DIHYDROGEN MONOXIDE (DHMO)

What to do about the world’s most deadly compound…

Unit 2 – Bio-molecules and Biochemistry

The Chemistry of Life

It all starts with Water

• Life depends on water!

• Why do you think water is so special?

• Water’s formula is H2O, two hydrogens covalently bonded to one oxygen.

Water’s Shape

• Water is a polar molecule– Oxygen is slightly

negative– The Hydrogens are slightly

positive

• Since positive and negative charges attract, this creates a weak bond called a hydrogen bond.

COHESION• Due to the hydrogen

bonds…– Water molecules stick to

other water molecules. This is called Cohesion. (Co – think couple)

• Surface Tension – enables organisms to walk on the water

• Capillary action – works with adhesion to draw water up the roots and stems of plants

ADHESION• Due to the hydrogen

bonds…– Water molecules stick

to other surfaces. This is called Adhesion (think adhesive, like glue)

• Works with cohesion to provide capillary action in plants

High Specific Heat• Water resists changing

temperature– 3/4ths of Earth is covered

in water which absorbs or releases heat

– Creates very stable marine and coastal environments

– Prevents extreme temperature fluctuations like those on other planets

Evaporative Cooling

• As water evaporates, it removes heat from a surface– This is how sweating

keeps you cool!

Density of Water• Water doesn’t follow the normal

rule of density. MOST solids sink because they are very dense, but solid water (ice) floats because it is less dense. – Becomes more and more dense until

4*C– Expands after 4*C and Freezes at the

lowest density at 0*C– Floating ice prevents lakes and

streams from freezing solid.

Density of Water (Gas)

Density of Water (Liquid)

Density of Water (ICE)

Water – the Universal Solvent

• Water will dissolve just about anything which makes it important for chemistry in living things– Hydrophilic – water loving, substances that

dissolve easily in water (i.e. salt)– Hydrophobic – water fearing, substances

that will not dissolve in water, these are non-polar compounds (i.e. oil)

Penny Lab Requirements

• Work with the partner I assign you. • Stay at your lab station and do not interact with the

other groups. • Stay focused on the lab. It should not take you

longer than ten minutes. • Do all plain water trials first, then do soapy. DO

NOT MIX. • Clean up your station when you are finished, and

return to your seat.

Friday, 8/23

• In your bell work section, answer the following question. (If you write in complete sentences, then you do not have to write the question)

• Which is more dangerous – Acid, Base, or Fire? Why?

pH Scale – Acids and Bases

• The pH scale is used to determine if a solution is an acid or a base. – Acids are found below 7. They get stronger

as you approach zero. – Neutral substances (like pure water) can be

found exactly at 7. – Bases are found above 7. They get stronger

as you approach 14.

pH levels and Biology• Strong acids and strong

bases cause damage to cells – Living things must

maintain a consistent pH level (typically from 6-8) by using buffers, which are substances that can bring a pH level back to normal.

– Where do you think most of the buffers in your body are found and why?

• Acid Rain is a major pollutant concern in biology– Rain or snow with a

pH lower than 5.6 can damage forests and lakes or streams.

– Caused by smoke mixing with rain water and lowering the pH level.

Effects of Acid Rain

7 8 9 10 11 12 133 4 5 62 141 9 10 11 123 4 5 621

Weak Base

Neutral Strong

Base

Weak Acid

Strong Acid

The pH Scale

Macromolecules

• Living things are made of Carbon, Hydrogen, Oxygen, Nitrogen, Phosporus, and Sulfur (CHONPS) with a few other elements in small amounts.

• These create carboyhdrates, lipids, nucleic acids, and proteins, which are taken in from/with food and used to build new cells/tissues

Carbohydrates

• Monomer – carbon rings; 1-2 rings = sugar; chain of rings = starch

• Look for –rings OR formula of CHO with 1:2:1 ratio (ex- C6H12O6)

• Uses – energy (food)• Test – Benedict’s

reagent turns orange with sugar; Iodine turns black with starch

• Draw Them

Examples of Carbohydrates

Lipids (fats)• Monomer – fatty

acids (CH chains) Look for – Capital “E” shape OR a C-H chain OR a CHO formula with very few O (ex. C9H18O2)

• Uses – store energy (fat), waterproof (oil), insulation (blubber)

• Test –Sudan Red stains lipids dark red

• Draw Them

Lipid Examples

Nucleic Acids (DNA or RNA)

• Monomer – Nucleotides (phosphate, sugar, and nitrogen base)

• Look for – P for (phosphorus) OR a spiral helix shape

• Uses – genetic info, instructions for proteins

• Test – No test• Draw Them

Nucleic Acid Examples

Proteins

• Monomer – amino acids (22 types)

• Look for – the “amino head”

• Uses – Almost everything from digesting food (enzymes) to coloring your eyes. (structural) (You are one big walking protein)

• Test – Biuret’s reagent turns dark purple in the presence of protein

• Draw Them

Protein Example