unit 3: enzymes and proteins

Question 1

what are proteins made from

Answer 1

C , H , O , N AND S

Question 2

What are proteins

Answer 2

polymers of a long chain of monomers called amino acids

Question 3

how many natural occurring proteins are there

Answer 3

20

Question 4

what are properties of amino acids determined by

Answer 4

amino acid sequence of the protein and the way the protein is folded

Question 5

give examples of proteins functions

Answer 5

haemoglobin , antibodies , enzymes

Question 6

what is the amino acid sequence

Answer 6

R
H2N-C-COOH
H

Question 7

how do amino acids differ

Answer 7

by their R groups

Question 8

how are amino acids linked together

Answer 8

through a condensation reaction to form dipeptides and polypeptides

Question 9

what do condensation reactions do with water

Answer 9

release water

Question 9

when does hydrolysis occur

Answer 9

when dipeptides and polypeptides are broken down , use water

Question 10

what happens during a condensation reaction of amino acids

Answer 10

-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
-

Question 11

what is the primary structure

Answer 11

sequence of amino acids in the polypeptide chain

Question 12

what is the secondary structure

Answer 12

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

Question 13

what is the tertiary structure

Answer 13

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

Question 14

what is the quaternary structure

Answer 14

-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

Question 15

how does a protein determine its function

Answer 15

by its shape

Question 16

what is one part of a molecule called

Answer 16

active site

Question 16

how is the activation energy lowered when a substrate fits into the active site

Answer 16

-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

Question 17

what happens when you change the shape of the active site

Answer 17

stops the enzyme from working-denaturation

Question 18

what is the lock and key model

Answer 18

substrate fits into the active site like a key fits into a lock.They are complementary and so show specifically

Question 18

what is the induced fit model

Answer 18

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

Question 19

why is measuring initial rates of reaction important

Answer 19

as a reaction proceeds reactants are being used up , means the substrate is becoming less concentrated which will cause the reaction to slow down

Question 19

how do you test for proteins

Answer 19

-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

Question 20

what are enzymes made out of

Answer 20

proteins

Question 21

what are enzymes

Answer 21

biological catalysts - speed up chemical reactions in cells

Question 22

what do enzymes act on

Answer 22

substrate molecules

Question 22

what is an active site

Answer 22

specific shape for the substrate to enter which forms a enzyme sublate complex

Question 23

are enzymes used up in reactions

Answer 23

no , can be produced in small amounts

Question 24

how do enzymes work

Answer 24

• 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

Question 25

how can temp effect enzyme activity

Answer 25

-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