A2.2 Cell Structure

What is the diameter of the goblet cell?

• 80000 µm

• 250 µm

• 20 µm

• 80 µm

Answer explanation

Accurately, measure the scale bar length in mm, measure the diameter of the cell, in mm
divide cell diameter by scale bar and multiply by 100µm.

You can often estimate the size using the scale bar and your thumb or a pen.

Human red blood cells are circular and 0.6 μm in diameter. A photograph of a red blood cell is shown as an illustration in a book with a diameter of 1.2mm. What is the magnification of the diagram?

• 400 X

• 20 X

• 2000 X

• 0.5 X

Answer explanation

Convert 1.2 mm into μm by multiplying x 1000 = 1200 μm (so that both units are the same). Then you can see that 0.6 x 2000 = 1200. Or use the formula Magnification = Image size/true size. If the photograph is larger than the cell, the magnification could not be 0.5x which would make it smaller. Eliminate obviously incorrect answers.

Which of the following is the best estimate of the length (from top to bottom) of an epidermal cell?

• 0.007 mm

• 7 μm

• 0.7 mm

• 70 μm

Answer explanation

The cells are approximately the same size as the scale bar.
This would make 70µm the closest estimate.

What is the structure of the genetic material found in a mitochondrion?

• Single molecule, double helix, associated with protein.

• Single molecule, linear, double helix.

• Single molecule, circular, double helix.

• Several molecules, linear, double helix.

Answer explanation

Mitochondrial DNA is a single helical molecule, not associated with protein and circular in shape. The same as prokaryote nucleoid DNA.

Which structure, visible in the image, could be used as evidence supporting endosymbiosis?

• Chloroplast

• Ribosomes in the cytosol.

• The Golgi apparatus

• Mitochondrion

Answer explanation

The mitochondria provide evidence supporting endosymbiosis because they have:

• a double membrane

• 70S ribosomes

• DNA

What is the best definition of endosymbiosis?

• Two cells each provide materials for each other and both survive.

• A cell is taken into another cell and develops a relationship in which both cells benefit.

• A cell provides materials for another cell and both cells survive.

• A cell engulfs another cells and benefits by digesting it. 

Answer explanation

Endosymbiosis is where a cell engulfs another cell and it continues to live inside the cell.

The engulfed cell provides something for the host cell, and gets something in return.  Both cells benefit.

What is the main function of the large organelle (A) seen in the cell?

• Storage of starch

• Photosynthesis

• Aerobic respiration

• Storage of genetic material

Answer explanation

The  organelle shown is the nucleus, it stores the genetic information, DNA and is the location of DNA replication and Transcription.

The image is of a prokaryotic cell. Which feature defines the cell as prokaryotic?

• Flagella

• 80s ribosomes

• Cell wall

• Nucleoid DNA loop

Answer explanation

Naked DNA in a single molecule shaped like a loop (nucleoid) defines a cell as prokaryotic.

What are the organelles shown by the labels X & Y?

• X is the cell wall and Y is the nucleus.

• X is a chloroplast & Y is a mitochondrion.

• X is the plasma membrane & Y is a chloroplast.

• X is the cell wall & Y is a mitochondrion.

Answer explanation

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

The pale area below Y is the vacuole.

Organelle Y is a mitochondrion, you can tell this by its size, and the presence of membranes inside.

Between X and Y is the chloroplast which is larger than the mitochondrion and has a different internal membrane structure.

This electron microscope image shows a group of prokaryotes.

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

• Plasma membrane, ribosomes and mitochondria.

• Cell wall, plasma membrane and nucleus.

• Cell wall, plasma membrane.

• Cell wall, plasma membrane and lysosomes.

Answer explanation

Prokaryotes have a cell wall (of peptidglycan) and all cells have a membrane. They do not have membrane bound organelles.