Cell Biology Fundamentals: Cycle, Control, and Structure
Cell Cycle: Growth, Replication, and Division
The cell cycle is an ordered sequence of events enabling a cell to grow, replicate its DNA, and divide into two genetically identical daughter cells, ensuring accurate genetic transmission. It comprises interphase (G1, S, G2 phases) and the mitotic (M) phase (mitosis and cytokinesis).
- G1 Phase: The cell grows metabolically, synthesizing proteins and organelles while assessing environmental conditions at the restriction point before committing to division.
Mechanisms of Biological Gas Exchange
Gas Exchange Fundamentals
Gas exchange is the process where an organism takes in oxygen and eliminates carbon dioxide. Oxygen is essential for respiration and must reach every cell. Carbon dioxide is a waste product of respiration that must be removed from the body. Gas exchange occurs via diffusion across a gas exchange surface. Oxygen diffuses from air or water, either into the blood for transport to the cells or directly into the cells. Carbon dioxide diffuses from the cells or the blood back
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Cell Theory and Microscope Technology
1. Can cells appear spontaneously without genetic material from a previous cell?
No, cells do not appear spontaneously; they pass copies of their genetic material on to their daughter cells.
2. Compare and contrast a TEM and SEM.
In a TEM (Transmission Electron Microscope), electrons are transmitted through a specimen to a fluorescent screen. An SEM (Scanning Electron Microscope) is a modification that directs electrons over the surface of the specimen, producing
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Biological Molecules: Lipids and Their Functions
Lipids are organic molecules that are insoluble in water, with an oily, waxy, or fatty consistency. Their functions are to store energy, to participate in muscle contraction, to act as insulators, and to make up part of the cell membranes. There are three kinds of lipids:
- Fatty acids and waxes: These are only made up of carbon, hydrogen, and oxygen.
- Phospholipids: These also contain phosphorus and nitrogen. They are made up of a polar head with a phosphate
V-n graph
- Which of the following statements best describes Darwin’s theory of evolution by natural selection? – Darwin’s theory emphasized that populations vary and change over time.
- Which of the following observations would provide evidence supporting Lamarck’s proposed evolutionary mechanism of “inheritance of acquired characteristics”? – A decrease in tail length in dogs after 20 generations of dogs that had their tails docked (cut off) as puppies.
- Darwin originally defined evolution as descent
Indole-3-acetic Acid (IAA): Mechanism of Cell Expansion and Plant Development
Plant cell expansion is a turgor-driven process, where water uptake into the vacuole generates internal pressure. For the cell to enlarge, its cell wall must be extensible. This is tightly regulated by hormones, especially auxin, the primary being Indole-3-acetic acid (IAA).
IAA promotes cell elongation particularly in young, growing tissues (e.g., coleoptiles, root tips) by modifying the mechanical properties of the cell wall.
Cell Wall Structure and Extensibility
The plant cell wall is a semi-rigid,
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