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Why is the presence of a membrane so important?
The plasma membrane or cell membrane seperates life from non-life. It is a layer of molecules that surrounds the cell interior and separates it from the external environment.
The plasma membrane serves as a what? It keeps what out of the cell and allows entry of what?
Selective barrier/damaging compounds/compounds needed by the cell
Because the plasma membrane sequesters the approriate chemicals in an enclosed area, reactants collide more frequently-what occurs much more effciently?
the chemical reactions necessary for life
The first cell functioned as a what?
It was responsible for one of the 5 key attributes of life: this is what?
- an efficient and dynamic reaction vessel
- The presence of a barrier that defines the cell and regulate the passages of materials
Lipids are what?
lipid is a catch-term for carbon-containing compounds that are what?
Lipids do dissolve, however, in what?
- "oily" or "fatty" coumpounds
- found in organisms and are largely nonpolar and hydrophobic-meaning that they do not dissolve readily in water. (Water is a polar solvent)
- in liquids consisting of nonpolar organic compounds.
What are hydrocarbons?
Why are hydrocarbons nonpolar?
- molecules that contain only carbon and hydrogen
- Hydrocarbons are nonpolar because electrons are shared equally in C-H bonds- owing to the aproximately equal electronegativity of carbon and hydrogen. This property makes hydrocarbons hydrophobic. Thus the reason lipids do not dissolve in water is that they have a significant hydrocarbon components
What is a lipid consisting of a hydrocarbon chain bonded to a carboxyl group (-COOH) at one end; Used by many organisms to store chemical energy; a major component of animal and plant fats?
Unlike amino acids, nucleotides, and monosaccharides, lipids are characterized by a physical property-which is what?
their solubility instead of a shared chemical structure.
What are the most important type of lipids found in cells?
fats, steroids, and phospholipids
What is composed of three fatty acids that are linked to a three carbon molecule called a what?
B/c of this structure fats are also called Triacyglycerols or triglycerides
How does fat form?
When dehydration reaction occurs b/w a hydroxyl group of glycerol and carboxyl group of a fatty acid.
The glycerol and fatty acid molecule became joined by an ester linkage which is a what?
Fatty acids are not monomers and fats are not polymers.
the covalent bond (type of chemical bond in which 2 atoms share one or more pairs of electrons) formed by a condensation reaction b/w a hydroxyl group (-OH). they join fatty acids to glycerol to form a fat or phospholipid
Steroids are what?
The various steroids groups differ from one another by the functional groups or side groups attached to those rings-shown as an "R-group"
a family of lipids distinguished by the bulky, four-ring structure shown in orange.
What are phospholipids?
The phosphate group is also bonded to a small organic molecule that is charged or polar
Phospholipids with isoprene tails are found in the domain Archea, Phospholipids composed of fatty acids are found in the domains of what? In all three domains of life, Phospholipids are critically important components of what?
- consist of a glycerol that is linked to a phosphate group (PO3_4) and to either two chains of isoprene or two fatty acids
- Bacteria and Eukarya
- the plasma membrane
In addition to storing chemical energy, lipids act as pigments that do what?; serve as signals b/w what?; form waterproof coatings on leaves and skins; and acts as vitamins used in an array of cellular processes.
The most important lipid function however is is what?
- capture or respond to sunlight/cells
- their roles in the plasma membrane
Not all lipids can do what?
Membrane-forming lipids have what kind of region? in addition to the what region found in all lipids?
- form membranes
- polar, hydrophillic region/ non-polar hydrophobic region
The charges and polar bonds in the head region interact with water molecules when a phospholipids is placed in solution. In contrast, the long isoprene or fatty-acid tails of a phospolipid are nonpolar and hydrophobic.
Water molecules cannot form what with the hydrocarbon tails? and do not interact extensively with this part of the molecule.
Compounds that contain both hydrophillic and hydrophobic elements are what?
Phosopholipids are amphipathic; as well as cholesterol.
What is the most important feature of phospholipids biologically?
- amphipathic ("literally dual-symphaty)
- the amphipathic nature-responsible for presence in plasma membranes