GEN BIO

• Important People in Cell Theory

  • Zacharias Janssen - invented the microscope
  • Robert Hooke - first to observe the cell
  • Anton van Leeuwenhoek - father of microbiology; "animalcules"→ little animals
  • Matthias Schleiden - "plants are made up of cells"
  • Theodor Schwann - "animals are made up of cells"
  • Rudolf Virchow - "cells come from pre-existing cells"
• Postulates of the Cell Theory

  • All living things are made up of cells
  • Cells are the basic unit of structure and function in an organism
  • Cells come from pre-existing cells
  • Cells carry genetic material which is passed from cell to cell during cell division
  • All cells are basically the same in structure and chemical composition
  • Energy flow (biochemical processes) occurs within cells
• Cell Organelles and Functions

  • Cell membrane - regulates entry and exit of materials
  • Cell wall - rigid membrane made of cellulose in plants
  • Cytoplasm - liquid portion between nucleus and cell membrane
  • Nucleus - stores genetic material and controls cell activities
  • Nucleolus - site of ribosome synthesis
  • Ribosome - site of protein synthesis
  • Mitochondria - site of cellular respiration
  • Smooth ER - lipid and steroid production, calcium ion storage, detoxification
  • Rough ER - modifies proteins
  • Golgi body - sorts, tags, packages, and distributes lipids and proteins
  • Vesicles - transport or store a variety of compounds
  • Lysosome - contains enzymes that degrade molecules
  • Peroxisome - contains catalase or peroxidase to neutralize toxicity
  • Chloroplast - site of photosynthesis
  • Vacuole - maintains water balance, stores nutrients and waste
  • Cytoskeleton - provides shape and structure
  • Centrosome - microtubule organizing center essential for cell division
  • Cilia and Flagella - locomotory projections
• Differences between Prokaryotic and Eukaryotic Cells

  • DNA - circular vs linear
  • Nucleus - no nucleus vs membrane-bound
  • Chromosomes - one or multiple vs multiple linear
  • Organelles - absent vs present
  • Ribosomes - 70S vs 80S
  • Reproduction - binary fission vs sexual and mitosis
  • Cell wall - peptidoglycan vs cellulose or chitin
• Prokaryotes reproduce faster than eukaryotes due to their smaller size and less complexity
• Plant Tissues and Cells

  • Dermal Tissue - covers outer surface, epidermal cells, stoma
  • Ground Tissue - parenchyma, collenchyma, sclerenchyma
  • Vascular Tissue - xylem, phloem, cambium
• Animal Tissues and Cells

  • Epithelial Tissue - squamous, cuboidal, columnar
  • Connective Tissue - bones, loose connective, blood
  • Muscle Tissue - skeletal, smooth, cardiac
  • Nervous Tissue - neurons, glial cells
• Root Hairs


  Absorb nutrients and water from the soil
• Microvilli


  Absorb nutrients during digestion
• Flagella


  For movement, found in sperm cells
• Phases of Cell Cycle

  • G1 - cell growth
  • S - DNA synthesis
  • G2 - energy replenishment and more growth
  • G0 - resting phase
• Mitosis


  1. Prophase - nucleoli disappear, DNA condenses, nuclear membrane disintegrates

  2. Metaphase - chromosomes line up on equatorial plane

  3. Anaphase - daughter chromosomes move to opposite poles

  4. Telophase - chromosomes reach poles, nuclear membrane reforms
• Meiosis I


  1. Prophase I - crossing over

  2. Metaphase I - homologous pairs align

  3. Anaphase I - homologous pairs separate

  4. Telophase I - chromosomes reach poles, cytokinesis
• Meiosis II


  1. Prophase II - chromosomes condense, nuclear membrane disintegrates

  2. Metaphase II - chromosomes align on metaphase plate
• At the end of Mitosis, the cell has 46 chromosomes
• At the end of Meiosis I, the cell has 23 chromosomes
• At the end of Meiosis II, the cell has 23 chromosomes
• Meiosis


  • KARYOKINESIS → TWO: Meiosis I and Meiosis II
  • Meiosis I→ reductive division (2n=n)
  • Meiosis II→ equal division (n=n)
  • CYTOKINESIS → cellular division
  • Product: four HAPLOID cells
• • Given 46 (diploid number) chromosome for HUMANS, how many chromosomes are there at:
  • the end of Mitosis= 46
  • the end of Meiosis I = 23
  • the end of Meiosis II = 23
• MEIOSIS I (focuses on homologous pairs)

  1. Prophase I

  2. Metaphase I

  3. Anaphase I

  4. Telophase I
• MEIOSIS II (focuses on chromatids)

  1. Prophase II

  2. Metaphase II

  3. Anaphase II

  4. Telophase II

  5. Cytokinesis
• Significance of Mitosis and Meiosis

  • Mitosis: Regeneration and repair, Cell growth and development, Genetic stability, Asexual reproduction
  • Meiosis: Diversity, Production of gametes, Activation of the genetic code
• Mitosis vs Meiosis


  Mitosis separates chromatids; meiosis separates homologous pairs
• Cancer→ any malfunction in the checkpoint can lead to uncontrolled division
• p53 gene defect → damaged cell continues to divide and can lead to formation of tumor or cancer cells; unable to trigger apoptosis
• Turner Syndrome → mono-X syndrome (only one X in females), resulting in short stature and infertility
• Down Syndrome → trisomy 21, characterized by intellectual disability, distinctive facial features, and developmental delays
• Edward Syndrome → trisomy 18, results in severe developmental abnormalities and is associated with high rates of infant mortality
• Klinefelter Syndrome → in males (an extra X chromosome) XXY, may result in infertility, reduced testosterone levels, and developmental delays
• Jacob Syndrome → in males (an extra Y chromosome) XYY, may result in tall stature, developmental delays, and behavioral problems
• Cell membrane


  • Phospholipid bilayer
  • Hydrophilic head→ phosphate
  • Hydrophobic tail → lipids
  • Fluid-mosaic model
  • Semipermeable→ allows certain molecules and ions to pass through while excluding others
  • Contains proteins: peripheral protein and integral protein
• Peripheral protein


  Found on the surface of the cell membrane, play roles in cell signaling, cell-cell recognition, and cell adhesion
• Integral protein


  Embedded in the lipid bilayer, involved in transporting molecules across the membrane, acting as channels or carriers
• Passive Transport


  1. Simple Diffusion

  2. Osmosis

  3. Facilitated Diffusion
• Simple Diffusion


  Movement of small or lipophilic molecules through the membrane (driven by concentration gradient)
• Osmosis


  Movement of water molecules through the membrane (dependent on solute concentrations)
• Facilitated Diffusion


  A transport protein (channel protein, gated channel proteins, carrier protein) is required to move a large substance (ex: glucose) from outside of the cell to the inside of the cell
• Active Transport


  1. Protein Pumps (Primary Active Transport)

  2. Carrier Proteins (Secondary Active Transport)

  3. Bulk Transport
• Protein Pumps (Primary Active Transport)


  Directly uses a source of chemical energy (e.g., ATP) to move molecules across a membrane against their gradient
• Carrier Proteins (Secondary Active Transport)


  Uses an electrochemical gradient – generated by primary active transport – as an energy source to move molecules against their gradient, and thus does not directly require a chemical source of energy such as ATP