9. Proteins

Question 1

Essential Amino Acid vs. Limiting Amino Acid

Answer 1

• essential amino acids are required because body can’t make them on its own
• limiting amino acids
  one of the essential amino acids is lacking in quantity to support growth of protein

Question 2

Complete Protein

Answer 2

contains every amino acid in sufficient quantities (animal sources contain all essential amino acids while plants are lacking in some)

Question 3

How is the quality of a protein determined?

Answer 3

By evaluating a protein based on requirements of the human body and their ability to digest it

Question 4

What is the role of stomach acid in protein digestion?

Answer 4

Stomach acid activates pepsin and denatures the proteins

Question 5

Endopeptidase vs. Exopeptidase

Answer 5

• endopeptidase breaks bonds within the polypeptide chain

- exopeptidase breaks the bonds at the end of the chain

Question 6

How are amino acids absorbed?

Answer 6

They’re absorbed in the small intestine via energy dependent transport carriers through a concentration gradient

Question 7

How can dietary overload of non-essential amino acids cause a deficiency in an essential amino acid?

Answer 7

Amino acid absorption transport systems are shared

one amino acid may have priority over another which then causes the deficiency

Question 8

Transamination vs. Deamination

Answer 8

Transamination
- reaction between an amine with an amino group and a keto acid with a keto group (amino acid becomes a keto acid and keto acid becomes amino acid)

Deamination
- causes the loss of the amine group from the amino acid which is replaced with a ketone

Question 9

Amino Acid Oxidation

Answer 9

enzymes remove the amino group, leaving a carbon skeleton which is then broken down into acetyl-CoA and pyruvate

Question 10

How does amino oxidation function with regard to neurotransmission?

Answer 10

• many amino acids play roles as neurotransmitters
• amino acid oxidation is one way (amino acids are converted into neurotransmitters)

Ex: oxidation of phynylalanine to form tyrosine

Question 11

How does the body dispose of excess ammnia? Where does this occur?

Answer 11

• the body turns ammonia into urea and excretes it in the urine
• urea is made in the liver and kidneys from ammonia produced in the mitochondria

Question 12

How are amino acids used for energy (where do they enter the energy production cycle)?

Answer 12

amino acids are broken down to Acetyl-CoA and pyruvate and then enter the krebs cycle

Question 13

Ketogenic vs. Glucogenic amino acids

Answer 13

Ketogenic amino acids (degraded into acetoacetate)

Glucogenic amino acids (degraded into precursurs to gluconeogenesis and may be formed into glucose)

Question 14

How does glutamine contribute to the synthesis of the nucleic acid bases?

Answer 14

Glutamine contributes to the synthesis of the nucleic acid bases because it is a precursor to the purine and pyrimidine nucleotide bases used in the synthesis of RNA and DNA

Question 15

major routes of nitrogen loss from the body

Answer 15

nitrogen is lost as ureo in urine when glutamate gets converted to glutamine

Question 16

Nitrogen balance

Answer 16

the amount of protein or nitrogen required by a human

• the body is in balance (amount taken in = amount excreted)
• the amount of nitrogen lost in urine, sweat, and feces is subtracted from the total amount taken in

Question 17

WHO protein recommendations

Answer 17

• they’re derived by taking the digestibility of the protein and multiplying it by the amount of protein a person of a specific age group is supposed to consume
• allows type of protein to be taken into account when finding the total mass of protein as a minimum the person must consume

Question 18

Potential complications from excess protein consumption

Answer 18

• deficiency in an essential amino acid
• renal stress
  increased incidence of colon cancer and obesity

Question 19

Kwashiorkor vs. Marasmus

Answer 19

Kwashiorkor - malnutrition causing the stomach to bloat (caused by insufficient protein intake with sufficient calorie intake)

Marasmus - inadequate energy intake in all forms (causes tissue and muscle wasting)

Question 20

20 major amino acids

Answer 20

Essential:
phynylalanine, tryptophan, valine, leucine, isoleucine, methionine, lysine, histidine, threonine

Non-Essential:
tyrosine, glycine, alanine, aspartate, glutamate, glutamine, asparagine, proline, arginine, serine, cysteine