proteins⭐️

Question 1

explain how amino acids are linked together to form proteins

Answer 1

amino acids form dipeptides and then polypeptides via a condensation reaction, forming peptide bonds. the water is formed from the OH group of the carboxylic acid on one amino acid and the H in the amine group of anther amino acid. this sequence of amino acids is called a primary structure

Question 2

explain how polypeptides are arranged to form a secondary structure of a protein

Answer 2

hydrogen bonds form between the OH group of a carboxylic acid and the H group on the amine group causing the polypeptide chain to twist into an alpha helix or fold into beta pleated sheets

Question 3

explain how the secondary structure of a protein forms the tertiary structure of the protein

Answer 3

the specific 3D structure of a protein, formed by either hydrogen bonds, disulfide bridges and ionic bonds

Question 4

explain how to quaternary structure of a protein is formed

Answer 4

the large protein molecule is formed from two or more polypeptide chains and additional prosthetic group (non protein)

Question 5

describe a test for proteins

Answer 5

add sample to dilute sodium hydroxide. add very dilute copper sulphate and mix. a positive test is purple colour change

Question 6

why might two proteins have different tertiary structures if they have the same number and type of amino acid

Answer 6

different primary structure/different sequence of amino acids. different disulfide bridges, ionic or hydrogen bonds formed

Question 7

What bond forms between amino acids?

Answer 7

Peptide bonds

Question 8

How are polypeptides formed?

Answer 8

Amino acids linked together via a condensation reaction, forming peptide bonds and releasing a molecule of water

Question 9

How are disulfide bridges formed?

Answer 9

Two molecules of cysteine come close together so the sulfur atom on one cysteine bonds to the sulfur atom of the other.

Question 10

What are the four functions of proteins?

Answer 10

Enzymes, antibodies, transport proteins, structural proteins

Question 11

What is a structural protein?

Answer 11

They consist of long polypeptide chains lying parallel to each other with cross links between them. An example is keratin and collagen. They’re physically strong

Question 12

Discuss transport proteins as a function of proteins?

Answer 12

Present in the cell membranes such as channel proteins containing hydrophobic and hydrophilic amino acids which cause the protein to fold up and form a channel. Allows ions across the membrane

Question 13

Discuss antibodies as a function of proteins

Answer 13

Involved in the immune response. Made up of two short polypeptide chains and two long polypeptide chains bonded together. They have variable regions