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Cytology · Year 1 · Medical University of Sofia

11

Cell. External and internal morphology of the eukaryotic cell. Organelles

Free notes for topic 11 of the Cytology syllabus, open without an account. Written by a senior student against the syllabus question and checked line by line by a second student before publishing. How content is made

Updated

Summary

note

A eukaryotic cell is larger than a prokaryotic cell, 10 to 100 μm, and its defining feature is the nucleus, which houses the DNA and is surrounded by cytoplasm.

Three membrane-bound organelles carry most of the work: mitochondria for ATP production, the endoplasmic reticulum (rough for protein synthesis, smooth for lipid synthesis), and the Golgi apparatus for sorting lipids and proteins.

Eukaryotic organisms are usually multicellular and sometimes unicellular, and eukaryotic cells are found in animals, humans and plants. Animal cells have a centrosome and lysosomes; plant cells have a cell wall, a central vacuole, chloroplasts and plastids.

1. Key points

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The features that define the eukaryotic cell:

  • It is larger than a prokaryotic cell, with a size of 10 to 100 μm.
  • The nucleus houses the DNA and is surrounded by cytoplasm.
  • Eukaryotic organisms are usually multicellular, sometimes unicellular.
  • It is found in animals, humans and plants.

2. The membrane-bound organelles

note

Three named organelles and what each is for:

  • Mitochondria are for ATP production.
  • The endoplasmic reticulum comes in two forms: rough ER for protein synthesis and smooth ER for lipid synthesis.
  • The Golgi apparatus is for the sorting of lipids and proteins.

The rough and smooth distinction is worth pinning down now, because it recurs in every later topic: rough ER carries ribosomes and therefore makes protein; smooth ER has none and makes lipid.

Diagram of a eukaryotic animal cell with the pinocytotic vesicle, lysosome, Golgi vesicles, rough endoplasmic reticulum, smooth endoplasmic reticulum, cell membrane, mitochondrion, Golgi apparatus, nucleolus, nucleus, centrioles, microtubules, cytoplasm and ribosome labelled
Diagram of a eukaryotic animal cell with the pinocytotic vesicle, lysosome, Golgi vesicles, rough endoplasmic reticulum, smooth endoplasmic reticulum, cell membrane, mitochondrion, Golgi apparatus, nucleolus, nucleus, centrioles, microtubules, cytoplasm and ribosome labelled

3. Animal cells against plant cells

note

Both are eukaryotic, and the differences are a short list.

  • Animal cells have a centrosome and lysosomes.
  • Plant cells have a cell wall, a central vacuole, chloroplasts and plastids.
Cell organellePlant cellAnimal cell
Cell wallPresentAbsent
Cell membranePresentPresent
NucleusPresentPresent
Nuclear membranePresentPresent
PlastidsPresentAbsent
CytoplasmPresentPresent
VacuolesPresentPresent

Only two rows in that table differ: the cell wall and the plastids. Vacuoles are present in both, although the large central vacuole is a plant feature.

Diagram of a plant cell labelled with cell wall, cell membrane, Golgi vesicles, ribosome, Golgi apparatus, smooth endoplasmic reticulum, chloroplast, vacuole membrane, nucleolus, nucleus, rough endoplasmic reticulum, raphide crystal, druse crystal, large central vacuole, amyloplast with starch grain, mitochondrion and cytoplasm
Diagram of a plant cell labelled with cell wall, cell membrane, Golgi vesicles, ribosome, Golgi apparatus, smooth endoplasmic reticulum, chloroplast, vacuole membrane, nucleolus, nucleus, rough endoplasmic reticulum, raphide crystal, druse crystal, large central vacuole, amyloplast with starch grain, mitochondrion and cytoplasm

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