Cell biology worksheet with answers

The cell membrane is mainly made of:

1. AStarch
2. BA phospholipid bilayer with proteins
3. CDNA
4. DCellulose

Which base is found in RNA instead of thymine?

1. AAdenine
2. BCytosine
3. CGuanine
4. DUracil

What is cytokinesis?

1. AThe division of the cytoplasm into two daughter cells
2. BThe breakdown of the nuclear envelope
3. CThe pairing of homologous chromosomes
4. DThe copying of DNA before division

Cyclin-dependent kinases (CDKs) that drive the cell cycle become active when they bind to:

1. AHistones
2. BTubulins
3. CRibosomes
4. DCyclins

How do steroid hormones such as cortisol mainly act on their target cells?

1. AThey activate adenylyl cyclase from outside the cell
2. BThey bind a membrane receptor and open ion channels, changing the cell's membrane potential
3. CThey are taken up by phagocytosis and digested
4. DThey cross the membrane and bind intracellular receptors that change gene transcription

A competitive inhibitor binds the active site of an enzyme. What can overcome its effect?

1. ARaising the inhibitor concentration
2. BLowering the temperature to 0 °C
3. CRemoving the enzyme's cofactor
4. DRaising the substrate concentration

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

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

Non-disjunction during meiosis can result in:

1. AIdentical twins
2. BMitochondrial DNA mutations only, which are passed on through the egg cytoplasm
3. CCrossing over
4. DGametes with an abnormal number of chromosomes, such as in Down syndrome