Lipids to Cell Membrane

• Fatty acids consist of a hydrophobic hydrocarbon chain and a hydrophilic carboxyl group, and are amphipathic.
• Saturated fatty acids contain only carbon-carbon single bonds and are relatively straight molecules.
• Unsaturated fatty acids contain carbon-carbon double bonds which cause kinks in the molecule.
• Triglycerides consist of one glycerol molecule bonded with three fatty acid molecules through ester bonds formed through condensation reactions, and are hydrophobic.
• Phospholipids consist of one glycerol molecule bonded with two fatty acid molecules at carbon 1 and 2 and one phosphate group at carbon 3.
• Phospholipids are amphipathic due to the hydrophilic head and hydrophobic tail.
• Phospholipids with unsaturated fatty acids allow the phospholipids bilayer to be more fluid as kinks prevent close packing.
• Steroids consist of 3 six-membered rings and 1 five-membered ring. An example is cholesterol, with a hydroxyl group connected to the steroidal ring structure and a short hydrocarbon tail.
• Cell membrane is described as a fluid mosaic model as phospholipids and membrane proteins can diffuse freely within the bilayer, and proteins are randomly scattered along the phospholipids.
• The cell membrane is held together by hydrophobic interactions and consist of a hydrophilic phosphate head facing outwards and hydrophobic tails facing inwards towards each other to create a hydrophobic core.
• The cell membrane consists of phospholipids, steroids like cholesterol, glycolipids, and membrane proteins.
• Cholesterol in the cell membrane regulates membrane fluidity by preventing close packing of hydrocarbon chains of phospholipids in low temperatures and restraining the movement of phospholipids at high temperatures.
• Membrane proteins consist of integral proteins, which are deeply embedded in the hydrophobic core, and peripheral proteins, which are loosely bound onto the membrane surface.
• Simple diffusion is the net movement of molecules down a concentration gradient, molecules that are small and non-polar pass through the cell membrane via simple diffusion.
• Facilitated diffusion is the movement of molecules down a concentration gradient facilitated by proteins, because proteins enable molecules to move across the membrane without having to interact directly with the hydrophobic bilayer core. This allows polar, charged molecules, and ions to pass through.
• Channel proteins have a pore and carrier proteins are proteins that bind to the surface and changes shape to transport molecules.
• The higher the temperature, the higher the kinetic energy of the molecules, resulting in a higher rate of diffusion.
• Osmosis is the net movement of water molecules from a region of higher water potential to a region of lower water potential through aquaporins.
• Isotonic solutions have the same water potential as the cytoplasm.
• Hypertonic solutions have a lower water potential than the cytoplasm, which means it is more concentrated.
• Hypotonic solutions have a higher water potential than the cytoplasm, which means it is less concentrated.
• In isotonic solutions, animal cells are normal, while plant cells become flaccid.
• In hypotonic solutions, animal cells become lysed, while plant cells are turgid.
• In hypertonic solutions, animal cells undergo crenation and shrivels, while plant cells become plasmolyzed.
• Active transport is the movement of ions or molecules against a concentration gradient using energy.
• Vesicular transport involves endocytosis and exocytosis.
• Endocytosis is when a substance is taken into the cell by the plasma membrane and bud off from the plasma membrane to form a vesicle containing the substance inside the cell.
• Exocytosis is the fusion of the vesicle membrane and plasma membrane to release the contents in the vesicle into the surroundings.
• Large substances like enzymes use vesicular transport to travel through the cell membrane.
• Small and polar molecules like oxygen and carbon dioxide use simple diffusion.
• Large and polar molecules like glucose use facilitated diffusion.
• Small and charged molecules like charged ions use active transport.