Chapter 2 Tran

Definition: Anything that has mass and occupies space.
Mass: Quantity of matter in an object, equated to weight on Earth, but they are not always equivalent in different gravitational fields.

Three states:
- Solid: Definite shape and volume, particles tightly packed in a fixed arrangement.
- Liquid: Definite volume, changeable shape, particles are close but can flow past each other.
- Gas: Changeable shape and volume, particles are far apart and move freely.

Water exists in all three states at temperatures compatible with life: solid (ice), liquid (water), gas (water vapor).
Importance: Unique properties contribute to its role as a solvent, temperature regulator, and participant in biochemical reactions.

Elements: Substances that cannot be broken down and have unique physical and chemical properties.
Key Elements in the Human Body:
- Principal Elements:
  - Oxygen (O): Essential for cellular respiration.
  - Carbon (C): Backbone of organic molecules, essential for life.
  - Hydrogen (H): Component of water; participates in energy transfer.
  - Nitrogen (N): Vital for amino acids and nucleic acids.
- Additional Elements:
  - Calcium (Ca): Important for bone structure, muscle contraction, and nerve signaling.
  - Phosphorus (P): Key component of ATP, DNA, and cell membranes.
  - Potassium (K), Sodium (Na), Chlorine (Cl): Participate in fluid balance and nerve conduction.
- Trace Elements: Needed in small amounts; including
  - Zinc (Zn): Important for immune function and enzyme activity.
  - Chromium (Cr): Involved in glucose metabolism.
  - Manganese (Mn): Necessary for bone formation and metabolism.

Importance: Familiarity with major element symbols (e.g., O, C, Ca, K) is essential for understanding chemical reactions and biological processes.

Basic Components: Atoms that interact to form molecules, the smallest stable units of matter.

Nucleus: Contains protons (positive charge) and neutrons (no charge), responsible for most of the atom's mass.
Electrons: Negatively charged particles orbiting the nucleus.

Atomic Number: Number of protons in the nucleus, determining the element’s identity.
Mass Number: Sum of protons and neutrons, influencing the stability of the atom.

Atoms with the same number of protons but different numbers of neutrons, often useful in medicine (e.g., radioactive isotopes used in imaging).

Ionic Bonds: Formed by the transfer of electrons; result in charged ions (cations and anions). Example: Sodium (Na) loses an electron to become Na+, while Chlorine (Cl) gains an electron to become Cl-.
Covalent Bonds: Formed by the sharing of electrons between atoms; can be single, double, or triple bonds.
Nonpolar vs Polar Covalent Bonds:
- Nonpolar: Equal sharing of electrons, e.g., molecular hydrogen (H2).
- Polar: Unequal sharing, e.g., water (H2O) has a partial negative charge near the oxygen atom.
Hydrogen Bonds: Weak attractions between polar molecules, particularly between water molecules, contributing to unique properties like high surface tension and specific heat.

Definition: Formation or breaking of chemical bonds resulting in products from reactants.
Types of Reactions:
- Synthesis Reactions: Smaller molecules combine to form larger ones (anabolic).
- Decomposition Reactions: Larger molecules broken down into smaller ones (catabolic).
- Exchange Reactions: Bonds are both made and broken, rearranging atoms.
- Enzymatic Reactions: Most reactions require enzymes to lower activation energy, influencing reaction rates and allowing for physiological functions.

Kinetic Energy: Energy in motion (e.g., muscle contractions, movement of molecules).
Potential Energy: Stored energy available to do work (e.g., chemical energy in food and gasoline).
Energy Conversion: Not 100% efficient; byproducts include heat, according to the laws of thermodynamics.

Universal Solvent: Ability to dissolve polar substances, facilitating biochemical reactions and nutrient transport.
Polarity: Water molecules are polar, allowing for hydrogen bonding and effects such as surface tension, which affects aquatic life and the movement of liquids through small spaces (capillary action).
pH Regulation: Vital to maintaining appropriate body fluid pH, which is essential for enzymatic activity and metabolic processes.

Acids: Substances that release hydrogen ions (proton donors), with a pH < 7, playing a role in digestion and metabolism.
Bases: Substances that release hydroxide ions (proton acceptors), with a pH > 7, important in many biochemical pathways.
Buffers: Compounds that maintain pH levels by absorbing or releasing hydrogen ions, stabilizing pH in biological systems.

Definition: Compounds containing carbon, vital for biological processes, forming the basis of life.
Types:
- Carbohydrates: Energy sources; can be classified as monosaccharides (simple sugars), disaccharides (two sugars), and polysaccharides (complex carbohydrates like starch and glycogen).
- Lipids: Diverse hydrophobic compounds (e.g., fats, oils, and steroids), important for energy storage, insulation, and cellular structure.
- Proteins: Made of amino acids, providing structural support, transport, and catalyzing biochemical reactions; proteins can be denatured, affecting their function.
- Nucleic Acids: DNA and RNA; critical for genetic information and protein synthesis.
- Nucleotides: Building blocks of nucleic acids, consisting of a sugar, phosphate, and nitrogenous base, playing roles in energy transfer (e.g., ATP).

DNA: Double-stranded, contains genetic information, organized into genes.
RNA: Single-stranded, plays roles in protein synthesis (types include messenger RNA (mRNA), transfer RNA (tRNA), and ribosomal RNA (rRNA)).
ATP: Energy currency of cells, high-energy molecule essential for life processes, facilitating energy transfer.