Chapter 1: Introduction to Cell Biology

Transmission of Hereditary Information

Cell biology explores the fundamental units of life and the mechanisms by which hereditary information is transmitted across generations in plants and animals.

• Cell Theory: All organisms are made up of cells, and all cells arise from preexisting cells.

• Chromosome Theory of Inheritance: Genes are located on chromosomes, and inheritance patterns are determined by chromosome behavior during meiosis.

• Organism: Defined as a life form or "living entity" that is alive.

Characteristics Shared by All Organisms

All living organisms share several key characteristics that define life:

• Cell: Made of membrane-bound units (cells). The cell membrane regulates the passage of materials between exterior and interior.

• Replication: All living things replicate; replication is essential for the continuation of life.

• Information: Organisms process hereditary information (genetic information) and respond to environmental information to maintain stable internal conditions.

• Energy: Organisms acquire and use energy (e.g., plants use sunlight, animals need food).

• Evolution: Populations of organisms evolve over time.

Cell Structure and Function

Cells are the basic unit of life. All organisms are made of cells, and cells come from preexisting cells. Cells must replicate, which they do by splitting.

• Cell Membrane: Regulates passage of materials.

• DNA: Contains hereditary information.

• RNA: Carries out functions within the cell; molecular machinery reads out what to do in order for the cell to make protein (essential for cell existence).

Chromosomes and DNA

Chromosomes are molecules of DNA. DNA is a double-stranded helix made up of four different symbols: A, T, C, and G. These are called nucleotides.

• Strands: The strands are connected by base pairing: A always pairs with T, and G always pairs with C.

• DNA Codes: DNA codes for RNA, which in turn codes for proteins.

Example: The sequence of DNA bases determines the genetic information passed from one generation to the next.

Proteins and Cellular Function

Proteins are essential molecules that carry out most cellular functions. The cell machinery reads DNA to determine which proteins to make, which are necessary for cell survival.

• Protein Synthesis: DNA → RNA → Protein

Energy Acquisition in Cells

Cells require energy to function. Plants and some bacteria can create sugar using sunlight (photosynthesis) and use the sugar to make ATP or store it in energy-rich molecules. Animals, fungi, and archaea obtain energy by consuming or decomposing energy storage molecules.

• ATP: Adenosine triphosphate, the main energy currency of the cell.

Degna Definition: Flow of Genetic Information

The flow of genetic information is central to cell biology, describing how DNA is transcribed to RNA and translated to protein.

• Central Dogma:

Phylogenetic Trees and DNA Sequences

Phylogenetic trees are used to examine evolutionary relationships among organisms by comparing DNA sequences. Organisms with similar DNA sequences are more closely related.

• DNA Sequence Comparison: DNA sequences are composed of the letters T, A, G, C. Organisms with similar sequences are more closely related.

• Phylogenetic Tree: A diagram that shows evolutionary relationships based on genetic similarity.

Example: Taxa 5 and 6 share a more recent common ancestor and are more closely related than taxa 2 and 4.

Additional info: The notes have been expanded to include definitions, examples, and context for key cell biology concepts such as cell theory, chromosome theory, DNA structure, and phylogenetic trees. The central dogma of molecular biology is also included for completeness.