TOPIC 3.1

Chemical Elements and Water

3.1.1 Most Frequently Occurring Elements

• Oxygen - 65%• Carbon - 19%• Hydrogen - 10%• Nitrogen - 3%• Carbohydrates and lipids composed of C, H

and O• Proteins composed of C, H, O, N and some

amino acids contain S (cysteine)

Bonds Between Atoms• Element = pure substances that cannot be broken

down further• Compound = two or more elements which are

chemically combined• Covalent bonds = atoms share electrons ex. H2O• Ionic bonds = atoms gain or lose electrons ex. NaCl

(the atoms become + or – ions)• Hydrogen bonds = weak polar bonds ex. Between

the bases in DNA• Peptide bonds = bonds between amino acids to

form polypeptides

3.1.2Other Elements Needed by Living Organisms

• Sulfur (sulphur)• Calcium• Phosphorus• Sodium• Iron

3.1.3One Role for Each Element in 3.1.2

Element Role in Prokaryotes Role in Plants Role in Animals

Sulfur Chemosynthesis- using sulfur as their source of energy

Produce amino acids which are part of some enzymes and proteins

Produce amino acids which are part of some enzymes and proteins

Phosphorus Part of ATP and DNA

Part of ATP and DNA Part of ATP and DNA

Calcium Needed to maintain cell structure and movementCo-factor in some enzymes

Component of cell walls and cell membranesCo-factor in some enzymes

Makes our bones hard and strongNeeded in release of neurotransmitters to transmit nerve impulsesCo-factor in some enzymes

Iron In cytochromes In cytochromesNeeded for the formation of chlorophyll

Component of hemoglobin in red blood cells- needed to transport oxygen

Sodium Indirectly helps move flagellum

In some plants helps bind CO2 for photosynthesis

Involved in action potential in neurons- Na/K pumpCo-transport of glucose

3.1.4Draw and Label Diagram of Water Molecules

Hydrogen bonds are weak polar bonds

3.1.5Thermal, Cohesive and Solvent Properties of H2O

• Cohesive Properties = the attraction forces between molecules of the same kind– Used for transport in plants (capillary action)

• Thermal properties = high specific heat and high heat of vaporization– High specific heat = H2O requires a lot of E to warm up

and gives off a lot of E when cooled down (blood can carry heat to colder places in our body; your nose gets red when you are cold)

– High heat of vaporization = H2O requires a lot of E to change from a liquid to a gas (sweating- evaporation has a cooling effect)

• Solvent properties = water is polar and will dissolve many polar solutes– Important for transport• In plants water transports minerals and sugars• In animals blood transports oxygen, carbon dioxide,

glucose, amino acids, fibrinogen (important protein involved in blood clotting)

– Important medium for metabolic reactions• In plants – fluid inside chloroplast for light-independent

reactions of photosynthesis• In animals – fluid inside nuclear membrane where DNA

replication and transcription take place