Bio 221-Water

Where is water found in cells and living organisms?

Everywhere. They are inside of cells and surround cells

Non-polar molecule

Electrons are equally shared between molecules (hydrogen and carbon)

Where is the partial positive charge on water? partial negative?

+=hydrogen -=oxygen

Explain how the polarity of water affects how water molecules interact with other water molecules.

The partial charges on the atoms of water molecules cause hydrogen bonding between the oxygen and hydrogen.

Explain why water can act as a solvent for many biologically important molecules.

Many biological molecules are also polar meaning they can dissolve in water. The polarness of water can also break ionic bonds

What types of molecules can dissolve in water? 

polar molecules or ionic bonds

What types of molecules cannot dissolve in water? 

non-polar molecules. polar and non polar do not mix (i.e. oil and water)

Why is the fact that water is a solvent important for living organisms?

used in different cellular processes, can help carry waste and nutrients, regulate temperature, etc.

Explain how water promotes the formation of membranes

In amphipathic molecules, the polar regions are hydrophilic and will react with the water molecules while the non-polar regions are hydrophobic and will move away from the water molecules. This often creates a micelle

How is a polar molecule different from a non-polar molecule?

a polar molecule has some sort of dipole and partial charge while a nonpolar molecule is neutral

Can a non-polar molecule be dissolved into a polar solvent? 

Yes but only under VERY specific conditions, usually polar and non polar do not mix because neither one will dissolve

What is an amphipathic molecule?

a molecule that has both polar and non-polar regions

How does water participate in reactions within cells?

water is used in many cellular reactions to either form covalent bonds or break covalent bonds(hydrolysis and condensation reactions)

What happens during a condensation (dehydration) reaction

an OH group and an H group of two molecules interact, forming a H20 molecule that gets lost in the reaction. Then a covalent bond is formed where the h20 was lost

What happens during hydrolysis?

Water is added (often times to a protein) and covalent bonds are broken (i.e. turning proteins back into amino acids

Explain how water provides support.

water can create hydrostatic pressure and turgor pressure (plants) to help provide support and structural integrity

What is turgor pressure?

When the hydrostatic pressure from osmosis presses the cell membrane against the cell wall, turgor pressure is created (only in plants)

How does turgor pressure affect plants?

turgor pressure helps maintain a plant cell’s structural integrity and rigidness which contributes to the plant’s support

Why is water stable as a liquid?

The hydrogen bonding between h20 molecules is very strong so they are not easily separated. Water also has a high specific heat capacity and heat of vaporization so it requires ala lotot of energy to break the hydrogen bonds

Specific heat

the heat required to raise the temperature of 1g of a substance 1 degree Celcius

Heat capacity

the heat required to raise the temperature of an entire object/substance

Heat of vaporization

the heat required to vaporize 1 M of substance at boiling point

Which property of water is most responsible for the dissipation of body heat while sweating?

Evaporation (taking heat from the body and evaporating the sweat)

Sublimation

going from a solid directly to a vapor

deposition

going from a vapor directly to a solid

What is the difference between cohesion and adhesion?

Cohesion is how water molecules interact with THEMSELVES and adhesion is how water interacts with other molecules or surfaces

Biological examples of cohesion…

surface tension of water (bugs can stand on water)

Biological examples of adhesion…

water is used as a lubricant to aid eating (saliva)

The _____________ force of water molecules aids in the movement of fluid through vessels in plants

cohesive

Transpiration

evaporation of water in plants that creates a change in pressure

the formula for pH when given hydrogen ion concentration?

pH=-log[H^+]

Which pH values are acidic?

less than 7

which pH values are basic?

more than 7

What’s another word for a basic pH value?

alkaline

What is a neutral pH value?

7

Spontaneous Ionization of water

the tendency for water to dissociate into OH and H groups