Introduction to Biology

Domains of Life

The domain system classifies all living organisms into three major groups based on genetic and cellular differences.

• Bacteria: Single-celled prokaryotes with no nucleus.

• Archaea: Single-celled prokaryotes, often found in extreme environments; genetically distinct from bacteria.

• Eukarya: Organisms with cells containing a nucleus; includes animals, plants, fungi, and protists.

Hierarchy of Living Organisms

Biological organization follows a hierarchy from smallest to largest:

• Atom → Molecule → Organelle → Cell → Tissue → Organ → Organ System → Organism

Shared Characteristics of Living and Nonliving Things

• Living things: Organization, metabolism, responsiveness, growth, development, reproduction, homeostasis.

• Nonliving things: May have structure but lack metabolism, growth, and reproduction.

Scientific Method

The scientific method is a systematic approach to investigation.

1. Observation

2. Hypothesis

3. Experiment

4. Data Collection

5. Analysis

6. Conclusion

Homeostasis

Homeostasis is the maintenance of a stable internal environment despite external changes.

• Example: Regulation of body temperature.

Chemistry of Life

Most Abundant Elements in Humanity

• Carbon (C)

• Hydrogen (H)

• Oxygen (O)

• Nitrogen (N)

• Phosphorus (P)

• Sulfur (S)

Reductionism

Reductionism is the approach of understanding complex systems by studying their simpler components.

• Example: Studying cell organelles to understand cell function.

Atoms, Elements, and Molecules

• Element: Pure substance consisting of one type of atom.

• Molecule: Two or more atoms bonded together.

Radioisotope Technology

Radioisotopes are used in medical imaging, cancer treatment, and biological research.

• Example: PET scans use radioisotopes to visualize metabolic activity.

Bond Types

• Ionic Bonds: Transfer of electrons between atoms, forming charged ions.

• Covalent Bonds: Sharing of electrons between atoms.

• Hydrogen Bonds: Weak attraction between a hydrogen atom and another electronegative atom.

Polarity

• Polar Molecule: Unequal sharing of electrons, resulting in partial charges (e.g., water).

• Nonpolar Molecule: Equal sharing of electrons, no charge separation (e.g., methane).

Acids, Bases, and pH

• Acidic: pH < 7

• Basic (Alkaline): pH > 7

• Neutral: pH = 7

Atoms and Charge

• Atoms can gain or lose electrons to become ions.

• Negatively charged elements (anions) attract positively charged elements (cations).

Structure & Function of Cells

Cell Organelles: Names, Functions, and Shapes

• Nucleus: Contains DNA; round or oval.

• Mitochondria: Site of ATP production; bean-shaped.

• Ribosomes: Protein synthesis; small, spherical.

• Endoplasmic Reticulum (ER): Synthesis and transport; network of membranes.

• Golgi Apparatus: Modifies and packages proteins; stack of flattened sacs.

• Lysosomes: Digestion of cellular waste; spherical.

• Plasma Membrane: Boundary of cell; flexible, phospholipid bilayer.

Cell Size and Surface Area

Cell size is limited by surface area-to-volume ratio. Smaller cells have a higher ratio, allowing efficient exchange of materials.

• Formula: for a cube

• Formula: for a cube

Microscopy Types

• Light Microscopy: Used for viewing live cells and tissues.

• Electron Microscopy: Used for high-resolution images of cell structures.

• Fluorescence Microscopy: Used to visualize specific molecules with fluorescent tags.

DNA Importance

DNA stores genetic information, directs cell activities, and is essential for inheritance.

• Example: DNA replication ensures genetic continuity.

Chemistry & Transport in Cells

Diffusion

Diffusion is the movement of molecules from high to low concentration.

• Example: Oxygen diffuses into cells.

Plasma Membrane Structure

• Composed of a phospholipid bilayer, proteins, cholesterol, and carbohydrates.

What Can and Can't Pass Through the Plasma Membrane

• Can Pass: Small, nonpolar molecules (e.g., O2, CO2), some small polar molecules (e.g., H2O).

• Cannot Pass: Large molecules, ions, and most polar molecules without transport proteins.

Active Transport

Active transport moves substances against their concentration gradient using energy (ATP).

• Example: Sodium-potassium pump.

Isotonic Solution

An isotonic solution has equal solute concentration inside and outside the cell, causing no net movement of water.

• Cells retain their normal shape in isotonic solutions.

Cellular Respiration

Glycolysis

Glycolysis is the first step in cellular respiration, breaking down glucose into pyruvate and producing ATP.

• Occurs in the cytoplasm.

• Produces 2 ATP molecules per glucose.

Electron Transport Chain & ATP Production

• Most ATP is produced in the ATP synthase protein complex during the electron transport chain.

• Location: Inner mitochondrial membrane.

Electron Carriers in Citric Acid Cycle

• NAD+ and FAD are electron carriers.

• They gain electrons from metabolic reactions and transfer them to the electron transport chain.

Tissues & Organ Systems

Types of Connective Tissues

• Loose Connective Tissue: Supports and binds other tissues.

• Dense Connective Tissue: Provides strength (e.g., tendons, ligaments).

• Adipose Tissue: Stores fat.

• Cartilage: Flexible support.

• Bone: Rigid support.

• Blood: Transport of substances.

Types of Tissues and Their Functions

• Epithelial Tissue: Covers surfaces, lines cavities.

• Connective Tissue: Supports, protects, binds other tissues.

• Muscle Tissue: Movement.

• Nervous Tissue: Communication, control.

Location of Each Tissue Type

• Epithelial: Skin, lining of digestive tract.

• Connective: Tendons, fat, bone, blood.

• Muscle: Skeletal muscles, heart, stomach.

• Nervous: Brain, spinal cord, nerves.

Type of Muscle in the Stomach

• Smooth Muscle: Involuntary, found in walls of stomach and other organs.

Types of Junctions

• Tight Junctions: Prevent leakage between cells.

• Desmosomes: Provide mechanical strength.

• Gap Junctions: Allow communication between cells.

Table: Types of Tissues and Their Functions