L-7 Energy Balance and Metabolism II Flashcards
how is ATP generated?
by the combustion of:
- carbs
- fatty acids
- proteins
what does ATP energize?
- synthesis of cellular components
- muscle contraction
- active transport across membranes
- glandular secretion
- nerve conduction
what does phosphocreatine function as?
- an accessory storage depot for energy
- ATP buffer
describe phosphocreatine
- has a high energy phosphate bond (13,000 cal)
- is 3-8 times more abundant than ATP
- cannot participate directly in energy transfer
- can transfer energy interchangeably with ATP
what do non-essential amino acid formation depend on?
alpha-keto acid precursors
what amino acid is present in the body in large quantities?
glutamine; serves as an amino radical storehouse
what are aminotransferases derivatives of?
pyridoxine (vitamin B6)
describe protein synthesis in regards to energy consumption
- one of the most energy expensive processes
- different peptide linkages require anywhere from 500 to 5000 calories per mole
how many phosphate bonds are needed to form one peptide linkage?
4
- each peptide bond only stores 500-5000 calories
what happens to excess amino acids in the body?
they are degraded and used for energy
what is one of the end products of deamination?
ammonia
what helps form urea? where?
in the liver; two molecules of ammonia + one molecule of CO2 are combined; this is the urea (ornithine) cycle
where in the liver cells does the ornithine cycle occur?
in mitochondria and in cytoplasm
describe process in mito
ammonia + CO2 –> carbamoyl phosphate
carbamoyl phosphate + ornithine –> citrulline
describe process in cytoplasm
citrulline + aspartate –> argininosuccinate
argininosuccinate –> arginine + fumarate
arginine –> urea + ornithine
*fumarate can enter CAC
what is the rate of the overall chemical reaction determined by?
- concentration of enzyme
- concentration of substrate
in regards to reaction rate, what happens when substrate concentration is high
- reaction rate is determined almost entirely by concentration of enzyme
give an example
diabetes mellitus and glucose:
- large quantities of glucose enter renal tubules
- glucose is in great excess in the tubules
- transport enzymes become saturated
- further incr in gluc concen in tubules have little effect on gluc reabsorption
- glucose reabs rate is limited by concen of transport enzymes
what about when enzyme conc is high
- reaction rate becomes directly proportional to concentration of substrate enzyme
give an example
absorption of substances from intestinal tract and renal tubules when concentrations of the substrate are low compared to transport enzymes
EXAM: what is the major rate-limiting factor for almost all energy metabolism in the body?
ADP
elaborate
- cellular concentrations of ADP are low
- chemical reactions that depend on ADP as one of the substrates are very slow
- ATP is converted to ADP during cellular activity; thus, ADP concen incr during cell activity
- incr ADP = incr reaction rates
what are some examples of ADP substrate dependence
all oxidative metabolic pathways
other pathways for the release of energy
how much of the energy in foods becomes heat during ATP formation and how much of it is used by functional systems?
35% and 27%
what are factors that influence metabolic rate?
- arousal vs sleeping
- skeletal muscle
- age
- thyroid activity
- testosterone
- growth hormone
- fever
- sleep
- malnutrition
what is the best known stimuli for increasing the rate of thyroid stimulating hormone?
the cold
describe basal metabolic rate
95% of energy expended by body is dervied from oxidative phosphorylation involving different kinds of foods
how can whole-body metabolic rate be calculated ?
from rate of oxygen utilization
what do you metabolize 1 L of O2 with?
- glucose: 5.01 C
- fat: 4.7 Cal
- Protein: 4.6 Cal
how many Cal are liberated per liter of oxygen with average diet?
averages to about 4.825 Cal = energy equivalent of oxygen
give some averages and random numbers on basal metabolic rate
- avg 70kg man, inactive: 1650 Cal/day
- 70kg man, inactive, reasonable diet: 1850 Cal/day
- 70 man, sitting in chair, psychologically active, no exercise: 2000 Cal/day
- walking upstairs requires 17x the energy as sleeping in bed all day
what is the BMR average per hour?
65-70 Cal per hour
How is BMR measured?
TEXT
what are some factors affecting BMR?
- thyroxine and basal metabolic rate
- malnutrition and basal metabolic rate
- testosterone and basal metabolic rate
describe the thyroxine and basal metabolic rate
- thyroxine incr rate of chem reactions in cells and incr metabolic rate
- max secretion may incr metabolic rate 50 to 100 percent above average
- loss of thyroid secretion decr met rate to 40-60% of normal
describe malnutrition and basal metabolic rate
- malnutrition results in reduced food substances in the cells
- this results in a marked reduction in metabolic rate
- this process may accompany final stages of many disease conditions
describe testosterone and basal metabolic rate
- T can incr met rate 10-15 %
- mainly related to anabolic effect of incr in skeletal muscle mass
what is the minimal level of energy required for a person to just exist?
60% - basal metabolic rate
what is much of the decline in BMR with increased age?
probably related to loss of muscle mass and replacement with adipose tissue with a lower rate of metabolism
