IB BIOLOGY

Atoms form molecules/compounds Bonds: covalent (atoms share electrons) or ionic (atoms give/receive electrons). H - Hydrogen C - Carbon Na - Sodium Cl - Chlorine Methane Sodium Chloride Ions

Most frequent elements: Carbon, Hydrogen, Oxygen and Nitrogen Other elements: - Sulfur (S): proteins/enzymes, plant growth - Calcium (Ca): teeth, bones, cell wall component, muscle and nerve function - Sodium (Na + ): water balance (osmoregulation), muscle contraction, nervous impulse - Potassium (K + ): nervous impulse - Iodine (I): thyroid hormones - Phosphorus (P): plant growth, bones/teeth, nucleic acids - Iron (Fe): needed for chlorophyll formation /photosynthesis, red blood cells (hemoglobin)

POLAR = Oxygen attracts electrons more strongly

The water molecules attract each other Hydrogen bonds form (not real bond – strong attraction force)

Transparent: allows plants/algae to survive under water Strong cohesion forces (polar molecule) = high surface tension (force between molecules at surface) = insects can walk on it/water goes from roots to leaves Good solvent for polar molecules = good transport medium (ex. blood, plants) + medium for chemical reactions

Thermal properties (due to high specific heat, heat of fusion/vaporization) Consequences: 1) can absorb larger amounts of energy and still remain liquid. Ex: large body of water can act as a buffer 2) coolant effect = water absorbs large amounts of heat and cools the body (sweat) Ice floats, protecting the water below from freezing, allowing organisms to survive

Organic = all molecules containing carbon found in living systems exceptions: CO 2 and carbonates (salt of carbonic acid - CO 3 2− - ex: calcium carbonate and carbonated water) Main organic substances (macromolecules): - Carbohydrates - Lipids - Proteins - Nucleic Acids Inorganic = all substances that are not organic

Most abundant Short term energy storage General molecular formula (CH 2 O) n Basic unit: monosaccharides (fructose, glucose, galactose) Two monosaccharides: disaccharides (maltose, lactose, sucrose) Anything larger than this: polysaccharides (starch, glycogen, cellulose)

Glucose: one of main products of photosynthesis, starts cellular respiration - cell uses it as a source of energy Galactose: sugar in milk Fructose: sugar found in honey, fruits, vegetables Ribose/Deoxyribose: RNA/DNA structure

Sucrose — common table sugar = glucose + fructose Lactose — major sugar in milk = glucose + galactose Maltose — product of starch digestion = glucose + glucose

Starches : plant storage (excess glucose) - before starches can enter (or leave) cells, they must be digested. The hydrolysis of starch is done by an enzyme called amylase. Glycogen : animals storage (excess glucose). -The liver and skeletal muscle are major deposits of glycogen. Cellulose : plant structure (cell wall). Probably the single most abundant organic molecule in the biosphere. (fibers – paper, cotton) Starch grains in potato cells Cellulose fibers

Condensation: 2 molecules are joined together + loss of 1 water molecule Hydrolysis: water helps break two units (monomers)

Glycerol + fatty acid chains Large number of C - H bonds = non-polar molecules. Insoluble in water Functions: - Long term energy storage - Thermal insulation (Arctic animals) - Major component of the cell membrane The fatty "tail" is non-polar (Hydrophobic) The phosphate "head" is a polar (Hydrophilic) phospholipid

Saturated: full of hydrogens – solid at room temperature Unsaturated: one or more double bonds connecting carbons – liquid at room temperature

Cis – Trans - Oil for frying causes some of the cis bonds to convert to trans bonds. Fatty acids with trans bonds are carcinogenic. All steroids (testosterone, estrogen, progesterone, cortisone…) and Vitamin D need cholesterol to be made. Cholesterol = controls how fluid the cell membrane will be

Animals use fats for energy storage Fat stores lots of calories in a small space - 9Kca/g - against carbs (4Kcal/g)

Made of amino acids Contain nitrogen Many functions: - Structural (muscles, collagen, keratin) - Enzymes (metabolism) - Carriers (hemoglobin, albumin) - Antibodies - Hormones (ex. insulin) - Membrane pumps (ATP pumps), receptors, neurotransmitters - Movement (actin, myosin)

peptide bond = joins two amino acids