unit 3: enzymes and proteins Flashcards
what are proteins made from
C , H , O , N AND S
What are proteins
polymers of a long chain of monomers called amino acids
how many natural occurring proteins are there
20
what are properties of amino acids determined by
amino acid sequence of the protein and the way the protein is folded
give examples of proteins functions
haemoglobin , antibodies , enzymes
what is the amino acid sequence
R
H2N-C-COOH
H
how do amino acids differ
by their R groups
how are amino acids linked together
through a condensation reaction to form dipeptides and polypeptides
what do condensation reactions do with water
release water
when does hydrolysis occur
when dipeptides and polypeptides are broken down , use water
what happens during a condensation reaction of amino acids
-the amino acids line up
-amine group of one amino acid lines up with the carboxyl group of another
-amine group donates 1 H atom
-carboxyl group donates an OH group
-water is eliminated
-petide bond is formed
-resulting molecule is a dipeptide
-
what is the primary structure
sequence of amino acids in the polypeptide chain
what is the secondary structure
the polypeptide chain doesn’t remain straight hydrogen bonds form between the amino acids in the chain, this makes sections of it to coil into an alpha helix of a beta pleated sheet
what is the tertiary structure
the coiled/folded chain of amino acids is often coiled an folded further
-more bonds form between the different points of the polypeptide chain
-hydrogen bonds, ionic , covalent(disulphide bridges) also form when two molecules of cysteine come close together
-the surfer atoms bond together
-final 3D structure of a proton made from the amino acid chain
what is the quaternary structure
-protein is made of more than one polypeptide chain , its the way that the different chains are arranged together,simlar bonds found in the tertiary structure are present here haemoglobin has a quaternary structure
how does a protein determine its function
by its shape
what is one part of a molecule called
active site
how is the activation energy lowered when a substrate fits into the active site
-holding substrate molecules close together and so that bonds can be made
-putting a strain on bonds in the substrate molecule and so they break more easily
-changing the substrate will successfully collide with the enzymes molecules
what happens when you change the shape of the active site
stops the enzyme from working-denaturation
what is the lock and key model
substrate fits into the active site like a key fits into a lock.They are complementary and so show specifically
what is the induced fit model
the enzyme substrate complex changes shape slightly to accommodate the fit , this helps to explain why enzymes are so specific and only bond to one particular substrate
-the substrate needs to have the correctly shaped active site as well as making the active site change shape in the right way
why is measuring initial rates of reaction important
as a reaction proceeds reactants are being used up , means the substrate is becoming less concentrated which will cause the reaction to slow down
how do you test for proteins
-bieuret test
-solution needs to be alkaline so first add a few drops of sodium hydroxide solution
-add some copper sulphate solution
if protein is present the solution will turn purple, if not remains blue
what are enzymes made out of
proteins
what are enzymes
biological catalysts - speed up chemical reactions in cells
what do enzymes act on
substrate molecules
what is an active site
specific shape for the substrate to enter which forms a enzyme sublate complex
are enzymes used up in reactions
no , can be produced in small amounts
how do enzymes work
- molecules in solution are continually moving around with kinetic energy
-for reactions to take place molecules need to make successful collisions
-the kinetic energy required for the reaction to take place is called the activation energy
-enzymes lower the activation energy of a reaction
-this means thatraection are able to take place at lower temp when enzymes are involved
-increasing the temp when enzymes are involved , gives molecules more kinetic energy and so the rate of reaction will increase
-increase the conc of the molecules also increase the rate of reaction
how can temp effect enzyme activity
-rate of reaction increases with increased temp
-enzyme and sublate have more kinetic energy and collide more frequently
above a certain temp the enzymes vibrate a lot
-som of the bonds holding the enzyme molecule in shape begins to break
-the enzyme molecule loses its shape and actively - denatured
