c1.1: enzymes and metabolism

enzyme substrate complex

- enzymes are globular proteins that catalyze, or speed up, reactions

- They have an active site where the specific substrate, or reactant binds to on the enzyme to form an _________________ _____________ _______________

- this reaction produces a product that is released from the enzyme

- this requires motion and collision between substrates and active sites

- these reactions may occur naturally, but without enzymes, to slowly

catalytic cycle

substrate is sucrose (glucose and fructose)

substrate binds to enzyme

water is added

stress is placed on the bond

products are released and enzyme can bind to other substrates

metabolism

all enzyme catalyzed reactions in a living thing

- anabolic and catabolic reactions

- independent or interact w other reactions

- enzyme specificity= many enzymes controlling metabolism

anabolism

synthesis of complex molecules including macromolecules from monomers by condensation reactions with the formation of water

- protein synthesis from amino acids on ribosomes

- glycogen from glucose

- photosynthesis

catabolism

breakdown of complex molecules including hydrolysis of macromolecules into monomers by splitting water, releases energy

- digestion of food

- oxidation of substrates during cell respiration

globular proteins and active sites

enzymes= globular proteins

- enzyme and active site= 3 dimensional

- active site= part of the enzyme that the specific substrate/reactant attaches to, made up of amino acids

- interaction between amino acids= 3 dimensional structure to bind to specific substrate + catalyze reactions

- enzymes can be denatured if the temperature or PH is altered

enzyme activation

induced fit model

activation energy

induced fit model

both the enzyme and the substrate change shape slightly when binding

activation energy

energy required for a reaction to occur

- enzymes catalyze reactions by lowering the energy required of the activation energy

exergonic reaction

more energy is released when binds form in the products than is required to break the reactants bonds

- overall loss of energy

- cell respiration

endergonic reaction

more energy is required to break the bonds in the substrate/reactant than is released when the products form

- overall gain of energy

- photosynthesis

molecular motion

enzymes and substrates coming together requires collisions between the two

more energy, (heat) means more collisions

- some enzymes and subtrates are anchored, making it easier to join substrates and active sites

mechanism of enzyme action

1. specific substrate makes contact with the active site of an enzyme

2. the enzyme and the substrate change shape to fit with one another

3. they form a temporary enzyme substrate complex

4. enzymes lower activation energy of the reaction and the substrate is altered when the atoms are reaarranged

5. the altered substrate is released from active site

6. the enzyme can be reused

factors affecting enzyme catalyzed reactions

temperature

PH

substrate concentration

Temperature

- in liquid, heat increases movement of molecules

- both enzymes and substrates have a greater chance of colliding

- as enzyme continues to heat, denaturation occurs and shape is altered (including active site)

- denaturation happens at temperatures that are too high

- enzyme activity falls or may stop altogether

PH

- enzymes have an optimum PH that varies between enzymes

- if PH increases (basic) or decreases (acidic) activity drops due to denaturation causing shape, (including active site) to change

substrate concentration

- more enzymes, more substrates = more collisions

- increase is not exponential. if enzymes and substrates are plentiful while substrates are bound to an active site, it blocks other substrates from binding

- enzyme activity plateus as only a certain number of products can be made when all enzymes are working at the same time

metabolic efficiency

- inefficient transfer of energy within a food web in an ecosystem is due to the fact that transfer of energy in metabolic reactions is not 100%

- energy not transferred is lost as heat

- heat is necessary for animals to maintain their body temperature

- ectotherms do not eat a lot so they do not produce enough heat to maintain their body temp and rely on the environment

intracellular reactions

- enzymes are present inside and outside of cells

- breakdown of glucose through cellular respiration is intracellular because glycolysis occurs in the cytoplasm and krebs cycle takes place in the mitochondria

extracellular reactions

- enzymes are present inside and outside of cells

- chemical digestion in the alimentary canal of the food we eat is catalyzed by extracellular enzymes

free floating

there are many reactions that occur as the result of several enzymes working together in a metabolic pathway or cycle inside and outside of cells. these may involve free floating enzymes or ones bound to a membrane within an organelle or the cell membrane

metabolic pathways

linear and cyclic

- specific sequence of metabolic reactions, using multiple enzymes along the way, that use the product of one reaction as the reactant in another

linear pathway

final product that is different than the initial reaction or substrate.

- can be regulated by end product inhibition

- ex: glycolysis

cyclic pathway

- initial reactant is reformed as a product by the end of the pathway

- ex: krebs cycle and calvin cycle

competitive inhibition

- competitive inhibitor will have a similar structure to the usual substrate in the metabolic reaction

- it will bind to the active site of an enzyme, but no reaction will occur because it is not the specific substrate

- blocks active site, and prevents the proper substrate from binding. rate of reaction decreases

- affected by substrate concentration (more subtrates= less competitors binding)

- reversible

- statins= prescribed to block enzyme that synthesizes cholesterol

non competitive inhibition

allosteric enzymes have a binding site other than the active site

- specific non competitive inhibitor binds to allosteric site changing the shape of the active site. do not compete with substrate

- end product can inhibit the enzyme for an early/first step in a metabolic pathway (negative feedback)

- inhibition is reversible and not influenced by substrate concentration

feedback inhibition

end product inhibition

- final product, when a certain concentration has been made, will turn off the molecular machine by binding to the allosteric site

- changes the shape of active site and inhibits it to keep more from being made

- when more of the final product are needed, inhibitor will break free, active site will reform, pathway will resume

mechanism based inhibition

- chemical changes to an active site caused by irreversible binding of an inhibitor

ex: transpeptidase

- transpeptidase forms cell walls

- penicillin (irreversible inhibitor) binds to a certain chemical group on the active site of transpeptidase so the cell wall cannot form leading to the death of bacteria

- if mutations to bacteria's transpeptidase lead to an altered active site that penicillin cannot bind to , they would be resistant