2.7 Proteins

Question 1

what is the function of proteins (3)?

Answer 1

-they are structural building blocks

-help cellular functions such as immune defence, cell-to-cell transport, oxygen transport

-genetic operations such as growth, repair, and protection

Question 2

what is the subunit of a protein?

Answer 2

amino acid

Question 3

what is the structure of an amino acid?

Answer 3

an organic molecule that has a central carbon atom attached to an amino group, a carboxyl group, a hydrogen atom and a side chain

Question 4

why are amino acids amphoteric?

Answer 4

amino acids are amphoteric because they can act both as an acid and a base

Question 5

how can you tell if an amino acid is nonpolar?

Answer 5

-electronegativity is less than 0.4

-is sulphur or nitrogen is present within the structure not at the bottom

Question 6

how can you tell if an amino acid is polar?

Answer 6

• the R group contains sulfur, nitrogen, and/or oxygen at the bottom because these electrons have a higher electronegativity so they draw atoms toward them a.k.a the SNO rule

Question 7

how can you tell if an amino acid is electrically charged and acidic?

Answer 7

there is a negative charge in the R groups because acids donate H+ ions to solutions

Question 8

how can you tell if an amino acid is electrically charged and basic?

Answer 8

the R group has a positive charge because it accepts H+ ions from solutions

Question 9

how many amino acids are essential?

Answer 9

9

Question 10

what does the protein’s primary structure look like?

Answer 10

a chain of 50 amino acids linked by peptide bonds

types of amino acids present and the sequence varies from one protein molecule to the next

Question 11

what chemical bond is involved in the primary protein structure?

Answer 11

an amide linkage forms between the miano group from one amino acid and the carboxyl group from an adjacent amino acid

Question 12

what does the protein’s secondary structure look like?

Answer 12

one or more polypeptide chains individually coiled into an alpha helix or a non-helical structure called a beta pleated sheet.

Question 13

how is the chemical bond formed in the alpha helix in the secondary structure?

Answer 13

bonds form between the carboxyl group of one amide linkage and the hydrogen of one amino group, four amide linkages away

Question 14

how are the chemical bonds formed in the beta-pleated sheets in the secondary structure?

Answer 14

two parts of the polypeptide chain lie parallel and hydrogen bonds form between the oxygen from a carbonyl and a hydrogen atom from an amino group

Question 15

what does the protein’s tertiary structure look like?

Answer 15

a further folded version of the coiled alpha helices and beta pleated sheets

Question 16

what are the chemical bonds involved in the tertiary protein structure?

d, h, i, p, v

Answer 16

1. Disulfide bridges between two cysteine
2. hydrogen bonds form between two polar groups
3. ionic bonds form between a positive and negative side chain
4. Proline kink swirls
5. van der wall forces form between two non-polar groups

Question 17

what does the protein’s quaternary structure look like?

Answer 17

the assembly of two or more tertiary, sub-units

Question 18

what bonds are involved in the quaternary structure?

Answer 18

the same types of bonds in the tertiary structure

Question 19

the highly specific bonds that are established during protein formation can be disrupted by a variety of environmental changes such as

Answer 19

-temperature (particularly high temperature)

-ph

-ion (salt) concentration

Question 20

what is protein denature caused by?

Answer 20

denature which is the unravelling of a protein structure due to the disruption of H-bonds, ionic bonds, disulfide bridges, and hydrophobic interactions