Proteins

Question 1

Structure of amino acid

Answer 1

Amino acid - monomer of proteins
Parts of amino acid
Central carbon atom attached to…
Amino group(NH2)
Carboxyl group(COOH)
Hydrogen atom
R-group(specific to each amino acid)

Question 2

The formation of a peptide bond

Answer 2

Condensation reaction
Peptide bond
OH group of carboxyl and H of amino group

Question 3

Primary structure-polypeptides

Answer 3

Through condensation reactions- amino acids polymerise
Form polypeptides
Sequence of amino acids in a polypeptide chain is the primary
Determined by DNA
Determines final shape
Shape is specific to function

Question 4

The secondary structure of proteins

Answer 4

Polypeptides have amino group and carboxyl group
H in amino has (-) charge
Therefore form H bonds
Causes chain to be twisted to 3-D shape
Such as coil shape-a-helix

Question 5

Tertiary structure of protiens
Bonds in tertiary structure

Answer 5

a-helixes can be twisted and folded and turn into a complex and specific structure
Maintained by different bonds

disulphide bridges - relatively strong and not easily broken
ionic bonds- carboxyl and amino group
IB>DB
hydrogen bond numerous and easily broken

Question 6

Quaternary structure of proteins

Answer 6

Large proteins from complex molecules with a number of individual chains linked in various ways
There may also be non-protein groups associated with it(eg.heam)
sequence of amino acids determine the shape

Question 7

Test for proteins

Answer 7

Biuret test
add sample of solution to test tube and add equal amount of NaOH
add few drops of very dilute CuSO4 and mix gently
purple colouration = (+) result
remains blue if (-)

Question 8

Fibrous proteins

Answer 8

long chains which parallel to one another. linked by cross bridges and form very stable moleculeseg;collagen(found in tendons)
+primary structure is an unbranched polypeptide chain
+secondary-tightly wound
+glycine aids close packing
+tertiary-chain is twisted into a second helix
+Quatanary- made from three such chains