Biochem chapter 12 mcat

enthalpy

changes in —- in closed biological system are equal to changes in internal energy, which is equal to heat exchange within the environment

entropy

measure of energy dispersion in a system

closed

no work is performed in —- biological systems because pressure and volume remain constant

atp

• mid level energy molecule

• contains high energy phosphate bonds that are stabilized upon hydrolysis by resonance, ionization, and loss of charge repulsion

hydrolysis and coupling

ATP provide energy through —- and —- to energetically unfavorable reactions

phosphoryl transfers

ATP can also participate in —- —- — as a phosphate donor

flavoproteins

a subclass of electron carriers that are derived from riboflavin (B2)

equilibrium

this is an undesirable state from most biochemical reactions because organisms need to harness free energy in order to survive

postprandial/well fed/ absorptive

in this state insulin secretion is high and anabolic metabolism prevails

postabsorptive/fasting

in this state insulin secretion decreases while glucagon and catecholamine secretion increases

-seen in short term fasting (overnight)

-there is a transition to catabolic metabolsim

prolonged fasting/starvation

in this state there are dramatic increases in glucagon and catecholamine secretion

• most tissues rely on fatty acids

• at maximum 2/3 of the brains energy can come from ketone bodies

insulin

• causes a decrease in blood glucose levels by increasing cellular uptake

• increases the rate of anabolic metabolism

• secreted by pancreatic B cells and is regulated by blood glucose levels

glucagon

• increases blood glucose levels by promoting gluconeogenesis and glycogenesis in the liver

• secreted by pancreatic A cells and is stimulated by both low blood sugar and high AA 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 BMR through their sympathetic nervous activity

thyroid hormones

modulate the impact of other metabolic hormones and have a direct impact on BMR

t4

converted to t3 in tissues

t3

more potent than the other option, but has a shorter half life and is available in lower concentrations in the blood

leptin

hormone released by fat cells that decrease appetite by suppressing orexin production — genetic variations in this molecule and its receptors have been implicated in obesity

ghrelin

secreted in the stomach in response to signals of an impending meal (sight, sound, taste, and especially smell). Increases appetite and stimulates the secretion of orexin

orexin

increases appetite and is involved in alertness and sleep-wake cycle. Hypoglycemia is a trigger for release

liver

most metabolically diverse tissue

• responsible for the maintenance of blood glucose levels by glycogenolysis and gluconeogenesis in response to pancreas hormone secretions

• also participates in the processing of lipids, bile, cholesterol, urea, and toxins

adipose tissue

stores lipids under the influence of insulin and releases them under the influence of epinephrine

resting muscle

conserves carbohydrates in glycogen stores and uses free fatty acids from the blood stream for energy

active muscle

may use anaerobic metabolism, oxidative phosphorylation of glucose, direct phosphorylation from creatine phosphate, or fatty acid oxidation — depending on type and duration of activity

cardiac muscle

uses fatty acid oxidation in both well-fed and fasting states

brain and nervous system

consumes glucose in all metabolic states, except for prolonged fasts where 2/3 of fuel may come from ketone bodies