Biology Chapter on Cell Size and Division

Cell Size and Efficiency

• Larger cells are less efficient at moving materials across their membrane and place greater demands on their DNA.
• Surface area is calculated as length × width × 6 (SA).
• Volume is calculated as length × width × height (V).
• The ratio of surface area to volume (SA:V) is crucial for cellular function. A smaller SA:V ratio leads to inefficiencies.

Information and Traffic Problems

• Cell volume growth outpaces the increase in surface area.
• This creates difficulty in exchanging materials.
• This leads to an information crisis as the cell struggles to manage its internal processes.

Cell Division

• Cell division creates two daughter cells.
• DNA replication must precede cell division.
• Dividing into smaller cells maintains a high surface area to volume ratio, ensuring efficient material exchange.

Asexual Reproduction

• A single parent produces genetically identical offspring.
• Offspring can be produced rapidly in favorable conditions.
• In stable conditions, this method is highly effective.

Sexual Reproduction

• Involves the fusion of two parent cells.
• Offspring inherit genetic information from both parents.
• This provides genetic diversity.
• This is advantageous in changing environments.

Comparing Asexual and Sexual Reproduction

Chromosomes

• Genetic information is bundled into packages of DNA
• Prokaryotic cells have a single, circular chromosome.
• Eukaryotic cells have multiple thread-like chromosomes.
• Prokaryotic cells reproduce through binary fission.

Eukaryotic Cell Cycle

• Interphase is the period between cell divisions.
• Mitosis is the division of the nucleus.
• Cytokinesis is the division of the cell.
• G1 Phase: cell grows in size, produces new proteins, and synthesizes new organelles.
• S Phase: DNA replication occurs.
• G2 Phase: cell continues growing; makes necessary organelles and molecules for DNA replication.
• M Phase: cell division stage encompassing prophase, metaphase, anaphase, and telophase.

Mitosis

• Prophase: Chromosomes condense, spindle fibers form, and the nuclear membrane breaks down.
• Metaphase: Chromosomes line up along the middle of the cell.
• Anaphase: Sister chromatids separate and move to opposite poles of the cell.
• Telophase: Chromosomes decondense, spindle fibers break down, and nuclear membranes reform.

Meiosis

• A process that creates gametes (sex cells).
• Establish 4 gametes from one initial cell.
• Generates genetic diversity through crossing over and independent assortment.
• Oogenesis creates eggs; spermatogenesis creates sperm.
• Homologous pairs of chromosomes line up, undergo crossing over (exchanging segments), and separate in meiosis I and later the sister chromatids separate in meiosis II to create 4 unique haploid cells.

Regulating the Cell Cycle

• The cell cycle is controlled by internal and external regulators.
• There are specific proteins involved in this process, including cyclins which regulate mitosis.
• Internal regulators monitor internal conditions before advancing to the next phase, ensuring a smooth cycle.
• External regulators signal the cell to start or stop dividing in response to external factors such as wound healing.
• Apoptosis is a programmed cell death that is important for development and maintaining healthy tissues.

Cancer

• Cancer is caused by uncontrolled or unregulated cell growth.
• Cancer cells ignore normal regulatory signals.
• Cancer cells can form tumors.
• Benign tumors do not spread—malignant tumors can spread to other parts of the body.
• Carcinogens are substances known to cause cancer.

Cancer Treatments

• There are various treatments, such as surgery, radiation, chemotherapy, and immunotherapy.
• These methods aim to eliminate cancer cells by various means including targeting DNA, or by boosting the body's own immune system to fight the cancer cells.

Explore the concepts of cell size, efficiency, and division in this quiz. Learn how surface area to volume ratios affect cellular function and the implications of asexual reproduction. Test your knowledge on how cells manage their processes and the importance of maintaining efficient material exchange.