Dietary Protein Flashcards
Summarize the major steps in protein digestion.
- Enzymes mediate hydrolysis of proteins into single AA’s that can be absorbed
- in the stomach, pepsin is the major proteolytic enzyme
- in the small intestines, substances secreted by the pancreas further break down the partially digested material from the stomach.
- bicarbonate neutralizes the stomach acid. This raises the pH for optimal range for digestive enzymes.
- enteropeptidase cleaves typsinogen»>trypsin
- trypsin then cleaves other zymogens
Summarize the major steps in protein absorption.
Specific transport proteins transfer AAs into the intestinal cells where some are used and the rest are transported via the blood to the liver.
Describe the conversion of digestive zymogens to their active form.
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What is an essential amino acid? List them.
An amino acid that the body cannot make at all or cannot make in sufficient quantities to meet its needs.
Histidine Isoleucine Leucine Lysine Methionine Phenylalanine Threonine Tryptophan Valine
What is the recommended protein intake?
50% carbohydrate
20% fats
30% proteins
Where is the major source of Amino acid metabolism?
liver
Other than soybeans, plant sources do not provide all the essential amino acids. Give an example of plant combinations that do.
beans + corn
beans + rice
How many calories are in a gram of protein?
4 calories
Unlike carbohydrate and fat, protein does not have a specialized form of ?
storage
If not supplied by diet, protein will be acquired from?
working and structural components of the cells and tissues
What does starvation always cause?
wasting of lean body tissue in addition to fat loss
How do you spare proteins from being used for energy and allow them to perform their unique and important roles?
Take in adequate carbohydrate and fat
In what form is pepsin secreted? Where is the zymogen stored? How is it changed?
Produced and secreted by gastric cells as pepsinogen.
HCl produced by parietal cells induces conformational change that causes pepsinogen to be cleaved to active pepsin.
What cleaves trypsinogen?
enteropeptidase
Where is enteropeptidase released?
small intestines
What would happen if enteropeptidase malfunctioned?
- trypsin would not be produced
- chymotrypsin would not be produced
- elastase would not be produced
- carboxypeptidase would not be produced
**failure to thrive, diarrhea, hypoproteinemia
Where is chymotrypsinogen synthesized?
pancreas
Where is proelastase synthesized?
pancreas
Where is procarboxypeptidase synthesized?
pancreas
If the patient was unable to produce HCl, what would the patient experience?
- deficiencies in protein digestion and absorption
- malnourishment
What is the first step in the use of protein for energy production?
deamination (removal of N-containing amino group)
What two products result from deamination?
ammonia (NH3)
keto acid
Because ammonia is toxic, what does the liver do?
combines ammonia with carbon dioxide to produce urea and water
At what protein consumption level does the maximum urea production occur?
250 grams/day
How would you diagnose disease of liver?
blood ammonia is high
How would you diagnose kidney disease?
blood urea is high
How much water should a person drink if they are on a high protein diet?
> 100 grams/day
What is chronic protein-energy malnutrition called? What are the symptoms?
Marasmus
- infancy (<2)
- develops slowly
- severe weight loss
- severe muscle wasting
- no detectable edema
- no fatty liver
- skin is dry, thin and easily wrinkles
What is acute protein-energy malnutrition called? What are the symptoms?
Kwashiorkor
- older infants and young children (1-3 years)
- rapid onset
- some weight loss
- some muscle wasting
- edema
- fatty liver
- loss of appetite
- skin develops lesions
Why would you see edema in Kwashiorkor?
decreased plasma protein in circulation
What 2 tests could you perform to confirm Kwashiorkor?
BUN (Blood urea nitrogen)
Creatinine clearance tests
What results would confirm Kwashiokor from the BUN test?
lower than normal levels (<6 mg/dL) are seen in low protein diet or malnutrition
What does the BUN test measure?
the amount of urea nitrogen in the blood
Urea nitrogen is what is formed when protein breaks down
What does the creatinine clearance test measure?
compares the creatinine level in the urine with the creatinine level in the blood.
Higher levels indicate muscle breakdown
In elderly patients, creatinine clearance appears to decrease with age
What results would confirm Kwashiokor from the creatinine clearance test?
higher than normal levels indicate breakdown of muscle
Male: 97-137 ml/min
Female 88-128 ml/min
Why do Kwashiorkor patients have increased infections?
damaged immune system due to the body breaking down antibodies
What enzyme is lacking in patients with PKU?
phenylalanine hydroxylase (PAH)
What inheritance type is PKU?
autosomal recessive
In addition to light pigmentation, what other symptoms may be present in PKU?
- delayed mental and social skills
- small head size
- hyperactivity
- jerking movements
- seizures
- skin rashes
What are some foods that contain phenylalanine? What supplements should be added to the diet?
aspartame
Supplements:
- fish oil
-iron
What amino acids are not able to be broken down by Maple Syrup Urine Disease patients?
branched chain amino acids
BCAA
What inheritance type is MSUD?
autosomal recessive
Which four genes can mutate to result in MSUD?
BCKDHA
BCKDHB
DBT
DLD
- genes form a complex to catabolize branched chain amino acids (BCAAs)
What is the name of the MSUD complex?
BCKD - mutation in BCKD is the most common reason for MSUD
What symptoms appear with MSUD?
poor feeding
vomiting
lethargy
developmental delay
What treatment is available for MSUD?
diet low in branched chain amino acids (Val, Leu, Ile)
fish oil supplements
iron supplements
some patients pursue a liver transplant
An infant with PKU would be expected to be deficient in what non-essential amino acid?
tyrosine
A mother is informed that products containing aspartame could be detrimental to her child’s health. What is the likely genetic disorder?
PKU
