Lipids

• Glycerol is an alcohol produced by the hydrolysis of triglycerides.
• Lipids are insoluble in water but soluble in organic solvents such as ether or chloroform.
• A phospholipid's phosphate head is hydrophilic and polar.
• A phospholipid's fatty acid tail is hydrophobic and non-polar.
• Mono-unsaturated fatty acids contain only one double bond in their carbon chain.
• Poly-unsaturated fatty acids contain more than one double bond in their carbon chain.
• Saturated fatty acids have no double bonds between carbon atoms in their chains.
• A phospholipid is a triglyceride in which one of the fatty acid components is replaced by a phosphate molecule.
• A triglyceride is an individual lipid molecule made of a glycerol molecule and three adjoining fatty acids.
• In a triglyceride each fatty acid forms an ester bond with the glycerol molecule in a condensation reaction.
• Triglyceride properties include:

  • a high ratio of C-H bonds : C atoms (= good source of energy)
  • a low mass : energy ratio (lots of energy can be stored in a small space)
  • insoluble (non-polar)
• Phospholipid properties include:

  • a hydrophilic (polar) phosphate head
  • a hydrophobic (non-polar) fatty acid tail
  • forms a lipid bilayer in cell membranes
• A phospholipid bilayer is a double layer of phospholipids that forms a barrier between the aqueous interior of the cell and the aqueous outside environment, allowing the cell control over which water-soluble substances enter and leave it.
• Roles of lipids:

  • protection of delicate organs
  • energy source
  • heat and electrical insulation
  • waterproofing
  • cell membranes
• Similarities and Differences between Phospholipids and Triglycerides:

  • both contain glycerol and fatty acid components
  • both are insoluble in water
  • both are soluble in organic solvents
  • phospholipids contain 2 fatty acids; triglycerides 3
  • phospholipids contain a phosphate group; triglyceride doesn't
  • the third carbon in the glycerol of a phospholipid is rotated 180°
• A short-chain triglyceride would be a liquid at room temperature and a long-chain triglyceride would be a solid.
• On adding ethanol to a suspected lipid and gently stirring, the ethanol will dissolve any present lipids. When the mixture is decanted, added to water and shaken, the lipid and water mix together freely, forming a suspension of small lipid droplets called an emulsion.
• Energy is released from triglycerides when they are oxidised in respiration.
• In animals, triglycerides are found in adipose tissue just beneath the skin. It acts as an excellent heat insulator to help regulate body temperature.
• In plants, triglycerides are found in seeds, where they act as lightweight high-energy stores that the seeds can utilise when they germinate.
• Triglycerides are hydrophobic (non-polar) and insoluble in water so they have no osmotic effect on cells. Their large size means they cannot easily cross membranes.
• A micelle is a sphere of phospholipids which have oriented their tails away from the aqueous environment. A double-layered micelle is referred to as a bilayered micelle.
• The lipid droplets formed as a result of an emulsion prevent light from passing through so the water becomes cloudy/milky-white.
• 𝙏𝙍𝙄𝙂𝙇𝙔𝘾𝙀𝙍𝙄𝘿𝙀𝙎:

  • 3 fatty acids
  • 3 ester bonds
  • no phosphate group
• 𝙋𝙃𝙊𝙎𝙋𝙃𝙊𝙇𝙄𝙋𝙄𝘿:

  • 2 fatty acids
  • 2 ester bonds
  • phosphate group
• Osmosis involves water traveling through a semi-permeable membrane, which can potentially be a cell membrane.
• The cell membrane is semi-permeable, meaning it lets some materials through but not others.
• Increase in volume results in a greater need for surface area as more food needs to enter, more waste needs to be removed, and more metabolic reactions occur in the larger volume.
• A glycoprotein known as CD4 is found on the surface of some of your immune cells and is essential for these immune systems cells to interact with each other and activate.
• The HIV virus uses the CD4 glycoprotein as a way to bind to Helper T cells, which it then can infect.
• Many proteins are found on or in the cell membrane and play major roles.
• Integral proteins go through the membrane and peripheral proteins can sit on them.
• Glycoproteins and glycolipids can identify the cell as belonging to the organism, aiding in self/non-self recognition, which is very important when fighting pathogens.
• Understanding the components of the cell membrane and how those components are involved in recognition and cell signaling is critical to understanding how to fight back against many viral and bacterial diseases.
• Peripheral proteins, like the name suggests, are on the peripheral area of the membrane and generally are not going to go through the membrane.
• Peripheral proteins tend to be more loosely attached since they’re generally not stuck in the membrane and can have an assortment of functions such as acting as enzymes to speed up reactions or attaching to the cytoskeleton structures to help with cell shape.
• Cholesterol in the cell membrane is critical for keeping temperatures from dropping and for keeping phospholipids from becoming too packed or too fluid in warm temperatures.
• Both protein types can have carbohydrates bound to them, which can then make them considered a glycoprotein or glycolipid.
• Glycoproteins and glycolipids can also be involved in many kinds of cell signaling.
• The Fluid Mosaic Model is often how we describe the cell membrane, arranging many small pieces together to make some larger piece.