Do animal cells have ribosomes?

Ribosomes are important molecular machines in cells that are responsible for synthesizing proteins. Ribosomes play a vital role in both single-celled organisms and complex multicellular organisms. Animal cells, as part of multicellular eukaryotic organisms, are no exception and contain ribosomes. So, how do ribosomes in animal cells work? What are their characteristics? This article will take a deep look at ribosomes in animal cells and analyze their key roles in cell life activities.

1. Definition and structure of ribosome

Ribosomes are molecular complexes responsible for protein synthesis in cells. They translate genetic information (mRNA) to link amino acids in a specific order to form polypeptide chains, which are then folded to form functional proteins. Proteins are necessary for all cell functions, including building cell structures, regulating metabolic processes, and maintaining cell signaling.

1. Composition of ribosomes

The ribosome consists of two parts: the large subunit and the small subunit . Each of these subunits is composed of ribosomal RNA (rRNA) and a variety of proteins . The large subunit and the small subunit work together to complete the translation process of mRNA.

• Small subunit : Responsible for binding to messenger RNA (mRNA) and directing its information into the translation process.

• Large subunit : responsible for catalyzing the formation of peptide bonds between amino acids to produce proteins.

2. Ribosome size and type

In cell biology, the size of a ribosome is often measured by its sedimentation coefficient (Svedberg unit, S). Ribosomes in animal cells have a sedimentation coefficient of 80S , which means they are slightly larger than ribosomes in prokaryotes such as bacteria (70S). 80S ribosomes are further divided into:

• Large subunit: 60S

• Small subunit: 40S

This difference in sedimentation coefficient reflects the differences in ribosome structure and function between eukaryotes and prokaryotes.

2. Distribution of ribosomes in animal cells

Ribosomes are present in all living cells, including animal cells. Ribosomes in animal cells can either be freely suspended in the cytoplasm or attached to the surface of the endoplasmic reticulum, forming the rough endoplasmic reticulum (Rough ER). The functions of these two types of ribosomes are slightly different.

1. Free Ribosomes

Free ribosomes refer to those ribosomes dispersed in the cytoplasm. They are mainly responsible for synthesizing proteins needed inside the cell, and these proteins will not be secreted outside the cell. For example, enzymes and cytoskeleton proteins in the cytoplasm are synthesized by free ribosomes.

2. Ribosomes attached to the endoplasmic reticulum

The ribosomes on the rough endoplasmic reticulum are responsible for synthesizing secretory proteins and membrane proteins . After being synthesized by the ribosomes, these proteins are transported to , and then further transported to the cell membrane or secreted outside the cell. For example, hormones such as insulin are synthesized and secreted by ribosomes attached to the endoplasmic reticulum.

3. The role of ribosomes in protein synthesis

The core function of ribosomes is to perform protein translation , which converts genetic information stored in the cell nucleus into functional proteins and is the core step of gene expression.

1. Translation of mRNA

The ribosome binds to the coding sequence of the mRNA and reads the triplet nucleotide sequence (i.e., codon ) on the mRNA. Each codon corresponds to a specific amino acid. The ribosome cooperates with the transfer RNA (tRNA) to transport the specific amino acid to the synthesis site.

2. Formation of peptide chains

Under the catalysis of the ribosome, peptide bonds are formed between amino acids, and the gradually elongated polypeptide chain extends out from the exit of the large subunit of the ribosome. As each codon is translated, the ribosome moves along the mRNA sequence until the synthesis is completed.

3. Protein folding and modification

Once protein synthesis is complete, the nascent polypeptide chain usually needs to be folded and modified before it can become a functional protein with biological activity. This process may be completed in the cytoplasm, or it may be carried out in the endoplasmic reticulum or Golgi apparatus.

4. Synergistic effects of ribosomes and other cell organelles

Ribosomes work closely with other organelles in animal cells to ensure the normal synthesis, transport and functionality of proteins.

1. Endoplasmic reticulum and Golgi apparatus

Proteins synthesized by ribosomes, especially secretory proteins and membrane proteins, enter the endoplasmic reticulum lumen through ribosomes attached to the rough endoplasmic reticulum. In the endoplasmic reticulum, proteins are folded and initially modified. Subsequently, they are transported to , where they are further processed and finally transported to the cell membrane through vesicles or secreted out of the cell.

2. Mitochondria

Mitochondria are the " energy factories " of animal cells , providing ATP energy for various cellular activities. Ribosomes support the function of mitochondria by synthesizing the proteins needed by mitochondria. At the same time, mitochondria themselves also contain a small number of ribosomes, which synthesize some of the proteins inside mitochondria.

3. Nucleus

Although ribosomes are responsible for the actual synthesis of proteins, their instructions come from DNA in the cell nucleus. DNA is transcribed into mRNA in the cell nucleus, which then enters the cytoplasm through nuclear pores and is translated into protein by ribosomes. Therefore, there is an important synergy between ribosomes and the cell nucleus to ensure the accurate expression of genetic information.

5. Ribosome Evolution and Its Importance in Animal Cells

Ribosomes not only play an important role in animal cells, but are also highly conserved during evolution. Whether it is single-celled bacteria or complex multicellular animals, ribosomes are similar in basic functions. This shows the important position of ribosomes in the evolution of life.

1. Conservation of ribosomes

The core structure and function of the ribosome are almost unchanged in all organisms on Earth, indicating that it is an essential molecular machine for life. By comparing the ribosome structure of different species, scientists can trace the evolutionary history of organisms and even study the ancient origin of life.

2. Ribosome Adaptability

Although ribosomes are highly conserved in their core functions, they have also shown some adaptability in evolution. For example, the ribosomes of eukaryotes are more complex than those of prokaryotes, which is closely related to the need for eukaryotes to synthesize more types of proteins with more complex functions.

6. Ribosome-related diseases and research

Because of the central role of ribosomes in protein synthesis, any factors that interfere with ribosome function can have a profound impact on cell health. Certain genetic diseases are associated with abnormal ribosome function. In addition, viruses (such as the new coronavirus) may hijack the host's ribosomes and use them to produce viral proteins, thereby completing the infection process.

1. Ribosomal diseases

Certain rare genetic diseases, such as Diamond-Blackfan anemia , are caused by defects in ribosomal proteins. These diseases usually lead to abnormal protein synthesis, which in turn affects the normal development and function of tissues and organs.

2. The role of antibiotics

Many antibiotics kill bacteria by inhibiting the function of bacterial ribosomes. For example, tetracycline drugs exert their antibacterial effects by preventing protein synthesis in bacterial ribosomes. This shows that ribosomes are not only essential in healthy cells, but can also be used as drug targets.

VII. Conclusion

In summary, animal cells do have ribosomes, which are essential protein synthesis factories in cells. Whether they are freely distributed in the cytoplasm or attached to the endoplasmic reticulum, ribosomes play a central role in protein synthesis and translation. By cooperating with other organelles, ribosomes ensure the normal function and

The evolutionary conservation of ribosomes and their key role in animal cells demonstrate their importance as a fundamental component of life. Understanding the structure and function of ribosomes is not only crucial to biological research, but also has far-reaching implications in medicine, drug development and other fields.

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