Enzymes

Question 1

Activation energy -

Answer 1

Minimum energy required for most reactions to start.

Question 2

Lock and key hypothesis -

Answer 2

An area with the tertiary structure of the enzyme has a shape complementary to substrate molecules (active site) when the enzyme-substrate complex is formed, the substrates react and the product or products are formed. The R -group within the active site will form temporary bonds.

Question 3

Induced-fit hypothesis -

Answer 3

Research has suggested that the binding of the substrate in the active site changes the active site slightly. (induced fit), initial reaction between the two is weak but these reactions cause changes in the enzyme’s tertiary structure. May be strain on the substrate molecule, therefore lowering the activation energy.

Question 4

Intracellular enzymes -

Answer 4

Enzymes that act within the cell, idea of the synthesis of polymers into monomers E.G polysaccharides to glucose. Hydrogen peroxide is toxic of metabolic pathways, catalase makes sure it is broken down into oxygen.

Question 5

Extracellular enzymes -

Answer 5

Enzymes that are released from inside the cell are used to break down nutrient molecules into smaller molecules for digestion. For example Fungi enzymes work outside the cell. Both multicellular and unicellular use extracellular enzymes. Examples are amylase and trypsin

Question 6

How do unicellular organisms use their enzymes - (changes of polymers)

Answer 6

Break down larger molecules into their immediate environment such as proteins are make them into smaller molecules like glucose and amino acids.

Question 7

How do multicellular organisms use their enzymes - (Changes of polymers)

Answer 7

Mainly eat food to gain nutrients, even still the larger molecules digested still have to be digested smaller so they can enter the bloodstream, then they can be used as substrates around the body.

Question 8

Digestion of starch -

Answer 8

• Begins in mouth to small intestine.
  1. Starch polymers are partially broken down into maltose (disaccharide), amylase involves in this stage, produced in the salivary glands and the pancreas.
  2. Maltose is then broken into glucose, from the enzyme maltase, which is present in the small intestine, the glucose is then absorbed into the bloodstream.

Question 9

Digestion of proteins -

Answer 9

Trypsin is a type of protease. Proteins into smaller peptides, also produced in the pancreas the amino acids produced are absorbed by the action of proteases and absorbed into the digestive system.

Question 10

Temperature on enzyme activity -

Answer 10

More temperature increases the kinetic energy of particles. Move faster and collide more frequent, resulting with more successful reactions with substrate and enzyme, the temperature coefficient of a reaction is measure of how much the ROR increases with a 10 degrees Celsius rise in temperature.

Question 11

Denaturation from temperature -

Answer 11

All enzymes are proteins and structure is affected by temperature, as the vibrations increase the bonds strain and break, changes the tertiary structure and is said is to become denatured.

Question 12

Optimum temperatures -

Answer 12

Optimum in the body is 40 degrees, once these enzymes have denatured above the optimum the decrease in the ROR is rapid, only needs a change in the active site for it to become ineffective at catalysing reactions.

Question 13

Temperature extremes -

Answer 13

Some organisms have evolved in order to cope with living in certain conditions, for example extremely cold temperatures like oceans, where there enzyme controlled activities need to be adapted to the cold, these have more flexible structures making them less stable than enzymes. Whereas, thermophiles are adapted to living in hot environments, there are ore stable due to there increased level of bonds, particular hydrogen and sulfur bonds, there are more resistant to changes as the temperature rises.

Question 14

pH -

Answer 14

Enzymes are affected by changes in pH, hydrogen and ionic bonds between r-groups in amino acids hold the proteins in 3D shapes, these bonds result from the interactions between the polar and charged R-groups present on the amino acid present on the primary structure, a change in pH refers to a change in hydrogen ion concentration, more are present in low pH (acid) environments whereas fewer are present are in high pH (alkaline) environments. The active site will only be right at optimum pH. The active site and bonding is changed if altered by increasing or decreasing. If it returns to normal after the change this is renaturation.

Question 15

What happens when the pH changes too much?

Answer 15

Enzyme is said to be denatured and substrates can no longer bind and the process is seen as irreversible, the hydrogen ions interact with polar and charged R -groups changing the degree of interaction, the more present (acid) the less r-groups are able to interact, leading to bond breaking, When fewer hydrogen ions are present the shape of the enzyme will change as the pH changes.

Question 16

Substrate and enzyme concentration -

Answer 16

Increased substrate particles leads to a higher collision rate with the active sites of enzymes and the formation of more enzyme-substrate complexes, increases ROR. Also the same for enzymes as more active sites become available leading to a greater chance of binding. The ROR increases up to the maximum (vMax) where all the active sites are occupied and no more E/S complexes can form.

Question 17

What other factors can influence metabolic activities -

Answer 17

Enzymes can be activated by coenzymes, cofactors and prosthetic groups and can be inhibited by inhibitors or they inactivate the enzymes.

Question 18

Competitive inhibition - (competes for the active site)

Answer 18

A molecule may have a similar shape which can fit into the active site. This blocks the substrate from entering preventing the reaction from being catalysed, the enzyme cannot carry out it’s function and is inhibited. The substrate and non-substrate (inhibitor) will compete for the active site this will reduce the chance of essential substrate from binding and slow down the ROR. But it doesn’t change the vMax of the enzyme, if the substrate concentration is increased enough there will be much more substrate than the inhibitor so the original vMAX can still be achieved.

Question 19

Examples of competitive inhibitors -

Answer 19

Statins - used in the synthesis of cholesterol, they are used to help blood cholesterol concentration.

Question 20

Non-competitive inhibitors -

Answer 20

The inhibitor here binds to the enzyme not the active site this is called the allosteric site. This causes the tertiary structure to change. Meaning the enzyme doesn’t have a complementary shape for the substrate to fit, so the enzyme-substrate complex is inhibited. The increase of concentration of enzyme or substrate will not overcome the effect of non-competitive inhibitor. Unlike competitive inhibition. But increasing the concentration of this inhibitor will decrease the ROR due to the level of unavailable active sites.

Question 21

Examples of non-competitive inhibitors -

Answer 21

Proton pump inhibitors used to treat long-term indigestion.

Question 22

End-product inhibition -

Answer 22

Term for enzyme inhibition that occurs when the product of the reaction acts as inhibitor to the enzyme, serves as negative feedback control mechanisms for the reaction.

Question 23

Cofactors, coenzymes and prosthetic groups are called?

Answer 23

Enzyme activators.

Question 24

Difference between cofactors and coenzymes -

Answer 24

Cofactors are non-protein helpers in order to help biological catalysts they can be both derived from the diet however coenzymes act as organic cofactors whereas cofactors are inorganic cofactors. Loosely bound.

Question 25

Prosthetic groups -

Answer 25

Play a role in some coenzymes to carry out catalytic functions these are tightly bound and permanent features of proteins whereas cofactors are loosely bound for example Zn 2+ important in the structure of carbonic anhydrase.

Question 26

Precursor activation -

Answer 26

Many enzymes are produced in the inactive form, known as inactive precursor enzymes, particularly enzymes which can cause damage within cells, these often undergo a change in their tertiary structure particularly to the active site to be activated it can receive the addition of a cofactor before it is added the precursor protein is called an apoenzyme , when the cofactor is added it is called an holoenzyme. Sometimes the change of other enzymes can be due to other enzymes such as protease.