BioChem 2.4 Proteins

Question 1

What are biological proteins composed of?

Answer 1

Biological proteins are made up of 20 different types of amino acids.

Question 2

Where do our cells get the amino acids?

Answer 2

Amino acids can be found through our diet and nutrients. Some amino acids can also be synthesized by human cells.

Question 3

How are amino acids considered polar or nonpolar?

Answer 3

Whether amino acids are polar or nonpolar depends on their variable group (R group). Polar makes them hydrophilic. Non Polar makes them hydrophobic.

Question 4

How does the polarity of an amino acid affect enzyme solubility?

Answer 4

The outer layer of an enzyme contains polar (hydrophilic) amino acids. This helps to make the enzyme soluble.

Question 5

How does the polarity of an amino acid affect membrane proteins?

Answer 5

The inner pore of a membrane channel will contain polar amino acids, while the amino acids in contact with the lipid bilayer will be nonpolar. This keeps the protein from floating away.

Question 6

How does the polarity of an amino acid affect proteins stability?

Answer 6

The inner layer of proteins will contain many non polar amino acids that help to stabilize the shape of a soluble protein.

Question 7

Where do most organisms assemble their proteins from?

Answer 7

Most organisms have proteins that consist of the same 20 amino acids. There are a few exceptions that are likely to come from distant evolutionary relatives.

Question 8

How do amino acids link together?

Answer 8

Amino acids link through condensation reaction, forming a peptide bond to make a dipeptide or polypeptide.

Question 9

How are amino acids joined together in cells?

Answer 9

In cells, amino acids are joined by free ribosomes or by ribosomes attached to the RER.

Question 10

What is the significance of the sequence of amino acids in polypeptides in living organisms?

Answer 10

The sequence of amino acids in polypeptides are codes for the genes.

Question 11

What is the primary structure of protein structure?

Answer 11

Primary structure is a sequence of amino acids. The molecule is called a polypeptide.

Question 12

What is the secondary structure of protein structure?

Answer 12

Secondary structure is the folding of the polypeptide to a combination of spiralled alpha helices and pleated beta sheets. They are held together by hydrogen bonds.

Question 13

What is the tertiary structure of protein structure?

Answer 13

Tertiary structure is the chain folding into a specific 3D structure. The structure is held together by a number of different kinds of bonds.

Question 14

What is the quaternary structure of protein structure?

Answer 14

A quaternary structure does not always occur. This occurs when two or more proteins in tertiary structure are bonded together to make 1 molecule.

Question 15

What does the quaternary structure involve to form a conjugated protein?

Answer 15

To form a conjugated protein, the quaternary structure involves the binding of a prosthetic group.

Question 16

What is the difference between fibrous proteins and globular proteins?

Answer 16

Fibrous proteins such as keratin which is found in hair is linear. While globular proteins such as pepsin are round.

Fibrous proteins such are Keratin are insoluble. Other, globular proteins such as pepsin are soluble in water

Fibrous proteins are less sensitive to changes in temperature and pH. Globular proteins are more sensitive.

Fibrous proteins perform structural roles. Globular proteins act as catalysts.

Question 17

What is proteome?

Answer 17

Proteome is the sum of all the proteins in one biological individual. This differs and is unique for every individual as we do not make the same amount of proteins.

Question 18

What is the role of rubisco?

Answer 18

Rubisco is the enzyme that catalyzes carbon fixation in green plants. This is a key event in photosynthesis.

Question 19

What is the role of insulin?

Answer 19

Insulin is hormone involved in the regulation of blood glucose concentration. It is composed of 2 peptides chains and totalling 51 amino acids.

Question 20

What is the role of immunoglobulins?

Answer 20

Immunoglobulins act for defence as antibodies which are large Y-shaped proteins that are used by the immune system to identify and neutralize foreign objects such as bacteria and viruses.

Question 21

Are immunoglobulins fibrous or globular?

Answer 21

Immunoglobulins are globular.

Question 22

What is the role of collagen?

Answer 22

Collagen is composed of three interwoven polypeptide chains, and is found in fibrous tissues such as tendons, ligaments, skin, bones and blood vessels. It serves to help our structure and support body tissues.

Question 23

Is collagen fibrous or globular?

Answer 23

Collagen is fibrous.

Question 24

What are some functions of protein?

Answer 24

• catalyst
• muscle contraction
• cytoskeletons
• tensile strengthening
• blood clotting
• transport of nutrients and gases
• cell adhesion​
• membrane transport
• hormones
• receptors
• packing of DNA
• immunity

Question 25

What is the protein function of an enzyme?

Answer 25

catalyze

Question 26

Where are the functions of myosin and actin involved?

Answer 26

muscle contraction

Question 27

What kind of protein function do tubulins show?

Answer 27

cytoskeletons

Question 28

What is an example of tensile strengthening as a protein function?

Answer 28

fibrous proteins give tensile strength to skin, tendons, ligaments and blood vessel walls

Question 29

What is an example of a protein function for blood clotting?

Answer 29

plasma proteins act as clotting factors

Question 30

Example of a protein that carries nutrients or gases

Answer 30

Haemoglobin

Question 31

What are membrane proteins examples for protein functions?

Answer 31

• cell adhesion
• membrane transport