UNIT 1
1. The Chemistry of Life
● Atoms, Elements, and Compounds
○ Atoms: Basic unit of matter consisting of protons, neutrons, and electrons.
○ Elements: Pure substances made of only one type of atom (e.g., Carbon,
Oxygen, Nitrogen).
○ Compounds: Substances made of two or more elements chemically bonded
(e.g., H2O).
● Chemical Bonds
○ Covalent Bonds: Atoms share electrons (e.g., O-H in water).
○ Ionic Bonds: Electrons are transferred from one atom to another, resulting in
charged ions.
○ Hydrogen Bonds: Weak bonds between a hydrogen atom and an
electronegative atom (often oxygen or nitrogen).
○ Van der Waals Interactions: Weak attractions between molecules due to
transient changes in electron distribution.
● Water and Its Properties
○ Polarity: Water is polar, meaning it has a partial positive charge on hydrogen and
a partial negative charge on oxygen.
○ Hydrogen Bonding: This gives water its high cohesion, high specific heat, high
surface tension, and the ability to dissolve many substances (solvent properties).
○ Properties of Water:
■ Cohesion and Adhesion: Water molecules stick to each other (cohesion)
and to other surfaces (adhesion).
■ High Specific Heat: Water resists changes in temperature.
■ High Heat of Vaporization: Water absorbs a lot of heat when it
evaporates.
■ Universal Solvent: Due to its polarity, water dissolves many ionic and
polar compounds.
2. Macromolecules
● Carbohydrates
○ Function: Quick energy, structure (e.g., cellulose in plants).
○ Monomer: Monosaccharides (e.g., glucose).
○ Polymers: Disaccharides (e.g., sucrose), polysaccharides (e.g., starch, glycogen,
cellulose).
● Lipids
○ Function: Long-term energy storage, insulation, cell membrane structure.
○ Types: Fats, phospholipids, steroids.
, ○ Monomer: Fatty acids and glycerol.
○ Phospholipids form the lipid bilayer of cell membranes.
● Proteins
○ Function: Enzyme catalysis, structure, transport, cell communication, movement.
○ Monomer: Amino acids.
○ Polymers: Polypeptides.
○ Levels of structure:
■ Primary: Sequence of amino acids.
■ Secondary: Alpha-helices and beta-pleated sheets.
■ Tertiary: 3D folding of the protein.
■ Quaternary: Multiple polypeptide chains interacting.
● Nucleic Acids
○ Function: Store and transmit genetic information.
○ Monomer: Nucleotides.
○ Types: DNA and RNA.
○ DNA is double-stranded, RNA is single-stranded.
○ DNA stores genetic information, RNA is involved in protein synthesis.
3. Enzyme Structure and Function
● Enzymes: Proteins that speed up chemical reactions by lowering activation energy.
● Substrate Specificity: Each enzyme works with a specific substrate due to its active
site shape.
● Factors Affecting Enzyme Activity:
○ Temperature and pH: Enzymes have an optimal range.
○ Concentration of Substrate and Enzyme: Higher concentration increases the
rate of reaction.
○ Inhibitors: Competitive inhibitors block the active site, non-competitive inhibitors
change the enzyme's shape.
4. Cellular Biology Basics
● Structure of Cells
○ Prokaryotic Cells: Lack a nucleus and membrane-bound organelles (e.g.,
bacteria).
○ Eukaryotic Cells: Have a nucleus and membrane-bound organelles (e.g., plant
and animal cells).
● Organelles
○ Nucleus: Contains DNA.
○ Ribosomes: Protein synthesis.
○ Endoplasmic Reticulum (ER): Rough ER (protein synthesis) and Smooth ER
(lipid synthesis).
○ Golgi Apparatus: Modifies, packages, and ships proteins.
○ Mitochondria: Energy production via cellular respiration.
, ○ Chloroplasts (in plants): Photosynthesis.
○ Lysosomes: Breakdown of waste materials.
● Cell Membrane
○ Phospholipid Bilayer: Hydrophobic tails and hydrophilic heads.
○ Transport Proteins: Facilitate the movement of molecules across the
membrane.
○ Fluid Mosaic Model: The membrane is fluid and contains various proteins.
5. Cell Communication and Signaling
● Signal Transduction Pathways: Cells communicate using chemical signals that bind to
receptors and cause cellular responses.
● Types of Signals:
○ Autocrine: Signal affects the same cell.
○ Paracrine: Signal affects nearby cells.
○ Endocrine: Signals travel through the bloodstream to distant cells.
● Receptors:
○ Membrane-bound receptors: For hydrophilic signals (e.g., peptide hormones).
○ Intracellular receptors: For hydrophobic signals (e.g., steroid hormones).
● Feedback Mechanisms:
○ Negative Feedback: Reduces the effect of a stimulus, stabilizing systems (e.g.,
regulation of body temperature).
○ Positive Feedback: Amplifies the effect of a stimulus (e.g., childbirth).
UNIT 2
1. Cell Theory and Types of Cells
● Cell Theory:
○ All living organisms are made of cells.
○ The cell is the basic unit of life.
○ All cells come from pre-existing cells.
● Prokaryotic Cells:
○ No nucleus or membrane-bound organelles.
○ Examples: Bacteria and Archaea.
○ Key structures: Cell wall, plasma membrane, ribosomes, nucleoid (region where
DNA is located), and sometimes flagella or pili.
● Eukaryotic Cells:
○ Have a nucleus and membrane-bound organelles.
○ Examples: Plants, animals, fungi, and protists.
○ Organelles: Nucleus, mitochondria, endoplasmic reticulum (ER), Golgi apparatus,
lysosomes, vacuoles, chloroplasts (in plants).
, 2. Cell Membranes
● Structure of the Plasma Membrane:
○ Phospholipid Bilayer: Hydrophobic tails face inward, and hydrophilic heads face
outward, creating a semi-permeable barrier.
○ Membrane Proteins:
■ Integral proteins: Embedded within the membrane (e.g., channel
proteins, carrier proteins).
■ Peripheral proteins: Attached to the surface of the membrane.
■ Glycoproteins and Glycolipids: Proteins and lipids with carbohydrate
chains that help with cell recognition and communication.
● Fluid Mosaic Model: The membrane is dynamic and flexible, with proteins "floating" in
the lipid bilayer like a mosaic.
● Functions of the Plasma Membrane:
○ Selective permeability: Regulates what enters and leaves the cell.
○ Cell communication and recognition (e.g., via receptors and signaling molecules).
○ Transport of materials (active and passive transport mechanisms).
3. Transport Across Membranes
● Passive Transport: Movement of molecules from high to low concentration without
energy.
○ Diffusion: Movement of small or nonpolar molecules (e.g., O2, CO2) directly
through the lipid bilayer.
○ Facilitated Diffusion: Transport of larger or polar molecules (e.g., glucose, ions)
through membrane proteins.
○ Osmosis: Diffusion of water across a selectively permeable membrane.
■ Hypertonic: Higher solute concentration outside the cell (cell shrinks).
■ Hypotonic: Lower solute concentration outside the cell (cell swells).
■ Isotonic: Equal solute concentration inside and outside the cell (no
change in cell size).
● Active Transport: Movement of molecules from low to high concentration, requiring
energy (ATP).
○ Sodium-Potassium Pump: Active transport pump that moves sodium ions out
and potassium ions into the cell.
○ Endocytosis: The cell engulfs materials by forming vesicles (e.g., phagocytosis,
pinocytosis).
○ Exocytosis: The cell expels materials via vesicles fusing with the plasma
membrane.
4. Endomembrane System and Organelles
● Nucleus: The control center of the cell, housing the cell’s genetic material (DNA).
