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Amino Acid Derivatives and Important Biomolecules
(biosynthesis pathways and important facts)
Terms in this set (45)
What two hormones are produced by the thyroid gland? What are their abbreviations? What type of hormones are they? Where, how, and from what are they synthesized?
Thyroxine (T4), triiodothyronine (T3). Growth hormones. Thyroid gland, by post-translational modification of tyrosyl residues of the thyroid gland protein called thyroglobulin.
Describe in detail the production of T4 and T3 from thyroglobulin.
Tyrosyl residues in thyroglobulin get modified with phenol and iodine to convert the residues to thyroxine or triiodothyronine. Thyroxine and triiodothyronine are subsequently released as hormones by proteolytic degradation of thyroglobulin.
How does a lack of iodine in the diet affect the human body? How is this prevented?
Impairs T4 and T3 synthesis, causing a condition called hypothyroidism. Causes goitre to form which is swelling of the thyroid gland. Table salt is supplemented with iodine in order to prevent this.
What are three functions that T4 and T3 have in the body?
Help regulate long bone growth as well as neural maturation, and increase basal metabolic rate.
What is hyperthyroidism? How is it treated?
Overproduction of T4 and T3 by thyroid. Thyroid gland is either removed surgically or with radioactive Iodine I-125. I-125 gives off gamma rays which kills thyroid.
What is Dopamine? What does it do?
Dopamine is a neurotransmitter synthesized and released by nerve cells to alter the behavior of neighboring cells. It is involved in the brains reward pathways.
How is dopamine synthesized?
Tyrosine is hydroxylated at C-5, forming dihydroxyphenylalanine (DOPA). This is followed by decarboxylation of the a-carboxyl group.
Where, and from what, are epinephrine (adrenaline) and norepinephrine synthesized?
Adrenal medulla, from tyrosine or phenylalanine.
When does break down of glycogen occur?
when muscle cells need glucose for energy production.
In what three ways do epinephrine and norepinephrine affect muscle cells (myocytes)?
Epinephrine and norepinephrine act on muscle cells to promote enzymatic breakdown (degradation or hydrolysis) of stored glycogen in musle cells (myocytes) to Glucose-1-phosphate (Glucose-1-O-PO3).
Inhibit glycogen synthesis.
Epinephrine and norepinephrine also cause -the release and accumulation of Ca2+ in muscle cells to cause muscle contraction.
How do epinephrine and norepinephrine promote the enzymatic breakdown of stored glycogen?
initiate a cascade of signal transduction reactions that leads to the activation of glycogen phosphorylase. This enzyme catalyzes the phosphorolysis of glucose residues from glycogen.
Frowm what is s-adenosylmethionine synthesized? What is its function? What is it converted too after functioning?
S-Adenosylmethionine (SAM) is synthesized from methionine and ATP.
SAM is the major donor of methyl groups in biosynthetic reactions.
S-Adenosylmethionine is converted to S-Adenocylhomocysteine
How is serotonin synthesized, from where, and what is its function?
Synthesized by sequential hydroxylation and decarboxylation of tryptophan. Primarily in the enterochromaffin cells in the epithelial lining of the digesative tract, but also synthesized in the CNS. It is a neurotransmitter. In the digestive tract it is used to regulate intestinal movements. In the CNS it regulates mood, appetite, and sleep.
What is a basophil?
a type of white blood cell in which histamine is stored in granules.
How is histamine synthesized?
by decarboxylation of histidine.
How and why is histamine released into the blood? What effect does it have?
The granules in basophils degranulate during allergic reaction leading to the release of histamine into blood.
Histamine causes the dilation of blood vessels leading to the release of water from blood. This effect is responsible for the watery eyes and nose associated with allergic reactions
How does histamine affect digestion?
Histamine controls the release of hydrochloric acid (HCl) from the stomach during digestion.
What does GABA stand for, where is it synthesized, and what is its function? How is it synthesized?
gamma-aminobutyrate, in nerve cells of CNS, cheif inhibitory neurotransmitter of CNS, regulates neuron excitability. synthesized by decarboxylation of the a-carboxyl group of L-glutamate
What is the commercial name for aspartame? What is aspartame? Is it sweeter than sugar? What disease prevents an individual from being able to consume aspartame and why?
Nutrasweet. A synthetic methyl ester of the dipeptide aspartylphenylalanine. yes, 200X. Phenylketoneuria, because they lack the enzyme to metabolize phenylalanine.
To what class of diseases does phenylketoneuria belong? What does this class of disease result from? What enzyme do phenylketoneurics lack? What does this enzyme do? In phenylketoneurics, what is phenylalanine converted into? How are these waste products eliminated?
"inborn errors of metabolism". genetic mutations leading to inactivation of enzymes involved in metabolic pathways. phenylalanine hydroxylase. converts phenylalanine to tyrosine. phenylalanine is converted to phenylpyruvate (phenylketone), phenyllactate and phenylacetate. excreted in urine.
How is phenylketoneuria characterized? What is the theory of how this characteristic is caused? What is believed to be another maleffect of the build up of phenylalanines waste dervatives?
by severe mental retardation. Available evidence suggests that phenylpyruvate, which is a phenylketone, causes mental retardation by interfering with the utilization of pyruvate by brain cells to generate energy.
It is also believed that the accumulation of phenylpyruvate, phenyllactate and phenylacetate in the brain lead to an osmotic imbalance where water flows to the brain causing brain cell to swell and crush each other
How is phenylketoneuria screened for? How is it treated?
Newborn babies are routinely screened for phenylalanine hydroxylase activity. Phenylketonuria is treated by dietary changes. The dietary changes involve the limitation of phenylalanine in the diet to just what is needed for protein synthesis and supplementing the diet with tyrosine since they cannot synthesize it
What is glutathione? What is its significance?
Glutathione is a tripeptide made up of glutamate, cysteine and glycine. Glutathione contains an unusual g-linked peptide bond between glutamate and cysteine. It is an important reducing agent in the cytosol of cells.
How are superoxide radicals generated? How are they detoxified?
generated by cellular metabolism and from drugs and chemicals. detoxified by glutathione peroxidase using glutathione
What is glutathione disulfide? How is it converted back to glutathione?
Glutathione disulfide (GSSG) formed by the reaction of glutathione with superoxide radicals is reduced back to glutathione by glutathione reductase which uses NADPH + H+ as proton donor.
How is NADPH generated?
NADPH + H+ is generated from the Pentose Phosphate Pathway that converts glucose-phosphate to 6-phosphogluconate using glucose-6-phosphate dehydrogenase (G6PDH) as enzyme and NADP+ as coenzyme.
How is glutathione synthesized? What is significant about this pathway?
Glutathione (GSH) is synthesized as part of the g-glutamyl cycle of glutathione metabolism. The g-glutamyl cycle provides a vehicle for transport of amino acids into cells through the synthesis and breakdown of GSH
What are four biochemical reactions and corresponding enzymes that involve glutathione?
2. Glutathione reductase
-regeneration of GSH from GSSG
3. Thiol transferase
-modulates protein thiol-disulfide balance
Give a summary of the 4 metabolic functions of glutathione.
Transport of amino acids from the outside to the inside of cells by the g-glutamyl cycle.
Maintenance of protein thiol-disulfide balance in the cytosol.
Detoxification of peroxides generated in the cytosol from the action of intracellular oxidases.
Biosynthesis of leukotrienes (prostaglandins)
How could one distinguish between a sample containing phenylalanine and a sample containing tyrosine?
by using UV spec. phenylalanine absorbs at 260 while tyrosine absorbs at 280.
What is one way of observing a tyrosine deficiency visually?
Paler skin indicates lack of melanin, a product of the precursor tyrosine.
What does NADPH stand for?
Nicotinamide adenine dinucleotide phosphate
What type of reactions utilize NAD+/NADH? What is the main donor of hydrogen in biosynthetic reactions? How is NADPH generated? What else does this pathway produce? During which step is this produced?
reversible reactions, such as reversible conversion between pyruvate and lactate use NAD+/NADH. reduced NADP (NADPH). solely by the Pentose Phosphate Pathway, during the two oxidative steps. the ribose-5-phosphate used for the synthesis of both ribonucleotides and deoxyribonucleotides. Ribose-5-phosphate is synthesized during the non-oxidative step of the pentose phosphate pathway during which interconversions to other sugars do occur.
How are deoxyribonucleotides synthesized?
Deoxyribonucleotides are synthesized by converting ribose to 2-deoxyribose by the enzyme ribonucleotide reductase which uses Fe3+ as a cofactor
What molecule, and what functional group of that molecule, reduces NADP+ to NADPH? What happens to the molecule after it is oxidized?
The aldehyde group of glucose-6-phosphate reduces NADP+ to NADPH. The aldehyde gets oxidized to a carboxylate to form 6-phosphogluconate, an aldonic acid.
What is technical and clinical application of the Pentose Phosphate Pathway? What about htis pathway allows for this type of assay?
used extensively to assay the activity of glycolytic enzymes and to determine glucose concentration in fluids such as blood. Also used by brewers to calculate glucose concentration in alcohol production. The NADPH formed by the pentose phosphate pathway occurs in equimolar ratios with the substrates of the pathway, therefore the concentration of NADPH formed during the reaction is equivalent to the concentration of the substrates of the pathway. NADPH and NADH absorb UV light at 340 nm.
What is the Specific assay for determination of concentration of glucose in blood using the pentose phosphate pathway?
pH 7.2 buffer
Glucose-6-phosphate dehydrogenase (excess)
Serum (contains blood glucose)
The is reaction incubated till all the glucose in the blood sample has been converted to 6-phosphogluconate and NADPH
The NADPH formed is measured at 340 nm in a spectrophotometer
Note: polystyrene plastics do not absorb at 340 nm. Therefore. plastics cuvettes could be used to measure absorbance of the NADPH formed
Moles of NADPH formed is calculated and that would be equivalent to moles of glucose in the blood sample since the molecules of the pentose phosphate pathway react in equimolar ratios.
What is significant about L-DOPA (dihydroxyphenylalanine)?
it is the precursor for melanin and dopamine.
What is a nother name for ascorbic acid? What is its function?
Vitamin C. Cofactor in enzymatic reactions such as collagen synthesis. Also an antioxidant.
is the main structural protein of the various connective tissues in animals.
disease resulting from a deficiency of vitamin C, which is required for the synthesis of collagen in humans. Scurvy often presents itself initially as symptoms of malaise and lethargy, followed by formation of spots on the skin, spongy gums, and bleeding from the mucous membranes. As scurvy advances, there can be open, suppurating wounds, loss of teeth, jaundice, fever, neuropathy and death.
What is the benefit of stong acid in the stomach?
denatures proteins, gives proteolytic enzymes better access.
moves group within molecule
moves groups intermolecularly
group of lipid compounds that are derived enzymatically from fatty acids. regulate the contraction and relaxation of smooth muscle tissue.
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