Enzymes Flashcards

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1
Q

define an enzyme

A

Enzymes are globular proteins that act as catalysts.

they alter the rate of a chemical reaction without undergoing permanent changes themseves.

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2
Q

what is required for reactions like sucrose + water= glucose to take place naturally

A

the sucrose water molecules must collide with sufficient energy to alter the arrangement of their atoms to form glucose and fructose

the free energy of the products must be less than that of the substrates sucrose and water

many reactions require an activation energy

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3
Q

what must happen before a reaction can proceed

A

there is an activaion energy level, like an energy barrier which must initially be overcome before the reaction can proceed

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4
Q

explain how enzymes help reactions proceed

A

enzymes work by lowering this activation energy level

in this way enzymes allow reactions to take place at lower temperature than normal

this enables some metabolic processes to occur rapidly at the human body temperature of 37 degrees Celsius

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5
Q

what would happen without enzymes

A

these reactions would proceed too slowly to sustain life as we know it

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6
Q

what region of the enzyme is functional

A

active site

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7
Q

describe the active site

A

the active site is made up of a relatively small number of amino acids

he active site forms a small depression within the much larger enzyme molecule

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8
Q

what is the molecule on which the enzyme acts called

A

the substrate

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9
Q

explain the role of a substrate

A

fits neatly into this depression and forms an enzyme-substrate complex.

the substrate molecule is held within the active site by bonds that temporarily form between certain amino acids of the active site and group of the substrate molecule

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10
Q

describe the induced fit model of enzyme action

A

the induced fit model of enzyme action proposes that the active site forms as the enzyme and substrate interact

the enzyme is flexible and can mould itself around the substrate

the enzyme has a certain general shape but this alters in the presence of a substrate

As it changes shape, the enzyme puts a strain on the substrate molecule.

the strain distorts particular bonds in the substrate and consequently lowers the activation energy needed to break the bond

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11
Q

explain the induced fit concept

A

any change in an enzymes environment is likely to change its shape.

the very act of colliding with its substrate is a change in its environment and so its shape changes- induced fit

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12
Q

explain the mechanism of enzyme action

A

Substrates collide with the enzyme’s active site and this must happen at the correct orientation and speed in order for a reaction to occur

An enzyme-substrate complex forms when an enzyme and its substrate join together

The enzyme-substrate complex is only formed temporarily before the enzyme catalyzes the reaction and the product(s) are released

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13
Q

explain the specificity of an enzyme

A

The specificity of an enzyme is a result of the complementary nature between the shape of the active site on the enzyme and its substrate(s)

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14
Q

what determines the shape of the active site

A

The shape of the active site (and therefore the specificity of the enzyme) is determined by the complex tertiary structure of the protein that makes up the enzyme

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15
Q

what forms when an enzyme and substrate join together

A

an enzyme-substrate complex

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16
Q

what are the two types of enzyme reactions

A

Enzyme reactions can either be catabolic or anabolic

17
Q

explain catabolic reactions

A

Catabolic reactions involve the breakdown of complex molecules into simpler products, which happens when a single substrate is drawn into the active site and broken apart into two or more distinct molecules (products)

18
Q

give two examples of catabolic reactions

A

cellular respiration and hydrolysis

19
Q

explain anabolic reactions

A

Anabolic reactions involve the building of more complex molecules from simpler ones by drawing two or more substrates into the active site, forming bonds between them and releasing a single product

20
Q

give two examples of anabolic reactions

A

protein synthesis

photosynthesis

21
Q

what type of protein are enzymes

A

globular proteins

22
Q

what can enzymes be

A

Enzymes can be intracellular or extracellular referring to whether they are active inside or outside the cell respectively

23
Q

define intracellular enzymes

A

Intracellular enzymes are produced and function inside the cell

24
Q

define extracellular enzymes

A

Extracellular enzymes are secreted by cells and catalyse reactions outside cells (eg. digestive enzymes in the gut)

25
Q

explain the effect of a rise in temperature on enzyme action

A

a rise in temperature increases the kinetic energy of molecules.

as a result, the molecules move around more rapidly and collide with each other more often

in an enzyme catalysed reaction, this means that the enzyme and substrate molecules come together more often in a given time

there are more effective collisions resulting in more enzyme-substrate complexes being formed and so the rate of reaction increases

26
Q

what happens when the temperature exceeds 37 degrees celsius

A

it causes the hydrogen and other bonds in the enzyme molecule to break

this results in the enzyme, including its active site changing shape, slowing the rate of reaction

27
Q

explain when denaturation occurs and define it

A

usually, around 60 degrees the enzyme is so disrupted that it stops working altogether. it is said to be denatured

denaturation is a permanent change and once it has occurred, the enzyme does not function again

28
Q

why have our bodies evolved to be 37 degrees celsius

A

althougher higher body temperatures would increase te metabolic rate slightly, the advantages are offset by the additional energy that would be needed to maintain the higher temperature

other proteins, apart from enzymes, may be denatured at higher temperatures

at higher temperatures any further rise in temperature, for example, during illness, might denature the enzymes