Atoms and Subatomic Particles

Definition of Atom

An atom is the smallest unit of matter that retains the properties of an element. Atoms are the building blocks of all substances in the universe.

• Subatomic particles: Atoms are composed of three main subatomic particles:

  • Proton: Positively charged particle found in the nucleus.

  • Neutron: Neutral particle found in the nucleus.

  • Electron: Negatively charged particle found in orbitals around the nucleus.

• Atomic number: The atomic number tells you the number of protons in an atom, which determines the element's identity.

• Nucleus composition: The nucleus of an atom contains protons and neutrons.

Chemical Symbols of Elements

Chemical symbols are one- or two-letter abbreviations for elements.

• Sodium: Na

• Potassium: K

• Chlorine: Cl

• Calcium: Ca

• Carbon: C

• Hydrogen: H

• Oxygen: O

• Nitrogen: N

Isotopes

Isotopes are atoms of the same element that have different numbers of neutrons, resulting in different mass numbers.

• Example: Carbon-12 and Carbon-14 are isotopes of carbon.

Chemical Bonding

Types of Chemical Bonds

• Ionic bond: Formed when electrons are transferred from one atom to another, resulting in oppositely charged ions that attract each other.

• Covalent bond: Formed when two atoms share one or more pairs of electrons.

• Hydrogen bond: A weak attraction between a hydrogen atom (already covalently bonded to an electronegative atom) and another electronegative atom.

Formation of Ions

• Ion: An atom or molecule with a net electric charge due to the loss or gain of electrons.

• Cation: A positively charged ion (e.g., Na+).

• Anion: A negatively charged ion (e.g., Cl-).

Ionic and Covalent Bonds

• Ionic bond formation: Example: Sodium (Na) transfers an electron to chlorine (Cl), forming Na+ and Cl-, which combine to form NaCl.

• Covalent bond formation: Example: Two hydrogen atoms share electrons with one oxygen atom to form H2O.

Water Molecule Bonds

• Polar covalent bonds hold the atoms together within a water molecule.

• Hydrogen bonds attract water molecules to each other, giving water its unique properties.

Chemical Notation and Reactions

Chemical Notation

• Molecular formula for glucose: Molecular formula for glucose:

Types of Chemical Reactions

• Synthesis reaction: Two or more simple substances combine to form a more complex product.

• Decomposition reaction: A complex molecule breaks down into simpler substances.

• Exchange reaction: Parts of molecules are swapped to form new products.

Glucose Breakdown in Cells

• Glucose () can be split into two three-carbon molecules (pyruvate) in a process called glycolysis, which is a decomposition reaction.

Enzymes and Chemical Compounds

Enzymes

• Enzyme: A biological catalyst that speeds up chemical reactions in cells.

• Enzymes are needed to regulate metabolic pathways and maintain homeostasis.

Inorganic and Organic Compounds

• Inorganic compound: A compound that does not contain both carbon and hydrogen (e.g., water, salts).

• Organic compound: A compound that contains both carbon and hydrogen (e.g., glucose, proteins).

Important Inorganic Compounds in the Human Body

• Water

• Salts (e.g., sodium chloride)

• Acids and bases

Properties of Water

Key Properties

• High heat capacity: Water can absorb and release large amounts of heat with little temperature change.

• Polarity/solvent properties: Water dissolves many substances, making it an excellent solvent.

• Chemical reactivity: Water participates in many chemical reactions, such as hydrolysis.

Solutions and Electrolytes

Definitions

• Solution: A homogeneous mixture of two or more substances.

• Solvent: The substance that dissolves the solute (usually water in biological systems).

• Solute: The substance dissolved in the solvent.

• Ion: Charged particle formed when an atom gains or loses electrons.

• Cation: Positively charged ion.

• Anion: Negatively charged ion.

• Electrolyte: A substance that conducts electricity when dissolved in water due to the presence of ions.

Acids and Bases

• pH: A measure of hydrogen ion concentration; scale ranges from 0 (acidic) to 14 (basic).

• Acid: Substance that releases hydrogen ions () in solution.

• Base: Substance that accepts hydrogen ions or releases hydroxide ions ().

Biological Molecules

Carbohydrates

• Common examples: Glucose, fructose, sucrose, starch, glycogen.

• General functions: Provide energy, store energy, structural support.

• Monosaccharide: Simple sugar (e.g., glucose).

• Disaccharide: Two monosaccharides joined together (e.g., sucrose).

• Polysaccharide: Many monosaccharides linked together (e.g., starch, glycogen).

• Storage form of glucose: Glycogen in animals, starch in plants.

Lipids

• Common examples: Triglycerides, phospholipids, steroids.

• General functions: Energy storage, insulation, cell membrane structure, hormone production.

• Most common lipid in the human body: Triglycerides.

• Best known steroid: Cholesterol.

• Phospholipid: A lipid containing a phosphate group; major component of cell membranes.

• Phospholipid structure: Hydrophilic (water-attracting) head and hydrophobic (water-repelling) tails.

Proteins

• Monomers: Amino acids.

• Functions: Enzymes, structural support, transport, defense, movement.

Enzymes

• Proteins that act as biological catalysts.

• Speed up chemical reactions without being consumed.

Nucleic Acids

• Functions: Store and transmit genetic information.

• Types: DNA and RNA.

• Groups in nucleic acids: Phosphate group, sugar, nitrogenous base.

• Structural differences between DNA and RNA:

  • DNA: Double-stranded, contains deoxyribose sugar, bases are A, T, C, G.

  • RNA: Single-stranded, contains ribose sugar, bases are A, U, C, G.

ATP and Energy

ATP Structure and Function

• ATP (Adenosine Triphosphate): The primary energy carrier in cells.

• Function: Provides energy for cellular processes.

• Reversible reaction: (where is inorganic phosphate)

*Additional info: Some definitions and examples have been expanded for clarity and completeness. Table content inferred from context and standard academic sources.*