Water Properties and Behaviors

Study Notes

Water

Polarity: Water is a polar molecule due to the uneven sharing of electrons between the oxygen and hydrogen atoms.
Hydrogen bonding: The partial positive charge on the hydrogen atom of one water molecule attracts the partial negative charge on the oxygen atom of another water molecule, resulting in a hydrogen bond.
Cohesion: Water molecules stick to each other due to hydrogen bonding. This is why water forms droplets.
Adhesion: Water molecules stick to other polar substances, such as glass. This is why water wets surfaces.
Capillary action: The combination of cohesion and adhesion allows water to move up narrow tubes, like the xylem in plants.
Surface tension: Water molecules at the surface exhibit stronger cohesive forces than the water molecules below, resulting in surface tension. This is why insects can walk on water.
Universal solvent: Water is a good solvent because it can dissolve many polar and ionic substances due to its polarity.
Density: Water is less dense as a solid (ice) than as a liquid. This is why ice floats.
High heat capacity: Water can absorb a lot of heat energy without a significant change in temperature. This helps to regulate body temperature in organisms.
High heat of vaporization: Water requires a lot of heat energy to change from a liquid to a gas. This is why sweating helps to cool us down.
Buffers: Buffers are solutions that resist changes in pH. They are important for maintaining a stable internal environment in living organisms.
pH: pH is a measure of the acidity or alkalinity of a solution. pH values range from 0 to 14, with 7 being neutral, below 7 being acidic, and above 7 being alkaline.

Carbohydrates

Monomers and Polymers: Monomers are small, repeating units that make up larger molecules called polymers.
Carbohydrate Monomers: The monomer of carbohydrates is a monosaccharide, such as glucose, fructose, and galactose.
Carbohydrate Polymers: Polymers of carbohydrates are called polysaccharides. Examples include starch, glycogen, and cellulose.
Macromolecule Composition: Carbohydrates are made up of the elements carbon (C), hydrogen (H), and oxygen (O).
Hydrogen Bonds and Covalent Bonds: Carbohydrates are held together by covalent bonds within the molecule and hydrogen bonds between molecules.

Proteins

Importance of Carbon Valence: Carbon has four valence electrons, allowing it to bond with up to four other atoms, forming complex molecules like proteins.
Amino Acid Structure: An amino acid consists of a central carbon atom bonded to an amino group (-NH2), a carboxyl group (-COOH), a hydrogen atom (-H), and a variable side chain (R group).
Protein Polymerization: Proteins are polymers made up of amino acid monomers.
Dehydration Synthesis and Peptide Bonds: The formation of a peptide bond between two amino acids involves the removal of a water molecule through a process called dehydration synthesis.
Protein Hydrolysis: The breakdown of a protein into its constituent amino acids occurs through the addition of a water molecule, called hydrolysis.
Enzyme Function: Enzymes are proteins that catalyze (speed up) biochemical reactions. They are essential for all biological processes.
Protein Folding: The specific three-dimensional structure of a protein is crucial for its function. The folding process is influenced by interactions between amino acid side chains.
Levels of Protein Folding:
- Primary Structure: The linear sequence of amino acids.
- Secondary Structure: Local folding patterns, such as alpha helices and beta sheets.
- Tertiary Structure: The overall three-dimensional shape of a single polypeptide chain.
- Quaternary Structure: The arrangement of multiple polypeptide chains (subunits) in a protein.

Nucleic Acids

DNA and RNA: DNA (Deoxyribonucleic Acid) and RNA (Ribonucleic Acid) are nucleic acids that store and transmit genetic information.
Central Dogma: The central dogma of molecular biology describes the flow of genetic information from DNA to RNA to protein.
Nucleotide Structure: A nucleotide is composed of a sugar molecule, a phosphate group, and a nitrogenous base.
DNA Bases: Adenine (A), guanine (G), cytosine (C), and thymine (T).
RNA Bases: Adenine (A), guanine (G), cytosine (C), and uracil (U).
Nucleic Acid Polymerization: Nucleic acids are polymers made up of nucleotide monomers.
Dehydration Synthesis and Phosphodiester Bonds: The formation of a phosphodiester bond between two nucleotides involves the removal of a water molecule through a process called dehydration synthesis.