ch 12 - Bioenergetics and Regulation of Metabolism Flashcards
open systems
biological systems that exchange both energy and matter with the environment
Internal engery
italicized U - sum of all of the different interactions between and within atoms in a system; vibration, rotation, linear motion, and stored chemical energies are all contributors
First Law of Thermodynamics
deltaU=Q-W. Work refers to changes in pressure and volume. Q = heat or heat exchange
enthalpy
delta-italicized H. measures overall change in heat of a system during a rxn. at constant pressure and volume, enthalpy and thermodynamics heat exchange (Q) are equal
entropy
delta italicized S. measures the degree of disorder or energy dispersion in a system. Units J/K
Gibbs Free energy equation
deltaG=deltaH-TdeltaS. H is enthalpy. T is temp. S is entropy. Spontaneous reactions move forward and have a negative G value. Moves toward zero as reaction approaches equilibrium
standard free energy
deltaG-degree sign - energy change that occurs at standard concentrations of 1 M, pressure of 1 atm and temp of 25 C.
standard free energy relationship to Gibb’s free energy
deltaG=delta G-degree sign + RT ln (Q). delta G is Gibb’s free energy. delta G-degree sign is standard free energy. R is universal gas constant. T is temp. Q is reaction quotient.
modified standard state
modified because a 1 M concentration of protons would have pH 0 and be far too acidic. modified standard state is [H+]=10^-7 M with pH of 7. with this delta G-degree sign is changed to delta G-degree sign’.
amount of energy produced by ATP under physiological conditions
30 kJ/mol
role of cAMP and amount and deltaG-degree sign’
second messenger, delta G degree sign’ = -50.4 kJ/mol
function of creatine phosphate and modified standard state of free energy
direct phosphorylation in muscle, delta G degree sign’ = -43.3 kJ/mol
function of ATP and modified Gibb’s free energy
energy turnover in all cell types (mid-level energy carrier); delta G degree sign’ = -30.5 kJ/mol
function and modified Gibb’s free energy of Glucose 6-phosphate
intermediate of glycolysis and gluconeogenesis; delta G degree sign’ = -13.9
function and modified Gibb’s free energy state of AMP
ATP synthesis; delta G degree sign’ = -9.2
ADP
adenosine diphosphate - produced if one phosphate group is removed from ATP.
AMP
adenosine monophosphate - produced if two phosphate groups are removed from ATP
what do many coupling reactions use
energy harnessed from hydrolysis of ATP
ATP cleavage
transfer of a high-energy phosphate group from ATP to another molecule, which generally activates or inactivates the target molecule
Phosphoryl group transfers
ATP provides phosphate group as a reactant.
Hess’s law to calculate the difference in free energy between reactants and products
creatine phosphate + H2O -> creatine + P sub i – (free energy = -43.3 kJ/mol) + ADP + P sub i -> ATP + H2 – (free energy = 30.5 kJ/mol for a total of creatine phosphate + ADP -> creatine + ATP (free energy total = -12.8 kJ/mol)
half-reactions
division of oxidation-reduction reactions into components to determine how many e-s are being transferred. Number of e-s must be equal on both sides of reaction. Spontaneous have -delta G and positive elecromotive force (E)
high-energy electron carriers in the cytoplasm
soluble - NADH, NADPH, FADH2, ubiquonone, cytochromes and glutathione
flavin mononucleotide (FMN)
membrane-bound e- carrier embedded in the inner mitochondrial membrane; bonded to complex I of ETC.
Flavoproteins
contain modified vit B2 (riboflavin). nucleic acid derivatives, generally either flavid adenine dinucleotide (FAD) or flavin mononucleotide (FMN); present in mitochondria and chloroplasts as e- carriers; function in modification of other B vits to active forms and as coenzymes for enzymes in the oxidation of fatty acids, decarboxylation of pyruvates and the reduction of glutathione
postprandial state
absorptive or well-fed state marked by great anabolism (synthesis of biomolecules) and fuel storage than catabolism (breakdown of biomolecules for energy). lasts generally 3-5 hours after eating; glucose levels rise and stimulate release of insulin
major target tissues for insulin
liver, muscle, adipose tissue
tissues insensitive to insulin
nervous tissue and RBCs
hormones that oppose actions of insulin (counterregulatory hormones)
Glucagon, cortisol, epi, norepi, growth hormone
Postabsorptive (fasting) state
characterized by counterregulatory hormones; stimulate glycogen degredation and release of glucose in the blood; hepatic gluconeogenesis is stimulated by glucagon but glycogenolysis begins almost immediately at the beginning of the postabsorptive state and takes about 12 hours to hit max velocity.
Prolonged Fasting (starvation)
glucagon and epi are markedly elevated; increased levels of glucagon result in rapid degradation of glycogen stores in the liver when depleted gluconeogenic activity maintains glucose levels; at 24 hours gluconeogenesis takes over for glucose production. After weeks, muscle tissue will utilize fatty acids as major fuel source and brain will adapt to using ketones for energy, reserving amino acids and proteins. Glucose is used for those cells with little or no mitochondria
peptide hormones
water-soluble, able to rapidly adjust the metabolic processes of cells via second messenger cascades (ex insulin)
amino acid-derivative hormones
fat-soluble; enact longer-range effects by exerting regulatory actions at the transcriptional level (ex. thyroid hormones and steroid hormones like cortisol)
Insulin
peptide hormone secreted by the beta-cells of the pancreatic islets of Langerhans; key player in uptake and storage of glucose
tissues that require insulin for effective uptake of glucose
adipose and resting skeletal
tissues in which glucose uptake is not affected by insulin
nervous tissue, kidney tubules, intestinal mucosa, RBCs (erythrocytes), beta-cells of the pancreas
glucokinase and glycogen synthase
insulin increases glycogen synthesis in the liver by increasing activity of these enzymes
glycogen phosphorylase and glucose-6-phosphatase
insulin decreases these enzymes in the liver - they promote glycogen breakdown
Increasing effects of insulin on metabolism of fats
-glucose and triacylglycerol uptake by fat cells; -lipoprotein lipase activity increases, which clears VLDL and chylomicrons from the blood; -triacylglycerol synthesis (lipogenesis) increases in adipose tissue and the liver from acetyl-CoA
decreasing effects of insulin on metabolism of fats
Insulin decreases: -tracylglycerol breakdown (lipolysis) in adipose tissue; -formation of ketone bodies by the liver
controller of insulin secretion
plasma glucose; above threshold of 100 mg/dL or abot 5.6 mM of glucose, insulin secretion is directly proportional to plasma glucose
Glucagon
peptide hormone secreted by the alpha-cells of the pancreatic islets of Langerhans; primary target is the hepatocyte
effects of glucagon
-increased liver glycogenolysis (activates glycogen phosphorylase and inactivates glycogen synthase); -increased liver gluconeogenesis (promotes conversion of pyruvate to phosphoenolpyruvate by pyruvate carboxylase and phosphoenolpyruvate carboxykinase (PEPCK); increases conversion of fructose 1,6-bisphosphate to fructose 6-phosphate by fructose-1,6-bisphosphatase); -increased liver ketogenesis and decreased lipogenesis; -increased lipolysis in liver (activates hormone-sensitive lipase in liver); not a major fat-mobilizing hormone
important promoter of glucagon
low plasma glucose (hypoglycemia); some amino acids, especially the basic one (arginine, lysine, and histidine); secreted in response to a meal rich in protein
important inhibitor of glucagon
high plasma glucose (hyperglycemia)
glucocorticoids
class of corticosteroids that come from the adrenal cortex; responsible in part for stress response; cortisol is an example
Cortisol
glucocorticoid and steroid hormone secreted with most forms of stress; promotes mobilization of energy stroes through the degradation and increased delivery of amino acids and increased lipolysis; elevates bgl, increasing glucose availability for nervous tissue
mechanisms through which cortisol increases availability of glucose for nervous tissue
- inhibits glucose uptake in most tissues (muscle, lymphoid and fat) and increases hepatic output of glucose via gluconeogenesis. 2. has permissive function that enhances the activity of glucagon, epi, and other catecholamines
Catecholamines
secreted by adrenal medulla. epi and norepi (adrenaline and noradrenaline). increase activity of liver and muscle glycogen phosphorylase (promoting glycogenolysis in muscle and liver). act on adipose tissue to increase lipolysis by increasing activity of hormone-sensitive lipase
Thyroid hormones
kept largely constant; increase the basic metabolic rate evidenced by increased O2 consumption and heat production; primary effects in lipid and carb metabolism. accelerate cholesterol clearance from plasma and increase rate of glucose absorption from the small intestine. Epi requires it to have a significant metabolic effect
thyroxine (T sub 4)
occurs after latency of several hours but may last for days; increases metabolic rate. subscript is number of iodine atoms in hormone
triiodothyronine (T sub 3)
produces more rapid increase in metabolic rate than T sub 4 and has a shorter duration of activity. subscript is number of iodine atoms in the hormone
deiodonases
enzymes that remove iodine from a molecule and are located in target tissues to convert T4 to T3
respirometry and respiratory quotient
respiratory quotient differs depending on the fuels being used by an organism. RQ = CO2produced/O2consumed for the complete combustion of a fuel source
Calorimeters
measure basal metabolic rate (BMR) based on heat exchange with environment.
Ghrelin
hormone secreted by the stomach in response to signals of an impending meal. sight, sound, taste and smell; stimulates release of orexin
orexin
hormone that further increases appetite; also involved in sleep-wake cycle; also triggered by hypoglycemia
Leptin
hormone secreted by fat cells that decrease appetite by suppressing orexin production
Body Mass Index (BMI)
mass/(height squared)
