Review of Biological Knowledge in Cells and Mitosis Phases

This paper will address how cells work, how cell parts function and work, and how they function together as a whole. How cells reproduce, and create identical offspring without creating cancerous cells. Different types of cells, and their purpose. Finally how genetics and heredity affect these cells.

Cell wall and Cell Membrane

The cell is complex, and made up of many different organelles and parts. The cell wall is made up of cellulose, which is only found in plants and a few other organisms similar to plants, it protects the weaker plant cell from bursting. The cell membrane which is a phospholipid bilayer, with pumps and channels, helps let in necessary nutrients and water. Small uncharged particles can simply go through the bilayer, charged or larger particles must go to protein pumps and channels which are more specific and can close. If a nutrient needs to go against the grain, from low concentration to high concentration, then a special pump named after the nutrient will be apart of the bilayer. Special pumps use ATP to transport nutrients. Osmosis is the transport of water, it can have special pumps, or go through the bi-layer, according to non-AP biology standards, osmosis can not occur in active (low to high) transport.

Cytoplasm and Mitochondria

The cytoplasm is the background of the cell, it covers the area inside the bilayer that isn’t another organelle. During protein synthesis and cellular respiration, movement and steps occur in the cytoplasm with mRNA going to ribosomes, and Cellular respiration starting, then heading to the mitochondria. If no oxygen is present after glycolysis, the 2 atp are used, and lactic acid fermentation occurs, where leftover materials are used up, this is the burning sensation you feel when working out. The mitochondria is where the second and third steps of cellular respiration occurs, Krebs cycle begins with Pyruvate, made in the first step which creates a collection of chemical energy. The electron transport chain uses oxygen to create water 34 ATP and citric acid.

Chloroplast and Vacuole

The chloroplast is found in plants, and other autotrophic organisms, the main point of the mitochondria is to convert light energy into chemical energy. Chlorophyll is inside the chloroplast, and captures the light energy, it then converts it into sugar for the organism to use. The chemical equation for Photosynthesis is carbon dioxide, water, and light energy are combined, and the cell Creates sugar and oxygen. CO2 + H2O + EL = C6H12O6. Light independent reactions are more focused on conserving water, than not using light, and partly occur in any plant. Water is split, and hydrogen is used, while oxygen is released. The vacuole is used for storage of water, nutrients, or waste, it is formed with the cell, or can be formed in a few organisms by creating a hole around nutrients.

Nucleus and Ribosomes

The Nucleus stores genetic information, it houses all DNA which would not survive outside, it is a membrane bound organelle that lets mRNA out through pores. When a new protein needs to be created, the DNA double helix will begin to be unwound, and split, mRNA copies the DNA because it can traverse the cell. mRNA leaves the nucleus through its pores, and heads to the ribosome to continue protein synthesis. A varying range of ribosomes can be found in certain cells. Ribosomes are where the second half of protein synthesis occurs, mRNA is translated to tRNA which can be read by the Ribosome. Each group of three letters creates a codon, when read by the Ribosome, a codon creates a specific type of amino acid, and adds it to the chain. The order of the amino acids determines the shape and function of the protein.

Cell Types

The two main types of cells Prokaryotic cells are simple organisms, prokaryotic organisms include eubacteria, which contain peptidoglycan, and archaebacteria, which don’t have peptidoglycan, and live in harsh environments. Prokaryotes have DNA in an area called the nucleoid, instead of a nucleus. Eukaryotic cells are much more complex, and are believed to have evolved from prokaryotic cells that absorbed other prokaryotic cells, and those cells worked together. Eukaryotes have membrane bound organelles, such as the nucleus, and are made up of of many organelles.

Types of Eukaryotic Cells

The four types of eukaryotic cells are animal, plant, protist, and fungus. Fungus and Protist cells are usually unicellular. All moving unicellular eukaryotes move with a flagella, which is a tail like structure, reproduce both sexually and asexually, and all functions such as cellular respiration, circulation reproduction, excretion, and so on. Animal cells and plant cells are similar, and have similar organelles, animal cells are generally smaller because of smaller vacuoles. The major difference is that plant cells have a chloroplast, and cell wall, while animal cells do not.

Somatic vs Sex Cells

Somatic cells are cells found normally in the human body and are commonly called diploid cells, sex cells, haploid or gametes are special because they only have one of each chromosome, and are specifically for reproduction. Animalia and plantae both have somatic and sex cells, while unicellular organisms are all diploid because they go through mitosis. Mitosis is the process of cell replication that duplicates a cell, with no intended diversity. Sex cells are made through meiosis, which is a more complicated process. Meiosis starts the same way that mitosis does, but it performs the splitting process twice, the second time chromosomes cross, and exchange information. Mitosis creates two cells with twenty-three pairs, while meiosis creates four cells with 23 non paired up chromosomes.

Stem Cells

Stem cells are cells which are either in developing humans, or specific areas of the grown human body, such as bone marrow, or the brain. Stem cells are not differentiated, and can take on any task in the environment they are in, like bone marrow cells can’t become brain cells. Humans start off in the womb as a zygote, a single celled mixture of two sex cells, egg and sperm. As a zygote, the human cell starts to perform mitosis, and duplicating. As the fetus develops, cells begin to differentiate, this happens from a signal sent from the parent by the umbilical cord which is rich in nutrients and stem cells.. In humans that are born, signals to differentiate come from the person’s mind. When the Fetus’ stem cells begin to differentiate they begin to develop systems such as respiratory and circulatory. Stem cells in fetuses have been found to not have all genes active like somatic (adult) stem cells, and the rest of their genes are paused, if needed. Gene expression appears when a cell produces certain types of proteins, or other specialized products are produced.

Cell Cycle and Reproduction

Parts of the cell cycleThe cell cycle is made up of four main parts, G1, the G used to stand for gap, but now it stands for growth thanks to scientific discovery of what occurs in the cell during G phases, S, for DNA synthesis, G2, and M, for mitosis. In G1, the cell grows, and produces protein. In S, DNA is duplicated, in G2, the cell continues to grow and produce protein, the cell will not begin to split until it has enough protein. M is the most complicated phase, it is made up of tinier phases. Prophase, where the membrane dissolves around the nucleus, and dna can survive in the cell naturally. Metaphase is when the chromatids, still paired up, line up in the center of the cell. Anaphase, when the chromatids split up into singular chromatids.

Telophase, where the chromatids go to opposite sides of the cell and cytokinesis when the cells part from each other, and reform the nuclear membrane. During meiosis the cell goes through all of the phases again, except the chromatids can exchange parts, and there are four daughter cells with only one of each chromosome instead of two.How does the cell advance to the next stage When a cell completes a phase in the cell cycle, it does a form of check, to see if it is ready to duplicate. After G1 the cell checks if the DNA is stable, it checks if there are enough resources and protein to reproduce, and if the environment is safe. G2 checks if the DNA was replicated correctly, and if all proteins are ready, there is no S checkpoint, and when the cells finishes S, it moves immediately to G2. The last checkpoint occurs after metaphase, and it checks to see if each sister chromatid has a spindle, which separates the two sister chromatids, a sister chromatid is two chromatids combined.

Mitosis vs. Meiosis

Mitosis and Meiosis are what differentiate sex cells and somatic cells. Mitosis produces diploid, somatic daughter cells while meiosis produces haploid, sex daughter cells, and includes crossing over.

During the second M phase, chromosomes swap genes, and go through the steps of Mitosis twice, except the steps happen a little differently. During meiosis, in the second phase of mitosis, the chromatids reform into sister chromatids, swapping parts and then they proceed to line up, and split, except with twenty three chromosomes in each daughter cell.

Heredity

How does the cell receive its genes? Parents combine their sex cells to create a zygote, this zygote gets one of each chromosome, and they come together to make a somatic child cell. The cells in the parents are directly from their parents, so your genetics, actually come from your grandparents. The cell then undergoes mitosis, where the genetic information is doubled, then divided in two, over and over until a baby is formed, and can become a part of the world. An example of a mendelian gene passed on in animals. Cystic fibrosis is an example of A mendelian gene, one that has a dominant and recessive trait. Cystic fibrosis is recessive, and autosomal, meaning that it is not on the twenty third chromosome. Cystic fibrosis is a gene that causes bad salt regulation, and causes your sweat to be extremely sticky, as well as various internal organs such as the lungs, people with cystic fibrosis are prone to lung infections due to a warm moist environment being provided in the lungs in the form of mucus.

Example of Incomplete Dominance

Horses are an example of incomplete dominance, when a white and black horse breed, they create a brown horse. Incomplete dominance occurs when two genes are incomplete, and mix with each other. Incomplete dominance is commonly seen in hair or skin color of many animals, human skin and hair is polygenic.

Example of Codominance

Cows are an example of Codominance when a white and red cow are bred, they create a roan cow, which has both types of fur colors. A codominant trait is where two traits both appear instead of dominant and recessive. Codominance is also commonly seen in skin color, in spotted, or multi-color animals.Example of Multiple alleleHuman blood type is an example of a multiple allelic trait and codominance. Multiple allelic traits are when there are more than two alleles for a trait. There are three alleles for blood type, A, B, and O. The codominance part comes from A and B both showing up in AB types. Other examples of multiple allelic traits would be texture of hair, and eye color in humans and cats.

Example of Polygenic Traits

Human height is an example of a polygenic trait and incomplete dominance. Polygenic traits are when multiple genes exist that affect a trait. Height has three genes, similar to skin color, and each one mixes, three tall and three short traits would create a child equal to the average height.

Types of Mutations, and How They Happen

When a gene is changed or passed down incorrectly, the person with the mutated gene will create incorrect proteins, and certain cells will not be able to function properly, unless the mutation is silent, a silent mutation still codes for the same amino acid when being translated. There are four main types of mutations, insertion is where one or more base pairs are added, a base pair refers to one bond of adenine and thymine or cytosine and guanine. Deletion is when one or more base pairs are removed. Both of these mutations cause a frameshift, which means that protein pairs will all be messed up. The fourth type of mutation is replacement, when base pairs are replaced, this can still be just as bad, or have much less effect than a frameshift. Nondisjunction is when chromatids fail to separate and cause an uneven distribution among sex cells, this can lead to three or one chromosome,which can cause diseases such as down syndrome.