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Revision notes on 5.1.3 Cell Signalling for the OCR A Level Biology syllabus, written by the Biology experts at Save My Exams.
- Paracrine Signaling
- Autocrine Signaling
- Endocrine Signaling
- Direct Signaling
- Internal Receptors
- Cell-Surface Receptors
- Small Hydrophobic Ligands
- Water-Soluble Ligands
Signals that act locally between cells that are close together are called paracrine signals. Paracrine signals move by diffusion through the extracellular matrix (Figure 9.2). These types of signals usually elicit quick responses that last only a short amount of time. In order to keep the response localized, paracrine ligands are usually quickly de...
When a cell responds to its own signaling molecule, it is called autocrine signaling (auto = “self”). Autocrine signaling often occurs with other types of signaling. For example, when a paracrine signal is released, the signaling cell may respond to the signal along with its neighbors (Figure 9.2). Autocrine signaling often occurs during early deve...
Signals from distant cells are called endocrine signals, and they originate from endocrine cells. (In the body, many endocrine cells are located in endocrine glands, such as the thyroid gland, the hypothalamus, and the pituitary gland.) These types of signals usually produce a slower response but have a longer-lasting effect. The ligands released i...
Gap junctions in animals and plasmodesmata in plants are connections between the plasma membranes of neighboring cells. These water-filled channels allow small signaling molecules to diffuse between the two cells. Small molecules, such as calcium ions (Ca2+), are able to move between cells, but large molecules like proteins and DNA cannot fit throu...
Internal receptors, also known as intracellular or cytoplasmic receptors, are found in the cytoplasm of target cells and respond to hydrophobic ligand molecules that are able to travel across the plasma membrane. Once inside the cell, many of these molecules bind to proteins that act as regulators of mRNA synthesis (transcription) to mediate gene e...
Cell-surface receptors, also known as transmembrane receptors, are integral proteins that bind to external signaling molecules. These receptors span the plasma membrane and perform signal transduction, in which an extracellular signal is converted into an intercellular signal. (Figure 9.5). Because cell-surface receptor proteins are fundamental to ...
Small hydrophobic ligands, also called lipid-soluble ligands, can directly diffuse through the plasma membrane and interact with internal receptors. Important members of this class of ligands are the steroid hormones. Steroids are lipids that have a hydrocarbon skeleton with four fused rings; different steroids have different functional groups atta...
Since water-soluble ligands are polar, they cannot pass through the plasma membrane unaided. Sometimes they are too large to pass through the membrane at all. Instead, most water-soluble ligands bind to the extracellular domain of cell-surface receptors (see Figure 9.5). This group of ligands is quite diverse and includes small molecules, peptides,...
Deductive reasoning is a form of logical thinking that uses a general principle or law to forecast specific results. From those general principles, a scientist can extrapolate and predict the specific results that would be valid as long as the general principles are valid.
Dec 18, 2016 · AP Biology 4.1 - Cell Communication. This section of the AP Biology curriculum focuses on the many different ways that cells communicate. We’ll start by taking a look at the process of signal transduction.
