BIO 101 — General Biology I: Lecture Note

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BIO la-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS

BIO la-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS Course code: BIO 101 Course title: General Biology I Course credit load: 2 Units Series 1: Cell Structure and Organization • Part 1.1: The Cell as the Unit of Life o Sub Part 1.1.1: Cell theory and discovery o Sub Part 1.1.2: Levels of biological organisation o Sub Part 1.1.3: Cell size and shape • Part 1.2: Prokaryotic and Eukaryotic Cells o Sub Part 1.2.1: Prokaryotic cell structure o Sub Part 1.2.2: Eukaryotic cell structure o Sub Part 1.2.3: Comparing prokaryotic and eukaryotic cells • Part 1.3: Plant and Animal Cell Differences o Sub Part 1.3.1: Distinctive plant cell features o Sub Part 1.3.2: Distinctive animal cell features o Sub Part 1.3.3: Shared cellular features • Part 1.4: The Cell Membrane and Transport o Sub Part 1.4.1: Membrane structure o Sub Part 1.4.2: Passive transport mechanisms o Sub Part 1.4.3: Active transport mechanisms

BIO la-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS Introduction All living things are built from cells, the smallest units capable of carrying out the basic processes of life. Understanding cell structure provides the foundation for nearly every other topic in biology, from how organisms grow and reproduce to how they obtain energy and respond to their environment. This opening Series introduces the cell as the basic unit of life and the levels of biological organisation; the structural differences between prokaryotic and eukaryotic cells; the distinguishing features of plant and animal cells; and the structure of the cell membrane together with the mechanisms by which substances cross it. This foundation supports the organelle function, classification, and reproduction topics covered later in this course. Series Learning Outcomes Upon completing this Series, you should be able to: • SLO 1.1 explain cell theory and the levels of biological organisation (Linked to Part 1.1), • SLO 1.2 distinguish prokaryotic and eukaryotic cell structure (Linked to Part 1.2), • SLO 1.3 distinguish plant and animal cell features (Linked to Part 1.3), and • SLO 1.4 describe the cell membrane structure and transport mechanisms (Linked to Part 1.4). 1.1 The Cell as the Unit of Life 1.1.1 Cell theory and discovery The cell theory states that all living organisms are composed of one or more cells, the cell is the basic structural and functional unit of life, and new cells arise from the division of existing cells; this theory, developed gradually through the work of several scientists using improving microscope technology, remains a foundational, unifying principle across all of biology.

BIO la-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS Robert Hooke first observed and named cells in cork tissue in 1665, while later microscopists, including Anton van Leeuwenhoek, observed living cells directly; the formal cell theory was articulated more fully in the nineteenth century, establishing that the cell, rather than any larger or smaller unit, is the fundamental building block shared by every living organism, from single-celled bacteria to large multicellular plants and animals. Fill in the blank: The cell theory states that all living organisms are composed of cells, the cell is the basic structural and functional unit of life, and new cells arise from the division of ________ cells. 1.1.2 Levels of biological organisation Living systems are organised hierarchically: atoms combine into molecules, molecules combine into organelles (specialised structures within a cell), organelles combine into cells, and, in multicellular organisms, cells combine into tissues (groups of similar cells performing a shared function), tissues into organs, organs into organ systems, and organ systems into a complete organism. Beyond the individual organism, biological organisation extends further: populations (groups of the same species in a given area), communities (multiple species populations interacting in an area), ecosystems, and ultimately the biosphere represent successively broader levels, with each level displaying properties (emergent properties) not present at the level below it, a concept relevant throughout this course. Fill in the blank: Each level of biological organisation displays ________ properties not present at the level below it, such as a tissue function not predictable from any single cell alone. 1.1.3 Cell size and shape Most cells are microscopic, generally ranging from about 1 to 100 micrometres in diameter, far too small to see with the unaided eye; this small size is not incidental but functionally important, since it keeps the ratio of cell surface area to cell volume relatively high, supporting efficient exchange of nutrients, gases, and waste products across the cell membrane.

BIO la-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS Cell shape varies considerably and often relates closely to cell function: red blood cells are flattened discs supporting efficient gas exchange, nerve cells have long, thin extensions supporting signal transmission over distance, and many plant cells are roughly rectangular, reflecting the supportive role of the surrounding rigid cell wall; this form-function relationship recurs throughout the study of cell biology. Fill in the blank: Small cell size keeps the ratio of cell surface area to cell ________ relatively high, supporting efficient exchange of nutrients, gases, and waste. Figure 1.1: Cell theory and biological organisation Pilot questions 1.1 1. State the three components of cell theory. 2. Name the scientist who first observed and named cells. 3. List the levels of biological organisation from atom to organism. 4. Define emergent property. 5. Explain why small cell size supports efficient exchange of materials.

BIO la-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS 1.2 Prokaryotic and Eukaryotic Cells 1.2.1 Prokaryotic cell structure Prokaryotic cells (found in bacteria and archaea) lack a membrane-bound nucleus and most membrane-bound organelles, instead containing their genetic material as a single, circular DNA molecule located in a region called the nucleoid, along with ribosomes (the cellular structures responsible for protein synthesis) suspended directly in the cytoplasm. Prokaryotic cells are generally smaller and structurally simpler than eukaryotic cells, typically enclosed by both a cell membrane and, in most bacteria, a rigid cell wall providing structural support and protection; despite this structural simplicity, prokaryotic cells carry out the essential life processes of metabolism, growth, and reproduction successfully across an enormous diversity of environments. Fill in the blank: Prokaryotic cells lack a membrane-bound nucleus, instead containing their genetic material in a region called the ________ . 1.2.2 Eukaryotic cell structure Eukaryotic cells (found in plants, animals, fungi, and protists) contain a membrane-bound nucleus enclosing the genetic material, along with numerous other membrane-bound organelles (mitochondria, endoplasmic reticulum, Golgi apparatus, and others, examined individually in detail in this course) that compartmentalise different cellular functions within distinct internal spaces. This internal compartmentalisation allows eukaryotic cells to carry out multiple specialised chemical processes simultaneously within separate organelles without these processes interfering with one another, supporting the greater structural and functional complexity generally associated with eukaryotic cells compared to prokaryotic cells, and underlying the capacity of eukaryotic cells to form the complex multicellular organisms (plants, animals, fungi) that make up much of visible life.

BIO la-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS Fill in the blank: Eukaryotic cells contain a membrane-bound ________ enclosing the genetic material, distinguishing them from prokaryotic cells. 1.2.3 Comparing prokaryotic and eukaryotic cells Prokaryotic cells are generally smaller (typically 1 to 10 micrometres) than eukaryotic cells (typically 10 to 100 micrometres), reflect simpler internal organisation lacking membrane-bound organelles, and possess a single circular DNA molecule, while eukaryotic cells are larger, internally compartmentalised by membrane-bound organelles, and possess DNA organised into multiple linear chromosomes contained within the nucleus. Despite these substantial structural differences, both cell types share certain fundamental features: a surrounding cell membrane regulating what enters and exits the cell, cytoplasm (the gel-like internal cell contents), ribosomes for protein synthesis, and DNA carrying hereditary information, underscoring that the cell theory basic principles apply across both major cell types despite their considerable structural divergence. Fill in the blank: Both prokaryotic and eukaryotic cells share certain fundamental features, including a cell membrane, cytoplasm, ribosomes, and ________ carrying hereditary information.

BIO la-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS Figure 1.2: Prokaryotic and eukaryotic cell structure Pilot questions 1.2 1. Define prokaryotic cell and name two organism groups that have this cell type. 2. Define eukaryotic cell and name two organism groups that have this cell type. 3. Explain the function of membrane-bound organelles in eukaryotic cells. 4. Compare the typical size range of prokaryotic and eukaryotic cells. 5. Name three features shared by both prokaryotic and eukaryotic cells. 1.3 Plant and Animal Cell Differences 1.3.1 Distinctive plant cell features Plant cells possess a rigid cell wall (composed primarily of cellulose) surrounding the cell membrane, providing structural support and shape, alongside chloroplasts (organelles containing

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