M1:08 Enzyme intro

Question 1

Describe the structure of a globular protein

Answer 1

it has a specific three dimensional shape or tertiary structure, with hydrophobic amino acids on the inside and hydrophilic amino acid R-groups around the outside of the ball.

Question 2

Give 5 ways in which all enzymes are similar

Answer 2

• they are all globular proteins, generally soluble in water- they act as catalysts, speeding up chemical reactions, but was not used up as part of the reaction- they are specific, catalysing a reaction involving only one type of substrate - the globular structure contains a pocket or cleft area are called an active site- their activity is affected by temp and pH

Question 3

How large is the active site of an enzyme in comparison to the total size?

Answer 3

very small, there are thousands of amino acids in an enzyme. (often fewer than 10 of these enzymes make up the active site)

Question 4

What is the role of the majority of the amino acids within an amino acid?

Answer 4

they are involved in maintaining the specific tertiary structure, which enables the enzyme to function properly.

Question 5

Name one of the main advantages to enzymes

Answer 5

they are specific to one catalytic and does not produces a range of unwanted by-products.

Question 6

What are the main commercial applications of enzymes?

Answer 6

28% detergents 35% food processing 23% beverages

Question 7

Give some examples of the formation and breakages of bonds that uses enzymes?

Answer 7

glycosidic bondsester bonds peptide bonds

Question 8

Name 4 processes that use a range of different enzymes

Answer 8

respiration photosynthesisdigestion and protein synthesis

Question 9

What does a substrate become when it is catalysed by an enzyme? and give an example

Answer 9

a producteg if you use the enzyme maltase to catalyse the conversion of maltose into glucose, then the substrate maltose is converted into glucose (the product)

Question 10

What is the usually format for naming a specific substrate?

Answer 10

its usually derived from the substrate of the reaction that is catalysed with the suffix -ase

Question 11

Describe the reaction catalysed by the enyzyme lactase

Answer 11

The break down of milk sugar, lactose into glucose and galactose monomers.

Question 12

What makes lactose-intolerants, intolerant to lactose and what are the effects.

Answer 12

They do not produce lactase and it causes them to suffer stomach cramps, bloating and diarrhoea

Question 13

Describe the reaction catalysed by the enyzyme catalase

Answer 13

The breakdown of hydrogen peroxide to water and oxygen gas. Almost all organisms produce catalase brcause hydrogen peroxide is a toxic by-product of some metabolic reactions

Question 14

Describe the reaction catalysed by the enyzyme Ribulose biphosphate carboxylase (rubisco).

Answer 14

Plants need carbon dioxide for photosynthesis. The enzyme rubisco catalyses the binding of carbon dioxide to a molecule called ribulose bisphosphate.

Question 15

Describe the reaction catalysed by the enyzyme ATP-ase.

Answer 15

The break down of ATP to produce ADP and a phosphate group. This reaction releases a small amount of energy that is used to drive energy requiring processes such as active transport

Question 16

Describe the reaction catalysed by the enyzyme glycogen synthetase

Answer 16

The building up of glycogen of catalysing the joining together of glucose molecules. Glycogen is the storage carbohydrate of animals.

Question 17

What are the weaknesses of enzymes?

Answer 17

The same as protein weaknesses, their shape must remain in tact

Question 18

What can endothermic animals do?

Answer 18

maintain their internal body temperature independently of the environment, allowing them to live in so many enviroments all around the world

Question 19

How does it help by regulating body temperatures in endothermic animals?

Answer 19

As it means that enzymes can function at a near optimum temperature

Question 20

What is the advantage and disadvantage to regulating body temperatures in endothermic animals?

Answer 20

It has allowed mammals to live successfully on land and water.It requires alot of energy so mammals and birds require a lot more food than a similarly size reptile.

Question 21

What is a heterotroph?

Answer 21

an organism that obtains its nutrients by consuming other organisms, that need to break down the body of organisms they are consuming in order to extract the nutrient molecules they need for their own growth and energy requirements.

Question 22

Name 3 bonds that must be broken down during digestion.

Answer 22

esterpeptide glyosidic

Question 23

`Describe the two methods of digestion

Answer 23

-Some organisms secrete enzymes out of them and then the enzymes digest molecules into their monomers, which the organism then takes in and uses - Others have internal digestive systems, that mixes enzymes with the food as it is digested (many of these enzymes are extracellular)

Question 24

What does extracellular mean?

Answer 24

enzymes catalyse reactions outside the cell

Question 25

What does intracellular mean?

Answer 25

Enzymes catalyse reactions inside the molecule

Question 26

What does mould produce to digest bread?

Answer 26

extracellular enzymes

Question 27

are enzymes just used simply as a catalyst?

Answer 27

no, they are often used as defensive mechanisms.

Question 28

Give an example of a white blood cell that use enzymes for digestion

Answer 28

phagocytes, they take in and digest bacteria using lysosomal enzymes

Question 29

How do white blood cells engulf bacterial cells?

Answer 29

An endocytosed vesicle is fused with one of the many lysosomes present and lysosomal enzymes digest the bacterium. (phagocytosis)

Question 30

What is activation energy?

Answer 30

The amount of energy that must be applied for a reaction to proceed.

Question 31

How do enzymes affect the activation energy needed?

Answer 31

They reduce it

Question 32

Is the amount of activation energy required, the same for each enzyme?

Answer 32

no, it varies

Question 33

Use maltose as an example of how enzymes break down molecules

Answer 33

The glycosidic bond must be broken and a water molecule must be split at the same time, this happens when maltose is boiled with an acid which provides the right conditions for maltose molecules to collide with water molecules ‘energetically’ enough to achieve hydrolysis (the activation energy)

Question 34

How do enzymes help a cell function?

Answer 34

they reduce the amount of activation energy needed, so reactions can proceed quickly at temperatures much lower than boiling point. (They can do this because of the way the active site is shaped to fit the substrate molecule/s)As these reactions would need a lot more energy without the enzyme

Question 35

What role does the substrate play?

Answer 35

substrates are where the reaction occurs, eg maltose may enter an enzyme, and two glucose molecules would leave as the products

Question 36

Name 2 ways its thought that enzymes work

Answer 36

lock and key induced fit theory

Question 37

Describe the lock and key theory.

Answer 37

The substrate ‘key’ fits into the active site ‘lock’. The substrate is then held in one place so the reaction can go ahead.

Question 38

Describe the induced fit theory

Answer 38

As the substrate molecule collides with the AS, the enzyme changes shape slightly which makes the active site fit more closely round the molecule and is held in place because of the opposite charges of the substrate and the active site (an enzyme-substrate complex) - This change in shape places a strain on the substrate, destabalising the molecule so the reaction occurs more easily. This produces a produce (known as the enzyme-product substrate) that is a different shape to the original substrate so no longer fits the active site.

Question 39

What is the product of an enzyme reaction called?

Answer 39

a substrate-product complex

Question 40

How does kinetic energy affect an enzyme

Answer 40

As it increases the amount of random collisions, and they collide with greater speed, and therefore greater force

Question 41

What happens to bonds when heat is applied to a solution?

Answer 41

the vibrations of the molecules put a strain of the molecules, it could even denature some structures, reducing reaction rates.

Question 42

What is denaturation?

Answer 42

the changes to the tertiary structure of an enzyme so it cannot function and its function cannot be restored (but it does not change the primary structure of an enzyme/protein ie peptide bonds arent broken)

Question 43

What happens to the rate of reaction if heat is added?

Answer 43

it will increase until the optimum rate of reaction, and after this point it reduces due to an increase in the amount of enzymes being denatured

Question 44

How do you measure the effect of temperature on enzyme action?

Answer 44

carry out enzyme controlled reactions at different temperatures , using a waterbath controlled by a thermostat, and you can measure the production of product or the disappearance of substrate in various ways (in detail later)

Question 45

What is the average range for optimum temperatures of enzymes?

Answer 45

40-50

Question 46

What is a polymerase chain reaction?

Answer 46

where heat resistant enzymes are used to catalyse reactions involved in making many copies of DNA segments (very similar to DNA replication) which is used in modern genetic engineering.

Question 47

What is pH?

Answer 47

the measure of the hydrogen concentration, with values ranging from 1-14 (1=acid, 14=alkaline)

Question 48

Do acids have a low or high concentration of H+?

Answer 48

high, the higher the concentration of hydrogen, the lower its found on the pH scale.

Question 49

What is an acid defined as in chemical terms?

Answer 49

a proton doner as hydrogen ions are also known as protons.

Question 50

Why do hydrogen bonds hold together tertiary structures?

Answer 50

As they are attracted to the negative groups on the amino acids.

Question 51

Why does the concentration of hydrogen bonds(pH) affect the tertiary structure of an enzyme molecule? What else can it affect?

Answer 51

As hydrogen ions can interfere with the hydrogen and ionic bonds that hold the tertiary structure together,also affects the shape of the active site, so can also affect the rate of enzyme controlled reactions

Question 52

How does increasing the concentration of hydrogen affect the charges round the active site?

Answer 52

As more hydrogen ions are attracted towards any negatively charged groups in the active site.

Question 53

What is the most common optimum pH level for enzymes? Why is it optimum?

Answer 53

pH 7, as it gives the tertiary structure of the enzyme the best overall shape to hold the substrate in place.

Question 54

Is the pH range for an enzyme quite broad or narrow?

Answer 54

narrow

Question 55

How is the effect of pH on an enzyme measured?

Answer 55

You carry out enzyme-controlled reactions at different pH values using buffering solutions, and the production of a product or the disappearance of a substrate can be measured in a variety of ways (seen later)

Question 56

Give examples of enzymes working at different pHs in the human digestive system

Answer 56

In the stomache, the protein digesting enzyme pepsin works at an optimum pH level of 2But then trypsin, the protein digesting enzyme in the small intestine works best at pH7

Question 57

What happens as you increase the concentration of substrates/

Answer 57

collisions between enzymes and substrate molecules occur more often , so more enzyme-substrate complexes occur

Question 58

Describe what happens at the maximum reaction rate

Answer 58

all the enzymes present are forming enzyme substrate complexes as fast as possible, so it cannot increase any further (meaning an increase in substrate will no longer have any effect)

Question 59

How do you increase the rate of reaction?

Answer 59

adding both more substrates and enzymes

Question 60

If you mixed enzymes and substrates once, and did not add anything to the solution once the reaction has begun, why would the rate of reaction increase, and then eventually decrease again?

Answer 60

As the substrate is slowly being used up, so its concentration is decreasing, while the concentration of enzymes remains the same and the concentration of products increases.

Question 61

What is the initial rate of reaction?

Answer 61

The highest reaction rate, which gives the maximum possible reaction rate for an enzyme under a particular experimental situation

Question 62

When is a factor described as a limiting factor/

Answer 62

if there is a situation where, if all other conditions kept constant, increasing the concentration of that factor alone will increase the reaction rate

Question 63

What is the plateau of a graph and why does it occur in graphs of increasing the enzyme/substrate concentration?

Answer 63

the leveling off of the graphoccurs as the level of the molecule remaining constant prevents any further increase in the reaction rate.

Question 64

What happens if the concentration of the limiting factor is increased?

Answer 64

then the reaction rate increases

Question 65

Why are enzyme concentrations often quite low in cells

Answer 65

As they are catalysts so they work over and over again, driving the same reaction.