Cells
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
All cells have a number of features in common with each other
Cellular components & functions table
Animal and plant cells are both eukaryotic cells as their genetic material is packaged in a nucleus
Nerve cells (neurones) have a characteristically elongated structure which allows them to coordinate information from the brain and spinal cord with the rest of the body
Muscle cells contain layers of fibres which allow them to contract. The image above shows skeletal muscle cells
Sperm cells are mobile – their tail helps propel them forward in search of an egg to fertilise
Prokaryotic cells do not have a nucleus, and are much smaller than eukaryotic cells
Prokaryotic cells table
The root hair is an extension of the cytoplasm, increasing the surface area of the cell in contact with the soil to maximise absorption of water and minerals
Xylem cells lose their top and bottom walls to form a continuous tube through which water moves through from the roots to the leaves
Phloem cells form tubes similar to xylem vessels, except the cells still retain some subcellular structures and are therefore living
You may be given some information (including an image) about an unfamiliar cell in an exam, and asked to describe how it’s able to carry out its function. This shouldn’t faze you – just look at the shape of the cell and its subcellular structures.Does the cell have a shape which increases its surface area? Are there lots of ribosomes to make proteins (such as enzymes or hormones), or lots of mitochondria (to transfer lots of energy via respiration)?
Make sure you are comfortable converting between different units
You need to be aware that many subcellular structures in eukaryotic cells are the same size as or bigger than prokaryotic cells!
Size of cells table
A common exam question is to ask you to calculate the size of subcellular structures and then to suggest why they may or may not be present in a certain type of cell.For example:Why do bacterial cells not contain mitochondria?
Practise converting numbers into standard form – you may be asked to do this in the exam!
Take care to look at the units that measurements of cells and subcellular structures are given in.
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