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Phospholipids [1] are a class of lipids whose molecule has a hydrophilic "head" containing a phosphate group and two hydrophobic "tails" derived from fatty acids, joined by an alcohol residue (usually a glycerol molecule). Marine phospholipids typically have omega-3 fatty acids EPA and DHA integrated as part of the phospholipid molecule. [2]
Other phospholipids. There are many other phospholipids, some of which are glycolipids. The glycolipids include phosphatidyl sugars where the alcohol functional group is part of a carbohydrate. Phosphatidyl sugars are present in plants and certain microorganisms. A carbohydrate is very hydrophilic due to the large number of hydroxyl groups present.
This system describes how bones are connected to other bones and muscle fibers via connective tissue such as tendons and ligaments. The bones provide stability to the body. Muscles keep bones in place and also play a role in the movement of bones. To allow motion, different bones are connected by joints.
A special kind of protein, called apolipoprotein, is embedded in the outer shell, both stabilising the complex and giving it a functional identity that determines its role. Plasma lipoprotein particles are commonly divided into five main classes, based on size, lipid composition, and apolipoprotein content: HDL , LDL , IDL , VLDL and chylomicrons .
Theodore Gobley (1847) discovered phospholipids in mammalian brain and hen egg, called by him as "lecithins". Thudichum discovered in human brain some phospholipids , glycolipids (cerebroside) and sphingolipids (sphingomyelin). [9] The terms lipoid, lipin, lipide and lipid have been used with varied meanings from author to author. [15]
Like phospholipids, these fatty acid derivatives have a polar head and nonpolar tails. [5] Unlike phospholipids, sphingolipids have a sphingosine backbone. [10] Sphingolipids exist in eukaryotic cells and are particularly abundant in the central nervous system. [7] For example, sphingomyelin is part of the myelin sheath of nerve fibers. [11]
The sarcolemma (sarco (from sarx) from Greek; flesh, and lemma from Greek; sheath), also called the myolemma, is the cell membrane surrounding a skeletal muscle fibre or a cardiomyocyte. [ 1 ] [ 2 ] It consists of a lipid bilayer and a thin outer coat of polysaccharide material ( glycocalyx ) that contacts the basement membrane .
Diagram of skeletal muscle fiber structure. Skeletal muscle cells are the individual contractile cells within a muscle and are more usually known as muscle fibers because of their longer threadlike appearance. [10] Broadly there are two types of muscle fiber performing in muscle contraction, either as slow twitch or fast twitch .