Biology 105 Study Guide: Foundations of Life, Cells, Chemistry, Immunity, and Respiration

Humans in the World of Biology

Basic Characteristics of Living Things

All living organisms share several fundamental characteristics that distinguish them from non-living matter. These features are essential for life and are observed across all domains of biology.

• Contain nucleic acids, proteins, carbohydrates, and lipids: These biomolecules are universal to all living things. DNA (deoxyribonucleic acid) is especially important for heredity and reproduction.

• Composed of cells: Cells are the smallest units of life. Organisms may be unicellular (one cell) or multicellular (many cells).

• Grow and reproduce: Reproduction can be asexual (one parent) or sexual (two parents combining genetic material).

• Use energy and raw materials: Metabolism refers to all chemical reactions in cells, enabling growth and maintenance.

• Respond to their environment: Sensory organs and nervous systems detect and respond to stimuli.

• Maintain homeostasis: Internal conditions are regulated within certain limits for stability.

• Adapt and evolve: Populations acquire adaptive traits through natural selection, leading to evolution.

Evolution and Biological Classification

Domains and Kingdoms of Life

Biological classification organizes life into three domains and several kingdoms, reflecting evolutionary relationships and cellular structure.

• Domain Bacteria: Unicellular prokaryotes, lack a nucleus.

• Domain Archaea: Unicellular prokaryotes, often live in extreme environments.

• Domain Eukarya: Eukaryotic cells with a membrane-bound nucleus and internal compartments. Includes four kingdoms: Protists, Fungi, Plants, Animals.

Humans belong to the Animal kingdom, specifically the vertebrates and mammals, and are classified as primates.

Levels of Biological Organization

Hierarchy of Life

Life is organized from the smallest to the largest levels, each with increasing complexity.

• Population: Group of the same species in one area.

• Community: All species living and interacting in one area.

• Ecosystem: Community plus non-living environment (water, soil, air).

• Biosphere: All ecosystems on Earth.

The Scientific Method

Steps in Scientific Investigation

The scientific method is a systematic approach to answering questions about the natural world, ensuring reliable and reproducible results.

1. Observation

2. Form a question

3. Hypothesis (possible explanation)

4. Prediction

5. Experiment (controlled setup)

6. Results

7. Conclusion

Variables: Independent (changed/tested), dependent (measured), and confounding (extra, confusing results). Control: Standard for comparison.

Reasoning: Inductive (generalize from observations), Deductive (predict from general rule).

Chemistry Comes to Life

The Nature of Atoms

Atoms are the fundamental units of matter, composed of subatomic particles:

• Protons: Positive charge, in nucleus.

• Neutrons: Neutral, in nucleus.

• Electrons: Negative charge, orbit nucleus in shells.

Atomic number: Number of protons. Atomic mass: Protons + neutrons. Isotopes: Same element, different neutrons.

Chemical Bonds and Compounds

Atoms combine via chemical bonds to form molecules and compounds. The main types of bonds are:

Type	Basis for Attraction	Strength	Example
Covalent	Sharing of electrons	Strongest	CH4 (methane)
Ionic	Transfer of electrons, attraction of oppositely charged ions	Strong	NaCl (table salt)
Hydrogen	Attraction between hydrogen and electronegative atom	Weak	Between water molecules

The Cell

Prokaryotic vs. Eukaryotic Cells

Cells are classified as prokaryotic or eukaryotic based on their structure and complexity.

Feature	Prokaryotic Cells	Eukaryotic Cells
Organisms	Bacteria, archaea	Plants, animals, fungi, protists
Size	1–10 μm	10–100 μm
Membrane-bound organelles	Absent	Present
DNA form	Circular	Linear strands
DNA location	Cytoplasm	Nucleus
Internal membranes	Rare	Many
Cytoskeleton	Present	Present

Cell Size and Surface-to-Volume Ratio

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

Measurement	Small Cell	Large Cell
Surface area	6	216
Volume	1	216
Surface-to-volume ratio	6:1	1:1

Additional info: Smaller cells are more efficient at exchanging materials due to higher surface-to-volume ratios.

Movement Across the Plasma Membrane

Cells use various mechanisms to transport substances across the plasma membrane:

Mechanism	Description
Simple diffusion	Random movement from high to low concentration
Facilitated diffusion	Movement via carrier protein
Osmosis	Movement of water across membrane
Active transport	Movement against concentration gradient, requires energy
Endocytosis	Engulfing materials into cell
Exocytosis	Expelling materials from cell

Cell Organelles and Their Functions

Eukaryotic cells contain specialized organelles, each with distinct functions:

Organelle	Function
Nucleus	Contains genetic information, influences cell function
Rough ER	Protein synthesis, produces membrane
Smooth ER	Detoxifies drugs, produces membrane
Golgi complex	Sorts, modifies, packages products
Lysosomes	Digest waste and old cell parts
Mitochondria	Produce energy (ATP) via cellular respiration

Body Defense Mechanisms: Immunity

Active vs. Passive Immunity

The immune system protects the body through two main types of immunity:

Active Immunity	Passive Immunity
Memory cells produced	No memory cells
Antibodies made by own white blood cells	Antibodies from outside the body
Results from infection or vaccination	Provided by injection, breast milk, or placenta

Self vs. Nonself: MHC Markers and Antigens

The immune system distinguishes self from nonself using molecular markers:

• MHC (Major Histocompatibility Complex) markers: Label cells as "self" to prevent immune attack.

• Antigens: Foreign molecules (often on pathogens) recognized as "foe" by the immune system.

Immunological Memory: Primary and Secondary Response

Immunological memory allows the body to respond more rapidly and effectively to repeated exposures to the same antigen.

• Primary response: Slow, occurs after first exposure.

• Secondary response: Faster and stronger, due to memory cells.

The Respiratory System

Structure and Function of the Larynx and Epiglottis

The larynx is a key structure in the respiratory system, responsible for voice production and preventing food from entering the airway. The epiglottis covers the larynx during swallowing.

• Larynx: Air passageway, voice production.

• Epiglottis: Prevents food/drink from entering the trachea during swallowing.

Additional info: Failure of the epiglottis mechanism can result in coughing or choking.