Option B: Biochemistry

sum of all chemical reactions in an organism (necessary to sustain life)

sequences and cycles that metabolic reactions go through

compounds taking part in metabolism

• metabolic reactions involved in building up (i.e. synthesis) • requires energy to carry out • reactants are small molecules (called precursors) • products are large, complex molecules of higher energy e.g. nucleotides –> nucleic acids, amino acids –> proteins, photosynthesis

• metabolic reactions involved in breaking down • releases energy • reactants are larger molecules • products are smaller and energy-poor e.g. breakdown of glucose during cell respiration

• energy obtained from catabolism is used to fuel anabolic reactions • through the use of ATP (adenosine triphosphate) as the intermediary energy carrier

• the metabolic pathways for anabolism and catabolism of a specific substance differ from each other and also involve different enzymes • if they were the same, futile cycles would occur • i.e. stable complex structures would not exist in cells as they would be broken down immediately after synthesis

• compounds with relative molecular masses numbering in the thousands e. g. polysaccharides, proteins, nucleic acids • they can be described by their constituents (monomers) which are covalently bonded

• all biopolymers are condensation polymers • i.e. they are synthesized through condensation reactions • to undergo a condensation reaction, both monomers involved must have 2 functional groups • these reactions are catalysed by enzymes (polymerases)

• reverse of condensation reaction - involves the addition of a H2O unit for every covalent bond broken

• anabolic process used by plants to synthesize energy-rich biomolecules • uses solar energy absorbed using photosynthetic pigments (chlorophyll) • all organisms on Earth are dependent on this process for food, directly or indirectly

• series of redox reactions • water is split into H2 and O (O is the waste product) • H2 is used to reduce CO2 to form glucose • essentially transforms energy-poor CO2 and H2O into glucose

• catabolic process used by all organisms to release energy from energy-rich molecules • essential to life and occurs continuously in every cell • glycolysis –> link reaction –> krebs cycle –> electron transport chain • in anaerobic conditions only glycolysis takes place • in the electron transport chain, cytochromes are reduced and oxidized in succession • the last step of the electron tranport chain involves the reduction of the final electron acceptor, oxygen, to H2O

• photosynthesis: carbon sink, removes carbon from atmosphere • respiration: carbon source, releases carbon to atmosphere

• fibrous proteins - globular proteins

• supports structure/movement • elongated molecules with a dominant secondary structure • insoluble in water

• tools operating on the molecular level (e.g. enzymes, receptors) • compact spherical molecules with a dominant tertiary structure • soluble in water

• keratin: the protective covering in claws/hair/wool - collagen: connective tissue in skin and tendons

• polymerase: catalyses anabolic reactions • insulin: hormone that controls + maintains blood glucose levels • haemoglobin: carries oxygen in the blood

• building blocks of proteins • contains an amino group (NH2) and a carboxyl group (COOH) • called 2-amino acids • all amino acids differ by their variable R group

• R group: hydrocarbon e. g. alanine

• R group: hydroxyl (OH), sulfhydryl (SH), or amide (CONH2) e. g. serine

• R group: amino (NH2) e. g. lysine

• R group: carboxyl (COOH) e. g. aspartic acid