B M 3 : Proteins

Question 1

what are proteins made from?

Answer 1

Long chains of amino aicds

Question 2

what are the monomer of proteins?

Answer 2

Amino aicds

Question 3

when is a dipeptide formed?

Answer 3

When 2 amino acids join together

Question 4

whens a polypeptide formed?

Answer 4

when more than 2 amino acids join together

Question 5

what are proteins made up of?

Answer 5

One or more polypeptides

Question 6

Do different amino acids have different variable groups?

Answer 6

Yes

Question 7

general structure of amino acids

Answer 7

CH(3)
          /
h(2)N-C-COOH
          /
         H

• Carboxyl group (-COOH)
• amine or amino group (-NH2)
• and a carbon containing R group (variable group)

Question 8

how many amino acids are there?

Answer 8

20

- the only difference between them is what makes up their carbon-containing R group

Question 9

what reaction forms polypeptides?

Answer 9

condensation reactions

- amino acids linked together by condensation reactions

Question 10

what are the bonds formed between the amino acids called?

Answer 10

Peptide bonds

Question 11

how many structural levels do proteins have?

Answer 11

four

Question 12

primary structure of proteins?

Answer 12

the sequence of amino acids in the polypeptide chain

Question 13

Secondary structure of amino acids?

Answer 13

• hydrogen bonds form between the amino acids in chain

- causes it to coil into an alpha (a) helix or into a beta (b) pleated sheet

Question 14

tertiary structure of amino acids?

Answer 14

• coiled and folded further
• more bonds form between different parts of the polypeptide chain (hydrogen bonds and ionic bonds)
• disulfide bridges also form
• for proteins made from a single polypeptide chain this forms their final 3D structure

Question 15

what are ionic bonds?

Answer 15

attractions between negative and positive charges on different parts of a molecule

Question 16

how are disulfide bridges formed?

Answer 16

whenever two molecules of the amino acid cysteine come close together - sulfur atom in one cysteine bond to the other sulfur atom in the other

Question 17

Quaternary structure of proteins?

Answer 17

• some proteins made of several different polypeptide chains held together by bonds
• Quaternary structure is the way these chains are assembled together
• for proteins made form more than one polypeptide chain this forms their final 3D structure

Question 18

examples of proteins?

Answer 18

• enzymes
• antibodies
• transport proteins
• structural proteins

Question 19

about enzymes?

Answer 19

• spherical shaped due to tight folding of polypeptide chains
• they’re soluble + often have roles in metabolism

Question 20

about antibodies?

Answer 20

• involved in immune response
• made up of 2 short polypeptide chains and two long polypeptide chains bonded together
• antibodies have variable regions, amino acid sequences in these regions vary greatly

Question 21

about transport proteins?

Answer 21

(example channel proteins - present in cell membranes)

• channel proteins contain hydrophobic and hydrophilic amino acids, cause protein to fold and form a channel
• these proteins transport molecules and ions across membranes

Question 22

about structural proteins?

Answer 22

• they’re physically strong
• consist of long polypeptide chains lying parallel to each other with cross links between them
• structural proteins include keratin ( hair and nails) and collagen (connective tissue)

Question 23

which test do you use to test for proteins?

Answer 23

Biuret test

Question 24

how to perform the biuret test?

Answer 24

2 stages
1 - test solution needs to be alkaline, so add a few droplets of sodium hydroxide solution
2 - then add some copper(II) sulfate solution

Question 25

results of biuret test

Answer 25

if protein present, turns purple

if there’s no protein, solution will stay blue