Metabolism Flashcards
Def of metabolism:
sum of all chemical reactions in the body
Metabolism can be…
- anabolic
- catabolic
Metabolism is used to…
- extract energy from nutrients
- use energy for work
- store excess energy
What is the basal metabolic rate (BMR)?
lowest rate of reactions needed to keep body going
How do you find the total body energy?
energy stored + energy intake - energy output
What is energy intake?
energy in nutrients that we absorb
What is energy output?
work + heat
Work is used to…
- transport molecules
- cause movement
- growth
- body maintenance
- store information
- store energy
Regulation of energy intake comes from…
- hunger
- satiety
What is the difference between hunger and satiety?
- hunger: desire for food in general
- satiety: desire for specific food
Where is hunger and satiety regulated?
hypothalamus
Two types of neurons in the hypothalamus that regulates appetite and energy expenditure:
- pro-opiomelanocortin neurons
- orexigenic neurons
Pro-opiomelanocortin neurons release…
alpha-MSH and CART (cocaine and amphetamine regulated transcript
Pro-opiomelanocortin neurons’ effect on hunger and satiety:
- decrease in food intake
- increase in energy expenditure
When are pro-opiomelanocortin neurons specifically activated?
- severe infections
- cancer
- uremia
- can also be activated the same way as orexigenic neurons
Orexigenic neurons release…
- neuropeptide Y (NPY)
- agouti-related protein (AGRP)
Orexigenic neurons effect on hunger and satiety:
- increases food intake
- reduces energy expenditure
What influences the activation of hunger and satiety centers?
- higher brain control
- endocrine regulation
- sensory feedback from GI
Examples of sensory feedback from GI that influences activation of hunger and satiety centers:
- stretch receptors for fullness and CCK, which increases with food
- insulin and PPY from GI and leptin from adipocytes, which decreases feeding when food is present
- ghrelin from oxyntic cells of empty stomach
- endocannabinoids made by the NS, which increases feeding behavior
Glucostatic theory of regulation:
feeding behavior results from glucose metabolism
- high blood glucose decreases hunger and increases satiety
The glucostatic theory of regulation is regulated by…
- insulin
- glucagon
Lipostatic theory of regulation:
- body fat stores will regulate weight
- leptin protein hormone helps regulate (made by adipocytes)
According to the lipostatic theory of regulation, an increase in fat leads to…
increase in leptin -> signal to hypothalamic centers
- can lead to decrease in NPY -> decrease in hunger
- or increase in alpha-MSH -> increase in CRH
- increase in SNS
- decrease in insulin
Thermoregulation of food intake:
- cold = increased feeding
- hot = decreased feeding
T/F: stress can’t affect food intake
F, it can and it’s not consistent from person to person
Both long term and short term mechanisms help to regulate…
immediate feeding behavior and long term body weight
Example of short term mechanism:
- fullness and CCK (increases)
- ghrelin (decreases)
Example of long term mechanism:
- hyperglycemia
- leptin
- heat
- cold
Energy content is expressed as…
heat units Calorie
- 1 kilocalorie heat to raise 1 L h2o 1 degrees C
How do you measure how many Calories are in food?
burn it in a bomb calorimeter
- amount of heat released is measured
- doesn’t take into account food ingested but not absorbed
How much of each macronutrient is recommended?
- 30% fat
- 10-15% protein
- 55-60% carbs
You can measure energy produced from food by measuring…
- oxygen used to metabolize it
- CO2 produced when it’s metabolized
What is respiratory quotient (RQ)/respiratory exchange ratio (RER)?
rate of CO2 produced to O2 consumed
What is the RQ for each macronutrient?
- pure carbs: 1
- pure protein: 0.8
- pure fat: 0.7
What is the average dietary RQ?
0.82
When do you measure resting metabolic rate?
after 12 hour fast
Skeletal muscle accounts for how much of BMR?
20-30%
What factors affect metabolic rate?
- genetics
- hormones (+)
- diet (+)
- SNS activity (+)
- activity level (+)
- lean muscle mass (+)
- age (-)
- females have less lean muscle than men
- fever (+)
- climate
Examples of hormones that increase metabolic rate?
- TH
- epi/norepi
- testosterone/GH
Nutrient pools of building blocks are used in what three ways?
- metabolized to make ATP
- used as building blocks to make things for growth and maintenance
- stored
Most tissues use ____ as energy source
glucose
What is glycolysis?
breakdown of glucose for energy
Def of essential nutrients:
nutrients that can’t be made and have to be consumed
Energy can be stored as…
- fat in adipose
- glycogen in liver and skeletal muscle
What is lipogenesis?
storage of glucose as fats
- FA + glycerol -> triglyceride
What is lipolysis?
breakdown of fats to use for energy
- triglyceride -> FA and glycerol
What is glycogenesis?
storage of glucose as glycogen
- glucose -> glycogen
What is glycogenolysis?
conversion of glycogen to glucose for use
What is gluconeogenesis?
AA -> glucose and FA
What is the fed state?
- absorptive state
- follows ingestion of nutrients
T/F: fed state is catabolic
F, is anabolic
- nutrients used for energy, synthesis, and storage
What is proteogenesis?
AA -> proteins
- in muscle
What is proteolysis?
proteins -> AA
- in muscle
What is the fasted state?
- postabsorptive state
- between meals
T/F: fasted state is catabolic
T b/c body taps into stored reserves
Fate of carbs in the fed state metabolism:
- glucose is main source of energy and used to make ATP
- some used by liver for lipoprotein
- some stored as glycogen or fat
Glucose enters the cell via what transporter?
GLUT
Fate of amino acids in the fed state metabolism:
- used for protein synthesis
- liver goes first
- cells uptake amino acids
- in muscle: some get stored as phosphocreatine for energy
What does the liver make with amino acids during the fed state metabolism?
- lipoproteins
- plasma proteins (albumins, clotting factors, angiotensinogen
What do cells make with amino acids during the fed state metabolism?
- structural proteins
- enzymes
- hormones
- neurotransmitters
What happens to excess amino acids in the fed state?
- broken down to make ATP
- stored as fat
Fate of fats in fed state metabolism:
- travels as chylomicrons
- gets converted to free FA and glycerol by lipoprotein lipase
- usually used to make ATP by most cells
- metabolized by liver
Examples of chylomicrons:
- cholesterol
- triglycerides
- phospholipids
- apolipoproteins
Where do fats get converted to free FA and glycerol during the fed state metabolism?
capillary endothelium of muscles and adipose
What happens to fats when they are metabolized by the liver during the fed state metabolism?
- cholesterol -> steroids
- some excess cholesterol -> bile salts
- other excess cholesterol -> lipoprotein complexes
Examples of lipoprotein complexes made from fats in the liver:
- VLDL: mostly triglycerides
- LDL: large amounts of cholesterol
- HDL: less fat and more protein
VLDL is used for…
lipoprotein and eicosanoid synthesis
LDL info:
- bad cholesterol
- apoprotein B promotes its absorption into blood vessels
- causes atherosclerosis
HDL info:
- good cholesterol
- apoprotein A promotes uptake into cells
- promotes cellular use in steroids and cell membranes
Function of liver, muscle, and adipose tissue in the fasted state metabolism:
- liver: releases glucose for brain
- muscles: burn stored energy
- adipose: releases FA for use by muscle
Fate of carbs in the fasted state:
- glycogenolysis of glycogen to glucose 6 PO4
- used for energy in liver and muscle
- converted to glucose by liver and released for energy for CNS
Fate of proteins in the fasted state:
- broken down into AA
- AA used to make glucose in liver via gluconeogenesis
- gets deaminated: loss of amino group
How does deamination of proteins in the fasted state occur?
NH3 converted to NH4
- both are converted to urea by liver
- urea gets excreted by kidney
Fate of lipids in the fasted state:
- converted to FA and glycerol by lipases via lipolysis
- glycerol used for glycolysis
In order for FA to be used for energy, it needs to undergo…
beta-oxidation in liver
What happens during beta-oxidation of FA?
- FA -> 2 carbon acyl units
- acyl units -> acetylCoA
- acetylCoA used to make cholesterol and in glycolysis
- excess acyl units (ketone bodies)
What happens to the excess acyl units during beta-oxidation of FA?
- used for E by brain
- too many ketone bodies = ketosis, which lowers body pH
What is the main concern when it comes to the availability of glucose?
making sure there is enough for CNS metabolism
What is the normal resting blood glucose?
90mg/dL
Glucose is regulated by…
pancreatic islet hormones insulin and glucagon
What kind of cells make insulin?
pancreatic beta islet cells
- due to high blood glucose
Insulin dominates in the ____ state and causes an increase in…
fed state and causes an increase in:
- glucose oxidation
- glycogen synthesis
- fat synthesis
- protein synthesis
What kind of cells make glucagon?
pancreatic alpha islet cells
- due to low glucose levels
Glucagon dominates in the _____ state and causes an increase in…
starved state and causes an increase in:
- glycogenolysis
- gluconeogenesis
- ketogenesis
Regulation of glucose is a function of…
insulin to glucagon ratio
Both insulin and glucagon have ____ half lives
short, and are secreted constantly
Insulin is a _____ hormone
anabolic
Insulin is turned on by…
- increase in blood glucose and plasma AA
- feedforward GI hormones like GLP-1 and GIP
- CCK and gastrin
- PNS stimulation to beta cells
Insulin acts on what receptor?
tyrosine kinase receptor
Effects of insulin on the body?
- increases glucose uptake into cell via GLUT-4 transporters in membrane
- promotes phosphorylation of glu to glu-6-PO4 and fat synthesis
- activates enzymes of glycolysis, proteogenesis, and lipogenesis
- inhibits effects of glucagon
- enhances use of AA
Glucagon is turned on by…
- low glucose
- acts on liver to stimulate glycogenolysis and gluconeogenesis
- high AA from eating protein without carbs (stimulates formation of ketone bodies)
What other hormones affect metabolism?
- stress reactions
- thyroid hormone
What are the effects of stress reactions on metabolism?
- increase in cortisol and circulating norepi
- synergistic (opposing) w/ insulin effects
What are the effects of the thyroid hormone on metabolism?
associated with cold stress so should increase metabolism
What is metabolic disorder?
combination of type 2 diabetes, atherosclerosis, and high blood pressure
In order to have a metabolic disorder, you must have at least 3 of the 5 criterias:
- central obesity (waist > 40” women, 35” men)
- BP > 130/85
- elevated fasting triglycerides
- low plasma HDL
- fasting glucose > 110 mg/dL
Metabolic disorder is associated with…
PPARs (proliferator-activated receptors) for lipid and carb metabolism
T/F: body temp rises with decreased metabolism
F, increased metabolism such as during exercise or after meals
Thermoregulation is controlled by…
thermoregulatory centers in the hypothalamus
- signals come from thermoreceptors in the skin
How does heat get lost?
- vasodilation of blood vessels in the skin under sympathetic control
- sweating
How does the body thermostat get reset?
- hot flashes: due to low estrogen
- fever: due to pyrogens, fever producing cytokines
- inflammatory: due to interleukins
- genetics: malignant hyperthermia due to defective Ca2+ channels in skeletal muscle -> overcontraction
