AP Bio: Cell Communication & Cycle

What are the different methods of cell communication and how do they compare?

Direct contact involves cells physically touching, local signaling uses chemical signals to affect nearby cells, and long-distance signaling involves hormones traveling through the bloodstream or vascular tissue.

What are examples of the different methods of cell communication?

Direct contact: immune cell interactions

How do gap junctions and plasmodesmata contribute to cell communication?

Gap junctions in animal cells and plasmodesmata in plant cells create direct cytoplasmic connections that allow ions, molecules, and signals to pass between adjacent cells.

What are the three stages of a signal transduction pathway?

The three stages are reception (a ligand binds to a receptor), transduction (signal is relayed and amplified via secondary messengers and protein modifications), and response (the cell carries out a specific action).

What is a ligand?

A ligand is a molecule that binds specifically to a receptor to trigger a signal transduction pathway.

What is the importance of secondary messengers in signal transduction pathways and give an example?

Secondary messengers amplify and relay signals inside the cell

What are the roles of protein kinases and phosphatases in signal transduction pathways?

Protein kinases add phosphate groups to proteins to activate or deactivate them, while phosphatases remove phosphate groups to reverse the process.

What are the various cellular responses of signal transduction pathways, including ligand-gated ion channels?

Cellular responses include changes in gene expression, enzyme activity, or ion flow through ligand-gated ion channels, leading to specific cell behaviors.

What role does the environment play in signal transduction pathways?

Environmental signals, such as light, temperature, or chemical cues, can trigger or modulate signal transduction pathways to alter cellular responses.

What effects can signal transduction pathways have on gene expression?

They can activate or repress transcription of specific genes, affecting protein production and cell behavior.

What is apoptosis and what is its role in signal transduction pathways?

Apoptosis is programmed cell death, and signal transduction pathways can initiate apoptosis to remove damaged or unnecessary cells.

How does a change in the receptor protein or other molecules in the signal transduction pathway alter the cellular response?

Mutations or modifications can change the pathway’s sensitivity, timing, or type of response, leading to altered cellular behavior.

What is the consequence when some molecules activate a signal transduction pathway?

Activation molecules can trigger downstream responses, such as changes in metabolism, gene expression, or ion flow, even in the absence of the normal signal.

What happens when molecules interfere with a signal transduction pathway?

Interfering molecules can block or misregulate the pathway, leading to inappropriate cellular responses, disease, or cell death.

What is the difference between positive and negative feedback?

Positive feedback amplifies a change or response, while negative feedback reduces a change to maintain stability.

What are examples of positive and negative feedback in animals and plants?

Positive feedback: childbirth contractions, fruit ripening

How can visual representations and disruptions of feedback mechanisms be analyzed?

Graphs or diagrams can show how feedback maintains or fails to maintain equilibrium, and disruptions can indicate over- or under-correction of a process.

What is homeostasis and which feedback mechanism helps maintain it?

Homeostasis is the maintenance of a stable internal environment, typically regulated by negative feedback mechanisms.

What are the roles of interphase and M-phase in the cell cycle?

Interphase is the period of growth and preparation, including DNA replication, while M-phase is when the cell undergoes mitosis and cytokinesis to divide.

What are the three steps of interphase in the cell cycle?

G1 phase (cell growth and normal functions), S phase (DNA replication), and G2 phase (preparation for mitosis).

Why would a cell go through mitosis?

To grow, replace damaged cells, or reproduce asexually.

What are the roles of mitosis and cytokinesis in M-phase?

Mitosis divides the nucleus and its contents, while cytokinesis divides the cytoplasm, producing two daughter cells.

What is the G0 phase and why do cells enter it?

G0 is a resting or non-dividing phase

What is the difference between chromatin and chromosomes?

Chromatin is the uncondensed form of DNA in the nucleus during interphase, while chromosomes are the condensed, organized form of DNA during cell division.

What are sister chromatids and where is the centromere located?

Sister chromatids are identical copies of a chromosome joined at the centromere, which is the region that holds them together.

What are the roles of centrosomes/centrioles and spindle fibers in mitosis?

Centrosomes/centrioles organize microtubules to form the spindle apparatus, and spindle fibers attach to chromosomes to separate sister chromatids.

What happens in each phase of mitosis (PMAT) and cytokinesis, and how can they be recognized?

Prophase: chromosomes condense, spindle forms

What occurs at the G1, G2, and M-spindle checkpoints?

G1 checkpoint ensures the cell is ready for DNA replication, G2 checkpoint verifies DNA replication is complete and undamaged, and the M-spindle checkpoint ensures all chromosomes are properly attached to the spindle before anaphase.

What are the roles of cyclin and cyclin-dependent kinases (CDKs) in cell cycle control?

Cyclins regulate the timing of the cell cycle by activating CDKs, which phosphorylate target proteins to drive progression through the checkpoints.

How can disruption of cell cycle regulation lead to cancer?

Mutations in genes controlling the cell cycle can cause uncontrolled cell division, resulting in tumor formation and cancer.

Why would apoptosis be an appropriate response to a disruption in the cell cycle?

Apoptosis removes damaged or abnormal cells that could potentially lead to cancer, maintaining tissue health.