter the equilibrium itself, but only the speed at which it is reached.
Enzyme concentration	enzymes work efficiently at very low concentrations as they may be used again and again. To work efficiently temperature & other conditions must be suitable.	Provided there are excess substrate mol. the rate of a reactions is directly proportional to the enzyme concentration. ->if amnt is restricted it limits the rate of reaction->further enzymes cannot increase rate!
Enzyme Specificity	enzymes usually work on very specific substrates-> like a key->some are highly specific, others may not be so much: ie. will break particular chemical linkage wherever it occurs wheras others will only act on particular isomers.	(blank)
Substrate concentration	For a given amnt of enzyme the rate of an enzyme controlled reaction increases with increasing substrate concentration- up to a point.	->low concentration of substrates->not all active sites of Emolec r used, ie. occupied. , very high substrate concentration->all sites are being used->rate of reaction cannot increase more->graph tails off.
Enzymes - Temperature	has 2 main effects: 1. increase kenetice energy ->faster movement->more often substrate & enz. collide->greater rate of reaction., 2. atoms (which make up enzymes) vibrate->breaking up hydrogen bonds etc. ->shape of enz. is altered->active site no longer	fits substrate->enzyme is said to be denatured->loses its catalytic property//optimum temperatures of enz. varies between appr. 10-80 C-> most commonly areoung 40 C->denaturing usually occurs at appr. 60C.
Denaturing	i.e increase of temperature->. atoms (which make up enzymes) vibrate->breaking up hydrogen bonds etc. ->shape of enz. is altered->active site no longer fits substrate->enzyme is said to be denatured->loses its catalytic property	or change in pH->3-dimensional mol. shape is vital to functioning of enzymes->they are partly results of hydrogen bonding which may be broken by conc. of (H+)ions present and may lead to denaturing.
Definition pH	is a measure of hydrogen ion concentration (H+)->is usually measured on a scale of 1-14 with pH7 being neutral. pH less than 7 is acid, pH greater than 7 is alkaline	Each enzyme works best at a particular pH and deviations from this optimum may result in denaturation->Optimum pH various from enzyme to enzyme.
Hydrogen ions	(H+)	(blank)
Kinetic Energy	Energy due to the motion of an object ->be translation (motion along a path from one place to another), rotation about an axis, vibration, or any combination of motions.	The kinetic energy of an object depends on its mass and velocity
Inhibitors	rate of enzyme reactions may be decreased by their presence->there are 2 main types: 1. reversible inhibtors, 2. non-reversible inhibitors	(blank)
Reversible inhibitors	effect is temporary and cause no permanent damage to enzymes, bcs their association with enzymes is loos->can easily be removed.	2 types: competetive (active site-directed) and 2. non-competetive (non-active-site-directed)
Competetive inhibitors	Reversible inhibitors->active site-directed->compete with the substrate for active site of enzyme mol. ->their struct. combines with AS->therefore prevents substrates to occupy site->reduces rate of reaction	->the same quantity of product is formes (->as substrate continues to use any enzyme molecules that are unafected)->but it takes longer!, ie. MALONIC ACID which dompetes with succinate
Non-competetive inhibitors	Reversible Inhibitors->attach themselves not to the active site of the enzyme but elsewhere. ->they alter shape of E. that that the AS can no longer properly accomodate the substrate	->as substrate & inhibitors attach to different parts they do not compete for same site->increase in substrate cons. therefore doen's reduce effect of inhibitors.
Non-reversible inhibitors	leave enzyme permanently damaged->E. are therefore unable to carry out their catalytic function.->ie. heavy metal ions such as mercury (Hg2+) and silver (Ag+) casue sisulphide bonds to break (those bonds help to maintain the shape of E. mol.)->permanent	loss of catalytic properties.
Cofactor	is a non-protein substance which is essential for some enzymes to function efficiently	There are 3 types: 1. activators , 2. coenzymes, 3. prosthetic groups
Activators	are substances which are necessary for the functioning of certain enzymes.	it is possible that activators asist in froming the enzyme-substrate complex by moulding either the enzyme or substrate molecules into a more suitable shape.
Coenzymes	are non-protein organic substances which are essential to the efficient functioning of some enzymes, but are NOT themselves bound to enzymes. They are often derived from vitamines.	Need to know example?
Prosthetic groups	are organic molecules (like coenzymes), but they ARE bound to enzymes themselves.	example is haem.
Classification of enzymes	are classified into 6 groups according to the type of reaction they catalise: 1. Oxidoreductase, 2. Transferases, 3. Hydrolases, 4. Lyases, 5. Isomerases, 6. Ligases	(blank)
negative feedback	This occurs where the products of a process can act at an earlier stage in the process to inhibit their own formation.	Where the end product (E) of a pathway inhibits (the enzyme) at the start (A) ->ie. high concentration of E reduces its own production rate (A). they are usually reversible

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