Cell Cycle, Cancer, and Cell Signaling

These flashcards cover key concepts related to the cell cycle, cancer, and cell signaling as discussed in lecture.

What are the stages of the eukaryotic cell cycle?

G1, S phase, G2, M phase

Why is cancer more common in older individuals compared to younger individuals?

more time to accumulate mutations

What triggers the major cell cycle checkpoints?

Nutrient availability, DNA damage, and correct chromosome alignment.

What is the role of cyclins in the cell cycle?

Cyclins regulate the cell cycle by activating cyclin-dependent kinases (CDKs).

What is MPF in the context of the cell cycle?

M-phase promoting factor: a complex of cyclin and CDK that triggers the M phase.

What happens during the S phase of the cell cycle?

DNA synthesis: replication of DNA.

What is the primary function of the p53 protein?

Most common mutates cancer gene: surveils genetic integrity and can pause the cell cycle in response to DNA damage.

How do cyclins affect CDKs?

Cyclins bind to CDKs, activating them to trigger events in the cell cycle.

What is the consequence of a failing checkpoint in the cell cycle?

If checkpoints fail, mutations can accumulate, increasing the risk of cancer.

What role do soluble factors play in the regulation of the cell cycle?

Soluble factors in the cytoplasm regulate the progression of the cell cycle stages.

How do chemical signals affect cell communication?

Chemical signals bind to specific receptors to convey messages inside the cell.

What are the three primary types of chemical messengers?

Peptide, steroid, and amine

What is the result of altering a stage in the cell cycle?

affect on cell structure and function

Describe the structure of peptide messengers.

hydrophilic: cannot pass through cell membrane easily

How are steroid hormones transported in the bloodstream?

Hydrophobic: attach to membrane-bound proteins

What is a checkpoint in the cell cycle?

A control mechanism that ensures processes are completed correctly before proceeding.

What happens during the G1 phase of the cell cycle?

Cell growth occurs, and the cell prepares for DNA synthesis.

What defines the M checkpoint in cell division?

Checks for aligning of chromosomes on metaphase plate

How do cyclins become regulated during the cell cycle?

Cyclin levels oscillate throughout the cycle, leading to CDK activation at specific times.

Why is transcription not possible during mitosis?

Chromosomes are condensed

What happens to cells if p53 is mutated?

Increased of tumor formation due to lack of DNA damage surveillance.

Explain the concept of mismatch repair in DNA replication.

correction of errors that occur during DNA synthesis.

What do you infer if cyclins are continuously produced?

Cyclins are necessary for cell cycle progression and M phase

What is the effect of phosphorylation in the cell cycle?

modifies protein function rapidly which causes quick responses in cell cycle regulation.

Why is the cell cycle highly conserved across eukaryotes?

Key regulatory mechanisms have remained largely unchanged throughout evolution.

What does the term 'ligand' refer to in cell signaling?

a chemical signal that binds to a receptor to transmit a message.

Which phase of the cell cycle involves DNA damage checks?

G2 phase

What is the relationship between a chemical messenger and its receptor?

Only certain cells with specific receptors can respond to particular signaling molecules.

What happens if you fuse cells at different stages of the cell cycle?

Nucleus of cell that is behind in cycle will skip to step that nucleus of other cell is in

Can we transcribe new genes during replication?

No

How do we regulate processes when new transcription isn’t possible?

1. Degrade transcripts and proteins

2. Transcribe sequences needed for new genes

3. Phosphorylate/dephosphorylate proteins that are only active in a phosphorylated state

When does CDK begin to phosphorylate other proteins?

When enough cyclin is present

What are the MPF phosphorylation targets?

1. Condensins: chromosomes condense

2. Lamins: nucleus breaks down

3. Golgi matrix protein 1: golgi and ER fragment

What do MPF phosphorylation targets trigger?

M phase

How do cyclins eventually break down?

Phosphorylation of the targets causes cyclin to be degraded over time (feedback loop)

What does the degradation of cyclin cause?

Cell exits M phase

What is important about phosphorylation?

1. Fast

2. Doesn’t depend on transcription

3. Drives cell cycle by activating MPF complex

What are model organisms?

Organisms picked as models depending on how closely their biological processes relate to the processes of the organism you want to study

What happens if a mismatch mutation is not recognized and corrected before the next round of DNA replication?

Mutation becomes irreversible: it is replicated and passed onto daughter cell

Should mutations be corrected before or after DNA replication?

Before

What happens at G1 checkpoint?

Check for nutrients, check for adequate growth, cell signals for division, and DNA damage

What happens at G2 checkpoint?

Check for proper DNA replication and damage

What happens when checkpoints are triggered?

Cells pause and repair

What happens if microtubules get cut?

Chromosomes remain stuck in metaphase, lined up in middle of cell

What happens if checkpoints aren’t triggered?

Mutation

What does a nonfunctional p53 protein cause?

Formation of cancer cells

What must happen in order to become a cancer cell?

1. Lose ability to listen to signals

2. Lose ability to fix mutations

What needs to happen for a receptor to react to a ligand?

Specific ligand must find specific receptor

What happens when a ligand binds to a receptor?

Receptor shape changes

What chemical messengers are lipid-soluble?

Amines and steroids (ring): hydrophobic

What chemical messengers are not lipid soluble?

Amines and peptides (protein): hydrophilic

What do lipid-soluble messengers bind to?

DNA inside of nucleus (intracellular): transcription factor receptors

What do not lipid soluble messengers bind to?

Surface of cell membrane: transmembrane protein receptors —> cause phosphorylation

What is signal transduction?

Passing of info that not-lipid soluble ligand is bound to receptor: convert one signal into another

How is phosphorylation a switch?

Activates or deactivates

How do hormones and other chemical messengers present in very low concentrations have an enormous impact?

Signal amplification: small amounts of signal amplified at a time to cause large response

What is a phosphorylation cascade?

Chain reaction that amplifies signal from a chemical message

How does a phosphorylation cascade occur?

Each kinase in a signaling network phosphorylates multiple target proteins, target proteins go on to phosphorylate more proteins, and so on

What is a second messenger

Intracellular signal: ion or small molecule that is released when non-lipid soluble messengers bind to cell-surface receptors

What is cancer?

Uncontrolled cell division

Benign tumor

Rapid growth that disrupts normal cell function at tumor site

Malignant tumor

Metastasis: rapid growth that disrupts normal cell function at new sites

What happens in G2 phase of cell cycle?

growth, error-checking of DNA replication and prep for mitosis

What happens if cells don’t receive signal to keep growing in G1 phase?

G0: long-term non-diving phase

Role of genotype in cancer development

Some people are born with cancer predisposition (mutations of p53, BRCA1 and BRCA2)

Role of environment in cancer development

Somatic cells’ DNA damaged by chemicals

Role of age in cancer development

Older = higher chance of cancer

Which phase of the cell cycle contains replicated chromosomes?

S phase, G2 phase, and M phase