A.1.1 Water

1. The first cells originated in water.

2. Water is the "universal solvent" allowing it to dissolve and transport molecules around a body.

3. Water is a metabolite in condensation and hydrolysis reactions.

4. Water is a temperature buffer in bodies and ecosystems.

5. Water maintains biological structures (such as phospholipid bilayer, proteins and DNA).

Protons and neutrons make up the nucleus of the atom, while electrons orbit it in a "cloud".

The electrons in an atom are attracted to the protons in the nucleus by an electromagnetic force in which the positive charge of the proton attracts the negative charge of the electron.

An ionic bond is an attraction between a positively charged ion and an negatively charged ion.

In a covalent bond, two atoms share one or more pair of electrons.

In a polar covalent bond, the nucleus of one atom has more pull on the shared electrons than the other atom. As a result, it has a bigger electron cloud surrounding it. Because electrons have a negative charge and there are MORE ELECTRONS around this nucleus, there is a slight negative charge (ઠ-) on this nucleus. Because there are LESS ELECTRONS around the second atom's nucleus, there is a slight positive charge (ઠ+) on this nucleus

two polar covalent bonds within a water molecule; one between the oxygen atom and each hydrogen atom.

The nucleus of the oxygen atom of a water molecules has more pull on the shared electrons than the hydrogen atom. As a result, it has a bigger electron cloud surrounding it. Because electrons have a negative charge and there are MORE ELECTRONS around the oxygen nucleus, there is a slight negative charge (ઠ-) on this nucleus. Because there are LESS ELECTRONS around the hydrogen atom's nucleus, there is a slight positive charge (ઠ+) on this nucleus

A water molecule consists of 2 hydrogen and 1 oxygen atom, hence…H2O. Within a water molecule, electrons are shared through polar covalent bonding between the atoms.(see slide 1)

The partially positive hydrogen atoms of one water molecule are attracted to the partially negative oxygen atom of a different water molecule, forming a hydrogen bond.

Water’s ability to make hydrogen bonds with itself and other charged molecules grants it a number of emergent properties such as cohesion, adhesion, solvency and a high specific heat. Collectively these property make water the primary medium of life.

Cohesion is the property of water in which it makes hydrogen bonds with itself, causing water molecules to stick together,

1. Transpiration (evaporation) occurs through stomata of a leaf. As transpiration occurs, it creates negative pressure

2. The tension created by transpiration “pulls” water in the plant xylem, drawing the water upward

3. Cohesion pulls up water molecules in a chain as the top-most water is pulled up and out of the stomata.

The molecules on the surface are more attracted other molecules of the liquid than to molecules in the surrounding air. The net effect is an inward force that causes water to behave as if its surface were covered with a stretched elastic membrane.

Surface tension allows organisms like water striders to “walk on water” and provides a stable environment for other organisms that live on or near the surface of water. To break through the surface of the water, enough force must be applied to break many hydrogen bonds simultaneously.

The attraction of water to other polar or charged molecules is called adhesion.

unequal sharing of electrons in a covalent bond between two atoms.

An ion is an atom with different (unequal) numbers of electrons and protons.

A cation has a positive charge because it has more protons than electrons (Na+)

An anion has a negative charge because it has more electrons than protons (Cl-)

The slight negative charge (δ-) of water oxygen atom is attracted to the [slight] positive charge of molecules that are polar or charged.

The slight positive charge (δ+) of water hydrogen atom is attracted to the [slight] negative charge of molecules that are polar or charged.

Capillary action is the movement of water in through a narrow space, often in opposition to external forces like gravity. Adhesion of water to the walls of a vessel will cause an upward force on the liquid

Capillary action helps bring water from the roots all the way up to the branches and leaves. Adhesion of water to the xylem walls will cause an upward force on the water.

Capillary action in soil the primary force that enables the soil to retain water. In the same way that water moves upwards through a tube against the force of gravity; water moves upwards through soil pores, or the spaces between soil particles.

Solvent: the liquid in which a solute dissolves

Solute: the substance that dissolves in a solvent

interaction of a solvent with the dissolved solute

Water is electrostatically attracted to ions.

The slight positive charge (δ+) of of water hydrogen atom is attracted to the negative charge of an anion .

The slight negative charge (δ-) of of water oxygen atom is attracted to the positive charge of a cation.

Polar molecules can form hydrogen bonds with water.

The slight positive charge (δ+) of of water hydrogen atom is attracted to the negatively charged region of the solute.

The slight negative charge (δ-) of of water oxygen atom is attracted to the positively charged region of the solute.

Hydrophobic means water fearing. Because they are not polar or charged, hydrophobic molecules will not dissolve in water. They are insoluble.

Hydrophilic means water loving. Because they are polar or charged, hydrophilic molecules will dissolve in water. They are soluble.

Because of they have hydrophillic amino acids, enzymes can dissolve in cytoplasm where they are used to catalyze chemical reactions in the cell.

Because of their hydrophobic tail, phospholipids will form bilayers in water, with the tails not exposed to water.

Cytosol is the liquid part of the cytoplasm, a structure common to all cells. It is composed of about 80 percent water and also contains dissolved salts, fatty acids, sugars, amino acids, and proteins such as enzymes. These substances must be dissolved in water in order to carry out the metabolic processes required to keep the cell alive.

Water is used to transport molecules through the body of vascular plants.

Dissolved mineral ions are transported in the xylem from roots to leaves

Dissolved sugars produced in photosynthesis are transported in the phloem from source to sink

Water is used to transport molecules through the body within the blood of animals. Blood plasma transports
Salt ions
Amino acids
Proteins
Glucose
Waste products of metabolism
A small amount of dissolved gasses

A physical property is a measurable behavior or characteristic of matter that exists without the matter reacting or interacting with other things.

Buoyancy
Viscosity
Thermal conductivity
Specific heat capacity

Cause:
an upward force applied to an object that is immersed in a fluid.


Effect:
If the buoyant force of the fluid is greater than the object's weight, the object will float.

Air < Water < Blood

Molecules in air have little friction as they flow over each other, so air is not viscous.

Molecules in water can form hydrogen bonds with each other, increasing the friction and viscosity.

Cells and dissolved solutes in blood cause even more friction as the blood flows, increasing viscosity.

Thermal conductivity is a measure of a material's ability to move heat across a temperature gradient.

Less Conductive
Heat slowly moves through the material.
Better at insulation and preventing heat loss.

More Conductive
Heat rapidly moves through the material.
Better for absorbing and transferring heat.

Marine mammals are exposed to both air and water. The animal will lose more body heat to the environment when in water than in air because water rapidly absorbs and removes heat from the body. As a result, these animals have large layers of blubber which insulate their body heat sources (muscles) from the environmental. Fat is less conductive of thermal energy than water, so the animal is able to retain more body heat than it would be able to without the blubber.

Specific heat capacity is the quantity of heat needed to raise the temperature of a chemical per unit mass.

Water’s high heat capacity is caused by its numerous hydrogen bonds. Each individual “bond” is weak, but there are so many of them that collectively a lot of energy must be added to break them all.

As a result of its high specific heat capacity, water heats up or cools down very slowly. This provides for a stable internal environment and habitat of living things.

Because living body’s contain a lot of water, body temperature is slow to fluctuate when environmental temperatures change. Water’s high specific heat capacity helps body temperature rise and fall slowly when external temperatures becomes very hot or cold.

Water
greater buoyant force
greater viscosity
greater thermal conduction
greater specific heat capacity

Air
lower buoyant force
lower viscosity
lower thermal conduction
lower specific heat capacity

Buoyancy in water allows the bird to stay afloat without expending a lot of energy, however when flying through air the bird must expend energy to stay aloft. Air is not viscous, so the loon can easily move through it when flying. The loon doesn’t lose as much body heat to the air because air has low thermal conductivity. However, because the air has a low specific heat, its temperature changes as rapidly.

Buoyancy in water allows the seal to stay afloat without expending a lot of energy. However, the water is viscous, so the seal has adaptations for streamlining as it swims through it. Water has a greater thermal conductivity than air, so the seal needs to insulate itself with blubber to maintain body temperatures. However, because the water has a high specific heat, the temperature of the water does not change as rapidly as the air around it, providing habitat stability for the seal.