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They key points covered in this video include:
1. Introduction to Cells - Eukaryotes and Prokaryotes
2. The Structure of an Animal cell
3. The Structure of a Plant Cell
4. The Structure of a Bacteria Cell
5. Additional Subcellular structures

Introduction to Cells - Eukaryotes and Prokaryotes

Cells are the building blocks of organisms - they make up all living things. Cells are either prokaryotic or eukaryotic. Animal and plant cells are eukaryotic - they are complex and relatively large. The cells are between 10 - 100 micrometers in size. Eukaryotic cells have genetic material contained in the nucleus. Bacterial cells are prokaryotic - they are simple and smaller than eukaryotic cells at 1 - 10 micrometers in size. Prokaryotic cells don't have a nucleus - they have genetic material that floats in the cytoplasm. They both have sub-cellular structures


The Structure of an Animal Cell

There are five main sub-cellular structures. The nucleus contains the cell's genetic material. The genetic material controls the cell's activities. The genetic material is arranged as chromosomes - this determines the cell's appearance and function. The genetic material inside the nucleus also carries instructions on making new cells or organisms. The cytoplasm is a gel-like substance in the cell. This is the site of most chemical reactions, which are controlled by proteins called enzymes - these reactions are essential to survive. The cell membrane surrounds the cytoplasm. It holds the cell together and is a selective barrier that controls the movement of substances in and out of the cell. Cell membranes also have receptor molecules. The mitochondria is where the reactions for aerobic respiration take place. Respiration transfers energy to the cell using a reaction between oxygen and glucose - this reaction involves enzymes. The ribosomes are involved in making proteins (protein synthesis). Specifically, translation (the second part of protein synthesis) takes place here


The Structure of a Plant Cell

Plant cells have all the components of an animal cell. They also have three more sub-cellular structures - this is because unlike animals, plants have to make their own food and stay in the same place. The cell wall surrounds the cell. It is rigid and made out of a fibre called cellulose - its function is to support and strengthen the cell. The vacuole is large and contains cell sap (a solution of sugar and salt). Its function is to support the cell by maintaining internal pressure to keep the cell rigid. This helps to support the plant and keep it from wilting. The chloroplasts are the site of photosynthesis - this is what makes the food for plants. Chloroplasts are only in the green parts of the plant. They contain green chlorophyll to absorb and transfer light from the Sun to the cell for photosynthesis

The Structure of a Bacterial Cell

Bacterial cells have a different structure to animal and plant cells. Bacteria are made of just one cell - they are unicellular. Bacteria are also very small so to see them we use microscopes. We can see bacteria on agar plates where millions of bacteria form a colony. Like plant cells, bacteria have a cytoplasm, cell membrane, cell wall and ribosomes. But they do not have a "true" nucleus as the circular DNA strand containing the genetic material floats in the cytoplasm. This is called a bacterial chromosome. They also have plasmids. These are small loops of DNA not part of the main chromosome - they store extra genes. Plasmids can be passed on between bacteria - the genes on plasmids may help bacteria to survive difficult conditions. Some bacteria have flagella (singular: flagellum) which are hair-like extensions from the cell. This is used for movement in liquids through rotation. They also have a cell wall made of a substance called peptidoglycan - like in plant cells, this cell wall holds the cell together and protects it. There are different types of bacteria: Escherichia coli (E. Coli) is bacteria that causes food poisoning. Streptococcus bacteria causes sore throats

Additional Sub-Cellular Structures

Bacteria also have additional sub-cellular structures that are adaptations to their environment. For example, bacterial cells that attach to structures have pili that allow them to do this - these are hair like structures on the surface of cells. Pilli can be used to transfer genetic material between bacterial cells. Bacteria can also have slime capsules outside the cell wall that allow them to stick to smooth surfaces. They also keep the bacteria from drying out and protects them from poisonous substances.

Summary

1. Cells are the building blocks of life
2. Cells can either be prokaryotic or eukaryotic
3. Animal cells have a nucleus, cell membrane, mitochondria, cytoplasm and ribosomes

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