Human Biology Exam 1 Study Guide: Chapters 1-4

Domain of Life and Hierarchy of Living Organisms

Domains of Life

The three domains of life classify all living organisms based on cellular organization and genetics.

• Bacteria: Single-celled prokaryotes without a nucleus.

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

• Eukarya: Organisms with eukaryotic cells (with a nucleus), including 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 → Population → Community → Ecosystem → Biosphere

Example: Muscle cell → Muscle tissue → Heart (organ) → Circulatory system → Human (organism)

Chemistry of Living Things

Most Abundant Elements in Humans

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

Atoms, Elements, and 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 from one atom to another, forming charged ions.

• Covalent Bonds: Sharing of electrons between atoms.

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

Polarity

• Polar Molecules: Unequal sharing of electrons, resulting in partial charges (e.g., H2O).

• Nonpolar Molecules: Equal sharing of electrons, no charge separation (e.g., O2).

pH Scale

• Acidic: pH < 7

• Neutral: pH = 7

• Basic (Alkaline): pH > 7

Radioisotope Technology

• Used in medical imaging, cancer treatment, and biological research.

Atoms and Charge

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

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

Reductionism

• Studying complex systems by analyzing their simpler components.

DNA Importance

• DNA stores genetic information essential for inheritance, coding for proteins, and guiding cell functions.

Scientific Method

1. Observation

2. Question

3. Hypothesis

4. Experiment

5. Analysis

6. Conclusion

Homeostasis

• Maintenance of a stable internal environment despite external changes.

Living vs. Nonliving Characteristics

• Living things: Organization, metabolism, responsiveness, growth, reproduction, adaptation.

• Nonliving things lack one or more of these characteristics.

Structure and Function of Cells

Cell Organelles: Names, Functions, and Shapes

Organelle	Function	Shape/Structure
Nucleus	Stores DNA, controls cell activities	Large, spherical
Mitochondria	ATP production (cellular respiration)	Oval, double membrane
Ribosome	Protein synthesis	Small, spherical
Endoplasmic Reticulum (Rough)	Protein modification, transport	Flattened sacs with ribosomes
Endoplasmic Reticulum (Smooth)	Lipid synthesis, detoxification	Tubular, no ribosomes
Golgi Apparatus	Sorting and packaging of proteins	Stacked, flattened sacs
Lysosome	Digestion of macromolecules	Small, spherical vesicles
Plasma Membrane	Controls entry/exit of substances	Flexible, phospholipid bilayer
Cytoskeleton	Cell shape, movement	Network of fibers

Cell Size and Surface Area

• Smaller cells have a higher surface area-to-volume ratio, allowing efficient exchange of materials.

Microscopy Types

Type	Use
Light Microscope	Viewing live cells, general structure
Transmission Electron Microscope (TEM)	Internal cell structures, high resolution
Scanning Electron Microscope (SEM)	Surface details, 3D images

Cell Membrane and Transport

Plasma Membrane Structure

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

What Can and Can't Pass Through the Plasma Membrane

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

• Ions and large polar molecules require transport proteins.

Diffusion

• Movement of molecules from high to low concentration.

Active Transport

• Movement of substances against their concentration gradient, requiring energy (ATP).

Isotonic Solution

• Solute concentration is equal inside and outside the cell; no net water movement; cell shape remains unchanged.

Cellular Respiration and Energy

Glycolysis

• First step in cellular respiration; breaks down glucose into pyruvate, producing ATP and NADH.

Electron Transport Chain (ETC)

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

Electron Carriers in the Citric Acid Cycle

• NAD+ and FAD collect electrons from metabolic reactions to deliver to the ETC.

From Cells to Organ Systems

Types of Tissues and Their Functions

Tissue Type	Function	Location Example
Epithelial	Protection, absorption, secretion	Skin, lining of gut
Connective	Support, binding, transport	Bone, blood, fat
Muscle	Movement	Skeletal muscles, heart, stomach
Nervous	Communication, control	Brain, nerves

Types of Connective Tissue

• Loose connective tissue, dense connective tissue, cartilage, bone, blood, adipose tissue.

Muscle Type in the Stomach

• Smooth muscle is found in the stomach wall, responsible for involuntary contractions.

Types of Cell Junctions

• Tight Junctions: Seal cells together, prevent leakage.

• Desmosomes: Anchor cells together, provide mechanical strength.

• Gap Junctions: Allow communication between cells via small channels.

Where to Find Each Tissue Type

• Epithelial: Skin, lining of digestive tract

• Connective: Tendons, ligaments, bone, blood

• Muscle: Skeletal muscles, heart (cardiac), stomach (smooth)

• Nervous: Brain, spinal cord, nerves

Additional info: This guide covers foundational concepts from the first four chapters of a Human Biology course, including cell structure, chemistry, and tissue organization. For diagrams and further examples, refer to your textbook or lecture slides.