3.1.4.2 many proteins are enzymes

Question 1

what is the definition of :
metabolism

Answer 1

All of the enzyme controlled reactions (anabolic and catabolic) that take place in an organism

Question 2

what is the definition of :
Anabolic reaction

Answer 2

One that build up molecules

Question 3

what is the definition of :
Catabolic reaction

Answer 3

One that breaks down molecules

Question 4

what is the definition of :
Catalyst:

Answer 4

A substance that modifies and increases the rate of reaction without being used up or changed

Question 5

what is the definition of :
Activation energy:

Answer 5

The energy required to start a reaction - to break existing bonds so new ones can be formed

Question 6

what is the definition of :
Enzyme

Answer 6

A biological catalyst that controls metabolism. Highly specific. Cannot make reactions happen that would not otherwise occur. Cannot change the amount of product. Can be re used

Question 7

what is the definition of :
Substrate:

Answer 7

The reactant(s) that fit into the active site of the enzyme

Question 8

what is the definition of :
Active site:

Answer 8

The region of the enzyme (a group of amino acids) into which the substrate fits and binds

Question 9

what is the definition of :
Intra/extra cellular:

Answer 9

Enzymes can act inside or outside of cells

Question 10

what is the definition of :
Metabolic pathway:

Answer 10

A Sequence of enzyme controlled reactions

Question 11

what is the definition of :
Denatured

Answer 11

The point at which an enzyme no longer functions
as a catalyst

Question 12

how are enzyme substrate complexes held together

Answer 12

Enzyme substrate complex held together by weak non covalent interactions (H, ionic, hydrophobic).

Question 13

waht are the three conditions for a chemical reaction to take place

Answer 13

1. The reactant molecules must collide with sufficient energy to alter the arrangement of their atoms to form products.

2.The energy of the products must be lower than that of the reactants

3.Activation energy must be supplied, often in the form of heat.

Question 14

how do enzymes lower activation energy

Answer 14

By putting stress on the bonds within a molecule

Or by holding molecules closer together
.
This increases the chances of a reaction, and so lowers the energy required to begin it.

Alternatively the enzyme can make the local conditions inside the active site quite different from those outside (pH, water concentration, charge for example) so that the reaction is more likely to happen.

Question 15

what are the two main assumed moddels for enzymes

Answer 15

the lock and key moddel

The Induced-fit hypothesis

Question 16

describe what the lock and key model hypothesesis

Answer 16

Lock-and-key hypothesis assumes the active site of an enzyme is rigid in its shape

Question 17

describe what The Induced-fit hypothesis

Answer 17

The Induced-fit hypothesis suggests the active site is flexible and only assumes its catalytic conformation after the substrate molecules bind to the site. In other words the enzyme has a certain general shape that alters slightly to accommodate the substrate placing strain on the substrate molecule.

The induced fit model helps to explain why enzymes are so specific and only bond to one particular substrate. The substrate doesn’t only have to fit the active site, it has to make the active site change in the right way as well.

Question 18

what factors effect enzyme activity

Answer 18

Temperature
pH
Substrate Concentration
Enzyme Concentration

Question 19

how does tempreature effect enzymes

Answer 19

Generally the rate doubles for each 10 degrees C rise until the optimum is reached, usually 40 degrees C in humans.

Low temps can inactivate the enzymes due to zero KE of molecules (reversible)

But most are denatured between 50 and 70 degrees C (irreversible)

Exposure time is important

Question 20

how does pH effect enzymes

Answer 20

Extremes of pH denature enzymes by breaking ionic bonds and hydrogen bonds that stabilise tertiary structure (non reversible)

Less extreme changes can inactivate enzyme (reversible)

pH fluctuations inside organisms are usually small, this means that they are far more likely to reduce an enzyme’s activity than to denature it.

Question 21

why do bonds break and how does the active site change

Answer 21

The arrangement of the active site is partly determined by the hydrogen and ionic bonds between -NH2 and -COOH groups that make up the enzyme. The change in H+ ions affects this bonding, causing the active site to change shape.

At low pH (<7) the NH3+ group will not be affected but the COO- will pick up a H ion. Ionic bonds can no longer form between enzyme and substrate.

pH > 7, there are insufficient H ions so that
NH2 cannot become NH3+

Question 22

why is it essential to use buffers in experiments involving proteins

Answer 22

In enzyme experiments it is essential to use buffers and controls.]

Buffers maintain a constant pH. If acid is added, the buffer ‘soaks up’ the hydrogen ions.

Controls are duplicate experiments, identical in every aspect to the experiment, except that the enzyme is boiled and cooled to denature it and thus cannot affect the DV.

Question 23

what are competative and non-competative inhibitors

Answer 23

Competitive inhibitors that bind to the active site of the enzyme., they compeate with subtrates for the active site

Non competitive inhibitors that bind to the enzyme at a position other than the active site (alloteric site) they change the shape of the active site , preventing the subtrate from binding

Question 24

competitive inhibitor vs non-competative inhibitor :
shape of molecule

Answer 24

comp :
similar to substrate

non-comp
different to substrate

Question 25

competitive inhibitor vs non-competative inhibitor :
site on enzyme

Answer 25

comp
active site

non-comp
allosteric site

Question 26

competitive inhibitor vs non-competative inhibitor :
effect of increasing inhibitor conc.

Answer 26

comp
may outcompete substrate and lower rate of reaction

non-comp
decreases the reaction as more enzyme molecules are made inactive

Question 27

competitive inhibitor vs non-competative inhibitor :
effect of increasing substrate conc.

Answer 27

comp
may out compete the competitive inhibitor and the rate can increase

non-comp
no effect on rate as the active site will have been changed by non competitive Inhibitor

Question 28

what are metabolic pathways

Answer 28

A metabolic pathway is a series of reactions in which each step is catalysed by an enzyme. Cells have evolved to use the products of their own reactions for feedback inhibition of enzyme activity. Feedback inhibition involves the use of a reaction product to regulate its own further production

Question 29

info card (summarise after reading this info)

Answer 29

Pharmaceutical Drugs:

Understanding how enzymes work and how they can be regulated is a key principle behind the development of many of the pharmaceutical drugs.

Statins are a group of medicines used to control blood cholesterol.

The end product of a metabolic pathway known as the mevalonate pathway, produces cholesterol.

How do statins work to reduce cholesterol?