Biology flashcards wrong questions

If two structures are 200 nm apart, what is the actual distance when magnification changes from ×40 to ×400?

200 nm.The actual distance does not change with magnification. Magnification only affects what you see.

Which structures contain cisternae?

Endoplasmic reticulum and Golgi body.Cisternae are membrane sacs found in the ER and Golgi, not in chloroplasts or mitochondria.

Which structures are found in both eukaryotic and bacterial cells?

Cell membrane, cell wall, cytoplasm Bacteria do not have nuclei or mitochondria (no membrane-bound organelles).

What type of bond holds collagen triple helices together?

Covalent bond.These are strong cross-links between helices — not hydrogen, peptide, or disulfide bonds.

Why is cysteine important in β-globin?

It affects oxygen affinity and the Bohr shift. Replacing it reduces the Bohr effect, showing it's key to hemoglobin function.

What does a triglyceride yield on hydrolysis?

Fatty acids and glycerol.

No amino acids here — it's a lipid, not a protein.

Why did glucose diffuse out of Visking tubing but starch didn’t?

A: Glucose is small enough to pass; starch is too big.

Only glucose caused a color change in Benedict’s test. Water movement isn’t shown.

What does a non-competitive inhibitor do to enzyme rate?

A: Lowers the maximum rate (Vmax).

It binds elsewhere and affects enzyme shape, reducing efficiency even if substrate is added.

Q: How does allopurinol reduce uric acid formation?

A: It binds to the active site of xanthine oxidase.

Explanation: It mimics hypoxanthine and acts as a competitive inhibitor.

Which statements about phospholipids in membranes are true?

Hydrophobic tails face inward, phospholipids provide flexibility. Explanation: Tails don’t allow ions through; polar heads face both sides, not just cytoplasm

What is the SA:Vol ratio of a 2 µm long, 0.5 µm wide bacterium?

A: 9.0 : 1.0

Explanation: Calculated using cylinder formulae. Small cells have high SA:Vol ratios.

Q: How many DNA molecules are in a chicken cell at prophase?

A: 156.

Explanation: Each of the 78 chromosomes has two chromatids (DNA copies) after replication.

What happens next in metaphase?

A: Chromosomes are aligned; next, chromatids are pulled apart (anaphase).

Explanation: Cell X was in metaphase → the next step is C: chromatids move to poles.

Which processes happen in bone marrow cells during mitosis?

A: ATP synthesis, DNA replication, translation.

Explanation: All three are active processes in dividing cells.

Concept: Differences between prokaryotic and animal cells

Why C is correct: Only animal cells have lysosomes. Both produce ATP, but in prokaryotes, it's in the cell membrane; in animal cells, it's in mitochondria. C correctly shows no lysosomes in prokaryotes and ATP production in both.

Concept: Peptide bond formation during protein synthesis.

Why D is correct: Statement 3 is correct: peptide bonds form via condensation (not hydrolysis) and remove a water molecule. Statement 1 is false — the bond forms while amino acids are still attached to tRNA. Statement 2 is incorrect due to the "hydrolysis" part.

Concept: Biological molecule tests.

Solution 2: Became red after acid hydrolysis, indicating sucrose (non-reducing sugar).

Solution 3: Biuret test positive (blue to purple), indicating amylase, a protein.

Solution 1: Glucose (reducing sugar), not relevant to the question.

Concept: Competitive enzyme inhibition.

Why A is correct: Competitive inhibitors don't affect Vmax, but they increase Km because more substrate is needed to achieve the same rate (they compete with the substrate).

Concept: Substrate affinity (inverse of Km).

Why B is correct: The enzyme that reaches half Vmax at the lowest substrate concentration has the highest affinity. Order is X → Z → Y.

Concept: Properties of molecules and active transport.

Why D is correct: A polar molecule that’s affected by ATP implies active transport. But if the ATP concentration has no effect, the molecule is not using active transport, likely diffusing passively.

Surface area-to-volume ratio (SA:V).

Why C is correct: Smaller blocks have larger SA:V, so they diffuse substances faster and turn yellow more quickly. Correct ratios and times

Spindle fibre changes during mitosis.

Why D is correct: Centromeres detach during anaphase, which corresponds to a rapid increase in spindle fibre length—seen at region D.

Codons and anticodons.

Why B is correct:

ACU, ACC, ACA, ACG → threonine.

Anticodons for those are UGA, UGG, UGU, UGC.

ACC is a codon, not an anticodon. Only UCA and ACC are listed as answers in B — and ACC is invalid, so B is correct as it includes ACC in error detection.

mRNA processing in eukaryotes.

Why B is correct: During RNA splicing, introns (non-coding) are removed and exons (coding sequences) are joined to form mature mRNA.

Concept: Plant vascular tissue structure.

Cell 1 is companion cell (smaller, with dense cytoplasm and nucleus).

Cell 2 is phloem sieve tube element (no nucleus, large).

Symplast pathway.

Why A is correct: Movement is cytoplasmic via plasmodesmata, but entry into symplast is controlled by cell membrane, making A correct.

Concept: Water movement in xylem.

Why B is correct: Water's cohesion (H-bonding between molecules) forms a continuous column, allowing transpiration pull.

Concept: Heart anatomy.

Why B is correct: The atrioventricular node (AVN) is in the lower right atrium, near the septum—location B in the diagram.

What happens when ventricular pressure exceeds atrial pressure?

A: Atrioventricular valves close.

What is present in tissue

A: Phagocytes, some proteins, and sodium ions