The Chemistry of Life

Elements of Life Living things are comprised of molecules which are made of different combinations of atoms 4 most common elements: carbon, hydrogen, oxygen and nitrogen Other elements are vital as well but less common

Structure of Water Almost all cells have water within and around them The properties of water depend on its structure:

hydrogen and oxygen atoms are held together by a polar covalent bond oxygen pulls the hydrogen’s electrons towards itself, giving the hydrogen end of the molecule a positive charge, and the oxygen end a negative charge

Properties of Water the attraction between water molecules (H + and O -) gives them many different properties

Thermal Properties high specific heat- water can absorb or give off large amounts of heat without changing the temperature much helps living things regulate temperature high heat of vaporization- water absorbs a lot of heat as it evaporates organisms use to cool themselves (sweat)

Cohesive Properties cohesion- when molecules of the same type are attracted to each other examples: water droplets surface tension

Solvent Properties water is an excellent solvent of other polar molecules solvents dissolve other substances into a solution this makes water a good “medium” for reactions within the cell

Common Aqueous Solutions cytoplasm- fluid inside the cell, location of glycolysis and protein synthesis

nucleoplasm- fluid inside nuclear membrane, location for DNA replication and transcription

stroma- fluid inside chloroplast membrane, location of some parts of photosynthesis

Water as a Transporter water can carry dissolved substances plants: xylem carries water and dissolved minerals up through the plant phloem transports dissolved sugars from the leaves to the rest of the plant

animals: blood is a common transport medium in animals, is mostly water common blood solutes include: glucose, amino acids, fibrinogen, hydrogencarbonate ions

Organic Molecules

molecules containing carbon historically thought to include only molecules that were synthesized by living organisms (have been exceptions since then) common examples: carbohydrates, lipids, proteins, and nucleic acids

Biomolecule Components categorycomponentsexamples carbohydrates monosaccharides glucose, galactose proteinsamino acidsenzymes, antibodies lipids glycerol and fatty acids triglycerides, phospholipids nucleic acidsnucleotidesDNA, RNA

Carbohydrates may be sugars (monosaccharides and disaccharides) or starches (polysaccharides) generally 5 or 6 carbon structures (rings or linear formats)

Important Carbohydrates in Animals NameTypeFunction glucosemonosaccharide chemical fuel for cellular respiration (energy production) lactosedisaccharide makes up some of the solutes in milk glycogenpolysaccharide stores glucose in liver and muscles

Important Carbohydrates in Plants NameTypeFunction fructosemonosaccharide found in many fruits sucrosedisaccharide “table sugar” transported from leaves to other locations in the plant cellulosepolysaccharide one of the primary components of the plant cell wall

Lipids triglycerides- fats(solid) and oils (liquid) structure:

Functions of Lipids efficient at storing energy (stores about twice as much chemical energy as an equal amount of carbohydrate) important for thermal insulation phospholipids make up the cell membrane

Building and Breaking Organic Molecules when food is consumed, our bodies break it into smaller pieces (hydrolysis) these pieces are then used for energy or built into new molecules (condensation)

Hydrolysis Reactions require a molecule of water break molecules apart may break up carbohydrates, lipids, or proteins

Hydrolysis Examples disaccharide broken to 2 monosaccharides lactose + water --> glucose +galactose polysaccharide broken to many monosaccharides starch + many waters --> many glucose triglyceride broken to glycerol and fatty acids triglyceride + 3 waters --> glycerol + 3 fatty acids polypeptide (protein) to amino acids protein + many waters --> many amino acids

Condensation Reactions release a molecule of water forms larger molecules opposite of hydrolysis

Condensation Examples amino acids built into a polypeptide many amino acids --> protein + many waters or reverse the reaction arrow on any of the previous hydrolysis examples

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