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a-level biology > 2.1.4 Enzymes and Chromatography > Flashcards

2.1.4 Enzymes and Chromatography Flashcards

1
Q

types of metabolic reactions

A

anabolic and catabolic

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2
Q

anabolic reaction

A

building up/synthesis

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3
Q

catabolic reaction

A

breaking down/degradative

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4
Q

examples of anabolic reactions

A

protein synthesis, photosynthesis

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5
Q

examples of catabolic reactions

A

respiration, digestion

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6
Q

general enzyme equation

A

enzyme + substrate <-> enzyme substrate complex <-> enzyme product complex <-> enzyme + products

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7
Q

biological catalyst

A

biological - proteins used in metabolism

catalyst - a chemical that speeds up rate of reaction, lowering the activation energy

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8
Q

residues directly involved in enzyme action

A

contact residues and catalytic residues

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9
Q

contact residues

A

bind to the substrate, determines specificity

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10
Q

catalytic residues

A

act on the bonds within the substrate that are broken by enzyme action

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11
Q

types of inhibitors

A

competitive and non-competitive

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12
Q

denatured enzymes

A

permanent change in tertiary and secondary structure

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13
Q

types of cofactors

A

prosthetic groups, inorganic ions, coenzymes

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14
Q

factors that denature enzymes

A

high temperatures or extreme pH

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15
Q

cofactor

A

any substance which is essential for efficient functioning of an enzyme

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16
Q

types of cofactors

A

prosthetic group
inorganic ions
coenzymes - organic

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17
Q

features of a prosthetic group

A

non-protein part of an enzyme, very tightly bound on a permanent basis (usually metal ions)

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18
Q

examples of prosthetic group

A

haem group (Fe2+)
zinc (Zn2+) - carbonic anhydrase

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19
Q

features of inorganic ions

A

not permanently bound but may bind temporarily to an enzyme or substrate

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20
Q

example of an inorganic ion

A

Cl- for amylase

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21
Q

features of coenzyme

A

often vitamins, bind to active site temporarily or at the same time as the substrate, carry chemical groups between enzymes eg. e-

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22
Q

examples of coenzyme

A

NAD, FAD, both derived from vitamin B, involved in respiration

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23
Q

metabolic pathways

A

series of consecutive reactions, every step catalysed by a specific enzyme that produces a specific product

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24
Q

intracellular enzymes

A

catalyse reactions inside the cell

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25
example of intracellular enzyme
**catalase:** breaks down hydrogen peroxide into water and oxygen
26
primary structure of an enzyme
sequence of amino acids joined by peptide bonds
27
secondary structure of an enzyme
folding of the amino acid chain into **alpha helices** or **beta-pleated sheets** held together by **hydrogen bonds**
28
tertiary stucture of an enzyme
3D folding of secondary structure into a specific shape held together by hydrogen bonds, hydrophobic/hydrophilic interactions, ionic bonds, disulfide bonds
29
quarternary structure of an enzyme
occurs in proteins that have more than one polypeptide chain working together as a functional macromolecule
30
respiratory enzymes
responsible for the breakdown of glucose and the formation of ATP
31
extracellular enzymes
catalyse reactions **outside** the cell
32
phosphorylases
act in cytoplasm add phosphate groups e.g. glucose is phosphorylated to keep in cell + makes it more reactive
33
decarboxylases
act in matrix of mitochondria removes carbon dioxide
34
dehydrogenases
act in matrix of mitochondria removes hydrogen
35
digestive enzymes
carbohydrase - e.g. amylase protease - e.g. pepsin lipase - e.g. lipase
36
carbohydrase substrate molecule
carbohydrates starch
37
protease substrate molecule
protein
38
lipase substrate molecule
lipids
39
bonds that carbohydrases break
glycosidic bonds
40
bonds that proteases break
peptide bonds
41
bonds that lipases break
ester bonds
42
site of production and action of carbohydrases
salivary glands mouth
43
site of production and action of proteases
stomach
44
site of production and action of lipases
produced in pancreas act in small intestine
45
lock and key hypothesis
1. substrate arrives + **randomly** collides with the active site 2. substrate fits into the active site - **complementary** binding, forms temporary bonds 3. products leave the active site
46
what does the induced fit model suggest
the presence of the substrate induces a shape change in the active site fo the enzyme gives a good fit
47
the induced fit model
1. initial complementary binding of substrate and active site 2. temporary bonds form 3. conformation in the enzyme structure - enzyme changes shape 4. catalytic R groups interact with substrate and reaction occurs 5. products are released
48
activation energy
the minimum amount of energy required to reach the transition state of a reaction
49
how do enzymes lower activation energy
catalytic R groups may donate or accept e-, forms bonds with substrate - helps substrate reach transition state enzyme may create a particular environment by enclosing substrate on binding, bonds in substrate may be strained - helps molecules reach transition state enzymes orientate molecules so reacting bonds are closer to each other
50
factors that affect the rate of enzyme controlled reactions
enzyme concentration substrate concentration temperature pH
51
effect of enzyme concentration on rate
increasing enzyme conc. increases rate **more active sites** are available increased **frequency** of successful collisions (enzyme + substrate) increased number of **enzyme - substrate complexes** more products formed **per second** increased initial rate
52
effect of enzyme concentration, limited substrate, on rate
graph flattens/plateaus substrate is a **limiting factor** if enzyme conc. increased further, rate would not increase **not all active sites are occupied** by substrate VMax is reached
53
effect of substrate concentration on rate
increasing substrate conc. increases rate increased **frequency** of successful collisions increased number of **enzyme - substrate complexes** more products formed **per second** increased initial rate
54
effect of substrate concentration, fixed enzyme concentration, on rate
rate **plateaus** rate is prevented from increasing further enzyme reached its VMax **every active site is occupied**
55
effect of low temperature on rate
enzyme is **unactivated** less KE = move slowly and not frequently low frequency of successful collisions less product formed per second low initial rate
56
effect of increasing tempertaure on rate
**KE increases** = move quicker, more frequently **increased frequency** of successful collisions more enzyme - substrate complexes increased initial rate
57
effect of optimum temperature on rate
enzyme reaches VMax highest initial rate
58
effect of temperature above optimum temp on rate
initally enzyme **begins to change shape** = decreased frequency of successful collisions more vibrations = **more H/ionic bonds broken** loss of secondary and tertiary structure **active site changes shape** = no longer complementary **no enzyme - substrate complexes formed** enzyme is denatured = function cannot be restored
59
effect of small changes of pH on rate
decrease rates shape of active site is disrupted, not denatured
60
effect of extreme changes from optimum pH on rate
enzyme is denatured rate = 0
61
effect of extreme low pH on rate
acids = H+ donors H+ ions attracted to negatively charged parts of molecule excess H+ interferes with hydrogen/ionic bonds - can cause secondary and teritary structure to unravel active site changes shape substrate molecule no longer complementary
62
buffer
a solution which resists changes in pH when small amounts of acids or alkalis are added
63
enzyme inhibitors
reduce the rate of enzyme controlled reactions have an effect on the enzyme may block the active site, change active site shape, stop it from catalysing the reaction
64
competitive inhibitors
similar shape to substrate binds to active site of an enzyme = enzyme - inhibitor complex competes with substrate for active site prevents the substrate from binding mostly reversible
65
example of competitive inhibitor
statins = competitive inhibitor of enzyme HMG-coA reductase (makes cholesterol in liver) treates people with coronary heart disease - reduces fatty deposits in arteries
66
non-competitive inhibitor
binds to allosteric site no structural similarity to substrate binding causes active site shape to distort - comfromational change in tertiary structure = substrate no longer complementary to active site
67
example of non-competitive inhibitor
cyanide is a non-competitive inhibitor of respiratory enzyme (cytochrome oxidase) prevents the formation of ATP
68
reversible inhibitors
most competitive inhibitors do not bind permanently removal of inihibitor from a reaction mixture leaves enzyme molecule unaffected
69
irreversible inhibitors
most non-competitive inhibitors bind permanently to enzyme molecules any molecules bound by inhibitor are inactivated

a-level biology (26 decks)

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