IB Biology: Level 9 - Intro to Molecular Biology 2.1

• explains living processes in terms of the molecules involved • reductionist approach • to work out the structure of organic molecules which make up living things • e.g. DNA, RNA, proteins, carbohydrates, lipids • understanding structure leads to understanding function • how molecules interact with each other; biochemical pathways to form new substances and break down others • perhaps cannot yet explain emergent properties when all molecules are combined

• vitalism stated that living molecules cannot be made artificially • urea discovered in 1720s in urine • nitrogen containing compound • waste product of protein breakdown • however, was artificially synthesized in 1800s • therefore, organic molecules from living things can be synthesized artificially

• carbon can form 4 covalent bonds; • therefore can become the backbone of molecules • form chains • ring structures • link together • form double bonds with itself • can bond with just one atom like hydrogen, or multiple different ones • giving a huge range of properties for organic molecules in living things

Most common in living organisms are Carbon, Hydrogen and Oxygen, then nitrogen. Carbon COxygen, OHydrogen, HNitrogen, N

Living organisms require CHONS plus calcium, phosphorus, iron and sodium and other elements

Carbohydrates: - Composed of carbon, hydrogen and oxygen -ratio of 2 hydrogen to one oxygen atom - hence the name carbohydrate Lipids: - broad class of molecules that are insoluble in water - including steroids, waxes, fatty acids, triglycerides - mainly made of carbon, hydrogen and oxygen, though not a fixed ratio - often in long chains - e.g. fatty acids or ring shapes - e.g. steroids Proteins: - made of one or more chains of amino acids - contain carbon, hydrogen, oxygen, nitrogen and sulphur (only 2 of twenty); Nucleic acids- subunit called a nucleotide - contain carbon, hydrogen, oxygen, nitrogen and phosphorous - two types, RNA (single stranded) and DNA (double stranded)

• Ring structure • but! 6th member of the ring is actually oxygen in top right carbon 3 has OH sticking up, all others are sticking down

Same as alpha BUT has 1st carbon OH group going down, as well as carbon 3

• 5 carbon molecule • pentagon shape • oxygen is a top, not carbon • formula is C5 H10 O5 • OHs for 1 and 5 point up, 2 and 3 point down

• Long chain of C and H, acid group at end with COOH structure • no polar bonds • therefore non-polar and hydrophobic • e.g. phospholipid tails

• NH2 group at one end, COOH group at other • R group (which is actually usually C and other atoms) at top • meaning variable group (could be CH3, could be CH2CH3, depending on the amino acid)

• the web of enzyme catalyzed reactions - sum of all the reactions • most take place in cytoplasm -involve many steps • eg. A-B-C-D, where each step is catalyzed by a different enzyme

• synthesis of complex molecules • from simpler ones • e.g. protein synthesis from amino acids • DNA from nucleotides • photosynthesis of glucose from water and carbon dioxide • starch from glucose

• breakdown of large complex molecules into simpler ones • release energy • which can be captured in the form of ATP • e.g. cell respiration where glucose is broken down • digestion of starch into glucose molecules