Amino Acids, Peptides, and Proteins

Question 1

Fibrous Proteins

Answer 1

• have polypeptide chains organized in long fibers/sheets
• physically tough, but can still be slightly stretchy
• water insoluble

Question 2

Structural proteins

Answer 2

• Fibrous protein that functions in support
• Collagen and elastin are used in tendons and ligaments of animals
• Silk fibers for insect webs
• Keratin is found in hair horns and feathers

Question 3

Contractile

Answer 3

• Fibrous protein that specializes in movement
• Actin and myosin contract in order to form a cleavage furrow and allow muscles to move
• Move cilia and flagella

Question 4

Globular Proteins

Answer 4

• Chains folded into compact, rounded shapes
• Extremely soluble in aqueous solutions
• Can act as storage protein fo AAs
• Can act as transport protein (ex: hemoglobin)
• Can act as enzymes

Question 5

Amino Acids

Answer 5

Amino acid sequence, composition, and amount help distinguish proteins from one another (i.e determine primary protein structure and in turn protein function)

Question 6

General amino acid structure

Answer 6

central (alpha) carbon, amino group, carboxylate group, H atom, R group

Question 7

Immune system proteins

Answer 7

• globular proteins

- antibodies help fight bacteria and viruses

Question 8

Peptides

Answer 8

Amino acid polymers of 50 or less

Question 9

Polypeptides/protein

Answer 9

Amino acid polymers greater than 50

Question 10

Phenylalanine (Phe)

Answer 10

• Essential
• Nonpolar
• R group is benzene derivative

Question 11

Valine (Val)

Answer 11

• Essential
• Nonpolar
• R group is CH connected to two methyl groups

Question 12

Threonine (Thr)

Answer 12

• Essential
• Polar
• R group is C connected to H, CH3 and OH
• Contain hydroxyl

Question 13

Methionine (Met)

Answer 13

• Essential
• Nonpolar
• R group is 2 CH2’s then S then CH3

Question 14

Leucine (Leu)

Answer 14

• Essential
• Nonpolar
• R group is CH2 connected to CH connected to 2 CH3’s

Question 15

Isoleucine (Ile)

Answer 15

• Essential
• Nonpolar
• R group is C connected to H and CH3 and CH2 connected to CH3

Question 16

Lysine (Lys)

Answer 16

• Essential
• Basic
• Polar
• R group is 4 carbon chain with NH+

Question 17

Histidine

Answer 17

• Essential
• Basic
• Polar
• R group is CH2 connected to pentagonal shape with N and C
• Weak base because only alpha NH3+ is protonated

Question 18

Arginine

Answer 18

• Conditional
• Basic
• Polar
• R groups is 3 carbon chain with last C connected to N connected to H and C connected to NH2 and double bonded to NH2+

Question 19

Zwitterions

Answer 19

• Neutral form of amino acid
• Exist at different pH’s for different amino acids depending on pKa
• R group primarily gives amino acid its unique properties

Question 20

Amino acid classes

Answer 20

Classified by R groups ability to interact with water

Question 21

Titration of amino acids

Answer 21

-Free amino acids contain ionizable groups, form depending on pH

Question 22

pI

Answer 22

Isoelectric point; average of two pKas either side of zwitterion

Question 23

Good buffers

Answer 23

• Weak acids or bases
• Best in solutions within 1 pH unit on either side of one of their pKa values
• Higher buffer concentration= greater buffering capacity

Question 24

Bonds broken when protein denatures

Answer 24

• Hydrogen bonds
• Hydrophobic interactions
• Salt bridges

Question 25

Lipid functions

Answer 25

- Key source for endurance activities - Insulation and water resistance - Components of biomembranes - Derivatives of other biomolecules

Question 26

Saturated fatty acids

Answer 26

- Highly flexible molecules; free C-C rotation - Fully extended conformation is most stable due to least amount of steric hindrance - As molecular mass increases, so does melting point