Lecture 9 Flashcards
What is the structure of an AA?
central C attached to Amino group, R group and Acrboxylic acid group
What % of C,O,N,H,S is in proteins?
Carb 50% O 22% N 16% H 7% S little
What is protein condensation?
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
What is the bond that connects 2 AAs?
Peptide bond is the bond between the AA
What is a hybrid or twitter ion?
AA that is ampthoteric
-AA can carry +/- charge at the same time on same molecule
What happens to a twitter ion when pH increases or decreases?
Low ph will appear in acid form
-net charge +
Increase ph go to basic form
-net chargee is -1
What are the characteristics of acid coagulation of casein?
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
What situation would be desireable/undesireable use of acid coagulation of casein?
Desireable if you want yogurt you want coagualtion of casein or in cheese
Undesirable curdling of milk in a smoothie
What are the uncharged R groups of AAs?
Serine
Threonine
Cysteine
Glyceine
What are the negatively charged AAs?
Aspartate
Glutamate
What is the one positively charged AA?
Lysine
What are the non polar R groups?
Methionine
Phenylalanine
Alanine
Valine
What are the essential AAS?
Valine Leucine Isoleucine Phenylalanine Tryptophan Lysine Arginine Histidine Methionine Threonine
What are the R groups for Gly, Asp, Set, Lys, Ala, Phe, Cys, Glu?
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
What is the Pka?
PKA: Ph at which you have equal amount of acid and base
pH at which [Acid] = [Base]
What is the isoelectric point?
Ph when net charge on protein is 0
PI = PKa1 + PKa2/2
How can you calculate the pH if you only know the Pka and acid base concentrations?
PH = Pka + log [A-]/[HA]
HA>H+ + A-
HA = ACID A- = BASE
What is the primary structure of proteins ?
AAs joined by peptide bonds
What are the factors that fact the physical/chemical properties of proteins?
Peptide bonds
R-groups
Type of AA
Sequence of AA
What is the secondary structure of protein ?
α-helix
Collagen helix
Beta Pleated sheet
Held together and maintain structure by :
- S-S
- H-Bond
What is the tertiary protein structure?
Results from folding of 2o structure on itself
Maintained by:
- H bond
- S-S
- Ionic Bond
What is the quaternary structure?
Protein consisting of more than one amino acid chain
What are the 2 kinds of proteins?
Globular Protein >Myoglobin
*Protein helix is folded back on itself
Fibrous Protein > Collagen
*Extended polypeptide chain
What is the nutrition breakdown of egg yolks?
(30% Fat, 18% Protein, 50% Water)
Lipids
Protei:
-Lipoprotein (Lipovittellin): Emulsifying property
-Non-Lipoprotein (Phosvitin): High in P
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
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
What is the structure of connective tissues?
(Bind muscle cells together)
Collagen + Heat >Gelatin
-sensitive to heat
Elastin + Heat> Unchanged
-heat resistant
What is protein denaturation?
Unfolding of Protein Structure to Expose R-groups
What are the causes of denaturation?
Heat, High or Low pH, Salt
What are other names for denaturation?
Gelation, Coagulation, Curdling, Precipitation
What is hydrolysis?
Cleaves peptide bonds
Can be achieved by:
Strong Acid/Base, Enzymes
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)
What are the enzymes involved in hydrolysis?
Proteinases
Proteolytic Enzymes
What is Cysteine susceptible to?
The SH group in cysteine is susceptible to Oxidation
forms Disulfide bonds Under oxidaiton, forms thisbond and lacks flexibility
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
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
What are the kinds of enzymes used not he food industry?
Carbohydrase
Proteinases or Proteolytic Enzymes
Lipase
-Breaks ester bonds in lipids
What are the characteristics of enzymes?
Catalyst
↑ RXN Rate
3D-Structure
-Has a 3d structure
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
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
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
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
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
What do we assume about enzyme kinetics?
Assumption:
Steady State Concept: [ES] is constant
Rate of enzyme substrate formation = Rate of enzyme substrate destruction
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)
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
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
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
