Category: Cell

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A polyribosome or polysome is the attachment of many ribosomes to an mRNA during translation or protein synthesis. Under the microscope, polyribosomes are visualized as “beads” on a “thread”. It is formed during the elongation phase of the translation. Polysomes are formed both in prokaryotes and eukaryotes.

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Pancytopenia is a hematologic condition that arises due to a decrease in the number of red blood cells (RBCs), white blood cells (WBCs), and platelets. pancytopenia is a common feature observed in patients having chemotherapy and other treatment that affects the bone marrow.

The person with pancytopenia shows a decrease in RBCs number (anemia), a decrease in WBCs number (leukopenia), and a decrease in platelets number (thrombocytopenia).

Treatment of pancytopenia includes medication to stimulate the production of cells in bone marrow, blood transfusion and bone marrow transplantation.

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Acetocarmine or Carmine is a bright red color dye. The dye is basic in nature. Carmine is produced from carminic acid that isolated from the insect Coccus cacti . The dye is used in the cytology for the staining of chromosomes. For the staining of chromosomes, the carmine solution (1%) in acetic acid (45%) is used.

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During prophase I of meiosis I, the pairing of two homologous chromosomes is called the synapsis. Synapsis occurs due to the lengthwise pairing of homologous chromosomes with the help of a protein complex. The protein complex that connects the homologous chromosomes is called the synaptonemal complex.

Synapsis allows chromatid arms to exchange chromosomal segments by the process known as crossing over and helps in genetic recombination in the gametes.

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The junction between the axon of one neuron and the dendrite of the next is called the synapse. The synapse is formed by the pre-synaptic neuron and the postsynaptic neuron. The minute space present between two neurons is called the synaptic cleft.

The pre-and post-synaptic neurons communicate through chemical messenger called the neurotransmitters.

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The endoplasmic reticulum is a cell organelle found both in plant and animal cells. The endoplasmic reticulum is of two types based on the basis of presence or absence of ribosomes on its surface. The endoplasmic reticulum having ribosomes on its surface is called the rough endoplasmic reticulum (RER) and the endoplasmic reticulum without ribosomes on its surface is called the smooth endoplasmic reticulum (SER).

The SER is mainly involved in the synthesis of lipids and cholesterol. The SER is present in a high percentage in cells that synthesize lipids such as sebaceous glands, testes, and ovaries.

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Eukaryotic organelles such as mitochondria and quantasomes possess the oxysomes and the quantasomes respectively.

The oxysomes are small round bodies present in the inner folding of the inner mitochondrial membrane (cristae). These small particles are also known as F-1, F-0 particles, or the Fernandez Moran particles. They play important role in the electron transport chain and ATP production.

Quantasomes are protein and lipid-containing particles present in the chloroplasts and are play an important role in photosynthesis and are considered as the unit of photosynthesis.

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Chaperones are a group of proteins that help in protein folding inside of the cell during normal physiological and stress conditions. The main function of chaperone protein is to prevent the aggregation of both newly synthesized polypeptide chains and protein subunits. Upon aggregation, a newly synthesized protein will form nonfunctional structures.

The main examples of chaperones are heat shock proteins (hsps) found in bacteria and archaea. The two main families of hsps are hsp70 (70-kDa heat shock protein) and hsp60 (60-kDa heat shock protein). The hsp70 binds to the short sequence of hydrophobic amino acids that appear after a new polypeptide chain is synthesized. On the other hand, the hsp60 (chaperonines) act later in the folding process and help hsp70 in protein folding.

In eukaryotes, the chaperons are found in the endoplasmic reticulum, the site of protein synthesis. Examples of eukaryotic chaperons are GRP78/BiP, GRP94, GRP170.

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Metaphase is a stage of mitotic or meiotic cell division in the eukaryote. It comes after the prophase. During the “Growth” phase of the cell cycle or in the resting phase the chromosomes are present inside the nucleus. Each chromosome appears as a thread. Therefore, individual chromosomes are unable to observe in the nucleus.

However, during metaphase, the chromosomes are very much condensed (less condensed than the anaphase stage) and visible inside the cell. During metaphase, chromosomes align in the center of the dividing cell and each chromosome becomes distinguishable from the other. Thus, the best phase to study the chromosome is metaphase. Karyotyping is a procedure used to observe chromosomal abnormalities using metaphasic chromosomes.

The proteins help in the condensation of chromosomes during cell division are “Condensins”. In eukaryotes, condensins are of two types. They are known as condensin I and condensin II.

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An epithelial cell attach to its adjacent epithelial cell by Desmosomes. Desmosomes are intercellular junctions found in epithelial as well as cardiac muscle cells and provide strong adhesion between two adjacent cells. Desmosomes are also known as macula adherens. They are mostly localized in the plasma membrane of the cells.

Desmosomes are mainly comprised of desmosome-intermediate filament complexes (DIFC). The DIFC is composed of cadherin, linker proteins, and intermediate filaments. The desmosomal cadherins are comprised of two subtypes of proteins called desmogleins and desmocollins. They are calcium (Ca2+) dependent cell adhesion molecules. They provide a platform where the intermediate filaments of the cells are attached and provide mechanical support to the cells.

Desmosomes are discovered by Italian pathologist Giulio Bizzozero in the spinous layer of the epidermis. Therefore, desmosomes are also known as “nodes of Bizzozero,” In 1920, the term desmosome was introduced by Josef Schaffer.