Biology C1.1- enzymes and metabolism

enzymes description

• are catalysts

• 3D proteins that speed up chemical reactions

• interact with substrates and substrate molecules

  • control the rate of reactions

metabolism

complex network of interdependent and interacting reactions occurring in living organisms

anabolic reactions

“build up”

• build macromolecules

  • require energy input to occur

anabolic reaction examples

condensation reactions, photosynthesis

catabolic reactions

“break down”

• break down macromolecules into monomers

  • release energy as they occur

catabolic reaction examples

hydrolysis, oxidation reaction, digestion

what living organisms are dependent on

• C - carbon

• O- oxygen

  • H - hydrogen

metabolic pathway

• cells make things in steps and each step needs an enzyme

1. substrate goes into enzyme 1 → intermediate 1

2. intermediate 1 goes into enzyme 2 → intermediate 2

3. intermediate 2 goes into enzyme 3 → final product

what happens when there is too much product

the product goes back and blocks enzyme 1 which stops the whole pathway so the cell doesnt waste energy

how you get more control over reactions

chemical changes in living things often occur with a number of stages

describing metabolic pathways

• cycle / chain of enzyme catalysed reactions

• chemical change from 1 molecule to another

• not often happening in large jumps'

• sequence of small steps

  • small steps = metabolic pathways

are enzymes globular

yes

enzyme structure

tertiary

active site

region / area of an enzyme surface that has a specific shape, composed of a few amino acids with complimentary base pairing

exergonic

• release energy

• more energy is released when chemical bonds form its products then is needed to break the bonds in the reactants

• exothermic reactions

• product has less energy than the reactants of an experiment

exergonic graph

endergonic graph

endergonic

• takes in energy

  • more energy is needed to break the bonds in the reactants than is released when the product is formed

  • endothermic reaction

  • product has more energy than the reactants of an experiment

induced fit theorey

• explains the broad specifity of enzyme activity

• needing to be similar enough to work

  • imrpovement of lock and key method

ATP

adenine TRI phosphate

• energy currency of a cell

ADP

adenine DI phosphate

• looses a phosphate

activation energy

• energy storage molecule

• energy necessary to destabalise the existing bonds in a substrate so the reaction can proceed

  • lowering the activation energy = increased chemical reactions = bonds broken easier

ATP functions

• supplying energy - needed to synthesize large molecules

  • supplying energy for mechanical work - muscle action

collision theorey

• substrates entering with a minimum rate of motion (kinetic energy)

• that will provide the energy necessary for the reaction to occur

• enzymes dont provide this energy, they just lower it

ways of overcoming the energy barrier and increasing the rate of reactions

• increase energy of the reacting molecules which increase the rate of collisions

  • lowering the activation energy so bonds can break more easily

thermodynamic reaction examples

exergonic, endergonic

intracellular enzymes

enzymes that occur within a cell

extracellular enzymes

enzymes that occur outside a cell

do groups of enzymes work together in incremental steps inside and outside the cell

yes

linear pathway

• happens in a fixed sequence

• each step converts the substrate into a product which becomes the substrate for the next enzyme

• clear start and end point

• if one enzyme stops working, the whole pathway is affected

linear pathway example

glycolysis

cyclic pathway

• arranged in a loop

• starting molecule is regenerated at the end so the pathway is continued repeatedly

  • each step is controlled by a specific enzyme

cyclic pathway example

krebs cycle in respiration and calvin cycle of photosynthesis

cyclic pathway drawing

linear pathway drawing

inhibitor

• a molecule that binds to an enzyme and slows down / stops the enzymes function

• enzymes can be inhibited by other molecules

  • inhibition can either be competitive or non competitive

competitive inhibition drawing

non competitive inhibition drawing

competitive inhibition

the inhibitor fits into the active site and prevents the substrate from entering

non competitive inhibition

inhibitor fits into an allosteric site which causes a change in the active site so the substrate cant attach to react

allosteric site

other site

non competitive inhibition example

cyanide ions blocking cytochrome oxide in oxidation

competitive inhibition example

O2 competing with CO2

non competitive inhibition graph

as the concentration of inhibitors increase, the rate of reaction decreases and fewer functional active sites are available for a reaction

competitive inhibition graph

same maximum rate will be achieved. if there is more inhibitor, the faster it will take to reach the maximum rate but no number of enzymes have changed

competitive inhibition consequenses

high levels of cholesterol means blockages in blood vessels which can lead to cardiovascular disease

statins

• act as drugs and competitive inhibitors

• combine with the active site of an enzyme

• essential catalyzing the biosynthesis of cholesterol within the liver

isoleucine

• essential for amino acids

• as concentration increases, some of it binds to the allosteric site

• acts as non competitive

  • then the pathway is turned off

end product of isoleucine

• usually involves the allosteric site

• usually reversable when toxins and poisons are involved

  • substrate combines with an allosteric site

penicillin

• irreversible inhibitor which binds to transpeptidase (makes bacteria cell walls)

• inactivates transpeptidase by bonding to a particular chemical group at the active site

  • defensive cell wall prevents bacterial reproduction

why arent humans effected from penicillin

dont have cell walls

the change from penicillin

• some satin bacteria have become resistant to penicillin due to mutation

  • penicillinase attacks molecular structure of penicillin by breaking specific bonds

how to treat satins

scientists change the structural makeup of penicillin to produce variants that arent inactivated by penicillinase

what allows them to produce an enzyme called penicillinase

some satins of bacteria have become resistant to penicillin due to mutation

denaturation

• structural change in proteins active site that results in a loss of its biological properties

  • enzymes depend on the shape of their active site to function

factors affecting enzyme activity

high temperatures, extreme pH, concentration of the substrate

process of denaturation

causes the active site of an enzyme to change shape since the bonds are broken and that enzyme wont work anymore

how the spread of a reaction can be measured

• how fast the substrate disappears

• how fast the product is formed