Biology of Water Lecture Notes

Practice flashcards covering the biological roles and chemical properties of water including polarity, hydrogen bonding, and thermal properties.

What role does water play as a versatile solvent in biological systems?

It acts as the fluid medium in which dissolved molecules (solutes) can move, interact, and form the chemical bonds necessary for metabolism.

Which two biochemical processes specifically require or produce water molecules?

The synthesis of proteins (condensation) and the digestion of food (hydrolysis).

How is water produced during the process of energy production?

Water is produced at the end of oxidative phosphorylation when oxygen accepts electrons and protons.

What two key factors are responsible for water's unique chemical properties?

The polarity of its molecules and their ability to form hydrogen bonds with each other and other molecules.

What is the chemical definition of polarity as it relates to water?

The state of having two opposite or contradictory tendencies, poles, or charges.

Why does oxygen create a partial negative charge in a water molecule?

Oxygen is highly electronegative, acting like an "electron magnet" that pulls shared electrons closer to itself than the hydrogen atoms can.

Why do the partial charges in a water molecule not cancel each other out?

Because of the molecule's bent geometry, which makes it a highly polar molecule with distinct positive and negative ends.

How do hydrogen bonds form between water molecules?

The positive end of one water molecule (a hydrogen atom) associates with the negative end of an adjacent water molecule (the oxygen atom) through electrostatic attraction.

According to the chemical rule, which atoms must hydrogen be covalently attached to for a hydrogen bond to occur?

Hydrogen must be attached to highly electronegative atoms such as Fluorine, Nitrogen, or Oxygen.

What is the power dynamic of hydrogen bonds in terms of their quantity?

Hydrogen bonds are relatively weak interactions when alone, but highly powerful in large numbers.

What are the characteristics and examples of hydrophilic substances?

They are charged or polar substances that readily interact with and dissolve in water, such as sugars, salts, amino acids, and vinegar.

What characterizes hydrophobic substances like oils and fats?

Nonpolar molecules that do not interact well with water, separating rather than dissolving.

What is the difference between cohesion and adhesion?

Cohesion is water molecules sticking to each other due to hydrogen bonding, while adhesion is water molecules sticking to other polar or charged surfaces.

Which biological processes allow plants to draw water from roots to leaves against gravity?

Capillary action, enabled by cohesion and adhesion, together with transpiration pull.

Why does water have a high specific heat?

Energy is absorbed to disrupt and continually rearrange hydrogen bonds before the molecular kinetic energy can substantially increase.

What is the biological importance of water's high heat of vaporization?

It allows for evaporative cooling (sweating), which removes immense heat from the body, and helps maintain stable internal temperatures.

What happens to water molecules as they cool below $4^\circ C$?

The molecules slow down, allowing hydrogen bonds to lock them into a rigid, open crystalline lattice structure.

At what temperature does water form a complete crystalline lattice?

$0^\circ C$.

Why does ice float on liquid water?

The crystalline lattice structure keeps the molecules further apart than they are in liquid form, making ice less dense than liquid water.

What is the biological impact of ice forming at the top of lakes and oceans?

It forms a protective insulating layer that prevents bodies of water from freezing solid from the bottom up, preserving aquatic life underneath.