Topic 3.1, 3.2, 7.5:

Water, Carbs, Lipids and Proteins

IB BIOLOGY

ElementsAtoms form molecules/compoundsBonds: covalent (atoms share electrons) or ionic (atoms give/receive electrons).

H - HydrogenC - Carbon

Na - SodiumCl - Chlorine Methan

e

Sodium ChlorideIons

Elements / Minerals 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)

Water and its properties

POLAR = Oxygen attracts electrons more strongly

Hydrogen BondsThe water molecules attract each other

Hydrogen bonds form (not real bond – strong attraction force)

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

Water propertiesThermal 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 buffer2) 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 and Inorganic Compounds

Organic = all molecules containing carbon found in living systems exceptions: CO2 and carbonates (salt of carbonic acid - CO3

2− - ex: calcium carbonate and carbonated water)Main organic substances (macromolecules):-Carbohydrates-Lipids-Proteins-Nucleic Acids

Inorganic = all substances that are not organic

Carbohydrates Most abundant Short term energy storage General molecular formula (CH2O)n

Basic unit: monosaccharides (fructose, glucose, galactose) Two monosaccharides: disaccharides (maltose, lactose,

sucrose) Anything larger than this: polysaccharides (starch, glycogen,

cellulose)

Monosaccharides

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

DisaccharidesSucrose — common table sugar = glucose + fructose

Lactose — major sugar in milk = glucose + galactose

Maltose — product of starch digestion = glucose + glucose

Polysaccharides 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/Hydrolysis

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

Lipids/FatsGlycerol + 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

FatsSaturated: full of hydrogens – solid at room temperature

Unsaturated: one or more double bonds connecting carbons – liquid at room temperature

FatsCis – 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

Energy contentAnimals use fats for energy storageFat stores lots of calories in a small space - 9Kca/g - against carbs (4Kcal/g)

ProteinsMade of amino acidsContain nitrogenMany functions:-Structural (muscles, collagen, keratin) -Enzymes (metabolism)-Carriers (hemoglobin, albumin)-Antibodies-Hormones (ex. insulin)-Membrane pumps (ATP pumps), receptors, neurotransmitters-Movement (actin, myosin)

Peptide Bondpeptide bond = joins two amino acids