Cells
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课程笔记
Cell Theory and Discovery
- Cells are the basic structural and functional unit of all living organisms.
- Robert Hooke discovered cells in 1665 after observing cork under a microscope.
- Cell theory (Schleiden & Schwann, 1839): all organisms are made of one or more cells, cells are the fundamental unit of life, and all cells arise from pre-existing cells.
Prokaryotic vs Eukaryotic Cells
- Prokaryotes (bacteria & archaea) lack a membrane-bound nucleus; their DNA is in a nucleoid region.
- Eukaryotes (animals, plants, fungi, protists) have a membrane-bound nucleus and other organelles.
- Prokaryotes are generally smaller (0.1–5.0 μm) and simpler; eukaryotes are larger and more complex.
- All prokaryotes are single-celled; eukaryotes can be single-celled (e.g., yeast) or multicellular.
Plant vs Animal Cells
- Both have a cell membrane, cytoplasm, nucleus, mitochondria, ribosomes, and endoplasmic reticulum.
- Plant cells have a cell wall (cellulose), chloroplasts (photosynthesis), and a large central vacuole.
- Animal cells have no cell wall, no chloroplasts, and smaller vacuoles (if any).
- Plant cells are typically rectangular; animal cells are irregular or rounded.
Key Organelles and Their Functions
- Nucleus: contains genetic material (DNA); controls cell activities.
- Cell membrane: semipermeable; controls entry/exit of substances.
- Cytoplasm: jelly-like fluid where chemical reactions occur.
- Mitochondria: site of aerobic respiration; produce ATP (energy).
- Chloroplasts (plants): contain chlorophyll; site of photosynthesis.
- Vacuole (plants): stores sap; maintains turgor pressure.
- Ribosomes: synthesise proteins.
- Cell wall (plants, bacteria): provides structural support and protection.
Prokaryotic Cell Structure
- Prokaryotes have a cell envelope: plasma membrane + cell wall (peptidoglycan); some have a capsule.
- DNA is a single circular chromosome in the nucleoid; plasmids (extra DNA) may be present.
- Ribosomes are smaller than eukaryotic ribosomes (70S).
- Some have flagella (movement) and pili (attachment/conjugation).
- No membrane-bound organelles; some have microcompartments (e.g., gas vesicles, magnetosomes).
Microscopy
- Most cells are microscopic and require a microscope to be seen.
- Light microscopes use visible light; can magnify up to ~1000×.
- Electron microscopes use electron beams; much higher magnification and resolution.
- Stains (e.g., methylene blue) help highlight cell structures.
Animal cell structure showing key organelles.
Plant cell structure with cell wall, chloroplasts and large vacuole.
Prokaryotic cell (bacterium) with key features.
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练习题
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1.What is the basic structural and functional unit of all living organisms?
Easy- ACell
- BNucleus
- COrganelle
- DTissue
2.Which structure is found in plant cells but not in animal cells?
Easy- ACell wall
- BCell membrane
- CNucleus
- DMitochondrion
3.The diagram shows a plant cell. Which labelled structure is the chloroplast?
Easy- AA
- BB
- CC
- DD
4.Which of the following is a function of the cell membrane?
Easy- AControls what enters and leaves the cell
- BProvides energy for the cell
- CContains the genetic material
- DSite of protein synthesis
5.Who first discovered cells and named them after their resemblance to monastery cells?
Easy- ARobert Hooke
- BMatthias Schleiden
- CTheodor Schwann
- DAntonie van Leeuwenhoek
6.A student observes a cell under a microscope. It has a nucleus, mitochondria, and a cell wall. What type of cell is it most likely to be?
Medium- APlant cell
- BAnimal cell
- CBacterial cell
- DFungal cell
7.What is the function of the mitochondria in a cell?
Easy- ATo produce energy (ATP) through respiration
- BTo control cell activities
- CTo carry out photosynthesis
- DTo store water and nutrients
8.The diagram shows a bacterium. Which labelled part contains the genetic material?
Easy- AA (cell wall)
- BB (plasma membrane)
- CC (nucleoid region)
- DD (ribosome)
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