in Biology

Cells and Organisms

Structure of plant cell

plant_cell_structure-en-svg

Structure of animal cell

612px-endomembrane_system_diagram_en_edit-svg



Organelles

In cell biology, an organelle is one of several structures with specified functions, suspending in the cytoplasm of a eukaryotic cell, or prokaryotic cell.

Examples of which include:

  • Nucleus
  • Mitochondria
  • Endoplasmic Reticulum
  • Golgi Complex
  • Ribosomes
  • Lysosomes
  • Chloroplast (plant cells)
  • … and more

Unlike in eukaryotic cells, prokaryotic cells do not contain membrane-bound organelles. However, they do contain some non-membranous organelles such as ribosomes flagella, and plasmids (circular DNA structures that are not involved in reproduction).

Eukaryotic Cells

Eukaryotic cells have a true nucleus.

  • The nucleus houses DNA

Prokaryotic Cells

Prokaryotic cells do *not* have a true nucleus

  • Their DNA is not separated from the rest of the cell, but is coiled up in whats called a nucleoid.

Differences Between Plan and Animal Cells

# Plant Animal
1 Usually larger in size Comparatively smaller
2 Enclosed by rigid cellulose cell wall in addition to plasma membrane Only enclosed by a thin flexible plasma membrane
3 It cannot change it’s shape Can often change it’s shape
4 Plastids are present. Plants exposed to sunlight contain chloroplast Plastids are usually absent
5 A mature plant contains a large central vacuole Often possesses many small vacuole
6 Nucleus resides on the same side of the peripheral cytoplasm Nucleus usually lies in the centre
7 Centrioles are usually absent Centrioles are practically present
8 Lysosomes are rare Lysosomes are always present
9 Glyoxysomes may be present Glyoxysomes are absent
10 Tight junctions and desmosomes are lacking. Plasmodesmata is present Tight junctions and desmosomes are present between cells. Plasmodesmata is absent
11 Reserve food is generally stored starch Reserve food is usually glycogen
12 Plant cells synthesize all amino acids, enzymes, and vitamins required Animal cells cannot synthesize all required amino acids, enzymes, and vitamins required
13 Spindles formed during cell division in anastral – without esters at opposite polls Spindle formed during cell division is amphiastral. Has an ester at each poll
14 Cytokinesis occurs by cell plate method Cytokinesis occurs by construction or furrowing
15 Plant cells do not burst if placed in hypotonic solution due to the cell wall Animal cells lacking contractile vacuoles usually burst if placed in hypotonic solution


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