Proteins

Question 1

what monomers are proteins made up of ?

Answer 1

amino acids

Question 2

structure of amino acids

Answer 2

central carbon, amino acid , carboxyl group and R group

Question 3

what does the R group represent ?

Answer 3

all the variable group - 20 options

Question 4

what bond is formed between amino acid ?

Answer 4

peptide bond

Question 5

how are dipeptides formed ?

Answer 5

two amino acids join by a condensation reaction

Question 6

how are polypeptide formed ?

Answer 6

condensation of many amino acids

Question 7

Ionic bond

Answer 7

electrostatic interaction between oppositely charged ion - may often be broken by changing the pH

Question 8

hydrogen bonding

Answer 8

a hydrogen atom is shared by two other atoms

Question 9

disulphide bond

Answer 9

strong covalent bond formed by the oxidation of - SH groups of two cysteine side chains

Question 10

primary structure of protein

Answer 10

sequence of amino acids that make up the polypeptide chain - held together by peptide bonds

Question 11

secondary structure of protein

Answer 11

• sequence of amino acids causes parts of a protein molecule to bend into alpha helix shapes or fold into beta pleated sheets
• held by hydrogen bonds

Question 12

tertiary structure of protein

Answer 12

• further folding of the secondary structure to form a unique 3D shape
• held in place by ionic, hydrogen and disulphide bonds

Question 13

quaternary structure of protein

Answer 13

a protein arises when two or more polypeptides become held together forming a complex, biologically active molecule

Question 14

biuret test for proteins

Answer 14

1. by adding an equal quantity of sodium hydroxide solution to the test solution
2. a few drops of 0.5 % copper ( II ) sulphate solution
3. if a colour changed from pale blue to lilac than a protein is present

Question 15

examples of proteins

Answer 15

collagen and haemoglobin

Question 16

Fibrous protein

Answer 16

• long, coiled polypeptide chain
• single collagen molecules has 3 polypeptide chains
• held together by covalent and hydrogen bonds

Question 17

structure of collagen

Answer 17

• three long polypeptide molecules coiled together to form triple helix
• every 3rd amino acid is glycine + 2 amino acids are mostly proline and hydroxy proline
• covalent bonds form between the polypeptide chains together with many hydrogen bonds

Question 18

Globular protein

Answer 18

• spherical
• polypeptide chains wind in a way so hydrophilic amino acids are at the surface and hydrophobic amino acids are at its core - soluble in water

Question 19

structure of haemoglobin

Answer 19

• respiratory pigment found in our red blood cells
• consists of 4 polypeptide chains, each bound to an iron - containing haem group

Question 20

What does iron in the haem group binding to oxygen cause ?

Answer 20

a change in shape of the haemoglobin molecule, making it easier for the further oxygen molecules to bind