Biochemistry 12: Bioenergetics and Regulation of Metabolism Flashcards
open biological systems
a system in which matter and energy can be exchanged with the environment
ex. consumption, elimination, respiration
closed biological systems
a system in which only energy can be exchanged with the environment
ex. cellular systems
internal energy for a closed system
the sum of all the different interactions between and within atoms in a system
dU = Q - W
no work done, so enthalpy = changes in internal energy
how does a biological system perform work?
no work is performed in a closed biological system because pressure and volume remain constant
at constant pressure and volume, enthalpy dH = heat exchange Q are equal
ATP
mid-level energy molecule
has high-energy phosphate bonds stabilized upon hydrolysis by resonance, ionization, and loss of charge repulsion
provides energy through hydrolysis and coupling to energetically unfavorable reaction
can also participate in phosphoryl group transfers as a phosphate donor
half reactions
the breaking down of oxidation and reduction reactions
flavoproteins
proteins which contain a modified vitamin B2 or riboflavin
derived from nucleic acids such as flavin adenine dinucleotide (FAD) or flavin mononucleotide (FMN)
present in mitochondria and chloroplasts as electron carriers
involved in modification of other B vitamins to active forms
function as coenzymes for enzymes in the oxidation of fatty acids, decarboxylation of pyruvate, and the reduction of glutathione (helpful in oxidative stress)
postprandial state / absorptive state / well-fed state
state which occurs shortly after eating
greater anabolism than catabolism (more storage and synthesis than breakdown)
generally lasts 3 - 5 hours after eating
high insulin levels
what are the three major target tissues for insulin?
liver
muscle
adipose tissue
how does insulin affect the liver?
promotes glycogen synthesis
increasing the activity of glucokinase and glycogen synthase
once glycogen stores are filled, liver converts excess glucose to fatty acids and triacylglycerols
how does insulin affect muscle?
promotes glycogen and protein synthesis
also promotes glucose entry
how does insulin affect adipose tissue?
promotes triacylglycerol synthesis and glucose entry
which cells are insensitive to insulin?
nervous tissue
red blood cells
how do nervous tissue and red blood cells obtain energy in a well fed state?
nervous tissue: oxidation of glucose to CO2 and water
RBC: anaerobic glycolysis
(do so without interference from insulin because they must be able to absorb glucose even in low concentrations)
postabsorptive / fasting state
release of counterregulatory hormones - glucagon, cortisol, epinephrine, norepinephine and growth hormone (they oppose the activity of insulin)
observed in short term (overnight) fasting
more catabolic metabolism
