Properties of WaterChapter 2.2

Most of the material in chapter 2.2 is not necessary for this course.

There are a few things about water that you should know.

The water molecule (page40)

Water is a compound made of 2 hydrogen atoms and one oxygen atom.

Formula – H2O

Water is found everywhere on the planet Earth, yet is thought to be rare in the rest of the universe.

Water is necessary for all life as we know it.

The theories behind the origin of life on Earth require water.

No water = No life

Humans are currently searching for life on other planets (and their moons).

We assume that if a planet has water, it could have life.

On the other hand, if the planet does not have water, it probably doesn’t have life.

Why is water so important for life?

1. Water has polarity – which means it has poles of positive and negative charge.

2. This makes a water molecule similar to a magnet – remember – opposites attract.

3. The oxygen side of a water molecule has a slight negative charge.

4. The hydrogen side of a water molecule has slight positive charge.

•

Water molecules will cling together similar to magnets.

When water molecules cling together, it is

called hydrogen bonding.

That’s nice, but why is that important to life?

Because of the polarity on water molecules, water is highly capable of dissolving other substances.

Most substances will dissolve in water because of the positive and negative charges on water molecules.

Water can dissolve most substances because water is a polar molecule.

For this reason, amino acids, triglycerides,

glucose, nucleic acids, salts, and other compounds can be dissolved in water.

For example, Blood is mostly water, and is the main transport fluid in complex organisms.

If water could not dissolve lots of substances, then blood would not work well.

Other liquids can not dissolve substances as well as water.

Why is water important to living things?

Because water can dissolve many substances (due to its polarity)

Cl-

Water

Cl-

Na+

Water

Na+

Section 2-2

Figure 2-9 NaCI Solution

Section 2-2

Figure 2-9 NaCI Solution

Cl-

Water

Cl-

Na+

Water

Na+

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Chemical reactions and enzymes2.4

Chemical reactions keep living things alive.

A chemical reaction happens when 2 or more elements or compounds come together to form different compounds.

For example, when monomers join together to form polymers – this is a chemical reaction.

Compounds and elements don’t just come together naturally.

There are specific molecules that will put them together.

This is similar to a factory – the parts of a car do not just fall in place together.

Machines (and humans) put the parts together in such a way that makes the car work properly.

Enzymes are proteins that have 3 main functions

1. Put substances together in such a way so that they are useful.

2. Break substances apart in such a way so that they are not harmful

3. Speed up chemical reactions so they can be useful at high speeds.

1. Put substances together in such a way so that they are useful.

2. Break substances apart in such a way so that they are not harmful

3. Speed up chemical reactions so they can be

useful at high speeds.

If a specific chemical reaction needs to take place quickly – many enzymes will be necessary.

Enzymes are found everywhere in the body, in cells, outside of cells, in the bloodstream etc.

Living things could not exist without enzymes.