Ch06
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Transcript of Ch06
Basic Biochemistry IIBCM301
Chapter 6:Integration, Specialization, and Regulation of
Metabolism
At this point, we’ll consider how organisms arrange/organize the metabolic symphony to meet their energy needs.
Discussion will include how:Body maintains
energy balance (homeostasis)
It deals with starvation
It responds to the loss of control from diabetes mellitus
Biochemistry & nutrition
Table 24-2, p.666
Fig. 24-2, p.668
Food pyramid
Obesity
-Define as weighing at least 20% more than their ideal weight- several inventions: artificial sweeteners, fat substitutes- protein leptin plays a role in the control of obesity
- Has been established in mice- in mice, leptin is 16kDa protein that produced by obesity (ob) gene- mutation in this gene will lead to deficiency of leptin
Organ specialization
Brain
Muscle The Cori Cycle
Liver The Glucose Alanine Cycle
The fate of G6P varies with metabolic requirements – depends on the glucose demandG6P can be converted to glucose by glucose-6-
phosphatase (transport via bloodstream to the peripheral organs)
G6P can be converted to glycogen – when body’s demand for glucose is low
G6P can be converted to acetyl-CoA via glycolysis and action of pyruvate dehydrogenase (this glucose-derived acetyl-CoA used in the synthesis of f.acids)
G6P can be degraded via pentose phosphate pathway (to generate NADPH required for f.acids biosynthesis and liver’s many other biosynthetic functions)
The liver can synthesize or degrade TAGsWhen metabolic fuel is needed, f.acids are degraded to
acetyl-CoA and then to ketone bodies (export via bloodstream to the peripheral tissues)
When the demand is low, f.acids are used to synthesize TAGs (secreted into the bloodstream as VLDL for uptake by adipose tissue)
Amino acids are important metabolic fuelThe liver degrades amino acids to a variety of
intermediates (begin with a.acid transamination to yield α-keto acid, via urea cycle excreted urea)
Glucogenic a.acid – converted to pyruvate / OAA (TCA cycle intermediates)
Ketogenic a.acid – converted to ketone bodies
Kidney
Functions: to filter out the waste product urea from the bloodstream: to concentrate it for excretion: to recover important metabolites (glucose): to maintain the blood pH
Overall reaction in kidney: Glutamine → α-ketoglutarate + NH4
+
During starvation, the α-ketoglutarate enters gluconeogenesis (kidneys generate as much as 50% of the body’s glucose supply)
α-ketoglutarate : converted to malate (TCA cycle) : pyruvate (oxidized to CO2) or via OAA to PEP: converted to glucose via gluconeogenesis
Hormones and second messengers
Fig. 24-5, p.671
Hormones reacts as the intercellular messengersHormones transported from the sites of their synthesis to
the sites of action by the bloodstream
Some typical hormones:
- steroids (estrogens, androgens)
- polypeptides (insulin and endorphins)
- a.acid derivatives (epinephrine and norepinephrine)
Hormones help maintaining homeostasis (the balance of biological activities
Table 24-3, p.672
Fig. 24-7, p.673
Control system mechanism
Hormone releasing factor
Fig. 24-8, p.674
Second messenger e.g cyclic AMP (cAMP)
p.676
Fig. 24-9a, p.675
Fig. 24-9b, p.675
Hormones & metabolism The effects of hormones triggered
the responses within the cell There are three hormones play a
part in the regulation of CHO metabolism
Epinephrine, insulin and glucagon Epinephrine: acts on muscle tissue,
to raise level of glucose on demand, when it binds to specific receptors, it leads to increased level of glucose in blood, increased glycolysis in muscle cells and increased breakdown of f.acid for energy
p.681
Fig. 24-14, p.682
Glucagon: acts on liver, to increase the availability of glucose, when it binds to specific receptors, it leads to increased level of glucose in blood.
Metabolic homeostasis
Table 24-4, p.685
Metabolic adaptation During prolonged starvation, the brain slowly
adapts from the use of glucose as its soul fuel source to the use of ketone bodies, shift the metabolic burden form protein breakdown to fat breakdown
Diabetes mellitus is a disease in which insulin either not secreted or doesn’t stimulate its target tissues → high [glucose] in the blood and urine. Abnormally high production of ketone bodies is one of the most dangerous effects of uncontrolled diabetes