Nucleic Acids, Urine & Milk Analysis – Exam Review

A comprehensive set of flashcards covering nucleic acids, urine analysis, and milk chemistry/processing to aid exam preparation.

What are nucleic acids polymers of?

Individual nucleotide monomers.

What is the full name and main role of DNA?

Deoxyribonucleic acid; it stores genetic information.

What is the full name and main role of RNA?

Ribonucleic acid; it directs protein synthesis.

What two components make up a nucleoside?

A nitrogenous base and a pentose sugar.

Which nitrogenous bases are purines?

Adenine and Guanine.

Which nitrogenous bases are pyrimidines in DNA?

Cytosine and Thymine.

Which nitrogenous base replaces thymine in RNA?

Uracil.

What three parts form a nucleotide?

Nitrogenous base, sugar, and phosphate group.

Which bases pair together in DNA by hydrogen bonds?

Adenine with Thymine, and Cytosine with Guanine.

Which bases pair together in RNA?

Adenine with Uracil, and Cytosine with Guanine.

What bond links nucleotides in the primary structure of nucleic acids?

Phosphodiester bond.

Name the three common DNA conformations and their handedness.

B-DNA (right-handed), A-DNA (right-handed, short & wide), Z-DNA (left-handed, zig-zag).

Who captured the critical X-ray diffraction image "Photo 51"?

Rosalind Franklin.

List the three major steps of the central dogma.

Replication (DNA→DNA), Transcription (DNA→RNA), Translation (RNA→Protein).

Which qualitative test detects peptide bonds in nucleoproteins?

Biuret Test.

Normal urine should be what color and appearance?

Yellow and clear to translucent.

What is the normal specific gravity range of urine (24-h sample)?

1.016 – 1.022.

What is the normal urine pH range?

5.50 – 6.50.

Define polyuria and give one common cause.

Urine output > 2 L/day; seen in diabetes mellitus, diabetes insipidus, or chronic renal failure.

Define oliguria and give one cause.

Urine output < 400 mL/day; seen in acute glomerulonephritis, congestive heart failure, or dehydration.

Define anuria.

Urine output < 100 mL/day; indicates near-complete cessation of renal function.

What is isosthenuria and its typical SG value?

Fixed urine specific gravity around 1.010, typical of end-stage renal failure.

A sweet-smelling urine odor suggests which condition?

Diabetes mellitus (glucosuria).

Maple-syrup-like urine odor indicates which disease?

Maple syrup urine disease.

The Jaffe’s picric acid reaction identifies which substance and what positive result?

Creatinine; a red Janovski complex.

Which reagents and result indicate chlorides in urine?

Nitric acid + 5 % silver nitrate; curdy white precipitate.

Rothera’s nitroprusside test detects what and shows what color?

Ketone bodies; purple tinge.

Benedict’s test screens for what in urine and gives what positive sign?

Glucose; brick-red precipitate.

Heller’s ring test detects which protein and what is the positive observation?

Albumin; a white ring or fuzzy zone at the acid-urine interface.

Which test uses benzidine and H₂O₂ to detect blood in urine?

Benzidine test; positive if solution turns green to blue.

Gmelin’s test identifies what substance with a green/blue/violet ring?

Bile pigments.

Lettenkofer’s test confirms the presence of what in urine?

Bile salts (red ring after sucrose & conc. H₂SO₄).

Approx. what percentage of total protein in bovine milk is casein?

About 80 %.

What is the isoelectric point of casein?

pH 4.6.

Which enzyme breaks down lactose, deficiency of which causes lactose intolerance?

Lactase (β-galactosidase).

What is the major carbohydrate in milk and its sweetness level?

Lactose; it is the least sweet of the common sugars.

Give the Low-Temperature Long-Time and High-Temperature Short-Time pasteurization conditions.

LTLT: 63 °C for 30 min; HTST: 72 °C for 15 s.

What is the main purpose of homogenization of milk?

To break fat globules into tiny particles preventing cream separation.

What is the specific gravity range of normal milk?

1.027 – 1.035.

What proteins remain in whey after casein removal?

Whey proteins such as β-lactoglobulin, α-lactalbumin, serum albumin, and immunoglobulins.

Which vitamins in milk are fat-soluble?

Vitamins A, D, E, and K.

What positive result indicates Moore’s test for lactose in milk?

Yellowish-brown color with caramel odor (hot alkali reduction).

A violet ring after ferric chloride addition reveals which adulterant in milk?

Formaldehyde.

Goat milk is less allergenic because it contains lower amounts of which casein fraction?

αs1-casein.

How does ultrapasteurization differ from UHT pasteurization?

Both heat milk to 138 °C for 2 s, but UHT places milk in multi-layer boxes/cans for extended shelf life, whereas ultrapasteurization uses sterile conventional containers.