Unit 4 Extra Credit Cell Cycle

What is the primary reason cells divide in unicellular organisms?

Asexual reproduction

What are three reasons cells divide in multicellular organisms?

Growth and development, repair damaged tissue, replace dead cells

What is the Cell Cycle?

The series of events that occur between cell divisions.

What is the longest phase of the Cell Cycle?

Interphase

What occurs during the G1 phase of Interphase?

Growth, making more organelles, and metabolic activity.

What is the G1/S Checkpoint?

It checks if the cell is ready to divide, assessing DNA integrity, cell size, space, growth factors, and resources.

What is the significance of the G0 phase?

It is a resting phase where non-proliferative cells, like many nerve and muscle cells, remain until proper signals prompt them to divide.

What happens during the S phase of Interphase?

DNA replication occurs, and the cell becomes committed to division.

What is synthesized during the G2 phase of Interphase?

Proteins needed for mitosis and a large amount of ATP.

What is the G2/M Checkpoint?

It checks if the DNA is okay and if replication is complete before mitosis.

What is Mitosis?

Nuclear division that results in two identical nuclei.

What occurs during Prophase?

The nucleolus and nuclear membrane disappear, chromatin condenses, and centrosomes move to opposite poles.

What is the difference between a chromosome and a replicated chromosome?

A chromosome has one chromatid; a replicated chromosome has two identical sister chromatids.

What is the role of the centromere?

It links sister chromatids together and contains kinetochore proteins for spindle fiber attachment.

What happens during Metaphase?

Spindle fibers align chromosomes at the equator of the cell.

What occurs during Anaphase?

Sister chromatids are separated and pulled to opposite poles of the cell.

What happens during Telophase?

The spindle disappears, chromosomes unwind, and the nucleolus and nuclear membrane reform.

What is Cytokinesis?

The division of the cytoplasm, resulting in two daughter cells.

How do cytokinesis differ in animal and plant cells?

Animal cells form a cleavage furrow; plant cells form a cell plate.

What are cyclins and cyclin-dependent kinases (CDKs)?

Positive regulators of the cell cycle that advance the cell cycle.

What role do mitogens play in the cell cycle?

They are growth factors that promote cell division.

What is the function of tumor suppressors?

They inhibit cyclin/CDK pairs, stopping the cell cycle.

What is p53 known as?

The 'Guardian of the Genome' and an important tumor suppressor.

What characterizes cancerous cells?

Uncontrolled cell division often due to mutations in regulators.

What are some hallmarks of cancerous cells?

Sustaining proliferative signaling, evading growth suppressors, resisting cell death, activating invasion and metastasis, inducing angiogenesis, enabling replicative immortality.

What is a main form of cell communication?

Chemical signaling

What are ligands?

Chemicals that interact with specific receptor proteins on the cell surface or in the cell.

What type of receptors do small, hydrophobic ligands interact with?

Internal (cytoplasmic) receptors

How do water-soluble ligands communicate with cells?

They interact with external (cell membrane) receptors and cannot diffuse directly through the membrane.

What are the four types of cell communication?

Juxtacrine, Autocrine, Paracrine, Endocrine signaling

What is Juxtacrine signaling?

Cell-to-cell signaling through direct contact.

What is Autocrine signaling?

A cell produces the ligand for its own receptor.

What is Paracrine signaling?

Ligands are received by nearby cells.

What is Endocrine signaling?

Ligands travel through the bloodstream.

What are the three main steps in cellular communication?

Reception, Transduction, Response

What occurs during the Reception step of cell communication?

The ligand interacts with its specific receptor.

What happens during the Transduction step?

The signal is converted to an intracellular message.

What is the Response step in cell communication?

A change occurs within the cell.

What types of receptors do small, hydrophobic ligands use?

Internal receptors located in the cytoplasm or nucleus.

What is the function of enzyme-linked protein receptors?

Ligand activation initiates signal transduction.

How do ion-channel linked receptors function?

Ligand binding opens a channel through a conformational change.

What role do G protein-coupled receptors play?

Ligand binding activates the G protein attached to the receptor.

What is phosphorylation in the context of signal transduction?

The addition of phosphates from ATP to another protein, activating relay proteins.

What are second messengers?

Molecules that relay and amplify the signal within the cell.

Give an example of a second messenger.

Cyclic AMP (cAMP)

What is the role of feedback in cellular communication?

Feedback can stimulate or inhibit the signal that produced it.

What is a negative feedback loop?

A response that stops the signal and returns to a baseline or set level.

What is a positive feedback loop?

A response that amplifies the signal until the process is complete.

What is an example of positive feedback?

Fruit ripening or blood clotting.