Comprehensive Guide to Chemistry of Life: Atoms, Molecules, Water, Organic Compounds, and Enzymes

What is a chemical element?

The simplest form of matter to have unique chemical properties.

How is each element identified?

By its atomic number.

What is the range of naturally occurring elements?

There are 91 naturally occurring elements.

Which six elements account for 98.5% of the body's weight?

Oxygen, carbon, hydrogen, nitrogen, calcium, and phosphorus.

What elements make up 0.8% of the body's weight?

Sulfur, potassium, sodium, chlorine, magnesium, and iron.

What are trace elements?

The remaining 12 elements that make up 0.7% of the body's weight.

What role do minerals play in the human body?

They contribute to body structures, enable enzyme function, and are vital to nerve and muscle function.

What percentage of the body's weight do minerals constitute?

4% of the body's weight.

What are the main components of bones and teeth?

Crystals of minerals.

Who was the first to use the term 'atom'?

The Greek philosopher Democritus.

What did John Dalton propose in 1803?

An atomic theory of matter.

What is the composition of an atom's nucleus?

Protons and neutrons.

What is the charge of protons and neutrons?

Protons have a positive charge, neutrons have no charge.

What is the atomic mass of protons and neutrons?

1 amu (atomic mass unit) each.

What surrounds the nucleus of an atom?

Electrons in concentric clouds.

What is the charge of electrons?

Electrons have a negative electrical charge.

What is the maximum number of electrons in the first three electron shells?

2 in the first, 8 in the second, and 18 in the third.

What are valence electrons?

Electrons in the outermost shell that determine chemical bonding properties.

What are isotopes?

Varieties of elements that differ in the number of neutrons.

What are radioisotopes?

Unstable isotopes that decay into stable isotopes, giving off radiation.

What is the atomic weight of an element?

The sum of the mixture of isotopes of that element occurring in nature.

What is ionizing radiation?

High-energy radiation that can destroy molecules and tissues.

What can high doses of ionizing radiation cause?

It can be fatal; in low doses, it can be mutagenic or carcinogenic.

What are the three types of radiation caused by decay?

Alpha particles, beta particles, and gamma rays.

What is an alpha particle composed of?

Two protons and two neutrons.

How deeply can alpha particles penetrate?

They do not penetrate deeply but are dangerous if they enter the body.

What is a beta particle?

A free electron that does not penetrate deeply but can be dangerous if emitted inside the body.

What are gamma rays characterized by?

High energy and deep penetration, dangerous even if emitted outside the body.

What is the physical half-life of an isotope?

The time required for 50% of its atoms to decay.

What is the biological half-life of an isotope?

The time required for half of it to disappear from the body.

How long is the physical half-life of Cesium-137?

30 years.

What is the biological half-life of Cesium-137?

17 days.

How is the intensity of ionizing radiation measured?

In sieverts (Sv).

What dosage of radiation is usually fatal?

5 Sv or more.

What is the average annual background radiation exposure for Americans?

About 2.4 millisieverts (mSv) per year.

What is the acceptable occupational exposure limit for radiation per year?

50 mSv.

What are ions?

Charged particles with unequal numbers of protons and electrons.

What occurs during ionization?

An element gives up or gains electrons in its outer shell.

What is an anion?

A negatively charged ion.

What is a cation?

A positively charged ion.

What happens to sodium and chlorine in sodium chloride (NaCl)?

Sodium gives up an electron, and chlorine gains an electron to fill its outer shell.

What are electrolytes?

Salts that ionize in water, forming solutions that can conduct electricity.

Why are electrolytes important in patient care?

They are crucial for chemical reactivity, osmotic effects, and electrical effects.

What are free radicals?

Chemical particles with an odd number of electrons.

How are free radicals produced?

By metabolic reactions, radiation, and chemicals such as nitrites.

What role do antioxidants play?

They neutralize free radicals, preventing damage to tissues.

What distinguishes a compound from a molecule?

A compound is a molecule composed of two or more different elements.

What are isomers?

Molecules with the same molecular formula but different arrangements of atoms.

What are the types of chemical bonds?

Ionic bonds, covalent bonds, hydrogen bonds, and van der Waals forces.

What is an ionic bond?

The attraction of a cation to an anion, as seen in NaCl.

Can ionic bonds involve more than two ions?

Yes, ionic bonds can be formed by more than two ions, such as in CaCl2.

How do ionic bonds behave in water?

Ionic bonds are weak and easily dissociate in the presence of more attractive molecules like water.

What is a covalent bond?

A covalent bond forms by the sharing of electrons between two atoms.

What is the difference between a single and a double covalent bond?

A single covalent bond involves the sharing of one pair of electrons, while a double covalent bond involves the sharing of two pairs.

What characterizes a nonpolar covalent bond?

Shared electrons spend approximately equal time around each nucleus.

What is a polar covalent bond?

Shared electrons spend more time around one nucleus, resulting in a small charge difference represented as δ- and δ+.

What is a hydrogen bond?

Weak attraction between a slightly positive hydrogen atom in one molecule and a slightly negative oxygen or nitrogen atom in another.

How do water molecules interact through hydrogen bonds?

Water molecules form hydrogen bonds with each other.

In what contexts can hydrogen bonds form?

Between different regions of a single large molecule, such as proteins and DNA.

Why are hydrogen bonds important in physiology?

they provide stable structures for DNA and proteins, facilitate rapid proton transport for enzyme reactions and pH balance, and give water essential properties like high heat capacity

What are Van der Waals forces?

Weak, brief attractions between neutral atoms caused by random fluctuations in electron orbits.

What are some examples of Van der Waals forces in action?

When plastic wrap clings or when spiders walk across ceilings.

What is a mixture?

Substances that are physically blended but not chemically combined.

What percentage of body weight does water constitute?

50% to 75% of our body weight.

What are the two important aspects of water's structure?

Water's atoms are joined by polar covalent bonds, and the molecule is V-shaped with a 105° bond angle.

What properties does water's polarity give it?

Properties such as solvency, cohesion, adhesion, chemical reactivity, and thermal stability.

What is solvency in the context of water?

The ability to dissolve other chemicals; water is often called the universal solvent.

What is the difference between hydrophilic and hydrophobic substances?

Hydrophilic substances dissolve in water, while hydrophobic substances do not.

What must a molecule be to be soluble in water?

Polarized or charged.

What happens when sodium chloride is dissolved in water?

Water molecules form a hydration sphere around each ion, helping to keep them separated and dissolved.

What is adhesion and cohesion in relation to water?

Adhesion is the tendency of one substance to cling to another, while cohesion is the tendency of a substance to cling to itself.

What is the significance of water's high heat capacity?

Allows it to absorb energy without changing state, providing thermal stability and effective cooling.

How can mixtures in water be classified?

Solutions, colloids, and suspensions.

What characterizes a solution?

Solute particles mixed with a solvent, usually water, where solute particles are under 1 nm in size and do not scatter light.

What is a colloid?

A mixture of larger particles in a solvent, such as albumin in blood plasma.

What is the size range of colloid particles?

1 to 100 nm in size.

Why are colloids usually cloudy?

The particles scatter light due to their size.

Can colloid particles pass through selectively permeable membranes?

No, they are too large to pass through most selectively permeable membranes.

Do colloid particles separate from the solvent?

No, colloid particles remain permanently mixed and do not separate from the solvent.

What is a suspension?

A mixture with large particles in a solvent, such as red blood cells in blood plasma.

What is the size of particles in a suspension?

They exceed 100 nm in size.

How does a suspension appear?

Cloudy or opaque.

Can particles in a suspension pass through selectively permeable membranes?

No, the particles are too large to pass through selectively permeable membranes.

What happens to particles in a suspension over time?

Particles do not remain permanently mixed and separate upon standing.

What is an emulsion?

A suspension of one liquid in another, such as oil and vinegar salad dressing.

What types of mixtures can blood be classified as?

A solution, a colloid, and a suspension.

What is concentration in terms of solutions?

A measure of the amount of solute in a given volume of solution.

How is weight per volume concentration expressed?

Grams per liter of solution (g/L).

What unit is often used for biological concentration measurements?

Milligrams per deciliter (mg/dL) is often used.

What are the two types of percentages used in concentration?

Weight per volume (w/v) and volume per volume (v/v) must be specified.

What is molarity?

The number of moles of a solute per liter of solution.

What does one mole of a substance contain?

Avogadro's number (6.023 × 10^23) of molecules.

How much glucose is in a one-molar (1.0 M) solution?

180 grams of glucose per liter.

How are electrolyte concentrations measured?

Equivalents (Eq).

What defines one equivalent of an electrolyte?

One Eq is the amount that would electrically neutralize 1 mole of hydrogen ions (H+) or hydroxide ions (OH-).

What is the relationship between molarity and equivalents based on ion valence?

1 mM Na+ is equal to 1 mEq/L, while 1 mM Ca2+ is equal to 2 mEq/L.

What is an acid?

Any proton donor, a molecule that releases H+ in water.

What is a base?

Proton acceptor.

How is acidity expressed?

In terms of pH, derived from the molarity of H+.

What does a change of one whole number on the pH scale represent?

It represents a 10-fold change in H+ concentration.