Chapter 1: Foundations of Biology

Themes of Life

Biology is the study of living organisms and their interactions with the environment. Understanding the major themes of life helps organize biological knowledge.

• Five Categories of Life: Organization, Information, Energy and Matter, Interactions, Evolution.

• Approaches to Biology: Scientific method, observation, hypothesis, experimentation.

Levels of Biological Organization

Life is organized in a hierarchical manner, from the smallest to the largest scale.

• Hierarchy: Biosphere → Ecosystem → Molecules

Evolution and Natural Selection

Evolution explains the diversity of life through natural selection, where advantageous traits become more common in populations over time.

• Natural Selection: The process by which organisms better adapted to their environment tend to survive and produce more offspring.

Scientific Method

The scientific method is a systematic approach to inquiry in biology.

• Observation → Hypothesis → Experiment: Observations lead to hypotheses, which are tested through experiments.

• Controlled Experiment: An experiment in which only one variable is changed at a time, while all others are kept constant.

Chapter 2: Chemistry of Life

Atoms and Elements

Atoms are the basic units of matter, and elements are defined by the number of protons in their nuclei.

• Atomic Number: Number of protons in an atom; defines the element. (figure our how the shells work)

• Electron Shells: Electrons occupy shells around the nucleus. The first shell holds up to 2 electrons, the second up to 8, etc.

• Valence Electrons: Electrons in the outermost shell; determine chemical reactivity.

• Unpaired Electrons: Atoms with unpaired electrons in their valence shell are more reactive.

Chemical Bonds

Atoms interact to form molecules through various types of chemical bonds.

• Covalent Bonds: Atoms share electrons to fill their valence shells.

• Ionic Bonds: Atoms transfer electrons, resulting in charged ions that attract each other.

• Hydrogen Bonds: Weak attractions between partially charged regions of molecules, important in water and biological macromolecules.

Water and Its Properties

Water is essential for life due to its unique chemical properties.

• Polarity: Water is a polar molecule, allowing it to form hydrogen bonds.

• Cohesion and Adhesion: Water molecules stick to each other (cohesion) and to other surfaces (adhesion).

• Surface Tension: Cohesion at the surface of water creates surface tension.

• Evaporative Cooling: As water evaporates, it removes heat, cooling surfaces.

Acids, Bases, and pH

The pH scale measures the concentration of hydrogen ions in a solution.

• Acid: Substance that increases H+ concentration in solution.

• Base: Substance that decreases H+ concentration.

• pH Scale: Ranges from 0 (most acidic) to 14 (most basic); pH 7 is neutral.

Chapter 3: Biological Macromolecules

Isomers

Isomers are molecules with the same chemical formula but different structures.

• Types of Isomers: Structural, geometric, and enantiomers.

Shape and Function of Molecules

The three-dimensional shape of a molecule affects its biological activity and interactions.

• Drug Design: Shape determines how molecules interact with biological targets.

Macromolecules: Carbohydrates, Proteins, Nucleic Acids, Lipids

Macromolecules are large, complex molecules essential for life.

• Carbohydrates: Energy storage and structural components.

  • Monomer: Monosaccharides ("one" sugar)

  • Polymer: Polysaccharides ("many" sugars)

  • Disaccharide: "two" sugars

• Proteins: Structure, enzymes, transport, signaling.

  • Monomer: Amino acids

  • Polymer: Polypeptides

• Nucleic Acids: Information storage and transfer.

  • Monomer: Nucleotides

  • Polymer: DNA/RNA polynucleotides

• Lipids: Energy storage, membrane structure.

Polymer Formation and Hydrolysis

Polymers are formed by dehydration reactions and broken down by hydrolysis.

• Dehydration Reaction: Removes water to join monomers.

• Hydrolysis: Adds water to break polymers into monomers.

Protein Structure

Proteins have four levels of structure that determine their function.

• Primary: Sequence of amino acids.

• Secondary: Alpha helices and beta sheets.

• Tertiary: 3D folding due to side chain interactions.

• Quaternary: Multiple polypeptide chains together.

ATP: Cellular Energy

ATP (adenosine triphosphate) is the main energy carrier in cells.

• Energy Release: Energy is released when ATP's phosphate bonds are broken.

Chapter 4: Cell Structure and Function

Cell Membranes

Cell membranes are composed of a phospholipid bilayer, providing a barrier and controlling movement of substances.

• Phospholipid Bilayer: Hydrophilic heads face outward, hydrophobic tails face inward.

Organelles and Their Functions

Organelles are specialized structures within cells that perform specific functions.

• Ribosomes: Protein synthesis; can be bound (to rough ER) or free (in cytosol).

• Vacuoles: Storage and transport; larger in plant cells.

• Vesicles: Transport materials within the cell.

• Lysosomes: Digestive enzymes break down waste and foreign material.

• Peroxisomes: Break down fatty acids and detoxify harmful substances.

• Mitochondria: ATP generation, cellular respiration.

• Chloroplasts: Photosynthesis in plant cells.

• Nucleus: DNA storage and gene expression.

• Endoplasmic Reticulum (ER): Protein and lipid synthesis.

  • Rough ER: Protein synthesis (ribosome-studded)

  • Smooth ER: Lipid synthesis, detoxification

• Golgi Apparatus: Protein modification and sorting.

• Cytoskeleton: Cell structure and movement.

Protein Transport and Secretion

Proteins synthesized in the cell may be exported or used internally.

• Pathway for Exported Proteins: DNA → mRNA → Ribosome (Rough ER) → Golgi Apparatus → Transport Vesicle → Cell Membrane

• Pathway for Cytosolic Proteins: DNA → mRNA → Free Ribosome in Cytosol

Endosymbiotic Theory

The endosymbiotic theory explains the origin of mitochondria and chloroplasts in eukaryotic cells.

• Evidence: Both have their own DNA, double membranes, and can reproduce independently within the cell.