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Metabolism Exam 3
Terms in this set (30)
The organ or tissue in which protein digestion begins is the:
e. small intestine
The nitrogen-containing compound found in the urine that is reflective of somatic protein (i.e., skeletal muscle) in the absence of any disorders of renal function is:
c. uric acid
Kwashiorkor is commonly associated with
a. adequate energy consumption, but insufficient protein intake
b. inadequate energy consumption and protein intake
c. reduced urea cycle activity
d. elevated serum albumin
adequate energy consumption, but insufficient protein intake
Assuming an individual is in nitrogen balance, in what form would most dietary nitrogen be excreted?
e. none of the above
What is the main role of the kidneys in amino acid metabolism?
a. urea production
b. nitrogen excretion
c. nitrogen catabolism
d. transamination and deamination
e. more than one of the above
Which of the following has a half-life of ~14-18 days and could be considered a biomarker of longer-term dietary protein intake?
c. c-reactive protein
d. retinol binding protein
When the diet is lacking in the amino acids lysine and threonine
a. proteins will be made without one amino acid
b. the body will synthesize them
c. protein synthesis will be limited
d. another amino acid will be substituted so that synthesis is uninterrupted
e. none of the above
protein synthesis will be limited
A function of hydrochloric acid in gastric juice during protein digestion is
a. to neutralize the acidity of the stomach
b. to inactivate pepsinogen by suppressing pepsine formation
c. to denature the quaternary, tertiary, and secondary structures of protein
d. to cleave peptide bonds
e. none of the above
to denature the quaternary, tertiary, and secondary structures of protein
What is the name of the genetic disease associated with a defect in one of the proteins in the branched-chain ketoacid decarboxylase complex
a. maple syrup urine disease
d. lactase deficiency
e. none of the above
maple syrup urine disease
Under which scenario would upregulation of the glucose-alanine cycle be most likely?
a. someone is in positive nitrogen balance
b. during prolonged fast
c. following consumption of a high glucose meal
d. in an individual with elevated BUN
e. none of the above
during a prolonged fast
For whom would creatinine levels be contraindicated for use as an indicator of muscle mass?
a. an extremely fit individual
b. an individual with severe liver cirrhosis
c. an elderly individual
d. an individual with compromised renal function
an individual with compromised renal function
When would an individual most likely be in positive nitrogen balance?
a. when following a high protein diet
b. when following a low calorie diet
c. during weight loss
d. during pregnancy
Why is glutamine supplementation recommended for individuals who are being fed intravenously?
a. glutamine is a primary source of energy for intestinal bacteria
b. glutamine can promote bacterial translocation
c. glutamine can help prevent atrophy of intestinal cells
d. glutamine is an essential amino acid
glutamine can help prevent atrophy of intestinal cells
Which of the following recommendations would be most beneficial for promoting protein synthesis and increased lean body mass?
a. consume a high protein/low calorie diet
b. consume meals that contain a mixture of both carbohydrates and proteins
c. consume primarily plant-based proteins
d. consume only "fast" proteins as those are the most rapidly absorbed
consume meals that contain a mixture of both carbohydrates and proteins
Which of the following is not an example of a functional role of proteins?
a. enzymes (e.g., phosphofructokinase)
b. hormones (e.g., insulin)
c. fluid balance (e.g., albumin)
d. fatty acid transport (e.g., carnitine)
fatty acid transport (e.g., albumin)
List the 9 essential amino acids
phenylalanine, leucine, isoleucine, lysine, histidine, tryptophan, threonine, valine, methionine
What is the definition of a conditionally essential amino acid?
they become essential when the body can no longer make them or metabolism is inhibited (tyrosine in the instance of someone with PKU)
In times of excess energy and protein intakes, coupled with adequate carbohydrate intake, the carbon skeleton of amino acids may be used to synthesize
If an individual takes in 90 grams of protein in a 24-hour period, and as a urinary urea nitrogen (UUN) output of 10.3 mg/ml and a 24-hour urine volume of 1,200 ml, would they be in positive or negative nitrogen balance. Show your calculations.
90 x .16 = 14.4 g
10.3 mg/ml x 1,200 ml = 12,360 mg / 1,000 = 12.36g
14.4 - (12.36 + 4) = -1.96
negative nitrogen balance
Referring to the individual in question 19, how many grams of protein would they need to consume to achieve nitrogen balance. Please show all calculations.
1.96g x 100% = 196/16 = 12.25g
12.25g + 90g (original) = 102.25 total grams of protein
Explain why enternal nutrition formulas often provide amino acids as peptides rather than as individual amino acids.
it provides them as peptides because they can be utilized immediately for protein needs/ energy requirements and no longer require the cellular mechanisms to be broken down from large polypeptides. incorporating peptide bonds is more efficient and allows for direct use and little cellular processes.
Name at least two uses for amino acid carbon skeletons besides energy production
glucose production, fatty acid synthesis, carbohydrate production
Why would blood urea nitrogen levels (BUN) be decreased with advanced liver disease but increased in renal failure?
decreased because the liver can no longer make urea, increased in renal failure because the body cannot excrete the nitrogen like it normally can
Explain why the avoidance of fasting is a necessary precaution for both carbohydrate and fatty acid related inborn errors of metabolism.
inborn errors of metabolism mean that the person cannot breakdown glycogen, causing hypoglycemia to be a major concern. hypoglycemia happens when the body's blood glucose level is lower than normal, which usually occurs in a fasting state.
Explain how vegans can meet all their essential amino acid needs via diet alone even though plant-based proteins tend to be incomplete protein sources
there are plant based sources that are complete protein sources (quinoa), or they can combine foods to make a complete protein source (peanut butter and bread)
Explain the observation that urinary urea nitrogen excretion will increase with both an excessive intake of dietary protein and in an individual who is undergoing a prolonged fast?
with an excessive intake of dietary protein they are consuming more protein than needed, causing an increase in the excretion of UUN. during a prolonged fast, the body is having to breakdown proteins (skeletal muscle) to make ends meet, so there is also an increase in UUN excretion
Chocolate milk is often handed out to competitors at the end of endurance type sporting events and advertised as an excellent post workout beverage choice. Based on your knowledge of the macronutrient content of milk, provide at least 3 reasons to support the consumption of chocolate milk by athletes besides hydration. (Hint: Though this is a protein-based exam, your responses should also have something to do with carbohydrate content as well).
can help replete glycogen stores because of its carbohydrate content, both fast and slow proteins are present, which allows it to recover muscles after strenuous exercise
Serum albumin is commonly used as a clinical indicator of visceral protein status, but it does have some contraindications. Provide at least 2 clinical scenarios when serum albumin levels might not accurately reflect patient protein status and explain why.
for an acute hospitalization- albumin has a half life of 14-18 days, so it provides an indication of protein intake over the past two weeks, not the past two days which could be needed in the instance of a car crash.
acute renal failure can result in hypervolemia (decreased urinary output) which will dilute serum albumin levels and can lead to edema
Define the glucose-alanine cycle and explain its importance in the prevention of skeletal muscle breakdown during a fasting state.
the glucose-alanine cycle transfers an amino group from glutamate to pyruvate to form alanine. alanine is transferred to liver and is stored until energy is needed and is reformed into glucose to be used for energy. the glucose-alanine cycle provides glucose to the body for energy so skeletal muscle does not have to be broken down for energy.
Describe the difference in transamination and deamination reactions and their utility in protein balance and amino acid catabolism.
transamination is the transfer of an amino group of an amino acid to a new compound. this is important for nonessential amino acid synthesis. deamination is the removal of an amino group with no transfer to a new compound. this helps rid the body of nitrogenous waste by creating ketoacids, ammonium, and alpha keto acids
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