Main Difference – Lysosome vs Ribosome
Lysosome and ribosome are two components found in the cells. Lysosome is only found in animal cells whereas ribosomes are found in both plant and animal cells. Lysosome is a membrane-bound organelle, containing enzymes for the lysis of either nefarious substances or weary organelles. Ribosomes decode the genes, encoded in mRNAs in order to synthesize an amino acid chain. The main difference between lysosome and ribosome is that lysosome contains the digestive enzymes in the cell whereas ribosome synthesize proteins required by the cell, from the transcribed mRNA molecules.
This article looks at,
1. What is a Lysosome
– Structure, Function
2. What is a Ribosome
– Structure, Function
3. What is the difference between Lysosome and Ribosome
What is a Lysosome
Structure of Lysosome
A lysosome is a membrane-bound organelle found in all animal cells. It is a spherical-shaped vesicle which contains hydrolytic enzymes. Lysosomes are comparatively large in size and vary from 0.1-1.2 µm. They are composed of membrane proteins and lysosomal lumen enzymes. Lysosomal lumen contains about 60 different digestive enzymes. These enzymes are produced by rough ER and exported into the Golgi apparatus. Small vesicles containing the enzymes are released from the Golgi and are later fused into large vesicles. Genetic defects in the genes, which encode the lysosomal digestive enzymes, lead to the accumulation of a particular unwanted substance in the cytosol. Thus, these defects are responsible for several cardiovascular diseases, neurodegenerative disorders and several cancers.
Functions of Lysosome
The hydrolytic enzymes break down unwanted materials in the cytoplasm by engulfing them into the lysosome. These unwanted materials can be either biomolecules like nucleic acids, peptides, carbohydrates and lipids, or exhausted organelles. The major class of hydrolytic enzymes is cathepsins. Carbohydrates are degraded by alpha-glucosidase. The lysosome is considered to act as the cells’ waste disposal system. This hydrolytic enzyme requires acidic pH, ranging from 4.5 to 5.0 for their optimal activity. Protons (H+ ions) are pumped into the lumen of the lysosome in order to maintain the acidic pH as it is. The pH in the cytosol is usually 7.2. The hydrolytic reactions are limited in the lysosome lumen. The required acidic pH by the hydrolytic enzymes ensures that the hydrolytic reactions do not occur in the cytosol.
Other than the unwanted polymer degradation, lysosomes exhibit some other functions. They fuse with other organelles to digest cellular debris or large structures with phagosomes cooperatively. Phagosomes are capable of clearing out the damaged structures, including bacteria and viruses by a process called phagocytosis.
Figure 1: Phagocytosis
Lysosomes are involved in secretion, cell signalling, plasma membrane repair and energy metabolism.
What is Ribosome
A ribosome is a molecular machine found in both prokaryotic and eukaryotic cells. Ribosome facilitates the linking of amino acid precursors in an order which is specified by the messenger RNA (mRNA). It is composed of two unequal subunits called small subunit and the large subunit.
Structure of Ribosome
Ribosome is made up of ribosomal RNA (rRNA) and ribosomal proteins. Ribosomal proteins have no function in translation. They assemble rRNA to produce two subunits. These two subunits are arranged together to form the translational apparatus of the ribosome.
Bacterial ribosomes consist of one to two rRNA molecules. The diameter of the prokaryotic ribosomes is around 20 nm. Prokaryotic ribosome is 70S and is composed of 30S small subunit and 50S large subunit. It consists of 65% rRNA. Eukaryotic ribosomes consist of one to three large rRNA molecules. Ribosomes in eukaryotes are around 25-30 nm in diameter. Eukaryotic ribosome is 80S and is composed of 40S small subunit and 60S large subunit. It consists of 35% rRNA in their ribosomes. Eukaryotic organelles such as chloroplasts and mitochondria contain 70S ribosomes.
Functions of Ribosome
The major function of ribosome is protein synthesis. The small subunit reads the mRNA while the large subunit facilitates the linking of the precursor amino acids into a polypeptide chain. The process is referred to as translation.
Figure 2: Translation
Ribosomes can be found as free or membrane-bound. Some eukaryotic ribosomes are bound to the rough ER. Other ribosome types can be found freely-moving in the cytosol. Membrane-bound ribosomes import the synthesized polypeptide chain into rough ER in order to achieve further modifications and protein folding into 3-D structure. Proteins are required by the cell in various functions such as directing chemical processes, repairing damage and cell signalling.
Difference Between Lysosome and Ribosome
Membrane
Lysosome: Lysosome is enclosed by a membrane.
Ribosome: Ribosome is not enclosed by a membrane.
Type of Cell
Lysosome: Lysosome can be found only in eukaryotic animal cells.
Ribosome: Ribosome can be found in both prokaryotic and eukaryotic cells.
Size
Lysosome: Lysosome is large, 0.1-1.2 µm in size.
Ribosome: Ribosome is comparatively small, 20-30 nm in size.
Composition
Lysosome: Lysosome is composed of membrane proteins and digestive enzymes.
Ribosome: Ribosome is composed of rRNA and ribosomal proteins.
Localization
Lysosome: Lysosomes are equally distributed in the cytoplasm.
Ribosome: Ribosomes can be found either bound to the endoplasmic reticulum or remained scattering in the cytoplasm.
Segmentation
Lysosome: Lysosome is not a segmented organelle.
Ribosome: Ribosome consists of unequal two units, the small and large subunits.
Function
Lysosome: Lysosome is involved in intracellular digestion.
Ribosome: Ribosome is involved in the translation of mRNAs.
Conclusion
Both lysosomes and ribosomes are components of a cell. Lysosomes are membrane-bound organelles found in animal cells, but rarely in plant cells. They carry digestive enzymes to hydrolyze unwanted materials in the cell. Ribosomes are a universal component of the cell though they possess different sizes in the structure. Ribosomes translate the information stored in mRNA into an amino acid sequence of a protein. Therefore, the main difference between lysosome and ribosome is in their function in the cell.
Reference:
1.“Lysosome”. Wikipedia, the free encyclopedia. 2017. Accessed 02 March 2017
2.“Ribosome”. Wikipedia, the free encyclopedia. 2017. Accessed 02 March 2017
Image Courtesy:
1. “Figure 04 04 04” By CNX OpenStax – (CC BY 4.0) via Commons Wikimedia
2. “Figure 04 03 06” By CNX OpenStax – (CC BY 4.0) via Commons Wikimedia
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