뒤로Cell Structure, Classification, and Membrane Biology: Study Notes
스터디 가이드 - 스마트 노트
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Drugs that Target Bacterial Cells
Antibiotics and Their Mechanisms
Antibiotics are chemical agents used to treat bacterial infections by targeting specific features of bacterial cells. Their effectiveness relies on their ability to distinguish between bacterial and human cells.
Antibiotics: Drugs that disable or kill infectious bacteria.
The goal of antibiotic treatment is to kill invading bacteria while minimizing harm to the human host.
Most antibiotics are selective because they bind to structures found only in bacterial cells, such as unique cell wall components or ribosomes.
Researchers continue to explore the unique structures of bacterial cells to design and discover new antibiotics.
Microscopic World of Cells
Cell Theory and Diversity
Cells are the fundamental units of life, and all living organisms are composed of one or more cells. The study of cells reveals their diversity in structure and function.
Organisms can be single-celled (e.g., most prokaryotes and protists) or multicellular (e.g., plants, animals, fungi).
Cell theory: All living things are composed of cells, and all cells come from earlier cells.
Each cell in your body and other organisms was formed by division of a previously living cell.
Cell size varies greatly; cognitive thinking about scale is important in cell biology.
Two Major Categories of Cells
Prokaryotic vs. Eukaryotic Cells
Cells are classified into two main groups based on their structural characteristics: prokaryotic and eukaryotic cells.
Prokaryotic cells: Include organisms from the domains Bacteria and Archaea. These cells lack a nucleus and most membrane-bound organelles.
Eukaryotic cells: Include organisms from the domain Eukarya (plants, animals, fungi, protists). These cells have a nucleus and various membrane-bound organelles.
Below is a comparison table summarizing the key differences between prokaryotic and eukaryotic cells:
Prokaryotic Cells | Eukaryotic Cells |
|---|---|
First evolved approximately 3.5 billion years ago | First evolved approximately 2.1 billion years ago |
Found in bacteria and archaea | Found in protists, plants, fungi, and animals |
Smaller, simpler structure | Larger, more complex structure |
No membrane-bound organelles | Membrane-bound organelles (e.g., nucleus, ER, mitochondria) |
DNA concentrated in a region called the nucleoid, not enclosed by a membrane | DNA enclosed within a membrane-bound nucleus |
Most have cell walls | Some have cell walls (plants, fungi); animal cells do not |
Have ribosomes | Have ribosomes |
Membrane Structure
Plasma Membrane and Its Properties
The plasma membrane is a critical structure that separates the living cell from its nonliving surroundings. It regulates the movement of substances into and out of the cell.
The plasma membrane and other membranes of the cell are composed mostly of phospholipids, arranged into a two-layer sheet called a phospholipid bilayer.
The plasma membrane is described as a fluid mosaic:
Fluid: Molecules can move freely past one another.
Mosaic: Diversity of proteins embedded in the membrane.
Each phospholipid has:
Hydrophilic head (water-attracting)
Hydrophobic tail (water-repelling)
Cell Surfaces
Cell Walls and Extracellular Matrix
Cell surfaces provide structural support and mediate interactions with the environment and other cells.
Plant cells have a cell wall made of cellulose fibers, which protects the cell, maintains its shape, and prevents excessive water uptake.
Animal cells lack cell walls but secrete a sticky coat called the extracellular matrix that helps hold cells together in tissues and supports cell communication.
Animal cell surfaces often contain cell junctions, structures that connect cells together and allow for coordinated activity within tissues.
