Gene Expression

ERK is a MAP kinase that activates translation when it is phosphorylated. ERK phosphorylates MNK1, which in turn phosphorylates eIF-4E, an elongation initiation factor that, with other initiation factors, is associated with mRNA. When eIF-4E becomes phosphorylated, the mRNA unfolds, allowing protein synthesis in the nucleus to begin. Source: OpenStax Biology 2e OpenStax Biology 2e … Continue reading Gene Expression

Signaling Molecules

Steroid hormones have similar chemical structures to their precursor, cholesterol. Because these molecules are small and hydrophobic, they can diffuse directly across the plasma membrane into the cell, where they interact with internal receptors. Source: OpenStax Biology 2e OpenStax Biology 2e Small Hydrophobic Ligands Small hydrophobic ligands can directly diffuse through the plasma membrane and … Continue reading Signaling Molecules

Methods of Intracellular Signaling

In protein phosphorylation, a phosphate group (PO4 -3) is added to residues of the amino acids serine, threonine, and tyrosine. Source: OpenStax Biology 2e OpenStax Biology 2e The induction of a signaling pathway depends on the modification of a cellular component by an enzyme. There are numerous enzymatic modifications that can occur, and they are recognized … Continue reading Methods of Intracellular Signaling

Binding Initiates a Signaling Pathway

The epidermal growth factor (EGF) receptor (EGFR) is a receptor tyrosine kinase involved in the regulation of cell growth, wound healing, and tissue repair. When EGF binds to the EGFR, a cascade of downstream events causes the cell to grow and divide. If EGFR is activated at inappropriate times, uncontrolled cell growth (cancer) may occur. … Continue reading Binding Initiates a Signaling Pathway

Intracellular or Cytoplasmic Receptors

Hydrophobic signaling molecules typically diffuse across the plasma membrane and interact with intracellular receptors in the cytoplasm. Many intracellular receptors are transcription factors that interact with DNA in the nucleus and regulate gene expression. Source: OpenStax Biology 2e OpenStax Biology 2e Internal receptors, also known as intracellular or cytoplasmic receptors, are found in the cytoplasm … Continue reading Intracellular or Cytoplasmic Receptors

Forms of Chemical Signaling

In chemical signaling, a cell may target itself (autocrine signaling), a cell connected by gap junctions, a nearby cell (paracrine signaling), or a distant cell (endocrine signaling). Paracrine signaling acts on nearby cells, endocrine signaling uses the circulatory system to transport ligands, and autocrine signaling acts on the signaling cell. Signaling via gap junctions involves … Continue reading Forms of Chemical Signaling