Cell ultrastructure and functions to include:
cell walls
mitochondria
chloroplasts
cell membrane
vacuole
nucleus
ribosomes
plasmids
using examples from typical plant, animal, fungi and bacteria cells.Cytoplasm: The cytoplasm is the liquid part of the cell. It consists mainly of water and has many different substances dissolved in it. Many of the cell's chemical reactions occur in the cytoplasm.
Cell membrane: The cell membrane contains the contents of the cell and provides a barrier to control what enters and leaves the cell. The cell membrane is often described as "selectively permeable" as it allows some but not all substances across (permeable) and can choose which substances can pass across (selective). We'll learn more about this in the transport topic.
Nucleus: The nucleus controls everything which takes place in the cell. It does this as it is the site of the cell's DNA. DNA contains the genetic code which is translated into proteins. All of the chemical reactions which take place in cells are controlled by these proteins. You'll learn more about all of this in the DNA and Enzymes topics.
Mitochondria: Mitochondria are the power houses of animal, plant and fungal cells. They are found in the cytoplasm and the majority of the respiration chemical reactions take place in the mitochondria, which releases chemical energy from food molecules. Obviously, we'll discuss this in more detail in the Respiration topic.
Ribosomes: Ribosomes are tiny structures which are also found in the cytoplasm. Ribosomes are the sites of protein production in cells. We'll discuss this in more detail in the DNA & Protein Production topic.
Although the diagram above shows the typical structures of an animal cell, very few animal cells would actually look anything like this. Animal cells are specialised for their functions. Look at the following diagrams of different animal cells...why do they have different structures?Red Blood Cell: Biconcave shape provides a large surface area to absorb oxygen. Also mature cells have no nucleus to increase the volume of the oxygen-binding haemoglobin protein molecules.
Nerve Cell: Long, thin shape to transmit nerve impulses. High concentration of mitochondria to provide energy for nerve impulse transmission.
Small Intestine Epithelial Cell: Large surface area of membrane lining the gut to absorb the products of digestion. High concentration of mitochondria to provide the energy required for active transport.
Explanation:
