Definitions [1]
Define Prokaryotic cells.
- It has no true nucleus.
- This type of nucleus is called a nucleoid.
- No nuclear membrane is around the nucleoid.
- It is ranging from 0.003 to 2.0 micrometers in diameter.
Key Points
Key Points: Plastids
- Plastids are present only in plant cells and are of several types—chloroplasts, leucoplasts, and chromoplasts.
- They are double-membraned organelles with a proteinaceous matrix and contain DNA.
- Chloroplasts (green) contain chlorophyll in thylakoids and perform photosynthesis.
- Leucoplasts are colourless, store starch, and have no pigment.
- Chromoplasts are variously coloured, contain pigments like xanthophyll and carotene, and help in pollination by attracting pollinators.
Key Points: Vacuoles & Granules
- Vacuoles are clear spaces containing water or dissolved substances, enclosed by a membrane called the tonoplast.
- Plant cells have fewer but larger vacuoles, while animal cells have smaller ones.
- Vacuoles store water, food, pigments, and waste, and help maintain cell turgidity.
- Some vacuoles contain pigments like anthocyanins (violet-blue).
- Granules are non-living particles (starch, glycogen, fats) that serve as food reserves for the cell.
Key Points: Plant Cell Vs Animal Cell
| Feature | Animal Cell | Plant Cell |
|---|---|---|
| Cell Wall | Absent | Present |
| Chloroplasts | Absent | Present |
| Vacuole | Small or absent | Large central vacuole |
| Shape | Generally round and irregular | Generally rectangular and regular |
| Lysosomes | Present | Present (though less common) |
| Centrioles | Present | Generally absent in most plant cells |
| Plasmodesmata | Absent | Present |
| Microvilli | Present | Generally absent |
| Golgi Apparatus | Present | Present |
| Mitochondria | Present | Present |
| Rough Endoplasmic Reticulum | Present | Present |
| Smooth Endoplasmic Reticulum | Present | Present |
| Ribosomes | Present | Present |
| Nucleus | Present | Present |
| Nucleolus | Present | Present |
| Plasma Membrane | Present | Present |
| Peroxisome | Present | Present |
| Cytoplasm | Present | Present |
| Middle Lamella | Absent | Present |
| Microtubules | Present | Present |
