Biochemistry Chapter 12: Bioenergetics and Regulation of Metabolism Flashcards
Biological systems are open when:
matter and energy can be exchanged with the environment
Biological systems are closed when:
only energy can be exchanged within the environment
In a closed system changes in enthalpy are equal to:
changes in internal energy, which is equal to heat exchange within the environment
Is work performed in a closed biological system?
no - pressure and volume remain constant
Entropy
a measure of energy dispersion in a system.
Physiological concentrations are usually ____ than standard concentrations.
much less
Free energy calculations must be adjusted for:
pH, temperature and concentrations
ATP contains:
high-energy phosphate bonds that are stabilized upon hydrolysis by resonance, ionization and loss of charge repulsion.
ATP provides energy through
hydrolysis and coupling to energetically unfavorable reactions. Can also participate in phosphoryl group transfers as a phosphate donor.
Half-reactions
breakdown of biological oxidation and reduction reactions. Provide useful information about stoichiometry and thermodynamics
Electron carriers may be:
soluble or membrane-bound
Flavoproteins
one subclass of electron carriers that are derived from riboflavin.
Why is equilibrium generally an undesireable state for biochemical reactions>
Organisms need to harness free energy to survive.
Postprandial/well-fed (absorptive) state
insulin secretion is high and anabolic metabolism prevails.
Postabsorptive (fasting) state
insulin secretion decreases while glucagon and catecholamine secretion increases
- short term fasting (overnight).
- transition to catabolic metabolism
Starvation state (prolonged fasting)
dramatically increases glucagon and catecholamine secretion (most tissues rely on fatty acids)
Insulin and blood glucose levels
decreases
Insulin and rate of anabolic metabolism
increases
Insulin secretion by pancreatic beta-cells is regulated by
blood glucose levels
Glucagon and blood glucose levels
increases through promoting gluconeogenesis and glycogenolysis
Glucagon secretion by pancreatic alpha-cells is stimulated by
low glucose and high protein levels
Glucocorticoids
increase blood glucose in response to stress by mobilizing fat stores and inhibiting glucose uptake (increase the impact of glucagon and catecholamines)
Catecholamines
Promote glycogenolysis and increase basal metabolic rate through their sympathetic nervous system activity
Thyroid hormones
Modulate the impact of other metabolic hormones and have a direct impact on basal metabolic rate
T3
More potent than T4, but has a shorter half-life and is available in lower concentration sin the blood
T4
converted to T3 at the tissues
What is the most metabolically diverse tissue
Liver
Hepatocytes
responsible for the maintenance of the blood glucose levels by glycogenolysis and cluconeogenesis in response to pancreatic hormone activity.
Liver participates in the processing of:
lipids and cholesterol, bile, urea and toxins
Adipose tissue stores lipids:
under the influence of insulin and releases them under the influence of epinephrine
Resting muscle potential
conserves carbohydrates in glycogen stores and uses free fatty acids from the bloodstream
Active muscle
may use anaerobic metabolism, oxidative phosphorlyation of glucose, direct phosphorylation from creatine phosphate or fatty acid oxidation, depending on fiber type and exercise duration
Cardiac muscle uses:
fatty acid oxidation in both the well-fed and fasting states
Metabolic rates can be measured using:
calorimetry, respirometry, consumption tracking or measurement of blood concentrations of substrates and hormones
Respiratory quotient
estimates the composition of fuel that is actively consumed by the body
What three hormones play a role in body mass?
leptin, ghrelin and orexin
What do long-term changes in body mass result from?
Changes in lipid storage
Changes in consumption must ___ to cause weight change
a threshold - lower for weight gain than weight loss.
