Prokaryotic and Eukaryotic Cells: Key Differences
Key Differences Between Prokaryotic and Eukaryotic Cells
June 07
B1OB
1. a. Prokaryotes:
- DNA is located in a Nucleoid region, not surrounded by a membrane.
- Direct cell division, mainly by binary fission.
- No centrioles and spindle microtubules.
- Sexual systems are few; if any sexual intercourse occurs, it is by transfer from a donor to a recipient.
- Few multicellular forms; absence of tissue development.
- Anaerobic, facultative, aerobic, and microaerophilic forms.
- Absence of mitochondria: enzymes for oxidation of organic molecules are linked to the membranes.
- In photosynthetic species, enzymes are bound to membranes. Photosynthesis can be aerobic or anaerobic, with end-products like sulfur, sulfate, and oxygen.
Eukaryotes:
- The nucleus is surrounded by a membrane.
- Genetic material is fragmented into chromosomes composed of DNA and proteins.
- Cell division by mitosis; spindle present, or some form of organization of microtubules.
- Frequent sexual systems. Alternation of haploid and diploid phases through Meiosis and Fertilization.
- Multicellular organisms develop tissues.
- Almost exclusively aerobic.
- Enzymes are in the mitochondria.
- The enzymes for photosynthesis are packaged in chloroplasts.
2. The bacterial cell wall is mainly composed of peptidoglycan. The composition and cell wall structure in prokaryotes depends on the species and growing conditions. The difference in the structure of the bacterial cell wall is used for classification, differentiating between them by using the Gram stain. The plant cell wall is a complex organ; apart from giving support and structure to plant tissues, it can influence the development of cells.
3. 1c, 2d, 3a, 4b
B2OA
1. Mitochondria have two membranes: a smooth outer membrane and an inner membrane whose folded invaginations are called cristae. These membranes define two different compartments: the intermembrane space and the matrix, limited by the inner membrane.
2. Cellular respiration is the most important function that this organelle triggers, obtaining energy as ATP. In cellular respiration, the molecule is oxidized in the presence of O2 to form CO2, H2O, and energy in the form of ATP. Proteins are synthesized in the ribosomes.
3. The endosymbiotic theory explains the origin of mitochondria and chloroplasts. Mitochondria appeared millions of years ago from respiring aerobic and photosynthetic bacteria that were phagocytosed by primitive eukaryotic cells and, instead of being digested, established an endosymbiotic relationship in which one cell lives inside another and they mutually benefit each other.
B3OB
1. Mitosis (MIT): Each cycle of DNA replication is followed by cell division, and each daughter cell will have the same amount of DNA and a diploid chromosome number. There is no relationship between homologous chromosomes; they behave independently. It is a short process where the genetic material remains constant, not occurring mutations or aberrations.
Meiosis (ME): Each replication is followed by two cell divisions, resulting in four haploid daughter cells that contain half the number of chromosomes as the parent cell. There is a connection between homologous chromosomes that are paired to form bivalents. It is a long process with genetic variability due to crossover.
2. e.1 Metaphase, d.2 Anaphase, c.3 Telophase, b.4 Cytokinesis, a.5 Daughter cell
3.
c. Reconstruction of the nuclei of the daughter cells: a new nuclear envelope forms around each group of separate chromosomes, chromosomes decondense, nucleoli reappear, and RNA synthesis resumes completely.
d. Simultaneous separation of each chromosome; its sister chromatids move to opposite poles of the spindle, resulting in two equal groups of separated chromosomes.
B4OB
1. 4.b, 2.a, 1.c, 3.d
2.
Active Immunity (IA): Acquired after an adaptive immune response in which the individual acquires immunological memory, i.e., the ability to rapidly generate large numbers of specific antibodies in subsequent contacts with the same antigen.
Passive Immunity (IP): Achieved when immunity-conferring antibodies come from another organism. Its action is short-lived.
3. The first line of defense is the skin and mucous membranes of the digestive, respiratory, excretory, and reproductive systems. They are physical, chemical, and biological barriers. Physical barriers include epithelia (barrier effect and sloughing effect), and chemical barriers include skin fatty acids. The second line of defense involves cells and molecules that react non-specifically; these mechanisms are in place immediately when pathogenic microorganisms breach the first line of defense.