AP bio Unit 1 Chemistry of life

How do organisms use water to survive

Organisms rely on water because of its unique properties—like polarity, hydrogen bonding, high specific heat, heat of vaporization, cohesion, adhesion, and solvent abilities—which enables essential biological functions such as maintaining temperature, transporting substances, and supporting chemical reactions in the cytoplasm.

1. We see Polarity & Hydrogen bonds allow water molecules to stick together (cohesion) and to other substances (adhesion) which facilitating transportation (e.g., water moving up plant xylem)

2. High specific heat ensures stable water temperature, helping maintain internal homeostasis.

3. High heat of vaporization enables evaporative cooling (e.g., sweating, panting)

4. Excellent solvent for polar and ionic molecules, enabling transport and biochemical interactions.

Surface Tension

It is the result of cohesion between water molecules due to hydrogen bonding, which creates a “film-like” surface as it has an ability against rupturing when put under tension or stress.

This allows small organism (like insects) to move or rest on water.

Cohesion

Is the attraction between water molecules causes by hydrogen bonding which allows water molecules to stick together.

1. This allows for Surface tensions - which lets insects and small organisms move on water

2. This helps pull water upward in the Xylem during transpiration. Water moves upward in plants through xylem. As water evaporates from leaves, it pull the next water molecules up like a chain. This is because water molecules stick together by hydrogen bonds, when one water molecule is pulled upward, it drags the others with it—allowing continuous after flow from roots to leaves.

Adhesion

Is the attraction between water molecules and other polar surfaces, which helps water stick to things like plant cells walls.

______ helps water molecules stick to the walls of xylem, preventing the water column from sliding back down.

Moreover the _______ + the cohesion together lets water move upward in narrow tubes, which supports transpiration in plants because the _____ makes water molecules stick to the polar walls of the xylem, so gravity doesn't pull the water column straight back down. This “grip” on the walls, combined with ________ allows water to climb upward.

Capillary Actions

Is the ability of water to move upward in the thin tubes because of cohesion (water sticking to water) and adhesion (water sticking to other surfaces)

In plants that water moves upward through the narrow xylem tubes due to capillary action in where the molecules stick together and the water sticks to the xylem walls, which allows water to climb against gravity during transpiration.

In animals they have tiny capillaries, where blood is pulled along partly by capillary action in where the water in blood stays connected and the water in the plasma sticks to capillary walls. This helps blood reach vary narrow vessels where pressure is low.

Solvent

It is a substance, like water, that dissolves other molecules so they can be transported or react in cells. (water is called the universal _____)

This works because water’s polarity causes it to surround and separate ins or polar molecules, allowing them to dissolve.

For example, in blood transport water dissolves salts, sugars, and gases so they can move throughout the body. Or water also dissolves reactants so chemical reactions can occur inside cells.

Specific heat capacity

This is the amount of heat energy needed to to raise the temperature of substance (like water) by 1 degrees Celsius.

Water molecules are held together by hydrogen bonds, when heat is added, much of the energy goes into breaking these hydrogen bonds rather than speeding up the molecules so it takes a longer time for water to heat up.

However when water cools, hydrogen bonds reforms, which releases heat slows as they slow down. (This is why water has a high _____ _____ ______)

This matters causes it causes water to resist rapid temperature changes, keeping cells and environments stable. This further protects organism from overheating or freezing too quickly.

Thermoregulator

Is an organism’s ability to maintain a stable internal temperature despite external temperature changes.

This works as water’ high specific heat helps absorb or release heat slowly, preventing rapid temperature changes in cells and tissues.

For example in humans sweating cools the body via evaporative cooling, and in plants transpiration helps leaves stay at safe temperatures.

Evaporative cooling

Is the process where water absorbs heat as it evaporates, lowering the temperature of a surface or organism.

This works as hydrogen bonds in water require energy to break, so when water evaporates from skin, leaves or other surfaces, it removes the heat that was used to break it.

Polarity

Is when a molecules has a slightly postie and slightly negative ends due to uneven sharing of electrons, creating partial negative and positive charges at each end of the molecule and subsequentially an unsymmetrical shape.

This works in water because oxygen is more electronegative than hydrogen, so it “hogs” the shared electrons, making oxygen slightly more negative and hydrogen slightly positive. This creates polar molecules that can form hydrogen bonds with each other and other polar molecules.

Some examples of this would be water being able to dissolve salts, sugars, and other polar molecules. Or Cohesion and adhesion in where it helps water move in plants and maintain surface tension.

Electronegativity

Is the ability of an atom to attract shared electrons in a chemical bonds this is caused from some atoms having more protons in a nucleus which creates a stronger positive pull on the negativity charged electrons.

Hydrogen bonding

The attractive forces between a hydrogen atom covalently (share electrons) bonded to a very electronegative atom such as a N, O, or F atom, and another very electronegative atom.

Subcomponents, sequence, and properties of molecules influence.

The subcomponents of biological molecules and their sequence determine the properties of that molecules.

For example water is made of two hydrogen atoms and one oxygen atom (subcomponents) and the sequence and arrangement (H-O-H angle and polarity) create a polar molecule with slightly positive hydrogen and a slightly negative oxygen.

This causes water to have properties, like cohesion and adhesion, high specific heat, solvent ability, and surface tensions and evaporative cooling.

What do water systems depend on

Water systems depend on properties of water that results from its polarity and hydrogen bonding.

What does the hydrogen bonds in water result in

The hydrogen bonds between water molecules results In cohesion, adhesion, and surface tension.

The structure of molecules determines their what

The structure of molecules determines their function.