Related Concept Videos

SN1 Reaction: Mechanism02:25

SN1 Reaction: Mechanism

Kinetic studies of ionization of a tertiary halide in a protic solvent suggest that only the substrate participates in the rate-determining step (slow step). The nucleophile is involved only after the slowest step. The SN1 reaction takes place in a multiple-step mechanism. 
Firstly, the haloalkane ionizes to generate a carbocation intermediate and a halide ion. This heterolytic cleavage is highly endothermic with large activation energy. The ionization of the substrate, facilitated by a...
14.4K
Structure of Cadherins01:25

Structure of Cadherins

The cadherins were one of the first cell adhesion molecules discovered; the term “cadherins”   is based on their calcium-dependent adhering properties. The first cadherins discovered on the epithelial, neuronal, and placental cells were named E-cadherin, P-cadherin, and N-cadherin, respectively. These classical cadherins share sequence and structural similarities. Other cadherins, including those involved in cell signaling, are grouped into non-classical cadherins. This...
4.9K
Receptor Downregulation in MVBs01:15

Receptor Downregulation in MVBs

Multivesicular bodies (MVBs) are mature endosomes that sort ubiquitinated proteins and then fuse with lysosomes to degrade the sorted proteins. Epidermal growth factor (EGF) and its receptor (EGFR) form a complex that can be internalized through endocytosis, sorted into an MVB, and later degraded.
The EGFR can initiate signaling pathways that  lead to cell proliferation, migration, and differentiation. Overexpression of EGFR  stimulates cells to proliferate. Excessive  EGFR...
2.8K
Cadherins in Tissue Organization01:19

Cadherins in Tissue Organization

The cadherins are a superfamily of cell adhesion molecules comprising over 180 variants, with specific tissues expressing a particular combination of cadherin types. Cadherins generally exhibit homophilic binding; i.e., cadherins on one cell bind to cadherins of the same or closely related type on another cell. Thus, cells of the same type have a specific affinity to bind to each other and sort themselves into clusters to form tissues.
Cell Sorting During Development
Cell sorting plays an...
4.3K
Cell Specific Gene Expression01:58

Cell Specific Gene Expression

Multicellular organisms contain a variety of structurally and functionally distinct cell types, but the DNA in all the cells originated from the same parent cells. The differences in the cells can be attributed to the differential gene expression. Liver cells, whose functions include detoxification of blood, production of bile to metabolize fats, and synthesis of proteins essential for metabolism, must express a specific set of genes to perform their functions. Gene expression also varies with...
16.6K
Preparation of 1° Amines: Hofmann and Curtius Rearrangement Mechanism01:26

Preparation of 1° Amines: Hofmann and Curtius Rearrangement Mechanism

The Hofmann and Curtius rearrangement reactions can be applied to synthesize primary amines from carboxylic acid derivatives such as amides and acyl azides. In the Hofmann rearrangement, a primary amide undergoes deprotonation in the presence of a base, followed by halogenation to generate an N-haloamide. A second proton abstraction produces a stabilized anionic species, which rearranges to an isocyanate intermediate via an alkyl group migration from the carbonyl carbon to the neighboring...
4.1K