Metabolic Transformations

metabolism

molecules, pathways, and regulation! The interconversion of chemical compounds in the body

50%

percent of carbohydrates in a normal diet

40%

percent of lipids in a normal diet

10%

percent of protein in a normal diet

normal metabolism

adaptation to fasting, starvation, exercise, pregnancy, or lactation

abnormal metabolism

results from nutrition deficiency, enzyme deficiency, hormonal abnormalities, drugs, toxins, or genetics

wasting

occurs when there is less metabolic fuels than the energy expenditure

obesity

occurs when there is more metabolic fuels than the energy expenditure

anabolic

pathways that involve synthesis; endothermic

ex: amino acids --> proteins

catabolic

pathways that involve breakdown; exothermic

ex: glycolysis

amphibolic

pathways that link anabolic and catabolic pathways

ex: citric acid cycle

glucose

the metabolic fuel for most tissues

fasting

in the ___________ state, glucose must be spared for use by the CNS (largely dependent) and for erythrocytes (wholly dependent)

fatty acis

tissues that can oxidize other fuels for glucose do so; muscle and liver oxidize _________________

ketone bodies

the liver synthesizes _____________________ from fatty acids to export to muscle and other tissues

amino acids

________________________ are used for gluconeogenesis when glucose is depleted

digestion

the gateway to metabolism

acetyl-CoA

all products (carbohydrates, protein, or fat) are catabolized into ________________ which is oxidized by the citric acid cycle

liver

regulates blood concentration of many water-soluble metabolites; is constantly working, as it performs gluconeogenesis, lipogenesis, glycogenolysis, and glycogenesis (with the kidney) - also synthesizes major plasma proteins (albumin) and deaminates amino acids in excess

subcellular

at the _________________ level, cytosol, mitochondria, endoplasmic reticulum, and ribosomes are involved

ATP

the energy "currency" common to all life forms: links energy-releasing pathways with energy-needing pathways

essential

_______________ amino acids cannot be synthesized in the body and must be present in the diet

carbohydrates

major metabolic processes: glycolysis, citric acid cycle, pentose phosphate pathway

lipids

major metabolic processes: esterification, beta-oxidation, lipolysis, lipogenesis, ketogenesis, cholesterogenesis, steroidogenesis, and the citric acid cycle

beta-oxidation

metabolic process that converts dietary fatty acids into acetyl-CoA to be used in the citric acid cycle

protein

major metabolic processes: transamination, deamination, citric acid cycle

regulatory enzymes

regulation of metabolism is achieved by control of one or more key reactions in the pathway, catalyzed by regulatory enzymes

nonequilibrium

regulatory enzymes usually catalyze __________________ (rate limiting) reactions in a metabolic pathway

rapid

______________ mechanisms of regulation:

-alteration of substrate membrane permeability

-conversion of an inactive to an active enzyme

-allosteric modifications

-hormones and signaling pathways

slow

____________ mechanisms of regulation:

-alteration of the rate of translation of mRNA at the ribosomal level

-induction of new mRNA formation

-repression of new mRNA formation

-availability of cofactors

fed

in the ______ state:

-metabolic fuel reserves are replenished

-glucose is the major fuel for oxidation in most tissues

-there is a concurrent increase in the respiratory quotient from 0.8-1

respiratory quotient

the ratio of carbon dioxide produced to oxygen consumed

insulin

glucose uptake into muscle adipose tissue is controlled by ____________________

mobilized

during fasting, metabolic fuel reserves are ________________

glucose

concentrations of metabolic fuels:

fed: 5.5

40h fasting: 3.6

7 day starvation: 3.5

free fatty acids

concentrations of metabolic fuels:

fed: 0.3

40h fasting: 1.15

7 day starvation: 1.19

ketone bodies

concentrations of metabolic fuels:

fed: negligible

40h fasting: 2.9

7 day starvation: 4.5

Triacylglycerols (triglycerides)

A glycerol molecule esterified to three fatty acid molecules; the most common form of fat storage in the body

Overall nonpolar and hydrophobic

Can be seen in oily droplets