Amino acids

• There are 20 different amino acids that are commonly found in proteins.
• Some of these proteins are channel proteins, which allow specific molecules to pass through the plasma membrane.
• The main organelles found in all eukaryotic cells include the nucleus, which contains the genetic information that governs the functioning of the cell, and the cell membrane, also known as the plasma membrane, which defines the cell contour and allows communication between cells and exchanges.
• The nucleus is bound by a nuclear envelope formed by two membranes: an outer membrane and an inner membrane, each one made up of a phospholipid bilayer.
• The double membrane of the nucleus is pierced with nuclear pores that allow the exchange of molecules between the nucleus and cytoplasm.
• Inside the nucleus, there is a fluid in which bathes the DNA.
• The plasma membrane, also known as the cell membrane, is the main organelle found in all eukaryotic cells.
• Under an electron microscope, the plasma membrane appears to be composed of three layers: two thick sheets and one clear sheet.
• The plasma membrane consists of a phospholipid bilayer (40%) in which some proteins (60%) are attached.
• Phospholipids are composed of a polar hydrophilic head and an non polar hydrophobic body (2 fatty acid chains).
• All cells are surrounded by a cell membrane, the latter is constituted mainly of phospholipids which is a specific type of lipids.
• Lipids are hydrophobic compounds.
• We distinguish three families of lipids: phospholipids which is an essential component of plasma membranes, cholesterol which is used in the synthesis of steroids, certain hormones and it is also a component of cell membranes, and triglycerides which are molecules that allow to store energy long term.
• Phospholipids are structural molecules (cell membranes).
• Cholesterol, a steroid lipid, is used in the synthesis of some steroid hormones, such as testosterone and estrogen.
• Proteins are incorporated into the membrane.
• In the cell membrane, cholesterol maintains the fluidity and increases the stability of the membrane.
• Phospholipids make the cell membrane amphipathic with a hydrophilic region and a hydrophobic region.
• The fatty acids are hydrocarbon chains with a carboxyl group (-COOH).
• The hydrocarbons chains of the fatty acids are organic molecules consisting of only carbon and hydrogen.
• Many organic molecules, such as fats, have hydrocarbon components.
• Hydrocarbons can undergo reactions that release a large amount of energy.
• Lipids are energetic substances, providing (identical to the initial weight) x 2 more energy than glucose.
• A major function of fats is energy storage.
• Lipids also serve as insulation against the cold or shock absorber to certain organs such as the kidneys or liver.
• Phospholipids are constituted of a glycerol to which is attached two fatty acids and a phosphate (phosphoric acid) with a polar group, which is hydrophilic.
• Humans and other mammals store their fat in adipose cells.
• Adipose tissue also cushions vital organs and insulates the body.
• Unsaturated fatty acids are mainly found in vegetable oils or fish oils, whereas saturated fatty acids are found in animal fat.
• Triglycerides are constituted of a glycerol to which is attached three fatty acids.