Topic 2.3: Proteins

Question 1

proteins always contain the elements….

Answer 1

C (carbon)
H (hydrogen)
O (oxygen)
N (nitrogen)
sometimes: S (sulfur)

Question 2

why may proteins contain the element S sometimes?

Answer 2

S is found in certain R groups of amino acids (methionine and cysteine)

Question 3

How many different amino acids are there?

Answer 3

20 different amino acids

Question 4

what does an R group do

Answer 4

determines an amino acid’s chemical properties and is, therefore, responsible for the 3D shape of proteins

Question 5

2 groups of an amino acid

Answer 5

amino group and carboxyl group

Question 6

which bond forms between 2 amino acids by condensation?

Answer 6

peptide bond

Question 7

opposite of condensation

Answer 7

hydrolysis

Question 8

4 levels of protein structure

Answer 8

primary, secondary, tertiary, quaternary

Question 9

which levels of protein structures are functional?

Answer 9

tertiary and quaternary

Question 10

polymer of amino acids

Answer 10

polypeptide

Question 11

description of primary structure

Answer 11

a chain of amino acids linked by peptide bonds

Question 12

bonds involved in primary level structure

Answer 12

peptide bond (C-N)

Question 13

secondary level structure description

Answer 13

coiling (alpha-helix)

or

folding (beta-pleated sheet)

Question 14

bonds involved in secondary level structure

Answer 14

hydrogen bonds (between non-adjacent carboxyl and amino groups)

Question 15

tertiary level structure description

Answer 15

further coiling/folding of the secondary structure to form a precise 3-D shape

Question 16

bonds involved in tertiary level structure

Answer 16

1. hydrogen bonds
2. hydrophobic interactions
3. ionic bonds
4. disulfide bridges

Question 17

quaternary level structure description

Answer 17

the association of 2 or more tertiary level proteins

Question 18

bonds involved in quaternary level structure

Answer 18

1. disulfide bridges
2. ionic bonds
3. hydrophobic interactions
4. hydrogen bonds

Question 19

protein denaturation

Answer 19

the unfolding or alteration in conformation of a protein that causes it to lose its precise 3D shape and becomes inactive

Question 20

shape of globular protein

Answer 20

spherical, globe like

Question 21

functions of globular proteins

Answer 21

involved in cell processes like catalysis (enzymes), transport, signaling (ligands/hormones)

Question 22

solubility of globular proteins

Answer 22

they are soluable because their hydrophilic R-groups are exposed and their hydrophobic R-groups are hidden in the core of the sphere

Question 23

shape of fibrous protein

Answer 23

long/elongated, rope-like

Question 24

function of fibrous proteins

Answer 24

provide structural support in tissues like hair, skin, and tendons

Question 25

solubility of fibrous proteins

Answer 25

insoluble in water because their hydrophobic R groups cannot be hidden, they're exposed to the surface

Question 26

hemoglobin structure

Answer 26

- quaternary level protein(globular) - made of 4 polypeptide chains - 2 alpha-globin chains - 2 beta-globin chains - each chain has a gene group associated with it, the iron ion in each heme group binds to one oxygen molecule

Question 27

function of hemoglobin

Answer 27

- transports O2 in red blood cells - each hemoglobin can bind to/carry 4 O2 molecules (8 oxygen atoms)

Question 28

can hemoglobin dissolve in the cytoplasm

Answer 28

Yes, because it is globular, therefore soluble.

Question 29

why is it important for hemoglobin to dissolve in the cytoplasm of red blood cells

Answer 29

- important for proper functioning of red blood cells - if hemoglobin was not soluble, the molecules stick together and distort the shape of RBC's (they become sickle-shaped) - this causes the RBC's to get stuck in small blood vessels, creating blockages that prevent O2 delivery to the tissues

Question 30

collagen structure

Answer 30

- quaternary level structure (fibrous) - made of 3 polypeptide chains - at primary level structure, almost every third amino acid is glycine - many collagen molecules ---> fibrils ---> lay side by side ---> collagen fibers

Question 31

function of collagen

Answer 31

plays a structural role in skin, bones, tendons, teeth, cartilage, and the walls of blood vessels

Question 32

how does every third amino being glycine affect the function?

Answer 32

glycine is a nonpolar amino acid making the surface of collagen hydrophobic

Question 33

why is it important for collagen to be insoluble

Answer 33

gives it flexibility and tremendous tensile strength (the ability to withstand large pulling forces without permanently stretching out or breaking)