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Introduction to Cells

Applied Science: BTEC Level 3 National Extended Diploma, topic 1.3.1

Eukaryotic vs Prokaryotic Cells

All life on Earth exists as cells. A cell is the smallest unit of a living thing. All cells can be grouped into either eukaryotic or prokaryotic cells. These different categories have similarities and differences.

Similarities

Similarities

  • Both prokaryotic and eukaryotic cells contain organelles.
  • The cell-surface membrane in eukaryotic and prokaryotic cells is made of a phospholipid bilayer.
  • This bilayer is responsible for controlling the passage of substances across exchange surfaces.
Differences

Differences

  • Prokaryotic cells make up single-celled prokaryotic organisms (e.g. bacteria). In contrast, eukaryotic cells make up complex eukaryotic organisms (e.g. animals, plants, fungi and algae).
  • Eukaryotic cells are larger and more complex than prokaryotic cells.
  • Cells arise from other cells by binary fission in prokaryotic cells and by mitosis or meiosis in eukaryotic cells.
Size comparison

Size comparison

Types of Eukaryotic Cells

Eukaryotic cells have similar structures across different types of organisms. But there are some key differences that are outlined here.

Animal cell

Animal cell

Animal cell

Animal cell

  • Most animal cells have the following organelles:
  • Mitochondria.
  • Ribosomes.
  • Endoplasmic reticulum (ER).
  • Golgi.
  • Lysosomes.
  • Nucleus.
  • Animal cells are enclosed by a cell membrane.
Plant cell

Plant cell

Plant cell

Plant cell

  • Plant cells contain all the organelles found in animal cells.
  • Plant cells also possess:
  • Vacuole (a repository of cell sap).
  • Chloroplasts (the site of photosynthesis).
  • Cell wall (made of cellulose and contains plasmodesmata, through which cells exchange substances with each other).
Algal cells

Algal cells

  • Algal cells and plant cells have an identical set of organelles.
Fungal cells

Fungal cells

  • Fungal cells are similar to plant cells, apart from:
  • There are no chloroplasts in fungal cells.
  • The cell walls of fungal cells are made from chitin instead of cellulose.

Test yourself on Introduction to Cells

  • Which of these statements about prokaryotic and eukaryotic cells is true?

  • Which cells contain organelles?

  • Which of these organelles are NOT found in animal cells?

  • Which organelles are present in plant cells but not in animal cells?

  • Which of these eukaryotes does NOT have a cell wall?

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