Chapter 3 - Biological molecules - proteins

Question 1

what are peptides

Answer 1

polymers made up of amino acids - proteins consist of one or more polypeptides arranged as a complex macromolecule

Question 2

what elements do proteins contain

Answer 2

Hydrogen Nitrogen Oxygen and Carbon

Question 3

what is the basic structure of an amino acid

Answer 3

central carbon and hydrogen
left - amine group (NHH)
right - carboxyl group (COOH)
down - R group (different in all amino acids)

Question 4

how do amino acids join to form peptides

Answer 4

condensation reaction between one amine group and one carboxyl group to form a peptide bond forming a dipeptide

Question 5

what is the primary structure of a polypeptide

Answer 5

the sequence in which amino acids are joined (peptide bonds)

Question 6

what are the two secondary structures

Answer 6

alpha helixes or beta pleated sheets (hydrogen bonds)

Question 7

what are the interactions in the tertiary structure

Answer 7

between r groups:
hydrophobic/hydrophilic interactions (weak)
hydrogen bonds (weakest)
ionic bonds (strong)
disulphide bridges (strongest) - covalent bonds between r groups containing sulphur

Question 8

describe a quaternary structure

Answer 8

interaction between two or more individual proteins called subunits (same bonds as in the tertiary structure)

Question 9

describe the quaternary structure of haemoglobin

Answer 9

made of two sets of identical subunits - two alpha and two beta subunits; each subunit contains a prosthetic haem group

Question 10

what is the test for proteins

Answer 10

biuret test - peptide bonds form violet coloured complexes with copper ions in alkaline solutions

Question 11

what are the two main protein groups

Answer 11

globular and fibrous

Question 12

what are the features of globular proteins

Answer 12

compact, water soluble and usually roughly spherical - hydrophobic r groups are on the inside and hydrophilic r groups are on the outside

Question 13

what type of protein is insulin

Answer 13

globular

Question 14

what is a conjugated protein

Answer 14

globular proteins containing a prosthetic group (non-protein component)

Question 15

what is a simple protein

Answer 15

a protein without prosthetic groups

Question 16

what does the haem in haemoglobin do

Answer 16

the iron in it can reversibly combine with oxygen - it allows it to carry oxygen in the blood

Question 17

what is the structure of catalase and what does it to

Answer 17

it is a quaternary protein containing four haem prosthetic groups. this allows catalase to breakdown hydrogen peroxide which is a by-product of metabolism

Question 18

what is a the structure of a fibrous protein

Answer 18

long insoluble molecule (due to hydrophobic r-groups)
limited range of amino acid, usually with short r-groups
repetitive structure

Question 19

give examples of fibrous proteins

Answer 19

keratin, elastin, collagen

Question 20

where is keratin found and what is its structure

Answer 20

hair, skin and nails
large proportion of sulphur containing amino acid - cysteine
many disulfide bridges
strong inflexible and insoluble
(hair contains less bonds)

Question 21

where is elastin found and what is its basic structure

Answer 21

in elastic fibres (walls of blood vessels and alveoli in lungs)
quaternary protein

Question 22

where is collagen found and what is its structure

Answer 22

connective tissue found in skin, tendons, ligaments and the nervous system
three polypeptides wound together in a long strong rope-like structure
has flexibility