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100 Cards in this Set

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Describe how cell surface acting hormones interact with receptor proteins
cell surface- acting hormones interact with one as three known classes of receptor proteins defined by the signal transduction method that is employed.
what is the determining factor that elicits a response from a cell?
Overlap in signaling pathways, changes in secretion of hormones and alterations in expression of cell receptors provide many opportunities for regulation of cell response to hormones or growth factors.
Describe the interactions of G proteins and the activity state of the enzyme adenylate cyclase.
Changes in activity state of adenylate cyclase as impacted by hormone activation of Gser Gi protein. Hormone activation of Gs or Gi proteins change the activity state of adenylate cyclase which influences the capacity of the enzyme to convert ATP to cyclic AMP
What is the function of adenylate cyclase
Convert ATP to cAMP
Describe how the G protein linked hormone messenger systems functions.
They function by modifying the activity of a separate plasma membrane- anchored protein which may be an enzyme or may act as an ion channel
What is the function of a kinase?
phosphorylation
What is the outcome of the activation of the inositol phospholipid signaling pathway?
Diacylglycerol activates specific protein kinases IP3 triggers release of Ca2+ ions
How do enzyme linked receptors act upon hormone binding?
Binding of the hormone to the receptor activates the receptor so that it is capable of phosphorylating cellular proteins.
Describe homodimerization
binding of two receptors that are the same.
What is the function of Janus tyrosine kinase 2?
phosphorylates STAT proteins
Describe the relationship between STAT5, PRL, GH, and IGF-1
GH, PRL, and IGF-1 stimulates STAT5 DNA binding activity.
Describe how second messenger mechanisms of action work.
Hormones are "first" messenger and the critical molecules influenced inside are the second messengers.
Describe how chaperone proteins function
associated proteins that allow the newly formed hormone-receptor complex can attach to a specific region of the DNA
What does successful lactation require?
Alot of coordination, appropriate development of the mammary alveoli, timely structural and biochemical differentiation of the alveolar secretory cells, metabolic adjustments to supply needed substrates and regular milking or suckling must occur. Successful lactation requires 3 events: 1. The preparation proliferation of alveolar epithelial cells. 2. biochemical and structural differentiation of these cells and 3. Synthesis and secretion of milk constituents
Describe the two stages of lactogenesis
stage 1: consists of limited structural and functional differentiation of the secretory epithelium during the last third of pregnancy.
Stage 2: involves completion of cellular differentiation during the immediate periparturient (before and after) period coinciding with onset of copious milk synthesis and secretion. (fig 3-1)
What are the components of the enzyme complex necessary for lactose synthesis to occur? What is the name of the enzyme?
The enzyme complex necessary for lactose synthesis, membrane bound galactosyltransferase and the whey protein alpha-lactalbumin, combine in the golgi apparatus to form lactose synthetase, which links glucose and galactose to produce lactose. Activation of the alpha-lactalbumin gene and synthesis of alpha-lactalbumin is most closely associated w/stage 2 of lactogenesis.
What are the major positive regulators of structural differentiation of secretory cells?
The major positive regulators of structural differentiation of the secreoty cells are glucocortoids (lactogenesis->cortisol->stress) and prolactin. Insulin causes nutrients to be shunted away from mammary gland lowering milk production
what is the controvery regarding insulin and mammary cells?
Recent data support the idea that insulin-mediated effects on mammary cells in culture may actually represent effects more appropriately ascribed to the insulin-like growth factors (IGF-1 and IGF-11). This is because mammary epithelial cells have specific IGF-receptors and insulin is likely to bind to the IGF-1 receptor.
Thyroid protein
What organelle is stimulated by glucocorticoid?
Glucocorticoids are most closely associated with development of rough ER. Protein happen in ER
What organelles are stimulated by prolactin?
The golgi (packages and organizes lactose synthesis) apparatus and secretory vesicles.
What occurs during the second stage of lactogenesis?
The approach of parturition signals both the structural differentiation of the alveolar cells and maturation of tight junctions (zona occulens) between the cells. Increases in circulating glucocortoids along with declining progesterone seem to be especially important. Once this occurs, generally just after parturition, paracellular transport of components between the the cells is dramatically reduced. This creates an effective blood-milk barrier so that transfer of serum components into milk or milk consituents into blood is minimized.
What is the function of a tight cell junction?
To stop leakage into cells. To create an efficient blood milk barrier so that transfer of serum component.
In in the case of some type of mammary infection, what would be observed in the milk and the blood?
High milk SCC causes increased diapedesis of leukocytes into milk disruption of tight junctions and consequently greater passage of milk components into blood. Serum protein-lactobumin
antibodies-immunoglobulins
Describe the relationship of serum alpha-lactalbumin from prepartum to postpartum. How is this useful?
During the immediate periparturient period, serum alpha-lactalbumin concentrations peak just after calving but very rapidly decline. This abrupt decrease is believed to indicate the rapid maturation of the tight junctions at this time. Changes in serum alpha-lactalbumin can also be used to monitor mammary development during hormonal induction of lactation.
Describe the relationship between milk somatic cell count and alpha-lactalbumin.
Serum alpha-lactalbumin concentration was lower in cows with low milk SCC. It is positively correlated with milk SCC. Increases rapidly 3 weeks prior to calving.
Define paracellular passage.
Passage of soluble molecules between cells
Is milk secretion continuous during lactation and where is milk stored?
Once secreted, it continues more or less continuously throughout lactation. Milk is stored within the lumen of the alveoli and ductular system.
What are the requirements of net energy intake and glucose for the high producing cow?
80% of net energy intake and 85% of circulatory glucose (-> lactose)<--comes from propionate some from gle<---comes from microbes digesting starch----> amylotitic bacteria that break down starches and utilize sugars. you can get this from bakery waste sugar corn barley
What are the five routes of secretion across the mammary gland? Describe each one
1. Membrane route- refers to intestinal fluid-derived substances that cross the basolateral membrane, traverse the cell and pass across the apical membrane into milk Ex: water
2: Golgi route- products are synthesized, sequestered or packaged into secretory vesicles that bud from the stacks of golgi membranes. Vesicles fuse to the apical plasma membrane to release their contents to become part of milk.
3. Milk fat route-refers to substances that become entrained with the budding lipid droplets as they are released from the apical cell surface to become part of the milk.
4. Transcytosis- vesicles derived from the basolateral membrane are transported in membrane bound vesicles for excytosis at the apical membrane.
5. Paracellular route- direct passage for materials in the interstitial fluid between the epithelial cells and into milk.
What is the function of microtubules.
Microtubules are most frequently observed orientated perpindicular with respect to the apical plasma membrane (structure). Help transport secretory vesicles.
What occurs during the second stage of lactogenesis?
The approach of parturition signals both the structural differentiation of the alveolar cells and maturation of tight junctions (zona occulens) between the cells. Increases in circulating glucocortoids along with declining progesterone seem to be especially important. Once this occurs, generally just after parturition, paracellular transport of components between the the cells is dramatically reduced. This creates an effective blood-milk barrier so that transfer of serum components into milk or milk consituents into blood is minimized.
What is the function of a tight cell junction?
To stop leakage into cells. To create an efficient blood milk barrier so that transfer of serum component.
In in the case of some type of mammary infection, what would be observed in the milk and the blood?
High milk SCC causes increased diapedesis of leukocytes into milk disruption of tight junctions and consequently greater passage of milk components into blood. Serum protein-lactobumin
antibodies-immunoglobulins
Describe the relationship of serum alpha-lactalbumin from prepartum to postpartum. How is this useful?
During the immediate periparturient period, serum alpha-lactalbumin concentrations peak just after calving but very rapidly decline. This abrupt decrease is believed to indicate the rapid maturation of the tight junctions at this time. Changes in serum alpha-lactalbumin can also be used to monitor mammary development during hormonal induction of lactation.
Describe the relationship between milk somatic cell count and alpha-lactalbumin.
Serum alpha-lactalbumin concentration was lower in cows with low milk SCC. It is positively correlated with milk SCC. Increases rapidly 3 weeks prior to calving.
Define paracellular passage.
Passage of soluble molecules between cells
Is milk secretion continuous during lactation and where is milk stored?
Once secreted, it continues more or less continuously throughout lactation. Milk is stored within the lumen of the alveoli and ductular system.
What are the requirements of net energy intake and glucose for the high producing cow?
80% of net energy intake and 85% of circulatory glucose (-> lactose)<--comes from propionate some from gle<---comes from microbes digesting starch----> amylotitic bacteria that break down starches and utilize sugars. you can get this from bakery waste sugar corn barley
What are the five routes of secretion across the mammary gland? Describe each one
1. Membrane route- refers to intestinal fluid-derived substances that cross the basolateral membrane, traverse the cell and pass across the apical membrane into milk Ex: water
2: Golgi route- products are synthesized, sequestered or packaged into secretory vesicles that bud from the stacks of golgi membranes. Vesicles fuse to the apical plasma membrane to release their contents to become part of milk.
3. Milk fat route-refers to substances that become entrained with the budding lipid droplets as they are released from the apical cell surface to become part of the milk.
4. Transcytosis- vesicles derived from the basolateral membrane are transported in membrane bound vesicles for excytosis at the apical membrane.
5. Paracellular route- direct passage for materials in the interstitial fluid between the epithelial cells and into milk.
What is the function of microtubules.
Microtubules are most frequently observed orientated perpindicular with respect to the apical plasma membrane (structure). Help transport secretory vesicles.
What is the correlation between SCC and the concentration of alpha lactalbumin in blood?
positive.
define isosmotic
solution contains the same salt concentration as blood (milk is isosmotic w/ blood). Two lipids have some ion concentration.
proteins in milk arise from?
most of the proteins present in milk are synthesized from free amino acids or peptides absorbed from the bloodstream.
where is the site of milk protein synthesis?
in the bloodstream
after synthesis of protein where does it go in the cell?
the basolateral membrane serves to regulate the uptake of these molecules from interstitial fluids.
describe the synthesis of lactose.
Enzymes necessary for lactose synthesis are present in the golgi apparatus. After it is synthesized and its signal directs it into the RER cisternae, the whey protein alpha lactalbumin is glycosylated in the golgi apparatus. During transit it combines with membrane bound galactosyltransferase to generate the functional enzyme lactose synthase. This enzyme acts to combine the monosaccarides glucose and galactose to produce lactose.
How is lactose transported across the cell?
Lactose is packaged into secretory vesicles along with other specific milk proteins. B/c it cannot travel across the secretory vesicle membrane it has an osmotic effect.
How are proteins transported across cells?
Packaged into secretory vesicles and carried.
describe the formation and transport of lipids.
Lipid droplets first form as microdroplets near the RER. Through poorly understood mechanisms the droplets progressively enlarge and make their way to the apical plasma membrane. It is theorized that cytoplasma proteins serve to direct this intracellular passage. These enlarged droplets begin to protrude from the cell, pushing a portion of the plasma membrane into the alveolar lumen. The droplets ultimately pinch off surrounded by portions of the cell membrane. These membrane droplets are subsequently suspended in the alveolar lumen.
How does milk fat exist in milk?
milk fat exists primarily as membrane bound globules ranging from .1 to 15 um in diameter.
How many milk fat globules are there in 1 mL?
15x10^9 in 1 mL
describe the milk fat globule of holstein milk.
Membrane material associated with the fat globules in Holstein cows averages about 1.5g/100g of milk fat and consists of 60 percent protein and 40 percent phospholipids along with small amounts of other lipids.
Describe what happens to dietary fatty acids in the rumen.
In ruminants because of biohydrogenation in the rumen, nearly all of the dietary fatty acids are synthesized before they are available for triglyceride synthesis in the mammary gland.
What is CLA, how is it made, and why is it important?
CLA is conjugated linoleic acid. They are intermediates in rumen biohydrogenation of unsaturated fatty acids and are believed to be the source of these molecules in milk. They have been shown to have potent health benefits including inhibition of carcinogenesis reduction in atherogenesis and prevention of diabetes.
What maintains the concentration of ions in milk?
the action of the NA^+ K+ ATPase pumps in the basolateral membranes. The apical plasma membrane is permeable to both ions so that the distribution of these ions into milk is controlled by the electric potential across the apical plasma membrane.
What is the normal K/Na ratio in cow's milk? If this number got lower, what would you suspect and why?
concentrations of Na+ inside the cells are typically lower than outside, but the gradient for k+ is the opposite. Leakiness of tight junctions is altered allowing the concentrations to change.
What is MUN and why is it important?
Milk Urea Nitrogen is a tool for dairy nutritionists to evaluate protein metabolism.
Describe some of the contaminants found in milk.
Materials that are not normally secreted into milk but appear either by accident or design some of these substances are eaten or inhaled by the lactating animal and pass into milk via the bloodstream and mammary gland. Ex: pesticides and herbicides, and antibiotics.
What are the substrates that are extracted from, the blood in the lactating mammary gland?
glucose, amino acids, fatty acids and minerals. Ruminants also extract acetate and Beta hydroxybutate.
What is glucose a precursor of?
Glucose is the direct precursor for lactose, ribose, and much of the glycerol needed for triglyceride synthesis.
Where do amino acids arise from?
The bloodstream
Where do fatty arise from and what are they precursors of?
From the bloodstream (dietary lipids- come from adipose tissue and de nova (intramammary synthesis) They are precursors for triglycerides.
Where do coenzymes arise from and what is their function?
they are necessary for de novo fatty acid synthesis or for ribose synthesis. They are derived by oxidation of isocitrate in the Krebs cycle or the pentose phosphate shunt.
cytosol
glycolysis, NADPH production, alpha glycerol phosphate synthesis ribose amino acid. Genetic blueprint.
Rough endoplasmic reticulum.
is the site for esterification of fatty acids to glycerol and ultimately lipid droplets production. This is in addition to generation of phospholipids and desaturation of fatty acids.
mitochondria
numbers increase with the onset of lactation. Are the sites for production of ATP generation of precursors for synthesis of nonessential amino acids and formation of building blocks for de novo fatty acid synthesis.
nucleus
DNA. RNA synthesis
Golgi
Where lactose is produced and together with milk proteins packaged into vesicles for secretion. casein, phosphorylation
What are the primary differences between non-ruminants and ruminants in the production of energy by the mammary gland?
The most important substrates for production of energy in mammary cells are glucose and acetate. Use of these substrates for energy production, however, are markedly different in rum and non. Nonrum. have relatively higher circulating glucose concentrations but usually little acetate. So for these animals glucose is readily used for generation of ATP and propionate to generate a sufficient quantity of blood glucose.
In the TCA cycle what is produced that results in the production of ATP and where is ATP generated?
NADH and FADH go to ETC-> ATP and water(metabolic water) ATP synthase.
differences between figure 4.3 and 4.4
fatty acid synthesis in ruminants (4.3) doesn't involve the malate transhydrogenation cycle. ATP citrate lyase.
Describe how lactose is synthesized.
The functional enzyme required for lactose synthesis, lactose synthase, is actually a combination of two proteins that come together in the golgi apparatus. The pathway for synthesis involves three general steps:
1) UTP+glucose-> UDP - glucose +p-p
2) UDP - glucose-->UDP-galactose
3) UDP-glactose+glucose---> lactose + UDP
this occurs in golgi
What is the most variable of the major milk constituents
milk fat content
what is milk fat comprised of?
most of the milk fat is comprised of triglycerides but particular fatty acids are highly variable
what are the 3 sources of the fatty acids in milk triglycerides?
The three sources of the fatty acids in milk triglycerides are:
(1) glucose via conversion to pyruvate, citrate and ultimately acetyl coA in the cytoplasma
(2) diet via hydrolysis of chylomicra
(3) De novo synthesis within the mammary cells from nonglucose sources: acetate and beta hba in ruminants
What is the major source of fatty acids for non ruminants?
glucose is a major source for nonruminants but not for ruminants
in the dairy cow where are the c18 and greater fatty acids derived from?
Estimates for cows are that half of the milk fatty acids are derived from the diet, including most of the c18 fatty acids and about 30 percent of the c18 fatty acids.
where are the shorter chain fatty acids from?
shorter chain fatty acids are more likely to derive from de novo synthesis (within the mammary gland synthesized by acetate and BetaHBA)
What are the precursors of the c14 and shorter fatty acids in the cow?
In cows precursors for de novo fatty acids synthesis are acetate and BHBA.
Where are the NADPH derived from?
Nicotinamide dinucleotidephophate comes either from the catabolism of glucose via the pentose phosphate shunt or the oxidation of isocitrate to a ketoglutamic acid in the Krebs cycle.
What pathway sequentially adds two C units to the fatty acids in the ruminant mammary gland?
the malonyl coA pathway
Describe the steps in the synthesis of fatty acid.
The first step depends on the regulatory enzyme acetyl coA carboxylase and involves the addition of carbon from CO2 to acetyl CoA and hydrolysis of ATP to form malonyl CoA. The second step is catalyzed by fatty acid synthase. This complex enzyme controls growth of the growing fatty acid chain two carbons at a time. Fatty acids can only be even!
What are the differences between ruminants and non ruminants in fatty acid synthesis.
Differences between fatty acid synthesis concern the sources of the acteryl CoA needed in the initial step and generate the necessary NADPH.
What is the function of thioesterase II
The enzyme thioesterase II in mammary tissue induces the synthesis of more medium chain fatty acids and fewer long chain fatty acids. Up to C14. If you did not feed vegetable sources this C14 would be the most. Manipulate milk by adding LCFA
Where are milk proteins synthesized?
They are synthesized from amino acids derived either from the bloodstream (essential amino acids) or from amino acids synthesized by the secretory cells.
Define casein
casein is a mammary specific protein including alpha casien, beta casein, k-casein and gamma casien. The proteins that are precipitated when skim milk is acidified to pH 4.6@ 20C
What amino acids are high in casein?
prolene and glutamic acid
Describe the casein micelle
A nutritious source of amino acids and a colloidal structure of the micelle also allows the transport of large amounts calcium and phosphorus in a stable form. Generally spherical with a granular appearance and most range from 300mm in diameter.
describe why k-casein is important
k-caseins are glycosylated and differ from others because they are easily degraded by the enzyme chymosin(renin) to yield to fragments called para-k-casein and glycomacropeptide. This property accounts for the ability of renin to rapidly coagulate milk and illustrates the critical importance of k-caseins in stabilizing the casein micelle. Renin is what makes cheese clot.
Describe the proteins in whey
Beta-lactoglobulins, alpha-lactalbumin, immunoglobulins, serum albumin, lactoferrin, transferrin
Describe Beta-lactoglobulin
present in ruminants but essentially absent in the milk of humans, rats, and guinea pigs. Beta-lactoglobulin is the major whey protein in the milk of cows;it accounts for for more than 50 percent of the whey protein. Relevant nutritionally not biologically.
Describe how lactoferrin functions in the mammary gland
Lactoferrin and transferrin are glycoproteins, which transport and bind iron. Lactoferrin especially is bacteriostatic and is believed to be important as a nonspecific component in defense of the mammary gland. Availability of unsaturated lactoferrin serves to inhibit the growth of gram + and gram - bacteria in secretions because of its ability to sequester iron and limit its use by the bacteria
describe how proteins are synthesized
protein synthesis in mammary cells follows the pattern described for many other tissues. Aside from directing its own replication DNA also serves direct protein synthesis by its capacity to generate mRNA
What are the forms of RNA that is dependent on protein synthesis?
Transfer RNA, ribosomal RNA, and messenger RNA.
Why are bacterial cultures beneficial for human medicine?
bacterial cells now are utilized to produce virtually unlimited supplies of human growth hormone or insulin. Because insulin and the growth hormones are simple proteins that do not required posttranslational modifications for bioactivity, production in bacterial cultures is successful. They also produce recombinant human growth hormone and insulin
Describe how transgenics work
transgenic animals grew more rapidly and reached a greater size than controls. Carry copies of alternate genes to display a desirable protein.
Why is the mammary gland a logical choice for the production of therapeutic proteins?
Milk proteins are expressed at high levels and with very good tissue specificity. Second, milk can be readily obtained and in the case of dairy species for long periods in high volume.
Why are researchers considering developing cows that do not contain the alpha lactalbumin gene?
to reduce lactose intolerance. No alpha lactalbumin gene. But it makes the milk extremely viscous
what are the benefits of this?
you could dramatically lower the volume of milk needed to be stored and transported. Also allows infants to be fed bovine based formulas.
What would be the benefit of blocking the production of beta lactoglobulin?
blocking the production of beta lactoglobulin in bovine milk would likely be a benefit since many of the allergy problems of human infants consuming bovine milk appear to involve beta lactoglobulin. Beta lactoglobulin is the major whey protein but we don't know why its there.