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Biochemistry Key Concept: Polarity • If a molecule is created (covalent bonds), the electrons may or may not be evenly distributed – Evenly distributed: nonpolar molecule – Unevenly distributed: polar molecule • Brain check: what about ionic bonds? Keyword: Macromolecule • A macromolecule is a very large molecule (hundreds or thousands of atoms) – Molecule = held together with covalent bonds • There are four groups of macromolecules – – – – Carbohydrates Lipids Amino acids Nucleic acids • Vitamins and minerals are NOT macromolecules, they are small (but still important!) Keyword: Intermolecular Forces • Break down the language! – Inter=between two different things – Molecular=molecule – Force=a push or pull (in this case pull) • The more intermolecular forces between molecules, the more the molecules stick together – Do polar or nonpolar molecules have more intermolecular forces? Polar Molecules • Polar molecules often form hydrogen bonds, a type of intermolecular force • Water is the king of hydrogen bonds, since it has two hydrogens and one oxygen – Makes it have a lot of attractive forces Three questions: • Why is water “sticky” when you can slip on it? • What is a very sticky liquid? • What is a very notsticky liquid? Best Answers: 1) All liquids are slippery to some degree – Also note: ice is only slippery if it has a layer of water on the outside 2) Honey, syrup, molasses: all have sugar in them! 3) Oil, grease: all have lipids which are nonpolar! Sugar (Carbohydrates) • Sugars are carbon molecules with lots of oxygen and hydrogen, so they are also polar molecules • They mix well with water and form many more + attachments – Known as hydrophilic – This is why honey is so sticky! Starch • Starches are made of many individual sugar rings bonded together – Some starches (white bread, white rice, human glycogen, etc) are designed to break apart very quickly – Others (brown rice, whole wheat bread etc) are designed to break apart more slowly • This is why brown carbs are better for you! Carb Complexity • Carbohydrates may be attached in simpler or more complex styles of arrangements – Still the same covalent bonds, but different arrangements of the sugar rings • Cellulose is plant fiber that is made of sugar molecules arranged into an indigestible lattice – This is why cows need 4 stomachs to eat grass Lipids (Fats & Oils) • Lipids are made with carbon and hydrogen – Carbon and hydrogen form a nonpolar bond • Since electron sharing is even, no + and – charges form • This means they do not mix with water – Hydrophobic Common Lipids • Triglycerides are how many living things (including humans) store energy – Contains saturated fats and/or unsaturated fats • Cholesterol is an animal lipid that is used for many chemical processes but not for energy – Can build up and clog arteries in excess • Phospholipids are triglycerides modified to have a phosphate on one end Phospholipid Bilayer • Phospholipids are special because they are mostly hydrophobic but the phosphate head is hydrophilic • This causes the molecules to naturally line up and form a thin layer of oil • This forms the basis of the cell membrane Consider the Following: • Since oils are not sticky (no polar bonds) they don’t stick to glass like water does • Since oil and water don’t mix, how do you get oil off your hands? – Soap! Soaps are chemicals with hydrophobic and hydrophilic parts so they can make oil and water mix (detergent) – The term for this is to emulsify Amino Acids • Amino acids fit together like beads on a chain – Human bodies use 20 different kinds (there are many more) and each kind has a different molecule on its side chain • The order of the amino acids cause the chain to coil up and form a protein Some Protein Structures Nucleic Acids • How do our cells know what order to put the amino acids into? – Our DNA of course! • DNA (Deoxyribose nucleic acid) is a macromolecule that stores information – The order of base pairs (A, T, G, C) codes for amino acids in a sequence! – This process will be covered in chapter 3 Nucleic Acids Structure of a DNA Nucleotide • A nucleotide is a single “letter” of a DNA chain – Contains a base (the “letter), a sugar molecule, and one or more phosphate molecules – The energy is stored in the phosphate molecules • The cell often uses an adenosine molecule with three phosphates to provide energy for chemical reactions – The famous ATP See you Friday! • Also don’t forget the review quiz is online!