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What Are Cells And What Do They Do?
Cell Biology: A detailed Lesson
The basics of Cell Biology 101
Cells form the basis of all living tissue, and are the smallest constituents that are themselves, considered alive. Bacteria, plants and animals are composed of cells. Viruses are not composed of cells and are therefore not classified as living. Cells carry out tens of thousands of biochemical life processes, collectively referred to as metabolism.
Basic Cell Structure and Architecture
Cells can take on many sizes, shapes, tissue identities, and functional roles. Muscles, skin and internal organs are made up of cells. Cells communicate with each other in a myriad of ways to carry out all of their functional roles. The basic cell structure for most animals, consists of a phospho-lipiod bilayer (two layers) that protects the contents/interior of the cell from the external world. The phospholipid bilayer also selectively allows substances in as needed to contribute to the growth, proliferation, differentiation, and DNA mediated responses from the cell. The phospholipid bilayer is embedded with different integral and peripheral proteins that serve as receptors to mediate various interactions between: hormones, steroids, mechanical pressure, heat, and other external stimuli that may not actually enter the cell itself. Such examples are illustrative of a process known as a signal transduction cascade where external stimuil are converted to chemical signals within the cell that ultimately reaches the DNA within the cell nucleus.
Besides the phospholipid membrane and nucleus, the cell also contains many other organelles that mediate, moderate and mitigate cellular functions and responses to external stimuli. The organells include: the mitochondria, the cytoplasm, golgi bodies/apparatus, the rough and smooth endoplasmic reticulum, and the lysosome. The mitochondria process adenosine triphosphate through adding and removing phosphate groups (PO4) in a process known as phosphorylation and de-phosphorylation. The coupled phosphyrlation- de-phosphorylation process is mainly an aerobic (with oxygen) mediate process whereby the cells is able produce energy on demand from the breaking down of sugars and transporting electrons in the mitochondria.
The cytoplasm provides architectural support and protection from shock to internal cell organelles, and is typically a thick clear and jelly like substance. The cytoplasm also contains free floating ions of both positive and negative charges which provides energy via polarization for various metabolic processes. Such metabolic processes are important to keeping a cell healthy and alive. Food provides ions via catabolic processes where they are broken down and transported into various cell types for further degradation and later, anabolic (building up) processes. Muscles require ions to contract as one example. The cytoplasm also provides amino acids and proteins that are constructed at the ribosome.
The smooth and rough endoplasimic reticulum process and further modify proteins for better functionality. They also mnufacture lipids for the organelles and phospholipid membrane. The sooth endoplasmic reticulum produces protein based enzymes that detoxify the liver from harmful toxins, that are metabolites from initial metabolism. The rough endoplasmic reticulum is coverd by ribosomes churning out amino acid based proteins, and they produce acidic enzymes for the lysosomes.
Lysosomes are the digestive center of the cell and they help break down damaged substances and waste products of metabolism via hydrolase enzymes that are low in ph and this are acidic. In general it is a recycling and waste disposal function that the lysosomes carry out. Lysosomes can break down: lipids, carbohydrates, nucleic acids and proteins. Lysosomes contain around 50 different types of hydrolytic enzymes.
The nucleus contains the DNA of the cell which codes for proteins, that are polymerized from amino acids via, the genes that code for the instructions, and the ribosomal synthesis of the said amino acids to proteins within the cytoplasm.
Intermediate Cell Biological Functions: Biochemistry
The cytoplasm of the cell consists of aqueous solutions with concentrated solutes. Ions are an exampe of solutes. Such an envrionment brings rise to random waves of motion known as brownian motion, ion diffusion and attraction/repulsion that gives rise to non-random cellular motions, and hydrogen bonding as well. Ions in the brain and heart for example interact via channels and receptors through differential diffusion which gives rise to a polarized basis for heart myocardium contraction (heart muscle) and neuron communication in the brain and peripheral nervous system. The aqueous solution outside of or between cells assists immune cells in hydorgen bonding to foreign invaders known as antigens. An antigen maybe a fungus, a bacteria or virus, among other possibilities. Hydrogen bonds are electrostatic in nature and are weak bonds arising from a positive hydrogen bonded to an electro-negative oxygen or nitrogen. Water's strcuture is H-O-H (H20) and is thus, a polar molecule with what is referred to as a dipole moment. Dipole is just another way of saying it has electro positive and electri negative interactions from the Hydrogen and Oxygen. Such atomic charges can interact with other molecules like the antigens in the original example.
Adenosine triphosphate (ATP) consists of an adenine molecule (like in DNA) and 3 phosphate groups (PO4) and it is the energy absorber, carrier and releaser for the cell. ATP is indispensable for cell life processes and ulltimately all of human life and most other life as well. ATP contains a carbon based backbone. When PO4 is released from ATP adenosine diphosphate is produced (ADP) and energy is released to perform work, in what is called an exergonic reaction. When a PO4 is added to ADP ATP is reformed and potential energy is added, in what is called an endergonic reaction.