뒤로Chemistry of Life - Anatomy & Physiology
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Matter is anything that takes up space and has mass. It is composed of chemical elements, which are substances containing only one type of atom.
The major elements essential for life are carbon, hydrogen, oxygen, and nitrogen, making up about 96% of living matter.
An atom consists of protons (positive charge) and neutrons (neutral) in the nucleus, and electrons (negative charge) orbiting the nucleus.
Atomic number is the number of protons in an atom's nucleus. Atomic mass is the sum of protons and neutrons in the nucleus.
Isotopes are atoms of the same element with the same number of protons but different numbers of neutrons, resulting in different mass numbers.
The number and arrangement of valence electrons in the outermost shell determine an atom's chemical behavior and reactivity.
The octet rule states that atoms tend to form bonds to have eight electrons in their valence shell, achieving stability.
An ion is a charged atom formed when an atom gains or loses electrons to complete its valence shell. Positive ions are cations, negative ions are anions.
The three main types of chemical bonds are ionic bonds, covalent bonds (polar and nonpolar), and hydrogen bonds.
Ionic bonds form by electrical attraction between oppositely charged ions (cations and anions), often resulting from electron transfer.
Covalent bonds involve sharing of valence electrons between atoms. They can be nonpolar (equal sharing) or polar (unequal sharing).
Electronegativity measures an atom's attraction for shared electrons. Differences in electronegativity cause polar covalent bonds.
Hydrogen bonds are weak attractions between partial charges on different molecules or parts of large molecules, crucial for water's properties and biomolecule structure.
Water is essential because of its polarity, ability to form hydrogen bonds, and properties like temperature moderation, solvent versatility, and cohesion.
Water's special properties are: 1) Temperature moderation, 2) Versatile solvent, and 3) Cohesion due to hydrogen bonding.
The pH scale measures acidity from 0 (acidic) to 14 (basic). Biological fluids usually range from pH 6 to 8, with buffers maintaining stable pH.
Buffers minimize pH changes by accepting or donating H+ ions, maintaining stable internal pH in living systems.
Carbon can form four covalent bonds, allowing it to build diverse and complex organic molecules essential for life.
Isomers are molecules with the same formula but different structures. Monomers are small building blocks, and polymers are chains of monomers.
Polymers form by dehydration synthesis (removing water) and break down by hydrolysis (adding water).
The four major classes are carbohydrates, proteins, nucleic acids, and lipids.
Carbohydrates include sugars and polysaccharides, serving as energy sources and structural components.
Proteins are polymers of amino acids that perform diverse functions including structure, transport, signaling, and catalysis.
Nucleic acids (DNA and RNA) store and transmit genetic information and direct protein synthesis.
Lipids are hydrophobic molecules including fats, phospholipids, and steroids, important for energy storage and membrane structure.