ENZYMES

Question 1

What is an enzyme?

Answer 1

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

Question 2

What are enzymes?

Answer 2

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

Question 3

What are monomeric enzymes ?

Answer 3

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

Question 4

What are oligomers ?

Answer 4

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

Question 5

What is an active site?

Answer 5

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

Question 6

Define substrate

Answer 6

is any compound which an enzyme acts on. input to enzyme catalysed reaction

Question 7

Define product

Answer 7

is the output of enzyme catalysed reactions

Question 8

What bonds are the enzyme and substrate held together by

Answer 8

weak hydrogen bonds

Question 9

How is the specificity of enzymes demonstrated ?

Answer 9

• absolute or substrate specify
• bond specific
• group specificity

Question 10

Define absolute or substrate specificity

Answer 10

an enzyme can only act on one substrate only e.g. lactase can only hydrolyses fat sugar lactose

Question 11

Define bond specificity

Answer 11

an enzyme can only act on one type of chemical bond

Question 12

Define group specificity

Answer 12

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

Question 13

When and where does enzyme reactions occur?

Answer 13

Mosts enzymes act on substrates in solutions within cella of particular human tissues, therefore most enzymes are intercellular

Question 14

Define proenzymes

Answer 14

Is the state in which enzymes exist inactively in cells. These are enzymes that are only activate sin response to relevant signals

Question 15

What do proenzymes help achieve?

Answer 15

prevents enzyme activity occurring at inappropriate times or places causing damage

Question 16

What are the two theories related to enzyme specificity

Answer 16

• Lock and Key

- Induced fit model

Question 17

What are the key ideas of the lock and key model

Answer 17

• 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

Question 18

What are the key ideas of the induced fit model

Answer 18

• 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

Question 19

Define metabolism

Answer 19

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

Question 20

What are the two ain aspects of metabolism

Answer 20

catabolism and anabolism

Question 21

Describe anabolism

Answer 21

Is a series to cellular reactions in which complex molecules required by cells are synthesised from smaller building blocs-> requires energy

Question 22

Describe catabolism

Answer 22

Is a series of cellular reactions that release useful energy from the breakdown of complex molecules

Question 23

Define exergonic

Answer 23

metabolic reactions which release energy

Question 24

Define endogenic

Answer 24

metabolic reactions which require energy

Question 25

Define activation energy

Answer 25

is the minimum amount of energy required to initiate a reaction

Question 26

What is the relationship between enzymes and activation energy ?

Answer 26

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

Question 27

What does the enzyme substrate complex dictate?

Answer 27

• the substrate it will bind to
• the reaction it will catalyse
• products that will be made

Question 28

What are the main factors which effect enzyme activity ?

Answer 28

• Temp
• Enzyme concentration
• pH
• Substrate concentration

Question 29

What happens to enzyme activity as temperature increases to 37 degrees?humans

Answer 29

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.

Question 30

What begins to happen as the temp increases over optimum temp ?

Answer 30

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

Question 31

what happens to enzyme activity when temp decreases to below optimum level?

Answer 31

Rate of reaction decreases as the enzyme and substrate molecules do not have sufficient energy to interact

Question 32

What is pH?

Answer 32

concentration of hydrogen ions per litre of solution

Question 33

How does a change in pH levels from optimum level effect enzyme reaction ?

Answer 33

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

Question 34

What is the effect of substrate concentration on enzyme activity ?

Answer 34

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

Question 35

What is the effect of enzyme concentration on enzyme activity ?

Answer 35

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

Question 36

Define enzyme inhibiotor

Answer 36

is a molecule that binds to an enzyme, reducing activity by interfering with the enzyme in some way

Question 37

What is irreversible inhibition ?

Answer 37

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

Question 38

What is reversible inhibition?

Answer 38

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

Question 39

Define competitive inhibition

Answer 39

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

Question 40

Define non-competitive inhibitors

Answer 40

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

Question 41

What are cofactors ?

Answer 41

Additional non protein groups that are needed for enzymes to function properly. important to contributing to stabilising and activity

Question 42

What are inorganic cofactors ?

Answer 42

metal ions such as Fe^2+ or Mg^2+

Question 43

What are organic cofactors ?

Answer 43

prosthetic= tightly bound heme group groups and coenzymes , NAD, NADP, ATP