Energy And Metabolism II Flashcards
Characteristics of phosphocreatine.
- has a high energy phosphate bond
- is 3-8x more abundant than ATP
- cannot participate directly in energy transfer
- can transfer energy interchangeably with ATP
Why are essential aa considered essential?
-cannot be synthesized in the body or are not synthesized easily or in large quantities
What does non-essential aa formation depend on?
-alpha keto acid precursors
Review synthesis of alanine from pyruvic acid
:)
What is considered the most intracellular process that requires energy? How much energy is required?
- formation of peptide linkages
- 500-5000 calories per mole
Outline how peptide bonds are made.
- aa + ATP -> aa-AMP + 2P
- aa-AMP + tRNA -> aa-tRNA +AMP
- attachment of tRNA to mRNA via codon-anticodon pairing
- formation of peptide bond with second aa using peptidyl transferase + GTP
How many phosphate bonds are needed to form one peptide linkage?
4
What happens to excess aa in the body?
-degraded and used for energy
Outline the steps of protein degradation.
- deamination (involves transamination and end product is ammonia)
- two molecules + one molecule of CO2 are combined in the liver to form urea
- this occurs in the urea/ornithine cycle
Who discovered the ornithine/urea cycle?
Kreb’s 5 years before he discovered the TCA cycle
Where does the ornithine cycle take place?
-mitochondria and cytoplasm
Outline the steps that take place in the mitochondria. ornithine cycle
- ammonia +CO2 -> carbamoyl phosphate
- carbamoyl phosphate + ornithine -> citrulline
Outline the steps that take place in the cytoplasm. (Ornithine cycle)
- citrulline + Asp -> argininosuccinate
- argininosuccinate -> Arg + fumarate
- Arg -> urea + ornithine
- fumarate can enter the TCA cycle
Rate of overall chemical reaction is determined by what?
- [enzyme]
- [substrate]
What happens when substrate concentration is high?
- rxn rate is determined almost entirely by conc of enzyme
- ex. Diabetes mellitus and glucose
What happens when the enzyme concentration is high?
- rxn rate becomes directly proportional to conc of substrate and enzyme
- ex. Absorption of substances from intestinal tract and renal tubules when concs of the substrate are low compared to transport enzymes
Most chemical reactions in the body occur in series, what is the overall rate of rxn determined by?
-slowest step in the series
+rate limiting step
+ADP is the major rate limiting factor for almost all energy metabolism in the body
About ______ of energy in foods becomes heat during ATP formation.
35%
-more heat is produced in the transfer of energy from ATP to the functional systems of cells
No more than _____ of energy from food is used by the functional systems. What is most of this converted to?
27%
-converted into heat, exception is energy transferred outside the body as potential energy (eventually will turn into heat)
What are some factors that influence metabolic rate?
- arousal vs sleeping
- skeletal muscle
- age
- thyroid activity
- testosterone
- growth hormone
- fever
- sleep
- malnutrition
____ of energy expended by body is derived from oxidative phosphorylation involving differnt kinds of food.
95%
What can whole body metabolic rate be calculated from?
-rate of oxygen utilization
-metabolize 1 liter of oxygen with:
+glucose: 5.01 Cal
+fat: 4.7 Cal
+protein: 4.6 Cal
Energy liberate per liter of oxygen with average diet averages about 4.825 Cal
Energy equivalent of oxygen
BMR normally averages _______ Cal per hour
65-70
How does thyroxine affect BMR?
- thyroxine increases rate of chemical reactions in cells and increases metabolic rate
- maximal secretion may increase metabolic rate 50-100% above normal
- loss of thyroid secretion decreases metabolic rate to 40-60% of normal
How does testosterone affect BMR?
- testosterone can increase metabolic rate 10-15%
- mainly related to anabolic effect of increase in skeletal muscle mass
How does malnutrition affect BMR?
- 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
What, on average, are there components of energy expenditure? What activities?
- BMR (60% daily energy usage)
- thermic effect of food (8%)
- no exercise activity (7%)
- purposeful physical activity (25%)
Skeletal muscle accounts for ____ to _____ percent of BMR even at rest, BMR is typically corrected for differences in body size.
20-30%
What accounts for increasing decline in BMR with increasing age?
-related to loss of muscle mass and replacement with adipose tissue with a lower rate of metabolism
Phosphocreatine functions as what?
-an accessory storage depot for energy and as an ATP buffer
