Date post: | 03-Jun-2015 |
Category: |
Technology |
Upload: | nur-izzati |
View: | 83 times |
Download: | 0 times |
Metabolic interrelationship
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
Table 24-2, p.666
Fig. 24-2, p.668
Food pyramid
Review of metabolism
Glycolysis Gluconeogen
esis The pentose
phosphate pathway
Β oxidation and fatty acids synthesis
Amino acids degradation and synthesis
The citric acid cycle
Oxidative phosphorylation
Brain
Muscle
Liver
The liver can synthesize or degrade TAGs When 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
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
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.
Table 24-4, p.685
During prolonged starvation or fasting, 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
Dieting – to lose excess weight. Diet forced the body to follow the same adjustment like starvation or fasting but a more moderate or controllable pace. Dieting is not free of problems, therefore it is advisable to undergo diet under supervision of physician or nutritionist.