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OCR A-level Biology Module 2: Foundations in Biology > Enzymes in Biology > Flashcards

Enzymes in Biology Flashcards

the "biological catalysts" we all know and love... explored in detail!

1
Q

What make enzymes usefull in Organisms?

A
  1. They can speed up rate of metabolic reactions, able to be re-used for future reactions
  2. Small amount can be used to catalyse reactions to form products, from reactions.
  3. Number of reactions enzyme can catalyse reactions per second = Turnover Number
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2
Q

What are Anabolic and Catabolic Reactions!

A
  1. ANABOLIC: Smaller molucles made into a larger molecule (ENDO)
  2. CATABOLIC: Larger molecules brocken down into smaller molecules (EXO)
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3
Q

What makes the shape of enzyme active site crucial?

A
  1. Tertiary structure of enzyme active site must be complamentary to shape of substrate, in order to successfully bind
  2. Therefore, each type of enzyme remains highly specific to its substrate, fitting active site
  3. Hence, changes to active site will significantly alter ability to catalyse reaction, affecting the bionds that hold protiens in place!
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4
Q

What are intracellular enzymes?

A
  • These are enzymes working WITHIN the cell
  • Participates in an enzyme cascade, where products become reactants of next reaction
  • Both Anabolic and Catabolic reactions take place!
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5
Q

Explain and example of Intracellular Enzyme!

A
  • CATALASE!!
  • Fasterst acting enzyme, with turnovernumber of 6 million per second!
  • Found in small vesicles (peroxisomes)
  • Protects cell from damage by breaking down H202 (a toxic by-product of many metabolic reactions) into H20 and O2!
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6
Q

What are extracellular enzymes?

A

These are secreted to work in the bloodstream!

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7
Q

Explain examples of extracellular enzymes!

A
  1. AMYLASE: Secreted by salivary glands, to digest starch polysaccharides into disaccahide maltose!
  2. TRYPSIN: Secreted by pancreas, digesting polypeptides into amino acids (hydrolysing peptide bonds)
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8
Q

How can we describe basic Lock and Key model in basic steps?

A
  1. Enzyme + Substrate (approaches)
  2. Enzyme-Substrate Complex
  3. Enzyme-Product Complex
  4. Enzyme + Product (releases)
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9
Q

How does an enzyme catalyse a reaction?

A
  1. Reactants will need to collide with sufficient energy to undergo a successfull reaction
  2. Hence, enzyme active site will bring molecules closer together, providing a more accessibly reaction plane
  3. So, with enzymes, less energy required to collide and undertake a reaction, LOWERING ACTIVATION ENERGY!
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10
Q

What will lowering activation energy do for Reactants?

A

A greater proportion of molecules with sufficient energy to react upon collision (Boltzmann.D logic…)

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11
Q

How does the Induced Fit Model takem place?

A
  1. Substrate will approach enzyme, via own K.E.
  2. Active site will slighly be changed to fit around substrate, where R groups may be altered to precisly fit substrate
  3. Enzyme-Substrate Complex formed, where non-covalent forces will hold substrate in place.
  4. Reaction catalysed, substrate will diffuse away, active site returns to original shape!
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12
Q

What is a Cofactor?

A
  • This is an Mineral Ion, INORGANIC substance that will TEMPORARILY BIND to enzyme’s allosteric site!
  • This will temporarily change the active site’s shape, increasing the likelyhood of enzyme-substrate complexes to occur!
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13
Q

What is a Coenzyme?

A
  • This are Viatmins, ORGANIC substances that will TEMPORARILY BIND to enzyme’s allosteric site!
  • This will temporarily change the active site’s shape, increasing the likelyhood of enzyme-substrate complexes to occur!
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14
Q

What can Coenzymes and Cofactors do to a substrate?

A

They may add/remove electrons to a substrate to complamentary fit into active site even further!

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15
Q

What is an Apoenzyme and a Holoenzyme?

A
  • APOENZYME = This is an inactive enzyme, which may need a coenzyme to become activated, allowing substrate binding to occur!
  • HOLOENZYME = Entire complex of an activated enzyme, able to catalyse reactions
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16
Q

What is a Conjugate Enzyme and a Prosthetic Group?

A
  • PROSTHETIC GROUP: This is a substance that permanently binds to an enzyme that enables them to form enzyme-substrate complexes
  • CONJUGATE ENZYME: Enzyme containing one or more prosthetic groups
17
Q

Example of Cofactor and Coenzyme in action??

A
  1. Amalyase + Chloride Ion = Ion needed to determine the sahep of active site
  2. Vitamin B12 + Enzyme = Again, for the same purpose!
18
Q

THE COENZYMES DERIVED FROM VITAMINS!

vitamin = coenzyme&raquo_space; deficency symptoms…..

A
  1. Vitamin B12 = Cobalamin Coenzymes&raquo_space; Pernicious Anemia
  2. Folic Acid = Tetrahydrflorate&raquo_space;z Megablastic Anemia
  3. Nicotanamide = NAD&raquo_space; Diarrhoea
  4. Pantothenate = Coenzyme A&raquo_space; Elevated Blood Triglyceride Levels
  5. Thiamine = Thiamine PyroPhosphate&raquo_space; Heart Failure, Paralyisis
19
Q

What is a Buffer Solution??

A
  1. Solution that can resist changes to pH levels
  2. By donating or accepting H+ ions in said solution, keeping same pH levels
20
Q

How does pH affect Reaction Rate of Enzymes from Start to Optimum to beyond?

A
  1. Concentration of H+ ions outside optiumum range can intefere with ionic/hydrogen bonds, changing shape of tertiary structure of A.T!!
  2. Excess H+ ions can also alter charges of A.T., intefering with substrate binding (ES)
  3. Optimal H+ ion conc allows A.T. most complamentary to fit substrate
21
Q

How does temprature affect Reaction Rate of Enzymes from Start to Optimum?

A
  1. Temp Increase = reaction rate increase, as more KE of particles mean more particles with sufficent A.E. to successfully collide
  2. Increase rate of ES complex forming, increase rate of products released
  3. Optiumum = most ES Complexes formed per unit time, active site most complamentay to substrate
22
Q

How does temprature affect Reaction Rate of Enzymes from beyond Optiumum?

A
  1. Further from Optiumum = Decreased rate, as A.T. no longer complamentary fits to substrate
  2. Alter in A.T. 3D tertiary shape, as hydrogen bonds brocken causes shape to unfold!
23
Q

What is Temprature Coefficient?

LOOOOK HEREEEEE…..

A
  • The value refering to the rate of increase of reaction rate, per 10’C!
  • Reaction Rate at T+10’C / Reaction rate at T’C!

< 1 = decreasing rate of reaction!
> 1 = Increasing rate of reaction!!

24
Q

How does substrate conc affect Reaction Rate of Enzymes from Start to Optimum?

A
  1. Conc increase = raection rate increase
  2. Greater substrate and A.T. availability to form ES complexes
  3. Occurs until maximum rate, as now enzyme conc becomes limiting factor!
25
Q

How does enzyme conc affect Reaction Rate of Enzymes from Start to Optimum?

A
  1. Conc increase = raection rate increase
  2. Greater A.T. availability to undergo more frequent and successfull collisions, forming ES complexes
  3. Occurs until maximum rate, as now substrate conc becomes limiting factor!
26
Q

What is Competative Inhibition?

A
  • This is where inhibitor molecule has complamentary shape to A.T and similar shape to substrate
  • This will bind to enzyme AT, preventing substrate from doing so
  • Prevents formation of ES complexes, and product released!

“COMPETES” for enzyme AT!

27
Q

What is Non-Competative Inhibition?

A
  • inhibitor molecule will bind to allosteric site of enzyme
  • Will change 3D AT tertiary structure shape of enzyme, unable to bind to substrate
  • AT no longer complamentary to substrate, meaning no more ES complexes + no more product
28
Q

Describe inhibition in Enzyme Cascades!

A
  1. Here, final product of enzyme cascade can bind to allosteric site of enzyme, being non-competative end-product inhibition
  2. End product at high conc = able to inhibit cascade, preventing more ES complexes and product to be formed
  3. Hence, end-product conc will eventually decrease, less inhibition = more products made!

GREAT EXAMPLE OF NEGATIVE FEEDBACK! (responds when conditions change from the ideal condition and returns conditions to this set point)

29
Q

Describe “substrate concentration” graph of Competative Inhibitor!

A
  • Initial RoR = slower
  • As inhibitors bind to enzyme AT preventing ES complexes to form, fewer products formed per unit time
  • Plateu at same place as normal enzyme
  • substrate conc ins highest, outcompeting inhibitors, so now substrate able to bind to AT = more ES complexes able to form as before!
30
Q

Describe “substrate concentration” graph of Non-Competative Inhibitor!

A
  • Initial RoR = Very much slower
  • As inhibitors bind to allosteric site maximum RoR will ALWAYS be lower than initial, very fewer products formed per unit time
  • Plateu much beloew normal enzyme
  • substrate conc highest, but AT 3D tertiary structure shape will be changed, meaning AT no longer complamentary to substrate, meaning high sub conc will not bind to AT any longer
31
Q

How can Competative Inhibition be reversible?

A
  1. Increasing substrate conc = greater substrate availability
  2. Greater chance for AT to collide and bind with substrate molecule than inhibitor!
  3. ES complexes now able to form, and product!
    NON REVERSIBLE INHIBITOR = INACTIVATOR!
32
Q

Benefits of inhibition in Enzyme Cascades!

A
  1. More energy efficient
  2. Prevents unneeded product to be produced
33
Q

What are some examples of enzyme inhibitors as form of CHEMICALS?

A
  1. Cyanide = inhbits aerobic respiration
  2. Snake venom = inhibits neurotransmission
  3. Aspirin = inhibts prostaglandin production (causes sensitivity to pain and swelling)

OCR A-level Biology Module 2: Foundations in Biology (6 decks)

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