Overview of Metabolism

energy metabolism

the way the body stores and utilizes energy

what 4 things influence energy metabolism?

eating patterns, growth, stress, metabolic rate

2 critical concepts about energy metabolism?

1. The body has to store nutrients during intake periods & break down these stores between intake periods because food intake is intermittent

2. Blood glucose levels need to be maintained at all times because the brain depends on glucose as its main energy source

Where does energy input come from?

carbohydrates, fat, protein

What does energy output look like? (6 forms)

mechanical work, synthetic reactions, membrane transport, signal generation/conduction, heat production, detoxification & degradation

Body composition of humans by % body weight?

65% water & minerals, 20% fat, 14% protein (half is fixed, half is mobilizable), 0.6% carbohydrates

Composition of caloric stores? (%ages)

76% fat, 23% protein, 1% carbohydrates

3 important organ/tissue contributors?

liver, adipose tissue, muscle

glycogenesis

formation of glycogen from glucose

glycogenolysis

breakdown of glycogen to make glucose

gluconeogenesis

formation of glucose from other compounds like fatty acids or proteins

lipogenesis

formation of lipids from FFAs (free fatty acids)

lipolysis

breakdown of lipids to FFAs

protein synthesis

synthesis of proteins from amino acids

proteolysis

breakdown of protein to amino acids

absorptive/fed state

period immediately after eating when nutrients absorbed through intestinal wall into the circulatory & lymphatic systems (about 4 hours after each meal)

postabsorptive/fasting state

period after the absorptive state has finished where blood glucose levels are maintained by converting other molecules to glucose

4 important hormones?

insulin, glucagon, cortisol, epinephrine

1-2

only _____ % of pancreas is actually used for endocrine functions

3 actions of insulin?

lowers blood glucose, amino acids, FFAs

4 steps of mechanism of action for insulin?

insulin molecule binds to receptor in the cell membrane

activates insulin signal pathway

a vesicle containing the GLUT4 transporter is sent to the PM

once the vesicle is fused with the PM, glucose is transported inside the cell

glucagon major actions?

increase glycogenolysis, gluconeogenesis, lipolysis

cortex

80-90% of the adrenal gland is the ______

medulla

10-20% of the adrenal gland is the _______

cortisol regulation pathway?

stress, hypoglycemia, or morning time positively regulates the release of corticotropin releasing hormone (CRH) from the hypothalamus

nighttime negatively regulates the release of corticotropin

CRH from the hypothalamus causes the pituitary gland to release adrenocorticotropin hormone (ACTH)

ACTH stimulates the adrenal glands to produce cortisol

4 primary effects of cortisol?

mobilizing amino acids from protein in muscle

stimulating hepatic gluconeogenesis

facilitate lipolysis by epinephrine

anti-insulin effect on muscle & adipose tissue