proteins

Question 1

what are proteins and what are they made up of

Answer 1

Proteins are polymers, they’re made up of one or more polypeptide

Question 2

What is a dipeptide

Answer 2

dipeptide is formed when two amino acids join together.

Question 3

what is a polypeptide

Answer 3

A polypeptide is formed when more than two amino acids join together.

Question 4

What are amino acids in proteins

Answer 4

monomers

Question 5

What are the four protein structural levels

Answer 5

Primary
Secondary
Tertiary
Quaternary

Question 6

describe the proteins primary structure

Answer 6

this is the sequence of amino acids in the polypeptide chain.
Different proteins have different sequences of amino acids in their primary structure
A change in just one amino acid may change the structure of the whole protein.

Question 7

Describe the secondary structure of a protein

Answer 7

the polypeptide chain doesn’t remain flat and straight. Hydrogen bonds form between nearby amino acids in the chain. This makes it automatically coil into an alpha (o) helix or fold into a beta (B) pleated sheet - this is the secondary structure.

Question 8

Describe the tertiary structure

Answer 8

the coiled or folded chain of amino acids is often coiled and folded further. More bonds form between different parts of the polypeptide chain For proteins made from a single polypeptide chain, the tertiary structure forms their final 3D structure.

Question 9

Describe the quaternary structure

Answer 9

some proteins are made of several different polypeptide chains held together by bonds.
The quaternary structure is the way these polypeptide chains are assembled together. E.g. haemoglobin is made of four polypeptide chains, bonded together. For proteins made from polypeptide
chain more than one polypeptide chain, the quaternary structure is the protein’s final 3D structure.

Question 10

What bond holds together the primary structure

Answer 10

peptide bonds between amino acids.

Question 11

What bond holds together the secondary structure

Answer 11

held together by hydrogen bonds

Question 12

What bond holds together the tertiary structure

Answer 12

this is affected by a few different kinds of bonds:

•ionic bonds. These are attractions between negatively-charged R groups and positively-charged R groups on different parts of the molecule.
•Disulfide bonds. Whenever two molecules of the amino acid cysteine come close together, the sulfur atom in one cysteine bonds to the sulfur in the other cysteine, forming a disulfide bond.
•Hydrophobic and hydrophilic interactions. When hydrophobic (water-repelling) R groups are close together in the protein, they tend to clump together. This means that hydrophilic (water-attracting) R groups are more likely to be pushed to the outside, which affects how the protein folds up into its final structure.
• Hydrogen bonds - these weak bonds form between slightly positively-charged hydrogen atoms in some R groups and slightly negatively-charged atoms in other R groups on the polypeptide chain.

Question 13

What determines the bond of the quaternary structure?

Answer 13

this tends to be determined by the tertiary structure of the individual polypeptide chains being bonded together. Because of this, it can be influenced by all the bonds mentioned above.

Question 14

describe a globular protein

Answer 14

globular proteins hydrophilic R groups on the amino acids tend to be pushed to the outside of the molecule. This is caused by the hydrophobic and hydrophilic interactions in the protein’s tertiary structure This makes globular proteins soluble, so they’re easily transported in fluids.

Question 15

what are the functions globular proteins have in living organisms

Answer 15

HAEMOGLOBIN
INSULIN
AMYLASE

Question 16

haemoglobin is a globular protein, what does it do?

Answer 16

HAEMOGLOBIN is a globular protein that carries oxygen around the body in red blood cells, It’s known as a conjugated protein , this means it’s a protein with a non-protein group attached. The non-protein part is called a prosthetic group. Each of the four polypeptide chains in haemoglobin has a prosthetic group called haem. A haem group contains iron, which oxygen binds to.

Question 17

What is the function of insulin as a globular protein?

Answer 17

INSULIN is a hormone secreted by the pancreas. It helps to regulate the blood glucose level.
Its solubility is important - it means it can be transported in the blood to the tissues where it acts.
An insulin molecule consists of two polypeptide chains, which are held together by disulfide bonds

Question 18

What is amylase as a globular protein?

Answer 18

AMYLASE is an enzyme that catalyses the breakdown of starch in the digestive system. It is made of a single chain of amino acids. Its secondary structure contains both alpha-helix and beta-pleated sheet sections. Most enzymes are globular proteins.

Question 19

What are fibrous Proteins?

Answer 19

Fibrous proteins are insoluble and strong. They’re structural proteins and are fairly unreactive (unlike many globular proteins)

Question 20

What are the three types of fibrous proteins?

Answer 20

Collagen
Keratin
Elastin

Question 21

What is collagen

Answer 21

Collagen - found in animal connective tissues, such as bone, skin and muscle. It is a very strong molecule. Minerals can
bind to the protein to increase its rigidity, e.g. in bone.

Question 22

What is keratin

Answer 22

Keratin - found in many of the external structures of animals, such as skin, hair, nails, feathers and horns. It can either be flexible (as it is in skin) or hard and tough (as it is in nails).

Question 23

What is elastin

Answer 23

found in elastic connective tissue, such as skin, large blood vessels and some ligaments. It is elastic, so it allows tissues to return to their original shape after they have been stretched.