6-7. Bioenergetics & Control of Metabolism Flashcards
What does the ability of work depend on?
The conversion of one form of energy to another
When is the presence of energy revealed?
Only when change occurs
What is chemical energy?
Energy liberated or required when atoms are rearranged into new configuration
What is electrical energy?
Energy that a system possesses by virtue of the separation of positive and negative electrical charges
What is mechanical energy?
Energy of organized motion in which many molecules move simultaneously in the same direction
What is heat?
Energy that matter possesses by virtue of the ceaseless, random motion of all the atoms and molecules of which it is composed
Define energy in terms of biology. What is it measured as?
- Capacity to increase order
- Ability to produce change
- Measured as the amount of work performed during a given change
What is bioenergetics?
Conversion of one form of energy to another in a biological system
What does the 2nd Law of Thermodynamics state about order and entropy?
- Without energy input, processes will always proceed toward a less ordered state
- Entropy (disorder) will always increase
How do biological systems maintain order?
Using energy to keep body in a highly ordered state
What does the 1st Law of Thermodynamics state?
Energy can be neither created or destroyed, only converted to another form of energy
What kind of energy can’t perform physiological work of any kind?
Heat
What happens when one high-grade form of energy is transformed to another?
Some energy is degraded to heat
What is Gibbs Free Energy? Equation?
Energy in a compound which can be released to do work
(delta)G = (delta)H - T(delta)S
What is enthalpy?
Potential energy w/in a molecule’s chemical bonds
What is entropy?
Energy unavailable b/c of randomness
What do all chemical rxns involve?
Energy changes
What are enzymes? How are they classified? Specificity? Function? Regulation?
- Proteins classified by the type of rxn they catalyze
- High specificity for their substrates
- Catalyze chemical reactions in living organisms
- Attempt to drive rxn toward equilibrium
- Highly regulated
What do enzymes affect in a rxn?
Rate
What are the factors affecting the rate of enzyme rxns?
- Substrate concentration
- Enzyme concentration
- Temp
- pH
What are isozymes?
A single enzyme that exists in multiple molecular forms, which catalyze the same rxn
What is the Law of Mass Action?
- Simple chemical rxns and those catalyzed by equilibrium enzymes proceed linearly based on the concentrations of products and and reactants
- Rxn will proceed to the right or left depending upon the relative concentrations of the products and reactants
Why are enzymes important in biological systems?
Metabolic rxns would occur at such a slow rate that you couldn’t sustain life
How do enzymes alter the rate of a rxn?
- Allow for equilibrium rxns –> rxn can flux in both directions using same enzyme
- Can regulate enzymes to control which metabolic pathways are on/off
- Enzymes bring substrates in close proximity of each other –> lower activation energy needed to proceed w/ rxn –> faster velocity of rxn
What are the characteristics of enzyme rxns?
- Irreversible rxn
- Large energy change
- Nonequilibrium rxn
- Less common than S P
- Often rate limiting step
What are the characteristics of S P enzyme rxns?
- Reversible rxn
- Small energy change
- Equilibrium rxn
- Product also a substrate for the reverse rxn
- More common than S —> P
Endergonic vs. Exergonic chemical rxns
ENDERGONIC: -energy must be added to system to make these rxns happen (+ delta G) -won't occur w/o added energy -anabolic rxns EXERGONIC: -energy released (- delta G) -can occur spontaneously -catabolic rxns
What are coupled rxns?
Endergonic & exergonic rxns are coupled together
What is oxidation?
Loss of e- & H+ associated w/ it
What is reduction?
Gain of e- & H+ associated w/ it
What makes reduced compounds better than oxidized compounds?
- At a higher energy state since they carry more electrons
- Can eventually pass their electrons down the electron transport system to form ATP
What is metabolism?
- The sum of all chemical rxns occurring in a living organism
- All the rxns that create and use ATP
Which metabolic pathways are generally catabolic? Anabolic?
- Catabolic = pathways that generate ATP
- Anabolic = pathways that use ATP
What are the 3 primary macronutrients that are sources of energy?
- Carbohydrates
- Lipids
- Proteins
What are the basic building blocks of bioenergetics?
C, H, O, N
What are the functions of bioenergetics in the body?
- Biologic fuel
- Biologic structures
- Physiological processes
What is anaplerosis?
LOOKUP
Describe the energy release from the catabolism of fat.
Triglycerides fatty acides & glycerol (can undergo glycolysis) –> beta oxidation acytyl coenzyme A –> krebs cycle –> electron transport & oxidative phosphorylation
Describe the energy release from the catabolism of carbohydrates.
Polysaccharides –> glucose glycolysis pyruvic acid acetyl coenzyme A –> krebs cycle –> electron transport & oxidative phosphorylation
What is direct calorimetry? How is it done?
- Direct measurement of heat production
- Foodstuffs are ignited and burned in oxygen under pressure
- Heat of combustion of particular foods can be determined
What is heat of combustion? What does it represent?
- The heat liberated by oxidizing a specific food
- Represents the food’s total energy value
What is the heat of combustion for 1 g of carbohydrates? Lipids? Proteins?
- Carbs = 4.2 kcal
- Lipids = 9.4 kcal
- Protein = 5.65 kcal
What are the 3 main identifying parameters of exercise?
- Type
- Intensity
- Duration
List the types of exercise and whether they’re aerobic or anaerobic.
- Endurance = aerobic
- Resistance = anaerobic
- Spring = anaerobic
- Interval training = combo of both
What is endurance exercise?
Prolonged continuous or intermittent periods of contractile activity against low resistance
What is resistance exercise?
Short periods of contractile activity against high resistance
What is a sprint type of exercise?
Short periods of maximal contractile activity against low resistance
What is interval training?
Combo of diff types of exercise w/ rest in between intervals
How does the percentage of VO2 max relate to the intensity of exercise?
- Up to 49% = light
- 50-74% = moderate
- > 75% = heavy
What are the 5 means of metabolic control in exercise?
- Allosteric regulation
- Covalent modification
- Changing substrate concentration
- Changing enzyme concentration
- Nervous & hormonal control
What is the committed step of a rxn? What is a common inhibitor of this?
- Common control point in a metabolic pathway when the enzyme catalyzes the first irreversible rxn
- Inhibitor = product of the pathway can come back and regulate enzyme catalyzing committed step
Effects of allosteric activators vs. inhibitors on enzyme kinetics
ACTIVATORS -shift curve to left -lower Km -Higher affinity for enzyme -Increased velocity of rxn -takes lower substrate concentration to get same velocity as w/ no effectors INHIBITORS -shift curve to right -higher Km -lower affinity for enzyme -slower velocity of rxn -takes higher substrate concentration to get same velocity as w/ no effectors
What is allosteric modification?
Physically changing enzyme’s affinity for substrate to affect velocity of rxn
What is covalent modification?
Activity of certain enzymes is controlled by the reversible addition of chemical groups to their molecules
What is the most common way to modify the activity of enzymes and receptors? What is this an example of?
- Covalent modification
- Attach a phosphate group to the hydroxyl part of the side chains of amino acids serine, threonine and tyrosine
What is enzyme modulation by a cofactor?
Cofactors or coenzymes activate enzymes often by leading to a change in configuration which exposes the substrate binding site
What is a cofactor?
An organic or inorganic substance that is essential for the enzyme to function
What is a coenzyme?
Soluble, organic molecule which promiscuously associates and disassociates w/ the various enzymes it partners
What is the effect of temp and pH on enzyme activity? What happens at extremes?
- Enzymes have optimal temp & pH levels
- Too high/low temp = lowered activity
- Too high/low pH = denaturation
How does changing substrate concentration control metabolism?
Increase of substrate on one side of rxn increases rate in direction opposite to high concentration & decreases rate in its own direction
What is intracellular substrate concentration controlled by?
Concentration gradients and membrane transport proteins
What is the difference between allosteric modifiers and cofactors?
- Allosteric modifiers = not needed for rxn to occur
- Cofactors = needed for enzymes to function & rxn to occur
Active vs. Passive transport
- Active = requires energy & carrier protein to transport molecules across gradient
- Passive = large or charged molecules need channels, transporters; no energy required
What are the 3 mitochondrial transporters? How many things do they transport? What direction do they move?
- Uniport = transports one substrate down concentration gradient
- Symport = transports 2 substrates in same direction
- Antiport = transports 2 substrates in opposite directions
How can the body increase the Vmax of a rxn?
Increase concentration of enzyme
How is changing the enzyme concentration achieved? How fast is it?
- Slow process
- Often achieved through changes in rate of gene transcription
What are the major systems regulated during exercise?
- Metabolism
- Cardiovascular functionj
What does the metabolism do during exercise?
- Mobilize fuel for energy production
- Increase rate at which fuel is broken down to produce ATP
What are the cardiovascular functions during exercise?
- Transport fuel, oxygen & waste
- Maintain fluid and electrolyte balance
- Maintain thermal balance
What is the neurotransmitter released by the SNS? Name an endocrine gland that also releases this compound.
- Norepinephrine/epinephrine
- Adrenal medulla
What does norepinephrine mainly bind?
Alpha adrenergic receptors
What does epinephrine mainly bind?
Both alpha and beta adrenergic receptors
What is the intracellular mediator of alpha adrenergic receptors? What is their effect?
- Cyclic AMP & calcium
- Vasoconstriction
- Intestinal relaxation
What is the intracellular mediator of B1 adrenergic receptors? What is their effect?
- Cyclic AMP
- Increased HR
- Increased cardiac contraction
- Increased lipolysis
- Increased glycogenolysis
What is the intracellular mediator of B2 adrenergic receptors? What is their effect?
- Cyclic AMP
- Vasodilation
- Brachiodilation
What is the function of the endocrine system?
- Glands secrete hormones into the blood
- Hormones act as chemical systems throughout the body
How do most steroid hormones alter cell function?
- Gene activation
- Diffuse across membrane –> bind to intracellular receptors –> effect specific target cell
How do non-steroidal hormones alter cell function? Ex)
- Activate second messengers in cytoplasm
- Ex) insulin, glucagon, epinephrine, norepinephrine
What is the difference in composition between steroids and non steroids
Steroids are lipid soluble
What are the functions of insulin and glucagon?
- Insulin = decreases blood glucose levels
- Glucagon = increases blood glucose levels
How does insulin and glucagon maintain blood glucose levels?
- Pancreas secretes insulin when blood glucose is high
- Insulin stimulates formation of glycogen from glucose & promotes movement of glucose into certain cells
- Blood glucose decreases, which inhibits insulin secretion
- Pancreas secretes glucagon when blood glucose is low
- Stimulates change of glycogen into glucose & conversion of noncarbohydrates into glucose
- Blood glucose increase
