Foundations of General Biology: Organization, Chemistry, and Biological Molecules

Review of Unifying Themes in Biology

Main Themes

Biology is the study of living organisms and their interactions with each other and their environments. Several unifying themes help organize biological knowledge:

• Organization: Biological systems are structured in a hierarchical manner, from molecules to the biosphere.

• Information: Genetic information is stored in DNA and governs the functioning of all living things.

• Energy & Matter: Life requires the transfer and transformation of energy and matter.

• Interactions: Organisms interact with each other and their environment.

• Evolution: Evolution explains the unity and diversity of life.

Biological Organization

Levels of Organization (Smallest to Largest)

• Molecule

• Organelle

• Cell

• Tissue

• Organ

• Organism

• Population

• Community

• Ecosystem

• Biosphere

Each level builds upon the previous, increasing in complexity and integration.

Experiments in Biology

Experimental Design

• Control Group: The group in an experiment that does not receive the experimental treatment and is used as a benchmark.

• Experimental Group: The group that receives the treatment or variable being tested.

• Variables: Factors that can change in an experiment. Independent variables are manipulated, while dependent variables are measured.

Example: Testing plant growth under different light conditions. The control group receives normal light, while the experimental group receives altered light. Plant growth is measured as the dependent variable.

Chemistry for Biology

Atomic Structure

• Protons: Positively charged particles in the nucleus (atomic number = number of protons).

• Neutrons: Neutral particles in the nucleus.

• Electrons: Negatively charged particles orbiting the nucleus.

• Valence Electrons: Electrons in the outermost shell, important for chemical bonding.

Example: Oxygen (O): 8 protons, 8 neutrons, 8 electrons. Electron configuration: 2 in the first shell, 6 in the second shell.

Chemical Bonds

• Covalent Bonds: Atoms share electrons (strongest type of bond in biological molecules).

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

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

Properties of Water

Unique Properties

• Cohesion & Adhesion: Water molecules stick to each other (cohesion) and to other substances (adhesion).

• High Specific Heat: Water can absorb a lot of heat before changing temperature.

• Versatile Solvent: Many substances dissolve in water due to its polarity.

• Expansion Upon Freezing: Ice is less dense than liquid water, so it floats.

Acids and Bases

pH Scale and Ion Concentration

• Acids: pH less than 7; release hydrogen ions (H+).

• Bases: pH greater than 7; release hydroxide ions (OH-).

• Each pH unit represents a tenfold difference in H+ concentration.

Example: A solution of pH 9 is 100 times more basic than a solution of pH 7.

Carbon and Biological Molecules

Properties of Carbon

• Has 4 valence electrons, allowing it to form 4 strong covalent bonds.

• Can bond with many elements, including C (carbon), H (hydrogen), O (oxygen), N (nitrogen), P (phosphorus), and S (sulfur).

Large Biological Molecules

• Lipids: Nonpolar molecules used for energy storage and membrane structure.

• Carbohydrates: Sugars and starches used for energy and structural support. Glucose is a common monosaccharide.

• Proteins: Polymers of amino acids with diverse functions, including enzymes and structural roles.

• Nucleic Acids: DNA and RNA, which store and transmit genetic information.

Universal Genetic Code

DNA and Heredity

• All living organisms use DNA as their genetic material.

• The genetic code is nearly universal, allowing for the transfer of genetic information across species.

Cell Transport Mechanisms

Types of Transport

• Passive Transport: Movement of substances across membranes without energy input.

  • Simple Diffusion: Movement from high to low concentration.

  • Osmosis: Diffusion of water across a selectively permeable membrane.

  • Facilitated Diffusion: Movement via transport proteins, still down the concentration gradient.

• Active Transport: Movement of substances against their concentration gradient, requiring energy (often ATP).

Example: Sodium-potassium pump in animal cells moves Na+ out and K+ in, against their gradients.

Summary Table: Levels of Biological Organization

Level	Description
Molecule	Group of atoms bonded together
Organelle	Specialized structure within a cell
Cell	Basic unit of life
Tissue	Group of similar cells performing a function
Organ	Structure composed of multiple tissues
Organism	Individual living entity
Population	Group of organisms of the same species
Community	All populations in a given area
Ecosystem	Community plus the physical environment
Biosphere	All ecosystems on Earth

Key Equations and Concepts

• pH Calculation:

$\text{pH} = -\log_{10}[\text{H}^+]$

• Atomic Structure:

$\text{Atomic Number} = \text{Number of Protons}$ $\text{Mass Number} = \text{Number of Protons} + \text{Number of Neutrons}$

• Diffusion:

$\text{Net Movement} = \text{High Concentration} \rightarrow \text{Low Concentration}$

Additional info:

• Some context and examples were inferred to provide a complete, self-contained study guide.

• Scientific names and terms were italicized where appropriate.