nutrient
substance that promotes normal growth, maintenance, and repair
major nutrients
carbohydrates, lipids, and proteins
micronutrients
other nutrients"; vitamins and minerals and water
what do the body cells use glucose for?
to make ATP
what relies on glucose in our body?
neurons, red blood cells, and actively contracting skeletal muscle.
what happens to excess glucose?
it is stored as glycogen or fat
triglycerides
most abundant dietary lipids; found in animal and plant foods
lipids
-energy fuel of hepatocytes and resting skeletal muscle
-component of myelin sheaths and cell membranes
-cholesterol
What does cholesterol do?
stabilizes membranes and is a precursor of bile salts and steroid hormones
essential amino acids
8 total; must be obtained in the diet and are building blocks for the nonessential amino acids
if there is insufficient carbohydrate or fat available, what is used for fuel?
proteins
vitamins
-organic compounds needed for growth and good health
-absorbed in GI tract
-crucial in helping our body use nutrients
what is special about vitamin B12?
it requires gastric intrinsic factor to be absorbed
Fat-soluble vitamins
(ADEK) bind to ingested lipids and are absorbed with them.
antioxidants
neutralize free radicals by donating electrons. (vitamins ACE)
free radicals
unstable compounds that "steal" electrons from stable molecules; can cause disease like cancer and CAD
how to most vitamins function?
as coenzymes
main minerals
Ca, P, K, S, Na, Cl, Mg
trace minerals
required in lesser amounts (ex: Fe, Cr)
metabolism
all chemical reactions necessary to maintain life
anabolic reactions
synthesis of larger molecules from smaller ones
catabolic reactions
hydrolysis of complex molecules into smaller ones
cellular respiration
food break down within cells; energy captured to produce ATP
in metabolic processes, what do enzymes do?
shift high-energy phosphate groups of ATP to other molecules
phosphorylated molecules in metabolism do what?
are activated to perform cellular functions
oxidized substances
lose energy (electrons)
reduced substances
gain energy (electrons)
What are coenzymes roles in redox reactions?
act as hydrogen(or electron) acceptors
important coenzymes in redox
nicotinamide adenine dinucleotide and flavin adenine dinucleotide
carbohydrate metabolism
glucose metabolism" because all carbs are transformed to glucose in 3 pathways
3 pathways glucose is catabolized in are?
1) glycolysis
2) krebs cycle
3) electron transport chain and oxidative phosphorylation
glycolysis
-glucose is oxidized to pyruvic acid which moves on to krebs cycle in an aerobic environment
-2 NAD+ reduced to 2 NADH
-net gain of 2 ATP
pyruvic acid
aerobic environment: moves on to krebs
anaerobic environment: reduced to lactic acid
Krebs Cycle
-pyruvic acid converted to acetyl CoA
-1 glucose=2 acetyl CoA entering krebs
what does krebs cycle generate?
-4 NADH
-1 FADH
-1ATP
-2 CO2
electron transport chain
glucose oxidized and the released hydrogens are transported by coenzymes NADH and FADH2; then enter a hain of proteins bound to metal atoms(cofactors) and combine with O2 to form water.
-RELEASE ENERGY**
energy released from ETC does what?
harned to attach inorganic phosphate groups (Pi) to ADP, making ATP (by oxidative phosphorylation)
gylcogenesis
formation of glycogen when glucose in excess
glycogenolysis
breakdown of glycogen--in response to low blood glucose
gluconeogenesis
forming sugar from noncarbohydrates; happens in the liver.
--protects the body from hypoglycemia
Lipid metabolism
glycerol and fatty acids enter krebs cycle when converted to acetyl CoA
lipogenesis
excess dietary glycerol and fatty acids undergo lipogenesis to form triglycerides
why is glucose easily converted to fat?
because acetyl CoA is a starting molecule for the synthesis of fatty acids
lipolysis
the breakdown of stored fat.
lipid metabolism in the liver
1) synthesizes lipoproteins for transport of cholesterol and fats
2) synthesizes cholesterol from acetyl CoA
3) uses cholesterol to form bile salts
protein metabolism
amino acids assembled into proteins with instructions from enzymes
what does excess dietary protein result in?
amino acids being oxidized for energy or converted into glycogen or fat for storage
oxidation of amino acids
results in ammonia which is converted to urea by the liver which then is excreted by the kidney.
absorptive state
when nutrients are flushed into the blood
what is the major metabolic thrust of the absorptive state?
anabolism and energy storage
what happens to amino acids(1), glycerol/ fatty acids(2), and glucose(3) in absorptive state?
(1) become proteins
(2) are converted to triglycerides
(3) stored as glycogen
what is the role of dietary glucose in the absorptive state?
it is the major energy fuel
Absorptive state in the muscle:
-amino acids become protein
-glucose is converted to glycogen
Absorptive state in the liver:
-amino acids become protein or are deaminated to keto acids
-glucose stored as glycogen or converted to fat
Absorptive state in adipose tissue:
glucose and fatty acids/glycerol are converted and stored as fat
Insulin controls absorptive state and its secretion is stimulated by what?
-increased blood glucose
-elevated amino acid levels in the blood
-gastrin, CCK, and secretin
what does insulin enhance?
1) facilitated diffusion of glucose into tissue
2) active transport of amino acids into tissue cells
Postabsorptive state
GI tract is empty and breaksdown reserves
What is the major metabolic thrust of the postabsorptive state?
catabolism and replacement of fueld in the blood
What happens to triglycerides(1), glycogen(2), and proteins(3) in the postabsorptive state?
(1) broken into glycerol and fatty acids
(2) becomes glucose(via glycogenolysis)
(3) broken down to amino acids
ho might glucose be provided during the postabsorptive state?
gluconeogenesis
what are the major energy fuels of the postabsorptive state?
fatty acids and ketones
Postabsorptive state in the liver:
amino acids are converted to glucose
Glucagon
hormone of the postabsorptive state from the pancreas that stimulates (1) glycogenolysis and gluconeogenesis, (2) lipolysis in adipose tissue, (3) glucose sparing
what stimulates glucagon?
decreased plasma glucose concentration and rising amino acid levels
epinephrine in the postabsorptive state:
released by the sympathetic nervous system in response to a sudden drop in plasma glucose.
-acts on the liver, skeletal muscle, and adipose tissue to mobilize fat and promot glycogenolysis
thyroxine in the postabsorptive state
in the thyroid gland, stimulates glucose catabolism and lipolysis
cortisol in the postabsorptive state
in the adrenal glands, stimulates lipolysis and gluconeogenesis and protein catabolism
growth hormone in the postabsorptive state
in the pituitary gland-mostly only important when we are young
cholesterol
required to produce bile salts, steroid hormones, and vitamin D
how is cholesterol transported?
via lipoproteins
what are the lipoprotein classifications?
-HDLs
-LDLs
-VLDLs
HDLs
-high density lipoproteins
-have more protein content
-protect against CAD
-transport excess cholesterol from peripheral tissues to the liver
-serve needs of steroid-producing organs
LDLs
-low density lipoproteins
-have a considerable cholesterol component
-high levels linked to CAD
-derived from VLDLs
-transport cholesterol to peripheral tissues
VLDLs
-very low density lipoproteins
-mostly triglycerides
-transport triglycerides to peripheral tissues(especially adipose)
Unsaturated fatty acids
enhance excretion of cholesterol from body
Saturated fatty acids
inhibit excretion of cholesterol from body
unsaturated fatty acids like omega-3s can do what?
lower proportions of saturated fats and cholesterol
what stimulates hunger?
glucagon and epinephrine
what depresses hunger?
insulin and CCK; also increased body temperature
Leptin
-secreted by adipose tissue
-overall "satiety" signal
-acts on hypothalamus to control appetite
-suppresses secretion of neuropeptide Y(an appetite stimulant)
what two things can play a role in leptin release?
blood levels of insulin and glucocorticois
Ghrelin
-hunger hormone
-stimulates appetite
-levels increase before a meal and decrease after.
-counterpart of leptin
metabolic rate
-rate of energy output equal to the total heat produced by all chemical reactions in the body and the mechanical work of the body.
-measure via calorimeter or respirometer
Basal Metabolic Rate (BMR)
energy the body needs to perform the most essential activities
Total Metabolic Rate (TMR)
total rate of kilocalorie consumption to fuel all ongoing activities of the body.