Module 2 - Chemistry, Matter, And Life

What is the definition of an element?

A unique, fundamental substance that makes up all matter; it cannot be decomposed into a simpler substance by ordinary chemical means.

How many elements occur naturally in nature, and how many are found in living organisms?

• Naturally occurring: 92 elements.

• Found in living organisms: 26 elements

Which 4 elements make up approximately 96% of human body weight?

Oxygen (O), Carbon (C), Hydrogen (H), and Nitrogen (N).

What percentage of body weight do secondary elements (like Calcium, Sodium, Potassium, etc.) make up?

About 4% of total body weight.

What percentage of body weight is made up of trace elements (like Zinc, Selenium, Copper)?

Extremely small amounts totaling about 0.1% of body weight.

What is the primary function of Oxygen (O) in the body?

It is a major component of water (H2O) and is needed by cells to metabolize nutrients for energy.

What is the primary function of Carbon (C) in the body?

It forms the chemical basis of all organic compounds and is a key component of carbon dioxide (CO2), a metabolic waste product.

What is the primary function of Hydrogen (H) in the body?

It is a component of water, participates in energy metabolism, and determines the pH/acidity of body fluids.

What is the primary function of Nitrogen (N) in the body?

It is present in all proteins, nucleic acids (DNA and RNA), and ATP (the cellular energy molecule).

What are the key functions of Calcium (Ca)?

Builds bones and teeth; essential for muscle contraction, nerve impulse transmission, and blood clotting.

What are the key functions of Phosphorus (P)?

Component of ATP, nucleic acids, and cell membranes; works with calcium to build bones and teeth.

What are the key functions of Potassium (K)?

Major role in nerve impulse conduction and muscle contraction.

What are the key functions of Sodium (Na)?

Plays a central role in maintaining water balance, nerve impulse transmission, and muscle contraction.

What is the key function of Sulfur (S)?

It is an essential component of many proteins.

What is the key function of Iron (Fe)?

Essential component of hemoglobin, the compound in red blood cells that carries oxygen to tissues.

What is an atom?

The smallest subunit or complete unit of a chemical element that cannot be broken down or changed into another form by ordinary chemical or physical means.

What are the three main subatomic particles that make up an atom?

• Protons: Positively charged particles in the central nucleus.

• Neutrons: Uncharged (neutral) particles in the central nucleus.

• Electrons: Negatively charged particles orbiting the nucleus.

What holds electrons in orbit around the atomic nucleus?

The attraction between the positively charged protons in the nucleus and the negatively charged orbiting electrons.

What is the atomic number of an element?

The number of protons present in the nucleus of its atoms (which also equals the number of orbiting electrons in a neutral atom).

What is atomic weight (mass), and how is it calculated?

The sum of the protons and neutrons in the nucleus.

Why are electrons excluded when determining an element's atomic weight

Electrons are extremely tiny making their mass negligible.

What are electron energy levels?

Specific regions or distances from the nucleus where electrons orbit.

How many electrons can fit into the first, second, and third energy levels?

• 1st level (closest): Up to 2 electrons.

• 2nd level: Up to 8 electrons.

• 3rd level: Up to 8 electrons (stable capacity).

What determines an atom's chemical reactivity?

The number of electrons in its outermost energy level.

What makes an atom stable or nonreactive (inert)?

Having a completely filled or stable number of electrons (usually 8) in its outermost energy level (noble gases like helium, neon, argon).

What is an ion and how does it form?

An atom or group of atoms that has acquired an electrical charge by gaining or losing one or more valence electrons.

What are the terms for positively charged and negatively charged ions?

• Cation: A positively charged ion (lost electrons).

• Anion: A negatively charged ion (gained electrons).

What is an ionic bond

A chemical bond formed by the electrostatic attraction between oppositely charged ions created when electrons are transferred from one atom to another.

How do sodium and chlorine form an ionic bond in table salt?

Sodium transfers its 1 outer electron to chlorine. Sodium becomes a positively charged cation and chlorine becomes a negatively charged anion their opposite charges attract.

What are electrolytes

Compounds that release ions when dissolved in water, allowing the solution to conduct electricity.

Why are key ions like sodium and potassium essential in body fluids?

Their positive charges are essential for generating and transmitting electrical signals along nerves and muscle cells.

What is a covalent bond?

A chemical bond formed when two or more atoms share one, two, or three pairs of valence electrons to stabilize their outer shells.

What is a nonpolar covalent bond?

A covalent bond where electrons are shared equally between atoms, distributing electrical charges evenly with no distinct positive or negative poles (O2)

What is a polar covalent bond?

A covalent bond where electrons are shared unequally, pulling closer to one atom and creating a slightly negative region and a slightly positive region (H2O)

What is a molecule, and what type of bond forms it?

Two or more atoms held together covalently. Only covalent bonds form true molecules (chemists do not consider ionically bonded substances to be molecules because they are held together only by electrical attraction).

What is a compound?

Any substance composed of two or more different elements in a fixed ratio. This includes both covalently and ionically bonded substances

How do the properties of a compound compare to the properties of the individual elements that make it up?

The properties are completely different. For example, liquid water is formed from hydrogen and oxygen gases. Glucose is a sweet solid made from gases (hydrogen, oxygen) and a solid (carbon).

Are atoms created or destroyed during everyday biological chemical reactions?

No. Atoms are neither created nor destroyed; they are only rearranged by breaking and forming chemical bonds.

In a chemical equation (A + B → C), what do the terms on the left and right sides represent?

• Left side (A + B): Reactants (starting substances).

• Right side (C): Products (resulting substances).

What does a single arrow (—>) indicate in a chemical equation?

It indicates an irreversible reaction (the products do not easily break back down into the reactants).

What does a double arrow (⇄) in a chemical equation indicate?

It indicates a reversible reaction where products can break back down into reactants (D + E ⇄ F)

What is chemical equilibrium?

A state in a reversible reaction where the forward reaction occurs at the exact same rate/frequency as the reverse reaction, keeping reactant and product concentrations constant.

What happens to reactant and product concentrations when a reversible reaction is not at equilibrium?

Whichever direction occurs more frequently will change the concentrations ( if forward reaction rate exceeds reverse rate, reactants decrease and products increase).

What is the definition of a mixture?

A blend of two or more substances that are combined physically rather than chemically, meaning the components retain their individual identities and properties.

What is the difference between a homogeneous and a heterogeneous mixture?

• Homogeneous: A mixture that is uniform in composition throughout.

• Heterogeneous: A mixture where the individual components remain distinct and are not evenly distributed at a microscopic level.

What is a solution, and what are its two components?

A homogeneous mixture formed when one substance dissolves in another.

• Solvent: The dissolving substance (usually present in greater amount, like water).

• Solute: The substance that gets dissolved (like salt or sugar).

What is an aqueous solution?

A solution in which water serves as the solvent.

What is a suspension?

A heterogeneous mixture in which particles are dispersed in a liquid but will settle out over time unless constantly mixed or agitated (for example, red blood cells in plasma or milk of magnesia).

What is a colloid?

A heterogeneous mixture containing tiny, non-dissolved particles that remain evenly distributed because of their small size and opposing electrical charges (for example, cytosol or gelatin).

What is the most abundant compound in the human body?

Water.

What is dehydration

A severe deficiency of water in body tissues that threatens health and disrupts normal physiological processes.

What essential physiological processes are made possible by water in the body?

Absorption, exchange, secretion, excretion, and the transport of nutrients and waste to and from cells.

Why is water known as the "universal solvent"?

Because it can dissolve many different substances in large amounts, allowing gases, salts, and nutrients to be transported throughout the body.

What is the difference between hydrophilic and hydrophobic substances?

• Hydrophilic ("water-loving"): Substances that mix with or dissolve easily in water (for example, salts and sugars).

• Hydrophobic ("water-fearing"): Substances that do not dissolve in water (for example, fats and oils).

How does water help regulate body temperature?

It distributes heat throughout body tissues and cools the body surface through the evaporation of sweat

What role does water play in cellular metabolism?

It participates directly in chemical reactions, serving as a required reactant in digestion and cellular metabolic processes.

What is an acid

A chemical compound that donates hydrogen ions (H+) in solution, increasing the H+ concentration.

What is a base or alkali

A chemical compound that accepts hydrogen ions or releases hydroxide ions (OH-) in solution.

What is produced when an acid reacts with a base?

A salt and water (the hydrogen of the acid is replaced by the positive ion of the base).

What does pH measure?

The relative concentration of hydrogen ions (H+) and hydroxide ions (OH-) in a solution on a scale from 0 to 14.

What is the relationship between hydrogen ion (H+) and hydroxide ion (OH-) concentrations?

They are inversely related as H+ concentration increases, OH- concentration decreases, and vice versa.

What values on the pH scale indicate acidic, neutral, and alkaline (basic) solutions?

• Acidic: pH less than 7.0 (higher H+ concentration).

• Neutral: pH exactly 7.0 (equal concentrations of H+ and OH-, like pure water).

• Alkaline / Basic: pH greater than 7.0 (higher OH- concentration)

How much of a change in hydrogen ion concentration does each unit on the pH scale represent?

Each pH unit represents a 10-fold (10x) change.

What is alkalosis?

A physiological state where blood pH rises above 7.45.

What is a buffer?

A chemical substance or system that prevents sharp or sudden changes in the pH of a solution by absorbing or releasing hydrogen ions (H+).

why are chemical buffers essential in the human body?

They maintain homeostatic stability in body fluid pH within very narrow limits, protecting cells and tissues from dangerous shifts toward acidosis or alkalosis.

How does a buffer react if excess acid (hydrogen ions) is added to a solution?

The buffer binds to the excess hydrogen ions (H+), neutralizing them and preventing the solution's pH from dropping drastically.

How does a buffer react if excess base (hydroxide ions) is added to a solution?

The buffer releases hydrogen ions (H+) to combine with the excess hydroxide ions (OH-), preventing the solution's pH from rising sharply.

What is an isotope

A form of an element that has the same number of protons (atomic number) as other forms of the element, but a different number of neutrons in its nucleus (resulting in a different atomic weight).

What does it mean for an isotope to be radioactive?

It is an unstable isotope that spontaneously breaks down (decays), emitting subatomic particles and/or high-energy electromagnetic waves (such as gamma rays).

How are radioisotopes formed?

They can occur naturally (such as heavy elements like radium and uranium) or be produced artificially by smashing nuclei together in particle accelerators.

Why is radiation effective in treating cancer?

Cancer cells in a growing tumor are immature and rapidly dividing, making them much more sensitive to destruction by high-energy radiation than mature, healthy body cells.

What is a radioactive tracer?

A radioactive element administered internally so its radiation can be detected to identify structural or functional abnormalities in organs or tissues.

What defines an organic compound?

Complex chemical molecules that characterize living things, built around the element carbon.

Why is carbon the backbone of organic molecules?

Carbon atoms can form stable covalent bonds with a variety of elements and with other carbon atoms, creating long, complex chains and ring structures.

What are monomers?

Simple building block molecules (mono = "one") that bond together in long chains to form larger organic polymers.

What are the three main types of organic nutrients found in the body and diet?

Carbohydrates, lipids, and proteins (all composed primarily of carbon, hydrogen, and oxygen).

What are the three main classes of carbohydrates based on size?

• Monosaccharides: Simple single-sugar units (for example, glucose).

• Disaccharides: Two simple sugars linked together.

• Polysaccharides: Many simple sugars linked together in long chains (for example, glycogen or starch).

What is glucose, and why is it important?

A simple monosaccharide sugar that serves as the main source of immediate energy for body cells.

What is glycogen?

A complex polysaccharide stored in body tissues (such as liver and muscle) as a reserve storage form of glucose.

What is a triglyceride (simple fat)?

A lipid compound composed of one glycerol molecule combined with three fatty acid chains.

What is a phospholipid?

A lipid containing phosphorus, essential in forming the structural foundation of cellular membranes.

What is a steroid, and what is a prime example in the body?

A category of lipids containing distinct rings of carbon atoms. Cholesterol is a key example that contributes to cell membrane structure and hormone synthesis.

What element is present in proteins that is NOT found in carbohydrates or simple fats?

Nitrogen (in addition to carbon, hydrogen, and oxygen).

What are the building blocks (monomers) of proteins?

Amino acids. Each contains a central carbon attached to a hydrogen atom, an acid group (COOH), an amino group (NH2), and a variable side chain (R region).

What type of chemical bond links amino acids together to form a protein?

A peptide bond (forms between the acid group of one amino acid and the amino group of another).

What is the difference between fibrous and globular proteins?

• Fibrous proteins: Long, ropelike structural proteins (for example, collagen in bone and cartilage).

• Globular proteins: Complex, 3D-folded functional proteins (for example, myoglobin, hemoglobin, enzymes, hormones, and antibodies).

What is an enzyme

A protein catalyst that speeds up the rate of specific chemical reactions in the body without being permanently altered or consumed in the process.

What is a substrate?

The specific reactant molecule or substance that an enzyme binds to and acts upon.

How does the "lock-and-key" mechanism describe enzyme specificity?

An enzyme's 3D shape must match the precise shape of its substrate to bind together, just as a key must fit a specific lock.

What suffix typically indicates that a molecule is an enzyme?

The suffix -ase (for example, lipase, protease, oxidase).

What is denaturation, and what causes it?

The alteration of a protein's (or enzyme's) 3D shape so that it can no longer function. It is caused by harsh environmental conditions such as extreme temperature or pH, which break weak hydrogen bonds holding the protein shape together.

What are the three main structural components of a nucleotide

• A nitrogen-containing base.

• A sugar (usually ribose or deoxyribose).

• One or more phosphate groups (containing phosphorus).

What is adenosine triphosphate (ATP)

The primary energy-storing and transferring nucleotide molecule used by cells to drive cellular work.

How is energy stored and released in an ATP molecule?

Energy is stored in the high-energy chemical bonds connecting its phosphate groups. When these phosphate bonds are broken (hydrolyzed), energy is released for cellular use.

What is metabolism

The sum of all physical and chemical processes and life-sustaining chemical reactions occurring within the body.

What is catabolism

Metabolic breakdown reactions in which complex substances are broken down into simpler building blocks, releasing stored chemical energy in the form of ATP.

What is anabolism

Metabolic synthesis reactions in which simple component molecules are built up into complex substances needed for growth, tissue repair, and cellular function. These reactions require energy fueled by ATP.

What is kinetic energy?

The energy of movement or motion possessed by active matter (ranging from vibrating molecules to locomotion of an organism).

What are two specific forms of kinetic energy mentioned in physiology?

• Radiant energy: Energy traveling in waves through space (such as sunlight, heat, sound, and X-rays).

• Electric energy: Energy reflecting the movement of electrons, such as electrical currents along nerve cells (neurons).