An electron carrier is a molecule that accepts an electron from one molecule and transports it into another, this movement of electrons by carriers is known as the electron transport chain. Carriers can exist in either an oxidized or reduced form, in an oxidized form the carrier is available to receive additional electrons, in a reduced form the carrier is actively carrying electrons. Although there are many different electron carrier, the two most common within a human body are NADH and FAD. NADH is the reduced form of NAD⁺ that has accepted two electrons and a hydrogen ion, furthermore, FAD is the reduced form of FADH2 that has accepted two electrons and a hydrogen ion. These electron carriers are essential in cellular respiration where they harvest electrons from glucose to produce vital ATP, redox reactions during cellular respiration add or remove electrons from the electron carriers. Cellular respiration generally occurs in three processes but can vary depending on environment and the type of cell, these processes are glycolysis, the citric acid cycle, and oxidative phosphorylation. In glycolysis, the six-carbon molecule glucose undergoes a range of chemical transformations, the electron carrier NAD⁺ is reduced by accepts two electrons and a hydrogen ion producing NADH.  Additionally, two molecules of pyruvate, a three-carbon organic molecule, and ATP is produced. The pyruvate molecules then enter the mitochondria where they are processed into acetyl CoA, NADH is also produced while Co₂ is released. The processes then continue into the citric acid cycle, acetyl CoA is processed with a four-carbon molecule to produce ATP, NADH, and FADH₂. Additionally, the four-carbon molecule is regenerated to be used again and CO₂ is released. The final process of oxidative phosphorylation is now initiated, NADH and FADH₂ place their electrons into the electron transport chain to become oxidized. With these electrons, the electron transport chain expels protons from the matrix to create an electrical gradient. Protons reenter the matrix with the assistance of an enzyme called ATP synthase and produce ATP, during this process the majority of ATP produced in cellular respiration is made. With the process of cellular respiration explained, it’s easy to see how vital electron carriers are in the production of ATP.

References:

https://www.khanacademy.org/test-prep/mcat/biomolecules/overview-metabolism/v/electron-carrier-molecules

Fermentation is one of the most common pathways for anaerobic cellular respiration to occur, cellular respiration is the process in which a fuel, usually glucose, is processed through an electron transport chain to produce ATP. Fermentation is similar to many other cellular respiration pathways in the fact that it begins with glycolysis producing NADH and pyruvate. Due to a lack of oxygen, the electron transport chain in unable to function inhibiting the NADH to revert back into NAD⁺, without NAD⁺ the cycle of glycolysis cannot repeat. Additionally, pyruvate is unable to proceed through oxidization and the citric acid cycle, because of this one or two additional processes that are capable to occur in an anaerobic environment are then added. These processes are similar in the fact that they allow the NADH to drop of its electrons onto the organic molecule pyruvate or a molecule formed from the pyruvate. As there are many fermentation processes for many unique situations, the two most commonly known are lactic acid fermentation and alcohol fermentation.  Lactic acid fermentation is carried out by muscle cells when the necessary oxygen needed or the cells normal aerobic processes is absent, usually during exercise. Alcohol fermentation is used to produce the ethanol in alcoholic beverages, the NADH donates its electron into a molecule called acetaldehyde, which intern creates the ethanol. This occurs in a two-step process in which a carboxyl group is removed from the pyruvate, producing the two molecules of acetaldehyde, later the NADH donates its electron onto acetaldehyde, regenerating NAD⁺ and producing ethanol. Fermentation is not efficient in producing ATP, but without it producing ATP in abnormal conditions with a lack of oxygen would be impossible.

References:

https://www.khanacademy.org/science/biology/cellular-respiration-and-fermentation/variations-on-cellular-respiration/a/fermentation-and-anaerobic-respiration

DNA sequencing is determining the order of nucleotides within sample of DNA, these nucleotides are adenine, guanine, cytosine, and thymine. Modern technology has allowed the sequencing of the entire human genome, this allows scientist to determine whether or not a person id predisposed to a genetic condition. Additionally, this allows for prescription medication to be tailor maid for a specific genome in a specific patient. DNA is can be sequenced through a method called Sanger sequencing, but this method is older and much simpler than next-generation sequencing. In Sanger sequencing, the DNA sample is combined within a tube with a primer, DNA polymerase, and DNA nucleotide with some that are dye labeled. This mixture is heated and cooled to denaturize the DNA sample, then the DNA primer and polymerase begin to sequence an additional strand, this continues until a dideoxy nucleotide is added. This process is repeated many times until the entire sample has been sequenced, then the sample runs through a process known as capillary gel electrophoresis. This process produces an image that can be read by scientists and enables then to be able to accurately determine the nucleotide sequence. Sanger sequencing was the original method of sequencing DNA but as technology has improved Next-generation sequencing has enabled scientist to sequence massive amounts of DNA. Next-generation sequencing is the term used for the most modern sequencing methods available, there are many next-generation methods but they all are all similar in their characteristics. In Next-generation sequencing many sequencing reactions occur at the same time, the reactions are on a micro scale very quickly and are extremely cost efficient. These reactions generally only sequence a section 50-700 nucleotide at a time, but since these reactions are highly parallel, a massive number of nucleotides can be sequences quickly

references:

https://www.khanacademy.org/science/biology/biotech-dna-technology/dna-sequencing-pcr-electrophoresis/a/dna-sequencing

Animal cells contain 7 different types of organelles that regulate and perform the function of each cell. The first organelle is the nucleolus, the nucleus is where all the genetic information is stored. The nucleus regulates the entire cell by holding the instructions of what is to be done and when. The second organelle is the mitochondrion, this organelle is where the energy is produced to maintain the cell. The third organelle is the smooth endoplasmic reticulum, this is where the cell produces lysosomes and detoxifies necessary fluids. The forth organelle is the rough endoplasmic reticulum or RER, here is where proteins are synthesized that are intended to leave the cell. The fifth organelle is the Golgi apparatus, this organelle modified the proteins produced within the RER and exports them outside the cell. The sixth organelle are the peroxisome, peroxisomes contain oxidative enzymes which destroy unwanted lipids. The final organelle are the lysosomes, lysosomes deconstruct proteins for reuse, additionally, they destroy unwanted proteins to protect the cell. Each organelle has a specific function that is vital for the cell to remain alive, they depend on each other and without them life as biologist know it wouldn’t be possible.

References:

https://www.khanacademy.org/test-prep/mcat/cells/eukaryotic-cells/a/organelles-article

Speciation is the term used by biologist for how new species evolve from an origin species. A species is a group of animals that can interbreed and produce viable offspring, species can split into two by means of allopatric and sympatric speciation. First, allopatric speciation occurs when the two groups are geographically isolated from each other. The two species gradually change their genetic make-up through a process known as genetic divergence, this process is due to natural selection and the forces of genetic drift. Secondly, sympatric speciation occurs when two subgroups of a species evolve into two different species without a geographical barrier. The two species must become reproducibly isolated from each other, this commonly occurs in species that are polyploidy. Species that aren’t polyploidy can still under go this type of speciation if the subgroups of the population use different habitats or resources within the geographical area. The subgroups will adapt to what is needed most through natural selection, over a long period of time the genetic make-up of the two subgroups will change drastically. Speciation fully occurs when, regardless if the subgroups are separated by resources or habitat, the two groups would not be able to interbreed.

References:

https://www.khanacademy.org/science/biology/her/tree-of-life/a/species-speciation

Meiosis is the form of cell division that a diploid cell undergoes to create two haploid daughter cells. In the human body this process is used to produce gametes such as sperm, it is organized into two steps called meiosis 1 and meiosis 2. In meiosis 1 the cell undergoes the 4 steps of mitosis; prophase, metaphase, anaphase, telophase, with small differences applied. In prophase, the chromosomes begin to condense while aligning with their specific homologue partner. The chromosomes trade genetic information in a process call crossing over, after crossing the mitotic spindle begins to form, capturing the chromosomes in preparation of metaphase. Now in metaphase, the homologue pairs are aligned at the metaphase plate in a random orientation. As the cell progresses into anaphase, the pairs are pulled apart to opposite sides of the cell, the chromatids remain together unlike in mitosis. Finally, in telophase the chromosomes have been fully separated and a nuclear membrane develops, forming two new nuclei. Cytokinesis is completed and two new daughter cells have been formed. In some cells the formation of the nuclear membrane is skipped if it is intended for the cells to undergo another round of division. The resulting cells from meiosis 1 are all haploid, but they still contain two sister chromatids. As meiosis progresses into meiosis 2, the 2 daughter cells undergo a simplified version of meiosis 1 to create 4 cells daughter cells. Once all 4 steps have been completed, the 4 daughter cells will only contain chromosomes with one chromatid. It is this process that allows for sexual reproduction to exist, the single chromatids are able to connect with one another to form complete chromosome containing genetic information from two sources.

References:

https://www.khanacademy.org/science/biology/cellular-molecular-biology/meiosis/a/phases-of-meiosis

As a cell progress into its life cycle and exits interphase, it enters mitosis and will completely divide into two genetically identical daughter cells. Mitosis is organized into 4 stages known as prophase, metaphase, anaphase, and telophase, with an addition final process known as cytokinesis.  In the early stages of prophase, the chromosomes within the cell begin to condense, the mitotic spindle begins to form, and the nucleolus disappears. Later on, during prophase, sometimes known as prometaphase, the chromosomes fully compact, the nuclear envelope breaks down releasing the chromosomes, and the mitotic spindle continues to grow while some microtubules begin to latch onto chromosomes. The cell progresses into metaphase, where the microtubules finish latching onto all the of chromosomes and aligning them at the center of the cell in preparation of anaphase. During anaphase, the chromosomes are pulled to opposite sides of the cell by microtubules, forming new chromosomes.  When the cell enters telophase, the mitotic spindle is broken down and two nuclei form with the new chromosomes, which are beginning to return into their original uncompacted form. Although the cell has now almost completely divided, two daughter cells will not be formed until cytokinesis occurs. Cytokinesis may begin during anaphase or telophase depending on the cell, the cell is pinched between the two nuclei and the cytoplasm is divided into two new daughter cells. Now that two daughter cells have been formed, mitosis is complete and the cells will continue on into next stage in the cell life cycle.

References:

https://www.khanacademy.org/science/biology/cellular-molecular-biology/mitosis/a/phases-of-mitosis

As cells live and die they move through steps in a process which is known as the cell cycle. A cells life consists of a period of growth in which DNA will be replicated, followed by the cells division into two daughter cells. The first is called interphase which includes G₁ phase, S Phase, and G₂ while, the second phase is called mitotic or M phase, which includes Mitosis and cytokinesis. Once a new daughter cell has been formed it immediately enters G₁ phase, in this phase the cell grows larger and organizes it organelles for later stages. In the second stage called S phase, the cell forms a new copy of its genetic material and its centrosome. Finally, the cell enters G₂ phase, the cell continues to grow, forming proteins and organelles until it enters mitosis. Once these 3 phases, collectively known as interphase, are completed the cell enters mitosis or M phase. When mitosis begins the DNA within the nucleus condenses into chromosomes and is pulled apart into two individual sets on opposite sides of the cell. This process is divided into known as prophase, metaphase, anaphase, and telophase. The final step is cytokinesis, this is where the cytoplasm of the cell is split into two and the two daughter cells have been fully formed ready to begin the cycle again. Different cells replicate at different rates, some cells will never replicate. Cells that don’t replicate frequently will spend a variating amount of time performing their function before entering G₁ phase, this period of time is known as G₀ phase. With this being said, a cell cycle can range from 9 hours to up to 24 hours, each different type of cell spends an appropriate amount of time in each phase.

References:

https://www.khanacademy.org/science/biology/cellular-molecular-biology/mitosis/a/cell-cycle-phases

When biologists classify life at a high level, life is determined to be either Eukaryotic or Prokaryotic. While eukaryotes compose all multicellular organisms such as animals, plants and fungi, prokaryotes are single cell organisms such as bacteria and archaea. The largest differentiator between eukaryotes and prokaryotes is the structure of its cellular components. Eukaryotic cells contain membrane bound organelles such as Mitochondria, a Golgi apparatus, and most importantly; a Nucleus. Due to the fact that eukaryotes don’t contain a nucleus, the genetic information contained in eukaryotic cells is bundled up in a corner of the cell forming a nucleolus. The DNA in prokaryotic cells exists as only one long circular strand while eukaryotic DNA exists in many separate strands. Even though both types of cells contain ribosomes, the ribosomes are noticeably larger in eukaryotes. The membrane on eukaryotes is composed of phospholipids while protein-sugars form the membrane in prokaryotes. Additionally, eukaryotic cells are generally larger and more complex than simple prokaryotic cells. Although some eukaryotic life such as a plant cell forms a cell wall, all prokaryotic cells form a cell wall that is vastly more complex. Eukaryotic cells contain a cytoskeleton and divide through the process of mitoses, prokaryotes lack a cytoskeleton and divide through binary fusion. Eukaryotic and prokaryotic cells differ greatly but together they decide how life is organized.

References:

http://www.diffen.com/difference/Eukaryotic_Cell_vs_Prokaryotic_Cell

Lipids are one of the 4 biological macromolecules defined as being non-polar with an inability to be easily dissolved in water, they are mainly used for cell signaling, the storage of energy, and as structural components of cell membranes. Although lipids are organized into a wide range of subcategories, many of these subcategories contain only a slight change in characteristics from the 3 main categories of lipids; triglycerides, phospholipids, and steroids. Triglycerides are composed of a glycerol molecule with three fatty acid molecules attached to it, their biological purpose is to store energy efficiently. A Triglyceride will be saturated if there is only a single bond between the carbons in the hydrocarbon chain and unsaturated if a double bond is present. Saturated triglycerides tend to be solids at room temperature and are obtained primary through dairy products such as creams, cheeses, butters, and fatty meats. Unsaturated triglycerides tend to be liquids at room temperature and are generally found in plant foods such as nuts and seeds. Triglycerides consumed are stored in specialized fat cells called adipocytes forming adipose tissue throughout the body; this tissue is how the body efficiently stores energy for later use. Another main category of lipids are phospholipids, they are composed of two fatty acid molecule tails attached to a head composed of a glycerol molecule attached to a phosphate group. Phospholipids are amphipathic with a hydrophilic head and a hydrophobic tail, this is vital in its function. Phospholipids placed in water naturally arrange themselves into a sphere-shaped bilayer called a micelle with their hydrophilic heads facing the water and their hydrophobic tails facing inward. This characteristic allows phospholipids to perform its main biological function of forming the plasma phospholipid bilayer membrane incasing cells. Phospholipids allow the cell membrane to be semi permeable and extremely fluid. The final category of lipids are steroids, they are composed of four linked carbon rings with a possible tail and –OH group. Although steroids don’t resemble other lipid structures, they are considered lipids due to the fact that they are hydrophobic. Steroids are chemical messengers such as Testosterone, Estrogen, Adrenalin, and cortisol, which are transported through the blood stream to regulate essential body processes. Lipids unique characteristics allow it to play vital roles in biology and without lipids life on earth as biologists understand it today would not be possible.

References:

https://www.khanacademy.org/science/biology/macromolecules/lipids/a/lipids