Metabolism/Pathways intro Flashcards
(47 cards)
Concept of energy balance
Energy in = Energy Out
Weight gain
Energy in > Energy Out
weight loss
Energy in
components of Total energy expenditure (TEE)
Resting metabolic rate, Thermic effect of food, energy expended in physical activity
Resting metabolic rate
- about 75% TEE in sedentary ppl
- primary determinant = free fat mass (lean body mass)
measure resting metabolic rate
indirect calorimetry – device measures respiratory gas composition and flow rates to estimate O2 consumption/CO2 production
Why is oxygen used in indirect calorimetry
energy mostly from oxidation of nutrients (oxygen final electron acceptor in oxidation of nutrients, so rate of oxygen consumed = indirect measure of energy expenditure)
Estimate RMR
formula based on age, sex, height, weight, and lean body mass if known fo rmore accuracy
Thermic effect of food (TEF)
- normally about 8% of TEE
- energy cost of digestion/distributing nutrients from diet to body tissues
- protein has highest energy cost, then carbs then fat
Measure Thermic effect of food
- indirect calorimetry - determine increment of energy expenditure above RMR following ingestion of defined test meal
Energy costs of nutrients
Protein > Carbs > Fat
Energy expended in physical activity
- most variable component of energy expenditure
- 30-40% for those exercising regularly
non-exercise activity thermogenesis (NEAT)
refers to energy consumed in movement that is unplanned/unconscious; i.e. fidgeting or other random movements
efficiency
ratio of work to total energy expenditure during activity (total includes that lost as heat/lost to environment)
measure total energy expenditure
doubly labeled water – measures O2 consumption in free living individuals over weeks then subtract RER and TEF
Energy intake regulated by
brain makes decisions about eating (how much, how often)
- get signals from senses, organs, internal signals (blood nutrient levels/hormones)— all regulated in brain pathways
3 key nutrient molecules
glucose, fatty acids, amino acids
Stores of which nutrient has largest energy
- Fat (about 9 kcal/g) – large storage pool
- Carbs: 4 kcal/g – stored as glycogen in muscle and liver
- Protein: 4 kcal/g but no true storage
what happens to excess protein
oxidized to carbohydrate or fat
- if in protein balance, carbs preferentially oxidized and fat stored
why do we accumulate body fat
- smaller capacity to store excess carbohydrates, so they will be preferentially oxidized while fat is stored
- can also convert carbs into fat for more efficient storage
What happens in fasting
- glycogen broken down, protein in muscle –> amino acids to convert to glucose
- eventually lack essential amino acids, essential fatty acids and micronutrients and get organ dysfunction/disease
what happens in positive energy balance
- assimilate ingested nutrients and fill storage pools
- may remake polymers from monomers –> anabolic
Forms of energy currency in cell
ATP, NADPH, GTP/UTP, NADH/FADH2
catabolic vs anabolic processes
catabolic = breakdown of complex molecules into simpler ones
anabolic - building complex molecules from simpler ones