Enzymes (1st year) Topic 4

Question 1

What is an enzyme?

Answer 1

An enzyme is a protein catalyst which speeds up the rate of a specific biological chemical reaction.

Question 2

What is a catalyst?

Answer 2

A catalyst is a substance increases the speed of a chemical reaction.

Question 3

Therefore,what can we call enzymes?

Answer 3

Biological catalyst which speed up chemical reactions taking place in the body.

Question 4

Without enzymes,the reactions taking place inside of the body would be too slow to maintain life. So what is another role that enzymes have?

Answer 4

They serve to reduce the ammount of energy needed for a chemical reaction to take place.

Question 5

What are the reactions inside all of the cells called?

Answer 5

Metabolism

Question 6

What are the 2 types of metabolism and give examples.

Answer 6

Catabolism and Anabolism.

Catabolism : biological chemical reactions which break things down. For example: Glucose is broken down into carbon dioxide and water to produce energy.

Anabolism: biological chemical reactions which build things up. For example: Glucose is built into glycogen for storage

Question 7

Mention some properties of enzymes

Answer 7

1) Enzymes are highly specific because they work on a particular substrate
2) All enzymes are protein because they are coded by DNA.
3) Catalysists: increase the rate of a reaction without being used up so they can be used over and over again.
4) The activity of enzymes can be influenced by their environment : ph,temperature,availability of coenzyme molecules (vitamins),substrate concentration or enzyme concentration
5) The catalysed reaction is reversible

Question 8

What do we call an enzyme + substrate?

Answer 8

Enzyme substrate complex

Question 9

What is the substance on which an enzyme acts on?

Answer 9

Substrate

Question 10

Name the part where the chemical reaction takes place on the enzyme.

Answer 10

Active site.
The active site is made up of amino acid side chains which give the enzyme a 3D dimensional shape,this is what makes enzymes highly specific.

Question 11

What is the concept that enzymes work by?

Answer 11

The Lock and key concept

Question 12

Which is the “lock” and which is the “key”?

Answer 12

The enzyme is the “lock” and the substrate is the “key”. The substrate will fit into the region of the active site

The reaction takes place and the product/s are formed,the enzyme can take up another substrate molecule

Question 13

What type of fit can we use to describe the chemical reaction taking place

Answer 13

The substrate connects with the enzyme in an induced fit,forming the enzyme substrate complex

The substrate will often chnage into the shape of the active site fitting into what we call an induced fit.

Question 14

What is the enzyme substrate complex converted into?

Answer 14

An enzyme product (ES) = (EP)

Question 15

What exactly happens in catabolic reactions?

Answer 15

These types of catabolic enzymes speed up those reactions which beak down large molecules into smaller ones. For example in digestion when maltose is broken down into glucose and glucose

Question 16

What does the enzyme amylase act upon?

Answer 16

Starch to produce maltose

Question 17

What do we call the new substance/s ?

Answer 17

Product/s

Question 18

Define exactly what happens in anabolism.

Answer 18

These are types of enzymes whch speed up the rate of specific biological chemical reactions by gathering small molecules and making them into larger ones. These are usually important to build molecules which are needed by our cells ex: glucose and glucose are build up to make maltose

Question 19

Distinguish between intracellular and extracellular enzymes.

Answer 19

Intracellular enzymes are enzymes: enzymes which have been produced in a cell to be used in the same cell.

Ex: enzymes which have been made in a cell,which are needed for respiration,they will be used in the mitochondria of that same cell.

Extracellular enzymes: enzymes which have have been made in a cell,but are going to be used somwhere else in the body outside of that same cell.

Ex:in the digestive system of animals,extra cellular digestive enzymes are released into the stomach and intestines to figest the food

Question 20

Where are all enzymes made?

Answer 20

In the cells

Question 21

What is activation energy?

Answer 21

The energy needed to form a high energy-intermediate to form a reactant to a product

The reactants do not have the same ammount of energy as the products

Question 22

What is the transition state?

Answer 22

Its when the reaction is taking place but the reactants have not uite fully formed into the products yet.

The reactants need to have a sufficient form of energy in order to be able to overcome the barrier of the transition state between the reactant and the product

Question 23

True or false. enzymes do not change the free energies of the reactants or the products and therefore,do not chnage the equlibrium of the reaction

Answer 23

True

Question 24

The higher the activation energy,the slower and harder the chemical reaction would be to occur.

Answer 24

True

Question 25

The lower the activation energy,the easier it is for the reactants to overcome the energy barrier to pass over the transition state ,allowing the reaction to occur

Answer 25

True

Question 26

How can enzyme activity be regulated?

Answer 26

By inhibition or by activating it according to the needs of the cell/body

Question 27

Mention some factors which influence the velocity of an enzymatic reaction.

Answer 27

Temperature,ph,substrate concentration,enzyme concentration

Question 28

At what optimum temperature do enzymes work the best in?

Answer 28

37-40 degrees celscius

Question 29

What will happen if the temperature is below 37-40? (not the optiumum temperature)

Answer 29

The rate of enzyme action is slow (inactive/dormant)

Question 30

What will happen if the temperature increases to 37-40 degrees celsicus?

Answer 30

The rate of enzyme reaction is faster. Thereofre,the reaction will taker shorter to finish and occur,because the speed of the reaction increases and the molecules of the reacting substances move faster and come closer together

The enzymes have a lot of kinetic energy

Question 31

What will happen if the temperature rises above 40 degrees?

Answer 31

The enzymes become denatured. This is because when the temperature increase the molecules start to move so much that the heat destroys the hydrogen bonds and covalent bonds of the enzyme become destroyed. The active site also becomes destroyed so the enzyme cannot take in the substrate,because the enzyme is denatured. The enzyme has chnaged shape. Proteins are denatured by heat.

Question 32

What is peak temperature?

Answer 32

This is the optimum temperature at which enzymes work the best at.

The temperature increases until a peak velocity is reached.

Question 33

Sketch a graph to show this demonstration.

Question 34

What do we mean by the term ph?

Answer 34

We are referring to the acidicity or alkilinity of a solution.

Furthermore we are referring to the ammount of hydrogen ions present in order for a specific enzyme to work optiumuley.

Question 35

Different enzymes work best in different ph,mention some examples.

Answer 35

The enzyme pepsin found in the stomach works best at a ph of 2

The enzyme salivary amylase works best at a neutral ph of 7 in the mouth.

Question 36

True or false. Enzymes become denatured in extreme changes of ph.

Answer 36

True.

The active site becomes unfunctional due to the hydrogen bonds being denatured.

Question 37

At which ph do most enzymes work the best in?

Answer 37

7

Neutral ph

Question 38

Sketch a graph to show optimum ph for enzymes

Question 39

What will happen if substrate concentration is increased? How will it affect the rate of enzyme action?

Answer 39

The rate of reaction increases with increasing substrate concentration,HOWEVER up to a maximum limiting value.

Any further increase in substrate concentration will produce no change

Question 40

Explain why it increases up to a point.

Answer 40

This is because all of the active sites of the available enzymes present are all occupied by the substrates. The enzyme substrate complex needs to dissociate before it can take up a new substrate.

All the enzymes are in an enzyme substrate complex state.

Question 41

Sketch a graph to prove this

Question 42

Explain why increasing enzyme concentration influences the rate of enzyme reaction

Answer 42

As the enzyme concentration increases,there are more active sites available. This increases the rate of reaction,therefore making reaction time short.

Question 43

Sketch a graph to show how this happens

Question 44

Why does the rate of reaction increase?

Answer 44

This is because if a substrate concentration is present,and more enzymes are increasing (enzyme concentration is increasing) the chnace that the molecules will bump into each other is higher,and forming an enzyme substrate complex is higher

Question 45

However why after maximal velocity is reached,adding more enzyme molecules will not increase the rate of reaction.

Answer 45

This is because if the enzyme concentration continues to increase, the concentration of substarate might diminish. So then not all enzyme molecules will find a substrate to bind to. So the rate will not increase

Question 46

What are inhibitors?

Answer 46

Any substance that can diminish an enzymatic chemical reaction taking place is called an inhibitor

Question 47

Name the 2 types of inhibition

Answer 47

Competitive and non-competitve

Question 48

Describe what is reversible inhibition and non-reversibile inhibition

Answer 48

Reversible inhibition: inhibitors which bind to enzymes but then dissociate,allowing the enzyme to work again.

Non-reversible inhibition: inhibited enzymes do not re-gain activity (permanent) (inhibitor doesnt dissociate)

Question 49

Define competitive inhibition

Answer 49

The inhibtor binds reversibly to the active site that the substrate would normally occupy,therefore the inhibtor is competing with the substrate to occupy the active site.

Inhibtor has the same shape as the substrate

Question 50

How is the effect of a competitive inhibtor stopped?

Answer 50

By increasing substrate concentration

Question 51

Define non-competitve inhibition

Answer 51

Occurs when the inhibtor and the substrate bind at diffrent sites on the enzyme.

Inhibtor has a diffrent shape

effect on vmax.

Non-competitve inhibition cannot be easily hnaged by increasing substarte concentration

Question 52

How does the non-competitve inhibtor prevent the reaction from occuring?

Answer 52

By chnaging the active site’s structure.

Question 53

We can find enzymes in everyday life. For example in industrial processes. Mention some examples where enzymes are used in everyday life.

Answer 53

They can be used to make bread,wine,youghurt, cheese

They can be used in biological washing powders. Enzymes do not need very high temperatures to work so electricity is saved. Enzymes break down and dissolve stains on the clothing fabric.

The enzyme rennin is used to make cheese and clot milk