Essential Chemistry for Biology

Matter: Elements and Compounds

All living and nonliving things are composed of matter, which exists as elements and compounds.

• Element: A substance that cannot be broken down into other substances by chemical means. Examples include oxygen (O), carbon (C), and hydrogen (H).

• Compound: A substance consisting of two or more elements combined in a fixed ratio. Example: Water (H2O).

Atoms

Atoms are the smallest units of elements that retain their properties.

• Structure: Atoms consist of a nucleus (protons and neutrons) and electrons orbiting the nucleus.

• Atomic Number: Number of protons in an atom.

• Mass Number: Sum of protons and neutrons.

Chemical Bonding

Atoms combine through chemical bonds to form molecules and compounds.

• Covalent Bonds: Atoms share electrons. Example: H2O.

• Ionic Bonds: Electrons are transferred from one atom to another, creating charged ions. Example: NaCl.

• Hydrogen Bonds: Weak attractions between polar molecules, important in water and DNA structure.

Water and Life; Acids, Bases, and pH

Water is essential for life due to its unique properties.

• Cohesion: Water molecules stick together via hydrogen bonds.

• Solvent Properties: Water dissolves many substances, facilitating chemical reactions.

• Acids: Substances that increase H+ concentration in solution.

• Bases: Substances that decrease H+ concentration.

• pH Scale: Measures acidity or basicity (0 = most acidic, 14 = most basic, 7 = neutral).

Example: Human blood has a pH around 7.4, maintained by buffers.

The Molecules of Life

Carbon Chemistry; Giant Molecules from Smaller Building Blocks

Carbon forms the backbone of biological molecules due to its ability to form four covalent bonds.

• Macromolecules: Large molecules built from smaller units (monomers).

• Polymerization: Process of linking monomers to form polymers.

Carbohydrates

Carbohydrates are sugars and their polymers, serving as energy sources and structural materials.

• Monosaccharides: Simple sugars (e.g., glucose).

• Disaccharides: Two monosaccharides joined (e.g., sucrose).

• Polysaccharides: Long chains (e.g., starch, cellulose, glycogen).

Lipids

Lipids are hydrophobic molecules, including fats, oils, and steroids.

• Fats: Store energy; composed of glycerol and fatty acids.

• Phospholipids: Major components of cell membranes.

• Steroids: Include hormones like cholesterol.

Proteins

Proteins are polymers of amino acids, performing diverse functions in cells.

• Structure: Primary, secondary, tertiary, and quaternary levels.

• Functions: Enzymes, structural support, transport, signaling.

Nucleic Acids

Nucleic acids (DNA and RNA) store and transmit genetic information.

• Monomers: Nucleotides (sugar, phosphate, nitrogenous base).

• DNA: Double helix structure; stores genetic code.

• RNA: Single-stranded; involved in protein synthesis.

A Tour of the Cell

Microscopes

Microscopes are essential tools for studying cells.

• Light Microscopes: Use light to view living cells.

• Electron Microscopes: Provide higher resolution images of cell structures.

The Two Major Categories of Cells

Cells are classified as prokaryotic or eukaryotic.

• Prokaryotic Cells: Lack a nucleus; found in bacteria and archaea.

• Eukaryotic Cells: Have a nucleus and membrane-bound organelles; found in plants, animals, fungi, and protists.

An Overview of Eukaryotic Cells

Eukaryotic cells contain various organelles with specialized functions.

• Nucleus: Contains genetic material (DNA).

• Cytoplasm: Fluid region containing organelles.

• Other Organelles: Mitochondria, endoplasmic reticulum, Golgi apparatus, lysosomes, etc.

Membrane Structure

Cell membranes are composed of a phospholipid bilayer with embedded proteins.

• Fluid Mosaic Model: Describes the dynamic arrangement of lipids and proteins.

• Selective Permeability: Membranes regulate the movement of substances in and out of cells.

The Endomembrane System

The endomembrane system coordinates the synthesis and transport of cellular products.

• Includes: Nuclear envelope, endoplasmic reticulum (ER), Golgi apparatus, lysosomes, vacuoles, and plasma membrane.

• Function: Synthesis, modification, and transport of proteins and lipids.

Chloroplasts and Mitochondria

These organelles are involved in energy transformation.

• Chloroplasts: Site of photosynthesis in plant cells.

• Mitochondria: Site of cellular respiration in all eukaryotic cells.

The Working Cell

Conservation of Energy, Entropy, and Chemical Energy

Cells obey the laws of thermodynamics.

• First Law: Energy cannot be created or destroyed, only transformed.

• Second Law: Every energy transfer increases the entropy (disorder) of the universe.

• Chemical Energy: Stored in the bonds of molecules; used for cellular work.

ATP

Adenosine triphosphate (ATP) is the main energy currency of the cell.

• Structure: Adenine, ribose, and three phosphate groups.

• Function: Provides energy for cellular processes by hydrolysis of its terminal phosphate bond.

Equation:

Enzymes

Enzymes are biological catalysts that speed up chemical reactions without being consumed.

• Active Site: Region where substrate binds.

• Specificity: Each enzyme acts on a specific substrate.

Membrane Function

Cell membranes control the movement of substances via various transport mechanisms.

• Passive Transport: Diffusion and facilitated diffusion (no energy required).

• Active Transport: Movement against concentration gradient (requires energy).

Osmosis and Water Balance

Osmosis is the diffusion of water across a selectively permeable membrane.

• Isotonic Solution: No net water movement.

• Hypotonic Solution: Water enters the cell; cell may swell.

• Hypertonic Solution: Water leaves the cell; cell may shrink.

Cellular Respiration

Energy Flow and Chemical Cycling in the Biosphere

Energy flows through ecosystems, while chemicals are recycled.

• Producers: Convert solar energy to chemical energy (e.g., plants).

• Consumers: Obtain energy by eating other organisms.

Cellular Respiration: Equation and the Role of Oxygen

Cellular respiration releases energy from glucose in the presence of oxygen.

Equation:

• Oxygen: Final electron acceptor in the electron transport chain.

Cellular Respiration - An Overview

Cellular respiration occurs in three main stages:

1. Glycolysis

2. Krebs Cycle (Citric Acid Cycle)

3. Electron Transport Chain

Cellular Respiration - The Three Stages

• Glycolysis: Occurs in cytoplasm; breaks glucose into pyruvate; produces small amount of ATP and NADH.

• Krebs Cycle: Occurs in mitochondria; completes breakdown of glucose; produces CO2, ATP, NADH, and FADH2.

• Electron Transport Chain: Uses NADH and FADH2 to generate large amounts of ATP; oxygen is required.

Fermentation

Fermentation is an anaerobic process that allows cells to produce ATP without oxygen.

• Lactic Acid Fermentation: Occurs in muscle cells; produces lactic acid.

• Alcoholic Fermentation: Occurs in yeast; produces ethanol and CO2.

Photosynthesis

The Basics of Photosynthesis

Photosynthesis converts solar energy into chemical energy in plants, algae, and some bacteria.

• Occurs in: Chloroplasts of plant cells.

An Overview of Photosynthesis

Photosynthesis consists of two main stages: the light reactions and the Calvin cycle.

Equation:

The Light Reactions

Light reactions capture solar energy and convert it to chemical energy (ATP and NADPH).

• Location: Thylakoid membranes of chloroplasts.

• Products: ATP, NADPH, and O2 (from splitting water).

The Calvin Cycle

The Calvin cycle uses ATP and NADPH to convert CO2 into glucose.

• Location: Stroma of chloroplasts.

• Product: Glucose and other organic molecules.

Additional info: This guide expands on the provided outline with definitions, examples, and equations for clarity and completeness.