Lecture 15 - Energy Balance and Metabolism II

Question 1

ATP is generated by the combustion of:

Answer 1

•Carbohydrates •Fatty acids •Proteins

Question 2

ATP energizes:

Answer 2

• Synthesis of cellular components
• Muscle contraction
• Active transport across membranes
• Glandular secretion
• Nerve conduction

Question 3

Phosphocreatine functions as

Answer 3

an accessory storage depot for energy and as an “ATP Buffer.”

Question 4

Phosphocreatine

Answer 4

• 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

Question 5

Links in Protein Molecules

Answer 5

Peptide Linkages

Linkages btwn Peptide chains

Question 6

Essential amino acids

Answer 6

cannot be synthesized in the body or are not synthesized easily or in quantities

Question 7

Non-essential amino acids

Answer 7

formation depends on α-keto acid precursors

Question 8

Equilibrium among tissue proteins, plasma proteins, and plasma AAs is ___.

Answer 8

reversible

Question 9

Transamination

Answer 9

Synthesis of alanine from pyruvic acid (example of nonessential AA)

Question 10

Formation of peptide linkages

Answer 10

• 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

Question 11

Degradation of Proteins for Energy

Answer 11

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.

Question 12

Deamination results in

Answer 12

release of energy and ammonia

Question 13

Ornithine (Urea) Cycle

Answer 13

Discovered by Krebs

Urea formation in liver

Question 14

Rate of overall chemical reaction is determined by:

Answer 14

• Concentration of the enzyme

* Concentration of the substrate

Question 15

When substrate concentration is high, the reaction rate…

Answer 15

Reaction rate is determined almost entirely by concentration of enzyme

Example: Diabetes mellitus and glucose

Question 16

When enzyme concentration is high, the reaction rate…

Answer 16

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.

Question 17

Most chemical reactions in the body occur in ___.

Overall rate of a series of chemical reactions is determined by _______.

Answer 17

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.

Question 18

___ is the major rate-limiting factor for almost all energy metabolism in the body

Answer 18

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.

Question 19

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 ____.

Answer 19

35%, 27%

heat

Exception: energy transferred outside the body as potential energy (But eventually that will also become heat).

Question 20

Factors that Influence Metabolic Rate

Answer 20

Arousal vs sleeping, Skeletal muscle, Age, Thyroid activity, Testosterone, Growth hormone, Fever, Sleep, Malnutrition

Question 21

___ is one of the best known stimuli for increasing the rate of thyroid stimulating hormone.

Answer 21

Cold

Question 22

Factors Affecting BMR

Answer 22

Thyroxine and Basal Metabolic Rate, Testosterone and Basal Metabolic Rate, Malnutrition and Basal Metabolic Rate

Question 23

Basal Metabolic Rate

Answer 23

• 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

Question 24

Metabolize 1 liter of oxygen with:

Answer 24

• Glucose = 5.01 Cal
• Fat = 4.7 Cal
• Protein = 4.6 Cal

Question 25

Thyroxine and Basal Metabolic Rate:

Answer 25

* 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.

Question 26

Testosterone and Basal Metabolic Rate:

Answer 26

* Testosterone can increase metabolic rate 10 to 15 percent. * Mainly related to anabolic effect of increase in skeletal muscle mass.

Question 27

Malnutrition and Basal Metabolic Rate:

Answer 27

* 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.

Question 28

Much of decline in BMR with increasing age is probably related to ...

Answer 28

loss of muscle mass and replacement with adipose tissue with a lower rate of metabolism.

Question 29

Because skeletal muscle accounts for 20 to 30 percent of BMR even at rest, BMR is typically corrected for ___.

Answer 29

differences in size

Question 30

Do females or males have a generally higher metabolic rate?

Answer 30

males

Question 31

As age increases, BMR tends to...

Answer 31

decrease