Enzymes

Indented area of surface of enzyme with a shape that's complementary to the shape of a substrate molecule

Chemical that speeds up rate of reaction and remains unchanged and resusable at end of reaction

Outside the cell

Inside the cell

Chemical reactions that take place inside living cells or organisms

Molecule produced from substrate molecules, by an enzyme-catalysed reaction

Molecule that's altered by an enzyme-catalysed reaction

Substance that must be present to ensure that an enzyme-catalysed reaction takes place at the appropriate rate. Some (prosthetic groups) are part of enzyme structure, others (mineral cofactors and organic coenzymes) form temporary associations with the enzyme

Prosthetic groups

Mineral ion cofactors and organic coenzymes

Complex formed from temporarily binding of enzyme and substrate molecules during enzyme-catalysed reaction

An apoenzyme with it's cofactor. It's complete and catalytically active

Inactive enzyme, activation occurs upon binding of an organic or inorganic cofactor

Enzyme molecule with product molecule in it's active site. The two are joined temporarily by non-covalent forces

Enzyme molecule with substrate molecule in it's active site. The two are joined by non-covalent forces

Temp coefficient, calculated by dividing rate of reaction at (T+10)°C by the rate of reaction at 7°C

Number of molecules per unit volume

Inhibition of an enzyme where inhibitor molecule has a similar shape to that of the substrate molecule and competes with the substrate for the enzymes active site. It blocks the active site and prevents formation of ESC's

Substance that reduces or stops a reaction

Inhibition of an enzyme, where the competitor molecule attaches to a part of the enzyme molecule but now the active site. This changes the active sites shape, preventing ESC's forming, as enzymes active site is no longer complementary to substrate molecule

Fungi (muccr on bread) releases hydrolytic enzymes and hyphae. Enzymes digest carbs, proteins and lipids in bread and products of digestion (glucose, amino acids, glycerol fatty acids) absorbed into fungal hyphae for respiration and growth

Salivary glands and pancreas

Digests polysaccharide starch into disaccharide maltose

Catalyses reaction of polysaccharide starch into disaccharide maltose in lumina small intestine

Pancreas

Acts lumen of small intestine to digest proteins into smaller peptides by hydrolysis of peptide bonds

Between 7.5 and 8.5

Cells lining alimentary canal into the gut lumen

Extracellularly digest large molecules e.g carbs, proteins, lipids and nucleic acids from foods

The absorbed via epithelial cells in gut wall into bloodstream to be used for respiration, growth and tissue repair

Hydrogen acceptors

Derivatives of nucleotides

Cobalamin coenzymes

Pernicious anaemia

Tetrahydrofolate

Megablastic anaemia

NAD and NADP

B3

Pellagra

Coenzyme A

B6

Elevated blood-plasma triglyceride levels

B1

Thiamine pyrophosphate

Benben

Small organic non-protein molecules that bind temporarily to the active site of enzymes either just before or at the same time the substrate binds

They are chemically changed

Need to be recycled to their original state

Causes disease

Water soluble vitamins

Starch to maltose

If chloride ions are present

May temporarily bind to substrate or enzyme to ease formation of ESC, increasing rate of reaction

Co-substrates

They and the substrate form the correct shape to bind to the active site

The charge distribution on the surface of the substrate or enzymes active site

Cofactor that's permanently bound, by covalent bonds, to an enzyme molecule

Zinc ion

Erythrocytes

Catalyses the interconversion of CO2 and H2O to carbonic acid which then breaks down to H+ and HCO3 -

Enables CO2 to be carried in blood from respiring tissues to lungs

1/time taken to reach end point

Between A and B, increasing temp increases rate of reaction due to increased KE

Increasing temp beyond optimum (B), temp reduces rate due to breaking of hydrogen bonds holding enzymes tertiary structure in place

At C, no reaction as enzyme is denatured

Increase in rate of a process when temp is increased by 10°C

Q10

2

For every 10°C rise in temp, rate is doubled

Rate is doubled by every 10°C rise in temp

Rise in temp provides more KE so enzyme and substrate molecules move faster and collide more often

Q10 drops

Because higher temps alter the structure of the active site of the enzyme molecules so no longer complementary to shape of substrate molecules

Rate of reaction at (T+10)°C / rate of reaction at T°C

Temperature at which enzymes work best and has max rate of reaction

When contain more disulfide bonds that don't break with heat and keep shape of protein molecule stable

Extra energy in form of heat, causes molecules to move faster

Increases rate of collisions between molecules

Increases force with which they collide, as they're moving faster

Both types of molecules will gain KE and move faster

Will increase rate of successful collisions

Rate of formation of ESC'S increases and ROR increases, increasing number of EPCs per second, up to a point

ROR reaches max at optimum temp

No

Heat doesn't break peptide bonds between amino acids

Vibrate

Brakes some of the weak bonds that hold tertiary structure of the active site

Active site shape begins to change substrate molecules don't fit so well rate of reaction starts to decrease

As more heat is applied shape of active site completely and irreversibly changes and no longer complementary to fit substrate

Reaction can't proceed

Enzyme is denatured

The measure of hydrogen ion concentration

Whether substances acidic alkaline or neutral

0-6

7

8-14

Protons and a negatively charged ion

Proton donors

H+ and lacate

H+ and pyruvate

Changes in pH

Chemicals in the blood can help resist changes in pH so blood pH remains close to 7.4

Hydrogen ions have a positive charge so attracted towards negatively charged ions or molecules

Excess hydrogen ions interfere with hydrogen bonds and ionic forces active site will change shape. If substrate doesn't fit well rate will decrease

Increasing concentration of hydrogen ions will alter charges on active site of enzyme has more protons will cluster around negatively charged groups in active site. Interferes with binding of substrate on to active site

Extracellular enzymes

6.8

Narrow range of pH

It will slow the races shape of active site is disrupted

Hydrogen bonds can we form an active site is restored

Active site may be permanently changed. Enzyme is denatured and can't catalyse reactions

1-2

HCL is secreted to kill bacteria and pathogens in food

Digests large protein molecules into smaller peptide molecules

7.8

Bile as it neutralizes the pH of the stomach

Optimum of protein digesting enzymes that catalyse further digestion of peptides to amino acids

Reducing or increasing pH away from optimum reduces rate as concentration of hydrogen ions in solution affect tertiary structure of enzyme

When touches x axis enzyme is denatured

Enzyme-catalyzed reaction can't happen because there are no substrate molecules to fit active site so no ESC can be formed

Concentration increases and rate increases

More ESC can be formed

As a result more product molecules are formed

Substrate concentration is limiting factor because as it increases rate increases

Reaction will reach max rate

Adding more substrate to increase of shape concentration won't increase rate as all enzymes active sites are occupied with substrate molecules

More substrate molecules are added can't successfully collide and fit into active site

Between A and B, substrate concentration is limiting factor. Increase substrate concentration leads to increased reaction rate

Between B and C all enzymes present are working at maximum rate. Substrate concentration no longer limiting factor another factor is limiting reaction

Rate of synthesis of the enzyme and its rate of degradation (rates directly controlled by cell)

Depending on cells needs, genes for synthesising particular enzymes can be switched on or off

Elimination of abnormally shaped proteins that could accumulate and harm the cell

Regulation of metabolism in cell by eliminating any superfluous enzymes

Control of enzyme degradation is equally important as the control of enzyme synthesis

More active sites on an enzyme become available

Most successful collisions between enzyme and substrate occur

More ESC can form per unit time so rats increases

Enzyme concentration is limiting factor - as it increases so does rate

All substrates will be occupying or will have occupied an active site and been released as products

Reaction is at max rate for fixed substrate concentration

If enzyme concentration is increased further, no increase in rate because active site of extra enzyme molecules won't be occupied by substrates

Enzyme concentration no longer limiting factor as enzyme concentration increases rate doesn't increase

Substrate concentration is now limiting factor. Lack of substrate molecules is preventing rate from increasing

Maximum rate of reaction

At beginning of reaction all moving randomly so great chance of substrate molecules successfully colliding with enzymes active site

As reaction proceeds substrates used up as converted to products to concentration of substrate

As result frequency of successful collisions decrease as enzyme to may collide with products reducing rate of reaction

A - enzyme concentration is limiting factor

B - enzyme concentration is no longer limiting factor, substrate concentration is limiting factor

C - is substrate concentration which is now limiting factor is increased then rate increases

D - fixed concentration of substrate

Reduce enzyme activity by combining with the enzyme molecule in a way that influences how the substrate binds to the enzyme

Block active site

Change shape of active site

Fit into active site so the substrate molecule can't enter

More inhibitors collide = greater effect of inhibitor

Relative concentration of substrate and inhibitor molecules

Dilute the effect of inhibitor and if enough substrate is added the inhibitor is unlikely to collide with enzyme

Compete directly with substrate on enzymes active site to form an enzyme inhibitor complex thats catalytically inactive

Once on active site inhibitor is unchanged by enzyme

Collisions are random

Inactivators

Green is competitive

Blue is not competitive

Attach to enzyme on allosteric site, away from active site, disrupting tertiary structure and changing its shape

Greater degree of inhibition as more enzymes distorted

The distortion changes shape of active site so no longer complementary to substrate. Vsc can't form

One way in which enzyme catalysed reactions can be regulated

Once catalysed reaction has reached completion, products stay tightly bound to enzyme meaning enzyme can't form more of the product than the cell needs

Negative feedback

Increase efficiency of metabolic reactions without increasing sub conc as keep enzyme and substrate in same vicinity to reduce diffusion time

In many antiviral drugs

Enzymes involved in making DNA using the viral RNA as a template

Medical drugs that inhibit the the angiotensin converting enzyme (ACE) which normally operates in a metabolic pathway to increase blood pressure

Lower blood pressure in patients with hypertension who can't take beta blockers

Treat heart failure

Minimise risk of second heart attack or stroke in those who have suffered a myocardial infarction

Abnormal beat rate of the atria

Inhibit the sodium potassium pump in the cell membranes of heart muscle cells no more calcium ions to enter (calcium ions increase muscle contraction to strengthen heartbeat)

Purple foxglove leaves

Heart failure and atrial arrhythmia

Toxins that are ingested

Inhibiting or inactivating enzymes

KCN

It inhibits aerobic respiration and catalase

KCN is hydrolyzed to produce hydrogen cyanide

KCN is hydrolysed to produce hydrogen cyanide that can readily dissociates into H+ and CN- ions

CN- ions bind irreversibly to an enzyme found in mitochondria and inhibits the final stages of aerobic respiration. As final stage is inhibited earlier stages can't run so aerobic respiration stops

Chemical in venom of green mamba snake

Important at neuromuscular synapss to break down neurotransmitter acetycholine

Acetycholinesterase

ACh stays attached to receptors on muscle membranes and keeps muscle contracted

As movement dependent on muscles contracting and relaxing alternately (inhibits relaxation)

If inhibits break down of nuerotransmitters in synapses of muscles involved in paralysis, stops breathing

Damages lining of stomach

Reduces chance of blood clots forming in vessels

Inhibits formation of prostaglandins (cell-signalling molecules which make nerve cells more sensitive to pain)

Treating some viral infections

Prevent replication of virus particles within host cells by inhibiting protease enzymes so copies can’t be made - often inhibit by competitive inhibition

Biological catalysts that speed up rate of reaction by lowering activation energy

Number of reactions an enzyme can catalyse per second

Low temp

Neutral pH

Normal pressure

Don’t produce unwanted by-products and barely make mistakes

In genes

Alters sequence of AA’s, alters secondary, tertiary structure and therefore prevents structure

Determines the active site which is complementary to substrate molecule

Metabolites broken down to smaller molecules and releasing energy

Using energy to synthesise larger molecules from smaller ones

In almost all living organisms exposed to O2

Protects cells from damage by reactive O2 by quickly breaking down hyd peroxide to water and O2

4 polypeptide chains

Iron haem group

Catalase (6mil/s)

Peroxisomes

7

Lowered levels of catalase so more hyd peroxide bleaches hair shafts from inside

Substrate and enzymes both have KE and constantly moving around

If successfully collides, fits into AS complementary shapes. Temp hyd bonds hold together forming ESC

Substrate broken into products, forming EPS

Product molecules leave active site, leaving AS unchanged

The lock and key theory doesn’t explain how ESC is stabilised

AS complementary to substrate - when binding, R groups of AA change shape of AS slightly to give better fit

Esc formed and non-covalent forces e.g hyd bonds, ionic attractions etc bind substrate to AS

Substrate into products, forming EPC

Products detach AS

Enzyme free to catalyse further reations

Temp/pH can’t be raised in body to increase KE as proteins would denature and lipids would melt