1.3 proteins

Question 1

how many amino acids are found in biology

Answer 1

20

Question 2

structure of amino acid

Answer 2

H 2NCHRCOOH

amine group
r group
carboxhylic group

Question 3

what is different for each of the twenty amino acids

Answer 3

R group

Question 4

what elements are contained in the general structural of amino acid

Answer 4

nitrogen,hydrogen,carbon,
oxygen

some contain sulphur

Question 5

How do polypeptides form

Answer 5

when we join 3 or more amino acids we get a polypeptide
through condensation reaction (-CONH-)
(removal of water)

Question 6

name all levels of protein structure

Answer 6

primary structure
secondary structure
tertiary structure
quaternary structure

Question 7

define primary structure

Answer 7

the specific order of amino acids in a polypeptide chain. that helps determine its tertiary structure
this is determined by sequence of codons on mRNA

Question 8

why is primary structure important

Answer 8

helps determine final 3D shape of the protein molecule to carry out its function effectively.

Question 9

define secondary structure of a protein

Answer 9

hydrogen bonds form between slightly negative oxgen and attaches to carbon = oxygen and hydrogen

hydrogen bonds form between the slightly positive hydrogen attached -NH

N-H +
C=O -
^ attracted together, twists and fold into shapes (secondary structure)
hydrogen bonds form all between polypeptide chain

Question 10

describe the 2 types of secondary protein structure

Answer 10

a-helix
all N-H bonds on same side of protein chain
spiral shape
H-bonds parallel to helical axis

B-pleated sheet
N-H AND C=O groups alternate from one side to the other

Question 11

define ‘tertiary structure’ of a protein. name types of bonding present

Answer 11

the 3D folding of the secondary structure into a complex shape. The shape is determined by the type of bonding present, such as hydrogen bonding, ionic bonding (salt bridges, form between oppositely charged groups on the R groups) and disulfide bridges (covalent bonds between sulphur atoms in cysteine) .

Question 12

describe disulfide bridges in the tertiary structure of proteins

Answer 12

strong covalent S-S bonds between molecules of the amino acids cysteine

Question 13

describe ionic bonds in the tertiary structure of proteins

Answer 13

relatively strong bonds between charged R groups
ionic bonds are broken by changes to Ph

Question 14

describe the hydrogen bonds in the tertiary structure of proteins

Answer 14

intermolecular force between positive hydrogen of o-h or n-h and lone pair on o or n of an adjacent molecule
numerous and easily broken

Question 15

define ‘quaternary structure’ of a protein

Answer 15

functional proteins may consist of morebthan one polypeptide
precise 3D structure held together by the same types of bond as tertiary structure
may involve addition of prosthetic groups example metal ions or phosphate groups

Question 16

describe the structure and function of globular proteins

Answer 16

spherical and compact
hydrophilic R groups face outwards and hydrophobic inside

Question 17

fibrous proteins

Answer 17

Long parallel polypepdes * Very lile terary/quaternary structure - mainly secondary structure. * Occasional cross-linkages which form microfibres for tensile strength * Insoluble * Used for structural purposes

Question 18

collagen

Answer 18

Collagen is an example of a fibrous protein. It has high tensile strength due to the large number of hydrogen bonds in the structure. Collagen molecules are made up of three disnct α-chains which form a triple gamma helix.