Introduction to Biology

Domains of Life

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

• Bacteria: Prokaryotic, unicellular organisms lacking a nucleus.

• Archaea: Prokaryotic, often found in extreme environments, genetically distinct from bacteria.

• Eukarya: Eukaryotic organisms with membrane-bound organelles; includes animals, plants, fungi, and protists.

Hierarchy of Living Organisms

Biological organization ranges from simple to complex structures.

• Atoms → Molecules → Cells → Tissues → Organs → Organ Systems → Organisms → Populations → Communities → Ecosystems → Biosphere

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.

• Examples: Regulation of body temperature, blood pH, and glucose levels.

Characteristics of Living vs. Nonliving Things

• Living: Cellular organization, metabolism, growth, reproduction, response to stimuli, adaptation.

• Nonliving: Lack of cellular structure, metabolism, or reproduction.

Chemistry of Life

Most Abundant Elements in Humans

• Oxygen (O), Carbon (C), Hydrogen (H), Nitrogen (N), Calcium (Ca), Phosphorus (P)

Elements vs. Molecules

• Element: Pure substance consisting of one type of atom (e.g., O2).

• Molecule: Two or more atoms bonded together (e.g., H2O).

Types of Chemical Bonds

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

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

Acids, Bases, and pH

• Acidic: pH < 7

• Basic (Alkaline): pH > 7

• Neutral: pH = 7

Radioisotope Technology

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

• Example: PET scans use radioactive tracers to visualize metabolic activity.

Reductionism

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

• Example: Studying cell organelles to understand cell function.

Atoms and Charge

• Atoms can gain or lose electrons to become ions (charged particles).

• 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 shape.

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

• Ribosomes: Protein synthesis; small, spherical.

• Endoplasmic Reticulum (ER): Rough (with ribosomes) synthesizes proteins; smooth synthesizes lipids.

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

• Lysosomes: Digestive enzymes; spherical.

• Plasma Membrane: Phospholipid bilayer; flexible boundary.

• Cytoskeleton: Structural support; network of fibers.

Cell Size and Surface Area

Smaller cells have a higher surface area-to-volume ratio, facilitating 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: Higher resolution; used for detailed cell structures.

• Fluorescence Microscopy: Visualizes specific molecules using fluorescent tags.

DNA Importance

• DNA stores genetic information, directs cell activities, and enables inheritance.

Chemical Processes in Cells

Diffusion

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

• Example: Oxygen diffuses into cells, carbon dioxide diffuses out.

Plasma Membrane Structure

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

Transport Across the Plasma Membrane

• Passive Transport: No energy required; includes diffusion and facilitated diffusion.

• Active Transport: Requires energy (ATP); moves substances against concentration gradient.

• What can pass: Small, nonpolar molecules (e.g., O2, CO2).

• What cannot pass: Large, polar molecules and ions without transport proteins.

Isotonic Solutions

• Isotonic: Equal solute concentration inside and outside the cell; no net water movement.

• Cells retain their normal shape in isotonic solutions.

Glycolysis

Glycolysis is the first step in cellular respiration, breaking down glucose to produce ATP.

• Occurs in the cytoplasm.

• Produces pyruvate, ATP, and NADH.

Electron Transport Chain & ATP Production

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

• Electron carriers (NADH, FADH2) donate electrons to the chain.

Tissues & Organ Systems

Types of Tissues and Their Functions

• Epithelial Tissue: Covers surfaces, lines cavities, protects, absorbs, and secretes.

• Connective Tissue: Supports, binds, and protects organs.

• Muscle Tissue: Contracts to produce movement.

• Nervous Tissue: Transmits electrical impulses.

Types of Connective Tissues

• Loose Connective Tissue: Cushions organs.

• Dense Connective Tissue: Forms tendons and ligaments.

• Adipose Tissue: Stores fat.

• Cartilage: Flexible support.

• Bone: Rigid support.

• Blood: Transports substances.

Location of Tissue Types

• Epithelial: Skin, lining of digestive tract.

• Connective: Tendons, ligaments, fat, bone, blood.

• Muscle: Skeletal muscles, heart, stomach.

• Nervous: Brain, spinal cord, nerves.

Muscle Type in the Stomach

• Smooth Muscle: Involuntary, non-striated muscle found in the stomach and other internal organs.

Cell Junctions

• Tight Junctions: Seal cells together, prevent leakage.

• Desmosomes: Anchor cells, provide mechanical strength.

• Gap Junctions: Allow communication between cells.

Summary Table: Types of Tissues and Locations

Summary Table: Cell Junctions

Additional info: Academic context was added to expand brief points into full explanations, and tables were inferred for clarity.