Cells

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Cells are the basis of all life on Earth, producing every living organism, from a single cellular bacteria, through to trillions of cells making up a human.

Sub-Cellular Structures[edit | edit source]

Animal Cells[edit | edit source]

A diagram showing the organelles of an animal cell

Nucleus — contains the cells genetic material. Visible as an opaque area through a light microscope

Cell membrane — the membrane encasing the cell. Flexible, allowing movement. Ensures the cell stays together

Mitochondria — release energy, through respiration, typically from glucose. Allows the cell to carry out metabolic functions

Ribosomes — carry out protein synthesis and the site of DNA transcription


Plant Cell[edit | edit source]

A diagram showing organelles of a plant cell

Nucleus — contains the cells genetic material. Visible as an opaque area through a light microscope

Cell membrane — the membrane encasing the cell. Flexible, allowing movement. Ensures the cells organelles do not spill out.

Cell wall — a strong layer of cellulose and other polysaccharides, making the cell rigid. Ensures that plants can stand upright

Chloroplasts — allow sunlight, water, and carbon dioxide to be converted to glucose, and oxygen. Provide energy for the cell through photosynthesis

Mitochondria — release energy, through respiration, typically from glucose (made by photosynthesis). Allows the cell to carry out metabolic functions

Vacuole — a fluid-filled sac within the cell containing cell sap, mineral ions, and other chemicals essential for the cell to function

Ribosomes — carry out protein synthesis and the site of DNA transcription

Prokaryotic (bacterial) Cell[edit | edit source]

A diagram showing the organelles of a prokaryotic cell

Chromosomal DNA — DNA arranged in chromosomes. Contains most of a prokaryotic cells’ genetic material

Plasmid DNA — small rings of DNA within the cytoplasm of the cell. Allows bacteria to share genetic material throughout a population

Cell membrane — the membrane encasing the cell. Flexible, allowing movement. Ensures the cells organelles do not spill out.

Ribosomes — carry out protein synthesis and are the site of DNA transcription

Flagella — whip-like structures on bacteria, allowing them to move

Some Cells are Specialised to their Function[edit | edit source]

Sperm Cells[edit | edit source]

Sperm cells are the male gamete, used during sexual reproduction of humans.

A diagram showing a sperm cell

Acrosome — the region in the head of the sperm cell containing digestive enzymes. Used to ‘burrow’ through the cell membrane of the egg during fertilisation

Haploid nucleus — the nucleus of a sperm cell contains 23 chromosomes, as it is made by the process of meiosis. This creates haploid cells, which have ½ the number of chromosomes of the parent cell

Mitochondria — sperm cells contain many mitochondrion, to release energy to move the flagellum. These are located in the mid piece

Tail — sperm cells have a tail (flagellum), a whip-like structure, allowing the cell to propel itself during fertilisation

Egg Cells[edit | edit source]

Egg cells are the female gamete, used during sexual reproduction of humans.

A diagram showing the fertilisation of an egg cell with a sperm cell

Nutrients in the Cytoplasm — egg cells contain many nutrients in the cytoplasm to provide sufficient nutrition should the egg be fertilised. Allows the cell division and specialisation immediately after fertilisation to begin

Haploid nucleus — the nucleus of an egg cell contains 23 chromosomes, as it is made through the process of meiosis

Changes in the Cell Membrane after Fertilisation — when an egg cell is fertilised with a sperm cell, the cell membrane changes, preventing any further sperm from fertilising the cell

Ciliated Epithelial Cell[edit | edit source]

A scanning electron micrograph of respiratory epithelial cells

Ciliated epithelial cells have many, small, hair-like projections coming out of their cell membrane.

These projections are used to ‘waft’ waste products out of the trachea (wind pipe) and bronchioles. Mucus is transported out of the lungs with cilia, allowing it to enter the stomach, where it is digested.

These cells have a large proportion of mitochondria, as they use active methods (energy using) to ‘waft’ their hair-like projections.