Intro to metabolism Flashcards
the principal donor of free energy in biological systems
ATP
used primarily to generate ATP
NADH
used primarily in reductive biosynthesis
NADPH
what causes PKU
there’s a defect in phenylalanine hydroxylase so phenylalanine can’t be degraded and tyrosine cant be made
-tetrahydrobiopterin is a cofactor
what is downregulated in PKU
-tissue proteins
-melanin
-catecholamine
-fumarate acetoacetate
what is upregulated in when phenylalanine is not degraded?
phenylpyruvate, phenyllactate, phenylacetate
-toxic compounds in neurological tissue that cause intellectual disabilities
how is tetrahydrobiopterin synthesized
in the body from GTP
what is the treatment for PKU?
-restrict phenylalanine in diet (not completely)
-supplement with tyrosine
if you discontinue your tyrosine rich diet, what you happen to you?
your IQ can decline
atypical non-classical malignant phenylketonuria
-defect in either the synthesis of tetrahydrobiopterin or dihydropterin reductase, which regenerates the cofactor
-severe CNS disorders that don’t respond to diet change
how can neurological symptoms that arise from atypical PKU be resolved?
L-dopa and 5-hydroxytryptophan
THB is a cofactor that is required for synthesis for________________________________
dopamine, epinephrine, norepinephrine, and serotonin
the absorptive state
-store energy as fat
-perform anabolic reactions (repair what might’ve broken down during fast)
-fed state after meal
the fasting state
-maintain blood glucose
-limit proteolysis
glycolysis
metabolize glucose to pyruvate + energy
gluconeogenesis
synthesize glucose from precursors
fatty acid oxidation
Metabolize fatty acids to acetyl CoA + energy
citric acid cycle
metabolize acetyl CoA to carbon dioxide + energy
glycogenesis
convert glucose to glycogen for storage
glycogenolysis
convert glycogen to glucose when needed
pentose phosphate pathway
convert glucose to ribose-5-phosphate for nucleotide synthesis + energy + NADPH
ketone body synthesis
produce an alternative energy source during starvation
oxidative phosphorylation
convert energy to ATP
urea cycle
convert excess ammonia to urea for excretion
what is stage 1 of catabolism
Complex macromolecules of starch, protein,
and triacylglycerols are broken down into smaller units,
such as monosaccharides, amino acids, glycerol, and
fatty acids. During this stage, little or no free energy
is trapped.
what is stage 2 of catabolism
The simple molecules of different kinds are
catabolized to a few molecules that can be oxidized to
carbon dioxide and water along a common pathway. In
this stage, some free energy is trapped as ATP.
what is stage 3 of catabolism
It consists of the citric acid cycle, the electron
transport system and oxidative phosphorylation.
Together, these processes oxidize acetyl CoA to CO2
and water, and produce most of the ATP in the cell.
where are pathways compartmentalized
-cytosol (glycolysis, pentose phosphate pathway, fatty acid synthesis)
-mitochondrial matrix (citric acid cycle, oxidative phosphorylation, oxidation of fatty acids, ketone body formation)
-cytosol plus mitochondrial matrix (gluconeogenesis, urea cycle)
signals the fed state, the availability of glucose in the blood
insulin
signal the fasting state in which the level of glucose in the blood is low
glucagon and epinephrines
signals stressful states when mobilization of fuel is required
epinephrine
what are some non-hormonal regulation of metabolic pathways
-availability of substrates
-allosteric control
-gene expression
interplay of hormonal and non-hormonal regulation of metabolic pathways
-covalent modification: hormone-triggered reaction cascades result in the covalent modification of a key enzyme of a pathway
-ex. glucose—->glycogen glycogen—->glucose
glucose —-> glycogen (fed state)
glycogenesis
glucose —–> pyruvate (fed state)
glycolysis
glycogen —-> glucose (fasting state)
glycogenolysis
pyruvate —-> glucose (fasting state)
gluconeogenesis
flow of key metabolic intermediates
glucose 6-phosphate
pyruvate
acetyl CoA
what are the different pathways that glucose 6-phosphate is involved in?
-glucose in gluconeogenic tissues
-glucose 1-phosphate used in glycogen synthesis
-pyruvate via glycolysis
-ribose 5-phosphate for nucleotide synthesis, via pentose phosphate pathway
what pathways is pyruvate involved in?
-oxaloacetate and metabolized via the citric acid cycle
-acetyl coA by pyruvate dehydrogenase
-alanine via transamination
-lactate in muscle tissue
what pathways is acetyl coA involved in?
-oxidized to CO2 via the citric acid cycle
-fatty acid synthesis
-3-hydroxy-3-methylglutary CoA, a precursor of cholesterol, ketone bodies
liver in metabolism
-maintenance of blood glucose levels
-during fed state, it takes up excess glucose and stores it as glycogen or converts it to fatty acids
-during the fasting state, it exports glucose derived from glycogen and gluconeogenesis
-fatty acid synthesis
-ketone body synthesis during fasting state
-synthesis of plasma lipoproteins
skeletal muscle in metabolism
-maintains large stores of glycogen which provide a source of glucose for energy during exertion
-in resting muscle the preferred fuel is fatty acids
-muscle protein may be mobilized as a fuel source
heart muscle in metabolism
contains essentially no fuel reserves and must be continuously supplied with fuel from the blood, primarily fatty acids
adipose in metabolism
-primary function is storage of metabolic fuel in the form of triacylglycerols
-during the fed state, it synthesizes triacylglycerols from glucose and fatty acids
-during the fasting state triacylglycerols are converted to glycerol and fatty acids
brain in metabolism
-normally uses glucose as an exclusive fuel, except during starvation when it can adapt to use ketone bodies
-contains essentially no fuel reserves and must be continuously supplied with fuel from the blood
