Lecture 15 - Energy Balance and Metabolism II Flashcards
ATP is generated by the combustion of:
•Carbohydrates •Fatty acids •Proteins
ATP energizes:
- Synthesis of cellular components
- Muscle contraction
- Active transport across membranes
- Glandular secretion
- Nerve conduction
Phosphocreatine functions as
an accessory storage depot for energy and as an “ATP Buffer.”
Phosphocreatine
- Has a high energy phosphate bond (13,000 cal)
- Is 3-8x more abundant than ATP
- Cannot participate directly in energy transfer
- Can transfer energy interchangeably with ATP
Links in Protein Molecules
Peptide Linkages
Linkages btwn Peptide chains
Essential amino acids
cannot be synthesized in the body or are not synthesized easily or in quantities
Non-essential amino acids
formation depends on α-keto acid precursors
Equilibrium among tissue proteins, plasma proteins, and plasma AAs is ___.
reversible
Transamination
Synthesis of alanine from pyruvic acid (example of nonessential AA)
Formation of peptide linkages
- among the most important intracellular processes that require energy
- require anywhere from 500 to 5000 calories per mole
- 4 high-energy phosphate bonds are needed to form one peptide linkage
Degradation of Proteins for Energy
Excess amino acids in the body fluids are degraded and used for energy.
•First step is deamination:
•Generally involves transamination.
•Refer to page 879.
•Note that one of the end products is ammonia.
•Two molecules of ammonia + one molecule of carbon dioxide are combined in the liver to form urea.
•This occurs in the urea (ornithine) cycle.
Deamination results in
release of energy and ammonia
Ornithine (Urea) Cycle
Discovered by Krebs
Urea formation in liver
Rate of overall chemical reaction is determined by:
- Concentration of the enzyme
* Concentration of the substrate
When substrate concentration is high, the reaction rate…
Reaction rate is determined almost entirely by concentration of enzyme
Example: Diabetes mellitus and glucose
When enzyme concentration is high, the reaction rate…
Reaction rate becomes directly proportional to concentration of substrate and enzyme
Example: absorption of substances from intestinal tract and renal tubules when concentrations of the substrate are low compared to transport enzymes.
Most chemical reactions in the body occur in ___.
Overall rate of a series of chemical reactions is determined by _______.
Series
the rate of reaction of the slowest step in the series
•Called the rate-limiting step in the entire series
•ADP is the major rate-limiting factor for almost all energy metabolism in the body.
___ is the major rate-limiting factor for almost all energy metabolism in the body
ADP
- Cellular concentrations of ADP are low
- Chemical reactions that depend on ADP as one of the substrates are very slow.
•Examples of ADP substrate dependence: •All oxidative metabolic pathways •Other pathways for the release of energy
- ATP is converted to ADP during cellular activity; therefore, ADP concentration increases during cellular activity.
- Increased concentration of ADP increases reaction rates.
About __% of energy in foods becomes heat during ATP formation.
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. Most of this % is finally converted to ____.
35%, 27%
heat
Exception: energy transferred outside the body as potential energy (But eventually that will also become heat).
Factors that Influence Metabolic Rate
Arousal vs sleeping, Skeletal muscle, Age, Thyroid activity, Testosterone, Growth hormone, Fever, Sleep, Malnutrition
___ is one of the best known stimuli for increasing the rate of thyroid stimulating hormone.
Cold
Factors Affecting BMR
Thyroxine and Basal Metabolic Rate, Testosterone and Basal Metabolic Rate, Malnutrition and Basal Metabolic Rate
Basal Metabolic Rate
- 95% of energy expended by body is derived from oxidative phosphorylation involving different kinds of foods.
- Therefore, whole-body metabolic rate can 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
Thyroxine and Basal Metabolic Rate:
- Thyroxine increases rate of chemical reactions in cells and increases metabolic rate.
- Maximal secretion may increase metabolic rate 50 to 100 percent above normal.
- Loss of thyroid secretion decreases metabolic rate to 40 to 60 percent of normal.
Testosterone and Basal Metabolic Rate:
- Testosterone can increase metabolic rate 10 to 15 percent.
- Mainly related to anabolic effect of increase in skeletal muscle mass.
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.
Much of decline in BMR with increasing age is probably related to …
loss of muscle mass and replacement with adipose tissue with a lower rate of metabolism.
Because skeletal muscle accounts for 20 to 30 percent of BMR even at rest, BMR is typically corrected for ___.
differences in size
Do females or males have a generally higher metabolic rate?
males
As age increases, BMR tends to…
decrease
