Enzymes

What are enzymes made up of

Proteins

What are some organelles that contain catalase

Peroxisomes

Anabolic reactions…

Build things up

Catabolic reactions…

Break things down

What are enzymes

Biological catalysts

Examples of intracellular enzymes

Catalase

Examples of extra cellular enzymes + things that use them

Digestive enzymes- amylase, protease, bacteria, mould

Why is the tertiary structure of enzymes important

Give them their properties

What happens to enzymes in reactions

They are not used up

What can effect enzymes

Temperature and pH

How do enzyme work

By reducing the activation energy

Activation energy

Minimum energy required for a reaction to occur

Types of reaction you can have

Endergonic + exergonic

Exergonic reaction

Energy output > energy input / activation energy

Endergonic reactions

Energy input/ activation energy > energy output

How is activation energy lowered

Reactants are held close together in exposed positions on active sit, there are strains or tensions within the substrate molecule to change their shape to make them fit better, special conditions at active sit eg r groups, prosthetic groups

key inorganic ions

Ca2+, Na+, K+, NH4+, NO3-, HCO3, Cl-, PO4 3-, OH-

Rate of reaction=

1/ time taken

Optimum temperature

The temperature at which the enzyme has the highest rate of reaction

What happens as temperature increases

To the optimum, rate increases as the kinetic energy of enzyme and substrate increases d there are more successful collisions

What may prevent successful collisions

Active sit may to be available- may already be a substrate there

What happens beyond optimum temperature

Enzymes denature as they gain more kinetic energy so the bonds in the tertiary structure vibrate more and eventually break meaning the shape of the active site has changed and is no longer complementary to the substrate

Temperature coefficient

Qn= rate at (t + n degrees)/ rate at t degrees

Lock and key model

Substrate and active site are complementary

Induced fit model

Enzyme and substrate may not be completely complementary so during reaction when r groups in enzymes react with the substrate the shape changes slightly so the substrate fits more snugly

How does pH effect rate

Unlike temp either side of the optimum denaturation occurs as H+ ions can affect the bonding between r groups and may cause ionisation meaning the tertiary structure is changed

Why is the rate fastest at the start

When the reaction first begins there are a lot of successful collisions as the number of free active sites is high and the number of substrates is high

Why does rate decrease with time

Number of successful collisions decreases as substrate molecules are used up and number of active sites decreases

Effect of concentration on rate

Starts at a high rate as chance of successful collisions is greatest

Cofactors

Small inorganic parts of enzymes that they need to work

Common features of cofactors

Are always non protein, often need to be in the active site, often ions, within structure of enzymes

Examples of cofactors

Cl- ions are cofactors for amylase, Fe+ ions are cofactors in catalase

Coenzymes

Organic parts that enzymes need to work

Features of coenzymes

Non protein, large, often have a temporary role, large

Examples of coenzymes

NAD derived from Vito B3 needed in aerobic respiration, coenzymeA derives from vitamin B

What are cofactors+ coenzymes called if they are permanently bonded

They rae prosthetic groups

Competitive inhibitors

Prevent escs from forming as are also complementary

Features of competitive inhibitors

Often reversible, can be naturally occurring, stops reaction, prevent ESCs from forming

Non competitive inhibitors

Is allosteric inhibition that changes the shape of the enzyme by changing its tertiary structure

How do non competitive inhibitors work

Bind to the anyone’s allosteric site rather than its active site

Features of non competitive inhibitors

Changes shape of active site, often irreversible, tend to be drugs or poisons

Compared to the normal rate of a reaction, what happens with a competitive inhibitor

There is a lower rate of reaction- the reaction still goes to completion and max rate of reaction is reached just slower

Compared to the normal rate of reaction what happens when a non competitive inhibitor is introduced

Rate of reaction is slower- max rate/rate without inhibitor is not etched as the number of ESCs are reduced due to the permanent changes that occur

End product inhibition

When the inhibitor is non competitive and the last product

What happens during end product inhibition

The end product binds to an enzyme allosterically earlier in the sequence, inhibiting itself

How does end product inhibition work

Greater inhibition leads to a decrease in amount of end product, inhibition decreases in he conc. of end product decreases- is a negative feedback loop

Intracellular enzymes

Enzymes that act within cells

Extracellular enzymes

Enzymes that are released from the cells to work outside of the cells

Why are extracellular enzymes needed

Large molecules such as nutrients in the forms of polymers such as proteins and polysaccharides are too large to enter the cells directly so need to broken down

Role of extracellular enzymes in single and multi celled organisms

Rely on EE for nutrition - single celled organisms (bacteria and yeast) release EE to break down things such as proteins into amino acids and glucose, multicellular organism use them to break things down in the digestive system

How is starch digested

Digested in two steps with two different enzymes

First step of starch digestion

Starch polymers are partly broken down into maltose using the enzyme amylase

Where is amylase produced

Saliva, pancreatic juices in small intestine

Stage 2 of starch digestion

Maltose is broken down into glucose using enzyme maltase

Where is maltase found

Small intestine

Which enzyme catalyses the digestion of proteins

Protease enzymes

How are proteins digested

Broken down by protease enzymes into smaller peptides that can be broken down in to amino acids which are then absorbed by cells lining the digestive system to be absorbed by bloodstream

Example of a protease enzyme

Trypsin

Where is trypsin produced and where is released to

Produced in pancreas, released into smn all intestine with the pancreatic juices

How to calculate rate of reaction for a gas producing reaction

Volume/time