(7) Protein

Question 1

protein definition

Answer 1

macromolecule (polypeptides) that’s composed of amino acids liked to each other by peptide bonds

Question 2

mention the origins of protein

Answer 2

plant origin: vegetables (soybeans, legumes)
anima origin: meat, fish, chicken, etc

Question 3

shape types of protein

Answer 3

globular, fibrous, conjugated

Question 4

function of protein for the body

Answer 4

regulator, builder, biological activities (hormone, enzymes,…)

Question 5

ideally, how much protein should you have per day

Answer 5

1 gram/ body weight

Question 6

amino acid definition

Answer 6

an organic compound that contains both an amino (-NH2) and carboxylic acid (-COOH) functional group.

*both func. groups are tied to carbon with alpha bond (a-carbon, a-amino, a-hydrogen)

Question 7

amino acid is amphoteric, meaning…

Answer 7

it can act as an acid or base

Question 8

what functional group in amino acid makes them different from one another

Answer 8

the -R group

Question 9

what are the categories of -R group attached

Answer 9

non-polar alipathic group
polar uncharged group
aromatic group
positive/negative ionic group

Question 10

what does non-polar alipathic -R group means and give examples

Answer 10

the R group is hydrophobic and non-polar

*glycine, alanine, valine, leucine, methonine, isoleucine

Question 11

what does polar uncharged -R group means and give examples

Answer 11

the R group contains hydroxyl or amino groups. they have hydrophilic properties

*serine, threonine, cysteine, proline, asparagine

Question 12

what does aromatic -R group means and give examples

Answer 12

the R group is composed of aromatic or N ring structure

*phenylalanine, tyrosine, tyrptophan

Question 13

what does positively charged -R group means and give examples

Answer 13

the R group has an amide group and can form positive ions ph< 7.0

*lysine, argininem hystidine

Question 14

what does negatively charged -R group means and give examples

Answer 14

the R group has a COOH group that can form negative ions ph>7.0

*aspartic acid, glutamic acid

Question 15

what is essential amino acid

Answer 15

amino acids that can’t be synthesized by our body but are required in our diet

*isoleucine, leucine, methionine, phenylalanine, threonine, triptophan, valine, lysine, hystidine (child), arginine (infant)

Question 16

isomer definition

Answer 16

compounds that have the same molecular formula but are structurally different

Question 17

two optical isomes/mirror images of each other molecules that exhibit handedness are said to be …… and the mirror images are referred to as ……..

Answer 17

chiral, enantiomers

Question 18

what’s the isomer of D-alanine

Answer 18

L-alanine

Question 19

what is isoelectric point and how does it relate with amino acid

Answer 19

the ph at which a molecule carries no electrical charge

*it also means that the Ph of whichamino acid molecule is uncharged

Question 20

what is pka : ph in amino acid

Answer 20

50% ionized : 50% unionized

Question 21

protein have the potential to function as an acid or a base, depending on the ph. this is the definition of amino acid properties

Answer 21

amphoteric

Question 22

what is polymerization

Answer 22

a process where monomers combine together to produce a polymer

Question 23

how many polymerization type

Answer 23

dipeptide, oligopeptide, polypeptide, protein

Question 24

what type of bond connects the monomers in a polymer

Answer 24

peptide bond

Question 25

what is a peptide bond

Answer 25

covalent bonds that connects the amine (-NH2) of AA1 and carboxyl group (-COOH) of AA2

Question 26

mention some properties of peptide bonds

Answer 26

• peptide bonds are shorter and stronger than C-C bonds, but weaker than C=C
• cannot rotate freely
• when peptide bond is formed, one water molecule is released (condensation polymerization)

*diagram on page 17 on week 7

Question 27

explain the different structures of protein

Answer 27

primary structure= linear sequence from N terminal to C terminal
secondary= alpha helix & beta sheets
tertiary= 3d conformational shape & shape is usually globular
quartenary= 2 or more different polypeptides in a 3d space

*see diagram on page 17 week 7

Question 28

difference between alpha helix and beta sheet

Answer 28

alpha helix= the carbonyl (C=O) of one amino acid is hydrogen bonded to the H (N-H) of an amino acid that’s four down the chain. shape is spiral.

b-pleated sheet= two or more segments of polypeptides chain line up next to another. shape is sheet-like structure.

Question 29

what kind of bonds chains the polypeptides together in a tertiary structure

Answer 29

hydrogen bond, ionic bond, hydrophobic interaction, disulfide bond

Question 30

the different types of protein

Answer 30

globular protein= spherical in their tertiary structure. (albumin, globulin, histone, protamines)
fibrous protein= insoluble, elongated protein molecules (collagen , elastin)
conjugated protein= protein combined with some other type of compound, carbo or lipids. (lipoprotein, metalloprotein, nucleoprotein, phospoprotein)

Question 31

effects of food process or storage to protein

Answer 31

• denaturation (by heating) -> change in solubility
• oxidation (catalyzed by light) -> change in flavor
• enzymatic degradation -> change in texture and flavor
• freezing -> change in conformation and solubility

Question 32

explain protein denaturation

Answer 32

distruption and possible destruction of both secondary and tertiary structure. it uncoils the conformation into a random shape.

*primary structure are not affected because denaturation only affect peptide bond (primary structure is only a sequence of amino acid)

Question 33

what are the physical observation during denaturation process

Answer 33

precipitation or coagulation of protein

Question 34

what bonds are broken down during unfolding of structure (denaturation)

Answer 34

hydrogen bonds. covalent bonds are undistrupted

Question 35

what happens to protein functional properties during denaturation

Answer 35

functional properties are changed

Question 36

daily examples of protein denaturation in food

Answer 36

frying eggs and warming milk

Question 37

factors of protein denaturation

Answer 37

heat, alcohol, acid or base, heavy metals, reducing agents

Question 38

physicochemical properties of proteins

Answer 38

• hydration (water holding capacity and viscous forming
• solubility (important for extraction process)
• thickener
• gelling agent (important for processed meat and fish products)
• texture (heat coagulation and film forming. fiber structure in meat)

Question 39

food application of physicochemical properties of proteins

Answer 39

• emulsifier
• foam forming (foam of egg whites)
• dough forming (viscoelatic gluten protein in bread)
• maillard reaction (sugar and protein/amino acid)

Question 40

how does viscosity affect protein

Answer 40

viscosity of a protein solution is increased by denaturation of protein

Question 41

functional properties of proteins in relation with water

Answer 41

wet ability, swelling, rehydration, water holding, solubility

Question 42

functional properties of proteins in relation with water and proteins

Answer 42

viscosity, gelling, fiber forming, dough forming

Question 43

functional properties of proteins in relation with lipids/gases

Answer 43

emulsification, foaming ability, foam stabilization

Question 44

characteristics affected by food proteins

Answer 44

hydration, taste, appearance, viso-elasticity

Question 45

what is protein gelation

Answer 45

gelation is a result of denaturation. it’s a 3d network of protein fibers that develops high structural rigidity.

the gel matrix of protein can hold water, fat, and other food ingredients (gelatin desserts, tofu, yoghurt)

Question 46

what is the water holding capacity of protein

Answer 46

the ability of protein to bind water is related with the presence of hydrophilic and charged groups in the structure (meat retains water when cut, heat, or grinding)