proteins

Question 1

amino acids

Answer 1

proteins are made up of monomers and have a variety of functions within all living organisms

Question 2

proteins - properties

Answer 2

• fibrous proteins form long parallel chains and have structural functions, such as collagen
• globular proteins are spherical and have many metabolic functions (eg. enzymes)

Question 3

polypeptide vs protein

Answer 3

• polypeptide = a long chain of amino acids
• protein = a polypeptide folded into a specific shape (proteins have shape)

Question 4

general structure of protein

Answer 4

• amino group
• variable R group
• carboxylic acid group

Question 5

protein - structure

Answer 5

• every single amino acid looks exactly the same apart from the variable group
• there are 20 naturally occurring amino acids. each of them will have different variable R groups

Question 6

polypeptide

Answer 6

• multiple amino acids bonded together. in a protein, there can be multiple polypeptide chains folded into a specific shape
• the reaction that forms the bonds is a condensation reaction

Question 7

dipeptide molecule

Answer 7

formed by the condensation of two amino acids

Question 8

functional protein

Answer 8

can contain one or more polypeptides

Question 9

hydrogen bonding

Answer 9

• strongest form of intermolecular force
• it occurs between different molecules and is between hydrogen and either nitrogen, oxygen or fluorine

Question 10

primary structures

Answer 10

the basic sequence of amino acids within the protein

Question 11

secondary structures

Answer 11

the polypeptide chain has initial folding into either a beta pleated sheet or an alpha helix. this occurs as a result of hydrogen bonding between nearby amino acids

Question 12

tertiary structures

Answer 12

• different parts of the polypeptide chain with interact with each other through hydrogen bonding, ionic bonding, disulphide bridges and hydrophilic/hydrophobic interactions
• the tertiary structure completely relies upon these interactions and will give the specific 3D shape of the protein. it’s essential that these proteins have a specific shape for their roles as enzymes, receptors, antigens as they rely on a complementary molecules that fits them

Question 13

quaternary structure

Answer 13

multiple polypeptide chains interact to form a protein. proteins can be either globular or fibrous

Question 14

haemoglobin

Answer 14

• protein found in red blood cells (quaternary)
• used to carry oxygen round the body
• 4 subunits: 2 alpha and 2 beta polypeptides
• in the middle of each polypeptide is a haem group, flat and circular with iron (Fe2+) in the middle
• held in place by hydrogen & ionic bonds

Question 15

what is the test for identifying proteins?

Answer 15

biuret test

Question 16

biuret test for proteins

Answer 16

• used biuret reagent that changes colours
• from pale blue to lilac in the presence of protein