Chapter 24
Nutrition, Metabolism, and Body Temperature Regulation
931
24
Absorptive State
Te absorptive state, or
fed state,
is the time during and shortly af-
ter eating, when nutrients are flushing into the blood from the GI
tract. During the absorptive state anabolism exceeds catabolism
and nutrients are stored
(Figure 24.18)
. Glucose is the major
Metabolic controls act to equalize blood concentrations of
energy sources between two nutritional states—the
absorptive
state
and the
postabsorptive state
. People who eat “three squares”
a day are in the absorptive state for the four hours during and
aFer each meal and in the postabsorptive state in the late morn-
ing, late aFernoon, and all night.
(b) Principal pathways of the absorptive state
(a) Major events of the absorptive state
Major energy fuel:
glucose (dietary)
Liver metabolism:
amino acids deaminated and
used for energy or stored as fat
Major metabolic thrust:
anabolism and energy storage
Amino acids
Amino acids
ATP
Protein
Proteins
Keto acids
Triglycerides
Triglycerides
Triglycerides
Glucose
Glycogen
Glycogen
Glycogen
Protein
Glucose
Glucose
Glucose
Amino acids
Keto acids
Triglycerides
CO
2
+ H
2
O +
Triglycerides
Glycerol and
fatty acids
Glucose
Gastrointestinal
tract
In liver:
In all tissues:
In adipose
tissue:
Glucose
Fatty
acids
Fatty
acids
Glyceraldehyde
3-phosphate
Glycerol
Glycerol
Fatty
acids
In muscle:
CO
2
+ H
2
O
+
ATP
CO
2
+ H
2
O
+
ATP
CO
2
+ H
2
O
+
ATP
Figure 24.18
Major events and principal metabolic pathways of the absorptive state.
Although not indicated in (b), amino acids are also taken up by tissue cells and used for protein
synthesis, and fats (triglycerides) are the primary energy fuel of muscle, liver cells, and adipose tissue.
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