Introduction to Human Biology

This study guide covers foundational topics in human biology, focusing on the chemistry of life, cell structure and function, and the organization of tissues. Understanding these concepts is essential for further study in biological sciences and medicine.

Domains of Life

Classification of Life

• Three Domains: All living organisms are classified into three domains: Bacteria, Archaea, and Eukarya.

• Bacteria and Archaea: Prokaryotic cells lacking a nucleus.

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

Hierarchy of Living Organisms

Levels of Biological Organization

• Atoms → Molecules → Organelles → Cells → Tissues → Organs → Organ Systems → Organism

• This hierarchy reflects increasing complexity from chemical to organismal level.

Chemistry of Living Things

Most Abundant Elements in Humans

• Oxygen (O), Carbon (C), Hydrogen (H), Nitrogen (N) are the most abundant elements in the human body.

Atoms, Elements, and Molecules

• Element: A pure substance consisting of one type of atom (e.g., Oxygen).

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

Types of Chemical Bonds

• Ionic Bonds: Formed when electrons are transferred from one atom to another, creating charged ions.

• Covalent Bonds: Atoms share electrons to achieve stability.

• Hydrogen Bonds: Weak attractions between a hydrogen atom and an electronegative atom (e.g., in water).

Polarity of Molecules

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

• Nonpolar Molecules: Electrons are shared equally; no charge separation (e.g., O2).

Acids, Bases, and pH

• pH Scale: Measures hydrogen ion concentration.

• Acidic: pH < 7

• Basic (Alkaline): pH > 7

• Neutral: pH = 7

Radioisotope Technology

• Radioisotopes: Unstable isotopes that emit radiation; used in medical imaging and cancer treatment.

Reductionism

• Reductionism: The approach of studying complex systems by breaking them down into simpler components.

Cell Structure and Function

Cell Organelles: Names, Functions, and Shapes

• Nucleus: Contains genetic material (DNA); controls cell activities.

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

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

• Golgi Apparatus: Modifies, sorts, and packages proteins and lipids.

• Lysosomes: Contain digestive enzymes; break down waste.

• Ribosomes: Sites of protein synthesis; can be free or attached to ER.

• Plasma Membrane: Phospholipid bilayer; controls entry and exit of substances.

• Cytoskeleton: Provides structural support; involved in cell movement.

Cell Size and Surface Area

• As cell size increases, volume increases faster than surface area.

• This limits cell size due to the need for efficient exchange of materials.

• Surface Area to Volume Ratio: Higher ratio allows more efficient transport.

Microscopy Types

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

• Electron Microscopy: Provides higher resolution; used for detailed cell structures.

DNA Importance

• DNA: Carries genetic information; directs protein synthesis and inheritance.

How Atoms Change Charge

• Atoms gain electrons to become negatively charged (anions).

• Atoms lose electrons to become positively charged (cations).

Cell Membrane and Transport

Plasma Membrane Structure

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

• Contains 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., water).

• Cannot Pass Easily: Large molecules, ions, and charged particles.

Diffusion

• Movement of molecules from high to low concentration.

• Does not require energy (passive transport).

Active Transport

• Movement of substances against their concentration gradient.

• Requires energy (usually ATP).

Isotonic Solutions

• Isotonic Solution: Solute concentration is equal inside and outside the cell.

• No net movement of water; cell maintains its shape.

Cellular Respiration

Glycolysis

• First step in cellular respiration; occurs in the cytoplasm.

• Breaks down glucose into pyruvate, producing ATP and NADH.

Citric Acid Cycle (Krebs Cycle)

• Occurs in mitochondria; completes the breakdown of glucose.

• Electron carriers NADH and FADH2 are produced by transferring electrons from metabolic intermediates.

Electron Transport Chain (ETC)

• Located in the inner mitochondrial membrane.

• Most ATP is produced by the protein complex ATP synthase during oxidative phosphorylation.

Scientific Method and Homeostasis

Scientific Method Steps

1. Observation

2. Question

3. Hypothesis

4. Experiment

5. Data Collection

6. Conclusion

Homeostasis

• Maintenance of a stable internal environment despite external changes.

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

Living vs. Nonliving Things

Shared Characteristics

• Living things exhibit organization, metabolism, responsiveness, growth, reproduction, and adaptation.

• Nonliving things do not exhibit all these characteristics.

Tissues and Their Organization

Types of Tissues

• Epithelial Tissue: Covers body surfaces and lines cavities; functions in protection, absorption, and secretion.

• Connective Tissue: Supports and binds other tissues; includes bone, blood, cartilage, adipose tissue.

• Muscle Tissue: Responsible for movement; types include skeletal, cardiac, and smooth muscle.

• Nervous Tissue: Conducts electrical impulses; found in brain, spinal cord, nerves.

Types of Connective Tissue and Locations

• Loose Connective Tissue: Underlies skin, surrounds organs.

• Dense Connective Tissue: Tendons and ligaments.

• Cartilage: Joints, ear, nose.

• Bone: Skeleton.

• Blood: Circulatory system.

• Adipose Tissue: Fat storage under skin, around organs.

Muscle in the Stomach

• Smooth Muscle: Found in the walls of the stomach and other hollow organs; involuntary control.

Types of Cell Junctions

• Tight Junctions: Seal cells together to prevent leakage.

• Desmosomes: Anchor cells together, providing mechanical strength.

• Gap Junctions: Allow communication between adjacent cells.

Summary Table: Types of Tissues and Functions

Additional info:

• Some explanations and examples were expanded for clarity and completeness.

• Table entries and some tissue locations were inferred based on standard human biology knowledge.