U8

Question 1

what protein source has the best nutritive value in terms of amino acid balance

Answer 1

egg

Question 2

how are milk proteins categorized

Answer 2

casein and whey

Question 3

casein

Answer 3

isoelectric point 4.5 - isolated when milk’s pH has this value

Question 4

whey

Answer 4

left in solution after casein removed

Question 5

when is casein insoluble

Answer 5

in weakly acidic media - 4.5

Question 6

what kind of protein is casein

Answer 6

phosphoprotein

Question 7

where is the phosphate attached in casein

Answer 7

serine amino acid

Question 8

what are submicelles

Answer 8

aggregates of the casin fractions (a,b,g,k)

Question 9

what are micelles

Answer 9

aggregates of submicelles, hydrophobic on the inside and hydrophilic k-casein on the outside

Question 10

what do micelles protect from happening

Answer 10

coagulation into curds - cheese production

Question 11

what are serum caseins

Answer 11

monomers of casein - rare

Question 12

what does the extent of aggregation depend on

Answer 12

ca concentration and pH

Question 13

what precipitates in the presence of casein and what doesnt

Answer 13

k casein doesnt, everything else does

Question 14

when are micelles formed

Answer 14

only in the presence of Ca. can break and reform depening on levels

Question 15

why is milk white and opaque

Answer 15

micelles cause light scattering

Question 16

true or false: micelles are solvated and porous

Answer 16

true! k-casein is polar, so till attract water

Question 17

how are rennin and chymosin differen

Answer 17

theyre not silly

Question 18

where is rennin from

Answer 18

the 4th stomach of a suckling calf

Question 19

how does rennin/chymosin work

Answer 19

it targets the 105-phe and 106-met peptide bond, cleaving it and resulting in para-k-casein and glycomacroprotein

Question 20

what happens when para-k-casein is formed

Answer 20

it isn’t soluble, so it precipitates with the other hydrophobic caseins, coagulating and forming a curd

Question 21

is glycomacroprotein soluble or insoluble

Answer 21

soluble - stays

Question 22

a-1-casein: phosphoserine

Answer 22

8 phosphoserine residues, centralized in 43-80AAs with 12 carboxyl groups - polar region

Question 23

a-1-casein: self-associating tendency

Answer 23

due to hydrophobic side chains in residues 100-199

Question 24

a-1-casein: proline

Answer 24

distributed all along chain

effects: no crystallization and hindered secondary structure

Question 25

what happens to a-1-casein in the presence of Ca

Answer 25

forms in insoluble ca-salt

Question 26

how does the molecular structure of alpha-2-casein effect its properteis

Answer 26

dipolar - cationic C and anionic N

Question 27

which precipitates more easily, alpha1casin or alpha2casein

Answer 27

alpha2casein

Question 28

which casein is the most hydrophobi

Answer 28

b

Question 29

b casin phosphoserines

Answer 29

5 localized in1-40 range

Question 30

where are the ionizable sites in b casein

Answer 30

1-40 range

Question 31

where are the nonpolar sites in b

Answer 31

139-209

Question 32

where are beta sheets created in the chain and why do we know this

Answer 32

a-periodic part. in response to higher temperatures, there are more b sheets but no decrease in a helix

Question 33

where are the cysteines in b

Answer 33

none | !

Question 34

does b self-associate

Answer 34

no

Question 35

at what level of ca does b casein precipitate

Answer 35

milk-levels

Question 36

what are gamma caseins

Answer 36

degraded b-caseins

Question 37

molecular structure of k-casein

Answer 37

horse and rider model

Question 38

n terminus of k-casin

Answer 38

hydrophobic - interacts with other casein

Question 39

when is the monomer of k-casein accessible and what is it

Answer 39

only under reducing conditions. it is 2 cysteine residues

Question 40

why does k-casein self-associate

Answer 40

forms disulfide bonds between cys

Question 41

how does k-casein protect the other caseins

Answer 41

Aggregates with the other caseins to prevent their coagulation in the presence of Ca ions – forms stable casein complexes and casein micelles

Question 42

what are the hairs on k-casein

Answer 42

hydrophilic c-terminal domain

Question 43

what is acid coagulation

Answer 43

addition of acids or lactic acid fermentation to change the pH to 4.2-4.6

Question 44

what is the most prevalent protien in whey? 2nd most?

Answer 44

1. b-lactoglobulin | 2. a-lactalbumin

Question 45

what is the difference between the A and B variants of b-lactoglobulin

Answer 45

a- aspartic acid | b-glycine

Question 46

how many disulfide bonds and free sulfhydryl groups in b-lactoglobuion

Answer 46

2 disulf | 1 free sulfhydryl

Question 47

when does the b-lactoglobulin exist as a monomer

Answer 47

pH lower thand 3 or higher than 8

Question 48

when does the lactoglobulin exist as an octamer

Answer 48

3.1-5.1 pH

Question 49

when is it a dimer

Answer 49

any other pH

Question 50

why does the b-lactoglobulin oligoerize

Answer 50

carboxyl groups | a variant forms more readily

Question 51

how many disulfide links in a-lactalbumin

Answer 51

4

Question 52

what enzyme does a-lactalbumin effect

Answer 52

galactosyl transferase

Question 53

what is different about a-lactalbumin's heat sensitivity

Answer 53

more stable when in the presence of calcium

Question 54

how does bovine serum albumin enter milk

Answer 54

through the blood stream, not made in the mammary gland

Question 55

what are hydrolysates

Answer 55

made by enzymatic treatment of whey protein isolates - broken down proteins into smaller portions