Cell communication and signalling

Membranes

1. Cell/plasma: surrounds the cytoplasm. Continous and selectively permeable. Consists of lipid bilayer in which different types of proteins are embedded. Compartmentalize the cell contents.

2. Endomembranes: within the cell covering the organelles. Compartmentalize processes within the cell

   Also involved in transport of substances the detection of signals and communication between cells

Integral proteins

Segments embedded in plasma membrane.

1. Channel: allows for the passage of inorganic ions by diffusion. Gated.

2. Carrier: allows for the passage of small organic molecules or inorganic molecules by changing its conformation

3. Cell recognition: glycoproteins that recognize cells that are self and those that are foreign

4. Receptor: protein is a specific shape which will only bind to certain molecules to initiate cellular response.

5. Enzymatic: catalyses specific biological reactions

Exocytosis

Form of active transport to move substances out of a cell. Membrane bound secretory vesicles carried to cell membrane to dock and fuse at porosomes (cup-shaped structures) and contents are secreted to the outside- secretion is possible because vesicles transiently fuses with cell membrane

Endocytosis

Form of active transport to move substances into a cell. Material that needs to move in is surrounded by an area of cell of cell membrane, this then buds off inside the cell to form a vesicles containing the ingested material. Include pinocytes, small particles in a fluid and phagocytosis, large particles.

Cell communication and signaling

Ability of a cell to receive, process and transmit signals with its environment and with itself.

Type of signaling

1. Autocrine: cells secretes a hormone/chemical messenger that binds to autocrine receptors on that same cell, leading to changes in the cell itself

2. Juxtacrine: cell-cell or cell-extracellular matrix signaling in multicellular organism

3. Intracrine: cells stimulate itself by production of hormone that regulates intracellular events

4. Endocrine: release of hormones by internal glands of an organism directly into circulatory system, regulating distant target organs

5. Paracrine: signal is applied locally to induce changes in nearby cells, by altering the behavior of those cells

Receptor

Chemical structure composed of protein, that receive and transduce signals (chemical messengers which bind to a receptor and cause a cellar/tissue response)

1. Relay of signal: sends the signal onward

2. Amplification: increases the effect of a signal ligand (a molecule that binds to another)

3. Integration; allows signal to be incorporated into another biochemical pathway

Signaling pathway

1. Reception: cell detects signaling molecule from outside of cell when the chemical signal (ligand) binds to receptor protein on cell surface on inside the cell

2. Transduction: Once signaling nolecule binds to receptor it changes receptor protein in some way, this change initiates process, which each relay molecule in the pathway changes the next molecule in pathway.

3. Response: signal triggers a specific cellular response

Cell junctions

Cellular structures made of multiprotein complexes that provide contact between neighboring cells.

Plants use plasmodesmata for cell-to-cell communication

1. Tight: prevent the passage of substances by acting as a sealant

2. Gap: connect cytoplasm of two cells, allows molecules ions and electrical impulses to directly pass through a regulated gate between cells

3. Adherens: anchor cells through their cytoplasmic actin filament