Proteins and enzymes

for the eduqas branch of wjec

  • Created by: lridgeway
  • Created on: 27-04-18 16:24
What atoms are in proteins?
carbon, hydrogen, nitrogen and oxygen. some also contain phosphorous and sulfur
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What is the monomer in a protein?
amino acid
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What is a chain of amino acids called?
polypeptide chain
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What structure does an amino acid take?
NH2 group then a carbon with a hydrogen and a variable group attached and then a COOH group
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What happens to amino acids when they are dissolved?
they dissociate when dissolved to become dipolar ions called zwitterions containing COO- and NH3+
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What can amino acids be?
amphoteric meaning a hydrogen moves from COOH to NH2 group
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What do dissovled amino acids act as?
buffers to prevent pH cahnge as the relevent ends reacts to use up either excess OH -or H+ ions
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What are the bonds in proteins called and how are they formed?
peptide bonds which are fromed by condensation/hydrolysis reactions
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Whats is two amnio acids called?
dipeptide
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What is the primary structure of a protein?
sequence of amino acids in a polypeptide chain
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What is the secondary structure of a protein?
hydrogen bonds between amnio acids and fold into a alpha helix or a beta pleated sheet
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What is the tertiary structure of a protein?
secondary folds into a specific 3D shape. bonds used are; hydrogen, ionic, disulphide and hydrophobic interactions (van der Waals)
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What is the quaternary stucture of a protein?
more than one polypeptide chain held together in a specific 3D shape (bond similar to tertiary) and example in haemoglobin and some contain non amino acid, prosthetic groups
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What is the structure of globular proteins?
form a spherical mass with a specific 3D shape. they fold so the hydrophillic groups are on the outside and the hydrophobic groups are inside
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What is the structure of fibrous proteins?
long chains of fibres (3) which create a triple helix of polypeptide chains held by hydrogen bonds and are insoluble
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What are fibrous proteins used for and give an example
useful for stucture and support and an example is collagen (found in skin, teeth, bone, tendons and blood vessel walls
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Define enzymes
biological catalysts as they speed up reactions, aren't used up, aren't changed and have a high turnover
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Define catalyst
increase rate of reaction without being used up, by lowering activation energy
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Define specificty
enzymes only catalyse one reaction
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Define substrate
the molecule the enzyme acts upon
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Define intracellular
works inside cell
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Define extracellular
works outside cell
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Define active site
the region where other molecules combine or where a molecule is broken (site of reaction)
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What does the lock and key model suggest?
only 1 substrate fits an enzymes active site and that the enzymes doeant change shape during the process
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What are the components of an enzyme reaction?
enzyme, substrate, enzyme-substrate complex, enzyme-product complex and products
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What does the incuded fit theory state?
observations suggest that enzymes change slightly when substrate binds to the active site to accommodate the substrate
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What is an example of the induced fit theory and what does it do?
Lysozyme - anti bacterial enzyme found in human saliva and mucus. its active site is a groove which, when attched to sugar on bacteria cell walls, closes and encases the sugar. it hydrolyses the bond between the sugar, weakening the cell
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Explain why the rate of reaction for an enzyme increases with temperature until an optimum
there is increased kinetic energy which gives more frequent successful collisions between enzyme and substrate. This means more enzyme-substrate complexes are formed increasing the rate of reaction
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Why does the graph for temperature effect on enzyme rate of reaction rapidly decreases after optimum temperature?
further increase in molecules vibrating which breaks the hydrogen bonds holing the specific 3D shape (tertiary and primary) which changes the active site shape so substrate can no longer react. this is called denaturing and is irreversible
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Explain how the concentration of the enzyme effects rate of reaction
increases as more enzymes working at once so more frequent successful collisons and more enzyme substrate complexes. eventually the concentration of substrate becomes a limiting factor
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Explain how the concentration of the substrate effects rate of reaction
increases the rate of reaction due to the more frequent successful collisons and more enzyme substrate complexes. maximum rate is reached as all active sites are filled so enzymes are at maximum rate and ROR can no longer increase (saturation)
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Explain how large changes in pH effects enzyme rate of reaction?
extreme changes can cause permanent changes as ionic and hydrogen bonds are distrubed and the structure of the active site changes denaturing the enzyme.
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Explain how small changes in pH effect enzyme rate of reaction?
the binding or catalytic sites within the active site take the form of charged ions, which are inhibitory because the substrate can no longer react, these effects are reversible
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What is a competitve inhibitor?
interferes with active site of enzymes so substrate cannot bind, this is temporary and is a similar shape to the substrate
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What is a non competitive inhibitor?
changes shape of enzymes so substrate cannot bind by binding to alosteric site, this is permenant
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What is an immobilised enzyme?
bound to an inert soluable matrix
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What are the ways to immobilse an enzyme?
entrapment, carrier-bound, crosslinks
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What are the benfits of immobilsed enzymes?
no contamination of product, detect small amounts of substrate, less likely to denature so more stable, can resue the enzyme
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What are the two main uses for immobilsed enzymes?
food production, biosensors
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Other cards in this set

Card 2

Front

What is the monomer in a protein?

Back

amino acid

Card 3

Front

What is a chain of amino acids called?

Back

Preview of the front of card 3

Card 4

Front

What structure does an amino acid take?

Back

Preview of the front of card 4

Card 5

Front

What happens to amino acids when they are dissolved?

Back

Preview of the front of card 5
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