Chapter 02: Chemical Basis of Life

Comprehensive practice questions and answers covering the chemical basis of life, including atomic structure, bonding, pH, and organic/inorganic molecules based on Chapter 02 lecture notes.

Why is chemistry studied in Anatomy and Physiology?

Because all anatomical structures are chemicals, and all physiological processes are based on chemical reactions.

Define Matter.

Anything that takes up space and has mass; it is composed of elements and exists as solids, liquids, and gases.

Define Mass

Mass is the amount of matter present

Define Weight

the heaviness due to the gravitational pull on mass

Define Chemistry

Studies composition, properties, interaction of matter

What is the focus of Biochemistry?

biological chemistry, which studies physiological processes and disease.

What are Elements?

The simplest types of matter with certain chemical properties; there are $92$ naturally occurring elements.

Compounds

particle formed when two or more atoms of different elements chemically combine

• all compounds are molecules but not all molecules are compounds

Atoms

Smallest particles of an element that have properties of that element

Define Bulk elements and provide examples.

Elements required by the body in large amounts, such as Carbon ($C$), Oxygen ($O$), Hydrogen ($H$), Nitrogen ($N$), Sulfur ($S$), and Phosphorus ($P$).

What is a Trace element?

An element required by the body in small amounts, such as Iron ($Fe$) and Iodine ($I$).

Ultratrace elements

Required by the body in very minute amounts, like Arsenic (As)

Table of bulk and trace elements in the body

What is the most abundant element in the human body by weight?

Oxygen ($O$), making up approximately $65.0\%$ of the human body.

Describe the three subatomic particles of an atom.

Protons (positive charge), Neutrons (neutral; no charge), and Electrons (negative charge).

Protons

Large particles; carry a single positive charge

Neutrons

Large particles; carry no electrical charge

Electrons

Small particles; carry a single negative charge

Atoms consist of

a central nucleus (protons + neutrons) and electrons in constant motion around the nucleus

Why are atoms considered electrically neutral?

The number of protons in an atom equals the number of electrons.

Atomic Structure

Define Atomic Number.

The number of protons in the nucleus of an atom of a specific element.

• each element has a unique atomic number

Define Mass Number.

The number of protons plus the number of neutrons in one atom.

What are Isotopes?

Atoms with the same atomic numbers but different mass numbers due to containing different numbers of neutrons.

Radioactive isotopes

unstable atomic forms that release energy or atomic fragments (atomic radiation) until gaining stability

What are some medical uses of Radioactive isotopes?

used to detect:

• coronary blood vessel disorders,

• evaluate kidney function,

• measure hormone concentrations in body fluids,

• assess changes in bone density

What is the medical use for Radioactive iodine-131?

It is used to destroy cancerous thyroid gland tissue because the thyroid is the only part of the body that actively transports and metabolizes iodine.

What is Ionizing Radiation?

Radiation (alpha, beta, and gamma) that has enough energy to remove electrons from atoms, forming ions (charged atoms).

• free electrons can damage nearby atoms

What are sources of Ionizing radiation?

include X-rays, naturally occurring radioactive elements in the crust of the earth, and nuclear weapons

Computerized Tomography (CT scanning)

Imaging uses X-rays to create $3$-dimensional images of soft tissues

• used to see internal anatomy

Positron Emission Tomography (PET) imaging

imaging uses radioactive isotopes to detect biochemical activity and brain disorders

Define Molecule.

A particle formed when two or more atoms chemically combine.

Molecular formulas

Depict the elements present and the number of each atom present in the molecule

H₂

a molecule of hydrogen (not a compound)

C₆H₁₂O₆

a molecule of glucose (a compound)

H₂O

a molecule of water (a compound)

Chemical bond

Bonds form when atoms combine with other atoms.

• They result from interactions between the electrons of the atoms.

Electron shells

Electrons of an atom occupy regions of space, which encircle the nucleus, called

What are the electron capacity rules for the first three shells of an atom with an atomic number of $18$ or less?

The first shell can hold up to $2$ electrons, the second shell up to $8$, and the third shell up to $8$.

• Lower energy shells/inner orbits are filled first

How do the electrons in the outermost shell affect an atom's reactivity?

The number of electrons in the outermost (valence) shell determines if an atom will react with other atoms to form chemical bonds

What is an Ion?

An electrically charged atom that has gained or lost electrons to become stable.

• have a full outermost shell

cation

a positively charged ion (loses electrons)

anion

a negatively charged ion (gains electrons)

How is an Ionic Bond formed?

It is a strong chemical bond formed when ions of opposite charges attract each other.

• cations attract anions

ionic bond

How is a Covalent Bond formed?

A strong chemical bond formed between atoms that share electrons.

Covalent bonds

Structural formulas

•show how atoms bond and are arranged in various molecules

• more detailed than a molecular formula because it shows form

One line between atoms means

that 1 pair of electrons are being shared (forming single covalent bonds), while two lines indicate that 2 pairs are being shared (forming double bonds).

Nonpolar covalent bonds

Covalent bonds in which electrons are shared equally

• Found between atoms with same electronegativity

What is Electronegativity?

The pull for electrons exerted by the protons in the nucleus of an atom.

Polar covalent bonds

share electrons unequally, creating molecules with slightly negative and positive parts

• atoms with a larger number of protons have higher electronegativity, and pull shared electrons closer to their nucleus

Polar molecules

What is a Hydrogen Bond?

A relatively weak attraction between the slightly positive $(H)$ end of one polar molecule and the slightly negative ($N$ or $O$) end of a nearby polar molecule.

Chemical reactions

reactions occur when chemical bonds form or break between atoms, ions, or molecules

Reactants

Reactants are the starting materials of a chemical reaction

Products

are the substances formed at the end of a chemical reaction

List the four types of chemical reactions identified in the notes.

Synthesis Reaction, Decomposition Reaction, Exchange Reaction, and Reversible Reaction.

synthesis reaction

chemical bonds are formed to make a more complex structure

Decomposition Reaction

chemical bonds are broken to form a simpler chemical structure

Exchange Reaction

chemical bonds are broken and new bonds are formed

Reversible Reaction

the products can change back to the reactants

What happens when an ionically bonded substance is put into water?

The charged ions separate and are attracted to the polar water molecules, causing the substance to dissociate.

• The cations and anions become surrounded by water molecules.

What is an Electrolyte?

A substance that releases ions in water and can conduct an electric current.

Define Acid and Base according to their dissociation in water.

are electrolytes that release hydrogen ions ($H^+$)

Base

are electrolytes that release ions that combine with hydrogen ions

salts

Electrolytes formed by the reaction between an acid and a base

How is pH determined?

pH is a shorthand for $H^+$ concentration, based on the number of decimal places in the concentration in $g/L$.

• If the H⁺ concentration = 0.01g/L, the pH is 2

• If the H⁺  concentration = 0.000000001 g/L, the pH =9

pH scale

Indicates the relative concentration of hydrogen ions (H+) and hydroxide ions (OH-) in a solution

What pH values represent Acidic, Neutral, and Basic solutions?

pH scale runs from 0 through 14

• Acidic: < 7; a higher concentration of H+ than OH-

• Neutral: $7$; indicates equal concentrations of H+ and hydroxide ions (OH-)

• Basic (alkaline): > 7; indicates a higher concentration of OH- than H+

Hydrogen Ion Concentration and pH

pH scale

What is the normal range of blood pH?

$7.35$ through $7.45$.

What terms describe blood pH falling below $7.35$ or rising above $7.45$?

Acidemia ($7.0$–$7.3$)

What terms describe blood pH rising above $7.45$?

Alkalemia ($7.5$ –$7.8$)

Alkalosis

makes a person feel dizzy and agitated

What is the function of a Buffer?

Buffers are chemicals that resist pH changes by binding or releasing $H^+$.

Organic molecules.

contain $C$ and $H$

• include carbohydrates, proteins, lipids, and nucleic acids

Inorganic molecules

generally do not contain both $C$ and $H$ and usually dissolve in water to form ions

• include water, oxygen, carbon dioxide, and inorganic salts

What are the primary functions of Water in the human body?

It is the most abundant compound,

• acts as a medium for metabolic reactions, transports chemicals and heat, and serves as a solvent.

What is the role of Oxygen ($O_2$) in cells?

It is used by organelles to release energy from nutrients to drive metabolic activities.

Carbon dioxide (CO₂)

• Waste product released during metabolic reactions

• Must be removed from the body through exhaling

Inorganic salts

• Sources of necessary ions

• Play important roles in metabolism

• Help control H₂O concentration, pH, blood clotting, nerve and muscle processes

• Electrolyte balance exists when gains equal losses

• Na⁺, Cl^-, K⁺, Ca²⁺, etc.

Carbohydrates

• Main source of cellular energy

• Supply materials to build cell structures

• Water-soluble

• Contain C, H, and O

• Ratio of H to O close to 2:1 (C₆H₁₂O₆ = glucose)

List the classifications of carbohydrates by size.

Monosaccharides (single sugars), Disaccharides (double sugars), and Polysaccharides (complex carbohydrates)

Monosaccharides

glucose, fructose

Disaccharides

sucrose, lactose

Polysaccharides

starch, glycogen, cellulose

Lipids

• Insoluble in water, but soluble in organic solvents

• Include triglycerides (fats), phospholipids, steroids

• Important component of cell membranes, and have several functions in cells

most abundant lipid

Triglycerides (fats)

• •Used for cellular energy

  •Contain more energy per gram than carbohydrates

  •Contain C, H, and O, but less O than carbohydrates

What is the composition of a Triglyceride?

One molecule of glycerol and three fatty acids.

• Fatty acids are chains of hydrogen and carbon with two oxygens at one end

Compare Saturated and Unsaturated fatty acids.

have only single carbon-carbon bonds and are usually solid at room temp (animal origin)

Unsaturated fatty acids

have one or more double bonds and are usually liquid at room temp (plant origin).

fatty acids

What are Phospholipids?

Lipids consisting of $1$ glycerol, $2$ fatty acids, and a phosphate group

• they are the main structural component of cell membranes.

Steroids

• 4 connected rings of carbon

• Widely distributed in the body, various functions

• Component of cell membranes

• Used to synthesize adrenal and sex hormones

What is the main steroid in the body?

Cholesterol

Proteins

Used as structural materials, energy source, hormones, receptors, enzymes, antibodies, and many more functions

• Consist of building blocks called amino acids

Define the structure of an Amino Acid.

Contains an amino ($-NH_2$) group, a carboxyl ($COOH$) group, and a unique R (side chain) group.

• •bound to each other by peptide bonds