Cell Cycle and Signaling Quiz

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Questions and Answers

What is the primary purpose of the cell cycle in developing organisms?

To produce new cells with a complete genome (correct)

To produce energy through respiration

To facilitate the exchange of gases

To enable movement in response to stimuli

Which of the following correctly lists the stages of interphase?

Cytokinesis, Mitosis, G1

Prophase, Anaphase, Telophase

G2, M Phase, Cytokinesis

G1, G2, S phase (correct)

During which phase of the cell cycle is DNA synthesized?

Growth 2 (G2)

Growth 1 (G1)

S phase (correct)

Mitosis (M Phase)

In adult multicellular organisms, how does the cell cycle primarily function?

To replace damaged or dying somatic cells Signup and view all the answers

Which step in interphase involves the production of VIP molecules?

Growth 1 (G1) Signup and view all the answers

What is the main role of the ligand in cell signaling?

To initiate cellular activity in response to an external signal Signup and view all the answers

What happens during the transduction step of cell signaling?

The signal is moved from the cell membrane to the nucleus through a series of proteins Signup and view all the answers

Why does Medicine X only bind to liver cells in the experiment?

Only liver cells have the specific receptor for Medicine X Signup and view all the answers

Which of the following is NOT a step in the cell signaling process?

Gene Expression Signup and view all the answers

What initiates the cellular response in the cell signaling pathway?

The phosphorylation of a protein Signup and view all the answers

Which mechanism involves a signaling molecule traveling to a nearby target cell?

Paracrine signaling Signup and view all the answers

In which step does the receptor undergo a conformational change?

Reception Signup and view all the answers

How can ligands travel long distances to reach target cells?

Through the bloodstream Signup and view all the answers

What type of ligands bind to receptors embedded in the cell membrane?

Hydrophilic ligands Signup and view all the answers

What is the primary function of transduction pathways in cell signaling?

To amplify the signal and initiate transcription of target genes Signup and view all the answers

Which component is typically activated as a second messenger in transduction pathways?

Cyclic AMP Signup and view all the answers

Where do lipid soluble ligands bind upon entering the cell?

To intracellular receptors Signup and view all the answers

How would a mutation in the DNA coding for insulin receptor protein likely affect glucose usage in target cells?

Glucose usage would decrease due to impaired receptor function. Signup and view all the answers

What effect do mutations in receptor molecules or signaling proteins typically have on cell responses?

They can lead to a change or complete stop in the cell response. Signup and view all the answers

What results from the successful activation of a transcription factor in the nucleus?

Genes are turned on to produce proteins Signup and view all the answers

What is likely to happen if enzyme 3 is inhibited?

Substrate B would accumulate in the cell. Signup and view all the answers

What is the role of a G protein in response to ligand binding to a G Protein Coupled Receptor (GPCR)?

It activates a second messenger Signup and view all the answers

Which of the following describes how Botox affects neurotransmitter release?

It breaks down SNARE proteins, preventing neurotransmitter release. Signup and view all the answers

What accumulates in the cell when enzyme 5 is inhibited?

Substrate D Signup and view all the answers

What is the primary role of negative feedback in physiological processes?

To slow down or stop a response and return to normal state. Signup and view all the answers

Which process occurs at the end of a signal transduction pathway?

Initiation of cell response, such as growth or apoptosis Signup and view all the answers

What triggers the phosphorylation of proteins in the transduction pathway?

Activation of a second messenger Signup and view all the answers

What is typically a characteristic of positive feedback mechanisms in physiological processes?

They increase biological processes until a specific endpoint is reached. Signup and view all the answers

What is the purpose of the cell cycle?

To grow and divide to form new cells. Signup and view all the answers

Which phase of the cell cycle are most cells usually in?

G-0 phase Signup and view all the answers

Which situation could decrease a cell’s response to ligands aside from mutations?

The presence of inhibitors targeting signaling pathways. Signup and view all the answers

What is one of the potential outcomes of receptor protein mutations?

Changes in the shape and function of the receptor. Signup and view all the answers

Which of the following statements about the cell cycle is FALSE?

Cells in G-0 phase never re-enter the cell cycle. Signup and view all the answers

What can influence how often cells divide?

Environmental signals and cues. Signup and view all the answers

What general effect do medicines and toxins have on signaling pathways?

They can activate or inhibit signaling pathways. Signup and view all the answers

Which part of the cell cycle has three subparts?

Interphase Signup and view all the answers

In which phase do cells prepare to divide?

Interphase Signup and view all the answers

What occurs during the S phase of the cell cycle?

DNA synthesis occurs Signup and view all the answers

Which of the following stages is NOT part of mitosis?

G2 phase Signup and view all the answers

What is the primary function of spindle fibers during metaphase?

To attach to chromosomes Signup and view all the answers

How is the division of the cytoplasm accomplished at the end of cell division?

By the pinching in of the cell membrane Signup and view all the answers

What role do Cyclins and Cyclin Dependent Kinases (CDKs) play in the cell cycle?

Control progression through the cell cycle Signup and view all the answers

During which stage of mitosis do chromosomes line up along the equatorial plate?

Metaphase Signup and view all the answers

What marks the end of telophase?

Nucleus reforms and DNA decondenses Signup and view all the answers

Study Notes

Cell Signaling

Cell signaling is a series of steps that allow cells to respond to signals from their environment.
Cells respond by initiating some sort of cellular activity (e.g., initiating the cell cycle).
Signaling usually involves the secretion of a ligand (chemical signal) by the initiating cell, that travels to the target cell.
Only cells with the correct receptor protein will react to the signal molecule.

Basics of Cell Signaling

Step 3: Response – the final molecule in the signal pathway activates target DNA in the nucleus.
This leads to protein production, which is the cell's response.

Bell Work – Ligand Identification

In the experiment, insulin (a protein) is the ligand.

Bell Work – Ligand Specificity

Medicine X binds to liver cells because only liver cells have the correct receptor protein for that specific molecule.

Cell to Cell Contact and Ligand Delivery Mechanisms

Cells can make physical contact to transmit signals and initiate cell responses.
This requires direct contact between signal and receptor proteins bound on the cell membrane of communicating cells.
Ligands can travel short distances (diffusion) or long distances (bloodstream).
Paracrine signaling involves communication between cells where a signaling molecule is released and moves to the target cell.

Membrane-Bound vs. Intracellular Receptors

Hydrophilic ligands bind to receptors embedded in the cell membrane; the ligand does not cross the membrane.
Signal amplification and movement from the membrane to the nucleus happen via a transduction pathway.
Lipid-soluble ligands diffuse across the membrane and bind to the receptor inside the cell.

Signal Transduction Basics

Membrane-bound receptors use transduction to move the signal from the membrane to the nucleus.
A ligand binding to a receptor causes a shape change, transmitting the signal into the cell.
This process involves activating a second messenger (e.g., cyclic AMP) that phosphorylates the next protein in the chain.
This continues until a transcription factor enters the nucleus and initiates the cell's response.

Cell Response to Signal Transduction

Transduction pathways initiate transcription of target genes, causing genes to turn on and make proteins.
These proteins cause the cell to respond appropriately to the signal.
Examples of cell responses include: causing the cell to grow and enter the cell cycle, stimulating cells to secrete molecules, and initiating cell death (apoptosis).

G Protein Coupled Receptors (GPCRs) as a Signaling Example

A ligand binds to the GPCR, causing it to activate the G protein.
The activated G protein activates the second messenger, initiating transduction and leading to the cell's response.

Bell Work – Mutation Effects

A mutation in the insulin receptor protein changes its shape, reducing the cell's ability to respond to insulin.
This disrupts glucose usage in target cells.
Other factors that reduce response to a ligand can include disrupted signaling molecules or receptor protein quantity.

Structure, Function, and Pathway Malfunction

Mutations that alter the shape and chemical affinity of signaling molecules, receptors or proteins in transduction can alter or stop the proper cell response.

Chemical Compounds and Pathway Interference

Many medicines and toxins work by activating or inhibiting signaling pathways (e.g., Botox).
Botox breaks down SNARE proteins required for neurotransmitter release, leading to muscle paralysis.

Feedback Mechanisms

Sensory pathways and responses help maintain homeostasis.
Two types:
- Negative feedback: slows down or stops a response.
- Positive feedback: amplifies or increases a response.
Body temperature regulation is an example of negative feedback.

Negative vs. Positive Feedback Mechanisms

Negative feedback regulates physiological processes by stopping a cellular response, returning the body to normal and establishing homeostasis.
Positive feedback produces large systemic changes to re-establish homeostasis. It involves initiating and amplifying biological processes.

Negative Feedback Practice

If enzyme 3 is inhibited, the concentration of intermediate B will increase because it cannot be converted to intermediate C..
If enzyme 5 is inhibited, the concentration of substrate D will increase because it cannot be converted to isoleucine.

Bell Work – Cell Cycle Importance

Organisms need to make more cells for growth and development.

Important Prerequisite Knowledge Alert – Cell Cycle

Most cells in an organism are in the G0 phase (quiescence), which is a fancy way of saying they are not actively going through the cell cycle.

Cell Cycle Overview

Cells alternate between interphase and mitosis (M phase) and cytokinesis (actual cell division).
Interphase has three sub-phases: G1 (growth), S (DNA synthesis/replication), G2 (growth).

Cell Cycle Timing

Cell division rates vary greatly between cell types.
Cell cycle duration varies among cells, depending on their type and functional status, but is typically ~24 hours with ~23/24 hrs in interphase & ~1/24 hour in mitosis.

Developing and Adult Organisms – Cell Cycle

Developing organisms use the cell cycle for growth, producing new cells with complete genomes.
Adult organisms use it for tissue repair, replacing damaged or dying somatic (body) cells.

Steps of the Cell Cycle

The phases of the cell cycle are Interphase (G1, S, G2), Mitosis (prophase, metaphase, anaphase, telophase) and cytokinesis.

Steps of Mitosis

Prophase: Nucleus dissolves, DNA condenses, chromosomes visible(spindle fibers form)
Metaphase: Spindle fibers attach to chromosomes, chromosomes align on equatorial plate.
Anaphase: Spindle fibers contract, moving one set of chromosomes to opposite poles.
Telophase: Nucleus reforms, DNA decondenses. Cell membrane starts pinching in. Cytokinesis (cytoplasm division) completes to form two identical daughter cells.

Mitosis IRL

Stages of mitosis observed in cells.
Cells in G0 (non-dividing cells) and in the process of mitosis, characterized by changes in DNA, mitochondria and microtubules.

How do cells know to move to the next step: Cell Cycle Regulation

Growth factors stimulate the production of checkpoint-specific cyclin proteins.
Cyclins bind to CDKs, initiating a phosphorylation cascade that moves the cell through the checkpoint and into the next phase.
Phase-specific cyclins are degraded to prevent improper signaling.

Cell Cycle Control Overview

Cells progress through the cell cycle by passing through checkpoints.
These checkpoints ensure DNA integrity.
Damaged or mutated cells become stalled, entering cell cycle arrest by production of inhibitors of cyclin proteins.

Repairable vs. Irreparable Damage/Mutation:

Repairable damage/mutations are fixed; the cell progresses through the cycle.
Irreparable damage/mutations lead to programmed cell death (apoptosis).

Cancer: A Disease of the Cell Cycle

Cancer involves uncontrolled cell growth (tumors).
Cancer cells have accumulated mutations in genes that regulate cell cycle progression.
These mutations prevent programmed cell death, allowing cancer cells to grow and divide uncontrollably.

Healthy Cell Division

Normal healthy cells divide into two identical cells.
Cells go through checkpoints during division. Apoptosis, programmed cell death is initiated by itself.

Cancer Development

Two or more mistakes in DNA sequences leading to cancer cells: mistakes in genes that code for replication and apoptosis checkpoints.

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Description

Test your knowledge on the cell cycle and the mechanisms of cell signaling. This quiz covers the stages of interphase, DNA synthesis, and the roles of ligands and receptors. Assess your understanding of cellular processes crucial for developing organisms.