Proteins and amino acids wace

Question 1

Describe amino acids-what are they?
What are they made up of

Answer 1

-monomers making up proteins
-at least 50 amino acids when chain can be classified as protein
-has amino (weakly basic) and carboxyl (weakly acidic) functional group
-hydrogen attached to central carbon

Question 2

Describe proteins. What are they?

Answer 2

organic biopolymers containing amino acids joined by condensation to create polyamide
-polyamide chain folds into specific shapes to=protein w/many functions

Question 2

What are the biological roles of proteins

Answer 2

Structural: main component of body tissue i.e. muscles, skin, ligaments, and hair
Catalytic: all enzymes=proteins, catalyse biochemical reactions
Immunological: antibodies
Signalling: hormones and receptors

Question 3

What is the general formula for amino acids?
What are these amino acids called?

Answer 3

H2N-CH(R)-COOH
-α-amino acids or 2-amino acids
-have amino and carboxyl attached to same carbon (α-carbon)

Question 4

What are the properties of amino acid side chains (r groups)

Answer 4

-can be polar or non-polar
-can include functional group behaving as proton donor (carboxyl)
-or proton acceptor (amino)

Question 5

What is meant by essential amino acids

Answer 5

-body can synthesis 11/20 amino acids required to make protein=non-essential
-other 9 must be included in diet=essential amino acids

Question 6

What is a zwitter ion
Provide an example diagram

Answer 6

-compound w/no overall electrical charge but which contains separate parts that are pos. and neg charged
-in aqueous solution their is an internal transfer of hydrogen group from COOH to NH2 to leave ion w/both negative and positive charge

Question 7

Describe the acid-base properties of amino acids

Answer 7

-increase pH of solution by addition of OH ions=removal of H ion from NH3 group
-decrease pH by addition of H cause COO- part of zwitter ion to accept H+

Question 8

Describe the solubility of amino acids

Answer 8

-generally soluble in water/insoluble in organic
-due to presence of zwitter ion, in water, ionic attractions between ions in solid a.acid are replaced by strong attractions bwn polar water molecules and zwitter ions
-extent of solubility depends on size and nature of R group

Question 9

What occurs during a reaction between COOH and NH2
Provide and example diagram

Answer 9

-amide produced (CONH)
-molecule of water also produced

Question 10

What occurs during condensation reaction between 2xamino acids

Answer 10

-peptide link formed(amide group linking functional groups)
-bond between carbon and nitrogen=peptide bond
-2-amino acids bonded together=dipeptide
-and small molecule of water

Question 11

Difference between amide and peptide

Answer 11

amide: CNNCCNNCCNNC (alternate)
peptide: CNCNCNCNCNCN (don’t flip)

Question 12

Define polypeptide

Answer 12

polymers formed by condensation polymerisation of amino acids

Question 13

How to name polypeptides

Answer 13

-amino group on left N-terminal
-carboxyl group on right C-terminal
-3 letter short hand notation to list
-chain longer than 50=protein with more complex 3 dimensional structure
-with exception of C terminal, all end in yl
e.g. alanylglycylserine (Ala-aly-ser)

Question 14

What is the primary structure of proteins

Answer 14

the number, type and sequence of amino acid units in a protein

Question 15

What is a proteins secondary structure

Answer 15

secondary interactions w/other chains can cause twisting or folding
-alpha helix forms bwn amino acids that are 4 amino acids up a chain
-structure spiral shape
-if large r group=prevents helix forming

-beta pleated sheets forms when polypeptide chains lien up parallel to eachother
-H bonds then occur at regular intervals due to regular repeating(NCCNNCCN) backbone of protein chain

Question 16

What is the protien data bank

Answer 16

-3D structural data of large biological molecules
-data obtained from xrays, etc
-structure then visualised
-data will include function location and interactions
-aids in understanding role of protein in human health and diseases

Question 17

Define lock and key and induced fit
Provide example equation of enzyme-substrate reaction

Answer 17

-active sight is specific to the substrate, once attached, forms enzyme-substrate complex which allows bonds to be broken

-shape of active site can alter to accommodate substrate

Question 18

How does pH effect enzyme function

Answer 18

-enzymes work best at optimum pH
-if pH is higher than optimum level, bonds bwn R groups can be disrupted
-pH effects functional groups-acidic COO- while NH+ basic
-ionic bonds broken
-structure not held in place, protein chain will unfold
-shape of the active site changes=denature
-no longer function

Question 19

How does temperature effect enzyme function

Answer 19

low:
-low temp=low Ek of enzyme and substrates=less collision per unit time/less successful etc
-none/very few e-s complexes formed
-inactivated
high:
-higher Ek=break bonds of tertiary structure
-cause shape of enzyme to unfold=loss of active site=denatured
-w/out active site, e-s complex cannot form=cant catalyse reaction

Question 20

Denaturation vs hydrolysis

Answer 20

-disruption of side chains of amino acid peptide bonds=changes tertiary structure of enzyme, no effect to primary
-hydrolysis breaks covalent peptide bonds=shorter peptide chains=effect to primary structure

Question 21

What are the advantages and disadvantages of enzymes in industry

Answer 21

advantages
-effective at biological temps/pH levels=decrease cost and energy
-reusable and used for more time
-biodegradable=less pollution

disadvantages
-sensitive to pH/temp change
-costly to produce
-will only generally occur in aqueous

Question 22

Describe the production of ethanol via hydrolysis of ethene
What are it’s requirements

Answer 22

-quicker process than fermentation
-moderate 300C,607Mpa catalyst (H3PO4)
-products fvrd at low temp (exothermic) moderate temp compromise rate and yield as high temp=higher reaction rate but lower yield
-high pressure fvrs both high yield and and fast rate. fwd favoured as 1 gaseous product and 2 reactants

disadvantage:
-ethanol produced this way increase CO2 in atmosphere when burnt