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Biology > Chapter 4 - Enzymes > Flashcards

Chapter 4 - Enzymes Flashcards

1
Q

State the definition of enzymes

A

They are biological catalyst that interact with substrate molecules to facilitate chemical reactions

They lower the activation energy of a specific chemical reaction by helping

Globular proteins

They are highly specific bc only catalyse one reaction

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2
Q

Definition of a catalyst

A

A chemical that speeds up the rate of reaction and remains unchanged and reusable at end

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3
Q

Describe the steps to the formation of an enzyme and a product

and in terms of bonds

A

Enzyme + substrate
Enzyme-substrate complex
Enzyme-product complex
Enzyme + product

Substrate is held in such a way right atom groups are close enough to react

R-groups within the active s. of enzymes will also interact w substrate

Forms temporary bonds

Put strains on bonds within substrate (helps reaction occur)

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4
Q

Describe the role of enzymes reactions

A

In some chemical reactions a high temperature or pressure is needed, in the body it is not possible

Hence enzymes lower the activation energy and speeds up r of r so reactions can take place without having these conditions.

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5
Q

What is an anabolic reaction?

A

Reaction that constructs molecules from smaller units

involved in growth

The enzyme catalyses this reaction, requires energy

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6
Q

Suggest the roles of enzymes in organisms

A

Enzymes help catalyse the catabolic reactions (break down of molecules e.g. food) to release energy

Break down of glucose for energy

Involved in the metabolic pathway

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7
Q

Why are enzymes important for organisms

A

Don’t produce unwanted by products & rarely make mistakes

Break down of glucose for energy

Involved in the metabolic pathway

Body can regulate the enzymes to fit need

More specific than chemical catalysts

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8
Q

What is Vmax?

A

The maximum initial velocity/rate of the enzyme catalysed reaction

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9
Q

What is Vmax?

A

The maximum initial velocity/rate of the enzyme catalysed reaction

When the enzymes are working at its fastest, all active sites are occupied by substrate molecule (only way to incr r of r would be to incr enzyme conc)

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10
Q

What happens in the induced fit hypothesis?

A

Substrate and R-groups form weak interactions (only H+ bonds, ionic attractions)

They induce changes in the tertiary structure in enzymes

Enzyme moulds around substrate

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11
Q

What is catalase?

A

An enzyme that catalyses the reaction of hydrogen peroxide (which is toxic) to oxygen and water

4 ppc and haem group

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12
Q

Where is catalase stored in organisms?

A

Vesicles called peroxisomes, they are stored there bc they can be released easily when needed

also in separate bubbles

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13
Q

What are extracellular enzymes?

A

Enzymes are secreted by cell

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14
Q

Give a human example of an extracellular enzyme

A

Amylase
- produced in salivary / pancreas glands, acts in mouth

-polysaccharides starch into maltose

Trypsin (type of protease)
- Made in pancreas

  • Acts in lumen of the small the small intestine
  • Digest proteins into smaller peptides by hydrolysing peptide bond
  • Peptide broken down into aa by other proteases
  • op pH 7.5
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15
Q

Describe the steps involved in the digestion of starch in humans

A
  1. Begins in mouth, amylase
    Starch –> maltose
  2. maltase
    maltose –> glucose (monosaccharide)
  3. Glucose small enough to fit/absorbed by cells into blood cells
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16
Q

Describe and explain the effect of a temperature increase on the rate of enzyme activity?

A

Increases

  1. Increase in KE of the particles
    • particles move faster so collide more frequently
    • more successful collisions
  4. More enzyme substrate complexes formed
  5. Increase in rate of reaction
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17
Q

Suggest why after 37 deg the rate of reaction decreases

A

Denatured

  1. KE increases
  2. Bonds holding proteins tertiary structure in place vibrate more and eventually brake
  3. Change in tertiary structure of protein changes active site shape (denatured)
    • substrates can’t fit in the active site and less enzyme substrate complex formed
  5. Slower reaction
18
Q

What is the temperature co-efficient?1

A

Q10 - a measure of how much the r of r increases every 10 deg

19
Q

What is the effect of a lower pH on rate of reaction of enzyme?

A

Decreases

  1. Decrease of conc means more H+ ions as becomes more acidic
  2. H+ ions interact w polar and charged R-groups
  3. Disrupting H+ bonding and ionic bonds that hold the tertiary st. in place
  4. Change in tertiar. s. changes active site on enzyme, enzyme denatured
20
Q

Which factor affecting r of r can be reversed (to an extent)

A

pH change, if pH returns to optimum the protein will resume its normal shape

21
Q

What is the effect of an increase in substrate concentration?

A

Generally increases

  1. Higher frequency of successful collisions btwn enzyme and sub
  2. More enzyme substrate complexes formed
  3. Increased r of r

Plateaus

22
Q

As time increases the r of r ……

A

Decreases

- Conc of available substrates decr as is used up

23
Q

Describe the effect of an increased enzyme concentration on the rate of reaction

A

Increases + plateau

  1. More active sites available
  2. More enzyme substrate complexes formed
24
Q

Why does the graph of increased enzyme conc plateau?

A

Bc there are no more substrates to catalyse.

only way to by pass Vmax is by adding more substrate

25
Q

Define a cofactor

A

A substance that has to be present to ensure that an enzyme catalysed reaction takes place at an appropriate rate

26
Q

What is a coenzyme?

A

Enzyme + non-protein
A type of cofactor that binds temporarily to the active site either just before or at same time the substrate binds

-Conjugated protein w non-protein group associated with it

27
Q

Give an example of a protein that has a prosthetic group

A

Carbonic anhydrase, Zn2+ permanently bound to its active site

-Found in erythrocytes and catalyses the interconversion of CO2 and H20 to carbonic acid

Which then breaks down to protons and hydro-carbonate ions

  • Important bc enables CO2 to be carried in the blood from respiring tissue in the lungs
28
Q

Give an example of a temporary cofactor

A

Cl- in amylase

29
Q

How do co-substrates work

A

Some co-factors act as co-substrates, they and the substrate bind and together form the right shape to bind to AS

30
Q

How do some co-factors make enzyme-substrate complexes easier to form?

A

Some co-factors change the charge distribution on the surface of substrate mol. or enzyme mol. AS

make temporary bonds making enzyme-sub easier to form

31
Q

What happens to coenzymes during a reaction?

A

Chemically changed and need to be recycled to their OG state

32
Q

What are sources of coenzymes

A

Vitamins (e.g. B12)

33
Q

What is a competitive inhibitor? and an example

A

Substances whose molecules have a similar shape to an enzymes substrate molecules

Statins used in synthesis of cholesterol

34
Q

What is the mechanism behind competitive inhibitors?

A
  1. The inhibitor has a similar shape to the substrate of an enzyme
  2. Inhibitor fits into the AS, preventing the substrate to bind to form enzyme-substrate complex
  3. Reducing the n. of free enzyme AS available
35
Q

What ‘dilutes’/ opposes the effect of competitive inhibitors?

A

Increasing the substrate concentration

36
Q

What is an inactivator? and example

A

When the competitive inhibitor binds irreversibly to AS (aspirin)

37
Q

What is a non-competitive inhibitor?

A

If the inhibitor binds to somewhere other than the active site

38
Q

Where do non-competitive inhibitors bind to?

A

The allosteric site

39
Q

Explain how non-competitive inhibitors work

A
  1. Inhibitor binds to allosteric site
  2. Binding causes the tertiary structure to change, therefore AS shape changes
  3. AS no longer has COMPLEMENTARY shape to substrate so cannot bind
  4. No ES complex formed
40
Q

How can you oppose the non-competitive inhibitor?

A

Cannot

Because the AS shape is changed

41
Q

What is end-product inhibition?

A

Enzyme inhibition that occurs when the product of a reaction acts as an inhibitor to the enzyme that produces it.

42
Q

What is the advantage of end-product inhibition?

A

No excess or waste products are made, an example of non-competitive reversible inhibition

Biology (15 decks)

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