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.

• Order: Organisms exhibit complex but ordered organization.

• Regulation: Ability to maintain stable internal conditions (homeostasis).

• Growth and Development: Organisms grow and develop according to specific instructions coded in their DNA.

• Energy Processing: Use of energy to power activities and chemical reactions.

• Response to Environment: Ability to respond to environmental stimuli.

• Reproduction: Ability to produce new organisms.

• Evolutionary Adaptation: Populations evolve over generations through adaptations.

Hierarchy of Biological Organization

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

• Atom → Molecule → Organelle → Cell → Tissue → Organ → Organ System → Organism → Population → Community → Ecosystem → Biosphere

Populations, Communities, and Ecosystems

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

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

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

Experimental Design

• Positive Control: Group where a known response is expected.

• Negative Control: 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 webs. 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 or answers a scientific question.

Chapter 2: Chemistry of Life

Chemical Reactions and Atomic Structure

• Reactants: Substances that start a chemical reaction.

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

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

• Atomic Number: Number of protons in an atom.

• Atomic Mass: Sum of protons and neutrons.

Calculating Subatomic Particles

• Number of Protons: Equal to atomic number.

• Number of Neutrons: Atomic mass minus atomic number.

• Number of Electrons: Equal to number of protons in a neutral atom.

Subatomic Particles: Weights and Charges

• Proton: Mass ≈ 1 amu, Charge = +1

• Neutron: Mass ≈ 1 amu, Charge = 0

• Electron: Mass ≈ 0 amu, Charge = -1

Isotopes and Ions

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

• Ions: Atoms or molecules with a net electric charge due to loss or gain of electrons.

Chemical Bonds

• Covalent Bond: Sharing of electron pairs between atoms.

• Ionic Bond: Transfer of electrons from one atom to another, resulting in oppositely charged ions.

Polarity and Bond Types

• Polar Covalent Bond: Electrons are shared unequally, resulting in partial charges.

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

Element Stability and Valence

• Elements with full outer electron shells are stable and non-reactive (noble gases).

• Valence electrons determine chemical reactivity.

Major Elements in Living Organisms

• Major elements: Carbon (C), Hydrogen (H), Oxygen (O), Nitrogen (N)

• Trace elements: Required in small amounts (e.g., iron, iodine, zinc)

Chapter 3: Water and Life

Structure and Properties of Water

• Water Molecule: Composed of two hydrogen atoms and one oxygen atom (H2O).

• Polarity: Water is a polar molecule due to the difference in electronegativity between oxygen and hydrogen.

• Cohesion: Water molecules stick together via hydrogen bonds.

• Surface Tension: Caused by cohesive forces at the surface of water.

• Hydrogen Bonds: Weak bonds between the slightly positive hydrogen atom of one water molecule and the slightly negative oxygen atom of another.

Evaporation and Temperature Regulation

• When water evaporates, the surface cools (evaporative cooling).

• Hydrogen bonds must be broken for water to evaporate, requiring energy (heat of vaporization).

pH and Buffers

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

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

• Each unit change in pH represents a tenfold change in [H+].

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

• Acidification: Decrease in pH, which can threaten water quality and aquatic life.

pH Value	[H+] Concentration
5.0	$1 \times 10^{-5}$ M
7.0	$1 \times 10^{-7}$ M
Difference	pH 5.0 is 100 times more acidic than pH 7.0

Chapter 4: Organic Chemistry and Biological Molecules

Organic Compounds and Carbon

• Organic Chemistry: Study of carbon-containing compounds.

• Versatility of Carbon: Carbon can form four covalent bonds, allowing for diverse molecular structures.

Isomers

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

• Types of Isomers:

  • Structural Isomers: Differ in covalent arrangement of atoms.

  • Cis-trans Isomers: Differ in spatial arrangement around double bonds.

  • Enantiomers: Mirror images of each other.

Functional Groups

• Functional Groups: Specific groups of atoms attached to carbon skeletons that determine the properties of organic molecules.

Functional Group	Structure	Example
Hydroxyl	-OH	Alcohols (e.g., ethanol)
Carboxyl	-COOH	Carboxylic acids (e.g., acetic acid)
Amino	-NH2	Amines (e.g., glycine)
Phosphate	-PO4	Organic phosphates (e.g., ATP)
Methyl	-CH3	Methylated compounds

• Attachment of different functional groups changes the chemical properties and reactivity of organic molecules.