AP Biology - Unit 4: Cell Communication All Topics

What is the primary function of cell-to-cell signaling?

To facilitate communication critical for the function and survival of cells.

What are the two modes of communication between cells?

Direct contact and local or long-distance signaling.

What is direct contact in cell signaling?

Communication by cell-cell contact through direct channels or cell-cell recognition.

What structures allow animal cells to communicate directly?

Gap junctions (connexons).

What structures allow plant cells to communicate directly?

Plasmodesmata.

What is paracrine signaling?

A signaling cell releases chemical messages that travel a short distance to affect nearby target cells.

Give an example of paracrine signaling.

Mast cells releasing histamine to signal an inflammatory response.

What is synaptic signaling?

A special type of paracrine signaling that occurs in animal nervous systems.

How do neurons communicate with target cells?

By secreting neurotransmitters that diffuse across the synaptic cleft.

What is autocrine signaling?

A cell signals to itself by releasing a ligand that binds to its own receptors.

What is long-distance signaling?

Communication using hormones that produce responses in target cells far from the signaling cell.

How do plants utilize long-distance signaling?

By releasing hormones that travel through vascular tissue or air.

What is endocrine signaling?

A type of long-distance signaling where specialized cells release hormones into the circulatory system.

Give an example of a hormone involved in endocrine signaling.

Insulin, released by the pancreas into the bloodstream.

What are ligands in cell signaling?

Chemical messengers that can be peptides or small molecules.

What are receptors in cell signaling?

Proteins that recognize and bind to specific chemical messengers (ligands).

What are cell-surface receptors?

Receptors embedded in the plasma membrane that bind to polar, water-soluble ligands.

What are the three domains of cell-surface receptors?

Ligand-binding domain, transmembrane domain, and intracellular domain.

What are intracellular receptors?

Receptors found in the cytoplasm or nucleus that bind to ligands that can pass through the plasma membrane.

What is the first stage of cell signaling?

Reception, where a ligand binds to a receptor.

What occurs during the transduction stage of cell signaling?

The extracellular signal is converted into an intracellular response.

What is the final stage of cell signaling?

Response, where a cell process is altered.

What type of signaling involves a cell secreting a substance to an adjacent target cell?

Paracrine signaling.

What is the role of cytokines in autocrine signaling?

Cytokines can signal to the macrophage itself to regulate its activity.

What is the significance of receptor-ligand binding?

It is highly specific and can initiate signaling cascades.

What type of molecules can ligands be?

Ligands can be polar (charged, hydrophilic) or large molecules.

What happens during the transduction stage of cell signaling?

The receptor undergoes a conformational change and initiates a signaling cascade.

What role do protein kinases play in signal transduction?

They relay and amplify the signal by transferring phosphate groups from ATP to proteins.

What is the function of protein phosphatases?

They remove phosphate groups from proteins, returning them to their baseline state.

What is phosphorylation and how does it affect proteins?

Phosphorylation adds a phosphate group to a protein, altering its shape and activity.

What are second messengers in cell signaling?

Small, non-protein molecules that relay and amplify the signal within the cell.

Give an example of a second messenger.

Cyclic AMP (cAMP), which activates protein kinases.

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

The final molecule converts the signal to a response that alters a cellular process.

What are some examples of cellular responses?

Cell growth, secretion of molecules, and turning genes on or off.

What is cross talk in signaling pathways?

It refers to the interaction between different signaling pathways.

What are G protein coupled receptors (GPCRs)?

The largest category of cell surface receptors, important in animal sensory systems.

How are GPCRs activated?

Ligand binding causes a conformational change, activating the receptor and G proteins.

What is the role of ion channels in cell signaling?

They act as gates for ions, opening or closing in response to ligand binding.

What can mutations in receptor proteins lead to?

Changes in the transduction of signals, potentially resulting in diseases.

What is the significance of signal transduction pathways?

They influence how a cell responds to its environment and can alter gene expression.

What initiates a signaling cascade?

The activation of a receptor upon ligand binding.

What is the effect of activated kinases in signaling pathways?

They can activate many other proteins, amplifying the signal.

What happens to a protein after it is phosphorylated?

Its shape and function change, which can increase or inactivate its activity.

What is the role of calcium ions in signaling pathways?

They can act as second messengers, binding to proteins and altering their activity.

What is the role of ATP in phosphorylation?

ATP provides the phosphate group that is transferred to proteins by kinases.

What is the importance of the ligand-receptor complex?

It can bind to control regions of target genes, turning them on or off.

How do signaling pathways communicate with each other?

Through cross talk, where proteins in one pathway can affect others.

What is the overall purpose of signal transduction pathways?

To allow cells to respond appropriately to external signals and changes.

What can result from defective protein phosphatases?

It can lead to diseases such as cancer and diabetes due to disrupted signaling pathways.

What is the significance of cellular responses in signal transduction?

They can lead to significant changes in cell function and behavior.

What is homeostasis?

The state of relatively stable internal conditions in an organism.

What are set points in physiology?

Values for various physiological conditions that the body tries to maintain, with a normal range for fluctuation.

What is the normal range for human body temperature?

97℉ to 99℉, with a set point of 98.6℉.

What are the two types of feedback loops?

Negative feedback and positive feedback.

Define stimulus in the context of feedback loops.

A variable that will cause a response.

What role do receptors/sensors play in feedback loops?

They detect a stimulus and send information to the control center (brain).

What is the effector in a feedback loop?

A muscle or gland that responds to the stimulus.

What is the response in a feedback loop?

Changes that decrease or increase the effect of the stimulus.

What is the most common feedback mechanism?

Negative feedback.

How does negative feedback work?

It reduces the effect of the stimulus.

Give an example of negative feedback.

Body temperature regulation.

What happens during the negative feedback response to heat?

Sweat glands are activated to cool the body.

What is positive feedback?

A feedback mechanism that increases the effect of a stimulus.

Give an example of positive feedback.

Child labor during childbirth.

What is a homeostatic imbalance?

When the body is unable to maintain homeostasis.

What are some causes of homeostatic imbalances?

Genetic disorders, drug or alcohol abuse, intolerable conditions.

What is a disease in the context of homeostasis?

When the body cannot regulate homeostasis, such as in cancer or diabetes.

What is the role of cell signaling in homeostasis?

Cells in a multicellular organism must communicate to maintain homeostasis.

What are signal transduction pathways?

The means through which communication occurs among cells to maintain homeostasis.

What is the cell cycle?

The life of a cell from its formation until it divides.

What are the main functions of the cell division process?

Reproduction of cells, growth of cells, and tissue repair.

What must cells do before division?

Organize and package their DNA.

What proteins do DNA wrap around to form nucleosomes?

Histones.

What is chromatin?

Strings of nucleosomes that form when DNA is not actively dividing.

What happens to chromatin after DNA replication?

It condenses to form chromosomes.

What are sister chromatids?

Duplicated copies of a chromosome joined together.

What is the centromere?

The region on each sister chromatid where they are most closely attached.

What is the role of the kinetochore?

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

What is a genome?

All of a cell's genetic information (DNA).

How many chromosomes do humans have?

46 chromosomes.

What are homologous chromosomes?

Two chromosomes (one from mom and one from dad) that are the same length and carry genes controlling the same characteristics.

What are somatic cells?

Body cells that are diploid (2n) with two sets of chromosomes.

What are gametes?

Reproductive cells that are haploid (n) with one set of chromosomes.

What phases make up the cell cycle?

Interphase and mitosis.

What are the three phases of interphase?

G1 (first gap), S (synthesis), and G2 (second gap).

What occurs during the G1 phase?

The cell is metabolically active, duplicates organelles, and carries out normal functions.

What happens during the S phase?

DNA replication occurs, forming two sister chromatids.

What is mitosis?

The process where the nucleus divides.

What is cytokinesis?

The division of the cytoplasm.

What are the stages of mitosis?

Prophase, metaphase, anaphase, and telophase.

What key events occur during prophase?

Chromosomes condense, nucleoli disappear, and the mitotic spindle begins to form.

What happens during metaphase?

Chromosomes line up at the metaphase plate, and microtubules attach to kinetochores.

What occurs during anaphase?

Sister chromatids separate and move to opposite ends of the cell.

What are the key events of telophase?

Mitotic spindle breaks down, two daughter nuclei form, and chromosomes become less condensed.

How does cytokinesis differ in animal and plant cells?

In animals, a cleavage furrow appears; in plants, a cell plate forms.

What is eukaryotic chromatin composed of?

DNA and proteins

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

24 chromosomes

What is the most important checkpoint in the cell cycle?

G1 Checkpoint

What does the G1 Checkpoint check for?

Cell size, growth factors, and DNA damage

What happens if a cell receives a 'Stop' signal at the G1 Checkpoint?

The cell enters a nondividing state known as G0 phase