New Quarter – New Unit!  Biochemistry Think back. How do elements connect?

Chemical elements & water

Elements, atoms, & molecules Living organisms are made of 25 chemical elements Elements are the basic chemical units that cannot be broken apart by typical chemical processes There are 92 naturally occurring elements 25 are required by living organisms 4 make up 96.3 of the human body

Chemical elements in living things 96% of most living things are made up of oxygen, carbon, hydrogen and nitrogen. -These constitute the main ingredients of proteins, sugars and fats. 4% is made up of elements including calcium, phosphorus, iron, sulfur and sodium.

Why do we need them? Calcium = bone formation Iron = transportation of oxygen in blood Phosphorus = nerve transmission Sulfur = helps in blood clotting Sodium = muscle contraction More info

Trace Elements Essential in minute quantities for proper biological functioning (common additive in food and water) Example: Iodine is a trace element that prevents goiter. Many foods are fortified with trace elements and vitamins (which consist of two or more elements)

Goitre Lacking iodine so the body cannot make thyroxin –a hormone made by the thyroid gland and used for metabolism… individuals tend to be overweight with this condition. Found in iodized salt and seafood

Water, the great polar molecule!

Covalent Bonds Nonpolar covalent - atoms share electrons equally Polar covalent - atoms share electrons unequally One part of the molecule is slightly positive, and one part is slightly negative

In other words, if there is an atom that DOES NOT SHARE the electrons fairly, that atom acts like it has a negative charge!

2.2.U1 Water molecules are polar and hydrogen bonds form between them. Water molecules and their bonds Water (H2O) is made up of two hydrogen atoms covalently bound to an oxygen atom Share electrons unevenly Leads to polarization Slight Charges attract opposites. Water molecules can associate via weak hydrogen bonds Hydrogen bonds are transitory in nature – they constantly form, break and re-form

Hydrogen bonds are weak bonds between two polar molecules The attraction between slightly positive regions and slightly negative regions creates hydrogen bonds Hydrogen bonding occurs in many biologically important compounds -Water -DNA -Proteins

Hydrogen bonds are an important part of the properties of water. LE 2-10 Hydrogen bonds are an important part of the properties of water. Hydrogen bond

Water is Cohesive it sticks to itself Note surface tension!

Water is Adhesive it sticks to other things                                                    Transpiration: water needs to stick to the tubes of the plant and to itself to release water into the air.

Water has a high specific heat: it takes a lot of energy to change the temperature of water Energy is first used to break the hydrogen bonds, then to increase the temperature.

Hydrogen bonds in water moderate temperature When water is heated, the heat energy is absorbed, disrupting hydrogen bonds -The water stores a large amount of heat while warming only a few degrees When water is cooled, heat energy is released as hydrogen bonds are formed -The temperature of the water is lowered slowly

Water also Water moderates temperature by evaporative cooling -The surface cools as the hottest molecules leave

Water expands when it freezes Ice floats… but cold water is dense and sinks, this causes a lake to ‘turnover’

Ice is less dense than liquid water Hydrogen bonds in ice create a stable, three-dimensional structure Ice is less dense than water, because it has fewer molecules in the same volume Hydrogen bonds are stable Hydrogen bonds constantly break and re-form

Water is the solvent of life A solution is a homogeneous mixture of a liquid solvent and one or more dissolved solutes Because water is a polar molecule, it readily forms solutions with many other polar and ionic compounds A solution in which water is the solvent is an aqueous solution

LE 2-14 Ion in solution Salt crystal

Water as a solvent Water separates Na+Cl- (salt) into sodium (Na+ ) and chlorine (Cl- ) Necessary biological functions i.e. - Chlorine = carries electrical charge allowing nerve cells to work - Sodium = provides for normal muscle contraction