The Nutritional Value of Fats and Proteins Flashcards
What is the body’s premium reserve fuel?
Fats
What are the functions of protein?
structural dietary component and energy source
What is the key structural material of the diet?
protein
Protein is used to form
all structural components (eg collagen) and enzymes for metabolism
What are the general steps of protein digestion?
denaturing of dietary protein, rendering it to amino acids, transport them via multiple gut transporters
What are the implications of branched chain amino acids on performance?
eg valine, leucine, and isoleucine - transaminate in muscles but have no proven role as performance-enhancing
How much protein is made and broken down by the body per day?
300g
How much of our amino acids are recycled under normal conditions?
2/3rds
Broken down amino acids are used for
carbon sources for fuel
Amino acids make non-protein products such as
neurotransmitters
What is the major waste product to remove excess nitrogen?
urea (some ammonia can be passed direct from kidneys)
Breakdown of proteins in fasting fuels
formation of glucose and ketone bodies to maintain brain and RBCs
Acetyl-coA is never metabolised to
pyruvate; ie C from fat never becomes C in glucose
Fatty acids are metabolised to and from
Acetyl-coA
Why can’t the brain use fats for energy?
long-chain fatty acids cannot cross the BBB
Fat cells produce what hormones?
leptin and adiponectin to tell the brain how much fat is stored
Hormone sensitive lipase
triacylglycerol lipase: converts TAGs to FFAs and glycerol
What is the role of carnitine?
Carries fatty acids from fatty acyl-coA across the mitochondrial membrane into the matrix - this is a rate limiting step of beta oxidation
What is the role of malonyl-coA?
it is a precursor of fat synthesis and inhibits high energy and blocks the carnitine acytltransferase from transferring fatty acyl-coA into the mitochondrial matrix for beta oxidation (ie fat is being made so don’t break it down)
Fats are made in the
cytosol
Fats are broken down in
mitochondria
Beta oxidation of palmitate produces what yield of ATP via acetyl-coA in Krebs?
106 ATP/palmitate
What is the role of citrate?
exits from mitochondria into cytosol to generate acetyl-coA
Palmitate is synthesized by
polymerization of acetyl-coA (formed by citrate) by fatty acid synthase
Ketone bodies are made by
liver mitochondria to fuel other organs in starvation
Ketone bodies are a mixture of
acetoacetate, B-hydroxybutyrate, and acetone (breath only)
Ketone body production follows the same pathway as
cholesterol synthesis up to HMG-CoA, but cholesterol is only made in cytosol by HMG-CoA reductase
Cholesterol is only made in
cytosol
NADH generated in beta oxidation is used
to generate B-hydroxybutyrate from acetoacetate for energy
Ketoacidosis
metabolic acidosis due to high concentrations of ketone bodies as a result of failure to produce insulin - unregulated levels of ketone bodies and blood glucose
Ketosis
metabolic state where energy supply is ketone bodies (eg starvation) and insulin and blood glucose are low
What happens when glycogen stores are depleted (eg starvation)?
protein is broken down to amino acids for gluconeogenesis; after 3-4 days more and more ketone bodies are produced; glucose is maintained by gluconeogenesis from proteins and glycerol from TAG metabolism to FFAs
Omega fatty acids in fish oils are
eicosapentaenoic (6) acid and docosahexaenoic (3) acid (essential fatty acids)
What are the beneficial effects of omega 3 fatty acids?
inhibit production of leukotrienes (inflammation) and thromboxanes (platelet aggregation, thrombosis); promote production of prostacyclins (antithrombotic)
What is the dietary requirement for protein?
0.6-0.8g/kg body weight
What is pellagra?
disease of the 4 D’s - photosensitive dermatitis, diarrhea, dementia, death; caused by niacin deficiency (eg corn diet with no tryptophan, precursor to niacin)
Transamination
transfers an amino group from an amino acid to a ketone producing a new amino acid and a keto acid
What is the function of the alanine cycle?
alanine is produced by muscle to carry nitrogen from muscle protein breakdown to the liver where it is transaminated to make urea; the carbon is recycled as glucose
Gout is caused by
uric acid crystals and resulting inflammation
Gout can be treated with
allopurinol, a xanthine oxidase inhibitor; NSAIDs, and corticosteroids to treat the inflammation
