2.4-enzymes :) Flashcards
what do catalysts do?
speed up chemical reactions by lowering activation energy and remain unchanged at the end of the reaction.
what is the turnover number?
the no of reactions an enzyme molecule can catalyse per second
how are enzymes different to chemical catalysts?
1) whereas chemical catalysts usually need very high temperatures, pressures and ph, enzymes speed up metabolic reactions at often lower temperatures, neutral pH, and normal pressures
2) more specific than chemical catalyst; don’t produce unwanted by products and rarely make mistakes. cells can also regulate their activity to fit needs at the time.
how does a metabolic disorder happen?
if an enzyme that catalyses a metabolic reaction is deficient.
what is a metabolite?
the reactants, intermediates, and products of a metabolic pathway
what happens in a catabolic pathway?
metabolites are broken down to smaller molecules and release energy
what happens in an anabolic pathway?
energy is used to synthesise larger molecules from smaller ones.
what is a metabolic pathway?
a series of consecutive reactions, every step catalysed by a specific enzyme that forms a specific product.
why is catalase important?
protects cells from damage by reactive oxygen, by quickly breaking down h2o2 (hydrogen peroxide), a potentially harmful by-product of many metabolic reactions, to oxygen and water.
what is the structure of catalase?
4 polypeptide chains and contains a haem group with iron.
where is catalase found in eukaryotic cells?
inside small vesicles called peroxiomes
what is a use of catalase in white blood cells?
when they ingest pathogens they use catalase to help kill the invading microbe.
where is amylase produced and where does it act?
produced in: salivary glands and pancreas
acts in: mouth and small intestine
what does amylase do?
digests the polysaccharide starch to the dissaccharide maltose.
where is trypsin produced and where does it act?
made in pancreas and acts in lumen of small intestine.
what does trypsin do?
digests proteins into smaller peptides by hydrolysing peptide bonds.
what is a cofactor?
a substance that has to be present to ensure that an enzyme catalysed reaction takes place at an appropriate rate.
what is a prosthetic group?
a cofactor that is bound by covalent bonds to an enzyme molecule.
what prosthetic group does carbonic anhydrase contain?
a zinc ion
where is carbonic anhydrase found?
enthrocytes (red blood cells)
what does carbonic anhydrase do?
catalyses interconversion of CO2 and H2O to carbonic acid, which then breaks down to protons and hydrogencarbonate ions.
what is the equation for what carbonic anhydrase does?
CO2 + H20 H2CO3H+ +HCO3-
why is carbonic anhydrase important?
enables CO2 to be carried in the blood from respiring tissues to the lungs.
what is the cofactor of amylase?
chloride ions
what are co-substrates?
cofactors that, along with the substrate, form the correct shape to bind to the active site of the enzyme.
what are coenzymes?
small organic non-protein molecules that bind temporarily to the active site of enzyme molecules, either just before or at the same time that the substrate binds. the conezymes are chemically changed during the reaction, and they need to be recycled to their original state.
how can cofactors work?
1) prosthetic groups
2) co-substrates
3) by changing the charge distribution on the surface of the substrate molecule or on the surface of the enzyme’s active site, and making the temporary bonds in the enzyme-substrate complex easier to form.
4) coenzymes
what are 2 examples of coenzymes?
NAD and NADP- both hydrogen acceptors and derivatives of nucleotides.
how do enzymes lower the activation energy?
have an active site specifically to only the substrate molecules, so they bring the substrate molecules close enough to react without excessive heat.
what is the temperature coefficient?
the increase in the rate of a process when the temperature is increased by 10 degrees C.
what is Q10?
the temperature coefficient
name 2 organic acids
lactic acid
pyruvic acid
what is a buffer?
something that resists changes in pH.
how does pH affect bonds within molecules?
excess hydrogen ions interfere with h-bonds and ionic forces, so active site changes shape. it also alters charges on active site because more protons cluster around negatively charged groups, interfering with bonding of substrate.
how does pH affect rate of enzyme controlled reactions?
- small changes of pH, either side of the optimum, slow the rate of reaction but if normal pH is restored the h-bonds can reform and the active site’s shape is restored.
- at extremes of pH, the enzyme’s active site may be permanently denatured.
why do cells constantly degrade old enzyme molecules and synthesise new ones?
- eliminates abnormally shaped proteins that might accumulate+harm the cell
- regulates metabolism in cell by eliminating extra-surplus to requirements- enzymes.
what is an inactivator?
a competitive inhibitor which binds irreversibly to the enzyme’s active site.
what is a competitive inhibitor?
inhibitor whose molecules have a similar shape to an enzyme’s substrate molecules-fits in the active site so a substrate molecule can’t enter.
what do competitive inhibitors do?
compete with substrates directly for a position on the active site, forming enzyme-inhibitor complexes that are catalytically inactive-the inhibitor isn’t changed by the enzyme.
are competitive inhibitors reversible?
mostly
what are non competitive inhibitors?
inhibitor which does not compete with substrate for active site but binds to another place on the enzyme-the allosteric site.
how do non competitive inhibitors work?
by binding to the allosteric site, they change the tertiary structure of the enzyme. this distortion changes the shape of the active site so it’s no longer complimentary to the substrate, so ES complexes can’t form.
are non competitive inhibitors reversible?
can be irreversible or reversible
what is end product inhibition?
after enzyme catalyse reaction is over, product molecules may remain tightly bound to the enzyme, so the enzyme can’t form more than the cell needs.
what is end product inhibition an example of?
negative feedback
what does potassium cyanide turn into when ingested?
hydrolysed to produce hydrogen cyanide
what is hydrogen cyanide and what does it do?
a very toxic gas-readily dissociates into H+ and CN- ions.
how does potassium cyanide inhibit aerobic respiration?
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.
what does green mamba snake venom contain?
a chemical that inhibits the enzyme acetylcholinesterase (AChE)
what does green mamba snake venom cause?
paralysis
how does green mamba snake venom work/
acetylcholinesterase (AChE) inhibited, so acetylcholine (ACh) isn’t broken down. ACh stays attached to receptors on muscle membranes in neuromuscular synapses and keeps the muscles contracted.
what does salicylic acid do?
binds to enzymes that catalyse formation of prostaglandins.
what do prostaglandins do?
cell-signalling molecules produced when cells are damaged or inflamed: make nerve cells more sensitive to pain+increase swelling during inflammation.
what can aspirin also do?
reduce risk of blood clots in blood vessels, so many people take it to reduce risks of strokes.
why shouldn’t children under 12 take aspirin?
can damage their stomach lining
what is atrial arrhythmia?
abnormal beat rate of the atria
what are the cardiac glycoside chemical names?
digitalis
digitoxin
digitalin
digoxin
what do cardiac glycosides do?
inhibit sodium potassium pump in the cell membranes of heart muscle cells+allow more calcium ions to enter the cells. Ca2+ increases muscle contractions, strengthening the heartbeat.
what are cardiac glycosides?
ATPase inhibitors
what are ACE inhibitors?
medical drugs that inhibit the angiotensin converting enzyme (ACE)
what does ACE do?
operates a metabolic pathway that increases blood pressure
when are ACE inhibitors used?
1) lower blood pressure in patients with hypertension who can’t take beta blockers
2) treat heart failure
3) minimise risk of 2nd heart attack/stroke in patients who suffered myocardial infarction.
what is myocardial infarction?
heart attack
what are 2 examples of protease inhibitors?
1) amprenavir
2) ritonavir
what are protease inhibitors used for?
treating some viral infections
how do protease inhibitors work?
prevent replication of virus particles within host cells by inhibiting protease enzymes so viral coats can’t be made- often competitive inhibition.
what is a nucleoside?
a compound consisting of a base and a sugar.
how do nucleoside reverse transcriptase inhibitors work?
inhibit enzymes involved in making DNA using viral RNA as a template.
what are examples of nucleoside reverse transcriptase inhibitors ?
many antiviral drugs used to treat HIV, eg zidovudine and abacavir
What is a hypotonic solution?
Solution with a higher water potential than the cell- net movement of water molecules is into cell.
What is an isotonic solution?
Solution w the same water potential as the cell. Water molecules pass into and out of the cell in equal amounts.
What is a hypertonic solution?
Solution with a lower water potential than the cell- water moves out of cell.
what is a cofactor?
substance that has to be present in order for enzyme catalysed reactions to take place at an appropriate rate.
what is a prosthetic group?
molecule that is permanently bound by covalent bonds to an enzyme molecule.
what disease do you get if you have a deficiency of B12?
pernicious anemia
what disease do you get if you have a deficiency of folic acid?
megablastic anemia (large irregular RBCs)
what disease do you get if you have a deficiency of B3 (nicotinamide)
pellagra (diarrhea, dermatitis, dementia)
what disease do you get if you have a deficiency of B6?
elevated blood plasma triglyceride levels
what disease do you get if you have a deficiency of B1 (thiamine)?
beriberi (confusion, irregular heartbeat, muscular weakness, paralysis, heart failure)
how do you calculate q10?
rate of reaction at t+10/ror at t
HOW DOES AN ENZYME CHANGE THE SUBSTRATE?
BY DESTABILISING ITS BONDS.
WHEN DESCRIBING WHY AN ENZYME WORKS QUICKER ALWAYS SAY
MORE ENZYME SUBSTRATE COMPLEXES FORMED
WHY WOULD ENZYME CONC BE THE LIMITING FACTOR
IF ALL THE ACTIVE SITES OF THE ENZYMES ARE OCCUPIED
WHAT CAN PH DO TO ENZYMES
ALTER TERIARY STRUCTURE
AFFECT H/IONIC BONDS
DENATURE ENZYME
CHANGE CHARGE ON ACTIVE SITE
WHY ARE INDUCED FIT/LOCK AND KEY CALLED MODELS?
SHOW PEOPLE HOW ENZYMES WORK/ SIMPLE REPRESENTATION OF STRUCTURE/PROCESS
WHY IS INDUCED FIT ACCPETED OVER LOCK AND KEY
SUPPORTED BY MORE EVIDENCE+NEW RESEARCH
FITS EVIDENCE MORE CLOSELY THAN LOCK AND KEY
WHY WOULD LOW TEMP MEAN LOWER ENZYME RATE?
LESS KINETIC ENERGY
LESS CHANCE OF ESC FORMATION
BELOW OPTIMUM TEMP
WHY WOULD AN EZYME BEING FLEXIBLE INCREASE ITS ROR?
INCREASED CHANCE OF SUBSTRATE ENTERING ACTIVE SITE
EASIER FOR ACTIVE SITE TO CHANGE SHAPE
EASIER INDUCED FIT
WHAT MIGHT BE 2 DIFFERENCES IN DNA?
DIFFERENT SEQUENCE OF BASES
DIFFERENT PROPORTION OF BASES
