Biochemistry Proteins and Enzymes Quiz

Study Notes

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).

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.

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

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.

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.

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.

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.

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.

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.

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.

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

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)

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

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.