157343
Proteins
- Large molecules :
high molecular
weight (20,000 -
2mil)
- Polymers: made up
of smaller monomers
- Amino
acids!
- 20 aa in a protein
- 9 essential, 11
non-essential
- Need essential from diet for
body to make non-essentials
- Withut essential aa, no protein formed.
- Need essential from diet for
body to make non-essentials
- 9 essential, 11
non-essential
- P broken down
into aa by
Hydrolysis - eg saliva
Anmerkungen:
- Breaking of bonds by adding water
- Not stored in body long - fresh supply of
essental aa required daily.
- 20 aa in a protein
- Amino
acids!
- Main componants of muscles and
tissues, enzymes regulating
metabolism and functions of body,
structure of hormones & antibodies
- NITROGEN (16%),
CARBON,
HYDROGEN,
OXYGEN, sometimes
SULFUR,
PHOSPHORUS
- To find how much
protein in food, analyse
how much prtotein
nitrogen then x by 6.25
- Adults don't require as much
protein as childrren because
they have stopped growing
- High quality proteins:
meat, milk, eggs
Anmerkungen:
- Because they contain all the essentail amino acids in the amounts needed to support protein tissue formation by the body.
- Soy Beans: almost complete P
- Properties:
SOLUBILITY,
WATER BINDING,
STRUCTURE,
DENATURATION,
REDUCTION,
HYDROLYSIS
- SOLUBILITY
Anmerkungen:
- differences determined by amino acid sequence and composition
- Soluble in water: histones (protein
replication), ovalbumims (egg
whites), lactalbumin (milk),
albumins of blood.
- Insoluble in water: keratin
(hair/fingernails), collagen (bones,
cartilage, connective tissue,
epidermis)
- Soluble in weak
salt solutions:
myosin (muscle
tissue),
lactoglobins (milk)
- Soluble in acids:
wheat glutenin,
oryzenin (rice)
- Water bindning
- Through
hydrogen
bonding w/-
muscle tissue
of meats
(ground
products ie hot
dogs, mince)
- Through
hydrogen
bonding w/-
muscle tissue
of meats
(ground
products ie hot
dogs, mince)
- Structure
- Primary: molecular weight, aa
composition & seq along
peptide chain.
- Secondary: shape of coiled helix
- Tertiary: folding of a chain over itself
- quartenary: 2 or
more polypeptide
chains join
- Changed through
food processing
- Primary: molecular weight, aa
composition & seq along
peptide chain.
- Denaturation: change in
strcuture without
breaking covalent
bonds, or aa seq.
- Loss of biological activity & changes
in physical/functional proeprties (ie
solubility)
- Caused by heat, acids, solvents,
concetrated salts, surface forces.
- eg. 'Blanching; in freezing/canning
fruits & veg, Cheeses/Yogurts,
Hardening of egg whit in pan (heat
denaturation), whipping of egg
whites to foam (surface force), slow
cooking meat.
- Contributes to
flavour & texture
of food.
- Loss of biological activity & changes
in physical/functional proeprties (ie
solubility)
- Reduction:
- Hydrolysis: cleaving of peptide bonds
by adding water molecule.
- Complete: P broken down to aa cparts
- Partial: protein hydrolsates,: flavours parts of soups, sauces, gravy. plant
prteins hydrolysed by hydrochloric acid - neuatralised with alkali.
- Partial: protein hydrolsates,: flavours parts of soups, sauces, gravy. plant
prteins hydrolysed by hydrochloric acid - neuatralised with alkali.
- Complete: P broken down to aa cparts
- SOLUBILITY
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