BIOS 110 Exam 1 Review: Foundations of Human Biology (Chapters 1-4)

Introduction to Biology

Domains of Life

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

• Bacteria: Prokaryotic, unicellular organisms lacking a nucleus.

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

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

Hierarchy of Living Organisms

Biological organization follows a hierarchical structure from smallest to largest.

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

Shared Characteristics of Living and Nonliving Things

• Living things: Composed of cells, capable of growth, reproduction, response to stimuli, metabolism, and homeostasis.

• Nonliving things: May have structure and mass but lack cellular organization and biological processes.

Scientific Method

The scientific method is a systematic approach to investigation.

• Observation

• Hypothesis

• Experiment

• Data Collection

• Analysis

• Conclusion

Homeostasis

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

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

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 function by analyzing individual organelles.

Importance of DNA

• DNA stores genetic information, directs protein synthesis, and enables inheritance.

Types of Chemical Bonds

• Ionic Bonds: Formed by transfer of electrons between atoms; creates charged ions.

• Covalent Bonds: Formed by sharing electrons between atoms.

• Hydrogen Bonds: Weak attractions between a hydrogen atom and an electronegative atom (e.g., oxygen or nitrogen).

Polarity of Molecules

• Polar molecules: Unequal sharing of electrons; have partial positive and negative charges (e.g., water).

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

Acids, Bases, and pH

• Acidic substances: pH < 7

• Basic substances: 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.

Atoms and Charge

• Atoms change charge by gaining or losing electrons, forming ions.

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

Element vs. Molecule

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

• Molecule: Two or more atoms bonded together.

Structure & Function of Cells

Cell Organelles: Names, Functions, and Shapes

Cell organelles perform specialized functions within eukaryotic cells.

• Nucleus: Stores DNA; spherical shape.

• Mitochondria: Site of ATP production; oval shape.

• Ribosomes: Protein synthesis; small, round particles.

• Endoplasmic Reticulum (ER): Synthesis of proteins (rough ER) and lipids (smooth ER); network of membranes.

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

• Lysosomes: Digestion of cellular waste; spherical vesicles.

• Chloroplasts: Photosynthesis (plants); oval shape.

• Plasma Membrane: Controls entry/exit of substances; flexible boundary.

Cell Size and Surface Area

Cell size is limited by the surface area-to-volume ratio, which affects nutrient and waste exchange.

• Smaller cells have higher surface area relative to volume, allowing efficient transport.

Microscopy Types

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

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

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

Diffusion

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

• Example: Oxygen diffusing across cell membranes.

Plasma Membrane Structure

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

Transport Across the Plasma Membrane

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

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

Active Transport

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

• Example: Sodium-potassium pump.

Isotonic Solutions

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

• Cells retain their shape in isotonic solutions.

Chemical Reactions & Cellular Metabolism

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 in Citric Acid Cycle

• NAD+ and FAD are electron carriers.

• They gain electrons from metabolic intermediates during the citric acid cycle.

Tissues & Organ Systems

Types of Tissues and Their Functions

• Epithelial Tissue: Covers surfaces, lines cavities, forms glands.

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

• Muscle Tissue: Contracts to produce movement.

• Nervous Tissue: Transmits electrical impulses.

Types of Connective Tissues

• Loose Connective Tissue: Provides support and flexibility.

• Dense Connective Tissue: Forms tendons and ligaments.

• Adipose Tissue: Stores fat.

• Cartilage: Provides cushioning in joints.

• Bone: Structural support.

• Blood: Transports nutrients and wastes.

Location of Tissue Types

• Epithelial: Skin, lining of digestive tract.

• Connective: Tendons, fat, bone, blood.

• Muscle: Skeletal muscles, heart, stomach.

• Nervous: Brain, spinal cord, nerves.

Muscle Type in the Stomach

• Smooth muscle is found in the stomach, enabling involuntary contractions for digestion.

Types of Junctions

• Tight Junctions: Seal cells together, preventing leakage.

• Desmosomes: Provide mechanical strength by anchoring cells.

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

Table: Types of Tissues and Their Functions

Type	Function	Location
Epithelial	Protection, absorption, secretion	Skin, lining of organs
Connective	Support, binding, transport	Bone, blood, tendons
Muscle	Movement	Skeletal muscles, heart, stomach
Nervous	Communication	Brain, nerves

Table: Types of Cell Junctions

Junction Type	Function
Tight Junction	Prevent passage of molecules between cells
Desmosome	Provide structural support
Gap Junction	Allow communication via ions and small molecules

Table: Types of Cell Organelles

Organelle	Function	Shape
Nucleus	Stores genetic material	Spherical
Mitochondria	Produces ATP	Oval
Ribosome	Protein synthesis	Small, round
ER	Protein/lipid synthesis	Network
Golgi	Protein modification	Stacked sacs
Lysosome	Digestion	Spherical

Additional info:

• ATP synthase is the main protein complex for ATP production during oxidative phosphorylation.

• Electron carriers NAD+ and FAD are reduced to NADH and FADH2 during the citric acid cycle.

• Radioisotopes are also used for dating fossils and tracing biochemical pathways.