Eukaryotic cells and bacterial cells differ substantially in size. Describe five

Question

Eukaryotic cells and bacterial cells differ substantially in size.   Describe five cell structures that differ in function and/or presence between eukaryotes and bacteria because of this size difference. Explain how these structures are adaptations to the size difference for the bacteria and eukaryotes.Eukaryotic cells and bacterial cells differ substantially in size.   Describe five cell structures that differ in function and/or presence between eukaryotes and bacteria because of this size difference. Explain how these structures are adaptations to the size difference for the bacteria and eukaryotes.

Explanation / Answer

Prokaryotes do not have a nucleus. Instead, their DNA is a single circular molecule freely present in the cytoplasm and not associated with any proteins such as histones. Eukaryotic cells contain membrane-bound nuclei that contains the cell's DNA and direct the synthesis of ribonucleotides and proteins.

Mitochondria, present only in eukaryotes, is the major site for the synthesis of ATP. ATP synthesis through aerobic cellular respiration occurs here. Prokaryotes also produce ATP but the enzymes required for its production are present in the cell membrane.

The endoplasmic reticulum is present attached to the nuclear membrane in eukaryotes. The rough and smooth endoplasmic reticulum are involved in,
Rough ER - collects, stores, packages and transports the proteins made on the ribosomes
Smooth ER - synthesis of lipids and some steroids
Since prokaryotes does not contain a nuclear membrane, ER is absent in them.

The golgi apparatus, present only in eukaryotes, is a stack of flattened membrane discs which receives packages of protein from the rough ER, and is involved in synthesising chemicals before they are secreted from the cell.

Lysosomes, present only in eukaryotes, are small vesicles of membrane that contain enzymes which take part in digestion.

The size of a prokaryotic cell is restricted by its metabolism. Because prokaryotic cells lack organelles, their cellular processes aren’t as efficient as eukaryotic cells, which is why they are unable to grow as large. Increase in the size of a cell leads to increase in nutrient and energy demands. Nutrients enter a cell through the plasma membrane but as a cell gets bigger, the volume of the cell increases faster than the surface area of the plasma membrane and energy demands increase more than the energy supply. To counteract the difference between the supply and demand of nutrients and energy, cells must become more efficient at using their supply of nutrients and energy. Eukaryotic cells with organelles have evolved far more efficient methods for using their supply of nutrients and energy and so they have been able to grow much larger than prokaryotic cells.

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