AP Bio Unit 4

cell communication

The process through which cells coordinate activities and respond to environmental changes by transmitting signals.

signal transduction pathway

A series of molecular events that convert a signal on a cell's surface into a specific cellular response.

reception

The first step in a signal transduction pathway where a signaling molecule binds to a receptor.

transduction

The relay of a signal through various proteins or molecules within the signal transduction pathway.

response

The final step in a signal transduction pathway where the cell performs a specific action in response to the signal.

ligand

A molecule that specifically binds to a receptor, triggering a signal.

positive feedback

A process that amplifies a response; for example, oxytocin release during childbirth increases contractions.

negative feedback

A process that counteracts a change to maintain homeostasis; for example, regulation of blood sugar levels by insulin and glucagon.

apoptosis

Programmed cell death; it helps eliminate damaged or unnecessary cells.

protein kinases

Enzymes that phosphorylate other proteins, altering their activity to propagate the signal.

second messengers

Small molecules that relay and amplify signals inside the cell, such as cAMP.

G-protein-coupled receptors (GPCRs)

Membrane receptors that detect external signals and activate internal pathways.

quorum sensing

A method of bacterial communication that coordinates group behaviors based on population density.

homeostasis

The maintenance of stable internal conditions necessary for survival despite external changes.

intracellular receptors

Receptors located inside the cell that bind to hydrophobic ligands such as steroid hormones.

membrane-bound receptors

Receptors located on the cell surface that bind to hydrophilic ligands.

phosphorylation cascade

A series of events where one enzyme phosphorylates another, leading to various cellular responses.

phosphatases

Enzymes that remove phosphate groups from proteins, turning off signal transduction pathways.

ligand-gated ion channel

A channel that opens or closes in response to a ligand binding, allowing ions to pass through the membrane.

amplification

The process whereby a single signaling molecule activates multiple downstream molecules, creating a large response.

hormones

Signaling molecules that act as long-distance signals, traveling through the bloodstream to target cells.

feedback loop

A system where the output of a process influences its own activity, enhancing or suppressing it.

scaffolding proteins

Proteins that hold multiple components of a pathway together, increasing the speed and accuracy of signaling.

cross-talk

Interactions between different signaling pathways that can enhance or inhibit cellular responses.

secondary messenger

Non-protein molecules that propagate a signal inside the cell, such as cAMP and calcium ions.

endocrine signaling

A form of signaling where hormones are released into the bloodstream to reach distant target cells.

adenylyl cyclase

An enzyme that converts ATP to cyclic AMP (cAMP), a secondary messenger in signaling pathways.

hydrophilic ligands

Ligands that cannot cross the cell membrane and bind to surface receptors.

hydrophobic ligands

Ligands that can cross the cell membrane and bind to intracellular receptors.

specificity in signaling

Achieved through unique receptors and pathways in different cells tailored to specific ligands.

calcium ions

Act as a second messenger, triggering processes like muscle contraction and neurotransmitter release.

cyclic GMP (cGMP)

A secondary messenger involved in various signaling pathways, including those in phototransduction.

nuclear response

Changes in gene expression resulting from signaling events.

cytoplasmic response

Changes in cell activity, such as the activation of enzymes due to signaling.

MAP kinase pathway

A signaling pathway involving a cascade of protein kinases affecting gene expression and cell functions.

cell differentiation

The process by which cells become specialized in structure and function.

tumor suppressor protein

Proteins like p53 that monitor cell stress and can induce apoptosis or cell cycle arrest.

integrins

Membrane proteins that connect cells to the extracellular matrix and can activate signaling pathways.

Notch signaling pathway

A pathway involved in cell differentiation through direct cell-to-cell communication.

endoplasmic reticulum (ER)

A cell organelle involved in calcium storage and release, influencing cellular responses.

GTP

A molecule that binds to G-proteins to activate them in signaling pathways.

diacylglycerol (DAG)

A second messenger produced in signaling pathways that activates protein kinase C.

ligand binding

The attachment of a signaling molecule to a receptor, initiating a signal transduction cascade.

tight junctions

Structures that seal adjacent cells to prevent leakage of extracellular fluid.

gap junctions

Channels that allow direct communication between adjacent cells.

desmosomes

Anchoring structures that provide mechanical strength to cells.

cAMP phosphodiesterase

An enzyme that breaks down cAMP to terminate signaling responses.

mitosis

The process of nuclear division resulting in two genetically identical daughter cells.

cell cycle

The series of phases (Interphase and M phase) through which a cell passes to divide.

centrosomes

Structures that organize microtubules and form spindle fibers during mitosis.

prophase

The first phase of mitosis where chromatin condenses into chromosomes.

prometaphase

The phase where the nuclear envelope dissolves and spindle fibers attach to chromosomes.

metaphase

The phase where chromosomes align at the metaphase plate, ensuring proper segregation.

anaphase

The phase where sister chromatids are pulled apart toward opposite poles.

telophase

The phase where chromosomes de-condense and nuclear envelopes re-form.

cytokinesis

The process of dividing the cytoplasm after mitosis, differing in plant and animal cells.

mitotic spindle

A structure made of microtubules that separates chromosomes during mitosis.

kinetochores

Protein complexes where spindle fibers attach during mitosis.

G1 checkpoint

A cell cycle checkpoint that assesses cell size, nutrient availability, and DNA integrity.

G2 checkpoint

A checkpoint that verifies DNA replication and checks for DNA damage before mitosis.

cyclins

Proteins that regulate the cell cycle in conjunction with cyclin-dependent kinases (Cdks).

M checkpoint

A checkpoint ensuring all chromosomes are attached to spindle fibers before anaphase.

feedback inhibition

A regulatory mechanism that prevents excess product in metabolic pathways.

insulin signaling

The process by which insulin binds to receptors and activates pathways for glucose uptake.

chromosome condensation

The process by which chromatin coils into visible chromosomes for separation during mitosis.

error in chromosome segregation

Can lead to aneuploidy, causing diseases such as cancer.

spindle fibers

Microtubules that help align and separate chromosomes during mitosis.

regulation of the cell cycle

Involves genes that control cell division, where mutations can lead to cancer.

mitotic phase (M phase)

Includes mitosis and cytokinesis, differing from Interphase which encompasses cell growth.

sister chromatids

Identical copies of a chromosome formed after DNA replication.

homologous chromosomes

Pairs of chromosomes with genes for the same traits but possibly different alleles.