Unit 4 Cell Communication and Cell Cycle AP Biology Exam Review

Flashcards covering cell communication, cell cycle, and cancer for AP Biology exam review.

What is bacterial quorum sensing?

Mechanism by which bacteria regulate gene expression based on population density using signal molecules.

How are plasmodesmata examples of direct contact between cells?

Pores in plant cell walls connecting adjacent cells, facilitating the movement of water and materials.

How is direct contact communication different than local regulation?

Direct contact requires cells touching; local regulation involves signals traveling short distances to target cells.

How are neurotransmitters examples of local regulation?

They travel across a synapse from one nerve cell to another.

What is a hormone? How is it an example of long distance communication?

Hormones are made in an organ/gland and released into the bloodstream to travel long distances to target cells.

What are the steps of the signal transduction pathway?

1. reception 2. transduction 3. response

Compare an intercellular to an intracellular receptor.

Intercellular receptors are on the plasma membrane; intracellular receptors are in the cytoplasm.

What is a ligand?

A molecule which produces a signal by binding to a site on a target protein

How is cAMP used in transduction?

cAMP is a second messenger that amplifies a signal, increasing the cellular response.

Give an example of a response that may occur after transduction.

Regulation of a gene (turning it on or off); regulation of protein/enzyme production.

How would a mutation in the receptor affect the signal transduction pathway?

Mutation in receptor protein changes its shape; when the shape is changed, the ligand cannot bind. Therefore, the pathway is likely inhibited.

Compare a positive to a negative feedback loop.

Negative feedback loops bring a system back to a set point; positive feedback loops amplify a response.

Give two examples of each type of feedback loop.

Examples of Positive Feedback: Uterine contractions during childbirth, Fruit ripening. Examples of Negative Feedback: Blood glucose regulation Blood – water regulation

How are feedback loops used to maintain homeostasis?

Feedback loops allow an organism to maintain stability around a target set point.

What cells undergo mitosis and cytokinesis? Why?

Cells undergo cellular division for growth, development, repair and in some cases, reproduction. Cells that undergo mitosis are any cell other than a gamete OR cells that are non-dividing and in G0 phase.

Describe what happens in G1, S, and G2 phases of the cell cycle.

B) G1 Phase: cell growth. C) S Phase: DNA replicates. D) G2 Phase: preparation for mitosis

What events occur during each stage of mitosis?

Prophase : Nuclear envelope breaks down, chromosomes condense, centrioles move to poles of the cell; Metaphase: Chromosomes line up along metaphase plate; Anaphase: Spindle apparatus contracts and pulls duplicated chromosomes apart and away from each other; Telophase: Chromosomes are on opposite ends of cell; nuclear envelope reforms and cytokinesis takes place.

Why is cytokinesis important?

Cytokinesis is important for cells to receive cytoplasm and organelles after division. In plants, a new cell wall forms during cytokinesis along a cell plate. In animal cells, proteins in the cell membrane contract to pinch the cell off into two.

How do cyclins and cyclin dependent kinases work to regulate the cell cycle?

Cyclins are proteins that accumulate during the cell cycle. As cyclins are produced, they bind to an enzyme called cyclin-dependent kinase. This complex is called mitosis-promotion factor.

What is the purpose of the checkpoints found at various stages of the cell cycle?

The integrity of the DNA is assessed at the G1 checkpoint. Proper chromosome duplication is assessed at the G2 checkpoint. Attachment of each kinetochore to a spindle fiber is assessed at the M checkpoint.

How does cancer occur if there are checkpoints in the cell cycle?

In addition to the cell cycle regulatory proteins above, any protein that influences the cycle can be altered in such a way as to override cell cycle checkpoints. An oncogene is any gene that, when altered, leads to an increase in the rate of cell cycle progression.

What is apoptosis and why is this process important?

Apoptosis is programmed cell death. This is important for cell cycle regulation – if a cell fails a checkpoint and the pathway is working correctly, apoptosis is triggered. If it not, then uncontrolled cell growth can occur.