“false feet”. Imagine a caterpillar’s tiny legs propelling it across the surface of a leaf or twig. Also known as pseudopods, these tiny appendages attach to a surface in the direction the cell is moving. During chemotaxis, pseudopods are extended in several directions, but they’ll only attach to surfaces that exhibit higher concentrations of chemical signals.
On the other hand, bacterial cells facilitate movement through flagellum. Flagellum move almost like a boat propeller, urging the cell forward.
Metabolism
Metabolism is another common characteristic of all cells. Metabolism in cells occurs through a number of chemical processes.
Cellular metabolism defines chemical changes in living cells through which a number of activities and processes are achieved. It’s a constant state of growth and destruction, which is how energy is produced and provided, as well as involves how new materials are assimilated by a structure.
These biochemical reactions inside the cell can either accelerate or decelerate the functions of a cell based on need. A number of pathways are involved in these functions. Metabolism inside cells must be carefully balanced and coordinated.
The importance of enzymes and their influence in these biochemical reactions is vital. Enzymes are protein-based catalysts or triggers that accelerate biochemical reactions. They do this by expediting rearrangement of molecules supporting cellular functions.
Enzymes are defined as flexible proteins. They can change shape when binding to substrate molecules. This binding and “shape shifting” capability is how an enzyme can influence responses or reactions inside the cell.
Specific enzymes can either activate or inhibit a molecule’s activity or function. Metabolism often occurs along metabolic pathways, which are simply defined as a coordinated process of chemical reactions that trigger a continual process from point A to point B. Enzymes are involved in every step of this reaction pathway and have the ability to transform molecules into different forms depending on the presence of certain enzymes. In such a way, these chemical processes are involved in biosynthesis or creation of new molecules. They can also be involved in catabolism or degradation of molecules.
Some enzymes are involved in physically connected metabolic pathways. Chemical reactions in cellular structures are balanced through anabolic or catabolic pathways. Synthesis of new molecules requires the input of energy to become an anabolic pathway.
The catabolic pathway triggers the breakdown of molecules and results in energy release. In this way, cells break down polymers that include polysaccharides and proteins, and in turn, sugars and amino acids.
Molecules created by organic or enzymatic activities are known as metabolites. Metabolites ensure that energy is consistently available for both anabolic and catabolic pathway balances.
This careful balance as well as maintenance of biochemical reactions of cells by enzymes is a vital component to cellular functions. Activity of enzymes enables cells to respond to ever-changing demands on their environment as well as in the regulation of metabolic pathways. Both are vital to the survival of every cell.
Cellular mitosis
Mitosis is a process that all cell life undergoes. It was first observed in 1855 by German researcher Rudolph Virchow.10 Mitosis defines division of eukaryotic nuclei, although the term is used broadly in defining cellular duplication.
Cellular division differs between eukaryotes and prokaryotes. Prokaryotes (single-celled organisms) rely on asexual reproduction, producing offspring with the same genetic makeup of the parent through binary fission.
Figure 2-10 Cellular mitosis.
Eukaryotic cells undergo mitosis or cellular division and production by manufacturing identical copies that duplicate their DNA sequences through specific phases known as the cell cycle.
Cellular mitosis is most simplistically defined as reproduction. Technically, mitosis is recognized as the division of nuclear cells in the production of two identical “daughter” cells during numerous phases (cell cycle):
•Interphase – generally defined as a ‘pre-mitosis’ preparation activity
•Prophase
•Prometaphase
•Metaphase
•Anaphase
•Telophase
•Cytokinesis
Each of these phases involved in mitosis is a vital aspect of growth and rejuvenation or replacement of older or damaged, or otherwise literally “worn out” cells.
During mitosis, the cell divides and creates identical copies of itself. The process involves a parent cell that divides and produces identical daughter cells.
This process enables the parent cell to translate or pass on its genetic coding to each daughter cell.
Before this happens, the cells duplicate their DNA, and mitosis is defined as the process through which the cell separates identical copies or duplications of its nucleus.
In many circles, Interphase is not technically defined as the first stage or phase of mitosis, but is generally further broken down into three separate yet distinct stages: G1 (first gap), S (synthesis phase), and G2 (second gap phase).
During Gap 1 stage, the cells that will divide perform a number of metabolic activities, including growth. During the synthesis phase (S. phase) the cell effectively duplicates its DNA. Each chromosome creates its own copy known as a sister chromatid. The two chromatids fuse together in the shape of a X, with the intersection known as the centromere.
During the second gap phase (G2), the cell grows and manufactures proteins necessary for mitosis.
In Prophase, some structures inside the cell dissolve, while others are formed. Chromosomes will condense and mitotic spindles start to form. The spindle is responsible for organizing chromosomes, growing as the centrosomes gradually move apart. During this phase, the nucleolus also dissolves, triggering the next stage, typically called late prophase or prometaphase. As the nuclear envelope breaks down, the chromosomes are released. At this point, some microtubules bind to patches of protein (kinetochore) on the centromere of each sister chromatid.
During metaphase, the spindle has lined up the chromosomes in the middle of the cell in preparation for actual division. At this time, chromosomes are aligned with kinetochores and attached to microtubules. This process is vital in order to ensure that the sister chromatids divide evenly between the two daughter cells. If chromosomes are not aligned properly, the cell will trigger this division process to stop until they are properly arranged.
Anaphase occurs when the sister chromatids actually separate from one another. They drift to opposite sides of the cell, each now becoming its own chromosome. Each pair of chromosomes drift to opposite sides of the cell.
This movement activity is compelled by motor proteins as defined earlier. The motor proteins literally transport chromosomes during this phase.
Telophase is the point in time when the cell is nearly finished with the division process and once again reestablishes its normal structure. The division of the
