Cell Communication and Signal Transduction

Flashcards covering key vocabulary terms related to cell communication, signaling pathways, and homeostasis.

Cell Communication

The process by which cells communicate with each other, critical for function and survival.

Direct Contact

Cell communication through cell junctions allowing substances to pass between adjacent cells.

Local Regulators

Chemical messengers released by cells that affect nearby target cells through local signaling.

Paracrine Signaling

A form of local signaling where secretory cells release signals to nearby cells.

Synaptic Signaling

Communication in the nervous system where neurons secrete neurotransmitters across a synaptic cleft.

Long Distance Signaling

Communication that involves hormones traveling through the bloodstream or vascular tissue to reach distant target cells.

Transduction

The process of converting an extracellular signal into an intracellular signal.

Reception

The stage at which a ligand binds to its receptor on a target cell.

Signal Transduction Pathway

A series of molecular changes by which a signal on a cell's surface is converted into a specific cellular response.

Negative Feedback

A regulatory mechanism that reduces the output or activity of a system to stabilize it.

Positive Feedback

A regulatory mechanism that increases the output or activity of a system to amplify a response.

Homeostasis

The state of steady internal conditions maintained by living organisms.

Cyclins

Proteins that regulate the cell cycle by activating cyclin-dependent kinases (CDKs).

G1 Checkpoint

The most important checkpoint in the cell cycle that checks cell size, growth factors, and DNA damage.

G2 Checkpoint

A cell cycle checkpoint that ensures DNA replication is complete and DNA is undamaged before mitosis begins.

M Checkpoint (Spindle Checkpoint)

A cell cycle checkpoint that ensures all sister chromatids are correctly attached to the spindle microtubules at metaphase before anaphase begins.

Apoptosis

Programmed cell death that occurs when a cell is damaged beyond repair.

Malignant Tumor

A mass of cancerous cells that can invade other parts of the body.

Metastasis

The spread of cancer cells from one part of the body to another.

Ligand

A molecule that binds specifically to a receptor, initiating a cellular response.

Second Messenger

Small, non-protein, water-soluble molecules or ions that relay a signal from the receptor to target molecules inside the cell.

G-protein Coupled Receptors (GPCRs)

A large family of cell-surface receptors that work with the help of a G protein, often initiating a signal transduction pathway.

Cyclin-Dependent Kinases (CDKs)

Enzymes that, when activated by cyclins, phosphorylate other proteins to drive the cell cycle forward.

Interphase

The period in the cell cycle when the cell grows, copies its DNA, and prepares for cell division (G1, S, and G2 phases).

Proto-oncogenes

Normal genes that promote cell growth and division; mutations can turn them into oncogenes, leading to uncontrolled growth.

Tumor Suppressor Genes

Genes whose products inhibit cell division, repair DNA damage, or initiate apoptosis; mutations can lead to uncontrolled cell growth.

Benign Tumor

A mass of cells that remains at its original site in the body and does not invade other tissues.

S Phase

The phase during Interphase when DNA synthesis (replication) occurs, resulting in duplicated chromosomes.

M Phase (Mitotic Phase)

The phase of the cell cycle that includes both mitosis and cytokinesis, leading to cell division.

Mitosis

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

Cytokinesis

The division of the cytoplasm and its contents to form two separate daughter cells following mitosis.

Growth Factors

External signaling molecules that bind to receptors on the cell surface, promoting cell growth and division.

What is an example of negative feedback?

The regulation of blood glucose levels by insulin and glucagon, where high glucose triggers insulin release to lower it, thus reducing the initial stimulus.

What is an example of positive feedback?

Childbirth contractions, where hormones stimulate stronger contractions, which in turn leads to the release of more hormones until the baby is delivered.

What are the three main components of a G-protein Coupled Receptor (GPCR)?

1. An extracellular ligand-binding domain. 2. Seven transmembrane alpha-helices. 3. An intracellular loop that interacts with a G-protein.

How is a G-protein activated in a GPCR signaling pathway?

Upon ligand binding to the GPCR, the receptor changes conformation, causing the associated inactive G-protein to exchange its GDP for a GTP molecule.

What happens after a G-protein is activated by a GPCR?

The activated G-protein disassociates into an active (\alpha) subunit bound to GTP and a ( \beta\gamma) dimer, both of which can then regulate downstream effector proteins.