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Advanced Food Science > Lecture 9 > Flashcards

Lecture 9 Flashcards

1
Q

What is the structure of an AA?

A

central C attached to Amino group, R group and Acrboxylic acid group

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2
Q

What % of C,O,N,H,S is in proteins?

A 
Carb 50%
O 22%
N 16%
H 7% 
S little
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3
Q

What is protein condensation?

A

When 2 AA come together, carboxylic acid and AA from 2 different groups come together and release 1 molecule of water to form a dipeptide

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4
Q

What is the bond that connects 2 AAs?

A

Peptide bond is the bond between the AA

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5
Q

What is a hybrid or twitter ion?

A

AA that is ampthoteric

-AA can carry +/- charge at the same time on same molecule

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6
Q

What happens to a twitter ion when pH increases or decreases?

A

Low ph will appear in acid form
-net charge +

Increase ph go to basic form
-net chargee is -1

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7
Q

What are the characteristics of acid coagulation of casein?

A

Fresh Milk  pH ~ 6.6  “Colloidal Suspension”

Net Negative Charge on Casein

Add Acid Coagulation (Protein Denaturation)

Iso-electric point of casein: PI = 4.6 net charge = 0

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8
Q

What situation would be desireable/undesireable use of acid coagulation of casein?

A

Desireable if you want yogurt you want coagualtion of casein or in cheese

Undesirable curdling of milk in a smoothie

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9
Q

What are the uncharged R groups of AAs?

A

Serine
Threonine
Cysteine
Glyceine

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10
Q

What are the negatively charged AAs?

A

Aspartate

Glutamate

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11
Q

What is the one positively charged AA?

A

Lysine

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12
Q

What are the non polar R groups?

A

Methionine
Phenylalanine
Alanine
Valine

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13
Q

What are the essential AAS?

A 
Valine
Leucine
Isoleucine
Phenylalanine 
Tryptophan 
Lysine
Arginine
Histidine
Methionine
Threonine
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14
Q

What are the R groups for Gly, Asp, Set, Lys, Ala, Phe, Cys, Glu?

A 
Gly: R= H
Asp: R = CH2COOH
Ser: R = CH2OH
Lys: R = CH2-CH2-CH2-CH2- NH2
Ala: R = CH3
Phe: R = CH2=Benzene ring
Cys: R = CH2SH
Glu: R = CH2-CH2-COOH
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15
Q

What is the Pka?

A

PKA: Ph at which you have equal amount of acid and base

pH at which [Acid] = [Base]

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16
Q

What is the isoelectric point?

A

Ph when net charge on protein is 0

PI = PKa1 + PKa2/2

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17
Q

How can you calculate the pH if you only know the Pka and acid base concentrations?

A

PH = Pka + log [A-]/[HA]

HA>H+ + A-

HA = ACID
A- = BASE
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18
Q

What is the primary structure of proteins ?

A

AAs joined by peptide bonds

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19
Q

What are the factors that fact the physical/chemical properties of proteins?

A

Peptide bonds
R-groups
Type of AA
Sequence of AA

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20
Q

What is the secondary structure of protein ?

A

α-helix
Collagen helix

Beta Pleated sheet

Held together and maintain structure by :

  • S-S
  • H-Bond
21
Q

What is the tertiary protein structure?

A

Results from folding of 2o structure on itself

Maintained by:

  • H bond
  • S-S
  • Ionic Bond
22
Q

What is the quaternary structure?

A

Protein consisting of more than one amino acid chain

23
Q

What are the 2 kinds of proteins?

A

Globular Protein >Myoglobin
*Protein helix is folded back on itself

Fibrous Protein > Collagen

*Extended polypeptide chain

24
Q

What is the nutrition breakdown of egg yolks?

A

(30% Fat, 18% Protein, 50% Water)

Lipids
Protei:
-Lipoprotein (Lipovittellin): Emulsifying property
-Non-Lipoprotein (Phosvitin): High in P

25
What is the nutrition breakdown of egg whites?
White (11% Protein, 88% Water) -Ovalbumin: Principal Protein -Conalbumin: Fe- binding > Antibacterial Properties -Ovomucoid: High in CHO: Responsible for consistency of thick white -Lysozyme: Antibacterial Properties
26
What is the structure of muscle tissue?
*Composed of Myofibrillar Proteins (small thread like structure) Myosin: Thick Filaments Actin: Thin Filaments -responsible for muscle contraction and relaxation Actin + Myosin>Actinomyosin
27
What is the structure of connective tissues?
(Bind muscle cells together) Collagen + Heat >Gelatin -sensitive to heat Elastin + Heat> Unchanged -heat resistant
28
What is protein denaturation?
Unfolding of Protein Structure to Expose R-groups
29
What are the causes of denaturation?
Heat, High or Low pH, Salt
30
What are other names for denaturation?
Gelation, Coagulation, Curdling, Precipitation
31
What is hydrolysis?
Cleaves peptide bonds Can be achieved by: Strong Acid/Base, Enzymes
32
What are the 2 kinds of hydrolysis?
Complete Hydrolysis >AA -Strong acid/ase with no specificity, break all peptibe bonds, have AAs Partial Hydrolysis> Peptides -Fragments of protein (peptides)
33
What are the enzymes involved in hydrolysis?
Proteinases Proteolytic Enzymes
34
What is Cysteine susceptible to?
The SH group in cysteine is susceptible to Oxidation forms Disulfide bonds Under oxidaiton, forms thisbond and lacks flexibility
35
What is the water binding capacity?
Protein + Water > Hydrated Protein Water binds to R and backbone> ↑Stability Ovalbumin (egg white) binds readily with water Casein is less readily hydrated
36
What its protein analysis?
Content of PRO in food Kjeidahl Method >Determine the amount of N 16% of protein is N 6.25 g protein / g N
37
What are the kinds of enzymes used not he food industry?
Carbohydrase Proteinases or Proteolytic Enzymes Lipase -Breaks ester bonds in lipids
38
What are the characteristics of enzymes?
Catalyst ↑ RXN Rate 3D-Structure -Has a 3d structure
39
How are the enzymes used in the food industry produce?
Enzymes produced for the food industry are rather “crude” by biochemical standards -Means have predominant enzyme plus other enzymes or other ingredieents. (Predominant Enzymes + Other Enzymes) Contain: Salt Preservatives Stabilizers
40
What is the advantage of using enzymes in food?
Natural, Non-Toxic (plant, animal, microbial sources) Specific Mild Conditions Low Concentration Rate Controllable Inactivated After Use
41
What is the difference between substrate and apoenzymes?
Substrate: Substance acted upon by “E” Apoenzyme: Protein part of “E” -Cofactor non protein portion of enzyme
42
What is the difference between a cofactor and holoenzyme?
Cofactor: (Coenzymes/ Prosthetic group) Non protein portion necessary for activity Holoenzyme: Protein part + Non-protein part
43
What are enzyme kinetics?
The simplest scheme for representing enzyme rxns kinetically: E + S <>ES<>E+ P The substrate binds to the enzyme and is converted to the product and subsequently released Free Enzymes can then react with more substrate
44
What do we assume about enzyme kinetics?
Assumption: Steady State Concept: [ES] is constant Rate of enzyme substrate formation = Rate of enzyme substrate destruction
45
Does the run rate of an enzyme have an optimal ranges?
Max. Activity within narrow range of pH -Max activity within narrow range oh ph Each “E” has its own optimum pH (4-8)
46
What are the optimal temp ranges for enzymes?
30-40oC -optimum for most enzymes > 40oC -Begin to lose activity 70-80oC 2-5 mins irreversible denaturation
47
What is the Q10?
Q10 = Rate at [(T+10)oC] / [Rate at T] Q10 is an index of how sensitive the “E” is to temp. Q10 = x ~ for every 10oC in temp. rate of Rxn is doubled
48
What is the relationship with water activity and enzymes?
Measure of free water and enzymes need water for activities ↓ aw :  ↓ ``E`` activity  ↓ diffusion/mobility of [S] and [P] ``` [S] = Substrate [P] = Product ``` [S] + E  [P] as [P] ↑  Rxn. Stops

Advanced Food Science (12 decks)

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