proteins

Question 1

what is the monomer of proteins?

Answer 1

amino acids

Question 2

general structure of proteins

Answer 2

• amine group on the left (H2N)
• R group joined to the alpha carbon
• carboxyl group on the right (COOH)

Question 3

what is a condensation reaction for proteins?

Answer 3

• forms between the hydrogen in the amine group and the hydroxide in the carboxyl group
• when two amino acids join together to form a dipeptide
• or when two or more amino acids join together to form a polypeptide
• this makes a peptide bond form
• it also forms a water molecule

Question 4

role of hydrogen bonds

Answer 4

contribute to the rigidity and maintain the shape

Question 5

role of ionic bonds

Answer 5

creates electrostatic attractions, between positive and negatively charged ions

Question 6

role of disulfide bridges

Answer 6

stabilises the 3d structure

Question 7

primary structure of proteins

Answer 7

number and type of sequence ordered by amino acids

Question 8

secondary structure of proteins

Answer 8

coiling: alpha helix
- left handed spiral
- held by hydrogen bonds between -NH and -CO

folding: b-pleated sheet
- held by hydrogen bonds
- polypeptide zigzags to form sheet of antiparallel strands

Question 9

tertiary structure of proteins

Answer 9

• projects R group of amino acids
• determines folding and bonding
• 3d shape forms, active site formed
• can form hydrogen bonds, ionic bonds, disulfide bridges and cause hydrophobic interactions

Question 10

quaternary structure of proteins

Answer 10

• two or more polypeptide chains in a tertiary form combine to make more complex structure
• joined together by the different bonds in the tertiary stage

Question 11

what is a globular protein?

Answer 11

• enzymes, antibodies, hormones and plasma
• folded or spherical
• insoluable in water
• globular conjuated: contain a prosthetic group

Question 12

what is a fibrous protein?

Answer 12

• have structural functions
• strong and tough
• long chains with many crosslinks
• alpha helices linked into strands
• held together by hydrogen bonds
  examples: collagen and keratin

Question 13

biuret test for proteins

Answer 13

• solution needs to be made alkane with sodium/potassium hydroxide
• add copper (II) sulphate (biurets regeant)
• colour should change blue to purple
• more purple more proteins in the sample
• must be two or more peptide bonds present, otherwise no colour change visible