Cell biology worksheet with answers

When human muscle cells lack oxygen, pyruvate is converted into:

1. AEthanol
2. BAcetyl-CoA
3. CGlucose
4. DLactate

Which molecule brings amino acids to the ribosome during translation?

1. ADNA polymerase
2. BTransfer RNA (tRNA)
3. CMessenger RNA (mRNA)
4. DRibosomal RNA (rRNA)

What happens to a red blood cell placed in pure water?

1. AIt stays the same size
2. BIt swells and may burst
3. CIt shrinks and shrivels
4. DIt divides into two cells

What are aquaporins?

1. AEnzymes that split water into hydrogen and oxygen in membranes
2. BChannel proteins that let water cross membranes quickly
3. CReceptors for water-soluble hormones
4. DPumps that move sodium out of cells

Which cell junction lets ions and small molecules pass directly between neighbouring cells?

1. AAdherens junction
2. BGap junction
3. CTight junction
4. DDesmosome

Which cell junction seals neighbouring epithelial cells together and stops fluid leaking between them?

1. ATight junction
2. BHemidesmosome
3. CDesmosome
4. DGap junction

In the Meselson–Stahl experiment, bacteria grown in ¹⁵N were moved to ¹⁴N. After one round of replication all DNA formed one band of intermediate density. Which model did this rule out?

1. ABoth semi-conservative and dispersive models
2. BThe conservative model
3. CThe semi-conservative model
4. DThe dispersive model

Knudson's "two-hit" hypothesis, based on retinoblastoma, explains that tumour suppressor genes:

1. AUsually need both alleles to be inactivated before a tumour develops
2. BAre always inherited in mutated form from both the mother and the father
3. CCause cancer when one allele is overactive
4. DAre only found in children