7.5 Proteins

Question 1

Outline primary structure in proteins

Answer 1

The linear sequence of the amino acids of which the protein is composed. Formed by covalent peptide bonds between adjacent amino acids. Controls all subsequent levels of structure because it determines the nature of the interactions between R groups of different amino acids.

Question 2

Outline secondary structure in proteins

Answer 2

The 2D shape of the polypeptide chain. Two common shapes are ‘α helix’ (A coil) and ‘β sheets’ (Pleated sheets which are mores stressed that alpha helices)

Question 3

Outline tertiary structure in proteins

Answer 3

3D shape of the protein. The way a polypeptide folds and coils to form a complex molecular shape. Important for the function of the enzyme (e.g. specificity of active site in enzymes). Caused by interactions between R groups.

Question 4

State the four types of bonding involved in the tertiary structure of a protein

Answer 4

H-bonds
Disulphide bridges
Ionic bonds
Hydrophilic / hydrophobic interactions

Question 5

Outline quaternary structure in proteins

Answer 5

The linking of two or more polypeptides to form a single protein. Sometimes contain a non-polypeptide structure called a prosthetic group (conjugated protein).

Question 6

Define conjugated protein

Answer 6

A protein containing a prosthetic group (non polypeptide structure)

Question 7

Define prosthetic group

Answer 7

A non-polypeptide structure involved in protein structure or function. Proteins containing them are called conjugated proteins.

Question 8

Contrast the shape of globular and fibrous proteins

Answer 8

Globular proteins are round in shape; fibrous proteins are long and narrow.

Question 9

Contrast the role of globular and fibrous proteins

Answer 9

Globular proteins (generally) have a functional role; fibrous proteins (generally) have a structural role.

Question 10

Contrast the solubility of globular and fibrous proteins

Answer 10

Globular proteins are (generally) soluble in water; fibrous proteins are (generally) insoluble.

Question 11

Contrast the amino acid sequence in globular and fibrous proteins

Answer 11

Globular proteins have irregular sequences; fibrous proteins have repetitive sequences.

Question 12

Contrast the sensitivity of globular and fibrous proteins

Answer 12

Globular proteins are more sensitive to changes in heat, pH; fibrous proteins are less sensitive.

Question 13

State two fibrous proteins.

Answer 13

Collagen, Elastin, Keratin ect

Question 14

State two globular proteins

Answer 14

Catalase, Lactase, ect

Question 15

Describe polar amino acids

Answer 15

Hydrophilic R groups. Water soluble. Surface of globular proteins.

Question 16

Describe non-polar amino acids

Answer 16

Hydrophobic R groups. Lipid soluble. Inside globular proteins. Stabilize the structure of water soluble proteins.

Question 17

Outline significance of polar and non-polar amino acids in transport

Answer 17

Non-polar amino acids are lipid-soluble, and therefore can pass through the phospholipid bilayer. Polar amino acids, and other water soluble substances must be “carried”.

Question 18

Outline significance of polar and non-polar amino acids in terms of the active site

Answer 18

Polar amino acids in the active site of an enzyme allow chemical interaction between the substrate and enzyme to form an activated complex. This transitional state allows the weakening of internal molecular structure and therefore the reduction of activation energy.

Question 19

State six functions of proteins

Answer 19

Structure
Hormones
Immunity
Transport
Movement
Enzymes

(SHIT ME)

Question 20

Give an example of a structural protein

Answer 20

Keratin

Question 21

Give an example of a hormone protein

Answer 21

Insulin

Question 22

Give an example of an immunity protein

Answer 22

Antibodies

Question 23

Give an example of a transport protein

Answer 23

Haemoglobin

Question 24

Give an example of a movement protein

Answer 24

Actin

Question 25

Give an example of an enzyme protein

Answer 25

Catalse