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General Biology: Lessons 1-3 Overview

General Biology and Hierarchy of Life

  • Hierarchy of life (from simple to complex): Atoms → Molecules → Macromolecules → Organelles → Cells → Tissues → Organs → Organ Systems → Organism → Population → Community → Ecosystem → Biome → Biosphere

  • Subsystems of the Earth (components of the biosphere):

    • Hydrosphere — Water

    • Lithosphere — Land

    • Atmosphere — Air

    • Triosphere — Ice

    • Geosphere — Rocks and minerals

  • Biome example: Philippines is composed of tropical climates

  • Biosphere is the worldwide sum of all ecosystems (ecosystem plus interactions with the biosphere)

  • Earth is the only astronomical object known to harbor life

  • Properties of Life (7 core properties):

    • Order: highly organized, coordinated structures that consist of one or more cells

    • Reproduction: Sexual and Asexual

    • Stimuli response: organisms respond to diverse stimuli

    • Growth: organisms grow and develop following specific instructions coded for by their genes

    • Regulation: multiple regulatory mechanisms coordinate internal functions, respond to stimuli, cope with environmental stresses

    • Energy processing: all organisms use a source of energy for activities

    • Homeostasis: maintenance of appropriate conditions such as temperature, pH, and chemical concentrations

  • Adenosine Triphosphate (ATP) is the energy currency, produced by the mitochondria

  • Glycosidic bonds are involved in linking sugars (as in carbohydrates)

  • Deoxyribonucleic acid (DNA) is the hereditary material

  • The History of the Cell Theory (key figures and contributions):

    • Robert Hooke (1665): English physicist; discovered cells using cork; Hooke proposed the term cell from monks living in cells; Hooke is associated with elastic behavior (Hooke's Law) as well as cell discovery

    • Matthias Jakob Schleiden (1838): German botanist; concluded that all plant tissues are composed of cells; statement: the cell is the basic building block of all plant matter

    • Theodor Schwann (1839): concluded that all animal tissues are composed of cells; statement: all tissues are made up of cells

    • Rudolf Virchow: cells arise from pre-existing cells; new cells arise from existing cells in both diseased and healthy tissues

    • Antonie van Leeuwenhoek: observed animalcules and bacteria; father of microbiology

    • The Postulates of the Cell Theory (summary):
      1) All living organisms are made of cells
      2) Cells are the basic units of life
      3) Cells arise from pre-existing cells
      4) Hereditary information is passed from cells to cells
      5) All cells have the basic chemical composition
      6) Energy flow occurs within cells

    • Basic cell chemical composition: Carbon, Hydrogen, Oxygen, Nitrogen, Phosphorus, Potassium (K), & Sulfur

  • Chemical formulas to recall:

    • Typical carbohydrate composition:

    • Glucose: C{6}H{12}O_{6}

  • The cell theory and biology build on foundational principles that connect grand biological hierarchies to cellular processes

Cells and Organelles (Lesson 2)

  • Cell: the smallest, basic unit of life responsible for all life processes

  • Discovery of cells: Hooke and Leeuwenhoek

    • Hooke: father of biology; coined cell term from cork observations

    • Leeuwenhoek: father of microbiology; observed animalcules (bacteria)

  • Cell characteristics and organization:

    • Cells provide structure and support; interior is organized into organelles surrounded by a membrane

    • The nucleus is a major organelle containing genetic information needed for reproduction and cell growth

  • Types of cells:

    • Prokaryotes: no nucleus

    • Eukaryotes: true nucleus present

  • Prokaryotic cells

    • Size: roughly 0.1$-$5.0 \, \mu m

    • Unicellular

    • DNA is circular and typically single haploid chromosome (n)

    • No membrane-bound organelles

    • Reproduction by binary fission; may reproduce sexually and asexually in some contexts

    • Examples: bacteria and archaea

  • Eukaryotic cells

    • Size: roughly 10$-$100 \, \mu m

    • Multicellular (often)

    • Nucleus present; linear DNA; paired diploid chromosomes (2n)

    • Membrane-bound organelles

    • Mostly reproduce sexually; cell division by mitosis

    • Examples: plant and animal cells, including humans

  • Similarities between prokaryotes and eukaryotes:

    • Both have a cell (plasma) membrane, cytoplasm, and ribosomes; DNA present in some form in both

  • Structure and function of key cell components:

    • Cell membrane: supports and protects; controls movement of substances; separates cell from external environment; present in all cells

    • Cell wall: present only in plant cells; protects plasma membrane and other components; made of cellulose; outermost layer in plant cells

    • Major parts listed: nucleus, cell wall, mitochondria, cytoplasm

  • Cytoplasm: a thick, clear, jelly-like substance inside the cell membrane; cytoskeleton components include microtubules and microfilaments; maintains organelle placement; all cells have cytoplasm

  • Nucleus: contains hereditary material (DNA); brain of the cell; all cells have genetic material

  • Nucleolus: inside the nucleus; ribosome synthesis

  • Nucleopor es: nuclear pores; gateway for ribosomes

  • Ribosomes: sites of protein synthesis; some are free in cytoplasm, others attached to rough endoplasmic reticulum (RER)

  • Haploid vs Diploid:

    • Haploid: n (prokaryotic-like chromosome number in some contexts)

    • Diploid: 2n (eukaryotic; paired chromosomes)

  • Binary fission: division method for many prokaryotes

  • Archaea: unicellular; often in extreme environments with high sulfur/heat

  • Niche: how an organism survives in its environment

  • Phospholipid bilayer: membrane structure that protects hydrophobic tails; forms the cell membrane

  • Intracellular vs Extracellular space

  • Simple chemical references:

    • Glucose formula: C{6}H{12}O_{6}

  • Lipids: fats and oils; hydrophobic vs hydrophilic properties

  • Bacteria: peptidoglycan in cell wall; some bacteria have thick lipopolysaccharides; concept of superbugs and antibiotic resistance due to thick cell walls

  • Apoptosis: programmed cell suicide

  • Lysosomes: digestive enzymes; recycle energy by digesting damaged organelles

  • The cell membrane and pH in the stomach: stomach pH ~ pH=2

  • Nitrogenous bases in DNA: Adenine, Thymine, Guanine, Cytosine

  • Chromosomes:

    • In humans: 23 pairs, total 46 chromosomes

    • 22 autosomes; 1 sex chromosome

    • Male karyotype: XY; Female karyotype: XX

  • Hermaphrodite concept in the transcription: XXY example; note mentions a phrase about transgender transformation

  • Reticulum and Golgi apparatus

    • Reticulum (endoplasmic reticulum): rough ER has ribosomes; smooth ER lacks ribosomes and is involved in lipid synthesis

    • Golgi body: sorting center; involved in transportation of materials within the cell

  • Mitochondria: powerhouse of the cell; ATP production

  • Chloroplasts: site of photosynthesis; present in photosynthetic cells; chlorophyll pigment

  • Vacuoles: storage; central vacuole in plants stores water

  • Egg cell: largest cell in the human body; Sperm cell: smallest cell; flagellated

  • Plasmids: bacterial DNA elements

Lesson 3: Cell Types and Stem Cells

  • Stem cells are precursor blank cells from which all cells derive

    • Pluripotency: capacity to give rise to all cell types in the body except the placenta

    • Unipotency: capacity to give rise to only one cell type

    • Embryonic stem cells: primitive undifferentiated cells

  • Cell structures and functions (reference of organelle roles):

    • Nucleolus: ribosome synthesis

    • Nuclear membrane: boundary of nucleus

    • Chromosomes: contain genetic material

    • Ribosomes: protein synthesis; rough ER ribosomes for secreted/membrane proteins

    • Smooth Endoplasmic Reticulum: lipid synthesis

    • Rough Endoplasmic Reticulum: protein synthesis; ribosomes attached

    • Golgi Body: processing and transport of cellular materials

    • Mitochondria: powerhouse

    • Lysosomes: degradation and recycling

    • Chloroplast: photosynthesis

    • Vacuoles: storage

Cell Types, Stem Cells, and Blood/Immune System (Expansion from Lesson 3)

  • Plasticity: ability to differentiate into multiple cell types

  • Hematopoietic stem cells: give rise to all blood cells (RBCs, WBCs, immune cells)

  • Mesenchymal stem cells: bone marrow stromal cells that can grow into bone, cartilage, fat, and connective tissues

  • Skin stem cells: basal layer of epidermis; give rise to keratinocytes

  • Neutral stem cells: brain cells like neurons/nerve cells; non-neuronal cells include astrocytes and oligodendrocytes

  • Epithelial stem cells (in digestive system): absorptive cells (glober), enteroendocrine cells

  • Erythrocytes (RBCs):

    • Biconcave disc; transport oxygen via hemoglobin

  • Leukocytes (WBCs):

    • About 1% of blood; group together against pathogens; rely on dendritic cells for signaling

    • Types of leukocytes:

    • Neutrophils: most common ~65% of WBC; size ~12–14 μm; single nucleus; circulate 6–10 hours before entering tissue; undergo apoptosis after activation

    • Eosinophils: rare in blood; contain toxins; destroy parasites; assist in deworming; participate in inflammation

    • Basophils: rare; defense against parasites; ~14–16 μm; release histamine, serotonin, prostaglandins to promote inflammation

    • Lymphocytes: include B cells and T cells; roles in immune response

      • Helper T cells: activate B cells and antibodies

      • Killer T cells: kill pathogens

      • Virgin T cells: not yet developed

      • Messenger: undergo training

  • Dendritic cells: antigen-presenting cells that communicate with leukocytes

  • Monocytes: ~20 μm; differentiate into macrophages; large phagocytic cells; kidney bean shape; engulf and kill pathogens

  • Phagocytosis: engulfing pathogens

  • Hemophilia: factor deficiency leading to impaired blood clotting

  • Thrombocytes (platelets): cell fragments important in clotting; live ~8–10 days; produce fibrin to stop bleeding

  • Neuroglial cells (glia): not involved in conduction; helpers in the nervous system

    • Astrocytes: provide nutrients and support

    • Oligodendrocytes: form myelin sheath

    • Ependymal cells: remove debris from injury sites; maintain CSF

    • Microglia: immune defense in CNS

  • Neurons: basic brain cells that transmit information via electrical signals; do not divide readily after injury

  • Muscle cells:

    • Skeletal muscle cells: voluntary movement; attached to bones; show striations

    • Cardiac muscle cells (cardiomyocytes): heart muscle; involuntary; continuous beating

    • Smooth muscle cells: involuntary; arranged in sheets; found in digestive tract; aids digestion; stomach acid (pH ~2) is a key example of harsh internal conditions

  • Cartilage types and locations:

    • Hyaline cartilage: present in joints; various joint types (pivot, gliding, ball and socket, hinge, saddle, condyloid) and role in movement

    • Elastic cartilage: found in larynx, ears, epiglottis

    • Fibrocartilage: found in knee joints and between vertebrae

  • Bone cells:

    • Osteoclasts: break down bone during renewal and healing

    • Osteoblasts: synthesize organic matrix for bone formation

    • Osteocytes: sense mechanical strain and secrete growth factors to promote bone growth

    • Lining cells: line bone surfaces and regulate calcium release into the bloodstream

    • Approximately 206 bones in an adult human; >300 bones in an infant

  • Skin cells and components:

    • Keratinocytes: produce keratin; protect against toxins and pathogens; help retain heat and moisture

    • Melanocytes: produce melanin to protect against UV; skin color variation linked to number and activity of melanocytes

    • Merkel cells: associated with nerve endings; involved in touch reception

    • Langerhans cells: antigen-presenting cells in the skin; work with leukocytes in immune response

    • Endothelial cells: line blood vessels; flat in structure; thickness ~1–2 μm; present in arteries, veins, capillaries

    • Epithelial cells: line cavities such as lungs, intestines, stomach; form thin protective layers

  • Important numeric and factual references:

    • Human chromosomes: 46 total; 23 pairs; 22 autosomes + 1 sex chromosome

    • Male karyotype: XY; Female karyotype: XX

    • Stomach pH example: around pH 2

    • Glucose formula: C{6}H{12}O_{6}

    • 206 bones in an adult; 300+ bones in an infant

  • Miscellaneous terms encountered in the notes:

    • Plasmid: circular DNA molecule in bacteria

    • The term Hermaphrodite appeared in the notes with an XXY example, including a colloquial phrase; this is included here as part of the provided transcript

Summary of Key Concepts and Connections

  • The hierarchy of life provides a framework to understand how complex biological systems emerge from simple components, from atoms to biosphere and beyond

  • The cell theory unifies biology by stating that cells are the basic units of life that arise from pre-existing cells and that heredity information is passed through generations via cells

  • Prokaryotic and eukaryotic cells differ in nucleus presence, size, organization, and complexity, yet share core features like a cell membrane, cytoplasm, and ribosomes

  • Organelles perform specialized functions essential for cell survival, energy production, and biosynthesis; mitochondria and chloroplasts are energy-related organelles (ATP production and photosynthesis, respectively)

  • Stem cells provide the foundation for growth, development, and tissue repair; their potency (pluripotent vs unipotent) determines their differentiation potential

  • Blood and immune system cells illustrate how stem cells give rise to diverse lineages, each with specific roles in defense, oxygen transport, and wound healing

  • The extracellular and intracellular milieus, including pH, ion balance, and nutrient availability, shape cell function and tissue health

  • Anatomical structures like cartilage, bone, muscle, and skin demonstrate tissue specialization and how different cell types work together to support movement, protection, and homeostasis

Formulas and Key Figures to Remember

  • Carbohydrate formula: C{6}H{12}O_{6}

  • Chromosome count in humans: 23 \times 2 = 46 (total chromosomes)

  • Stomach acidity example: pH \approx 2

  • Typical cell size ranges:

    • Prokaryotes: 0.1\;\mu m \text{ to } 5.0\;\mu m

    • Eukaryotes: 10\;\mu m \text{ to } 100\;\mu m

  • Number of bones in an adult: 206

  • Description of cell colors and pigments (melanin, chlorophyll) not quantified numerically, but key for function is noted

Quick Reference: Major Terms

  • Atoms, Molecules, Macromolecules, Organelles, Cells, Tissues, Organs, Organ Systems, Organism, Population, Community, Ecosystem, Biome, Biosphere

  • Prokaryote vs Eukaryote: nucleus presence, size, complexity, and cell division method

  • Organelles: nucleus, nucleolus, ribosomes, endoplasmic reticulum (smooth and rough), Golgi apparatus, mitochondria, chloroplasts, lysosomes, vacuoles, cytoskeleton, cell membrane, cell wall (plants only), and more

  • Blood/immune cells: erythrocytes, leukocytes (neutrophils, eosinophils, basophils, lymphocytes), dendritic cells, monocytes/macrophages, thrombocytes

  • Connective and supportive tissues: cartilage (hyaline, elastic, fibrocartilage), bone cells (osteoclasts, osteoblasts, osteocytes, lining cells)

  • Skin layers and cells: keratinocytes, melanocytes, Merkel cells, Langerhans cells, endothelial cells, epithelial cells

  • Stem cell potency: pluripotent vs unipotent; embryonic stem cells

  • Notable historical figures: Hooke, Leeuwenhoek, Schleiden, Schwann, Virchow, and postulates of cell theory

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