Ultrastructure of cells quiz 1.2

This is a quiz of multiple choice style questions about the Ultrastructure of cells topic 1.2 for SL students.

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Each question has a helpful note written by an examiner.  Great for revision.

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The image below shows three structures as seen in an electron microscope.

Which of the structures are prokaryote cells?

Students are expected to be able to recognise and draw the simple structure of Prokaryote cells.

There is no compartmentation in prokaryote cells, and as membranes can be seen in structure B (a mitochondrion) it is not a prokaryote.

It is also expected for students to understand something about the resolving power of electron microscopes. They can create images of objects between 10µm and 1nm whereas light microscopes resolve details between 1mm and 1µm.

 

The electron microscope image below shows an organelle found in both animal and plant cells.
The black line is a scale bar showing 1µm.

What is the name of the organelle?

Know how to identity the organelles in eukaryotes and draw their compartmentalised structure.
A mitochondrion (pleural = mitochondria) has an outer membrane and inner membrane folded into long thing 'flaps' called cristae.

 

The electron microscope image below shows an organelle found in both animal and plant cells.



What is the name of the organelle?

Know how to identity the organelles in eukaryotes and draw their compartmentalised structure.
The rER has parallel membranes covered in dots, which are ribosomes, used for making proteins, for secretion from the cell.

 

The electron microscope image below shows an organelle found in both animal and plant cells.

What is the name of the organelle?

This organelle is one of the larges in the cell, the nucleus. The arrow points to an area of 'chromatic' within this organelle.

 

The electron microscope image below shows an organelle found in eukaryote cells.

What is the name of the organelle?

Chloroplasts are distinctive because they have stacks of membranes inside, called grana, which hold the chlorophyll that absorbs light.

 

What is the structure labelled X most likely to be in this electron microscope image?

Students are expected to be able to identify organelles from microscope images of cells.  The nucleus is distinctive because it is about 10µm in size, and it has black dots in it, chromatin, and sometimes one or more dark patches within the nuclear membrane. It also has a double membrane, not often easily visible.

 

If you found a eukaryote cell in an electron microscope image, and it contained a lot of rER, Golgi apparatus and many darkly stained vesicles, what do you think the function of the cell is most likely to be?

Student are expected to explain how the composition of organelles will be different in cells with different functions,

(eg. goblet cells which make mucus (a protein) will contain lots of rER and vesicles of mucus, and palisade mesophyll cells which do photosynthesis will contain lots of chloroplasts)

 

Why is it that prokaryotes can divide by the simple process of binary fission, but eukaryotes have to divide by the more complex process of mitosis?

To explain how the structure of prokaryotes allows them to divide by binary fission you could mention:

  • Prokaryotes have a single chromosome, eukaryotes have multiple chromosomes
  • Prokaryotes have no nuclear membrane, which eukaryotes have.

 

This electron microscope shows a group of prokaryotes.

What structures are most likely to be found inside these cells?

Skill: you should know how to draw prokaryotic cells (with a cell wall, plasma membrane, cytoplasm, pili, flagella, 70s ribosomes and nucleoid.) and eukaryotic cells (free 80s ribosomes, rough endoplasmic reticulum (rER), lysosome, Golgi apparatus, mitochondrion and nucleus)

 

The electron microscope image below shows a cell.

What are the organelles shown by the labels A & C?

If you look closely at A, it points to the plasma membrane, it is close to the cell wall, but not touching the chloroplast.

This is a plant cell, unusual because it doesn't have a large central vacuole.

Organelle C is a mitochondrion, you can tell this by the size, and the membranes inside.

 

How does the presence of membrane bound organelles benefit eukaryotic cells?

Eukaryote cells (approx. 100µm in diameter) are much larger than prokaryote cells (approx 1µm) and so the concentration of reactants in the cytoplasm would be more dilute if all the metabolism happened in the cytoplasm.

Specialist organelles, like mitochondria keep the enzymes for aerobic respiration in one place, which increases their concentration, and increases the rate of reactions.

 

What do we mean by, "a resolving power of 0.1µm", when describing microscopes?

The resolving power is the ability to separate objects, to produce separate images of two objects.

 

Total Score:

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