General Biology: Key Concepts and Practice Questions

Biological Classification and Phylogeny

Understanding Phylogenetic Trees

Phylogenetic trees are diagrams that represent evolutionary relationships among organisms. They are essential tools for visualizing how species are related through common ancestry.

• Phylogeny: The evolutionary history and relationship among individuals or groups of organisms.

• Clade: A group of organisms that includes an ancestor and all its descendants.

• Node: Represents a common ancestor in a phylogenetic tree.

• Root: The most ancestral branch in the tree.

• Outgroup: A species or group that is closely related to but not part of the group being studied; used as a reference point.

Example: In a tree showing mammals, birds, and reptiles, the node where mammals and birds diverge represents their last common ancestor.

Macromolecules: Structure and Function

Proteins, Carbohydrates, and Nucleic Acids

Macromolecules are large, complex molecules essential for life. The main classes include proteins, carbohydrates, nucleic acids, and lipids.

• Proteins: Polymers of amino acids linked by peptide bonds. Functions include catalysis (enzymes), structure, transport, and signaling.

• Carbohydrates: Sugars and their polymers. Serve as energy sources and structural components.

• Nucleic Acids: DNA and RNA, polymers of nucleotides, store and transmit genetic information.

Example: The enzyme amylase breaks down starch (a carbohydrate) into glucose monomers.

Chemical Bonds and Water Properties

Covalent, Ionic, and Hydrogen Bonds

Chemical bonds are forces that hold atoms together in molecules. Water's unique properties are due to its polar covalent bonds and ability to form hydrogen bonds.

• Covalent Bond: Atoms share electrons (e.g., H2O).

• Ionic Bond: Transfer of electrons from one atom to another (e.g., NaCl).

• Hydrogen Bond: Weak attraction between a hydrogen atom and an electronegative atom (e.g., between water molecules).

Properties of Water:

• High specific heat

• Cohesion and adhesion

• Excellent solvent for polar and charged substances

Example: Water's high heat capacity helps regulate temperature in living organisms.

Cell Structure and Function

Prokaryotic vs. Eukaryotic Cells

Cells are the basic units of life. They are classified as prokaryotic or eukaryotic based on structural differences.

• Prokaryotic Cells: Lack a nucleus; DNA is in the nucleoid region. Example: Bacteria and Archaea.

• Eukaryotic Cells: Have a nucleus and membrane-bound organelles. Example: Plants, Animals, Fungi, Protists.

Key Organelles:

• Nucleus: Contains genetic material.

• Mitochondria: Site of cellular respiration.

• Chloroplasts: Site of photosynthesis (plants and algae).

• Ribosomes: Protein synthesis.

Genetics: DNA, RNA, and Protein Synthesis

Central Dogma of Molecular Biology

The central dogma describes the flow of genetic information in cells: DNA → RNA → Protein.

• Transcription: DNA is used as a template to synthesize RNA.

• Translation: RNA is used to build proteins at the ribosome.

Example: The gene for hemoglobin is transcribed into mRNA, which is then translated into the hemoglobin protein.

Biological Molecules: Functional Groups

Recognizing Functional Groups

Functional groups are specific groups of atoms within molecules that have characteristic properties and chemical reactivity.

• Hydroxyl (-OH): Found in alcohols and carbohydrates.

• Carboxyl (-COOH): Found in amino acids and fatty acids.

• Amino (-NH2): Found in amino acids.

• Phosphate (-PO4): Found in nucleic acids and ATP.

Example: The carboxyl group in amino acids gives them acidic properties.

Table: Comparison of Cell Types

Feature	Prokaryotic Cell	Eukaryotic Cell
Nucleus	No	Yes
Membrane-bound Organelles	No	Yes
Size	Small (1-10 μm)	Larger (10-100 μm)
Examples	Bacteria, Archaea	Plants, Animals, Fungi, Protists

Additional info:

• Some diagrams and chemical structures were referenced in the questions, such as phylogenetic trees and molecular structures. These are commonly used in biology exams to test understanding of evolutionary relationships and molecular identification.

• Short answer and multiple-choice formats are typical for biology assessments, covering a range of foundational topics.