Biochemistry Proteins and Enzymes Quiz

BAPNA (N-Benzoyl-DL-arginine-p-nitroanilide)

• BAPNA is a synthetic substrate used to measure the activity of proteolytic enzymes.
• Proteases, like trypsin, cleave BAPNA, releasing p-nitroaniline, a yellow color.
• The intensity of the yellow color indicates the level of proteolysis (enzyme activity).

Factors that Denature Proteins

• Heat: High temperatures disrupt protein structures.
• pH Changes: Extreme acid or alkaline conditions cause proteins to lose their natural structure.
• Alcohol: Alters protein folding by breaking hydrogen bonds.
• Heavy Metals: Ions like mercury or lead bind to proteins, disrupting their structure.
• Mechanical Agitation: Stirring or shaking can cause proteins to denature.

Whipped Cream After Lipase Hydrolysis

• Texture Change: Lipase hydrolysis converts whipped cream into a watery substance, breaking down fats into glycerol and fatty acids.

Release of Fatty Acids (Rancid Taste)

• Rancid Taste: Lipase breaks down triglycerides, releasing fatty acids.
• These fatty acids cause the rancid taste, due to incomplete oxidation of fats in the cream.

TNP (Tri-nitrophenol)

• Structure: A highly acidic phenol with three nitro groups attached to the benzene ring.
• Identification: Used to detect certain compounds, especially reducing agents.
• Positive Result: Often observed in reactions involving reducing sugars or other phenolic compounds.

Uric Acid

• Structure: A purine derivative (C₅H₄N₄O₃) that crystallizes as yellowish-brown crystals.
• Identification: High uric acid levels in urine are linked to gout.
• Test: The Murexide test produces a bluish-violet color, indicating uric acid or its derivatives.

Creatinine

• Structure: A nitrogenous waste product (C₄H₇N₃O) from muscle metabolism.
• Identification: Creatinine levels in urine indicate kidney function.
• Test: Healthy individuals excrete creatinine consistently at a rate of approximately 1.2-1.7 g/hour.

Indican

• Structure: A breakdown product of tryptophan in the intestines, related to intestinal putrefaction.
• Identification: Obermeyer's test, with a greenish-blue result, indicates indican's presence.

Pathological Constituents

• Proteins: Proteinuria (proteins in urine) suggests kidney damage, like nephritis or kidney failure.
• Glucose: Glycosuria (glucose in urine) is linked to diabetes mellitus or excessive carbohydrate intake.
• Ketone Bodies: Produced during fat metabolism, often seen in diabetes, starvation, or increased fat oxidation.
• Bence-Jones Proteins: Indicates multiple myeloma or other blood plasma disorders. These proteins precipitate at low temperatures and dissolve at high temperatures.

Indicators of Liver Problems

• Bilirubin: Elevated levels in urine may indicate liver disease (like jaundice).
• Urobilinogen: A change in urobilinogen levels in urine can indicate liver dysfunction or hemolytic disease.

Key Indicators for Diabetes

• Bence-Jones Proteins: May be present in urine, suggesting possible multiple myeloma.
• Ketone Bodies: Indicate ketoacidosis, a severe condition of uncontrolled diabetes.

Urea

• Urea: A nitrogenous waste product from protein metabolism, excreted in urine.
• Formula: CO(NH₂)₂
• Structure: A carbonyl group (C=O) attached to two amine groups (NH₂).

Dipstick Test

• pH: (4.5 to 8.2)
• Glucose: (positive result = diabetes or high sugar intake)
• Proteins: (positive result = kidney damage)
• Ketones: (positive result = diabetes, starvation, or other metabolic disturbances)

Microscopic Urine Examination

• Used to identify cells, bacteria, and crystals in urine.
• Helps diagnose conditions like urinary tract infections (UTIs) or kidney stones.

Situational Problems

• Interpret abnormal test results based on known conditions.
• Examples
  • High glucose and ketones in urine: Could suggest diabetic ketoacidosis
  • Proteinuria in a patient with high blood pressure: Could suggest kidney damage or nephropathy.

Additional Tests

• Fehling's Test: Used for reducing sugars (e.g., maltose).
• Nitric Acid Test: Used for protein and to detect kidney issues or albuminuria.

Test your knowledge on the biochemical properties of proteins and enzymes, including the effects of various factors that denature proteins and the role of substrates like BAPNA. Explore how lipase affects whipped cream and the biochemical basis of rancidity in fats.