General Biology: Cells, Atoms, Water, and Organic Molecules

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Introduction to Biology

Overview of Biology and Related Sciences

Biology is the scientific study of life, encompassing the structure, function, growth, origin, evolution, and distribution of living organisms. It is closely related to other sciences such as anthropology (the study of human societies and cultures), and geology (the study of Earth's physical structure and processes).

Anthropology: Study of human societies, cultures, and their development.
Geology: Study of Earth's structure, substances, history, and processes.

Cells: The Basic Unit of Life

Types of Cells

Eukaryotic Cells: Cells with a nucleus and membrane-bound organelles. Found in plants, animals, fungi, and protists.
Prokaryotic Cells: Cells lacking a nucleus and membrane-bound organelles. Typically unicellular, including bacteria and archaea.

Unicellular vs. Multicellular Organisms

Unicellular Organisms: Consist of a single cell performing all necessary life functions.
Multicellular Organisms: Composed of multiple cells that differentiate and specialize to perform various functions.
Main Difference: Unicellular organisms consist of one cell; multicellular organisms consist of many cells.

Cellular Organization and Microscopy

Microscopic Organisms: Unicellular organisms are usually only visible with a microscope due to their small size.
Humans: Consist of trillions of cells.
Smallest Fundamental Unit of Life: The cell.

Key Biological Terms

Organism: Any individual form of life.
Root 'uni': Means one.
Root 'multi': Means many or multiple.
Root 'bio': Means life.
Root 'ology': Means study of.

Characteristics of Life

Organization and Homeostasis

Organization: Living organisms use smaller structures to build larger, more complex structures.
Homeostasis: The ability of living organisms to stabilize or maintain suitable living conditions.
Example: Sweating to cool the body in hot environments.

Reproduction and Genetic Material

Types of Reproduction: Sexual (two parents) and asexual (one parent).
Genetic Material: DNA serves as the genetic material in all living organisms.

Evolution and Response to Stimuli

Evolution: Changes in the DNA of a population over time, leading to adaptation and improved survival.
Response to Stimuli: The ability of living organisms to respond to environmental changes (e.g., a plant growing towards sunlight).

Viruses and Life

Viruses: Not considered alive because they lack characteristics such as the ability to reproduce on their own.

Atoms and Elements

Structure of Atoms

Atom: The smallest unit of an element that retains the properties of that element.
Subatomic Particles:
- Proton: Positive charge (+1), located in the nucleus.
- Neutron: Neutral charge (0), located in the nucleus.
- Electron: Negative charge (-1), orbits the nucleus.
Atomic Number: Number of protons in the nucleus.
Mass Number: Total number of protons and neutrons.
Atomic Mass Unit (AMU): Unit of mass for atomic and molecular weights.

Electron Shells and Valence Electrons

Electron Shells: Energy levels where electrons orbit the nucleus.
First Energy Shell: Maximum of 2 electrons.
Second Energy Shell: Maximum of 8 electrons.
Valence Electrons: Electrons in the outermost shell, involved in chemical bonding.
Octet Rule: Atoms are more stable when their valence shells are full, typically with 8 electrons.

Chemical Elements and Trace Elements

Chemical Element: Pure substance made up of only one type of atom.
Trace Elements: Required for life but only in small amounts.
CHNOPS: Mnemonic for Carbon, Hydrogen, Nitrogen, Oxygen, Phosphorus, Sulfur (key elements in living organisms).

Properties of Water

Structure and Polarity

Water Molecule: Polar molecule due to unequal sharing of electrons between oxygen and hydrogen atoms.
Hydrogen Bonds: Weak bonds between the hydrogen atom of one water molecule and the oxygen atom of another.

Unique Properties of Water

Cohesion: Water molecules stick to each other via hydrogen bonds.
Adhesion: Water molecules stick to other substances.
Surface Tension: Resistance of water's surface to being broken, caused by cohesion.
Capillarity (Capillary Action): Movement of water within narrow spaces, facilitated by cohesion and adhesion.
High Specific Heat: Water can absorb a lot of heat before changing temperature.

Biological Importance of Water's Properties

Transport in Plants: Capillary action and adhesion allow water to move upward from roots to leaves.
Surface Tension: Enables small objects or organisms to rest on water's surface.
Adhesion: Helps water move through plant vessels and stick to biological surfaces.

Summary Table: Properties of Water

Property	Description	Biological Significance
Cohesion	Attraction between water molecules	Enables surface tension, water transport in plants
Adhesion	Attraction between water and other substances	Helps water move through plant vessels
Surface Tension	Resistance of water's surface to breaking	Allows small objects to rest on water
Capillarity	Movement of water in narrow spaces	Essential for water transport in plants
High Specific Heat	Absorbs heat with little temperature change	Stabilizes temperatures in organisms/environments

Organic Molecules and Carbon Chemistry

Organic Molecules

Definition: Molecules containing covalently linked carbon and hydrogen atoms.
Hydrocarbons: Organic molecules made up solely of carbon and hydrogen.
Major Classes: Carbohydrates, proteins, nucleic acids, and lipids.

Carbon: The Building Block of Life

Abundance: Most abundant element in living systems (excluding water).
Bonding: Can form four covalent bonds, allowing for diverse structures.
Backbone Variation: Carbon backbones can vary in length, position of double bonds, branching, and ring formations.

Comparison Table: Organic Molecules vs. Hydrocarbons

Type	Composition	Example
Organic Molecules	Carbon, hydrogen, and other elements (e.g., O, N, P, S)	Glucose, DNA
Hydrocarbons	Only carbon and hydrogen	Methane, ethane

Key Terms and Concepts

Element Symbol: One- or two-letter abbreviation for a chemical element.
Atomic Mass: Average mass of all isotopes of an element.
Matter: Anything that takes up space and has mass.

Formulas and Equations

Atomic Number:
Mass Number:

Examples and Applications

Capillary Action in Plants: Water moves upward from roots to leaves due to cohesion and adhesion.
Surface Tension: Water strider insects can walk on water due to high surface tension.
Organic Molecules: Glucose (C6H12O6) is a carbohydrate essential for energy in cells.