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What is special about leucine, isoleucine, and valine?

  • They are branch-chained amino acids
  • Metabolized in muscle
  • Possibly important in patients with liver failure
  • They are essential amino acids


[The essential amino acids are leucine, isoleucine, valine, arginine, histidine, lysine, methionine, phenylalanine, threonine, and tryptophan.]


Which vitamin deficiency is characterized by all of the following?

  • Impaired decarboxylation of factors II, VII, IX, and X
  • Prolongation of prothrombin time (INR)

Vitamin K deficiency


What is the difference between the composition of central line parenteral nutrition (TPN) and peripheral line parenteral nutrition (PPN)?

  1. TPN is glucose based (10% amino acid solution, 50% dextrose solution, electrolytes, minerals, and vitamins. Lipids are given separately from TPN)
  2. PPN is fat based


[The maximum glucose administration in TPN is 3 g/kg/hr.]


What is the Cori cycle?

  1. Glucose is utilized and converted to lactate in the muscle
  2. Lactate then goes to the liver and is converted back to pyruvate and eventually to glucose via gluconeogenesis
  3. Glucose is then transported back to the muscle


What are the acute indicators of nutritional status?

  • Retinal binding protein
  • Prealbumin
  • Transferrin


What are the 4 precursors to gluconeogenesis?

  1. Amino acids (especially Alanine)
  2. Lactate
  3. Pyruvate
  4. Glycerol


In which patients should protein intake be limited and why?

Patients with liver or renal failure should have limited protein intake to avoid buildup of ammonia and possible worsening of encephalopathy


When do the following postoperative phases typically occur?

  • Diuresis phase
  • Catabolic phase
  • Anabolic phase

  • Diuresis phase: POD# 2-5
  • Catabolic phase: POD# 0-3 (negative nitrogen balance)
  • Anabolic phase: POD# 3-6 (positive nitrogen balance)


What do the following respiratory quotients indicate?

  • RQ < 0.7
  • RQ = 0.7
  • RQ = 0.8
  • RQ = 1.0
  • RQ > 1

  • RQ < 0.7: Ketosis and fat oxidation (Starvation)
  • RQ = 0.7: Pure fat utilization
  • RQ = 0.8: Pure protein utilization
  • RQ = 1.0: Pure carbohydrate utilization
  • RQ > 1: Lipogenesis (Overfeeding)


[Respiratory quotient is the ratio of CO2 produced to O2 consumed. It is a measurement of energy expenditure.]


What is the appropriate calorie breakdown by percentage for an average healthy adult male?

  • Protein
  • Fat
  • Carbohydrates

  • Protein: 20% (1 g protein/kg/day)
  • Fat: 30%
  • Carbohydrates: 50%


[20% protein and 30% fat should be essential amino acids and essential fatty acids respectively.]


How long do glycogen stores last after onset of starvation?

24-36 hours


[2/3 of glycogen is in skeletal muscle, 1/3 of glycogen is in the liver. After glycogen stores are depleted, the body begins to metabolize fat stores.


The Harris-Benedict equation calculates basal energy expenditure based on which 4 factors?

  1. Weight
  2. Height
  3. Age
  4. Gender


What is the difference between the energy sources utilized in starvation vs in trauma or postoperative patients?

Fat (ketones) are the main source of energy in both, however, in trauma/postop patients the energy source is more mixed (fat and protein)


[Protein-conserving mechanisms do not occur after trauma or surgery secondary to catecholamines and cortisol. Most patients can tolerate a 15% weight loss without major complications.]


What activates trypsinogen?

Enterokinase released from the duodenum


[Trypsin can then autoactivate other trypsinogen molecules.]


What are the two essential fatty acids and what are they needed for?

  1. Linolenic acid
  2. Linoleic acid


They are needed for prostaglandin synthesis (long-chain fatty acids) and they are important for immune cells



What are the half-lives of the following proteins?

  • Albumin
  • Transferrin
  • Prealbumin

  • Albumin: 18 days
  • Transferrin: 10 days
  • Prealbumin: 2 days


Where do carbohydrate and protein digestion begin, respectively?

  • Carbohydrate: Mouth with salivary amylase (followed by pancreatic amylase and disaccharidases)
  • Protein: Stomach with gastric pepsin (followed by trypsin, chymotrypsin, and carboxypeptidases)


What are the formulas for calorie and protein requirements in a burn patient?

  • Calorie requirement = 25 kcal/kg/day + (30 kcal/day x % burn)
  • Protein requirement = 1-1.5 g/kg/day + (3g x % burn)


Refeeding syndrome results in decreased levels of which 3 minerals?

  1. K
  2. Mg
  3. PO4


[This causes cardiac dysfunction, profound weakness, and encephalopathy. Refeeding syndrome can be prevented by starting to re-feed at a low rate (10-15 kcal/kg/day).]


What is the main effect of a deficiency of the following vitamins?

  • Vitamin A
  • Vitamin K
  • Vitamin D
  • Vitamin E

  • Vitamin A: Night blindness
  • Vitamin K: Coagulopathy
  • Vitamin D: Rickets, osteomalacia, osteoporosis
  • Vitamin E: Neuropathy


What is the primary fuel for the following cell types?

  • Colonocytes
  • Small bowel enterocytes
  • Neoplastic cells

  • Colonocytes: Short-chain fatty acids such as Butyric acid
  • Small bowel enterocytes: Glutamine
  • Neoplastic cells: Glutamine


What are 3 preoperative signs of poor nutritional status?

  1. Acute weight loss > 10% in 6 months
  2. Weight < 85% of ideal body weight
  3. Albumin < 3.0


[Albumin < 3.0 is a strong risk factor for morbidity and mortality after surgery.]


Which amino acid is the primary substrate for gluconeogenesis?



[Alanine is the simplest amino acid precursor for gluconeogenesis. Alanine and phenylalanine are the only amino acids to increase during times of stress. In late starvation, gluconeogenesis occurs in the kidney.]


Which 4 cells/tissues are obligate glucose users?

  1. Peripheral nerves
  2. Adrenal medulla
  3. Red blood cells
  4. White blood cells


[Glucose is the primary energy source for the brain, however, in starvation the brain utilizes ketones.]


Whats the difference between Kwashiorkor and Marasmus?

  • Kwashiorkor = Relative protein deficiency
  • Marasmus = Starvation


What is the difference between the absorption of long-chain fatty acids and medium- or short-chain fatty acids?

  • Long-chain fatty acids: taken up into micelles which enter enterocytes by fusing with the membrane
  • Medium- and short-chain fatty acids: Enter enterocytes by simple diffusion


[Long-chain fatty acids enter lymphatics along with chylomicrons. Medium- and short-chain fatty acids enter the portal system along with amino acids and carbohydrates.]


What are the ideal body weights for men and women respectively?

  • Ideal body weight of a man = 106 lbs + 6 lbs for each inch over 5 ft tall
  • Ideal body weight of a woman = 100 lbs + 5 lbs for each inch over 5 ft tall


Which vitamin deficiency is characterized by all of the following?

  • Poor wound healing
  • Fragile capillaries resulting in easy bruising and gingival bleeding

Vitamin C deficiency


How are saturated and unsaturated fatty acids used differently by the body?

  • Saturated fatty acids: Used for fuel by cardiac and skeletal muscles
  • Unsaturated fatty acids: Used as structural components for cells


Which amino acid is the most common amino acid in the bloodstream and tissue, helps with nitrogen excretion by releasing NH4 in the kidney, and can be used for gluconeogenesis?



[Glutamine is the primary fuel for small bowel enterocytes.]