Prokaryotic Cells

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Recommended: Similarities and differences between eukaryotic and prokaryotic cells

Prokaryotic Cells

All living things are made of cells, and cells are the smallest units

that can be alive. Life on Earth is classified into five kingdoms, and

they each have their own characteristic kind of cell. However the

biggest division is between the cells of the prokaryote kingdom

(monera, the bacteria) and those of the other four kingdoms (animals,

plants, fungi and protoctista), which are all eukaryotic cells.

Prokaryotic cells are smaller and simpler than eukaryotic cells, and

do not have a nucleus. Prokaryotic means 'pre-nucleus' and eukaryotic

means 'true nucleus'. The nucleus in eukaryotic cells contains the DNA

in linear chromosomes and is bounded by a nuclear membrane, but since

a prokaryotic cell doesn't have a nucleus and its DNA is a single,

circular coiled molecule that floats freely within the cell and is not

bounded by nuclear membrane nor is it complexed with any proteins. In

addition to the circular DNA some bacteria also contain plasmids.

Prokaryotic cells are far older and more diverse than eukaryotic

cells. Prokaryotic cells have probably been around for 3.5 billion

years, which is about 2.5 billion years longer than eukaryotic cells.

Not all Prokaryotic cells have all the parts shown above. All

bacterial cells have a cell wall, cytoplasm, cell membrane, circular

DNA, food reserve granules, and ribosomes. The capsule (or slime

layer) is a thick polysaccharide layer outside of the cell wall. It is

used for sticking cells together, as a food reserve, as protection

against desiccation and chemicals, and as protection against

phagocytosis. It also sores waste and protects the cell from drying

out. The cell ...

... middle of paper ...

...Do not have chloroplasts

Animal cells don't have chloroplasts but plant

cells do

Do not have endoplasmic recticulum or golgi

body

Do have endoplasmic recticulum and golgi

body

Always unicellular

Often multi-cellular

No cytoskeleton

Always has a cytoskeleton

Cell division is by binary fission

Cell division is by mitosis or meiosis

Reproduction is always asexual

Reproduction is asexual or sexual

Do not have a nucleus or any membrane-bound organelles

Always have a nucleus and other membrane organelles

DNA is circular, without proteins (naked)

DNA is linear and associated with proteins to form chromatin

May have one or more flagella

Have no flagella

Have a protective capsule (or slimy layer)

Do not have a protective capsule (or slimy layer)

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