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HDSO Food Science > Lecture 9 > Flashcards

Lecture 9 Flashcards

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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
Q

What is the nutrition breakdown of egg whites?

A

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
Q

What is the structure of muscle tissue?

A

*Composed of Myofibrillar Proteins (small thread like structure)

Myosin: Thick Filaments
Actin: Thin Filaments
-responsible for muscle contraction and relaxation

Actin + Myosin>Actinomyosin

27
Q

What is the structure of connective tissues?

A

(Bind muscle cells together)

Collagen + Heat >Gelatin
-sensitive to heat

Elastin + Heat> Unchanged
-heat resistant

28
Q

What is protein denaturation?

A

Unfolding of Protein Structure to Expose R-groups

29
Q

What are the causes of denaturation?

A

Heat, High or Low pH, Salt

30
Q

What are other names for denaturation?

A

Gelation, Coagulation, Curdling, Precipitation

31
Q

What is hydrolysis?

A

Cleaves peptide bonds

Can be achieved by:
Strong Acid/Base, Enzymes

32
Q

What are the 2 kinds of hydrolysis?

A

Complete Hydrolysis >AA
-Strong acid/ase with no specificity, break all peptibe bonds, have AAs

Partial Hydrolysis> Peptides
-Fragments of protein (peptides)

33
Q

What are the enzymes involved in hydrolysis?

A

Proteinases

Proteolytic Enzymes

34
Q

What is Cysteine susceptible to?

A

The SH group in cysteine is susceptible to Oxidation

forms Disulfide bonds Under oxidaiton, forms thisbond and lacks flexibility

35
Q

What is the water binding capacity?

A

Protein + Water > Hydrated Protein

Water binds to R and backbone> ↑Stability

Ovalbumin (egg white) binds readily with water

Casein is less readily hydrated

36
Q

What its protein analysis?

A

Content of PRO in food

Kjeidahl Method >Determine the amount of N

16% of protein is N
6.25 g protein / g N

37
Q

What are the kinds of enzymes used not he food industry?

A

Carbohydrase

Proteinases or Proteolytic Enzymes

Lipase
-Breaks ester bonds in lipids

38
Q

What are the characteristics of enzymes?

A

Catalyst

↑ RXN Rate

3D-Structure
-Has a 3d structure

39
Q

How are the enzymes used in the food industry produce?

A

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
Q

What is the advantage of using enzymes in food?

A

Natural, Non-Toxic (plant, animal, microbial sources)

Specific

Mild Conditions

Low Concentration

Rate Controllable

Inactivated After Use

41
Q

What is the difference between substrate and apoenzymes?

A

Substrate:
Substance acted upon by “E”

Apoenzyme:
Protein part of “E”
-Cofactor non protein portion of enzyme

42
Q

What is the difference between a cofactor and holoenzyme?

A

Cofactor: (Coenzymes/ Prosthetic group)
Non protein portion necessary for activity

Holoenzyme:
Protein part + Non-protein part

43
Q

What are enzyme kinetics?

A

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
Q

What do we assume about enzyme kinetics?

A

Assumption:
Steady State Concept: [ES] is constant

Rate of enzyme substrate formation = Rate of enzyme substrate destruction

45
Q

Does the run rate of an enzyme have an optimal ranges?

A

Max. Activity within narrow range of pH
-Max activity within narrow range oh ph

Each “E” has its own optimum pH (4-8)

46
Q

What are the optimal temp ranges for enzymes?

A

30-40oC
-optimum for most enzymes

> 40oC
-Begin to lose activity

70-80oC
2-5 mins irreversible denaturation

47
Q

What is the Q10?

A

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
Q

What is the relationship with water activity and enzymes?

A

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

HDSO Food Science (17 decks)

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