Cell Structures (AQA GCSE Combined Science: Synergy: Life & Environmental Sciences): Revision Note

Cell Types

All cells have a number of features in common with each other

• For a cell to be a cell, it has to have the following components:

Cellular components & functions table

• There are two distinct types of cell – eukaryotic and prokaryotic

Eukaryotic cells

• Plant and animal cells are both eukaryotic cells

• They have the components listed in the table above (so a cell membrane, cytoplasm and ribosomes), as well as others

• A defining feature of eukaryotic cells is that their genetic material (DNA) is enclosed within a nucleus

• Eukaryotic cells vary in size, usually between 10 and 100 µm

Animal and plant cells are both eukaryotic cells as their genetic material is packaged in a nucleus

Prokaryotic cells

• Bacterial cells are a type of prokaryotic cell

• A defining feature of prokaryotic cells is that their genetic material is not enclosed within a nucleus, it is found as a single loop of DNA within the cytoplasm

• Additional smaller, circular pieces of DNA called plasmids may also be present

• The cell membranes of all prokaryotic cells are surrounded by a cell wall (usually made from a substance called peptidoglycan)

• Prokaryotic cells are much smaller in comparison to eukaryotic cells, with many measuring ~ 1 µm in size

Prokaryotic cells do not have a nucleus, and are much smaller than eukaryotic cells

Prokaryotic cells table

Animal Cells

• Eukaryotic cells have subcellular structures, each carrying out a particular function

• Organelles are subcellular ‘compartments’ where specific processes take place within the cell

• The main subcellular structures in animal cells are:

  • The nucleus

  • Cell membranes

  • Mitochondria

  • Ribosomes

  • Cytoplasm

Some cellular structures can only be seen when viewed with an electron microscope

Cell structures table

Plant Cells

• In addition to the subcellular parts found in animal cells, plant cells have:

  • A cell wall made of cellulose (algal cells also have this structural feature)

  • A permanent vacuole filled with cell sap

• Plant cells found in the leaf and stem may also contain chloroplasts

The plant cell shown above contains chloroplasts, so it would be found in the leaves of a plant

 Plant cell structure & function table