Enzymes

Question 1

why are enzymes so remarkable

Answer 1

whereas chemical catalysts usually need high temperatures, increased pressures, and extremes of PH, enzymes speed up metabolic reactions by up to 10 to the power of 12 times at lower temperatures, often at neural Ph and normal pressures. Hence, as biological catalysts, they are able to function in conditions that sustain life. such as humans.

as well as this enzymes are more specific than chemical catalysts, they do not produce unwanted bi-products and rarely make mistakes. the cells in which they are produced can also regulate production to fit the needs of the organism or cell.

Question 2

how does enzyme structure determine their functioning?

Answer 2

as with all biological molecules, the structure of enzymes enables them to carry out their functions. for enzymes to catalyze some reactions, for example, they may require a cofactor. or as well as this the instructions for making enzymes are encoded in genes. if the gene has a mutation that alters the amino acid sequencing, it may alter the enzyme’s tertiary structure which may prevent it from functioning
and if an enzyme is prevented from functioning it could result in a metabolic disorder. enzymes catalyze the organism’s structural components such as collagen in bone, cartilage, blood vessel walls, joints, and connective tissue and if this production is prevented it could be harmful. it could cause something known as stone man syndrome.

Question 3

what is the active site of an enzyme

Answer 3

enzymes are large molecules with a specific area, an indentation or cleft on the surface of the molecule, known as the active site. this often consists of around 6-10 amino acids.
-the tertiary structure of the active site is critical, as its shape is complementary to a substrate molecule. so, each enzyme is highly specific in its function, as it can only catalyze a reaction involving the particular type of substrate molecule that fits into its active site. the shape of the enzyme active site, and hence its ability to catalyze a reaction, can be altered by changes in temperature and PH, as these affect the bonds that hold proteins in their tertiary structure

Question 4

describe how intracellular enzymes work

Answer 4

in any cell, and with its organelles, there may be up to 1000 metabolic reactions going on at once, each being catalyzed by a different enzyme. some of these reactions are part of a metabolic pathway. so therefore an intracellular enzyme is an enzyme that works within the mass reactions of inside cells.

Question 5

describe the processes that take place within a metabolic pathway

Answer 5

each metabolic pathway in a living cell is one of a series of consecutive reactions, every step catalysed by a specific enzyme that produces a specific product. and the various reactants and intermediates act as substrates for specific enzymes. we call these metabolites (reactants, intermediates, and products). at the end of a metabolic pathway, a final product will be produced that will be used either by the cell or by the body.

there are two types of metabolic pathways. One type is known as catabolic metabolic pathways- when molecules are broken down into smaller molecules and release energy
but in other metabolic reactions, known as anabolic metabolic pathways- energy is used to synthesize larger molecules from smaller ones.

Question 6

describe the properties and functions of the enzyme catalase

Answer 6

catalase is found nearly in all living organisms exposed to oxygen. it is a very important enzyme, as it protects cells from damage by reactive oxygen by quickly breaking down hydrogen peroxide. which is a potentially harmful product of many metabolic reactions, to water and oxygen

HYDROGEN PEROXIDE (harmful) + REACTIVE OXYGEN - WATER AND OXYGEN
- catalyze consists of four polypeptide chains and contains a haem group with iron
-it is the fasting-acting enzyme, having the highest turnover number of about 6 million a second.
-found in vesicles known as peroxisomes
-found within white blood cells.
-The optimum PH is around 7. and in humans, the optimum temperature for it is around 45 degrees.

Question 7

describe how extracellular enzymes work and give some examples

Answer 7

some enzymes are secreted from cells where they are made and act on their substrates extracellularly. Fungi such as the bread mould mucor, release hydrolytic enzymes from their thread-like hyphae. the enzymes digest carbohydrates, protein, and lipids in the bread, and the products are used in respiration and then growth.

in our digestive system, many enzymes are secreted, from cells lining the alimentary canal, into the gut lumen. they extracellularly digest large molecules such as proteins, lipids, and carbohydrates found within food.
for example
-amylase is produced in salivary gland cells and it is secreted to digest starch to maltose. it is also made in the pancreas and is released into the lumen of the small intestine
-trypsin is made in the pancreas and acts in the lumen of the small intestine to digest proteins into smaller peptides by hydrolysing peptide bonds. its optimum PH is around 7.5 and 8.5

Question 8

what is a turnover number

Answer 8

the number of substrate molecules transformed per minute by a single enzyme molecule when the enzyme is the rate-limiting factor.

Question 9

what is a cofactor

Answer 9

A cofactor is a non-protein chemical compound or metallic ion that is required for an enzyme’s role as a catalyst

Question 10

state the properties of the type of cofactor called a prosthetic group. and give an example of one

Answer 10

a prosthetic group is a cofactor that is permanently bound, by covalent bonds, to an enzyme molecule. the enzyme carbonic anhydrase contains a zinc ion permanently bound, as a prosthetic group, to its active site. this enzyme is found in erythrocytes (red blood cells) and catalyses the interconversion of carbon dioxide and water to carbonic acid, which then breaks down into protons and hydrogen carbonate ions. the reaction is vitally important, as it enables carbon dioxide to be carried in the blood from respiring tissues to the lungs.

Question 11

what other cofactors can be introduced and how do they work

Answer 11

during an enzyme catalyzed reaction, the enzyme and substrate molecules temporarily bind together to form an enzyme-substrate complex. the presence of certain ions that may temporarily bind to either the substrate or the enzyme molecule may ease the formation of complexes, and therefore increase the rate of enzyme-catalyzed reactions.
-some cofactors act as co-substrates- they and the substrates together form the correct shape to bind to the active site of the enzyme
-some cofactors also change their charge distribution on the surface of the substrate molecules or on the surface of the enzyme active site, and this makes temporary bonds in the enzyme-substrate complex easier to form.
for example. the enzyme amylase digests starch to maltose but it will only function if chloride ions are present.

Question 12

what is a coenzyme

Answer 12

coenzymes are small organic non-protein molecules that bind temporarily to the active site of enzyme molecules, either just before or at the same time as the substrate binds. the coenzymes are chemically changed during the reaction, and they need to be recycled to their original state sometimes by a different enzyme.

Question 13

what impact do vitamins have on coenzymes

Answer 13

many coenzymes are derived from water-soluble vitamins. if these vitamins are deficient in the diet of humans, then certain diseases may be a result.

Question 14

what co enzyme derives from vitamin B12 and what is the human deficiency disease if there is a short supply?

Answer 14

coblamin coenzymes

pernicious anemia

Question 15

what co enzyme derives from the vitamin Folic acid and what is the human deficiency disease if there is a short supply?

Answer 15

tetrahydrofolate

megablastic anemia

Question 16

what co enzyme derives from vitamin Nicotinamide and what is the human deficiency disease if there is a short supply?

Answer 16

NAD,NADP

pellagra

Question 17

what co enzyme derives from vitamin Pantothenate and what is the human deficiency disease if there is a short supply?

Answer 17

Coenzyme A

elevated blood plasma triglyceride levels

Question 18

what coenzyme derives from vitamin Thiamine and what is the human deficiency disease if there is a short supply?

Answer 18

thiamine pyrophosphate

beriberi

Question 19

what is the Lock and key hypothesis

Answer 19

the lock and key hypothesis is the hypothesis where the enzyme molecule and substrate molecule fit together like a lock and key because enzymes are highly specific to their substrate molecules and only one substrate works for one enzyme molecule just like how only one key works for one lock because they have a complementary shape just like enzymes.

Question 20

what is an enzyme product complex

Answer 20

an enzyme-product complex is when substrate molecules fit into the active site forming an enzyme-product complex, where the bond is reformed between the product of an enzyme-substrate complex to make a larger molecule. for example this occurs within anabolic reactions which requires energy to reform bonds.

Question 21

describe how substrate molecules and enzyme molecules come into contact and form an enzyme-substrate complex.

Answer 21

the substrate molecules and enzyme molecules each have kinetic energy and are constantly moving randomly. if a substrate molecule successfully collides with an enzyme molecule, the enzyme-substrate complex will form. the substrate molecules are either broken down or built up into a product molecule. it leaves the active site and then the enzyme molecule can complete its next reaction.

Question 22

what is the induced fit hypothesis

Answer 22

when the substrate molecules fit into the enzyme’s active site, the active site changes shape slightly to mold itself around the substrate molecule. the active site still has a shape complementary to the shape of the substrate molecule. but, on binding, the subtle changes in the shape of the R-groups of the amino acids that make up the active site give a more precise composition. an enzyme-substrate complex is formed and noncovalent forces such as hydrogen bonds, ionic attractions, and hydrophobic interactions bind the substrate molecule to the active site. when converted to products, the product stays in the active site and we refer to it as an enzyme-product complex. As the shape is now different the product detaches. the enzyme can now complete a new reaction.

Question 23

what do enzymes do to activation energy and how

Answer 23

chemical reactions need energy to activate or begin them. many chemicals can be heated to provide this activation energy and make them react together. this increases the kinetic energy of the molecules so they move about more and are more likely to collide successfully. in a living cell, the temperature cannot be raised too much, or proteins and lipids would denature. because enzymes have an active site specific to only the substrate molecules, they bring the molecules close enough together to react. without the need for excessive heat. Therefore they lower activation energy and speed up the rate of reaction.

Question 24

what happens if a mixture containing enzyme and substrate molecules is heated

Answer 24

-both types of molecule will gain kinetic energy and move faster
-this will increase rate of successful collisions
-therefore the rate of complexes formed increases, and the rate of reaction increases.
-at a particular temperature, called the enzyme’s optimum temperature, the rate of reaction is at its maximum. (any higher temperatures will often denature the enzyme)

Question 25

what effect does the vibrations created by kinetic energy do to enzymes

Answer 25

vibrations may break some of the weak bonds, such as hydrogen and ionic bonds that hold the proteins’ tertiary structure. as the active site begins to change and distort, the substrate molecules will no longer fit within the active site. so the rate of reaction will decrease. as more heat is applied, enzymes reach an irreversible state where we call them denatured and the reaction cannot proceed. (heat cannot break the peptide bonds holding polypeptide chains together)

Question 26

what do adaptations between species do to optimum temperatures of enzymes

Answer 26

some enzymes work best at cold temperatures. bear in mind that some organisms are adapted to living in cold environments s. for example, there are psychrophilic bacteria that live in very cold conditions. their enzymes work best at very low temperatures.
some organisms such as thermophilic bacteria alive in hot springs, that sit at extremely high temperatures. their enzymes are heat stable. they have more disulfide bonds that are harder to break making the susceptible to high temperatures.

Question 27

what is the temperature coefficient

Answer 27

the temperature coefficient refers to the increase in the rate of a process when the temperature is increased by 10 degrees. it is given an equation.

Q10 = rate of reaction at (T+10) degrees
divided by (over) the rate of reaction at T degrees.

Question 28

what is PH

Answer 28

the PH indicates whether a substance is acidic, alkaline or natural. PH values of 0-6 are acidic, PH values of 7 indicate neutral and PH 8-14 indicates that a solution is alkaline.

Question 29

what is a buffer within biology

Answer 29

in biology, a buffer is something that resists changes in PH. there are certain chemicals in your body that resist changes in PH so that blood PH remains within fairly narrow limits close to PH 7.4. these chemicals can donate or accept hydrogen ions. some proteins, such as hemoglobin, can also donate or accept protons and so act as buffers.

Question 30

how does Ph effect the tertiary structure of enzymes

Answer 30

a hydrogen ion which is a proton, has a positive charge so it will attract negatively charged ions, molecules, or parts of molecules. excess hydrogen ions will interfere with hydrogen bonds and ionic forces, and so the enzyme’s active site will change shape, if the substrate molecule doesn’t fit well then the rate of reaction will decrease. Increasing the concentration of hydrogen ions will also alter the charges on the active site or enzyme molecule, as protons will cluster around negatively charged groups. this will interfere with the binding between substrate and enzyme molecules.

Question 31

what Ph do enzymes often work at intracellularly

Answer 31

often close to PH 7

Question 32

what PH does amylase work best at within the mouth

Answer 32

around PH 6.8

Question 33

what PH should the stomach acid be so that pathogens can be killed and pepsin can break down proteins

Answer 33

between PH 1 and 2 ( PH is very low and acidic)

Question 34

what PH does trypsin work at and what does Bile do after food has been broken down in the stomach and it moves the small intestine

Answer 34

Bile neutralizes the stomach acid to bring PH to around 7.8 which is optimal for protein-digesting trypsin.

Question 35

describe the effect of changing substrate concentration on the rate of reaction in an enzyme catalysed reaction

Answer 35

if there is no substrate present, then an enzyme-catalysed reaction cannot proceed. this is because there are no substrate molecules to fit into the enzyme molecules’ active sites and no complexes are formed. as the substrate is added and its concentration increases, the rate of reaction increases. this is because more complexes can form and as a result more product is formed. substrate concentration at this point is the limiting factor, however, as concentration increased reaction will reach its maximum rate. increasing substrate concentration has no effect on the rate of reaction because all the enzymes’ active sites are occupied with substrate molecules. so now the enzyme concentration is the limiting factor.

Question 36

describe the effect of changing the enzyme concentration in an enzyme controlled reaction has on rate of reaction

Answer 36

as enzyme concentration increases more active sites on the enzyme become available and more successful collisions will occur. this means more E-S complexes can form per minute so the rate of reaction increases. the enzyme concentration is the limiting factor at this point. as it increases, so does the rate of reaction. however if substrate concentration is limited, all the substrate molecules will not be able to keep up with the enzymes and therefore wont fill all the active sites. this means maximum rate of reaction has been reached until substrate concentration increases. so therefore substrate concentration is now the limiting factor.

Question 37

what is enzyme degradation and what are the benefits of it

Answer 37

the protein component of living cells is constantly being turned over. cells are continuously degrading old enzyme molecules to their component amino acids and synthesizing new enzymes from the amino acids. this might appear wasteful however it has benefits
-the elimination of abnormally shaped proteins that may accumulate and damage cells
-the regulation of metabolism in the cell by eliminating any superfluous enzymes .

Question 38

what is an enzyme inhibitor

Answer 38

inhibitors are substances that reduce the activity of an enzyme. they do this by combing with the enzyme molecule in a way that influences how the substrate molecule binds to the enzyme or effects the enzyme’s turnover number. some may block the active site and some may change the active site shape. but both inhibit the formation of ES complexes and therefore product formation

Question 39

what is a competitive inhibitor and how does it prevent enzymes controlled reactions?

Answer 39

competitive inhibitors are substances whose molecules have a similar shape to an enzyme’s substrate molecule. the competitive inhibitor fits into the active site so that a substrate molecule cannot enter. the amount of inhibition depends on the relative concentration of substrate and inhibitor molecules. more inhibitor molecules means more inhibitors collide with active sites and so the effect on inhibition is greater. increasing substrate concentration effectively ‘dilutes’ the effect of the inhibitor. if enough substrate is added, the inhibitor is much less likely to collide with the enzyme. once in the enzyme, inhibitors remain unchanged as the normal substate would be. the result of the inhibitor is that it reduces rate of production of ES complexes depending on its concentration.

Question 40

what is it called if a competitive inhibitor binds irreversibly to the active site

Answer 40

inactivator

Question 41

what is a non competitive inhibitor and how does it prevent enzymes controlled reactions?

Answer 41

if the inhibitor molecule binds to somewhere other than the active site, it is called non-competitive inhibition. non-competitive inhibitors do not compete with substrate molecules for a place on the enzyme’s active site. they attach to the enzyme molecule in a region known as the allosteric site. in so doing they disrupt the enzyme’s tertiary structure and it changes shape. this distortion changes the shape of the active site so that it is no longer complementary to the substrate molecule, so no more ES complexes can formulate.
the maximum rate of reaction is reduced by the presence of non-competitive inhibitors. adding more substrate molecules might allow to reaction to attain this new, lower rate, but even very high concentrations of substrate will not allow the rate of reaction to return to its uninhibited maximum.
the more inhibitor molecules are present, the greater the degree of inhibition.

Question 42

what is an end product inhibition

Answer 42

one way in which enzyme-catalysed reactions may be regulated is by end-product inhibition. after the catalysed reaction has reached completion, product molecules may stay tightly bound to the enzyme. in this way, the enzyme cannot form more of the product than the cell needs. such regulation is an example of negative feedback.

Question 43

how can metabolic sequences be controlled

Answer 43

many metabolic processes, such as photosynthesis and respiration, involve a series of enzyme catalysed reactions. the product of one enzyme-catalyzed reaction becomes the substrate for the next enzyme-catalyzed reaction. this binding changes the shape of enzyme 1’s active sites shape, preventing the pathway from running. this is non-competitive inhibiton but its reversable.

Question 44

describe the metabolic poison that acts as an enzyme inhibitor: cyanide

Answer 44

potassium cyanide is highly toxic because it inhibits aerobic respiration. it also inhibits catalase.
-when ingested, cyanide is hydrolysed to produce hydrogen cyanide, a very toxic gas that can readily dissociate into H+ and CN- ions. the CN- ions bind irreversibly to an enzyme found in mitochondria and inhibit the final stage of aerobic respiration. because the final stage is inhibited, earlier stages cannot run and aerobic respiration stops.

Question 45

describe the metabolic poison that acts as an enzyme inhibitor: snake venom

Answer 45

the venom of the green mamba snake contains a chemical that inhibits the enzyme acetylcholinesterase. this enzyme is important at neuromuscular synapses to break down the neurotransmitter acetylcholine. if this is inhibited the enzyme stays attached to the receptors on the muscle membrane and the muscle keeps contracting. this causes paralysis. and if muscles involved in breathing are paralysed the victims will die from suffocation.

Question 46

describe the medical drug acting by enzyme inhibition: Aspirin

Answer 46

this drug has been used for over 3000 years, and marketed as aspirin since the late 19th century. in 1971, Professor John Vane and his team discovered salicylic acid binds to enzymes that catalyze the formation of prostaglandins. thus it prevents the formation of prostaglandins which are cell-signalling molecules produced by cells when tissues are infected or damaged. prostaglandins make nerve cells more sensitive to pain and increase swelling during inflammation. aspirin can also reduce the risk of blood clotting.

Question 47

describe the medical drug acting by enzyme inhibition: ATPase inhibitors

Answer 47

extracts from purple foxglove leaves have been used for centuries to treat heart failure and atrial arrhythmia. the chemicals are now identified as cardiac glycosides, also known as digoxin. they inhibit the sodium potassium pump in the cell membranes of heart muscle cells, and allow more calcium ions to enter the cells. calcium ions increase muscle contractions, this strengthen the heartbeat .

Question 48

describe the medical drug acting by enzyme inhibition: ACE inhibitors

Answer 48

these are medical drugs that inhibit the angiotensin-converting enzyme (ACE), which normally operates in a metabolic pathway that ultimately increases your blood pressure. they are used: - to lower blood pressure in patients with hypertension who cannot take beta-blockers. to treat heart failure- a low dose is given at first, and then a patient’s blood pressure is checked.
-to minimize risk of a second heart attack or a stroke in patients who have suffered a myocardial infarction.

Question 49

describe the medical drug acting by enzyme inhibition: protease inhibitors

Answer 49

protease inhibitors, such as amprenavir and ritonavir, are used to treat some viral infections. they prevent the replication of the virus particles within the host cells, by inhibiting protease enzymes so that the viral coats cannot be made. these inhibitors often inhibit viral protease enzymes by competitive inhibition.

Question 50

describe the medical drug acting by enzyme inhibition: nucleoside reverse transcriptase inhibitors

Answer 50

many of the antiviral drugs, such as zidovudine and abacavir, used to treat patients who are HIV positive are nucleoside reverse transcriptase inhibitors. they inhibit enzymes involved in making DNA using viral RNA as a template.