Mitosis and Meiosis: A Detailed Comparison
Mitosis and Meiosis: A Comparison
In both mitosis and meiosis, chromosomes are duplicated only once, in the preceding interphase. Mitosis involves one division of the nucleus, accompanied by cytokinesis, producing two diploid cells. Meiosis involves two nuclear and cytoplasmic divisions, producing four haploid cells. All events specific to meiosis occur during meiosis I. Homologous chromosomes pair up to form duplicated tetrads, and crossing-over occurs. In metaphase I, the tetrads are aligned on
Read MoreHemoglobin Dissociation, Hemostasis, and EPO Factors
Hemoglobin Dissociation Curve
The oxygen-hemoglobin dissociation curve is a graphical representation of the progressive increase that occurs in the percentage of hemoglobin combined with O2 as blood O2 partial pressure (PO2) increases. This is referred to as the saturation of Hb.
Blood leaving the lungs has a PO2 of 95 mmHg and a saturation of 97%, while venous blood has a PO2 of 40 mmHg and a saturation of 75%.
Normal human blood contains 15g Hb/100ml of blood, and each gram of Hb can bind 1.34 ml
Read MoreNon-Infectious Diseases: Types, Causes, and Prevention
Non-Infectious Diseases
(Which are not communicable or contagious)
Cardiovascular Diseases
Affecting the heart and blood vessels.
- Atherosclerosis: Thickening of the artery walls due to the deposition of cholesterol, platelets, and the formation of fibrous tissue. Favors thrombus formation (blood clot that occurs in an artery or vein and leads to an obstruction that can lead to a stroke).
- Aneurysm: Narrowing of the artery wall; the artery can rupture and cause bleeding.
- Strokes: Interruption of blood supply
Cellular Structures and Active Transport Mechanisms
Active Transport
In this type of transport, substances span the membrane against the concentration gradient. Molecules bind to transport proteins and move against the gradient through the input of energy, often in the form of ATP, from the cell.
Cell Wall
Not all living things have cell walls; they are present only in eukaryotic plant cells. They form channels within the plant called plasmodesmodes. The cell wall is constituted by a middle layer (the outermost layer), which is thin and flexible, and
Read MoreCell Structure and Function
The Cell: Structure and Vital Functions
The cell is composed of three main elements: the membrane, cytoplasm, and genetic material. It performs three vital functions: nutrition, relationships, and reproduction.
The Plasma Membrane: Cell Boundary and Exchange
The plasma membrane acts as a boundary, limiting the cell’s contents while allowing the exchange of matter and energy with the surrounding environment. It consists of lipids, proteins, and carbohydrates. The plasma membrane has a fluid mosaic structure,
Read MoreRNA Synthesis: Transcription Process in Detail
The Synthesis of RNA (Transcription)
The synthesis of RNA, or transcription, occurs in the nucleus and requires:
- A DNA strand serving as a template: Of the two chains of nucleotides that make up the gene, only one, the template, is actually transcribed, while the other, called the coding strand, is not.
- Enzymes: The process is catalyzed by RNA polymerases. In prokaryotes, only one exists, whereas in eukaryotes there are three: RNA polymerase I, II, and III. RNA polymerase I is involved in the formation