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Enzymes Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q
  1. What is an enzyme?
A

A biological catalyst that speeds up metabolic reactions.

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2
Q
  1. What type of molecules are enzymes?
A
  1. What type of molecules are enzymes?
    Enzymes are globular proteins, with a precise 3D shape due to ionic, hydrogen, disulphide bonds and hydrophobic interactions of the tertiary structure.
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3
Q
  1. What is an active site?
A

The portion of the enzyme molecule to which the substrate binds.

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4
Q
  1. What is an anabolic reaction?
A

Anabolism is the building up of molecules.

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5
Q
  1. What is a catabolic reaction?
A

Catabolism is the breakdown of molecules

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6
Q
  1. What is activation energy?
A

Activation energy is the amount of energy needed to initiate a reaction

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7
Q
  1. What effect do enzymes have on activation enzymes of a reaction
A

Enzymes lower the activation energy

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8
Q
  1. What is the benefit to living organisms of having enzymes?
A

Enzymes allow reactions to take place at body temperature at the rapid rate necessary to sustain life.

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9
Q
  1. Describe how an enzyme works in a catabolic reaction (breaking larger molecules down into their smaller sub-units)
A
  • Substrate collides with enzyme and fits into the active site forming an enzyme-substrate complex. * The bonds with the substrate are strained lowering the activation energy and forming the product. * The product does not fit into the active site and is released from the enzyme. * The enzyme can be reused
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10
Q
  1. What does the term, “enzyme specificity”, mean?
A

Each enzyme is specific to a particular substrate. Only one substrate is the exact complementary shape to the active site

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11
Q
  1. What is the “lock and key hypothesis”?
A

The enzyme active site is an exact match to the shape of the substrate, they are complementary to each other

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12
Q
  1. What is the “induced fit hypothesis”?
A

The active site moulds around the substrate forming a precise fit

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13
Q
  1. What is a co-factor?
A

Anon-protein substance that an enzyme may require to function. some are permanently attached)

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14
Q
  1. Name some examples of cofactors
A

Metal ions e.g. Chloride ion in salivary amylase Prosthetic groups e.g. haem group in catalase

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15
Q
  1. What is a co-enzyme?
A

Co-enzymes are non-protein, organic molecules necessary for enzyme action (never permanently attached to the enzyme.)

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16
Q
  1. Give some examples of coenzymes?
A

NAD and FAD are co-enzymes in respiration.

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17
Q
  1. Describe how an inhibitor can be used as a therapeutic drug.
A

Enzyme inhibitors can be used to reduce or stop the progression of the disease by targeting the enzymes involved in causing diseases.

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18
Q
  1. What characteristics must enzyme inhibitors have to work as therapeutic drugs?
A
  • Specific to the enzyme in the disease progression. * Work well at low dosage to prevent toxic build up of inhibitor.
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19
Q
  1. Give examples of inhibitors being used as therapeutic drugs.
A
  • Penicillin inhibits enzyme responsible for the formation of cross links in bacterial walls. * ACE (Angiotensin Converting Enzyme) inhibitors prevent vasocontraction of coronary arteries, thereby lowering blood pressure * Antiviral drugs inhibit DNA/RNA polymerase, essential in DNA replication.
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20
Q
  1. Describe how an enzyme can be used as a biomarker of disease.
A
  • The presence of an enzyme or the protein it produces can be used as a diagnostic tool to confirm that a particular disease is present in the body. * Monitoring levels of the enzyme can monitor the progression of the disease.
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21
Q
  1. Give an example of an enzyme being used as a biomarker of disease.
A
  • elastase is a biomarker for lung disease. * It is produced by body as part of the immune response to bacterial infection and normally is subsequently stopped by an enzyme inhibitor. * Over production of elastase is common in smokers leading to elastase-induced emphysema. * The elastase breaks down the elastin, reducing the elasticity of lung tissue and the stretch and recoil action of the alveoli.
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22
Q
  1. What are immobilised enzymes?
A

Immobilised enzymes are trapped within, or attached to, appropriate inorganic or organic materials.

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23
Q
  1. Describe the following method of immobilisation: Adsorption
A

The enzymes are attached by weak forces to an inert substance such as glass or a matrix.

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24
Q
  1. Describe the following method of immobilisation: Entrapment
A

The enzymes are trapped within polymers such as alginate beads or microspheres.

25
Q
  1. Describe the following method of immobilisation: Encapsulation (enmeshment)
A

The enzymes are trapped inside a selectively permeable membrane such as nylon.

26
Q
  1. State 5 advantages of enzyme immobilisation
A
  • Increased thermostability * More resistant to change in pH * Retained and reused * Allows continuous flow column reactors (faster and produce less wastage) * End product is enzyme free (simplifying the downstreaming process and reducing purification costs)
26
Q
  1. Describe the following method of immobilisation: Cross-linkage
A

The enzymes are bonded covalently to a matrix, such as cellulose.

27
Q
  1. Describe and explain 4 disadvantages of enzymes immobilisation
A
  1. Enzymes may wash off the material (adsorption) *as weak forces hold them in place. 2. Enzyme active sites are blocked (adsorption, cross-linkage) * therefore the substrate cannot enter some active sites slowing the rate of reaction. 3. Substrate must move through a material to get to the enzyme (encapsulation, entrapment) * reduced speed of diffusion between substrate and enzyme hence a reduced rate of reaction
27
Q
  1. Give examples of immobilised enzymes being used as diagnostic strips as biosensors.
A
  • Clinistix: when glucose is present the enzyme is activated to produce colour change. * Pregnancy tests: when pregnancy hormone attaches to antibody in test strip, this activates the enzyme to produce colour change.
28
Q
  1. What is a biosensor?
A

A device which uses a living organism or biological molecules, especially enzymes or antibodies, to detect the presence of chemicals.

29
Q
  1. Describe how immobilised enzymes can be used in diagnostic reagent strips as a biosensor
A

The molecule being monitored reacts with the immobilised enzymes and this reaction produces a colour change or is converted to an electrical signal for digital display.

30
Q
  1. Why are enzymes very effective as biosensors?
A
  • They are very specific and can be used to identify individual molecules * Quantitative - can measure amount presence
31
Q
  1. Why use an inhibitor rather than the normal substrate?
A

Active-site directed inhibitors are more specific than the normal substrate.

31
Q
  1. Describe how an enzyme inhibitor can be used as a diagnostic reagent strip.
A
  • at can detect the presence of an enzyme. * If the enzyme is present it will bind by its active site to the inhibitor which is attached to the diagnostic strip. Resulting in a positive read out.
32
Q
  1. Give examples of enzyme inhibitors being used in diagnostic reagent strips.
A

Early identification of cardiovascular disorders, preeclampsia and other medical conditions by detection of specific enzymes present in patient samples.

33
Q
  1. Name 4 factors that affect enzyme activity.
A

Temperature, pH, substrate and enzyme concentration all affect the rate of enzyme activity.

34
Q
  1. Which enzyme bonds are broken most at high temperatures?
A

Hydrogen bonds in the tertiary structure break, altering the shape of the active site.

34
Q
  1. Describe how temperature affects enzyme activity.
A

Increasing temperature increases the rate of reaction to a particular point (the optimum temperature) and then further increase in the temperature causes a decrease in the rate of reaction.

35
Q
  1. Sketch the graph for how temperature affects enzyme activity.
A

see notes

36
Q
  1. Explain how temperature affects enzyme activity.
A
  • Increasing temperature increases the kinetic energy of the substrate and enzyme. * They collide more, causing more frequent formation of enzyme-substrate complexes. * At higher temperatures, the increased temperature causes hydrogen bonds of the tertiary structure to break and the shape of the active site changes, the enzyme is denatured. * The substrate is no longer complementary and does not fit into the active site. Hence the rate of enzyme activity decreases. * At very high temperatures all enzymes are denatured hence enzyme activity stops.
37
Q
  1. What is the optimum temperature?
A

The temperature at which the enzyme has the greatest activity (highest rate of reaction).

38
Q
  1. Explain how pH affects enzyme activity.
A

At non optimum pH values, ionic bonds in the tertiary structure are disrupted changing the shape of the active site so fewer enzyme-substrate complexes are formed.

38
Q
  1. How is an enzyme denatured?
A

The hydrogen or ionic bonds in the tertiary structure of an enzyme break. The shape of the active site is permanently changed and is no longer complementary to the substrate. It can no longer catalyse the reaction as the enzyme-substrate complex cannot be formed.

38
Q
  1. Which enzyme bonds break most at non-optimal pH?
A

Ionic bonds in the tertiary structure break, altering the shape of the active site.

39
Q
  1. Sketch the graph for substrate concentration of enzyme activity.
A

see notes

40
Q
  1. Sketch the graph for pH affecting enzyme activity.
A

see notes

41
Q
  1. Explain how substrate concentration affects enzyme activity.
A

Increasing the substrate concentration provides more substrate molecules to fit into the active sites allowing more enzyme-substrate complexes to form. * At higher substrate concentrations the number of active sites becomes limiting as enzyme-substrate complexes form at the maximal rate.

41
Q
  1. Describe how pH affects enzyme activity.
A

The further away from non-optimal pH, the greater the reduction in enzyme activity.

41
Q
  1. Sketch the graph for enzyme concentration of enzyme activity.
A

see notes

42
Q
  1. Describe how substrate concentration affects enzyme activity.
A

Increasing substrate concentration increases the rate of reaction to a particular point, and then further increase in substrate concentration has no further effect on the rate of reaction, it remains unchanged.

43
Q
  1. Describe how enzyme concentration affects enzyme activity.
A

As enzyme concentration is increased the rate of reaction increases to a maximum and further increase in enzyme concentration has no further effect on the rate of the reaction, it remains unchanged. (However, in most living cells the rate of the reaction continues to increase without levelling off at a maximum).

44
Q
  1. Explain how enzyme concentration affects enzyme activity.
A
  • Increasing enzymes concentration provides more active sites and more enzymes-substrate complexes can form, increasing the rate of reaction. * At higher enzyme concentrations, the number of substrate molecules become limiting and no further increase in rate of reaction is seen, as enzyme-substrate complexes form at the maximal rate. * However, in most living systems, the substrate is seldom limiting, and the rate of reaction continues to increase.
45
Q
  1. Is inhibition a temporary effect?
A

Many inhibitors are reversible, though some are irreversible causing permanent damage to the enzyme.

45
Q
  1. What is an allosteric enzyme?
A

An enzyme with a second site where non-substrate molecules can attach

46
Q
  1. What is an enzyme inhibitor?
A

Inhibitors reduce enzyme activity either directly or indirectly affecting the functioning of the active site.

47
Q
  1. What is competitive inhibition?
A

The inhibitor substance competes with the usual substrate for the active site.

48
Q
  1. How can changing substrate concentration help distinguish between competitive and non-competitive inhibition?
A

If the substrate concentration is increased, it can overcome the effect of a competitive inhibitor but will not reduce the effect of a non-competitive inhibitor.

49
Q
  1. What is non-competitive inhibition?
A

The inhibitor attaches itself to a part of the enzyme other than the active site.

50
Q
  1. Sketch a graph of rate of reaction with inhibitors and no inhibitors
A

see notes

Biology (11 decks)

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