Anatomy and Physiology 12: Properties of Water, pH, Buffers, and Biological Molecules

Vocabulary flashcards covering the physical properties of water, the logarithmic pH scale, buffer mechanisms, covalent bonding in biological molecules, and dehydration synthesis versus hydrolysis.

Density of Water

An unusual physical property where liquid water is denser than solid ice, causing ice to form on top of bodies of water and insulate the liquid water below to prevent it from freezing solid.

Cohesion

The property of water molecules sticking to each other, playing a key role in transporting water against gravity in plants and contributing to surface tension.

Adhesion

The property of water molecules clinging to a different substance, such as adhering to the walls of blood vessels.

Surface Tension

A measure of the force necessary to stretch or break the surface of a liquid, which is higher in water because hydrogen bonds among surface water molecules resist stretching or breaking.

Hydrolytic Reactions

Chemical reactions that use water ($\text{hydro}$) to break ($\text{lytic}$) bonds within compounds.

pH

A measure referring to the potential hydrogen ion concentration ($[H^+]$) in a solution, indicating how acidic or basic it is on a scale from $0$ to $14$.

Acid

A substance that increases the hydrogen ion concentration ($[H^+]$) in a solution, such as hydrochloric acid ($HCl$) which dissociates into $H^+$ and $Cl^-$ ions.

Base

A substance that increases the hydroxide ion concentration ($[OH^-]$) in a solution, such as sodium hydroxide ($NaOH$) which dissociates into $Na^+$ and $OH^-$ ions.

Logarithmic pH Scale

A mathematical representation where each unit change on the $pH$ scale represents a factor of $10$ in hydrogen ion concentration, defined by $pH = -\log[H^+]$ or $[H^+] = 10^{-pH}$.

Neutral Solution

A solution with a $pH$ of $7$ where the concentration of hydrogen ions equals the concentration of hydroxide ions ($[H^+] = [OH^-]$).

Denature

The process where proteins, such as enzymes, break down and lose shape due to drastic changes in $pH$, preventing them from functioning properly.

Buffers

Biological chemicals or combinations of chemicals that resist changes to the $pH$ of a solution by combining with excess $OH^-$ or $H^+$ to maintain homeostasis.

Strong Acid

An acid, such as $HCl$, that dissociates to a much greater extent than weak acids, releasing many free $H^+$ ions into solution.

Neutralizing Effect

The chemical interaction where $OH^-$ from a base combines with $H^+$ in the environment to form water and salt.

Covalent Bonds

Relatively strong bonds formed when two non-metal atoms share a pair of electrons to complete their outermost electron shell.

Lewis Structures

Chemical diagrams that depict covalent bonds as lines drawn between atomic symbols rather than pairs of dots.

Polymers

Large molecules formed by joining smaller unit molecules (monomers), such as proteins, carbohydrates, fats, and nucleic acids.

Dehydration Synthesis

A chemical reaction requiring energy that joins unit molecules into polymers by removing a water molecule ($H^+$ from one molecule and $OH^-$ from the other).

Hydrolysis

A chemical reaction requiring energy that breaks down polymers into smaller unit pieces by adding a molecule of water ($\text{Hydro}$ = water, $\text{lysis}$ = to break apart).