Chemical Reactions and Carbon Compounds

Chemical Reactions and Energy

• Living organisms undergo thousands of chemical reactions, crucial to life processes.
• These reactions involve the rearrangement of atoms and bonds.
• Chemical reactions are often complex and multi-step sequences.
• Chemical reactions involve reactants (starting materials) transforming into products (resulting materials).
• The number of each atom type remains the same during a chemical reaction.

Carbon Compounds

• Organic compounds contain carbon atoms covalently bonded to other carbon atoms and other elements (like hydrogen, oxygen, and nitrogen).
• Carbon's capacity to bond with itself creates a large variety of organic compounds.
• Carbon forms four covalent bonds.
• Carbon can form chains, branched chains, or rings.
• Carbon bonding creates diverse organic compound structures.

Carbon Bonding

• Each line in structural diagrams represents a covalent bond (where two atoms share a pair of electrons).
• Single bonds are where two atoms share a pair of electrons.
• Carbon can share two or three pairs of electrons in double or triple bonds (respectively).
• Double bonds are shown with two parallel lines and triple bonds show with three parallel lines.

Water

• Water is a polar molecule, meaning it has an uneven distribution of electrical charge.
• It has a positive and a negative side.
• Its polarity makes water very effective at dissolving other polar substances (like sugars and some proteins ) and ionic compounds (like NaCl).
• Water molecules attract each other through hydrogen bonds.

Hydrogen Bonding

• Hydrogen bonding is the attraction between two water molecules.
• Water has strong cohesive properties (attraction to itself).
• Water also exhibits adhesion (attraction to other substances ).
• Water's hydrogen bonds enable capillarity ( the movement of water against gravity in narrow tubes).
• Water has high specific heat capacity, maintaining temperature stability within organisms.

Enzymes

• Enzymes are organic catalysts, crucial for chemical reactions.
• Most enzymes are proteins.
• Enzymes reduce activation energy by lowering the energy needed to initiate reactions.
• Enzyme action depends on a specific fit between the enzyme (lock) and its substrate (key), to perform their function.
• Enzyme shape changes slightly to grip and adjust reacting molecules (substrate), reducing the activation energy needed for reaction.
• Enzymes speed up chemical reactions but are not used up in the process.

Redox Reacions

• Redox reactions are electron transfer reactions between atoms.
• Reactions involving electron transfer are vital to life.
• Oxidation is the loss of electrons.
• Reduction is the gain of electrons.
• Oxidation and reduction always happen together in redox reactions.
• Redox reactions transfer energy and drive many important cellular functions.

Activation Energy

• Activation energy is the initial energy needed for a chemical reaction to begin.
• Reactions require some activation energy even when they release energy ultimately or take in energy.
• Catalysts, like enzymes lower the activation energy.
• The shape fit of an enzyme to substrate affects the activation energy.

pH

• The pH scale measures the concentration of hydronium ions (H₃O⁺) and hydroxide ions (OH⁻) in a solution, ranging from 0-14.
• A pH of 7 is neutral. Values below 7 are acidic; values above 7 are basic.
• Living organisms maintain specific pH ranges within their systems.
• Buffers are chemical substances that neutralize small amounts of added acid or base, to maintain a stable pH.

Energy Transfer

• Energy in the form of ATP (adenosine triphosphate) powers many life processes.
• Reactions that release energy are called exergonic.
• Reactions that absorb energy are called endergonic.
• ATP stores energy in high-energy phosphate bonds.
• Release of energy from ATP (breaking phosphate bonds) is used to drive many necessary reactions.

Molecules of Life

• The four major classes of organic molecules essential to life include carbohydrates, lipids, proteins, and nucleic acids.
• Carbohydrates consist of carbon, hydrogen, and oxygen atoms in a ratio of about 1:2:1.
• Monosaccharides are simple sugars (one sugar).
• Disaccharides are two linked monosaccharides.
• Polysaccharides are many linked monosaccharides.
• Lipids are large nonpolar organic molecules.
• Lipids primarily consist of carbon and hydrogen atoms.
• Fats, oils, and waxes are examples of lipids.
• Fatty acids are unbranched carbon chains with carboxyl and hydrocarbon ends.
• Fatty acids may be saturated or unsaturated.
• Proteins are macromolecules (large polymers) constructed from amino acids.
• Amino acid monomers link in condensation reactions forming peptide bonds and polypeptides, potentially forming larger proteins.
• Proteins' structure and shape enable their diverse functions.
• Proteins have an overall shape (3D structure).

Organic Compound Types & Polymers

• Monomers link through condensation reactions to form polymers.
• Hydrolysis reactions break polymers into monomers by adding water.
• Functional groups are clusters of atoms that influence properties and reactions of compounds.
• Hydroxyl (-OH) is an important functional group. Alcohols contain hydroxyl groups.