GENERAL ZOOLOGY

• Vertebrates are animals that have a backbone or spinal column.
• Animals are made up of molecules, which are collections of atoms bound to one another
• Life processes within an animal are based on the chemical properties of atoms, ions, and molecules
• Carbon is the key element of organic molecules because it has unique physical and chemical characteristics
• Carbohydrates and lipids are principal sources of energy for most animals
• Proteins, nucleotides, and nucleic acids provide the basis for structure, function, information storage, energy transfer, and genetic regulation in animals
• Matter is composed of elements, which are chemical substances that ordinary chemical reactions cannot break down into simpler units
• Elements are composed of units of matter called atoms.
• An atom is the smallest part of an element that can enter into a chemical reaction
• Atoms have a central core called a nucleus and a surrounding electron cloud
• The nucleus contains protons (positively charged) and neutrons (uncharged), while the electron cloud contains electrons (negatively charged)
• The number of protons and neutrons in a nucleus and the number and arrangement of electrons in the electron cloud determine an atom's chemical and physical properties
• Elements are identified by their atomic number, which is the number of protons in the nucleus of one of its atoms
• Atoms can have different atomic masses due to varying numbers of neutrons, known as isotopes
• Energy-level shells or clouds of electrons influence the way atoms react with each other
• Compounds are composed of atoms of two or more elements chemically united in fixed proportions
• Chemical bonds hold atoms together in molecules, with three types of bonds: covalent, hydrogen, and ionic
• In covalent bonding, atoms share outer-shell electrons to form a bond
• Electron arrangement in atoms:

  • Electrons are arranged in energy-level shells around the nucleus
  • Electrons are not found in a definite location but travel rapidly in a three-dimensional space around the nucleus
• Covalently bonded molecule - Hydrogen (H2):

  • A single covalent bond forms when two hydrogen atoms share a pair of electrons
• Hydrogen bonds:

  • Form when hydrogen bonds to certain other atoms like O, N, or Fe
  • Hydrogen electron is drawn toward another atom, leaving a proton behind
  • Hydrogen atom gains a slight positive charge
  • Weak attraction called a hydrogen bond forms
• Ionic bonds:

  • Form when an atom gains or loses electrons and acquires an electrical charge
  • Attracts an atom or group of atoms with an opposite charge
• Acids, Bases, and Buffers:

  • Electrolytes conduct electricity when in solution
  • Acids release hydrogen ions (H+) when dissolved in water
  • Bases release hydroxyl ions (OH-) when dissolved in water
  • pH scale measures acidity and alkalinity
  • Buffers resist changes in pH by accepting or donating H+ ions
• Organic molecules can be divided into two groups:

  • Organic molecules, which contain carbon atoms
  • Inorganic molecules, which lack carbon atoms
• The most important characteristics of organic molecules depend on the properties of carbon, which is the indispensable element for all life
• Carbon atoms have four electrons in their outer orbital and must share four additional electrons by covalent bonding with other atoms to fill their outer orbital with eight electrons
• Hydrocarbons are organic molecules that contain only carbon and hydrogen, forming the framework of all organic molecules
• Lipids are nonpolar organic molecules that are insoluble in polar water but soluble in nonpolar organic solvents like ether, alcohol, and chloroform
• Fats, the most common lipids in animals, build cell parts and supply energy for cellular activities
• Lipid molecules are primarily composed of carbon, hydrogen, and oxygen atoms, with some containing small amounts of phosphorus and nitrogen
• The building blocks of fat molecules are fatty acids and glycerol
• Unsaturated fats have low melting points because their chains bend at the double bonds, preventing close alignment and leading to fluidity at room temperature
• Phospholipids are important constituents of cell membranes, with a structure containing a glycerol portion, two fatty acid chains, and a phosphate and nitrogen-containing group
• Phospholipids have a hydrophilic "head" composed of phosphate and nitrogen groups and a hydrophobic "tail" made of the fatty acid portion
• Phospholipids are the major structural components of cell membranes due to their solubility properties
• Fatty acids are the building blocks of fats and are composed of carbon and hydrogen atoms
• Triglycerides are formed by the combination of three fatty acids with a glycerol molecule
• Fatty acids can differ in the length of their carbon chains and in the ways the carbon atoms combine
• Saturated fatty acids have single carbon-carbon bonds and each carbon atom binds to as many hydrogen atoms as possible
• Unsaturated fatty acids have one or more double bonds between carbon atoms, replacing some hydrogen atoms