Cell Communication Processes
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Questions and Answers

What type of communication occurs through gap junctions in animal cells?

  • Endocrine signaling
  • Direct contact (correct)
  • Paracrine signaling
  • Local signaling

Which signaling mechanism is characterized by the release of neurotransmitters that diffuse across a synaptic cleft?

  • Direct contact
  • Long-distance signaling
  • Synaptic signaling (correct)
  • Paracrine signaling

What structure allows plant cells to communicate directly through the cytoplasm?

  • Gap junctions
  • Neurotransmitters
  • Hormones
  • Plasmodesmata (correct)

What type of signaling involves a secreting cell releasing a chemical messenger to nearby cells?

<p>Paracrine signaling (D)</p> Signup and view all the answers

Which of the following is true about insulin as a signaling molecule?

<p>It travels through the bloodstream for long-distance signaling. (B)</p> Signup and view all the answers

Which type of cell communication is essential for the growth and development of multicellular organisms?

<p>All types of signaling (A)</p> Signup and view all the answers

What is a local regulator in a paracrine signaling pathway?

<p>A growth factor released by secretory cells (B)</p> Signup and view all the answers

In what way can plant hormones reach their target tissues?

<p>By traveling in the air or through vascular tissue (A)</p> Signup and view all the answers

What role do CDK complexes play in the cell cycle?

<p>They phosphorylate target proteins to regulate key events. (C)</p> Signup and view all the answers

Which of the following correctly describes contact inhibition?

<p>It stops the cell cycle at the G₁ phase when cells touch. (D)</p> Signup and view all the answers

What is a characteristic of malignant tumors?

<p>They can lose anchorage dependency and metastasize. (D)</p> Signup and view all the answers

Which factor is NOT a form of external regulation of the cell cycle?

<p>DNA mutations (C)</p> Signup and view all the answers

What is the main risk factor for cell mutations that can lead to cancer?

<p>Exposure to ultraviolet light (A)</p> Signup and view all the answers

What occurs during the G₁ phase of the cell cycle?

<p>Contact inhibition can stop progression. (A)</p> Signup and view all the answers

Which action is a recommended strategy for cancer prevention?

<p>Use SPF to protect the skin from the sun. (B)</p> Signup and view all the answers

What is the most likely checkpoint responsible for arresting the cell cycle due to cell damage?

<p>G₁ checkpoint (A)</p> Signup and view all the answers

Which statement about cancer cells is accurate?

<p>They accumulate DNA mutations over time. (C)</p> Signup and view all the answers

What is the primary effect of vinblastine on the cell cycle?

<p>It inhibits microtubule assembly and arrests the cycle. (B)</p> Signup and view all the answers

What type of cells have two sets of chromosomes?

<p>Somatic cells (C)</p> Signup and view all the answers

Which phase of the cell cycle involves DNA replication?

<p>S phase (D)</p> Signup and view all the answers

What is the result of mitosis?

<p>Two diploid daughter cells (C)</p> Signup and view all the answers

During which mitosis stage do sister chromatids separate?

<p>Anaphase (D)</p> Signup and view all the answers

Which structure reappears during telophase?

<p>Nucleoli (B)</p> Signup and view all the answers

What checkpoint is considered the most important in the cell cycle?

<p>G1 checkpoint (B)</p> Signup and view all the answers

What is the fate of a cell that fails the G2 checkpoint?

<p>It undergoes apoptosis (A)</p> Signup and view all the answers

In what cellular process does cytokinesis occur?

<p>After mitosis (A)</p> Signup and view all the answers

If a sperm cell contains 12 chromosomes, how many chromosomes does the organism have?

<p>24 chromosomes (B)</p> Signup and view all the answers

What is the role of cyclins in the cell cycle?

<p>To regulate cell cycle checkpoints (B)</p> Signup and view all the answers

What happens during prometaphase?

<p>The nuclear envelope disappears (C)</p> Signup and view all the answers

In which phase do chromosomes align at the metaphase plate?

<p>Metaphase (C)</p> Signup and view all the answers

What triggers the start of anaphase?

<p>Shortening of microtubules (A)</p> Signup and view all the answers

During cytokinesis in animal cells, what structure is formed?

<p>Cleavage furrow (C)</p> Signup and view all the answers

What is the first stage of cell signaling?

<p>Reception (C)</p> Signup and view all the answers

Which type of signaling occurs when a cell secretes a substance to an adjacent target cell?

<p>Paracrine signaling (B)</p> Signup and view all the answers

What is the role of second messengers in signal transduction pathways?

<p>To amplify the cellular response (A)</p> Signup and view all the answers

What happens during the transduction stage of cell signaling?

<p>Signal is amplified through a cascade of proteins. (C)</p> Signup and view all the answers

What type of receptor is most commonly involved in signal pathways responding to polar, water-soluble ligands?

<p>G protein coupled receptors (D)</p> Signup and view all the answers

What is the function of protein kinases in signal transduction?

<p>To phosphorylate target proteins (C)</p> Signup and view all the answers

Which of the following molecules can pass through the plasma membrane to bind to intracellular receptors?

<p>Steroid hormones (A)</p> Signup and view all the answers

What is the final outcome of the response stage in cell signaling?

<p>Change in membrane permeability (A)</p> Signup and view all the answers

How can mutations in receptor proteins affect cell signaling?

<p>They alter transduction of the signal. (C)</p> Signup and view all the answers

Which molecule is often a common second messenger in cellular signaling?

<p>Cyclic AMP (cAMP) (A)</p> Signup and view all the answers

What distinguishes the response phase from the reception and transduction phases in cell signaling?

<p>It alters a physiological process. (D)</p> Signup and view all the answers

What type of signaling is characterized by a cell responding to a substance it has secreted itself?

<p>Autocrine signaling (A)</p> Signup and view all the answers

During which stage is the signal transformed from an extracellular format to an intracellular format?

<p>Transduction (A)</p> Signup and view all the answers

What type of receptors are found in the cytoplasm or nucleus and bind to hydrophobic molecules?

<p>Intracellular receptors (B)</p> Signup and view all the answers

What is the primary role of G protein coupled receptors (GPCRs)?

<p>Bind to and activate enzymes upon ligand binding (C)</p> Signup and view all the answers

Which of the following describes the status of GPCRs before ligand binding?

<p>Inactive and unable to signal (C)</p> Signup and view all the answers

What is the main outcome of negative feedback mechanisms in the body?

<p>Reduce the effect of the stimulus (A)</p> Signup and view all the answers

What hormone is primarily involved in the positive feedback mechanism during childbirth?

<p>Oxytocin (A)</p> Signup and view all the answers

Which structure in eukaryotic chromosomes is responsible for linking sister chromatids to the mitotic spindle?

<p>Centromere (C)</p> Signup and view all the answers

What describes the cellular response initiated by ligand-gated ion channels?

<p>Opening or closing of gates for ions (A)</p> Signup and view all the answers

How are homologous chromosomes defined?

<p>Two chromosomes with the same characteristics from both parents (A)</p> Signup and view all the answers

What is the primary function of the cell cycle?

<p>Cell division and reproduction (A)</p> Signup and view all the answers

What happens to chromatin when a cell is actively dividing?

<p>It condenses to form chromosomes (D)</p> Signup and view all the answers

Which of these conditions can lead to homeostatic imbalances?

<p>Genetic disorders (D)</p> Signup and view all the answers

What type of feedback loop is exemplified by blood clotting?

<p>Positive feedback (C)</p> Signup and view all the answers

What is the function of histones in the organization of DNA?

<p>Package DNA into chromatin (D)</p> Signup and view all the answers

What physiological condition is regulated by a set point and normal range?

<p>Blood pressure (B)</p> Signup and view all the answers

Which component is involved in the initial detection of a stimulus in feedback loops?

<p>Receptor/sensor (D)</p> Signup and view all the answers

Flashcards

Direct Contact

A method of cell communication where signaling substances pass directly between adjacent cells through specialized junctions.

Cell Junctions for Direct Contact

Gap junctions in animal cells and plasmodesmata in plant cells allow for direct exchange of molecules between neighboring cells.

Paracrine Signaling

A type of local signaling where cells release signaling molecules that act on nearby target cells.

Synaptic Signaling

A type of local signaling that occurs in the nervous system where neurons release neurotransmitters across a synapse to communicate with target cells.

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Endocrine Signaling

Long-distance signaling where specialized cells release hormones into the bloodstream to reach target cells throughout the body.

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Plant Hormonal Signaling

A type of long-distance signaling where plants release hormones that travel through their vascular tissue or the air to reach target tissues.

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Ligand

A chemical messenger released by cells that communicate with other cells.

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Target Cell

A cell that is programmed to respond to a specific type of signal.

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What is paracrine signaling?

Signaling between cells that are close to each other.

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What are plasmodesmata?

These channels allow for communication between adjacent plant cells.

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What is cell signaling?

The process by which a cell receives and responds to a signal.

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What is reception?

Stage 1 of cell signaling, where the signaling molecule binds to a receptor protein.

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What is a ligand?

The molecule that binds to a receptor protein, starting the signaling cascade.

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What is a receptor?

A molecule that binds to a ligand and initiates a signaling cascade.

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What is transduction?

The conversion of an extracellular signal into an intracellular signal.

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What is a signal transduction pathway?

A series of molecules that amplify and relay a signal within a cell.

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What are protein kinases?

Enzymes that add phosphate groups to proteins, often involved in signal transduction.

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What are protein phosphatases?

Enzymes that remove phosphate groups from proteins, often involved in shutting down signal transduction.

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What are second messengers?

Small molecules that relay and amplify signals within a cell, often involved in transduction.

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What is response?

The final stage of cell signaling, where the signal is translated into a cellular response.

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How can mutations affect signal transduction?

Mutations in receptor proteins or signal transduction components can disrupt signaling pathways.

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How can defective protein phosphatases affect signal transduction?

Errors in protein phosphatases can contribute to diseases like cancer and diabetes by affecting signal transduction.

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Cyclins

A group of proteins that regulate the cell cycle by activating cyclin-dependent kinases (CDKs).

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Cyclin-dependent kinases (CDKs)

Enzymes that depend on cyclins for activation, and phosphorylate target proteins to regulate the cell cycle.

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G2 checkpoint

A checkpoint that ensures DNA replication is complete and accurate before the cell enters mitosis.

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Growth factors

Hormones that stimulate cell growth and division by activating signal transduction pathways, which activate CDKs.

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Contact inhibition

A regulatory mechanism where cell-surface receptors detect contact with other cells, inhibiting CDK activity and stopping cell division in the G1 phase.

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Anchorage dependence

A regulatory mechanism where cells require attachment to other cells or the extracellular matrix to divide.

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Cancer cells

Harmful mutations that escape normal cell cycle checkpoints, leading to uncontrolled cell growth and division.

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DNA mutations

Changes in the DNA sequence of a gene that can lead to uncontrolled cell growth, often found in cancer cells.

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Tumor

An abnormal mass of cells that arises from uncontrolled cell growth.

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Benign tumor

A cancer cell mass that doesn't invade surrounding tissues, often removed surgically and not life-threatening.

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G protein coupled receptors (GPCRs)

The largest category of cell surface receptors. They are important in animal sensory systems and bind to G proteins, which can bind to GTP.

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GTP

An energy molecule similar to ATP that activates G proteins in the presence of a ligand.

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Homeostasis

The state of relatively stable internal conditions that the body maintains.

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Stimulus

A variable that triggers a response in a feedback loop.

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Receptor/Sensor

The sensory organ that detects a stimulus and sends information to the control center (brain).

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Effector

A muscle or gland that responds to the signal from the control center.

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Negative Feedback

The change in the body that reduces the effect of the stimulus, maintaining homeostasis.

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Positive Feedback

The change in the body that increases the effect of the stimulus, pushing the body further away from its set point.

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Chromosome

A structure that contains genetic information and is composed of DNA associated with histones, forming nucleosomes.

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Histones

Proteins that associate with DNA to form nucleosomes.

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Nucleosomes

Bead-like structures formed by DNA wrapped around histones.

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Chromatin

A long, thread-like structure composed of DNA and histones. It is the non-condensed form of DNA.

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Centromere

The region on a chromosome where sister chromatids are attached.

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Kinetochore

Proteins attached to the centromere that link sister chromatids to the mitotic spindle.

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What are gametes?

A cell that participates in sexual reproduction and contains only one set of chromosomes (haploid). Examples: sperm cells and egg cells.

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What are somatic cells?

A cell that makes up the body of an organism and contains two sets of chromosomes (diploid). They are capable of dividing through mitosis.

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What is mitosis?

The process by which a cell divides to produce two genetically identical daughter cells. This is how somatic cells divide to grow and repair tissues.

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What is meiosis?

The process by which a cell divides to produce four genetically unique daughter cells with half the number of chromosomes (haploid). This is how gametes are produced.

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What is interphase?

The longest phase of the cell cycle, during which the cell grows, carries out normal functions, and replicates its DNA.

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What is G1 phase?

The first phase of interphase, where the cell grows and carries out normal functions.

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What is S phase?

The phase of interphase where the cell replicates its DNA, creating two identical copies of each chromosome.

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What is G2 phase?

The second phase of interphase, where the cell prepares for mitosis by growing more and making necessary proteins and organelles.

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What is the G1 checkpoint?

A control point in the cell cycle that checks for cell size, growth factors, and DNA damage. It determines whether the cell will continue through the cell cycle or enter a non-dividing state.

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What is the G2 checkpoint?

A control point in the cell cycle that checks for the completion of DNA replication and any potential damage to DNA. It decides whether the cell should proceed to mitosis or pause to repair damage.

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What is the M (Spindle) checkpoint?

A control point in the cell cycle that ensures that all chromosomes are properly attached to microtubules before they are pulled apart during anaphase. Prevents improper chromosome segregation.

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What is apoptosis?

A type of programmed cell death that eliminates damaged or unwanted cells from the body.

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What happens in prophase?

The first phase of mitosis, where the chromatin condenses into visible chromosomes, the nuclear envelope breaks down, and the mitotic spindle begins to form.

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What happens in prometaphase?

The second phase of mitosis, where the nuclear envelope breaks down completely, microtubules attach to kinetochores on chromosomes, and chromosomes begin to move towards the center of the cell.

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What happens in metaphase?

The third phase of mitosis, where duplicated chromosomes align at the metaphase plate, which is the center of the cell, and microtubules are attached to the kinetochores of each sister chromatid.

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What happens in anaphase?

The fourth phase of mitosis, where sister chromatids separate and move to opposite poles of the cell as microtubules shorten.

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What happens in telophase?

The final stage of mitosis, where two daughter nuclei form, chromosomes decondense, and the nuclear envelope reforms. Cytokinesis, the division of the cytoplasm, begins.

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Study Notes

Cell Communication

  • Cells communicate in three ways: direct contact, local signaling, and long-distance signaling.
  • Direct contact: Communication through cell junctions (gap junctions in animal cells, plasmodesmata in plant cells). Substances pass freely between adjacent cells. Example: immune cells communicating via direct contact.
  • Local signaling: A secreting cell releases chemical messages (ligands/local regulators) that travel a short distance via extracellular fluid, causing a response in a target cell.
    • Paracrine signaling: Secretory cells release local regulators (e.g., growth factors) through exocytosis to nearby target cells.
    • Synaptic signaling: Occurs in animal nervous systems. Neurons secrete neurotransmitters that diffuse across a synaptic cleft (space between nerve cell and target cell) to trigger a response.
  • Long-distance signaling: Animals and plants use hormones for long-distance communication.
    • Plants: Hormones travel in vascular tissue (xylem and phloem) or through the air to reach target tissues.
    • Animals: Specialized cells release hormones into the circulatory system to reach target cells; example: insulin released by pancreas into bloodstream.

Cell Signaling: Overview

  • Cell-to-cell communication involves three stages: reception, transduction, and response.
  • Reception: Ligand (signal molecule) binds to a receptor (macromolecule). Receptors are highly specific for the ligand. Binding initiates transduction by causing a conformational change in the receptor, allowing the receptor to interact with other cellular molecules and initiate transduction.
    • Plasma membrane receptors: Bind to polar, water-soluble, large ligands. Examples include G protein-coupled receptors (GPCRs) and ligand-gated ion channels.
    • Intracellular receptors: Bind to ligands that can pass through the plasma membrane (e.g., hydrophobic molecules like steroid and thyroid hormones, gases like nitric oxide). Located in the cytoplasm or nucleus.
  • Transduction: Conversion of an extracellular signal to an intracellular signal. This involves a sequence of changes in a series of molecules (signal transduction pathway).
    • Signal amplification occurs during transduction.
    • Second messengers (small, non-protein molecules and ions) help relay the message and amplify the response. Example: cAMP.
  • Response: The final molecule in the signaling pathway alters a cellular process (e.g., protein altering membrane permeability, enzymes changing metabolic processes, proteins turning genes on/off).

Signal Transduction Pathways

  • Signal transduction pathways influence a cell's response to the environment, altering gene expression and cell function.
  • Mutations in receptor proteins or components of the signaling pathway will affect signal transduction. Some diseases, like cancer and diabetes, result from defective protein phosphatases that affect signal transduction.

Receptors

  • G protein-coupled receptors (GPCRs): Largest category of cell surface receptors, important in animal sensory systems. A G protein (bound to GTP) binds to the receptor, activates the G protein, and relays the signal to an enzyme that amplifies the signal, leading to a cellular response.
  • Ligand-gated ion channels: Act as "gates" for ions. Ligand binding opens or closes the "gate," allowing ion diffusion, thus initiating a cellular response.

Homeostasis

  • Homeostasis is the maintenance of relatively stable internal conditions.
  • Body monitors internal conditions via feedback loops: negative feedback and positive feedback.
  • Negative feedback: Reduces a stimulus (e.g., sweating, regulating blood sugar, breathing).
    • Stimulus → receptor → control center → effector → response (reduces stimulus).
  • Positive feedback: Increases a stimulus (e.g., childbirth, blood clotting, fruit ripening).
    • Stimulus → receptor → control center → effector → response (increases stimulus).
  • Homeostatic imbalances can lead to disease (e.g., cancer, diabetes).

Cell Cycle

  • The cell cycle is the life of a cell from its formation to division. It alternates between interphase and mitosis/cytokinesis.
  • Interphase: The longest portion (G₁, S, G₂).
    • G₁: Cell growth and normal function.
    • S: DNA replication and chromosome duplication.
    • G₂: Final growth and preparation for mitosis.
  • Mitosis: Nucleus divides into two identical nuclei.
    • Prophase: Chromatin condenses, nucleoli disappear, and mitotic spindle forms.
    • Prometaphase: Nuclear envelope fragments, microtubules enter nuclear area and attach to kinetochores.
    • Metaphase: Chromosomes line up at metaphase plate, microtubules attached to kinetochores.
    • Anaphase: Sister chromatids separate and move to opposite poles.
    • Telophase and cytokinesis: Two daughter nuclei form, chromosomes decondense, nucleoli reappear; cytokinesis (cytoplasm division) follows.

Cell Cycle Regulation

  • Checkpoints (critical control points) regulate the cell cycle, ensuring orderly progression.
  • G₁ checkpoint: Checks for cell size, growth factors, and DNA damage.
  • G₂ checkpoint: Checks for completion of DNA replication and DNA damage.
  • M (spindle) checkpoint: Checks for microtubule attachment to chromosomes.
  • Internal regulators: Cyclins (varying concentration) and cyclin-dependent kinases (CDKs, constant concentration, active only with specific cyclin).
  • External regulators: Growth factors, contact/density inhibition, and anchorage dependence regulate cell division.

Cancer

  • Cancer arises from DNA mutations that cause cells to evade cell cycle checkpoints, divide uncontrollably, evade apoptosis, and undergo metastasis (spread).
    • Normal cells follow checkpoints, divide a limited number of times in culture, and undergo apoptosis with significant errors.
    • Cancer cells do not follow checkpoints, divide infinitely in culture, evade apoptosis, and spread.
  • Cancers form tumors (masses of abnormal cells): benign (remain localized) and malignant (spread).
  • Cancer prevention includes avoiding risk factors like smoking, eating a healthy diet, protecting skin from the sun, and getting regular screenings.

Biological Structures and Function

  • Chromosomes are complex structures assembled from smaller units (nucleosomes, chromatin).
  • Major functions of chromosomes: carrying genetic information (genome).

Chromosome Information

  • Genome: All of a cell's genetic information (DNA).
    • Prokaryotes: Singular, circular DNA.
    • Eukaryotes: One or more linear chromosomes (specific number for each species).
  • Homologous chromosomes: Same length, centromere position, and carry genes controlling same characteristics (one from each parent).
  • Diploid (2n): Two sets of chromosomes.
  • Haploid (n): One set of chromosomes (e.g., eggs/sperm)

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Description

Explore the three main methods of cell communication: direct contact, local signaling, and long-distance signaling. Understand how cells interact through junctions, release local regulators, and utilize hormones for communication across distances. This quiz covers fundamental concepts essential for understanding cellular interactions.

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