At the end of the lesson, you will be able to do the following:
Describe the structure and the functions of cell organelles.
Discuss the various plant and animal cell organelles.
Differentiate between rough and smooth endoplasmic reticulum.
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Does the cell function like a modern city?
All living things are made of cells. In multicellular organisms, cells with similar or coordinated functions work together and perform specific activities that help to maintain the healthy function of the organism. The cell can be compared to a modern city. As city government is made of different departments, a cell is made of different functional subunits called organelles.
The mitochondria are like the nuclear power plants of the city. It produces energy for the cell. Lysosomes are like the recycling plants of the city. They deal with cellular waste. The Golgi apparatus is like the post office of the city. It packages and transports proteins to different destinations in the cell. An organelle is a specialized subcellular structure that has a specific function.The activity below will introduce you to the names of the different organelles of the cell. This is just an analogy to help you visualize the functional abilities of the cell. In reality, a single analogy cannot capture the intricate and complex roles of all the different functions performed by the organelles of a cell.
What organelles are specific to plants?
Some organelles are found only in plant cells, some only in animal cells, and some in both plant and animal cells. All cells of multicellular organisms have a cell membrane, a nucleus, cytoplasm, ribosomes, mitochondria, endoplasmic reticulum (smooth and rough), peroxisomes, and Golgi apparatus. Besides that, organelles such as a cell wall, vacuoles (smaller in animal cells), chloroplasts, and glyoxysomes are unique to plant cells, whereas only animal cells contain lysosomes and centrioles. Evidence suggests that some plant cells contain lysosomes, but they are not as prominent as in animal cells.
 | Click the card deck to view a card of an organelle. Drag the card to match the appropriate category. |
Is structure related to function?
You now know the names of animal and plant cell organelles. You can now look at the cell membrane that encloses the cell. The internal structure of the organelle determines its function. You will understand that the structure of the organelle contributes to the function of the organelle.
Click the tabs on the image below to understand the structure of a cell membrane and its function.
Hover over here to have a quick review of the structure and function of a cell membrane.
| Click Show Answer to view the answer. |
The sodium-potassium pumps of animal cells pass _________.
Definition: Semipermeable Membrane
The semipermeable membrane has pores in it. The pores allow only certain substances to pass through the cell membrane either from inside the cell to outside the cell or from outside the cell to inside the cell. This property is called semi-permeability.
Definition: Membrane Transport
Membrane transport is the movement of biochemicals and other atomic or molecular substances across biological membranes. It is a major function of the cell membrane.
| See the various options. Click the left or right arrows to select the correct caption for the image shown. Then click the check mark to choose your answer. |
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Does the nucleus contain the instructional manual for the cell?
The nucleus acts as a control center of the cell. It contains chromatin, which is a complex of proteins (histones) and deoxyribonucleic acid which is abbreviated as DNA. The DNA contains all the information needed to make proteins. In fact, the nucleus of every human cell contains 23 pairs of chromosomes or 46 chromosomes. In general, a person inherits a copy of 23 chromosomes from the father and a copy of 23 chromosomes from the mother. Each chromosome contains a single molecule of DNA along with histones. DNA provides instructions on how to make specific types of proteins that are essential for the growth and maintenance of the human body. Therefore, DNA can be compared to the instructional manual for the cell.
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| Click on the nucleus of the cell to see the parts of a nucleus in detail. |
However, if you look into the nucleus, you cannot see the double-stranded DNA. It is packaged as chromatin.
The chromatin is made of DNA, RNA, and nuclear proteins. Also, there is liquid inside the nucleus, the nucleoplasm, which contains chromatin and ribosomes.
Inside the nucleus, a structure called nucleolus is present. The nucleolus is not surrounded by a membrane. It is the center for the assembly of structures called ribosomes.
Ribosomes are made of two protein subunits and ribosomal RNA (rRNA).
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Drag the labels from the bottom to the correct slots.
Are ribosomes tiny protein factories?
Ribosome is a tiny organelle that is the site of protein synthesis in the living cell. Ribosomes are complex, bead-like structures composed of about 40% protein and 60% ribosomal RNA (rRNA).
A ribosome is not a single piece. It is made up of two pieces or subunits that are a mix of protein and ribosomal RNA (rRNA). In eukaryotes, ribosomes contain four strands of RNA and are often attached to the membranes of the endoplasmic reticulum to form rough ER.
Build a Ribosome
Note: In the body, ribosomes are not built like how jigsaw puzzles are assembled. In fact, smaller and larger subunits of ribosomes are assembled to form the complete ribosome structure. The process is much more intricate and it's mediated by enzymes.
Move the puzzle pieces to their correct position to complete the picture.
What is the difference between cytosol and cytoplasm?
Cytoplasm is a fluid that fills the cell. It contains the cytosol and the cell organelles such as mitochondria, lysosomes, endoplasmic reticulum, Golgi apparatus, and vacuoles, are suspended in the cytoplasm.
The fluid part of the cytoplasm outside the organelles is called cytosol. It contains water, nutrients, salts (ions), and waste products.
The cytoplasm is similar to the plasma of the blood. It is the place where the metabolic activities of a cell such as protein synthesis occurs. Metabolic activities in the cytoplasm include both building molecules (anabolism) and breaking down molecules (catabolism). The enzymes in the cytoplasm break down certain large molecules into small molecules and there are also enzymes that help to assemble certain small molecules into bigger molecules. Thus, the cytoplasm is an active part of the cell. The products produced in the cytoplasm are used by the organelles of the cell.
Click the card deck to view a card. Drag the card to match with the correct category.
Show/hide comprehension question...
Which organelle generates the energy required by the cell?
There is always a relationship between the structure of an organelle and its function. The function of mitochondria is to be the powerhouse of the cell since they provide energy to the cell.
Click the tabs on the image below to learn more about mitochondria structure and function.
Hover over here to have a quick review of structure and function of mitochondria.
| Click Show Answer to view the answer. |
Is there a waste management system in the cell?
Lysosomes are the organelles that are unique to animal cells. They are vesicle-like organelles that contain many biochemical catalysts called digestive enzymes (hydrolases). The enzymes break down food molecules, old cell parts, and harmful bacteria. Evidence suggests that some plant cells contain lysosomes, but they are not as prominent as in animal cells. Please play this step by step animation that illustrates the function of lysosomes.
Lysosomes are covered by a membrane that keeps their strong digestive enzymes inside. Sometimes the contents of lysosomes are released within the cell leading to the autolysis (self-liquefying) and death of the cell (apoptosis). In such circumstances lysosomes have been aptly named "suicide bags."
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Do tiny structural differences matter?
The endoplasmic reticulum (ER) is found inside all eukaryotic cells. It is an independent storage and transport system of the cell, consisting of a network of interconnected membrane tubes. The spaces inside the tubes are called cisternae. The membranes separates the contents of the ER from the contents of the cytosol. Its main function is to operate as a transport system. There are two types of ER, smooth ER and rough ER. Please click on the tab set below to explore both the types of endoplasmic reticulum.
| See the various options. Click the left or right arrows to select the correct caption for the image shown. Then click the check mark to choose your answer. |
Which organelle helps in the transport of proteins in the cell?
The Golgi apparatus, or the Golgi body, is found in most of the eukaryotic cells. In plants, the Golgi complex is called dictyosome.
It was identified in 1897 by an Italian physician, Camillo Golgi, so the organelle was named after him.
Click the tabset below to learn about the structure and function of Golgi apparatus.
Hover over here to have a quick review of structure and function of Golgi apparatus.
Drag the items from the bottom to the slots on the right.
Cells
The cell membrane is double-layered and is not continuous due to the presence of pores in it.
Nucleoplasm is a liquid present inside the nucleus, which contains chromatin and ribosomes.
The nucleolus is not encircled with a membrane.
The ribosomes are built of RNA and protein.
The cytosol is the site for protein synthesis.
The gel-like fluid inside the mitochondria that is enclosed by an outer and an inner membrane.
"Suicidal bag" is another name for lysosomes.
The main function of the endoplasmic reticulum is to operate as a transport system.
Golgi complex was identified by an Italian physician, Camillo Golgi.
| Flip this photoalbum to familiarize yourself with some key words associated with this lesson. |