...CELL BIOLOGY AND GENETICS ASSIGNMENT TOPIC: CELL MEMBRANE [pic] INTRODUCTION Cell membranes are crucial to the life of the cell. It encloses the cell defines its boundaries, and maintains the essential difference between the cytosol and the extra cellular environment. Inside the cell the membranes of the endoplasmic reticulum, Golgi apparatus, mitochondria, and other membrane bound organelles in a eukaryotic cell maintain the characteristic differences between the contents of each organelle and the cytosol. Ion gradients across membranes, established by the activities of specialized membrane proteins, can be used to synthesize ATP to drive the transmembrane movement of selected solutes, or in nerve and muscle cells, to produce and transmit electrical signals. In all cells the plasma membrane also contains proteins that act as sensors of external signals allowing the cell to change its behavior in response to environmental cues; these protein sensors, or receptors, transfer information rather than ions or molecules across the membrane. [pic] THE STRUCTURE OF THE CELL MEMBRANE All biological membranes have a common general structure: each is a very thin film of lipid and protein molecules, held together mainly by non covalent interactions. Cell membranes are dynamic, fluid structures, and most of their molecules are able to move about in the...
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...AP October 2, 2014 In the early twentieth century, little was known about cell membranes. For years scientists looked through the microscope in search of answers. Since the discovery of many new information conducted through observations and research, they were able to understand that plasma membrane is an essential biological structure to all cells. It functions as an envelope by keeping all a cells organelles contained. It also serves as a gateway and barrier to certain foreign substance. Although plasma membrane may seem simple on the outside, it’s actually a complex structure of molecules working in coordination with each other to function properly. The cell membrane, also known as the plasma membrane, is a phospholipid bilayer, which consists of Polar, hydrophilic phospholipid heads and non-polar, hydrophobic fatty acid tails. The plasma membrane is constructed in a specific way where phospholipid tails point towards each other, away from polar substances and the polar heads are positioned in the other direction towards aqueous environments. Because of this special chemically influenced arrangement of molecules, an impermeable membrane selective to small, non-polar is formed substances. The cell’s plasma membrane also contains a diverse array of proteins amidst its phospholipid layer. Proteins are extremely important as they carry out many specialized functions for the plasma membrane. Proteins imbedded in between the phospholipid bilayer are called integral proteins...
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...Cells are the smallest form of life possible. All organisms have to consume air. Water is the building block of all life. Air is consumed, this process is referred to as respiration. In smart people talk this means an exchange of gases. Once the air is used to fuel the machine it is discarded as Carbon Dioxide. “Biologists also define respiration as the aerobic harvesting of energy from food molecules by cells. This process is called cellular respiration to distinguish it from breathing.” In everyday life we breathe, as we work harder physically like running, lifting heavy weight or any type of strenuous physical activity we require more oxygen. The air we breathe is taken in and deposited into the lungs, the lungs then distribute this air to the bloodstream to fuel the muscle cells in support of the higher demand of oxygen. The muscle cells extract energy from the protein and other valuable nutrients to generate ENERGY. This process is referred to as ATP. “Tonicity is how a cell loses or gains water from its surrounding solution. From here cells maintain the mass balance through a process called diffusion, all this means is the ability to spread out evenly in an available area. Isotonic simply means the ability to replace air, water, energy at the rate it is losing it. Hypotonic is a solution with a solute concentration less than the cell. Hypertonic is the opposite a solution with a higher solute concentration. Osmosis, the diffusion of water across a membrane...
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...The aim of this experiment is to investigate the influence of various alcohols and temperature on the permeability of beetroot cell membrane. The different types of alcohol will include ethanol, methanol, propanol, butanol and the tissue from the beetroot will be exposed different salt concentrations (0%, 5% ,10% and 20%) . The stress affecting the membrane’s permeability will be assessed by the amount of leakage of pigment caused. ‘Homeostasis the ability of the body or a cell to seek and maintain a condition of equilibrium or stability within its internal environment when dealing with external changes’ (Biology, 2014). Organelle membranes and the plasma membrane are selectively permeable, allowing water to pass through freely, but regulating the movement of solutes. The function of a cell membrane is to transport and allow certain substances into the cell, while keeping other substances out. Surrounding the cytoplasm of a cell, the cell membrane (plasma membrane) is a thin semi-permeable membrane (Bailey, 2014) consisting mostly of lipids and proteins and composed up of a phospholipid bilayer. This contributes to the selectively permeable nature of the membrane. 70% of proteins contribute to the cell membrane, allowing communication outside and inside the cell. The phospholipids arrange themselves so that hydrophobic tails are shielded from the surrounding water exposing the hydrophilic heads to the water. While small molecules and non-charged ions cross freely, big charged...
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...How substances cross the cell membrane. A cell’s membrane has many functions including forming a boundary in order to organise the contents and keep them separate from the extracellular environment. Yet in order for the cell to ‘live’ and perform its particular function, it needs to be able to take in substances and nutrients and to get rid of waste products. But with such a vast array of substances in the extracellular environment, it is a difficult task to control the influx and out-pouring of substances. There are several ways that this is accomplished and these are set out below. Cell, or plasma, membranes are formed from two layers of phospholipids which have a polar, hydrophilic head and a nonpolar, hydrophobic tail. This is known as the fluid mosaic model. It is this feature of membranes which makes them semipermeable and dictates how substances may cross them. Figure 1 shows a simplified structure of the cell membrane. Small, nonpolar molecules such as (O2), carbon dioxide (CO2) and nitrogen (N2) are able to diffuse passively across the membrane and do so down their concentration gradients or electrochemical gradients in the case of ions. However larger or charged molecules and ions require assistance of some type as they are too large or have a charge on them which prevents them crossing the hydrophobic interior of the membrane. In many cases a substance crosses the membrane with the assistance of membrane proteins, this is known as facilitated diffusion. Again...
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...Outline the roles of membranes at the surface of cells and within cells (10 marks) Both the cell surface membrane and the membranes surrounding certain organelles have the same basic structure and similar functions. There are 5 major roles of membranes including separating cell contents from the outside environment; separating cell components from cytoplasm; cell recognition and signalling; holding the components of some metabolic pathways in place and regulating the transport of materials into or out of cells. The phospholipid bilayer is the basic structural component of all biological membranes. A bilayer is formed when phospholipid molecules are completely surrounded by water. The hydrophilic (water-loving) heads stick in the water, while the hydrophobic (water-hating) fatty acid tails point towards each other in a mirror image. The formation of the tails creates a barrier to many molecules, separates the cell contents from the outside world and gives stability. Mechanical stability is supported by cholesterol in the bilayer. This steroid molecule fits between fatty acid tails and helps make the barrier more complete, so substances like water molecules and ions cannot pass easily and directly through the membrane. The structure of the membrane is called the fluid mosaic model because the membrane is fluid (the phospholipid molecules are not actually bonded) and because of the mosaic arrangement of the protein molecules. Inside the fluid mosaic model are various protein...
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...diffusing across a membrane? requires passive transport requires no energy requires active transport requires both a and b Which correctly describes the plasma membrane? fluid and nonpermeable rigid and nonpermeable fluid and partially permeable fluid and completely permeable Which component of the phospholipid bilayer is considered hydrophobic? phospholipid head phospholipid tail phospholipid head and tail none of the above Which correctly describes the fluid-mosaic model of the cell membrane? phospholipid monolayer with embedded proteins phospholipid bilayer with embedded proteins phospholipid monolayer with embedded triglycerides cholesterol bilayer with embedded proteins This process uses a carrier protein...
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...Cell membrane - forms the outer covering of the cell, and is semi-permeable. Cytoplasm - is a gel-like matrix where all the other cell organelles are suspended inside the cell. Nucleus - contains the hereditary material DNA and directs the activities of the cell. Centrioles - organize the microtubules assembly during cell division. Endoplasmic Reticulum - are a network of membranes composed of rough and smooth endoplasmic reticulum. Golgi complex - is responsible for storing, packaging of cellular products. Lysosomes - are enzyme sacs, that digest cellular wastes. Microtubules - are hollow rods, function primarily as support and shape to the cell. Mitochondria - is the site for cellular respiration and producers of energy. Ribosomes - are made of RNA and proteins, and are sites for protein synthesis. Nucleolus - is the structure within the nucleus and helps in synthesis of ribosomes. Nucleopore - is the tiny hole in the nuclear membrane, allows the movement of nucleic acids and proteins in/out of the cell Cell wall is the outermost rigid covering of the plant cell. It is a salient feature of plant cell. Cell membrane or the plasma membrane is the outer lining of the cell inside the cell wall. Cytosol or cytoplasm is the gel-like matrix inside the cell membrane which constitutes all other cell organelles. Nucleus is the control center of the cell. It is a membrane bound structure which contains the...
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...Cell Biology An Introduction to Cell Biology Membranes: Basic Structure Page [1 of 2] I hope you guys are getting the idea that membranes are important. Membranes are unbelievably important when it comes to the study of the eukaryotic cell. Everything we talk about, membranes are going to be involved. I’m trying to be gentle with this vocabulary, but there’s no way we can get around it. When I refer to things, when biologists refer to things, it’s like a classification system. You guys know the whole story of why we call things by their scientific name. Well, it’s the same thing with cell parts. There’s a vocabulary that goes with the cell, and you’re just going to have to tough it out and learn it. But you know what? It makes sense. Learn to dissect those words. Now, the plasma membrane in an animal cell, or in a plant cell, separates the cell from its exterior, but the membranes in the cell also separate the parts of the membrane in closed organelles from the environment of the cell. Well, when we talk about some of the functions of membrane, we’re going to refer to the cytosol and the cytoplasm, and let’s just get those words out of the way. The cytoplasm is what we refer to as all of the material inside of the cell between the plasma membrane and the nucleus. So, for example, you will find many organelles in the cytoplasm, and the cytoplasm has a liquid in it called the cytosol – “cyto” solution. “Cyto” means cell. So we have the cytoplasm, kind of plasma; cytosol is the...
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...Effects of Temperature on Membrane Permeability on Beta vulgaris Abstract In this experiment, we studied the effect of temperature on the cell membrane of a common garden beet Beta vulgaris. Beet roots were washed thoroughly, cut into six cylinders and then placed in separate test tubes. We placed each test tube in separate water baths at different temperatures for a specific period of time. The test tubes were then removed from the water baths and the absorbance of the solutions containing betalain pigments was recorded using a spectrophotometer . Maximum absorbance was recorded at -8°C (followed by the absorbance at 78.9 °C) indicating maximum release of pigments from the cell while minimum absorbance was recorded at 8°C. The results of the experiment were mostly consistent with the expectations and it was found that with increase in temperature the absorbance increases and so does the release of pigments from the cell. Introduction Cell is the basic structural and functional unit of life . The word cell comes from the Latin word ‘cella’ , meaning small room. Cell was first discovered by Robert Hooke as a descriptive term for the smallest living biological creature. The cell theory, developed by Schleiden and Schwann states that all cells arise from pre- existing cells by cell division , each cell acts as an elementary organism and all organisms are composed of one or more cells. On the basis of number of cells organisms can be classified as unicellular...
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...SUMMARY CBH Ex I CELLS AND ORGANELLES Cell Membrane: consist of a lipid bilayer. Hydrophobic tails are located in the interior. Transmembrane protiens are anchored to the core of the bilayer and can be removed only by detergents that disrupt the bilayer. Peripheral membrane proteins are attatched to the cell surface electrostatically and are easily removed by altering the pH. Eucaryotic cells with outer- and intra- cellular membranes ~ half the cell’s total volume -separate intracellular organelles Nucleus- double membrane-bound organelle containing chromatin. Contains the genetic blueprint for every protein in the body. Nuclear Envelope- separates and mediates transport between the nucleus and the cytoplasm and is supported by intermediate filament proteins, the lamins. Nucleolus- dense non membrane bound structure. rRNA synthesis and ribosome assembly. Ribosome-consists of 2 subunits of ribosomal RNA. Protein synthesis- formation of peptide bonds between amino acids to make polypeptide chains using messenger RNA as a template. Endoplasmic reticulum- (rER) Protein synthesis (sER)is involved in steroid synthesis and detoxification. Golgi apparatus- determines vesicle fate. Finaly assembly and glycosylation of proteins. Mitochondria – double membrane bound energy production mainly in the form of ATP Lysosomes- high acidity, killing of pathogenic organisms, and degradation of waste products. Endosomes- Peroxisomes – production of hydrogen peroxide...
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...processes and membrane functions are going to be affected by the loss of oxygen, blood glucose, and waste removal? The body needs the heart to always keep pumping, this is a vital part of the entire human body. When the heart stops cellular process is affected. All cells are burning up ATP. Carbon dioxide is building up in the cells and PH levels aren’t balanced. Glucose is needed to start the process for the glycolysis and oxygen is needed for mitochondria. Carbon dioxide is the byproduct and needs to be released. So the cells will begin to die and all transport pumps will come to a halt. Cells begin leaking, Na is leaking into cells and potassium is leaks out. The body’s cells will die if ATP cannot be sustained. C. Which Intracellular organelles have membranes included in their structure? How would the breakdown of the membranes of these structures affect the function of Joseph’s heart cells? Every intracellular organelle has membranes, with ATPase’s transferring calcium from the cytosol to the endoplasmic reticulum in cardiac muscle cells. Without the membrane the levels would just rise without channels in the membrane to regulate them causing an overload that would attack cytoskeleton. If the structure is broke down the hearts function is affected. Calcium and ATP will stop moving calcium from cytosol into ER of the heart muscle cells. The buildup of calcium causes protease to spill into the cells. The enzymes will bond inside vesicles and the plasma membrane will...
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...be tested and have results gathered from experimentation or observation, while hypotheses that cannot be tested and concluded upon are not useful. An example of a useful hypothesis is the question of whether or not cramming increases test performance when compared to consistent studying, and an example of a hypothesis that is not scientifically useful would be the question of whether God truly exists. 2. Two of the greatest unifying ideas in biology (i.e., concepts that account for and are consistent with a very large number of observations) are the Cell Theory, and the Theory of Evolution by Natural Selection. Most scientific Theories have two components: the pattern component and the process component. What are the two components of Cell Theory and of the Theory of Evolution by Natural Selection? What are the two conditions required by the process component of evolutionary theory? The pattern component of the cell theory is all organisms are comprised of...
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...Carrier Proteins and Active Membrane Transport The process by which a carrier protein transfers a solute molecule across the lipid bilayer resembles anenzyme-substrate reaction, and in many ways carriers behave like enzymes. In contrast to ordinary enzyme-substrate reactions, however, the transported solute is not covalently modified by the carrier protein, but instead is delivered unchanged to the other side of the membrane. Each type of carrier protein has one or more specific binding sites for its solute (substrate). It transfers the solute across the lipid bilayer by undergoing reversible conformational changes that alternately expose the solute-binding site first on one side of the membrane and then on the other. A schematic model of how such a carrier protein is thought to operate is shown in Figure 11-6. When the carrier is saturated (that is, when all solute-binding sites are occupied), the rate of transport is maximal. This rate, referred to as Vmax, is characteristic of the specific carrier and reflects the rate with which the carrier can flip between its two conformational states. In addition, each transporter protein has a characteristic binding constant for its solute,Km, equal to the concentration of solute when the transport rate is half its maximum value (Figure 11-7). As with enzymes, the binding of solute can be blocked specifically by either competitive inhibitors (which compete for the same binding site and may or may not be transported by the carrier) or noncompetitive...
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...Chapter 4 * Figure 4-2 * Modification of a germ cell to form a mammalian sperm. (A) The centriole produces a long flagellum at what will be the posterior end of the sperm, and the golgi apparatus forms the acrosomal vesicle at the future anterior end. The mitochondria collect around the flagellum near the base of the haploid nucleus and become incorporated into the midpiece ("neck") of the sperm. The remaining cytoplasm is jettisoned and the nucleus condenses. The size of the mature sperm has been enlarged relative to the other stages. (B) Mature bull sperm. The DNA is stained blue with DAPI, the mitochondria are stained green, and the tubulin of the flagellum is stained red. (Q Acrosome of mouse sperm, stained green by the fusion protein proacrosin-GFR * Sperm can travel in aqueous environment to reach the egg because of the flagellum * Figure 4-3 * The force for sperm propulsion is provided by dynein, a protein attached to the microtubules (see Figure 4.3B). Dynein is an ATPase, an enzyme that hydrolyzes ATP, converting the released chemical energy into mechanical energy to propel the sperm. * (Bj Interpretive diagram of the axoneme, showing the "9 + 2" arrangement of the microtubules and other flagellar components. The dynein arms contain the ATPases that provide the energy for flagellar movement. (C) Association of tubulin protofilaments into a microtubule double. One portion of the...
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