Phases of Cell Cycle and Mitosis PDF

Phases of Cell Cycle Many of life\'s little chores such as sweeping and dusting, are quietly satisfying and rather fun washing dishes by hand, however, is never fun, which is why some clever person made the dishwasher. This handy invention soaks, washes, and rinses your dishes to a spot-free, sanit...

Phases of Cell Cycle Many of life\'s little chores such as sweeping and dusting, are quietly satisfying and rather fun washing dishes by hand, however, is never fun, which is why some clever person made the dishwasher. This handy invention soaks, washes, and rinses your dishes to a spot-free, sanitary sparkle. You unload the dishes, and the machine is ready to start the cycle all over again. A cell goes through a cycle, too. This cycle of growth, DNA synthesis, and division is essential for an organism to grow and heal. The cell cycle is the regular pattern of growth, DNA duplication, and cell division that occurs in eukaryotic cells. The four main stages: gap 1, synthesis, gap 2, and mitosis. Gap 1, synthesis, and gap 2 together make up what is called interphase. Checkpoint- a critical control point in the cell cycle where stop and go signals can regulate the cell cycle. The Gap I Checkpoint or the Restriction point Cell is large enough to divide and enough nutrients are available to support the daughter cell. If it receives a go signal, it will continue to cell cycle If it receives a stop signal, it will exit the cell cycle Gap O Checkpoint- a state where cells will not divide. Synthesis (S)- Synthesis means \"the combining of parts to make a whole.\" DNA is copied. There will be a new two sets of DNA Gap 2 Checkpoint Cells continue to carry out their normal functions, and additional growth occurs. Checks that DNA is undamaged with adequate cell size before it proceeds with mitosis and cell division. Mitosis (M)- It includes two processes: mitosis and cytokinesis. This is the division of the cell nucleus. During mitosis, the nuclear membrane dissolves, the duplicated DNA condenses around proteins and separates, and two new nuclei form. Lastly, cytokinesis the process that divides the cell cytoplasm. The result is two daughter cells that are genetically identical to the original cell. Parts of the Chromosomes Did you ever attend a birthday party where cute goodies were handed out? Whoever stuffed the giveaways had to make sure that each giveaway bag had the same number of small toys, candies, and stickers. In case that one child will miss a single goody, he may be raised a fuss. In this scenario, dividing DNA must work properly. The beneficiary must equally have the same set of DNA. This is a complicated task because DNA is long. But this can be done easily through the process of mitosis. Chromosomes are essential for the process of cell division and are responsible for the replication, division, and creation of daughter cells that contain correct sequences of DNA and proteins. Nucleotides- DNA is a double-stranded molecule made of four different subunits Chromosome- One long continuous thread of DNA that consists of numerous genes along with regulatory information. Your body cells have 46 chromosomes each. Histones- a group of proteins associated with the chromosomes. DNA wraps around histones at regular intervals, similar to beads on a string. Parts of the histones interact with each other, further compacting the DNA. Chromatin- loose combination of DNA and proteins Chromatid- one half of the duplicated chromosome Sister chromatids- two identical chromatids Centromere- region of the condensed chromosome that looks pinched Telomere- ends of DNA molecules  Stages of Mitosis Mitosis divides two new cells genetically identical with the parent cell. This process allows the splitting of the cell nucleus into two new sets of chromosomes. **PROPHASE** - Duplicated chromosomes condense - The nuclear envelope breaks down - Centrioles begin to move to opposite poles and spindle fibers form **METAPHASE** - Spindle fibers attach to each chromosome. - They align the chromosomes along the cell equator. **ANAPHASE** - Chromatids separate to opposite sides of the cell. - Cytokinesis usually begins in late anaphase or telophase. **TELOPHASE** - Nuclear membranes start to form, chromosomes begin to uncoil, and the spindle fibers fall apart. **CYTOKINESIS** - Cytokinesis divides cytoplasm between two daughter cells, each with a genetically identical nucleus. The cells enter interphase and begin the cycle again. mitosis - Students \| Britannica Kids \| Homework Help Stages of Meiosis Meiosis is a form of nuclear division that creates four haploid cells from one diploid cell. This process involves two rounds of cell division-meiosis I and meiosis II. Each round of cell division has four phases, which are similar to those in mitosis. It only occurs for sex cells. At the end of meiosis II. each cell (i.e., gamete) would have half the original number of chromosomes, that is, 15 chromosomes.  A similar but no identical chromosome pair an organism receives from its two parents accomplished in meiosis using a two-step division process. Homologous pairs separate during a first round of cell division, called meiosis I. Sister chromatids separate during a second round, called meiosis II. Since cell division occurs twice during meiosis, one starting cell can produce four gametes (eggs or sperm).In each round of division, cells go through four stages: prophase, metaphase, anaphase, and telophase. Do you know someone with a twin or do you have some family members that are twins? Below is an example of the process of meiosis and its role in having a twin. Monozygotic twins are the other term for identical twins. These occur when a single sperm meets the single egg and will eventually multiply and divide, splitting it into two individuals. Its opposite is called the fraternal twins. These are the result of the fertilization of two different eggs that can produce different looks and gender. Application of Mitosis and Meiosis/ Disorders in Cell Cycle Have you ever watched a movie in which people play with the elements of nature? They might bring back dinosaurs or make a newfangled robot. And have you noticed that these movies are always scary? That\'s because things go out of control. The robots take over, or the dinosaurs start eating humans. If cell growth goes out of control in your body, the result can be even scarier. Cancer is uncontrolled cell growth and results from many factors that affect the cell cycle. So how does your body regulate all the millions of cell divisions happening in your body? Chromosomes are the compacted strands of DNA. Body cells have two sets of chromosomes received from the parent. Meiosis is responsible for creating sex cells. Human cells have 46 chromosomes. These came from the union of a sperm with 23 chromosomes and an egg cell with 23 chromosomes also. When the zygote is formed, a new cell with 46 chromosomes is produced. Sexual reproduction produces a diverse population. This is a result of the process called meiosis. Sex cells have unique combinations of chromosomes. No egg cells or sperm cells are identical. Sibling with the same parent is not identical to one another. This enables organisms to continue to reproduce through the generations. The unsuccessful process of the cell cycle might cause cancer cells. Normal body cells have a number of important features. They can: - reproduce when and where it\'s needed - stick together in the right place in the body - self-destruct when they become damaged or too old - become specialized (mature) Cancer cells are different from normal cells in various ways. **1. Cancer cells continue to divide** Cancer cells continue to divide until everything lumps and becomes a tumor. **2. Cancer cells ignore signals from other cells** Cancer cells deny signaling from other cells. Cells send chemical signals to each other. **3. Cancer cells don\'t stick together** Cancer cells detached with other cells. Cancer cells can lose the molecules on their surface that **4. Cancer cells do not have specialization** Cells developed to carry out their function in the body. Scientists call the process maturing differentiation. In cancer, the cells often duplicate rapidly and don\'t have a chance to mature. **5. Cancer cells do not repair** New gene faults, or mutations, can make the cancer cells grow quicker, damage other body parts and become resistant to treatment. **6. Cancer cells look different** Cancer cells look differently from normal cells. They have different sizes and some may be larger than normal while others are smaller. Cancer cells have unusual shape and the nucleus may have an abnormal appearance. What does cancer look like? Look at the picture below.  These photographs show half of a cancerous lung and half of a healthy lung. Gases diffuse across the surfaces of a healthy lung, so the membrane surfaces must be thin and moist. Exposure to substances such as tobacco smoke can cause changes in the lung cells. Cilia are destroyed, and the lung lining becomes thicker. The lungs can no longer clean themselves, so they are more susceptible to From the above picture, you can really tell how difficult this might cause a person. Imagine those who have survived cancer, they are really winners! From the suffering and treatment, things will really end up well. Now, what can you do to help yourself from not acquiring this? Follow the list below. 1\. Avoid tobacco in all its forms, including exposure to secondhand smoke. 2\. Eat properly. 3\. Make quality sleep a priority. 4\. Get enough vitamin D. 5\. If you choose to drink, limit yourself to an average of one drink a day. 6\. Exercise regularly. 7\. Stay lean. 8\. Avoid infections that contribute to cancer, including hepatitis viruses, HIV, and the human papillomavirus. 9\. Avoid unnecessary exposure to radiation 10\. Avoid exposure to industrial and environmental toxins such as asbestos fibers, benzene, aromatic amines, and polychlorinated biphenyls (PCBs) (Harvard School of Public Health). Structural Components of Cell Membrane Think about how the products you buy are packaged-----a pint of tomatoes, or a tube of toothpaste. The tomatoes are probably in a plastic container that has holes to allow air circulation. The toothpaste is in a tube strong enough to be squeezed without ripping. Both containers protect their contents, but they do so in different ways. Like these products, the cell needs protection, but it must also be able to respond to its surroundings. It is constantly taking in and getting rid of various molecules. The structure of the cell membrane allows it to perform all those functions. The plasma membrane is composed of a unit membrane, a two-layered structure with proteins on the outer surfaces and hydrophobic (water insoluble) fat molecules on the inside. All membranes in the cell are made of the same basic structure. This is called the unit membrane and consists of two main chemicals: proteins (glycoproteins, etc.) and lipids (glycolipids, etc.). The main lipid components of plasma membranes are phospholipids- molecules composed of glycerol, phosphate, and fatty acid residues- and heads with different chemical properties. The tails are hydrophobic (water insoluble) fatty acid residues that face the center of the membrane. The heads, which are hydrophilic (water soluble), form the surface. The plasma membrane is semipermeable. It lets small molecules like water pass very easily but holds back larger solute molecules like proteins. Water can diffuse through a semipermeable membrane almost as if it were not there. Water always moves from areas of high concentration to areas of low concentration. If two areas are separated by a semipermeable membrane and there is a higher concentration of water on one side, water moves through to equalize the concentration on both sides. Cell membrane is like a faculty room. Teachers need to be undisturbed in order to do paper work and preparations for the class. The solution so that teachers can do their tasks efficiently is to separate their rooms from the classroom. The walls keep the faculty room protected from outside disturbances. But teachers are not fenced in the faculty room forever. Doors allow people to come and go when transactions are needed to be done with the teachers. Doors in the faculty room are like the cell membrane in the cells. Cell membrane is a selectively permeable membrane that filters things that enter and exit the cell. The same scenario with the faculty room, it cannot allow unimportant people to enter. They also select. The fluid mosaic model describes the plasma membrane structure as a mosaic of phospholipids, cholesterol, proteins, and carbohydrates. Passive Transport If you have ever been jammed in traffic behind a truck full of pigs, you know that \"unpleasant\"fails to fully describe the situation. That is because molecules travel from the pigs to receptors in your nose, which your brain infers as a really bad odor. Or perhaps you have tie-dyed a T-shirt and have seen dye molecules spread throughout the pot of water, turning it neon green or electric blue. Why does that happen? Why don\'t the molecules stay in one place? Passive transport is the movement of molecules across a cell membrane without energy input from the cell. It may also be described as the diffusion of molecules across a membrane. Passive transport is like swimming in the direction of water flow in a river. Here, you have to face the current in order to reach the end or the opposite side of the river bank. You are one of the substances that meet other substances found in the river. The substances move from region of higher concentration to the region of lower concentration What will you do when someone sprays a perfume inside your room or even in the house? Basically you would react and say if it\'s pleasing or not. But how did it happened? This is because the perfume particles diffuse in the air. Diffusion is the movement of molecules in a fluid or gas from a region of higher concentration to a region of lower concentration. Water molecules, of course, also diffuse. How about when you sit in the bathtub or submerge our fingers in water for a while? What happened? Your hands become wrinkly, right? And that is too because of osmosis. The skin of our fingers absorb water and get expanded or bloated, leading to the pruned or wrinkled fingers. Movement across a semipermeable membrane from an area of higher water concentration to an area of lower water concentration is called osmosis. The transport of oxygen in the blood and muscles is another example of facilitated diffusion. In blood, hemoglobin is the carrier protein whereas in muscles, the carrier protein in the myoglobin. The diffusion of blood occurs as a result of higher pressure on one side of the membrane and a lower one on the other side. Facilitated diffusion is the diffusion of molecules across a membrane through transport proteins. The word facilitate means \"to make it easier.\" Transport proteins make it easier for molecules to enter or exit a cell. But the process is still a form of passive transport. Osmosis If you have ever been stuck in traffic behind a truck full of pigs, you know that \"unpleasant\" fails to fully describe the situation. That is because molecules travel from the pigs to receptors in your nose,which your brain interprets as a really bad odor. Or perhaps you have tie-dyed a T-shirt and have seen dye molecules spread throughout the pot of water, turning it neon green or electric blue. Why does that happen? Why don\'t the molecules stay in one place? EXPLORE Osmosis is the diffusion of water across a semipermeable membrane from an area of higher water concentration to an area of lower water concentration (Fig.1). 1\. A solution is isotonic to a cell if it has the same concentration of dissolved particles as the cell. Water molecules move into and out of the cell at an equal rate, so the cell\'s size remains constant 2\. A hypertonic solution has more solutes than a cell. Overall, more water exits a cell in hypertonic solution, causing the cell to shrivel or even die. 3\. A hypotonic solution has fewer solutes than a cell. Overall, more water enters a cell in hypotonic solution, causing the cell to expand or even burst. Source: Nowicki, S. Georgia Biology (2008) pp. 86-87 EXPLAIN Did you ever asks about how salt water fish cannot live in a fresh water and vice versa? Here\'s the reason why. Osmosis deals with chemical solutions. Solutions have two parts, a solvent and a solute. In the sea, the solute is the salt plus the other micro molecules and the solvent is the water. When solute dissolves in a solvent, the end product is called a solution. There are three different types of solutions that cells can be in: isotonic, hypotonic, and hypertonic. Different types of solutions have different impacts on cells due to osmosis. Source:https://www.scienceabc.com The environment of salt water fish is different (Figure 2). There is a high concentration of solutes in the environment around the fish. Like this environment, water moves toward the high concentrate solute solution because there is less water there. Water moves from high concentration to low concentration. The fish naturally wants to push water out of it which dehydrates them. Thus, saltwater fish drinks saltwater in order for its cells not to shrivel from dehydration which will eventually kill the fish. While the fish drinks saltwater, it is also consuming salt. The salt in the fish would make the cells want to push water out of them which will dehydrate the cells. In order to prevent this kind of scenario, fish filter out the salt and poop it in solid form, so there is not too much concentration of solutes in the fish (AP Biology,Tahomo High School, 2013). Fresh water (Figure 3) is hypotonic to the fish that salt content in their body is higher than the salt content of the water surrounding them. Due to osmosis, therefore, water continuously flows into their body (i.e., the area of high solute concentration, salt being the solute, in this case).To survive in the face of this continuous supply of water, freshwater fish have to urinate very frequently. How about the salt water fish placed in a freshwater environment, what will happen? If you put a saltwater fish into freshwater, the surrounding water would flow into their body until their cells swelled up with water, eventually killing them. Active Transport: Endocytosis and Exocytosis Active transport drives molecules across a membrane from a region of lower concentration to a region of higher concentration. This process uses transport proteins powered by chemical energy. Active Transport is like shipping something because shipping requires energy and it moves things across the surface of the earth. The same is with the cell. With active transport, the cell moves the materials across the membrane and it requires energy. Endocytosis is the process of taking liquids or fairly large molecules into a cell by engulfing them in a membrane. Endocytosis is like a GRAB taxi wherein you can get a car with a driver to drive you around the city just like a material that can get a casing from the cell membrane to take it inside the cell. Phagocytosis is a type of endocytosis in which the cell membrane engulfs large particles. The word literally means \"cell eating.\' Pinocytosis is a type of endocytosis in which the cell membrane engulfs small particles and called it as \"cell drinking® Exocytosis is the opposite of endocytosis. It is the release of substances out of a cell by the fusion of a vesicle with the membrane. Exocytosis is also like a train because the sac takes the material to the cell membrane and releases it onto the other side and that\'s as far as it will go. Likewise, with a train, it takes you where you have to go and no farther.