Carbohydrate and Lipids Metabolism Flashcards
(22 cards)
the formation of new glucose molecules from noncarbohydrate precursors (lactate, pyruvate,
glycerol, and certain -keto acids (molecules derived from amino acids).
Gluconeogenesis
Primarily occurs in the liver
and Occurs secondarily in kidney
Gluconeogenesis
PEP synthesis from pyruvate requires two enzymes:
pyruvate carboxylase
PEP carboxykinase
found only in liver and kidney,
catalyzes the irreversible hydrolysis of glucose- 6-
phosphate to form glucose and Pi. Glucose is subsequently
released into the blood.
Glucose-6-phosphatase
is more effective if transient accumulation of
product is funneled back through the cycle.
Flux control
is an energy-consuming process. Instead of
generating ATP (as in glycolysis), gluconeogenesis requires
the hydrolysis of six high energy phosphate bonds
Gluconeogenesis
lactate is
released by skeletal muscle
during exercise.
Cori cycle
a product of fat metabolism in adipose tissue, is
transported to the liver in the blood and then converted to
glycerol-3-phosphate by glycerol kinase.
Glycerol
When fructose-1-phosphate enters the glycolytic pathway, it
is first split into
dihydroxyacetone phosphate and glyceraldehyde
is the storage form of glucose
Glycogen
Fats (or triglycerides) within the body are ingested as food or synthesized by adipocytes or hepatocytes from
carbohydrate precursors
is associated with carbohydrate metabolism, as products of glucose (such as acetyl CoA) can be converted into lipids.
Lipid metabolism
When food reaches the small intestine in the form of chyme, a digestive hormone called
cholecystokinin
Within the intestinal cells, these triglycerides are packaged along with cholesterol molecules in phospholipid vesicles called
chylomicrons.
The process of breaking down stored triglycerides into fatty acids and glycerol by triglyceride lipase, which is stimulated by adrenaline and glucagon.
Lipolysis
If excessive acetyl CoA is created from the oxidation of fatty acids and the Krebs cycle is overloaded and cannot handle it, the acetyl CoA is diverted to create
ketone bodies
serve as fuel in times of prolonged starvation or
when patients suffer from uncontrolled diabetes and cannot utilize most of the circulating glucose.
Ketones
n this ketone synthesis reaction, excess acetyl CoA is
converted into
hydroxymethylglutaryl CoA
or
(HMG CoA).
s a precursor of cholesterol and is an intermediate
that is subsequently converted into β-hydroxybutyrate, the
primary ketone body in the blood
HMG CoA
creation of lipids (fat) from the acetyl CoA and
takes place in the cytoplasm of adipocytes (fat cells) and
hepatocytes (liver cells).
Lipogenesis
Fatty acids are synthesised within the cytoplasm of
hepatocytes, following maximal conversion
of
glucose to glycogen.
creates an elongated fatty acid chain from the malonyl-CoA molecules, adding two carbon atoms for each molecule of malonyl-coA
Fatty acid synthase
