Cell Biology Module 3: Organelles and Cell Division

Organelles

• Membrane-bound structures within cells performing specific functions
• Includes mitochondria (energy production), endoplasmic reticulum (protein synthesis), and Golgi apparatus (protein processing)

Cell Division

• Essential for reproduction, growth, and repair
• Involves splitting a single cell into new cells, distributing genetic information from parent cells to daughter cells

The Cell Cycle

• Regular sequence of growth and division that eukaryotic cells undergo
• Divided into three main stages: Interphase, Mitosis, and Cytokinesis

Interphase

• Cell grows, makes a copy of its DNA, and prepares for division
• Consists of three parts: G1 (Growth Phase), S (DNA Copying Phase), and G2 (Preparation Phase)

Chromosomes and Chromatids

• Human somatic cells have 23 pairs of homologous chromosomes, one from each parent
• Chromatin (DNA and proteins) condenses into chromosomes during the S phase of interphase, forming an "X" shape
• Each chromosome consists of two identical sister chromatids attached by a centromere

Chromosome Structure

• Chromatin: Indistinguishable mass of DNA and proteins
• Chromatids: Identical parts of a chromosome attached by a centromere

Mitosis

• Results in two genetically identical daughter cells
• Divided into four stages: Prophase, Metaphase, Anaphase, and Telophase

Cytokinesis

• Division of the cytoplasm, resulting in two separate daughter cells with identical nuclei

Meiosis

• Process of cell division producing four gametes with half the number of chromosomes
• Consists of two rounds of division: Meiosis I and Meiosis II

Unique Features of Meiosis

• Synapsis: Homologous chromosomes pair along their length after replication
• Crossing Over: Exchange of genetic material between homologous chromosomes during synapsis, causing genetic variation
• Reduction Division: Chromosomes are not copied between divisions, resulting in haploid cells

Meiosis I

• Prophase I: Chromosomes become visible, homologous chromosomes pair, and crossing over occurs
• Metaphase I: Homologous chromosomes line up in the cell center
• Anaphase I: Spindle fibers shorten, separating homologous chromosomes (sister chromatids remain paired)
• Telophase I: Nuclear membrane reforms, resulting in two haploid cells, each with two sister chromatids

Meiosis II

• Prophase II: Nuclear membrane breaks down again
• Metaphase II: Chromosomes line up in the cell center
• Anaphase II: Spindle fibers shorten, and sister chromatids move to opposite poles
• Telophase II: Nuclear envelope reforms around daughter chromosomes

End of Meiosis II

• Results in four haploid cells, each with one copy of each chromosome (23 chromosomes in humans)

Key Terms

• Cell Cycle: Sequence of growth and division in eukaryotic cells
• Interphase: Phase of growth and DNA replication
• Mitosis: Division of genetic material into two daughter cells
• Cytokinesis: Division of the cytoplasm
• Meiosis: Division process producing gametes with half the chromosomes
• Synapsis: Pairing of homologous chromosomes
• Crossing Over: Exchange of genetic material between homologous chromosomes
• Reduction Division: Division resulting in haploid cells

Genetics

• Definition: Study of heredity and variation, investigating how genes and traits are passed from parents to offspring
• Genetic Information: Located in the cell nucleus, cells undergo division and reproduction, passing genes from parents to offspring

Gregor Mendel's Experiment

• Foundation: Mendel's experiments with garden pea plants established the basic rules of inheritance
• Reasons for Using Pea Plants: Small and easy to cultivate, short generation time, ability to self-fertilize and cross-pollinate, and seven distinct contrasting traits

Characteristics of Pea Plants

• Traits: Stem height, seed shape, seed color, flower color, pod shape, pod color, and flower position
• Dominant and recessive traits: Tall and short, round and wrinkled, yellow and green, purple and white, inflated and constricted, green and yellow, and axial and terminal

Mendel's Experiment Process

• Purebred Plants: Produced purebred plants (P1 generation) with specific traits
• Cross-pollination: Pollen from one plant fertilized the eggs of another plant
• F1 Generation: Resulting offspring from cross-pollination
• F2 Generation: Resulting offspring from self-pollination of F1 generation

Archaebacteria

• Found in extreme environments (hot boiling water, thermal vents, acidic conditions with no oxygen)
• Anaerobic, with unique DNA in their ribosomes
• Includes methanogens, thermophiles, and halophiles

Eubacteria

• Diverse in shape, chemical composition, nutritional requirements, and biochemical activities
• Important decomposers in the ecosystem, recycling nutrients

Scientific Nomenclature

• Rules for Scientific Names: Organisms are identified by their binomial name (genus and species), genus name is capitalized, and species name is not
• Importance of Scientific Names: Provides useful information about evolutionary history and relationships, acts as shorthand for describing plants or animals, and developed using Latin and Greek

Cells

• Basic unit of structure and function in living things
• In multicellular organisms, cells are often specialized, each uniquely suited to perform specific functions

Tissues

• Group of cells that perform a single function
• Four basic types of tissue in the human body: Epithelial, Connective, Nervous, and Muscle tissue

Organs

• Group of different types of tissues that work together to perform a single function
• Example: The eye is an organ composed of epithelial, nervous, muscle, and connective tissues, all working together to enable sight

Organ Systems

• Group of organs that perform closely related functions
• Eleven organ systems of the human body work together to maintain homeostasis

Nervous System

• Recognizes and coordinates the body's response to changes in internal and external environments
• Structures: Brain, Spinal cord, and Peripheral nerves
• Divisions: Central Nervous System (CNS) and Peripheral Nervous System (PNS)
• CNS: Acts as the control center of the body, relays, processes, and analyzes information
• Brain: Has approximately 100 billion neurons and weighs about 1.4 kilograms