Ch. 19 Energy Balance/Metabolism (Day 1) Flashcards
(49 cards)
What is energy?
Capacity to do work
Types:
–chemical, transport, mechanical
What are the 2 major users of energy that our cells have?
Maintain ion gradients
–e.g. Na+/K+ pump
Maintenance (e.g. turnover) and repair
–e.g. protein synthesis
What are all the users of energy that our cells have?
Maintain ion gradients
–e.g. Na+/K+ pump
Maintenance (e.g. turnover) and repair
–e.g. protein synthesis
Movement (muscle contraction)
Reproduction
Lactation
Thermogenesis
What is metabolism?
Overall energy economy in a cell or organism
What is metabolic rate (MR)?
Sum total of all energy-obtaining and energy-consuming processes
Catabolism
Breakdown of macromolecules (fuels) to obtain usable energy –> ATP
big molecules –> small molecules + ATP
Anabolism
Use of energy (ATP) to produce new macromolecules
small molecules + ATP –> big molecules
Energy balance
Energy stored + energy intake minus energy expenditure
Energy expenditure: work + heat
Energy balance is a ____ ____ in which energy demand is balanced with energy supply.
Steady state
The turnover rate of the ATP cycle is equivalent to ____ ____.
Metabolic Rate
Flux through ATP demand pathways is ____ by flux through ATP supply pathways.
balanced
Catabolism in Anaerobic Organisms…
final common pathway whereby the chemical energy in fuel molecules is conserved as ATP is called RESPIRATION
Respiration is a process of slow, controlled ____, and we gain energy at various stages along the way.
Combustion (oxidation)
All the macronutrients feed into a final, common pathway in ____. (Catabolism or Anabolism)?
Catabolism
____ is the basic metabolic fuel.
Glucose
The TCA Cycle is the rotary engine of ____.
Metabolism
Energy content of food
Direct calorimetry
1 Calorie = 1,000 calories = 1 kcal = 4.184 kJ
Amount of heat needed to raise temperature of 1 liter of water by 1ºC = 1 Calorie
Yields “gross” energy of food
Includes combustion of indigestible components
–e.g. fiber, so energy content of some foods wasn’t accurate
Gross Energy Content
Adjusted for indigestible components and for any other relevant losses, then this modified value is used on food labels
W.O. Atwater, USDA (1900)
obtained gross energy values from various foods, applied corrections for digestibility, energy losses in urine; published series of tables of foodstuff energy contents
Several variations on Atwater’s general system, but his basic approach remains basis for current food labeling policies, despite some significant problems
What are the energy contents of the following metabolic fuels: CHO, PRO, and fat?
CHO: 4kcal (16.7kJ)/g
PRO: 4kcal (16.7kJ)/g
Fat: 9kcal (37.7kJ)/g
Under normal, well-fed conditions, protein is NOT used for energy, but is preferentially used for ____ ____.
Protein synthesis.
However, this can change under certain conditions, e.g. fasting, starvation, prolonged exercise
Energy Expenditure: Indirect Calorimetry
Since combustion (oxidation) of fuels to provide energy, and the use of that derived energy requires OXYGEN, then the rate of OXYGEN CONSUMPTION can be used to measure metabolic rate
1 liter O2 consumed per 4.5-5.0 kcal released from metabolized food
Metabolic rate (kcal/day) = liter O2 consumed/day * 4.8 kcal/L O2
Basal Metabolic Rate (BMR)
Minimal rate for maintaining life, aka SMR (12 hours post absorptive state, resting)
What influences metabolic rate?
Age: as age increases, MR decreases
Sex: female MR = 0.9 * male MR
Lean muscle mass (LMM): as LMM increases, MR increases
Activity level: as physical activity increases, MR increases
Diet: eating meal increases MR via thermic effect of food (aka “heat increment, HI”) - heat loss due to processes of uptake/assimilation/processing of nutrients - varies w/ nutrient - protein has highest HI
Hormones: thyroid hormones, epinephrine, norepinephrine
Genetic factors: poorly characterized
