General Biology I: Study Guide for Exam 1 (Chapters 1–4)

Chapter 1: Introduction to Biology

Properties of Living Organisms

Living organisms share several fundamental properties that distinguish them from non-living matter.

• Cellular Organization: All living things are composed of one or more cells.

• Metabolism: Organisms carry out chemical reactions to obtain and use energy.

• Homeostasis: The ability to maintain a stable internal environment.

• Growth and Development: Organisms increase in size and undergo development.

• Reproduction: The ability to produce new individuals.

• Response to Stimuli: Organisms can respond to environmental changes.

• Evolutionary Adaptation: Populations evolve over time through changes in genetic composition.

Hierarchy of Biological Organization

Biological systems are organized from the smallest to the most complex levels:

• Atoms → Molecules → Organelles → Cells → Tissues → Organs → Organ Systems → Organisms → Populations → Communities → Ecosystems → Biosphere

Populations, Communities, and Ecosystems

• Population: A group of individuals of the same species living in a specific area.

• Community: All the populations of different species living and interacting in an area.

• Ecosystem: A community plus the non-living (abiotic) environment.

Scientific Experiments: Variables and Controls

• Positive Control: A group where a known response is expected.

• Negative Control: A group where no response is expected.

• Independent Variable: The factor that is changed or manipulated.

• Dependent Variable: The factor that is measured or observed.

Energy Flow in Ecosystems

Energy enters ecosystems as sunlight, is converted by producers (plants) into chemical energy, and flows through food chains. Energy is lost as heat at each trophic level.

Scientific Method

The scientific method is a systematic approach to inquiry:

1. Observation

2. Question

3. Hypothesis

4. Experiment

5. Conclusion

Hypothesis

• A hypothesis is a testable, falsifiable statement that explains an observation.

Chapter 2: Chemistry of Life

Chemical Reactions and Atoms

• Reactants: Substances that start a chemical reaction.

• Products: Substances formed as a result of a chemical reaction.

• Nucleus: The central part of an atom containing protons and neutrons.

• Atomic Number: Number of protons in an atom.

• Atomic Mass: Sum of protons and neutrons.

Subatomic Particles

• Proton: Charge +1, mass 1 amu.

• Neutron: Charge 0, mass 1 amu.

• Electron: Charge -1, mass ~0 amu.

Isotopes

• Atoms of the same element with different numbers of neutrons.

• Some isotopes are stable; others are radioactive.

Electron Shells and Chemical Bonds

• Electron Shells: Electrons occupy energy levels around the nucleus.

• Covalent Bond: Atoms share electrons.

• Ionic Bond: Atoms transfer electrons, resulting in oppositely charged ions.

Polar and Non-Polar Covalent Bonds

• Polar Covalent Bond: Electrons are shared unequally, creating partial charges (e.g., in water).

• Non-Polar Covalent Bond: Electrons are shared equally.

Valence Electrons and Stability

• Atoms are stable when their outermost shell is full (octet rule).

• Valence electrons determine chemical reactivity.

Water and Van der Waals Interactions

• Van der Waals Interactions: Weak attractions between molecules due to temporary partial charges.

• Trace Elements: Elements required in very small amounts (e.g., iron, iodine).

Chapter 3: Water and Its Properties

Structure and Polarity of Water

• Water is composed of two hydrogen atoms and one oxygen atom (H2O).

• Oxygen is more electronegative, making water a polar molecule.

Cohesion, Adhesion, and Surface Tension

• Cohesion: Water molecules stick to each other via hydrogen bonds.

• Adhesion: Water molecules stick to other substances.

• Surface Tension: The result of cohesion at the surface of water.

Hydrogen Bonds

• Hydrogen bonds form between the slightly positive hydrogen of one water molecule and the slightly negative oxygen of another.

Evaporation and Temperature Regulation

• When water evaporates, it absorbs heat, cooling the surface (evaporative cooling).

• Hydrogen bonds must be broken for water to evaporate, requiring energy.

pH and Buffers

• pH: Measures the concentration of hydrogen ions ($[H^+]$) in a solution.

• pH is calculated as $pH = -\log_{10}[H^+]$.

• Each pH unit represents a tenfold difference in $[H^+]$ concentration.

• Example: pH 5.0 has 100 times more $[H^+]$ than pH 7.0.

• Buffers: Substances that minimize changes in pH by accepting or donating H+ ions.

Acidification and Water Quality

• Acidification lowers water pH, threatening aquatic life and water quality.

Chapter 4: Organic Chemistry and Biological Molecules

Organic Compounds and Carbon

• Organic chemistry studies carbon-containing compounds.

• Carbon is versatile due to its four valence electrons, allowing it to form four covalent bonds.

Isomers

• Isomers: Compounds with the same molecular formula but different structures.

• Types include structural isomers, cis-trans isomers, and enantiomers.

Functional Groups

• Groups of atoms attached to carbon skeletons that give molecules specific properties.

• Common functional groups include:

  • Hydroxyl (–OH): Alcohols

  • Carboxyl (–COOH): Carboxylic acids

  • Amino (–NH2): Amines

  • Phosphate (–PO4): Organic phosphates

  • Methyl (–CH3): Methylated compounds

Properties from Functional Groups

• The presence and arrangement of functional groups determine the chemical behavior of organic molecules.

• For example, the hydroxyl group makes molecules more soluble in water.

Functional Group	Structure	Example	Properties
Hydroxyl	–OH	Ethanol	Polar, forms hydrogen bonds
Carboxyl	–COOH	Acetic acid	Acidic, donates H+
Amino	–NH2	Glycine	Basic, accepts H+
Phosphate	–PO4	ATP	Contributes negative charge
Methyl	–CH3	Methylated DNA	Nonpolar, affects gene expression