Chapter 01 - Biochemistry DAT

• Chemical bonds of molecules are formed by electron interactions.
• Molecules are groups of 2 or more atoms held together by covalent bonds.
• Electronegativity is the ability of an atom to attract electrons Fluorine (F) is the most electronegative atom
• In general, covalent bonds involve two atoms of similar electronegativities Electronegativity difference:Nonpolar covalent: < 0.5Polar covalent: 0.5 - 1.7Ionic: > 1.7
• Ionic bonds involve two atoms of different electronegativities Electronegativity difference:Nonpolar covalent: < 0.5Polar covalent: 0.5 - 1.7Ionic: > 1.7
• Nonpolar covalent bonds involve equal sharing of electrons due to nearly identical electronegativities between two atoms Electronegativity difference:Nonpolar covalent: < 0.5Polar covalent: 0.5 - 1.7Ionic: > 1.7
• Polar covalent bonds involve unequal sharing of electrons due to similar electronegativities between two atoms Electronegativity difference:Nonpolar covalent: < 0.5Polar covalent: 0.5 - 1.7Ionic: > 1.7
• Covalent bonds can be single bonds, double bonds, or triple bonds
• Water is a good solvent because its dipoles break up charged ionic molecules. "Note how the polarity of water allows it to attach to ions:" "Image from OpenStax, CC BY 4.0"
• Water has high specific heat capacity, meaning it usually takes more energy to heat the same amount of water vs. another substance Specific heat of water = 4.18 kJ/mol
• Ice floats because hydrogen bonds in ice are rigid and form a crystal structure Molecules of ice take up more space than the same number of molecules of water (i.e. ice density < water density).
• Water is attracted to like substances via hydrogen bonds, aka cohesion
• Strong cohesion of water allows for high surface tension, which produces phenomena like water bugs walking on water
• Water sticks to things other than water, i.e. adhesion
• A disaccharide is two sugar monomers joined by a glycosidic bond/linkage formed by dehydration "Ex: sucrose. Note the two monomers joined by the glycosidic linkage in the middle"
• sucrose = glucose + fructose
• lactose = glucose + galactose
• maltose = glucose + glucose
• Monosaccharides are classified as alpha or beta based on the orientation of OH on the anomeric carbon (down = alpha, up = beta) "alpha D-glucose (left); beta D-glucose (right)Note the positioning of the OH on the anomeric carbon (carbon connected to two O atoms on the rightmost side). This OH is down (left) and up (right)."
• Polysaccharides are a series of many sugar monomers
• Polysaccharides are broken down via hydrolysis
• Cellulose is a polymer of β-glucose and is found in plant cell walls and wood ""
• Chitin is a polymer of β-glucose containing a nitrogen-containing group and is found in fungal cell walls and insect exoskeletons "left: chitin; right: cellulose"
• Glycogen is a polymer of α-glucose and stores energy in animal cells
• Starch is a polymer of α-glucose and stores energy in plant cells
• Glycogen and starch differ by branching patterns Both are polymers of α-glucose.
• Lipids are hydrophobic molecules and play roles in insulation, energy storage, structure (cholesterol and phoslipids in membrane), and the endocrine system
• Triglycerides (aka triacylglycerols) are three fatty acid chains attached to a glycerol backbone "left: tryglyceride example; right: glycerol"
• Saturated fats do not have double bonds
• Unsaturated fats have double bonds
• Saturated fats are bad for health because they stack densely and form fat plaquesUnsaturated fats are better for health because they stack less densely Double bonds = worse stacking, less dense, better for health
• Phospholipids contain two fatty acids attached to a phosphate group and an R group attached to a glycerol backbone
• Phospholipids are amphipathic, meaning they are both hydrophilic and hydrophobic
• Steroids have three 6-membered rings and one 5-membered ring "General structure of a steroid"
• Examples of steroids are hormones and cholesterol Cholesterol is found in the membrane.
• Waxes are lipids that are esters of fatty acids and monohydroxylic alcohols. They are used as protective coating or exoskeleton.
• Carotenoids are fatty acid chains with conjugated double bounds and six membered rings at each end.Caretonids are pigments in plants and animals. Subgroups include carotenes and xanthophylls.
• Porphyrins have 4 joined pyrrole rings and are often complexed with metals  "Ex: porphyrin heme complexes with Fe in hemoglobin, chlorophyll complexes with Mg1. example of a generic porphryin2. heme B"
• The cytoplasm of adipocytes contains nothing but triglycerides Adipocytes have two categories: white fat cells and brown fat cells
• Glycolipids are like phospholipids; they contain a carbohydrate group in place of a phosphate group "Example of a glycolipid"