Chemistry of Life Essential elements and water

Elements of living things Every living thing is made of – atoms are the smallest part of an element – Atoms of different elements group together to form – If an atom loses or gains an electron it becomes charged =

– 99% of living matter consists of four elements – Carbohydrates: carbon, oxygen, hydrogen – Lipids: carbon, oxygen, hydrogen – Proteins: consist of amino acids that contain carbon, oxygen, hydrogen and nitrogen

Roles of essential elements Trace elements also exist in the body ElementPlantsAnimalsProkaryotes Sulphur In some amino acids and proteins Calcium Cell wall formation between dividing plants Co-factor for certain enzymes In bone Reacts in muscle fiber contraction Cofactor for certain enzymes Helps with heat resistance in of bacterial endospores Co-factor in certain enzymes Phosphorus Phosphate groups in ATP Iron In cytochromes – electron transport molecule In cytochromes and hemoglobin In cytochromes Sodium Sodium potassium pump – part of transporting molecules across the cell membrane Sodium potassium pump – Sending nerve impulses Sodium potassium pump to transport molecules

Water is an important molecule for life Plants = 65 – 95% water Animals = 80% water

Water Molecule Unique structure that gives water some interesting characteristics Consists of two hydrogen atoms and one oxygen atom – they share valence electrons

Hydrogen atoms spend most of their time around Hydrogen atoms are offset giving one side of the molecule a slight charge and the other side the opposite charge – it is a molecule *Annotate the diagram to show which end is positive and negative

Water forms hydrogen bonds – an attraction to other positive and negative charges – Weak bond *Hydrogen bonds give water unique properties

Thermal Properties Water has high specific heat – A lot of heat energy is needed to raise the temperature of water Temperature is the measure of how quickly molecules are moving in a substance Hydrogen bonds must be broken before water molecules can move faster Lakes and ponds don’t change temperature quickly

Evaporation and Heat Loss Hydrogen bonds keep water from vaporizing (evaporating) easily – When organisms evaporate water (transpiration or sweating), heat energy is transferred to the water molecule and carried off in water vapor, cooling the organism

Heat Energy and Freezing A lot of heat energy must be removed from water to turn it to ice Water in the environment and in cells are

Density of Ice Ice is less dense than water: different from all other materials – Insulates freezing lakes and allows life to thrive under the surface in freezing temps.

Cohesive and Adhesive Properties Cohesion: water sticks to itself through hydrogen bonds – Responsible for surface tension

Adhesion: water sticks to other charged surfaces through Water can climb narrow tubes necessary to bring water to the uppermost limbs of plants

Solvent Properties Water is a powerful solvent of polar substances – Ionic substances like sodium chloride (Na + Cl - ) – Organic molecules (carbon containing molecules that are found in living things) that have ionized (charged) groups

Transparency Water is transparent Light can penetrate water allowing aquatic photosynthetic plants