Test 3- Nutrition and Metabolism (part 2)

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Lipolysis and Oxidation of Glycerol and Fatty Acids

eating too much, storing fats

Lipids =


lipids ->Triglycerides

between meals, broken down to: 1) glycerol and 2) fatty acids

occurs in response to:

epinephrine, norepinephrine, glucocorticoids, thyroid hormone, GH

products released into bld stream

serve as source of energy for other cells


-- converted to G3P via gluconeogenesis
-- enters glycolysis -> produces NADH & 2 ATP
-- continues thru Citric Acid cycle

[Free] Fatty Acids

-- beta-oxidation to form acetyl-CoA
-- enters Citric Acid cycle


-- production of lipids (fat stores)
-- excess glucose -> G3P -> glycerol
-- excess a.a.'s -> acetyl-CoA -> fatty acids

Protein Metabolism

protein taken in from diet -> broken down to amino acids

Oxidation of Amino Acids

amino acids broken down into intermediates (keto acids) -> enter Citric Acid cycle

first step = deamination

removal of amine grp -> converts amino acid into keto acid

Protein Synthesis

all composite amino acids need to be present in order to make the protein
-- if one missing, protein not made -> a.a.'s used for energy

Absorptive State

'Fed' State

Absorptive State

-- 4 hrs during & after each meal
-- nutrients from food in bld stream
-- ANABOLIC rxns exceed catabolic rxns

Absorptive State

excess metabolites, regardless of source, converted to fat

Fed State- Carbohydrate Absorption

all absorbed monosaccharides -> go to liver

Fed State- Triglycerides

primary energy source for: - adipose cells
- liver cells
- heart
- skeletal muscle cells (resting)

Fed State- Triglycerides

used by other cells when carbohydrates are limited

Fed State- Triglycerides

most fatty acids & glycerol -> converted to triglycerides -> stored in adipose tissue

Fed State- Amino Acids

to keto bodies
to body to make proteins

Fed State- Insulin

primary hormone promoting absorptive state

Fed State- Insulin

insulin -> b cells (pancreas) -> tissue cells -> active transport or facillitated diffusion of glucose into cells -> proteinsynthesis or ATP, glycogen, fatty acid&glycerol -> tryglyercide

Postabsorptive State

in btw meals; after nutrients from meal absorbed from bld

Postabsorptive State

-- net synthesis of protein, fat, glycogen STOPS
-- CATABOLIC rxns of glycogen, fat, protein BEGINS

Postabsorptive State

goal: maintain bld glucose between 70-110 mg/dL bld (for brain)

Postabsorptive State - Glucose sources

Glycogen breakdown (glycogenolysis) in liver -> release glucose to bld stream

Postabsorptive State - Glucose sources

Glycogen breakdown in skeletal muscle -> used in muscle itself

Postabsorptive State - Glucose sources

Fat breakdown (lipolysis) in liver & adipose

Postabsorptive State - Glucose sources

Cellular protein breakdown in liver & muscle

Postabsorptive State - Glucagon

strongly promotes postabsorptive pathways to increase bld glucose

Postabsorptive State - Glucagon (fight or flight, sympathetic)

glucagon -> liver (glycogenolysis or gluconeogensis to incre. glucose) OR glucagon -> adipose tissue -> fat brkdown (lypolysis) -> glycerol and fatty acids -> bldstream -> used by other cells in body

Cholesterol Supply

-- 15% comes from diet
-- 85% is made by liver from acetyl-CoA

Cholesterol Supply

in liver, cholesterol is catabolized to bile salts  excreted in feces

Cholesterol Transport and Function

cholesterol not water-soluble -> transported in lipoprotein complexes

Cholesterol Transport and Function

start= triglyeride 90% , cholesterol 5%
end= triglercride 5%, cholestrol 20%

*low density lipoprotein (LDL) to high density (HDL)
HDL= good cholesterol

Recommended Cholesterol Levels

total = LDL + HDL
less than 200 mg/dl or mg/100ml

HDL (good)

above 40mg/dl. increase by excercise, monounsaturated fatty acids (canola oil, olive oil). decrease by cigarattes stress coffee

LDL (bad)

less than 130 mg/dl
decre. by excercise, increase by trans fats and overeating

regulation of food intake

energy input = energy output

energy input

digested and absorbed food

energy output

1 heat 2 atp -> work 3 storage (growth, fat)

Neural signals from digestive tract

vagal signals from chemoreceptors & stretch receptors -> inhibit appetite

Nutrient Signals

-- incr blood levels of glucose, amino acids, fatty acids -> inhibit appetitie


insulin, CCK -> inhibit appetite


glucagon (from pancreas), ghrelin (produced by stomach) -> stimulate appetite

Body Temperature

incre. body temp -> inhibit appetite

Psychological Factors

-- appearance, smell, taste of food
-- depression/anxiety -> stimulate or inhibit appetite
-- compulsive behavior

Metabolic Rate

total heat produced by all chemical rxns and mechanical work by body

Basal Metabolic Rate (BMR)

energy burned to perform only essential activities (~1400 kcal/day)
(e.g. breathing; resting levels of organ function)

Basal Metabolic Rate (BMR)

lowest metabolic rate occurs during sleep

Basal Metabolic Rate (BMR)

related to body surface area -> heat loss

Total Metabolic Rate

energy burned for all activities
-- most increases come from skeletal muscle activity
2000 cal for men; 1800 cal for women

Total Metabolic Rate increased by

pregnancy, anxiety (epinephrine -> msucle tension), fewer/incr body temp, thyroxine (TH)

Total Metabolic Rate decreased by

depression, cal defficiency, age

Heat Production

-- produced by all organs of body
-- incr dramatically by muscular activity

body temp

~37oC (98.6oF) (35.8—38.2 oC) for proper rates of biochem rxns

if too high ->

neurons depresed, proteins denature -> enzymes stop working

if too low ->

bio chem rxns slower, but usually ok if not very cold

Body Temperature Regulation

Hypothalamus is main integration center for thermoregulation


controlled hyperthermia, ususally due to infection


pyrogen cytokines released by macrophages stim. hyptothalamus; hypothalamus temporarily set body temp higher


vasoconstriction in skin; shivering

when Fever breaks->

sweating and vasodilation in skin

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