PNB Spring Lab Quiz Prep - Metabolism

What is metabolism?

balancer between energy input and energy expenditure

What nutrients are absorbed during metabolism?

carbs, lipids (fats), proteins

What is the goal of metabolism?

maintain energy homeostasis

What is the majority of energy used for?

basal metabolic rate

What is basal metabolic rate (BMR)?

energy required for basic life functions at rest

What is the sodium-potassium pump (Na⁺/K⁺ ATPase)?

maintains resting membrane potential

What does the sodium-potassium pump constantly use?

ATP; high energy demands

What is the byproduct of metabolism?

heat

What is the function of heat during metabolism?

maintains thermal homeostasis (body temperature)

What does energy expenditure (output) come from?

metabolic rate, physical activity, thermoregulation

What is the energy output of metabolic rate?

30-60%

What is the energy output of physical activity?

10-60%

What is the energy output of thermoregulation?

approx. 10%

What is normal skeletal muscle energy use?

moderate energy consumption

When is skeletal muscle energy use high?

during intense exercise

What are anabolic pathways?

build and store macromolecules

What are the kinds of anabolic pathways?

protein synthesis, glycogen formation, require energy (ATP)

What are catabolic (metabolic) pathways?

breakdonw/consume macromolecules

What are the kind of catabolic (metabolic) pathways?

breakdown of carbs, fats, proteins

What is the purpose of catabolic (metabolic) pathways?

release energy

How is metabolism controlled?

involuntary

Why is metabolism involuntary?

ATP production and consumption cannot be directly controlled

What is a controllable factor in energy expenditure?

activity level (more activity = higher energy expenditure)

What is the control of energy intake?

voluntary; energy consumption is controlled

What determines control of energy intake?

what and how much we eat

What is hunger?

desire to eat

What is satiety?

no desire to eat (feeling full)

What orchestrates hunder and satiety?

gut-brain axis

What key structure is involved in the regulation of hunger and satiety?

hypothalamus

What regulates hunger and satiety?

hormonal signaling

What is the control of hunger and satiety signals?

involuntary

What hunger signals does the body automatically regualte?

when one is feeling hungry of full

What does the arcuate nucleus (hypothalamus) contain?

orexigenic and anorexigenic neurons

What are orexigenic neurons?

stimualte appetite

What are anorexigenic neurons?

suppress appetite

What regulates the control of arcuate neurons?

gut signals

What are key signals that control arcuate neurons?

CCK (cholecystokinin), vasoactive intestinal peptide (VIP), insulin

What does the activation of anorexigineic neurons stimulate?

paraventricular nucelus (PVN) of hypothalamus

What is the result of stimualting the paraventricular nucleus (PVN) of hypothalamus?

feelings of satiety (fullness)

When are satiety signals lost?

no gut signaling is present

What is the effect of losing satiety signals?

anorexigenic neurons do not fire

What is the result of anroexigenic neurons not firing?

reduced satiety; increased hunger

What does the afferent vagus nerve stimualte?

signals satiety to the brain

What triggers afferent vagus nerve stimualtion?

gut distension (stretching after eating)

Where do anorexic hormones/peptides come from?

GI organs and adipose tissue

What are GI organ anorexic hormones/peptides?

insulin, CCK, VIP (control orexogenic and anorexogenic neurons)

What are adipose tissue appetite-supresing signals?

leptin

What is leptin?

shuts off orexic pathways in hypothalmus; decreases appetite

What are brain targets of satiety signals?

arcuate nucleus, then paraventricular nucleus (PVN)

What do orexigenic neurons respond to?

gut-derived signals (ghrelin)

What is ghrelin?

hunger hormone (strong hunger signal)

What is the source that secretes ghrelin?

stomach

When is ghrelin released?

in response to empty stomach

What does a growling stomach indicate?

ghrelin release

What does stress increase?

Neuropeptide Y (NPY) in the brain (explains stress eating)

What is the effect of neuropeptide Y (NPY) in the brain?

increased appetitie

What hypothalamic hormone stimulates appetite?

orexin (hypocretin)

What is orexin (hypocretin)?

increases food-seeking behaviro

What GI hormone stimulates appetite?

ghrelin (stomach)

What is the result of ghrelin interactions?

suppresses leptin

What results from suppresing leptin?

decreases satiety

What does the stimulation of NPY result in?

increased food intake

What is the relationship between hunger and satiety?

inverse

Why do hunger and satiety have an inverse relationship?

orexigenic and anorexigenic neurons act on same hypothalamic regions

What has opposing effects?

orexigenic and anorexigenc neurons

What is metabolism adjustment based on?

age, environment, nutritional state

What is the lipostatic theory?

signals from fat (adipose) tissue modulate eating behavior in order to maintain a particular weight

What is the goal of the lipostatic theory?

maintain body weight

What is the key idea behind the lipstastic thoery?

more fat results in metabolic adjustments

What secretes leptin?

adipocytes (fat cells)

What is the function of leptin?

inhibits orexigenic neurons

What does leptin promote?

satiety

What is the result of increased eating in the leptin negative feedback loop?

increased fat; increased leptin

What is the result of increased leptin in the leptin negative feedback loop?

increased appeitie

What is the leptin negative feedback loop?

supports lipostatic theory

Who does the leptin negative feedback loop work on?

leptin-deficient individuals

What does the leptin negative feedback loop not work well in?

most obese individuals

Why does the leptin negative feedback loop not work on obese individuals?

leptin resistance (desensitization)

What is the glucostastic theory?

regualting metabolism through blood glucose levels (negative feedback system)

What is the goal of the glucostatic theory?

maintains glucose homeostasis

What is fed metabolism?

absorptive state

What is the result of the fed absorptive state?

hyperglycemia; high level of glucose inside the blood

What does the fed absorptive state create?

activates anabolic storage; increased synthesis

What is fasted metabolism?

post-absorptive state

What is the result of the fasted post-absorptive state?

hypoglycemia

What does the fasted post-absorptive state create?

increased catabolism; elevate the level of glucose in the blood

What is gluconeogensis?

making glucose from non-carbohydrates

What are sources for gluconeogenesis?

proteins and fats

What are energy storage molecules?

glycogen (carbs) and triglycerides (fats)

What is a short term energy storage molecule?

glycogen (carbs)

What is a long term energy storage molecule?

triglycerides (fats)

Where is glycogen stored?

liver and skeletal muscle

What are features of glycogen?

highly branched polymer of glucose, quick & easy access

What are the components of triglycerides?

glycerol + 3 fatty acids

What are features of triglycerides?

high energy yield, slow to access, stored efficiently

What is glycogenesis?

formation of glycogen; can be formed from excess glucose

What is glycogen phosphorylase?

phosphorylates glycogen forming glucose-1-phosphate (becomes G-6-Phosphate)

What is glucose-6-phosphatase?

dephosphorylates G-6-P, forming glucose

Where is glucose-6-phosphatase found?

liver

What does the liver release?

glucose to blood