Nitrogen Balance, Protein, and Related Metabolism

These flashcards cover key terms and concepts related to nitrogen balance, protein metabolism, and associated disorders as discussed in the lecture.

Positive nitrogen balance

Occurs when nitrogen intake exceeds nitrogen loss, leading to net protein synthesis.

Negative nitrogen balance

Occurs when protein breakdown exceeds synthesis, leading to muscle wasting and impaired healing.

RDA for protein

Reflects the need to maintain amino acid pools and ensure adequate tissue maintenance, rather than merely energy needs.

Plant-based diets protein needs

May require higher protein intake due to lower digestibility and incomplete amino acid profiles.

Importance of nitrogen beyond protein synthesis

Essential for creating nucleotides, heme, creatine, neurotransmitters, and is critical for metabolism.

Creatine in muscle cells

Stores high-energy phosphate which regenerates ATP quickly during short bursts of activity.

Creatinine as a kidney marker

Produced at a constant rate and excreted by kidneys; accumulation indicates renal dysfunction.

Selenium deficiency effects

Increases oxidative stress due to reduced selenoproteins which protect against reactive oxygen species (ROS).

Selenium and thyroid function

Required for enzymes that convert T4 into T3, the active hormone.

Role of glycine in heme synthesis

Combines with succinyl-CoA to form ALA, the first committed step in heme synthesis.

Disruption in porphyrin synthesis

Causes accumulation of porphyrin intermediates, leading to symptoms of porphyria.

Maple Syrup Urine Disease (MSUD)

Characterized by accumulation of branched-chain amino acids due to defective breakdown.

Risks of high homocysteine

Damages blood vessels, leading to increased risk of thrombosis and cardiovascular disease.

Photosensitivity due to porphyrins

Causes oxidative damage to skin upon exposure to light due to generation of ROS.

Harm of bilirubin accumulation

Leads to jaundice and potential neurological damage, particularly in infants.

Impact of phenylalanine buildup in PKU

Impairs brain development by competing with other amino acids, reducing neurotransmitter synthesis.

Treatment principle for PKU

Restrict phenylalanine intake early in life to prevent developmental issues.

Orotic acid accumulation in orotic aciduria

Due to a defect in pyrimidine synthesis, preventing conversion to UMP.

Implication of orotic aciduria in anemia

Impaired DNA synthesis affects rapidly dividing cells, leading to megaloblastic anemia.

Folate deficiency effects on DNA

Leads to reduced thymidine synthesis and incorporation of uracil into DNA, causing strand breaks.

Cancer risk associated with folate deficiency

Increased DNA instability and mutations due to strand breaks.