Hydrogen Bonds and Their Importance

Hydrogen Bonds

• Formed between positively charged hydrogen and negatively charged atoms (O, N, F) in other molecules.
• In water, hydrogen of one molecule bonds with oxygen of another, influencing the shape of complex molecules.

Solubility and Dissociation

• Solubility: Ability of a substance to dissolve in another; sugar and salt dissolve in water, but oils do not.
• Dissociation: In ionic compounds, cations and anions separate in water due to opposite attractions from water molecules.

Electrolytes and Nonelectrolytes

• Electrolytes: Solutions formed by dissociation of ions, capable of conducting electricity.
• Nonelectrolytes: Molecules that dissolve in water but do not dissociate, thus do not conduct electricity.
• Proper electrolyte balance is crucial for physiological processes.

Synthesis Reactions

• Two or more reactants combine to form a larger product.
• Also known as anabolism; energy is stored in chemical bonds.
• Examples include the formation of carbohydrates, proteins, lipids, and nucleic acids.

Decomposition Reactions

• Large reactants are broken down into smaller products; known as catabolism.
• Energy is released when chemical bonds break.
• Hydrolysis reactions involve water splitting to form products.

Reversible Reactions

• Reactions can proceed in both directions, either forming products or reverting to reactants.
• At equilibrium, the rate of formation of products equals the rate of formation of reactants.

Inorganic Chemistry

• Focuses on substances without carbon-hydrogen bonds; examples include water, oxygen, and calcium phosphate.
• Organic chemistry studies carbon-containing substances.

Water

• Polar molecule influencing interactions with hydrophilic (water-attracted) and hydrophobic (water-fearing) substances.
• Cohesion (water attraction to itself) creates surface tension; adhesion (water attraction to other molecules) aids plant water transport.
• Constitutes 50-60% of the body and 92% of blood.

Acids and Bases

• Acid: Proton donor that releases hydrogen ions.
• Base: Proton acceptor that binds to or accepts hydrogen ions.

The pH Scale

• Measures hydrogen ion concentration in solutions.
• Neutral is pH 7; acidic is below 7; alkaline (basic) is above 7.

Normal and Abnormal Body pH

• Normal pH for blood ranges from 7.35 to 7.45.
• Acidosis occurs below 7.35, leading to depression of the nervous system.
• Alkalosis occurs above 7.45, causing nervous system excitability.

Organic Molecules

• Carbohydrates: Composed of C, H, O; categorized into monosaccharides, disaccharides, polysaccharides; serve as energy sources.
• Lipids: Mainly C, H, O; includes trans fats which pose cardiovascular risks; critical for cell membrane structure.

Lipids: Phospholipids and Steroids

• Phospholipids: One fatty acid replaced with phosphate; crucial for cell membrane structure due to their amphipathic nature.
• Steroids: Lipids with a four-ring structure; includes cholesterol (cell membranes) and reproductive hormones (estrogen, testosterone).

Proteins and Amino Acids

• Proteins: Composed of amino acids linked by peptide bonds through dehydration synthesis.
• Amino acids consist of an amino group, a carboxyl group, a central carbon, and an R side chain distinguishing them.

Protein Structure

• Primary Structure: Sequence of amino acids.
• Secondary Structure: Hydrogen bonds form pleated sheets or helices.
• Tertiary Structure: Large-scale folding stabilized by disulfide bonds; determines protein function.
• Quaternary Structure: Association of multiple protein subunits.

Nucleic Acids: DNA and RNA

• Composed of nucleotides, including DNA and RNA, essential for genetic information.
• DNA consists of two strands with complementary bases (A-T, G-C) forming a double helix.

Structure of DNA

• Sugar-phosphate backbones running in opposite directions; genes coded by base sequences dictate protein synthesis.