Bio 101 - Cell Biology
Introduction to Biology
Biology defined as the study of living things.
Encompasses cellular basis, energy metabolism, genetic inheritance, evolution, and diversity of life.
Includes study of microorganisms, plants, and animals.
Links structural and functional relationships in organisms' daily activities.
Draws on chemistry and physics for foundational principles.
Divided into practical biology (e.g., plant breeding, medical science) and theoretical biology (e.g., physiology, biochemistry, taxonomy, ecology, microbiology).
Cell Theory
Basic tenet of biology: All living things comprise one or more cells.
Unicellular organisms consist of a single cell.
Multicellular organisms consist of multiple cells organized into tissues.
Tissues are organized into organs; organs function together as organ systems.
Key historical figures in cell discovery:
Robert Hooke (1665): First to observe cells (cork) through a microscope. Coined the term "cell."
Anton Van Leeuwenhoek: Further cell observations; noted movement in cells (animalcules).
Matthias Schleiden (1838): Proposed all plants are composed of cells.
Theodor Schwann (1839): Concluded all animals are composed of cells.
Rudolf Virchow (1858): Proposed that all cells arise from preexisting cells, encapsulating the cell theory.
Cell Theory Postulates
All living organisms are composed of cells.
The cell is the basic unit of life.
All cells arise from pre-existing cells.
Modern Version of Cell Theory
Additional postulates:
Energy flows within cells.
Genetic information is passed between cells.
Chemical composition of all cells is broadly similar.
Definition of a Cell
Cell defined as the smallest basic unit of life, responsible for life’s processes.
Cells serve as structural, functional, and biological units.
Range in size from to nearly across.
Cells can replicate independently; referred to as building blocks of life.
Components of a cell:
Fluid (cytoplasm) enclosed by a cell membrane, containing biomolecules (proteins, nucleic acids, lipids).
Suspended organelles that perform specialized functions.
Characteristics of Cells
Provide structure/support to organisms.
Vary in shape and size, similar to building bricks.
Complex organizations with specialized organelles performing various functions.
Contains hereditary material (DNA).
Discovery and Study of Cells
Landmark advancements in science due to the discovery of cells; key in understanding life processes.
Understanding cell structures and functions critical to biology.
Characteristics of Cells
Structural and organizational significance of cells in all living organisms.
Organisms can be unicellular or multicellular.
Major Functions of Cells
Support and Structure: Provides a basis for organismal architecture.
Facilitate Growth: Mitosis allows parent cells to divide into daughter cells; essential for growth.
Transport of Substances: Nutrients imported and waste eliminated through active/passive transport.
Passive transport: Molecules like oxygen diffuse across the cell membrane.
Active transport: Larger molecules need energy for crossing cell membranes.
Energy Production:
Plants: Energy through photosynthesis.
Animals: Through respiration.
Reproduction:
Mitosis (asexual reproduction, cells divide) vs. meiosis (producing genetically diverse offspring).
Types of Cells
Cells categorized based on structure:
Prokaryotic Cells: Simpler, older, and single-celled (e.g., bacteria).
Structure: Cell membrane, cell wall, potentially a capsule, no nucleus, contains ribosomes, plasmids.
Reproduction: Via binary fission, possibly conjugation.
Eukaryotic Cells: More complex cells, including multicellular organisms (plants, animals).
Have a true nucleus, multiple chromosomes, and internal membranes (organelles).
Key Differences Between Prokaryotic and Eukaryotic Cells
Feature | Prokaryotic Cells | Eukaryotic Cells |
|---|---|---|
Nucleus | Absent (nucleoid region) | Present |
Size | ||
Examples | Bacteria, Archaea | Plants, Animals |
Reproduction | Generally binary fission | Mitosis and meiosis |
Structure of Cells
Important Cellular Components:
Cell Membrane: Protects cell, controls substance movement. Present in all cells.
Cell Wall: Present in plant cells. Provides shape and rigidity. Composed of cellulose, hemicellulose, and pectin.
Cytoplasm: Jelly-like substance where chemical reactions occur; organelles are suspended within.
Nucleus: Contains genetic material (DNA), sending signals for growth and division.
Organelles: Functional units within the cell, each with specialized roles (e.g., mitochondria for energy production, lysosomes for digestion).
Organizational Level of Cells
Organisms comprise various cells and their functions, working collaboratively in functionalities necessary for life.
Cell Organelles and Their Functions
Vacuole: Maintains turgor pressure in plant cells; contains cell sap.
Lysosome: Digestive organelle containing hydrolytic enzymes.
Nucleus and Nucleolus: Control cellular activities and ribosome synthesis.
Endoplasmic Reticulum (ER): Synthesizes proteins and lipids; divided into rough and smooth ER.
Rough ER has ribosomes for protein synthesis.
Smooth ER synthesizes lipids.
Golgi Apparatus: Modifies, sorts, and packages proteins and lipids for distribution.
Ribosomes: Sites of protein synthesis.
Mitochondria: Powerhouse, generates ATP through respiration.
Chloroplast: Photosynthesis site in plant cells.
Differences Between Plant and Animal Cells
Cell wall (present in plants) vs. cell membrane (present in animals).
Chloroplasts (plants) vs. lack thereof in animals.
Large central vacuole (plants) vs. smaller vacuoles in animals.
Centrioles (animals) that aid in cell division, not present in plants.
Conclusion
Understanding cellular biology is foundational to comprehending complex biological systems, functions, and evolutionary relationships across the spectrum of life.