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Eukaryotic cells keep their genetic material in a nucleus, while in prokaryotic cells the DNA floats freely in the cytoplasm. Notes and 15 questions answered.
Understanding Cell Types: Eukaryotes vs Prokaryotes is part of Cell structure in GCSE AQA Higher Biology.
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Eukaryotic cells keep their genetic material in a nucleus, while in prokaryotic cells the DNA floats freely in the cytoplasm. Notes and 15 questions answered.
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Use this lesson to stay inside Cell structure while connecting the detail back to the wider Cell biology topic.
Read the core explanations from Understanding Cell Types: Eukaryotes vs Prokaryotes before testing yourself from memory.
Every living thing is made of cells, but not all cells are the same. There's a fundamental divide in the living world - some cells keep their DNA locked away in a special compartment, while others let it float freely. This difference is so important that it splits all life into two major groups.
Trap: Many students think 'prokaryotic' means 'simple' and 'eukaryotic' means 'complex'. Actually, both are highly sophisticated - they just organise their contents differently. Bacteria can do things like photosynthesis and nitrogen fixation that many eukaryotes cannot.
Plant and animal cells are the eukaryotes you know best. Picture looking at an animal cell under a microscope - you'd see a clear boundary (the cell membrane), jelly-like contents (cytoplasm), and a dark blob in the centre (the nucleus). The nucleus is like a vault containing all the cell's genetic instructions.
All eukaryotic cells share three essential features: a cell membrane that controls what enters and leaves, cytoplasm where chemical reactions happen, and genetic material safely locked in a nucleus. This nucleus is what makes them 'eukaryotic' - the word literally means 'true nucleus'.
Worked example: Worked Example: Identify and compare two cells
Cell A has a nucleus. Cell B has a single loop of DNA free in the cytoplasm and small rings of DNA. Identify each cell type and explain your evidence.
Answer: A is eukaryotic; B is prokaryotic. A has a nucleus, whereas B has a DNA loop free in its cytoplasm and plasmids.
Exam depth extension: In understanding cell types: eukaryotes vs prokaryotes, connect the two types of cells to plant and animal cells - the eukaryotic stars using clear cause-and-effect statements. When you explain biological processes, include what changes, why it changes, and the consequence for cells, organisms, or populations. If calculations appear, show each step, include units, and end with a sentence that interprets the result in biological context.
Bacterial cells are completely different. They're much smaller - you could fit thousands of bacteria inside a single animal cell. When you zoom in on a bacterial cell, you won't find a nucleus. Instead, the DNA floats freely in the cytoplasm as a single loop.
But bacteria are not simply 'cells without a nucleus'. They have their own special features. The cell membrane is surrounded by a tough cell wall for protection. Most importantly, they often carry extra DNA in small rings called plasmids - think of these as bonus genetic instructions that can be shared between bacteria.
Trap: Students often think bacterial cells have no DNA because they have no nucleus. Wrong! Bacteria have plenty of DNA - it's just not packaged in a nucleus. The main DNA forms a single loop, plus there may be several plasmids floating around.
The size difference is dramatic. A typical bacterial cell is about 1-2 micrometers across. A typical animal cell is 10-30 micrometers. That means you could line up 10-15 bacteria across the width of one animal cell.
This size difference isn't random - it's connected to how the cells are organised. Without a nucleus taking up space and organising things, bacterial cells can pack everything into a much smaller package. They're like efficiently designed studio flats compared to the sprawling mansions of eukaryotic cells.
Exam questions love to test whether you can distinguish prokaryotic from eukaryotic cells. The golden rule: look for the nucleus. If there's a nucleus, it's eukaryotic. If the DNA is scattered in the cytoplasm, it's prokaryotic.
For 6-mark questions comparing cell types, structure your answer: state the key difference (nucleus), describe eukaryotic features, describe prokaryotic features, mention size difference, give examples of each type. Always finish by linking back to the question.
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Move to the related lessons or back to the topic page when you need the wider sequence before exam-style practice.
A prokaryotic cell is a cell with genetic material not enclosed in a nucleus, found in bacteria and archaea. Its main DNA forms a single loop free in the cytoplasm, and it often carries extra small rings of DNA called plasmids, with a cell wall around the cell membrane.
A plasmid is a small ring of extra DNA that bacterial cells often carry as well as their main DNA, which forms a single loop. Plasmids work like bonus genetic instructions that can be shared between bacteria.
The main difference between prokaryotic and eukaryotic cells is the nucleus: eukaryotic cells keep their genetic material in a nucleus, while in prokaryotic cells the DNA floats freely in the cytoplasm as a single loop. Prokaryotic cells are also much smaller. Plant and animal cells are eukaryotic, and bacterial cells are prokaryotic.
Eukaryotic literally means 'true nucleus'. All eukaryotic cells, such as plant and animal cells, share three essential features: a cell membrane that controls what enters and leaves, cytoplasm where chemical reactions happen, and genetic material locked in a nucleus.
Eukaryotic cells are cells with genetic material enclosed in a nucleus. They are found in plants, animals, fungi and protists, and all share three essential features: a cell membrane that controls what enters and leaves, cytoplasm where chemical reactions happen, and genetic material in a nucleus.
Bacteria have plenty of DNA, even though they have no nucleus. The main DNA forms a single loop free in the cytoplasm, and there may also be several plasmids, which are small rings of DNA. Thinking bacterial cells have no DNA because they lack a nucleus is wrong.
The cell wall in a bacterial cell is a tough layer surrounding the cell membrane that protects the cell. Bacterial cells also have cytoplasm, a single loop of DNA and often plasmids, but no nucleus.
Examples of prokaryotes are bacteria and archaea, whose genetic material is not enclosed in a nucleus. Examples of eukaryotes are plants, animals, fungi and protists, whose cells keep their genetic material in a nucleus.
The DNA in a bacterial cell floats freely in the cytoplasm as a single loop, because bacteria have no nucleus. Bacterial cells often also carry extra DNA in small rings called plasmids, separate from the main chromosome.
A cell can be classed as prokaryotic or eukaryotic by looking for the nucleus. If the genetic material is enclosed in a nucleus, the cell is eukaryotic; if the DNA is a loop free in the cytoplasm, often with plasmids, the cell is prokaryotic.
Prokaryotic cells are not just 'simple' and eukaryotic cells 'complex'; both cell types are highly sophisticated and just organise their contents differently. Bacteria can carry out photosynthesis and nitrogen fixation, which many eukaryotes cannot.
Bacterial cells are small, about 1-2 micrometers across, partly because they have no nucleus taking up space and organising things, so they can pack everything into a much smaller package. A typical animal cell is 10-30 micrometers across, so 10-15 bacteria could line up across one.
A 6-mark answer comparing prokaryotic and eukaryotic cells should state the key difference (the nucleus), describe eukaryotic features, describe prokaryotic features such as the DNA loop and plasmids, mention the size difference, and give examples of each type, finishing with a link back to the question.
Bacteria are classified as prokaryotes because their cells have no nucleus. Bacteria still have plenty of DNA, but it is not packaged in a nucleus: the main DNA floats freely in the cytoplasm as a single loop, and there may also be several plasmids.
A typical bacterial cell is about 1-2 micrometers across, while a typical animal cell is 10-30 micrometers. That means 10-15 bacteria could be lined up across the width of one animal cell, and thousands of bacteria could fit inside a single animal cell.