MILK COMPOSITION Leo Timms Iowa State University.
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Transcript of MILK COMPOSITION Leo Timms Iowa State University.
MILK COMPOSITION
Leo Timms
Iowa State University
MILK COMPOSITION• Components are similar across species:
- Water - Lactose (CHO) - Proteins
- Lipids(fats) - Minerals - Vitamins
• Component % differ w/in & across species!• Milk is greater than the sum of it’s parts!• Emulsion of fat globules and a suspension
of casein micelles (casein, Ca, P), all suspended in an aqueous phase which contains lactose, whey proteins, minerals, and salts.
MILK COMPOSITION
Lactose, whey,minerals, salts
H20
A. Fully differentiated alveolar epithelial cells characterized by presence of numerous vacuoles (V), rounded basally positioned nuclei (N), abundant cytoplasm, and frequent occurrence of large apically located lipid droplets (F); alveolar lumen is L.
B. Intermediately differentiated alveolar epithelial cells showing fewer cellular vacuoles, more irregularly shaped nuclei, and greater nuclear to cytoplasmic ratio.
C. Undifferentiated alveolar epithelial cells displaying relative absence of cellular vacuoles, highly irregularly shaped nuclei, a mixture of large and small lipid droplets, and very large nuclear to cytoplasmic ratio, (X4,000).
ALVEOLUS
ALVEOLUS
ALVEOLUS
MILK COMPOSITION
Apical membrane
Basementmembrane
MILK COMPOSITION Rat Cow
Nucleus 22 22
RER 15 16
Golgi 21 19
Mito. 7 6
Lipid 1.5 5
Other 33.5 32
MILK COMPOSITION
SECRETION ROUTES
Membrane route
Waterurea
glucoseions
SECRETION ROUTES
Golgi route
Lactosecaseinwhey prot.CitrateCa
SECRETION ROUTESFats
hormonesdrugs
Milkfatroute
SECRETION ROUTES
Transcytosis
SECRETION ROUTES
Tightjunction
Paracellular:between cells
Not commonunless cells disrupted:mastitis!
SECRETION ROUTESMembranerecycling
pH: 6.2-6.9Freeze pt.?< 32F (0C)
MILK COMPOSITION
MILK COMPOSITION
WATER• Highest component except some marine
mammals!• Decreased viscosity so milk can be easily removed from the gland by the neonate• Major source of water for neonates!!!
• No resorbtion in ducts
MILK COMPOSITION
CARBOHYDRATES• LACTOSE
- primary milk CHO in most species- unique to milk
- major osmole in milk- least variable component?
- greatly impacted by mastitis • <1% - >7%: species differences
MILK COMPOSITION
CARBOHYDRATES* mg / 100ml•LACTOSE 5000 (5%)• Glucose 14• Galactose 12•N- acetyl glucosamine 11• Oligosaccharides
LACTOSE
• GLUCOSE is absolutely essential!!!• Can’t be replaced by any other sugar!• Lactose: uses 65-80% of total body glucose in high producing animals• Correlation between milk production and mammary glucose uptake = .93!
WHERE DOES THE GLUCOSE COME FROM?* non ruminants - sugars, digestion of starch
LACTOSE
LACTOSE
LACTOSE
LIVER (glycogen storage)
• Ruminant blood glucose levels 50% of monogas.• 45 - 60% of blood glucose from propionate• glucogenic amino acids, some lower GIT digestion
(Locks glucose in cell)
ATP:not inruminants
NADPH, RIBOSE(fat synth., DNA/RNA)
GLYCEROLmilkfat
LACTOSE• Disaccharide
• Glucose and galactose
• UTP + Glucose UDP- glucose + P-P
• UDP - glucose UDP galactose(epimerase)
• UDP - galactose + glucose lactose + UDP
LACTOSE
LACTOSE• Major enzyme complex: lactose synthase
• Comprised of two enzymes
• Galactosyl transferase(widely present in many cells)
(transfers sugar moeities)
• alpha lactalbumin(specific to the mammary gland!!!)
gene expression increases w/lactogenesismust continually be made: secreted in milk
LACTOSE
Draws in water
LACTOSE
• Milk is always isosmotic with blood!!• Lactose is major osmole but can change!