Cell Biology Quiz: Apoptosis and Cell Cycle

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Questions and Answers

What is one function of BCL-2 family proteins in relation to apoptosis?

They promote necrosis.

They trigger inflammation.

They cause ATP depletion.

They inhibit apoptosis. (correct)

Which mechanism distinguishes apoptosis from necrosis?

Causes cell swelling and rupture.

Involves membrane blebbing. (correct)

Always results in inflammation.

Requires external factors for cell death.

What is the primary consequence of necrosis?

It creates apoptotic bodies.

It maintains cell balance.

It generally leads to inflammation. (correct)

It allows for energy-efficient cell replication.

What role do Inhibitors of Apoptosis Proteins (IAPs) play regarding caspases?

They block various caspases. Signup and view all the answers

Which of the following accurately describes apoptosis?

It is a programmed and controlled process. Signup and view all the answers

What is a characteristic of cancer cells in relation to cellular transformation?

They have unlimited cell division potential. Signup and view all the answers

Which of the following processes requires ATP for execution?

Apoptosis Signup and view all the answers

Which of the following is NOT a feature of necrosis?

Formation of apoptotic bodies. Signup and view all the answers

What role do RB proteins play in cell cycle progression?

They activate genes required for S-phase entry. Signup and view all the answers

Which protein is responsible for phosphorylating the ATP binding site of CDKs to inhibit their activity?

WEE1 Signup and view all the answers

How does p53 contribute to cell cycle regulation under stress conditions?

By activating CDK inhibitors. Signup and view all the answers

What is the significance of the restriction point in the cell cycle?

It allows cells to become independent of mitogenic signaling. Signup and view all the answers

What is one consequence of loss-of-function mutations in WEE1?

Enhanced CDK activation. Signup and view all the answers

Which CDK inhibitors specifically target CDK4 and CDK6 without affecting other CDKs?

p15 and p19 Signup and view all the answers

In cancer biology, what is a common result of R-point deregulation?

Uncontrolled progression of the cell cycle. Signup and view all the answers

What additional role does mitogenic signaling play in normal physiological cell proliferation?

It provides survival signals to counteract p53 responses. Signup and view all the answers

What is the primary role of the CDK1-cyclin B complex during the cell cycle?

It drives the transition from G2 to M phase. Signup and view all the answers

Which of the following accurately describes the relationship between mitogens and D-type cyclins?

Mitogens stabilize D-type cyclins by activating CDK4/6. Signup and view all the answers

What happens at the R-point in the cell cycle?

Cells commit to the cell cycle and no longer require mitogenic signals. Signup and view all the answers

Which protein family acts as transcriptional repressors by sequestering E2F transcription factors?

Retinoblastoma (RB) family proteins Signup and view all the answers

How do cyclins contribute to the regulation of the cell cycle?

They degrade through hydrolysis unless stabilized by mitogenic signals. Signup and view all the answers

What is the effect of mitogens on the cell cycle?

They stimulate signaling pathways that promote cell growth and division. Signup and view all the answers

What initiates the signaling pathway associated with mitogens?

Binding to surface receptors with tyrosine kinase activity. Signup and view all the answers

Which cellular phase do most adult cells reside in when not actively dividing?

G0 phase Signup and view all the answers

What is a key feature of cancer related to the cell cycle?

Deregulated cell cycle commitment Signup and view all the answers

What typically allows cancer cells to bypass the dependency on mitogens?

Mutations in the Ras signalling pathway Signup and view all the answers

What is one of the mechanisms by which cancer cells achieve independence from mitogens?

Overproduction of growth factor ligands Signup and view all the answers

Why do normal cells exhibit limited proliferative capacity?

Shortening of telomeres with each division Signup and view all the answers

What role does telomerase play in cancer cells?

Adds nucleotides to telomeres Signup and view all the answers

What happens to telomeres in normal cells with each division?

They shorten Signup and view all the answers

What is a consequence of dysfunction in telomere maintenance due to absence of telomerase?

Continued cell division despite shortening Signup and view all the answers

What cellular mechanism attempts to repair critically short telomeres without telomerase?

End-to-end fusion of chromosomes Signup and view all the answers

What is the primary effect of telomerase reactivation in cancer cells?

Stabilizes scrambled chromosomes Signup and view all the answers

How does metaplasia differ from dysplasia?

Metaplasia involves changes in cell type, while dysplasia involves disorganized growth. Signup and view all the answers

What cellular process is characterized by a cell transforming into a more specialized type?

Cellular differentiation Signup and view all the answers

What is the consequence of mutations in the TERT promoter?

Loss of negative regulation of TERT expression Signup and view all the answers

Which of the following is NOT a characteristic of metaplasia?

It is always a pre-cancerous change. Signup and view all the answers

What does dysplasia indicate with respect to cell growth?

Abnormal growth or development of cells Signup and view all the answers

In which condition is squamous metaplasia most commonly observed?

Smokers’ lungs Signup and view all the answers

Which statement accurately describes telomerase in relation to cancer?

It can stabilize genomes and promote tumorigenic phenotypes. Signup and view all the answers

What defines metaplasia?

Replacement of one differentiated cell type with another Signup and view all the answers

Which condition is an example of metaplasia?

Barrett's oesophagus Signup and view all the answers

What is the main difference between metaplasia and dysplasia?

Metaplasia involves normal cells, dysplasia involves abnormal cells. Signup and view all the answers

Which of the following factors is considered a common cause of metaplasia?

Chronic irritation or environmental stress Signup and view all the answers

Which aspect of dysplasia makes it a pre-cancerous condition?

Presence of abnormal cells with disordered growth Signup and view all the answers

What percentage of people with Barrett's oesophagus are likely to develop oesophageal adenocarcinoma?

3—13% Signup and view all the answers

What cellular feature is characteristic of metaplasia?

Normal cells in an unfavorable environment Signup and view all the answers

Which statement best explains the reversibility of metaplasia?

It can revert to normal if the stimulus is removed. Signup and view all the answers

Study Notes

The Cell Cycle

The cell cycle describes the phases of cell division
G1 phase (Gap 1): Interval between mitosis and DNA synthesis; cells commit to division at a restriction point, influenced by growth signals; cells may arrest due to insufficient conditions or inhibitory signals.
S phase (Synthesis): DNA replication occurs, doubling the genetic material from 2n to 4n (diploid to tetraploid).
G2 phase (Gap 2): The interval between DNA synthesis and mitosis; error correction occurs to prevent replication errors; spindle assembly begins.
M phase (Mitosis): Cell division into two identical daughter cells; includes nuclear envelope breakdown, chromosome condensation and alignment, mitotic spindle assembly, Golgi and nucleolus disassembly, and cell rounding.
Mitogens trigger cell cycle progression through signalling pathways involving receptors, Ras proteins, and D-type cyclins.
Cyclins and Cyclin-dependent kinases (CDKs) regulate cell cycle progression.
Inhibitory factors control the cell cycle, prevent uncontrolled progression, and ensure precise timing of events (e.g., p21, p27).
R-point (restriction point): A critical point in G1 where cells commit to the cell cycle, independent of mitogens.
Telomere shortening limits cell division in normal cells.

Cellular Transformation

Cellular transformation involves the transition of normal cells to a tumorigenic state, including changes in morphology and function.
Cancer cells often bypass the need for mitogens to divide.
They may exhibit uncontrolled proliferation due to defects in checkpoints.
Telomerase activation in cancer cells prevents the shortening of telomeres, allowing unlimited cell division.

Apoptosis

Apoptosis (programmed cell death) is a regulated process removing damaged or unnecessary cells.
It involves cellular components being recycled through phagocytosis, and does not trigger inflammation.
Factors promoting apoptosis include proteolytic caspases, TNF receptor superfamily members (e.g., TNF-a, FasL), and p53.
Inhibitors of apoptosis include BCL-2 family proteins and IAPs.
Necrosis is an uncontrolled cell death, characterized by cell swelling, membrane damage, and inflammation.

Cellular Differentiation and Metaplasia

Cellular differentiation is the process where cells change into a specialized type during development.
Metaplasia is the replacement of one fully differentiated cell type by another.
Dysplasia describes abnormal cellular growth and maturity, often linked to pre-cancerous conditions.

Barrett's Oesophagus

Barrett's esophagus involves the replacement of normal squamous epithelial cells in the esophagus with abnormal columnar epithelial cells.
It's a pre-cancerous condition and linked to chronic acid reflux and an increased risk of esophageal adenocarcinoma.

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Description

Test your knowledge on the mechanisms of apoptosis and cell cycle regulation. This quiz covers key concepts such as the role of BCL-2 proteins, apoptosis vs. necrosis, and the function of CDKs and their inhibitors. Perfect for students studying cell biology or cancer biology.