Unit 4 AP Biology; Cell Communication + the Cell Cycle

Signal Transduction

The process by which a cell converts an external signal into a specific internal response.

Receptor

A protein that detects a specific signal and initiates a response within a cell

Ligand

A signaling molecule that binds to a specific receptor protein, initiating a cellular response

Autocrine

A form of cell communication where a cell releases a chemical messenger that binds to receptors on its own surface, thereby regulating its own behavior

Paracrine

A type of local cell communication where a cell releases signaling molecules, such as growth factors or neurotransmitters, that act on a nearby target cells

Endocrine

Glands that produce hormones and release them directly into the bloodstream to be transported throughout the body

Juxtacrine

A type of cell communication requiring direct physical contact between cells

Hormone

A chemical messenger secreted by an endocrine gland into the bloodstream to regulate physiological processes in target cells located elsewhere in the body

Plasmodesmata

Microscopic channels that pass through the cell walls of adjacent plant cells, directly connecting their cytoplasm to allow for the transport of water, nutrients, signaling molecules, and other substance between them

Gap Junction

Channels that connection the cytoplasm of adjacent animal cells, allowing for the direct passage of ions and small molecules between them

Intercellular

Between cells

Intracellular

within the cell

Phosphorylation

the addition of a phosphate group to a molecule, a crucial process that can activate or deactivate enzymes, regulate cellular processes, and store energy

Kinase

An enzyme that catalyzes the addition of an phosphate group from ATP to a target protein

Phosphatase

An enzyme that removes phosphate groups from molecules (proteins or sugars)

Enzyme-Linked Receptor

A cell-surface protein that binds a signaling molecule (ligand) and then activates its own enzymatic activity or associates with an enzyme

G-Protein Coupled Receptor

A cell-surface rece[tors that detects molecules outside the cell and initates a signal transduction pathway by activating internal G proteins

Ion Channel Linked Receptors (ligand-gated ion channels)

A transmembrane portions that opens or closes a specific ion channel in the cell membrane when a signaling molecule binds to it

Second Messenger

A small, non-protein intracellular signaling molecule or into that relays signals from a cell surface receptors to target molecules inside the cell, amplifying and propagating the original signal

Positive Feedback

A mechanism where a stimulus amplifies the original response, pushing a system further away from its initial set point

Negative Feedback

a process where the output of a pathway or system inhibits the pathway’s own production, which stabilizes the system and maintains homeostasis

Cell Cycle

The series of events in a cell’s life leading to its growth, DNA replication, and division into two daughter cells

Interphase

the phase of the cell cycle where a cell grows, replicates its DNA, and prepares for division

G1 Phase

The first stage of interphase in the cell cycle, where the cell grows, copies its organelles, and synthesizes proteins and other molecules in preparation for DNA replication

S Phase

The stage in the cell cycle where a cell replicates its DNA, creating two identical sets of chromosomes

G2 Phase

The final stage of interphase in the cell cycle, occurring after DNA replication (S phase) and before mitosis (M phase)

Mitosis

The process where a single eukaryotic cell divided its nucleus to produce two genetically identical daughter cells

Prophase

the first stage of both mitosis and meiosis, where chromatin condense into visible, distinct chromosomes

Metaphase

The stage of cell division (mitosis/meiosis) where condensed chromosomes, each consisting of two sister chromatids, align perfectly along the cell’s equator at an imaginary plane called the metaphase plate, ensuring equal distribution to daughter cells after spindle fibers attach to their kinetochores

Anaphase

The stage of mitosis and meiosis where the replicated chromosomes or homologous chromosomes pairs are separated and pulled to opposite poles of the cell

Telophase

The final stage of mitosis and meiosis, where two new nuclei form at opposite ends of the cell as chromosomes decondense and nuclear envelopes reappear around each set of chromosomes

Cytokinesis

The final stage of cell division where the cytoplasm of a parent cell divides to form two separate daughter cells

G0 Phase

a non-dividing, quiescent (resting) state where cells exit the active cell cycle (G1, S, G2, M) to perform specialized functions, remaining metabolically active but not preparing for or undergoing cell division

Proliferative

Rapid growth and multiplication of cells through cell divsion

Non-proliferative

cell or tissue that is not actively dividing or growing

Chromosome

A thread-like structure made of proteins and a single molecule of DNA that carries genetic information in the form of genes

Chromatid

one of two identical DNA copies (sister chromatids) that make up a single, replicated chromosome, joined at the centromere until separated during cell division to become individual chromosomes in daughter cells

Spindle Apparatus

a dynamic cellular machine made of microtubules that forms during cell division (mitosis/meiosis) to separate sister chromatids, ensuring each new daughter cell gets an identical set of chromosomes

Cyclin

Proteins that regulate the cell cycle by accumulating and degrading at specific times

Cyclin-dependent kinase

An enzyme that together with cyclins, regulates the cell cycle. CDKs are the "engine" of the cell cycle, but they require binding to specific cyclins to become active

Tumor suppressor

A protective gene that normally slows down cell division, repairs DNA, or triggers cell death to prevent tumors

Proto-oncogene/oncogene

A normal gene that promotes cell growth and division, acting as a “go” signal for the cell cycle; a mutated overactive version of a normal cell gene that promotes uncontrolled cell growth and division, often leading to tumor formation and cancer

Cancer

a disease of uncontrolled cell division caused by mutations in genes that regulate the cell cycle, leading to cells that ignore checkpoints and grow into tumors

Apoptosis

the process of programmed cell death, where a cell self-destructs in a highly controlled manner

Checkpoint

a control point in the cell cycle where regulatory proteins check for problems like DNA damage or improper replication before the cell can proceed to the next stage

Mutation

A change in the genetic material (DNA) of an organism