Proteins

Question 1

What is the structure of amino acids?

Answer 1

The amino group - stays the same in each amino acid.

Carboxyl group - stays the same in each amino acid.

R-group - different in each amino acid. Also, defines an amino acid.

Question 2

What is the r-group in an amino acid?

Answer 2

• represents side chaines
• from the central carbon atom
• different in each amino acid from a simple Hydrogen atom to a complex ring structure.

Question 3

What are the main properties of globular proteins?

Answer 3

• hydrophilic r-groups push out
• soluble so easily transported in fluids
• round and compact
• examples are haemoglobin, insulin, amylase and catalase.

Question 4

What is the structure and function of hameoglobin?

Answer 4

• carries oxygen in red blood cells around the bdoy
• conjugated protein (protein with a non-protein group attached)
• 4 polypeptide chains each with Heam (prosthetic group = a non-protein group)
• Haem has iron ions which combine with the Oxygen in Haemoglobin.

Question 5

What is the structure and function of insulin?

Answer 5

• a hormone secreted by the pancreas
• regulates blood glucose levels
• 2 polypeptide chains held together by disulfide bonds
• soluble so easily transported in the blood to the tissues where it acts.

Question 6

What is the structure and function of Amylase?

Answer 6

• an enzyme that catalyses the breakdown of starch in the digestive system
• made up of a single chain of amino acids
• secondary structure has sections of alpha helix and beta-pleated sheets

Question 7

What is the structure and function of Catalse?

Answer 7

• an enzyme that catalyses the breakdown of Hydrogen Peroxide which is harmful to cells
• quarternary strcuture has 4 prosthetic haem groups

Question 8

What is the structure and function of fibrous proteins?

Answer 8

• long, rope-like fibres
• structural proteins and fairly unreactive
• parallel polypeptide chains held together by cross-links
• soluble and strong (high tensile strength)

Question 9

What is the structure and function of Collagen?

Answer 9

• very strong molecule
• found in animal connective tissue (skin, bone, muscle)
• minerals can bind to it to increase rigidity (in bones)

Question 10

What is the structure and function of keratin?

Answer 10

• in external structures of an animal (hair, skin, nails)
• flexible (in skin) OR hard/tough (in nails)
• many sulfur atoms in amino acids which make it durable

Question 11

What is the structure and function of elastin?

Answer 11

• in elastic connective tissue (ligaments, large blood vessels)
• elastic allows it to return to its original shape after stretching

Question 12

How do proteins denature?

Answer 12

• bonds that maintain a proteins shape are broken so protein stop working properly tehrefore the protein is denatured
• changes in the temperature, pH and salt concentration can denature a protein
• specific conditions can vary from protein to protein
• when denatured, fibrous proteins lose structural strength but globular proteins become insoluble and inactive