Enzymes

Question 1

What are enzymes

Answer 1

Globular proteins with a 3D shape so it will have a primary secondary and tertiary structure
They acts as biological catalysts for intra and extracellular reactions to determine structure n function. They affect metabolism of cells and whole organism
They have an active site which is complimentary to the shape of a specific substrate molecule

Question 2

Why are enzymes 3D

Answer 2

Due to the interactions between the R groups of amino acids that make up the protein (ionic,H,covalent,Hphobic n Hphilic)

Question 3

Why are enzymes so specific

Answer 3

They have an active site which is complimentary to the shape of a specific substrate molecule
This active site will have a specific sequence of amino acids causing it to have this specific shape. Changing the amino acid sequence and ape of active site likely to be changed

Question 5

How do enzymes work

Answer 5

For reaction to work reaction molecules must have enough energy to cross potential energy barrier(AE)
All molecules have some KE but only some have enough for a reaction to occur.
The lower the potential energy barrier, the more reactant molecules have sufficient energy and faster the reaction
All catalysts function by forming transition state with reactants, of lower free energy than would be found in the uncatalysed reactions.
And the formation of enzyme substrate complexes lowers AE of metabolic reactions

Question 6

What is metabolism
And what reactions are enzymes involved in

Answer 6

All chemical reactions inside a cell
Anabolic(building bigger molecules) and catabolic (breaking large molecules down)

Question 7

Give eg of an exhume that catalyses intracellular reactions

Answer 7

Catalase:catalysed decomposition of hydrogen peroxide into H20 and O2

Question 8

2 enzymes that catalyse extracellular reactions

Answer 8

Amylase:carbohydrate catalyses digestion of starch to maltose in saliva
Trypsin: pancreatic endopeptidase catalyses hydrolysis of peptide bonds in small intestine lumen

Question 9

What do single celled organisms and fungi rely on to digest their food

Answer 9

Extracellular enzymes

Question 10

Explain the induced fit model of enzyme action

Answer 10

Helps explain why enzymes are so specific and only bond to one specific substrate. The shape of the active site is not directly complimentary to the substrate and it’s flexible.so active site slightly changes shape to better fit a substrate molecule once it binds.
Conformational change (changes in 3D struct of enz when it binds toS)enables
ES complexes to form when substrate adsorbs
This puts strain on substrate bonds lowering the activation energy. Bonds in the EPC weaken and product desorbs

Question 11

What’s the lock and key model theory

Answer 11

This is where the substrate fits into the enzyme in the same way a key fits into a lock-active site and substrate have a complimentary shape.
Active site has a rigid shape determined by the tertiary structure so it’s only complimentary to one substrate. Formation of the ES lowers activation energy

Question 12

Limitation of the lock and key model

Answer 12

New evidence has shown enzyme substrate complex changed shape slightly to complete the fit and licking substrate even more tightly to enzyme
Unlike the lock and key model, the induced fit model emphasizes that the enzyme is not completely rigid, but can adjust its shape to better accommodate the substrate.

Question 13

why does enzyme substrate lower activation energy

Answer 13

When bringing substrates tg it bends substrate molecules and bring em close tg in a way that facilitates bond-breaking, helping to reach the transition state. Reducing the repulsion between em
If enzymes catalysing a breakdown reaction fitting into active site the enzyme can induce strain on certain bonds within the substrate molecule, making them more susceptible to breaking and facilitating the reaction.

Question 14

Factors affecting enzyme activity

Answer 14

Temp
Ph
Enzyme concentration
Substrate concentration
Limiting factors

Question 15

How does temp affect enzyme activity

Answer 15

Upto the optimum temp, enzymes and substrates gain more KE so they move around more and faster
Greater chance of more successful collisions between enzymes active site and substrate molecules so higher ROR

Question 16

What’s optimum and what happens to enzymes when they pass the optimum

Answer 16

Temperature at which rate of an enzyme controlled reaction is at its fastest.
When it’s above optimum, temperature increases, the extra KE begins to break bonds in tertiary structure of the enzyme.(H first)
Causes enzyme to change shape and active site changing shape so yes denatured. Active site no longer has complimentary shape to substrate so no esc formed and ror decreases.

Question 17

What’s the temperature coefficient

Answer 17

Q10-R2(rate at higher temp)/R1(rate at lower temp

Question 18

If a graph had a q10 value of 2 what would it mean and if it’s three too

Answer 18

Rate doubles when temp raises by 10
If it’s three it would treble

Question 19

How does ph affect enzyme activity

Answer 19

All enzymes have different PHs. As environmental Ph moves away from optimum. The changing ratio of H+ and OH- interferes with hydrogen and ionic bonds that hold the enzymes tertiary structure in place . This resulting in active site changing shape so desaturation and it’s no longer complimentary to substrate so escs aren’t formed and rate of reaction decreases

Question 20

How does enzyme concentration affect
Enzyme activity

Answer 20

The more enzyme molecule there are in a solution the more likely a substrate molecule is to collide with one as more active sites are available and form an enzyme substrate complex. So it inc ROR.

Question 21

What happens when enzyme concentrations plateaus off

Answer 21

Enzyme conc isn’t a limiting factor anymore Substrate amount is.There are active sites which are empty so rates cannnot increase any further.

Question 22

Effect of substrate concentrations

Answer 22

The higher the substrate conc higher ROR. More substrate molecules increase collisions between substrates and enzymes so more active sites occupied and more enzyme substrate complexes formed.enzymes in excess atp and substrates acting limiting factor.
Sub conc dec over time so if no variable changed ROR dec too so initial ROR is highest ROR

Question 23

What happens when substrate concentration plateaus off

Answer 23

All active sites are occupied no further increase in rate possible and it stays constant.sub conc no longer limiting factor.Another factors limiting like EC. Not enligh enzymes to act on inc no of substrate molecules as AS are all saturated.(vmax)

Question 24

If we doubled the enzyme concentration what would happen

Answer 24

The maximum rate doubles (vmax) assuming there is sufficient substrate available

Question 25

What’s vmax

Answer 25

Rate of reaction when enzyme is saturated with substrate - it’s the max ROR. Relationship between ROR and conc of substrate depends on affinity of enzyme for its substrate. Vmax reveals the number of substrate molecules being catalases per second

Question 26

What are cofactors

Answer 26

Non protein facilitator molecules -increase rate of reaction by enabling enzyme activity

Question 29

What are inorganic cofactors

Answer 29

Some cofactors could be inorganic molecules/iobs. They work by helping substrate and enzyme to bind tg. They don’t directly participate in reaction so aren’t used up in any way.Eg Cl2 For amylase

Question 30

What are the organic cofactors

Answer 30

Co enzymes-participate in the reaction and are changed by it.Theyre just like a second substrate. They act as carriers moving chemical groups between different enzymes. Theyre continually recycled during. Eh vitamins are usually sources of coenzymes NAD from VB3 Prosthetic groups-non protein, tightly n permanently bound groups to enzymes which enables escs to form-bit directly involved in reaction . it will become a conjugate protein after.eg Zn2+- in carbonic anhydrase which breaks down co2 in rbc

Question 31

Why do we need small quantities of vitamins in our diets

Answer 31

For a healthy metabolism so they can help release energy from food

Question 32

What are enzyme inhibitors

Answer 32

Molecules that bind to enzymes and prevent enzyme action so can’t catalyse reactions.

Question 34

What are the different inhibitors

Answer 34

Competitive inhibitors-have a similar shape to substrate molecules competing with them to bind to the active site but no reactions takes place. Instead they block active site so no substrate molecules can fit in it How much it’s stopped by depends on conc of inhibitor and substrate.Jf theres high conc of inhibitor it w take up nearly all active sites n hardly any of substrate w get to enzyme . Higher conc of substrate then substrates chances of getting to active site before inhibitor increases.So increasing concentration of substrate will increase ROR

Question 35

What do non competitive inhibitors do

Answer 35

Bind to the enzyme away from its active site.Theyre site they bind to the enzymes allosteric site. Causing changes in tertiary structure= active site to change shape so substrate molecules can no longer bind to it. They don’t compete w substrate molecules to bind to active site cuz they’re a diff shape.Inc concentration of substrate won’t many a difference-enzyme activity still inhibited

Question 36

What happens when more substrate molecules are added with a competitive inhibitor and a non competitive inhibitor

Answer 36

W competitive: same number of enzymes but when you add more substrates they outnumber the competitives so higher ROR reached. Effect of competitive inhibitor reached. Non competitive : when adding more substrates, there are fewer active enzymes available n rate limited So effect is not overcome

Question 37

What are hyperthermophiles And pyschrophiles

Answer 37

Hyperthermophiles have opt temp above 75c so grow at highest temp.Due to several adaptations that give proteins ability to retain structure and function in term of extreme temperatures.(more dialogue bonds,hydrophobic residues or ionic interactions Pyschrophiles are capable of growth and reproductions in cold temperatures -20 to +10.less ke in cold condition for successful collisions and proteins lose flexibility .adaptations in proteins allow em to move n change shape at low temp w a flexible structure Both require subtle changes in amino acid composition to stay functional in extreme conditions (changes in charge and hydrophobicity)

Question 38

How can you measure the rate of reaction using hydrogen peroxide and catalase

Answer 38

Measure volume of gas produced in a given time 1)set up boiling tubes w same vol n conc of hydrogen peroxide,to keep ph constant add equal vol of buffer solution to each 2)set up trough of water and fill measuring cylinder w water n tip it upside down and put deliver tube in hole of cylinder 3) put each boiling tube in a water bath set to a different temperature (10,20,30,40) along w about tube w catalase. Wait 5 mins before moving to next step so enzyme gets upto temp 4) use pipe eye to add sane vol n conc of catalase to each BT. Attach bung quickly. 5) record how much o2 produced in the first minute of reaction using a stopwatch 6) repeat exp three times and find mean volume of O2 produced 7)calculate mean rate of reaction at each temperature by volf of oxygen produced / time taken.units cm3s-1

Question 39

Weird equation for action of catalase

Answer 39

Hydrogen peroxide-oxygen and water

Question 40

Controlled variants for this catalase reaction

Answer 40

Enzyme vol n conc Substrate vol n conc Ph

Question 41

Hazards n safety for catalase

Answer 41

HP is irritant. Wear goggles n avoid skin Take care in handling hot water baths n wash hands after dealing w source of catalase

Question 42

Gore to find the effect of enzyme concentration on ROR using amylase

Answer 42

1) put drops of iodine into each well of spitting tile 2) make a serial solution of amylase to make several concentrations 3)add same vol n conc of starch to first booing tube at same time n start timer 4) use dropping pure to put drop of mixture into one of the wells containing iodine solution at regular intervals 5) time how long it takes for colour to turn blue black 6) repeat 2 more times and calculate mean time taken 7) repeat experiment for each amylase conc

Question 43

Controlled variables for amylase practical

Answer 43

Temperate Ph Enzyme vol Substrate conc n vol

Question 44

How to do a dilution for catalase w a dilution factor of two so it halves

Answer 44

Start with 2% catalase solution and add 4cm3 to first boiling tube Using syringe add 2cm3 of solution in first tube to next tube making it 1% catalase solution Repeat to make 0.50,0.25,0.13

Question 45

What is a stem cell

Answer 45

Undifferentiated cells that can divide indefinitely and turn into other specific cell types. All multicellular organism have some form of stem cell

Question 46

What’s the four types of stem cell

Answer 46

Totipotent-can develop into any cell type including placenta umbilical cord dev fetus and embryo and their formed shortly after fertilisation of egg so versatile af. After 4 days they specialise slightly into PP Pluripotent-can develop into any cell type w out placenta n embryo. Not as versatile as T Eg embryonic stem cells and induced pluripotent stem cells(lab)are PP cells Multipotent- can only develop into few different types of cell. Cells of. Certain class n category Unipoyent- can only develop into one type of cell

Question 48

characteristics of a stem cell

Answer 48

1)self renew(mitosis) 2)differentiate into a specialised cell type

Question 49

Where are stem cells from embryonic cells derived from

Answer 49

Zygotes which turn into blastocyts which then turn into embryos

Question 50

Why is there high demand for stem cells when it comes to RBC

Answer 50

We need to make a lot of em often as they only last 120 days

Question 51

What’s differentiation

Answer 51

Stem cells divide to become new cells which become specialised this is differentiation. Eg in animals adult stem cells are used to replace damaged cells. Adult stem cells divide n differentiate into bone barrow to replace worn out blood cells (erythrocytes n neutrophils)

Question 52

How does stem cells differ between kids n humans

Answer 52

Stem cells are found in early embryos and in the first few days of an embryos life any of its cells can develop into a type of human cell. In adults stem cells are only found in few places like bone marrow but they’re not as flexible as they can only clop into a limited range of cells Embryonic stem cells can divide indefinitely whilst adult can’t so getting adult ones r harder Adult cells alr specialised so potential to repair damaged tissue is very limited

Question 53

Where are stem cells found in plants

Answer 53

Meristems of plants (where growth takes place most) in the roots n stem stemcells of vascular cambium divide and differentiate to become xylem vessels n phloem sieve tubes

Question 54

What type of stem cells is a meristematic one

Answer 54

Totipotent that develops into various types of plant cell

Question 55

Uses of stem cells in medicine

Answer 55

They could treat neurological diseases like Alzheimer’s-brain cells are destroyed as a reult of the build up of abnormal proteins : drugs only alleviate these symptoms n they’re tryna regrow healthy nerve cells. Parkinson’s- ppls suffer from tremor that they can’t control.loads to loss of a. Type of nerve cell in brain that releases dopamine for control movement . Transplanted stem cells may help degenerate the dopamine producing cells Treat heart disease- muscle tissue is damaged as a result of heart attack body can’t replace these cells so ppl tryna use stem cells to make replacement heart cells

Question 56

How does ppl t1 diabetes use stem cells

Answer 56

Ppl w insulin dependent diabetes they’re body destroys the cells that produce this insulin from pancreas , so stem cells to replicate this insulin is used n injected

Question 57

What else are stem cells used for

Answer 57

Drug trials-new drugs can be tested in cultures of stem cells before animals n humans Researching developmental biology-study of changes that occur as multicellular organism grow n develop from a single cell as a fertilised egg.Dtem cells are umpirtant for this ad they divide indefinitely and differentiate into any cell within an organism.

Question 58

What are embryonic stem cells

Answer 58

Inside a blastocyst cells can be cultured into an embryonic stem cell. They’re undifferentiated but they have unique ability to divide indefinitely into almost any type of cell in body

Question 59

Limits of ES cells n why animal cells are better

Answer 59

There aren’t enough of them from ivf n Donors as there’s a huge demand. So we need to use animal cells but this can cause uproar saying chimeras are created they’re not used for transplants in humans as it can cause diseases but they’re sooo useful for research and animal ones you could get so many of them

Question 60

What are embryonic stem cells used for

Answer 60

Cloned to form any type of tissue in body. Including specific tissues for transplants with no rejection from immune system Can study disease. Cells cloned from someone w a disease will carry faulty genes that cause it and scientists can study this n try out new drugs on cell Allows us to study earliest stages of human development so we can prevent birth defects miscarriages etc

Question 61

Ethics towards es cells

Answer 61

Removal of embryonic stem cells results in destruction of the embryos Many ppl believe life begins at conception and destruction of embryos is murder bsc. Lack of consensus to when embryo has rights This argument stops treatment of many incurable diseases. Umbilical cord stem cells may help treatment can overcome the problem but they only multipotent not pluripotent limiting use. Adult can be used to but can’t divide as much and can have mutations.

Question 62

What are induced pluripotent cells What’s gene therapy Ce therapy Cell reprogramming

Answer 62

Cells that can be reprogrammed from skin or blood cells to become any type of cell in body Technique to test n prevent disease by correcting mutation Cell therapy-treatment that uses stem cells to repair damaged cells in body Process of having identity of cell and returning it to a more primitive state of gene expression .

Question 63

Evaluate between human stem cells n plants stem cells

Answer 63

They both have specific regions where stem cells are found so bone marrow and skin and meristems for plants at roots n shoots Both undergo process of mitosis n differentiation Neither have totipotent stem cells and they have been specialised slightly so they can be one type of cell Animals are multi potent and meristems are Pluripotent Plant stem cells facilitate growth of cell animal helps replace cell Meristematic becomes transport vessels however bone marrow stem cells continue towards the blood cells which are transported

Question 66

How are metabolic poisons enzyme inhibitors enzyme inhibitors

Answer 66

Metabolic poisons-cyanide is a non competitive irreversible INH of an enzyme(cytochrome c oxidase.) that catalyses respiration reactions.cells that can’t respire die Ethylene glycol- metabolises ethanol dehyrogenase to oxalic acid as ethylene glycol is similar in shape to ethanol which acts a competitive inhibitor of above reactions . Mixing large amounts of ethanol w ethylene glycol slow ROR

Question 67

How do medicinal drugs act as inhibitors

Answer 67

Antibiotics like penicillin inhibits transpeptase which catalyse formation of protein in bacterial cell walls. It weakens cell walls as its structurally similar to one of substrates used in wall building and as P is different from substrate it prevents bacterium from regulating its osmotic pressure.cell bursts and bacterium killed Antiviral drugs can -eg reverse transcriptase INH which treat HIV as they inhibit enzyme reverse transcriptase which catalyses replication of viral dna preventing virus from replicating.

Question 68

What is a metabolic pathway and what ar they regulated by

Answer 68

A series of connected metabolic reactions Product of first reaction is used in second etc and each reactions catalysed by diff enzyme but many enezume are inhibited by product they catalyse which is product inhibition

Question 69

Function of end product inhibition again and give an example

Answer 69

Regulated metabolic pathways and controls amount of end product that’s made Phosphofrucyokinase involved in metabolic pathway that breaks down glucose to make atp. ATP inhibits Mr p over here so high level of atp prevents more atp being made

Question 70

How are enzymes synthesized to be inactive precursor molecules

Answer 70

Enzymes can initially be produced in an inactive form. . These inactive forms are “precursors“. They kept inactive by a reversible inhibitor component, which gets removed in a chem reaction in the right environment, to allow the enzyme to become active.This is good as it prevents enzyme from damaging cells

Question 71

What are the different inhibitors enzyme could be

Answer 71

Drugs Metabolic poison Control mechanism in end product inhibition Inactive precursor molecules

Question 72

2 examples of enzymes that catalyse extracellular reactions

Answer 72

Trupsin :pancreatic endopeptidase catalyses hydrolysis of appetite bonds in small intestine lumen Amylase carbohydrate catalyses digestion of starch to maltose in saliva /small intestine lumen

Question 73

How does end product inhibition work

Answer 73

The final product of a metabolic pathway binds to an allosteric site on the first enzyme in the pathway. This binding inhibits the enzyme's activity, shutting down the pathway. When the concentration of the end product decreases, the inhibition of the enzyme is reduced. The metabolic pathway can then proceed again.leading to more products/escs being produced once more.

Question 74

how does reversible and non reversible inhibition work

Answer 74

Some inhibitors bind reversibly to enzymes (i.e. their inhibiting effect on the enzyme can be reversed) while others bind irreversibly. Reversible inhibitors= form weak bonds w enzymes. Reversible inhibitors typically form hydrogen or ionic bonds w their enzymes which are weak and can easily be broken. Irreversible inhibitors form strong bonds w the enzymes. Irreversible inhibitors typically form covalent bonds with their enzymes which are much stronger and cannot be easily broken