Comprehensive Study Guide: Biomolecules, Cells, Bioenergetics, Cell Signaling, Cell Cycle, Genetics, and Protein Synthesis

Unit 1 – Biomolecules & Cells

Prokaryotic vs. Eukaryotic Cells

Cells are the fundamental units of life, classified as either prokaryotic or eukaryotic based on structural differences.

• Prokaryotic cells: Lack a nucleus and membrane-bound organelles; DNA is found in the nucleoid region (e.g., Escherichia coli).

• Eukaryotic cells: Possess a nucleus and various membrane-bound organelles (e.g., plants, animals, fungi, protists).

Key differences:

• Size: Eukaryotic cells are generally larger.

• Complexity: Eukaryotes have compartmentalized functions via organelles.

• Cell division: Prokaryotes divide by binary fission; eukaryotes by mitosis/meiosis.

Phospholipid Bilayers

Phospholipids form the basic structure of cell membranes, creating a selectively permeable barrier.

• Structure: Hydrophilic (polar) head and hydrophobic (nonpolar) tails.

• Bilayer formation: In aqueous environments, phospholipids arrange tails inward, heads outward.

• Function: Regulates entry/exit of substances, supports membrane proteins.

Transport mechanisms:

• Passive transport: Diffusion, facilitated diffusion, osmosis (no energy required).

• Active transport: Requires energy (ATP) to move substances against concentration gradients.

Example: Sodium-potassium pump actively transports Na+ and K+ ions across animal cell membranes.

Unit 2 – Bioenergetics & Cell Signaling

Energy Conversion in Cells

Cells convert energy from nutrients into usable forms (ATP) through metabolic pathways.

• Photosynthesis: Converts light energy into chemical energy (glucose) in chloroplasts of plants/algae.

• Cellular respiration: Breaks down glucose to produce ATP, CO2, and H2O in mitochondria.

ATP Cycle:

• ATP (adenosine triphosphate) stores energy in phosphate bonds.

• Hydrolysis of ATP releases energy for cellular work.

Enzymes: Biological catalysts that lower activation energy and increase reaction rates.

Cell Signaling

Cells communicate via chemical signals to coordinate activities.

• Signal transduction: Process by which a cell converts an external signal into a functional response.

• Receptors: Proteins that bind signaling molecules (ligands) and initiate cellular responses.

• Second messengers: Small molecules (e.g., cAMP, Ca2+) that amplify signals inside the cell.

Example: Insulin signaling regulates glucose uptake in animal cells.

Unit 3 – Cell Cycle & Genetics

Cell Cycle

The cell cycle is the series of events that cells go through as they grow and divide.

• Phases: G1 (growth), S (DNA synthesis), G2 (preparation for division), M (mitosis/cytokinesis).

• Checkpoints: Ensure proper division and DNA integrity.

Mitosis: Produces two genetically identical daughter cells for growth and repair.

Meiosis: Produces four genetically unique gametes for sexual reproduction.

Genetics

Genetics is the study of heredity and variation in organisms.

• Genes: Units of heredity made of DNA, located on chromosomes.

• Alleles: Different forms of a gene.

• Genotype: Genetic makeup; Phenotype: Observable traits.

Example: Mendel’s laws of segregation and independent assortment explain inheritance patterns.

Unit 4 – Making Proteins

Transcription and Translation

Protein synthesis involves two main processes: transcription (DNA to RNA) and translation (RNA to protein).

• Transcription: RNA polymerase synthesizes mRNA from a DNA template in the nucleus (eukaryotes) or cytoplasm (prokaryotes).

• Translation: Ribosomes read mRNA and assemble amino acids into polypeptides.

Key terms:

• Gene: DNA sequence coding for a functional product (protein or RNA).

• Promoter: DNA region where RNA polymerase binds to initiate transcription.

• Exons/Introns: Exons code for proteins; introns are non-coding regions (spliced out in eukaryotes).

• Codon: Three-nucleotide sequence on mRNA specifying an amino acid.

Directionality: mRNA is synthesized 5' to 3'; translation proceeds from the start codon (AUG) to a stop codon.

Example: The lac operon in E. coli demonstrates gene regulation in prokaryotes.

Overarching Questions for Critical Thinking

• How do chemical properties of biomolecules and the environment of early Earth facilitate the formation of a cell?

• What are the similarities and differences between prokaryotic and eukaryotic cells?

• How do enzymes lower activation energy and why is this important for metabolism?

• How is energy transformed from ATP hydrolysis to cellular work?

• How do mutations in DNA affect protein structure and function?

• How do cells regulate gene expression in response to environmental changes?

Additional info: Students should be able to draw and label diagrams of cells, membranes, and the processes of transcription and translation, and explain the significance of checkpoints in the cell cycle and the flow of genetic information from DNA to RNA to protein.