Question

Name the cell organelles that are visible only when viewed by an electron microscope. also mention thier function.

Answer 1

For organelles that can be seen under the light microscope are mainly the protoplasm: nucleus, cytoplasm, cell membrane, chloroplasts and cell wall (last 2 organelles are only present in plant cells).

Technically everything else are not visible under the light microscope, even if you uses the highest magnification available on light microscope (usually with the magnification of 1,000x) :(

And hence, electron microscopes will come in handy now. So, these are the organelles that I know so far which are only visible under the electron microscopes (highest magnification to more than 200,000x):

(1) mitochondria (mitochondrion for singular): It is a small oval or sausage-shaped organelle, containing membrane folds, which releases energy during aerobic respiration for cellular activities. Where glucose (from starch of the food we consume) and oxygen (taken in from surroundings) are required to produce water, carbon dioxide and energy. This energy would then be used for cell activities such as growth and reproduction.

(2) Ribosomes: They are small round structures which has the function of synthesizing proteins needed for the cell. There are 2 types of ribosomes, it could be a free lying ribosome in the cytoplasm or attached onto the endoplasmic reticulum (ER). The kinds that lie in the cytoplasm produces protein requires by the cell itself. Whereas the ones that are attached onto the ER produces protein that will be secreted out out of the cell.

(3) Rough Endoplasmic Reticulum (RER): It is a network of flattened spaces lined with a membrane and connected with layers. It is covered with ribosomes, thus it seems “rough on the surface”, and it is also continuous with the nuclear envelope. Its main function is to transport proteins that were produced by the ribosomes to the Golgi Apparatus for further chemical modify, by storing the substances into vesicles.

(4) Smooth Endoplasmic Reticulum (SER): It has similar structure shape as the RER except that it is more tubular and does not have any ribosomes attached onto it, so it has a “smooth surface”, which is connected to the RER. Its jobs are to synthesize fats and steroids (such as sex hormones) as well as to detoxify harmful substances into harmless substances. As such, organs that carries the function of detoxification such as the liver would have more SER. The substances that are produced by the SER would also be transported to the Golgi Apparatus for further modification.

(5) Golgi Apparatus or Golgi body (GA): The GA is made up of layers of flattened spaces surrounded by membranes that are not connected. Its function is to chemically modify substances produced by the ER (note that both SER and RER are under the ER group, hence when I mention ER, it is referring to both) and to store and package these modified products into vesicles for secretion out of cell.

(6) Vesicles: In animal cells, they are small, round sac that contains substances and proteins which are enclosed by the cell’s membrane. Their job is to transport the substances in/out of the cell. You could imagine them as delivery services throughout the cells, to get substances from one organelle to the next. [Be careful not to confuse it with vacuoles, they are different things!]

organelles (3), (4), (5) and (6) are part of transportation in the cell. Here’s one example to better understand how they work together, example, production of milk:

The ribosomes on the RER produces milk protein such as lactose, the vesicles with the milk proteins would be pinched off from the RER and proceed to the GA, where it will fuse and pour its contents into the GA. From there, it will be chemically modified to form milk, where secretory vesicles containing the milk would be pinched off from GA. It will then fuse with the cell membrane and the milk would be released out of the cell. This is practically where the mammalian milk comes from.

made up of deoxyribonucleic acid (otherwise known as your DNA) which stores your hereditary information as well as instructions for cellular activities. When under cell division (aka mitosis) the threads condenses and form highly coiled structures known as chromosomes, when in its chromosomes form, it is visible under the light microscope.

Okay, so these are the organelles which I know that are visible under electron microscopes. It was fun for me write it out, thanks for the question! I do hope this would help! :D