2.1.2 proteins

Question 1

describe the structure of amino acids

Answer 1

central carbon atom surrounded by amino group + carboxyl group
1 H group attached
variable R-group = diff AA

Question 2

explain the process of joining AA

Answer 2

form by condensation reaction
OH form carboxyl group + H atom
produce H2O as product
forms PEPTIDE BOND

Question 3

describe the primary structure of proteins

Answer 3

sequence of AA in a chain
diff proteins made from diff AA chains
which AA present affect folding + shape

Question 4

describe the secondary structure of proteins

Answer 4

chains of AA forming diff shapes
alpha helix OR beta pleated sheet
hydrogen bonds form between NH and COOH groups = coiling

Question 5

describe the tertiary structure of proteins

Answer 5

additional bonds between AA leads to complex folding = 3D shape
ionic bonds = +ive and -ive R groups
disulphide bonds = sulphur ions (cysteine)

Question 6

explain the hydrophobic and hydrophillic interactions in proteins

Answer 6

proteins are made in aqueous environment of cell
= hydrophobic R groups clump
= hydrophilic R groups pushed outside

Question 7

describe the quarterary structure of proteins

Answer 7

2 or more proteins (sub units) associated
same types of bonds but between DIFFERENT INDIVIDUAL PROTEINS

Question 8

describe the properties of globular proteins

Answer 8

round + compact; proteins in tertiary structures
soluble = hydrophilic R group outside
easy to transport in solution

Question 9

describe the properties of insuline

Answer 9

hormone secreted in pancreas
made of 2 polypeptide chains held by disulphide bonds
soluble = can be transported in blood

Question 10

what is a conjugated protein

Answer 10

contain prosthetic groups
complex proteins
can have lipid or carbohydrate prosthetic groups
also metal ions

Question 11

describe the properties of haemoglobin

Answer 11

contains haem prosthetic group
made of 4 polypeptide chains (2 alpha and 2 beta sub units)
carries oxygen in blood; iron in haem group reversibly binds to O

Question 12

describe the structure of amylase

Answer 12

enzyme to catalyse breakdown of starch
made of single chain of AA
secondary struc. = alpha helix + beta pleated sheet sections

Question 13

describe the properties of fibrous proteins

Answer 13

tough, long, rope shaped
unreactive
insoluble = high prop. of hydrophilic R groups
repetitive structures = v. organised + not folded

Question 14

describe the properties of collagen

Answer 14

in animal connective tissues (skin, tendons…)
v. strong
rope structure = flexible
made of 3 polypeptides

Question 15

describe the properties of keratin

Answer 15

animal structures (hair, skin, nails)
strong disulphide bridges due to cysteine
strong, inflexible, insoluble
more disulphide bridges = less flexible `

Question 16

describe the properties of elastin

Answer 16

in elastic fibres (skin, large blood vessels, alveoli, ligaments)
flexibility = can expand when needed; return to OG shape
made of tropoelastin