Chapter 22: Metabolic Adaptations, Energy Balance, and Temperature Regulation

BIOS 213

Carb energy content:

4 kcal/g

Protein energy content:

4 kcal/g

Fat energy content:

9 kcal/g

alcohol energy content:

7 kcal/g

1 kilocalorie =

1,000 calories

1 calorie =

the amount of energy needed to raise 1 cubic cm water 1 degree C

Brain’s preferred energy source:

glucose

Skeletal muscle (at rest) preferred energy source:

fatty acids

Various other organs can use ___ of energy

all the above

metabolic rate -

measured by amount of heat generated or amount of O₂ consumed per minute

Basal Metabolic Rate - 

measurement of the metabolic rate in quiet, resting, fasting condition

Average Basal Metabolic Rate in adults:

1200-1800 kcal/day

Factors that affect basal metabolic rate:

hormones, exercise, nervous system, body temperature, ingestion of food, age, gender, climate, sleep, malnutrition

Hormones that affect MR:

T₃ and T₄, testosterone, insulin, growth hormone

T₃ and T₄ are ____

major regulators of BMR

when thyroid hormone increases, caloric intake ___

increases

strenuous exercise increases MR rate ____

15x the basal rate

During exercise, the sympathetic nervous system is stimulated, and postganglionic neurons release:

norepinephrine and epinephrine

increases in norepinephrine and epinephrine cause:

increase in MR

An increase of 1^oC ___ rate of reactions by 10%

increases

food-induced thermogenesis -

cost of digesting, absorbing, and storing nutrients

absorptive state -

ingested nutrients enter the blood stream from GI tract to provide energy for the body

Postabsorptive state -

the GI tract lacks nutrients, and energy for the body; is supplied by the breakdown of the body’s own nutrient stores

Absorptive state reactions:

catabolism of glucose, catabolism of amino acids, protein synthesis, catabolism of few dietary lipids, glycogenesis, lipogenesis, transport of triglycerides from liver to adipose tissue

glycogenesis -

The synthesis of glycogen from glucose molecules, which primarily occurs in the liver and skeletal muscles when glucose is abundant

glycogenolysis -

The breakdown of stored glycogen into glucose molecules

gluconeogenesis -

The creation of glucose from non-carbohydrate substrates like lactate, glycerol, and certain amino acids

Catabolism of glucose:

most cells produce a majority of their ATP through glycolysis, via cellular respiration

Catabolism of amino acids:

some amino acids enter hepatocytes, where they are deaminated into keto acids. The keto acids either enter the Kreb’s Cycle for ATP production, or they are used to synthesize glucose or fatty acids

Protein synthesis:

many amino acids enter body cells (muscle or hepatocytes) for synthesis of proteins

Catabolism of few dietary lipids:

only a small portion of dietary lipids are catabolized for ATP; most are stored in adipose tissue

Lipogenesis:

liver converts excess glucose or amino acids into triglycerides to store; adipocytes also take up excess glucose to convert to triglycerides

____ of glucose is converted to triglycerides

40%

Transport of triglycerides from liver to adipose tissue:

most triglycerides are packaged into VLDLs and carried to adipose tissue for storage

____ primarily promotes absorptive state reactions

Insulin

Soon after a meal, insulin release is stimulated by:

glucose-dependent insulinotropic peptide from the small intestine, as well as increased glucose and certain amino acids

glucose is transported into cells by:

facilitated diffusion via GLUT

GLUT 4 =

muscle cells and adipocytes

GLUT 2 =

hepatocytes

GLUT 3 =

neurons

Postabsorptive state reactions:

glycogenolysis in the liver, glycogenolysis in muscle, lipolysis, protein catabolism, gluconeogenesis, catabolism of fatty acids, catabolism of lactic acid, catabolism of amino acids, catabolism of ketone bodies

glycogenolysis in the liver:

breakdown of glycogen to glucose in the liver, that releases glucose into blood (4 hour supply) → glucose 6-phosphate

glycogenolysis in muscle:

breakdown of glycogen to glucose in muscle, which provides ATP for muscle contraction

lipolysis:

triglycerides are broken down into fatty acids and glycerol, which are released into the blood; glycerol is taken up by the liver and converted into glucose, which then is released into the blood stream

protein catabolism:

breakdown of proteins releases amino acids, which are then converted to glucose

gluconeogenesis:

new glucose is formed from lactic acid, glycerol, or amino acids

the principle function of the postabsorptive state is to:

maintain a normal blood glucose level

catabolism of fatty acids:

fatty acids cannot be used for glucose production (acetyl CoA can’t be readily converted to pyruvic acid) → fatty acids get fed into the Kreb’s Cycle as acetyl CoA and produce ATP

catabolism of lactic acid:

cardiac muscle uses lactic acid to make ATP

Catabolism of amino acids:

hepatocytes can use amino acids directly to make ATP via deamination

catabolism of ketone bodies:

hepatocytes convert fatty acids to ketone bodies which can be used to make ATP → ketogenesis

Ketone bodies such as: Acetoacetic acid, beta-hydroxybutyric acid, and acetone all:

increase acetyl CoA breakdown

The postabsorptive state is regulated by:

hormones and sympathetic nervous system (ANS)

Hormones that regulate postabsorptive state:

anti-insulin hormones: glucagon, epinephrine, norepinephrine, cortisol

Decreased blood glucose stimulates:

release of glucagon, activation of sympathetic neurons

stress stimulates the release of:

cortisol

cortisol promotes:

gluconeogenesis, lipolysis, and protein catabolism

fasting -

going without food for hours or days

starvation -

weeks or months of food deprivation or inadequate food intake

anabolism -

synthesis of larger molecules from smaller molecules, requires energy

catabolism -

breakdown of larger molecules into smaller molecules, releasing energy

Insulin and thyroid hormones are:

anabolic hormones

Insulin and thyroid hormones stimulate:

all of the above

Glucagon, cortisol and growth hormone are:

catabolic homrones

Glucagon, cortisol and growth hormone stimulate:

all the above

conduction -

Heat exchange between materials that are in

direct contact with each other

Convection -

Transfer of heat by the movement of air or water

between areas of different temperatures

Radiation - 

Transfer of heat in the form of infrared rays

between a warmer object and a cooler one

without physical contact

Evaporation - 

Conversion of a liquid to a vapor

Hypothalamus regulates:

satiety

Neuropeptide Y stimulates:

food intake

Ghrelin:

increases appetite

melanocortin peptide inhibits:

food intake

leptin regulates:

amount of adipose tissue

leptin inhibits:

hypothalamic pathways that increase eating

leptin stimulates:

pathways that increase energy expenditure