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Separate Biology > 12.2 Proteins and Enzymes > Flashcards

12.2 Proteins and Enzymes Flashcards

1
Q

biology is the study of what

A

proteins and shapes fitting together

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2
Q

what elements do all amino acids and proteins contain

A

nitrogen, carbon, hydrogen, oxygen - some contain sulphur

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3
Q

what is special about proteins

A

different specific shape which allows different specific role / function

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4
Q

monomers of proteins

A

amino acids

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5
Q

how many types of amino acids are there

A

20 different types with same general structure linked by peptide bonds

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6
Q

protein structure

A

a carboxyl group, an amine group and a side chain

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7
Q

R groups can be…

A

positively charged
negatively charged
hydrophilic
hydrophobic

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8
Q

what do 2 amino acids join to form

A

dipeptide by condensation

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9
Q

what happens when 2 amino acids are condensed

A

water is removed and a peptide bond is formed

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10
Q

what do hundreds of amino acids join to form

A

a polypeptide chain

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11
Q

what are the 4 levels of protein structure

A

primary structure
secondary structure
tertiary structure
quaternary structure

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12
Q

primary structure of protein

A
  • the number and sequence of amino acids in a polypeptide chain
  • only involves peptide bonds
  • responsible for overall structure of protein
  • changing 1 amino acids might alter the structure / function of the protein
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13
Q

secondary structure of protein

A
  • basic level of protein folding
  • polypeptide chain either folds or coils
  • alpha helix (coils)
  • beta pleated sheet (zigzag)
  • held together by weak H bonds only (between OH groups)
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14
Q

tertiary structure of protein

A
  • folds into a specific complex 3D shape
  • r group determines the specific 3D shape
  • shape held together by bonds between r groups
  • globular proteins
  • 3 types of bonds between r groups
    1 weak H bonds (OH)
    2 ionic bonds weak (R)
    3 disulphide bridges strong (S)
    specific structure -> specific shape -> specific function
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15
Q

globular protein examples

A

haemoglobin
hormones
enzymes

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16
Q

function and factor (what can it do) of globular proteins

A

transport protein
compact and folded into spherical molecules -> soluble in water

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17
Q

quaternary structure of protein

A
  • 2 or more polypeptide chains joined together
  • haemoglobin 4 polypeptide chains
  • collagen 3 polypeptide chains
  • specific shape -> function
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18
Q

structural protein examples

A

keratin
collagen
actin + myosin

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19
Q

denaturation meaning

A

a permanent change to the specific 3D tertiary structure of a protein

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20
Q

when do proteins denature

A

at high temp and changes to the pH

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21
Q

denaturation process

A
  • increase temp -> increases KE -> vibration -> breaks weak H bonds in 2nd + 3rd structure
  • changing pH of environment -> breaks ionic bonds between R groups in 3rd structure
  • binds break -> specific tertiary shape is lost
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22
Q

biuret test for proteins (detects the peptide bonds)

A
  • place small volume of extract in a labelled test tube
  • add 2cm3 of biuret solution
  • positive blue to purple / violet
  • negative stays blue
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23
Q

what are enzymes

A

globular proteins (dissolve in water / soluble) and act as biological catalysts

24
Q

what does a catalyst do

A

increases the rate at which chemical reactions occur but remain unchanged or are unaffected by the reaction (take part but not used up)

25
initial bond breaking requires...
activation energy
26
what is activation energy
the minimum energy required for a successful chemical reaction
27
what do enzymes do to a chemical reaction
increase the rate of reaction by lowering the activation energy needed for a chemical reaction
28
how do enzymes increase the rate of reaction
stressing / distorting / weakening the bonds in the substrate during the formation of an enzyme-substrate complex
29
what does enzymes increasing the rate of reaction allow
allows reactions that would normally require high temperatures to work at lower temperatures
30
enzyme structure
- have active sites - proteins with a specific tertiary structure - active site is specifically complementary to their substrate/s which allows the substrate to bind to the enzymes active site forming an ESC by distorting / stressing the substrates bonds and lowering the Ea.
31
active sites are typically made up of...
less than 10 amino acid R groups
32
induced fit model
- the active site is not fixed / rigid - the active site can change its shape (slightly flexible) - when the substrate binds to the active site (when its aligned correctly), the substrate induces a change in the shape of the active site making it more complementary - the enzyme can alter its tertiary structure when the complementary substrate binds to the active site
33
steps of the induced fit model
- the substrate enters the enzymes active site and binds to it forming the enzyme-substrate complex - the binding of the substrates molecules induces a change in the shape of the active site - the slight change in shape of the specific 3D tertiary structure of the active site applies stress or distorts the bonds within the substrates molecules which lowers the AE of the reaction - when the substrate leaves the active site returns to its original shape
34
what factors affect enzyme action
- temperature - pH - substrate concentration - enzyme concentration - concentration of competitive inhibitor - concentration of non-competitive inhibitor
35
describe how temp affects enzyme action
- rate is low when temp is low - rate increases as temp increases up to the optimum - reaction rate highest at optimum temp - reaction rate falls quickly as temp increase above the optimum temp - reaction rate lowest at high temp
36
why does temp affect enzyme action
- little KE few successful collisions few ESC - KE increases more faster more successful collisions more ESC - most successful collisions no altering of structure - weak hydrogen bonds break changes the tertiary structure active site no longer complementary no ESC - enzyme denatures
37
describe how pH affects enzyme action
- small pH change - large pH change
38
why does pH affect enzyme action
- R group in active site may change reversible - bonds in tertiary structure break active site changes shape irreversible (denatured)
39
describe how enzyme concentration affects enzyme action
enzyme conc = low then rate = low enzyme conc increases then rate increases with set amount of substrate rate plateaus
40
why does enzyme concentration affect enzyme action
- few successful collisions = few ESC = product starts to produce - more successful collisions = more ESC = more product - most successful collisions = more ESC = more product - limiting factor = substrate conc
41
describe how substrate concentration affects enzyme action
substrate conc = low then rate = low substrate conc increases then rate increases with set amount of enzymes rate plateaus
42
why does substrate concentration affect enzyme action
- few successful collisions = few ESC = product starts to produce - more successful collisions = more ESC = more product - most successful collisions = more ESC = more product - limiting factor = enzyme conc (the number of active sites)
43
what happens at both high and low conc for CI
the rate will eventually reach the same as without an inhibitor as enough substrate is added
44
what does low conc require with CI
less substrate added to overcome the inhibition and reach the maximum R of R
45
what does high conc require with CI
more substrate added to overcome the inhibition and reach the maximum R of R
46
what happens if a NCI is added
the maximum R of R will never reach the same maximum R of R as it would with no inhibitor present (the maximum rate would be lower at a higher conc of NCI)
47
What is the shape of the competitive inhibitor
Similar to substrate
48
What is the shape of the non competitive inhibitor
Not similar to substrate
49
Where does a competitive inhibitor bind
Binds to AS no ESC forms
50
Where does a non competitive inhibitor bind
Binds to allosteric site away from the AS
51
What is the effect on the enzymes for a competitive inhibitor
No substrate can bind whilst AS occupied
52
What is the effect on the enzymes for a non competitive inhibitor
Causes conformational change changes tertiary structure AS no longer complimentary
53
What is the effect on the R of R for a competitive inhibitor
Reduces R of R (less product is produced)
54
What is the effect on the R of R for a non competitive inhibitor
Reduces R of R (less product formed)
55
An enzyme-controlled reaction is inhibited by substance X. Suggest a simple way in which you could tell whether substance X is acting as a competitive or non-competitive inhibitor.
Increase the substrate conc. If CI the degree of inhibition is reduced. If NCI the degree of inhibition stays the same.

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