Cell Structure and Function. Introduction to the cell. Both living and non living things are composed of molecules made from chemical elements such as Carbon, Hydrogen, Oxygen, and Nitrogen. The organization of these molecules into cells is one feature that distinguishes living things from all other matter. The cell is the smallest unit of matter that can carry on all the processes of life. What is osmosis Dilute vs. Predicting osmosis Osmosis in action Remember what the cell membrane looks like Osmosis and cells Osmosis and plant cells. Type or paste a DOI name into the text box. Click Go. Your browser will take you to a Web page URL associated with that DOI name. Send questions or comments to doi. AP World History Stearns Chapter 3 Classical Civilization India. Introduction difference vs. China China focus on politicsrelated philosophies vs. India. Osmosis is the spontaneous net movement of solvent molecules through a semipermeable membrane into a region of higher solute concentration, in the direction that. State%20of%20Georgia/GAVS%20Shared/Science/Biology_CellsAndCellTransport_Shared/ActiveVSPassive.png' alt='How Is Active Transport The Same As Facilitated Diffusion Vs Active Transport' title='How Is Active Transport The Same As Facilitated Diffusion Vs Active Transport' />Every living thing, from the tiniest bacterium to the largest whale, is made of onemore cells. Before the C1. 7th, no one knew that cells existed, since they are too small to be seen with the naked eye. The invention of the microscope enabled Robert Hooke, 1. Anton van Leuwenhoek 1. Hooke to describe the cells in a thin slice of cork, which reminded him of the rooms where monks lived. The idea that all living things are made of cells was put forward in about 1. Cell Theory i. Spontaneous Generation. Cell Theory consists of three principles All living things are composed of one or more cells. Cells are the basic units of structure and function in an organism. Cells come only from the replication of existing cells. Cell diversity. Not all cells are alike. Even cells within the same organism show enormous diversity in size, shape, and internal organization. Your body contains around 1. Cell size. A few types of cells are large enough to be seen by the unaided eye. The human egg ovum is the largest cell in the body, and can just be seen without the aid of a microscope. Most cells are small for two main reasons The cells nucleus can only control a certain volume of active cytoplasm. Cells are limited in size by their surface area to volume ratio. A group of small cells has a relatively larger surface area than a single large cell of the same volume. BACKGROUND KNOWLEDGE Structure and Function of the Cell Introduction to the cell. Both living and nonliving things are composed of molecules made from chemical. Pharmaceutical Research Read articles with impact on ResearchGate, the professional network for scientists. Leaves are flat and thin. The epidermis is usually transparent epidermal cells lack chloroplasts and coated on the outer side with a waxy cuticle that prevents. This is important because the nutrients, oxygen, and other materials a cell requires must enter through it surface. As a cell grows larger at some point its surface area becomes too small to allow these materials to enter the cell quickly enough to meet the cells need. Ficks Law something you need to learn well. Rate of diffusion Surface Area x Concentration. Difference Distance Cell shape. Cells come in a variety of shapes depending on their function. Quotes. What information consumes is rather obvious it consumes the attention of its recipients. Hence a wealth of information creates a poverty of attention, and a. The Energy Storage Systems ESS Research Program is part of the Office of Electricity Delivery and Energy Reliability at DOE. The program is managed through Sandia. The neurones from your toes to your head are long and thin. Blood cells are rounded disks, so that they can flow smoothly. Internal organisation. Cells contain a variety of internal structures called organelles. An organelle is a cell component that performs a specific function in that cell. Just as the organs of a multicellular organism carry out the organisms life functions, the organellesof a cell maintain the life of the cell. There are many different cells however, there are certain features common to all cells. The entire cell is surrounded by a thin cell membrane. All membranes have the same thickness and basic structure. Organelles often have their own membranes too once again, these membranes have a similar structure. The nucleus, mitochondria and chloroplasts all have double membranes, more correctly called envelopes. Because membranes are fluid mosaics, the molecules making them up phospholipids and proteins move independently. The proteins appear to float in the phospholipids bilayer. Membranes can thus be used to transport molecules within the cell e. Proteins in the membrane can be used to transport substances across the membrane e. The proteins on the outside of cell membranes identify us as unique. Prokaryotes vs. Eukaryotes. Organisms whose cells normally contain a nucleus are called Eukaryotes those generally smaller organisms whose cells lack a nucleus and have no membrane bound organelles are known as Prokaryotes. Prokaryotes. Eukaryotes. Typical organisms. Bacteria. Protoctista, fungi, plants, animals. Typical size1 1. Type of nucleus. Nuclear body. No nucleus. Real nucleus with nuclear envelope DNA circular ccc DNA linear molecules chromosomes with histone proteins. Ribosomes. 70. S8. SCytoplasmatic structure. K 5 Video Reversal Tool 1000 Ways To Die. Very few structures. Highly structured by membranes and a cytoskeleton. Cell movement. Flagellaecilia made of flagellin. Flagellae and cilia made of tubulin. Mitochondria. None. RBCs have noneChloroplasts. None. In algae and plants. Organization. Usually single cells. Single cells, colonies, higher multicellular organisms with specialized cells. Cell division. Binary fission simple divisionMitosis normal cell replicationMeiosis gamete productionParts of the eukaryotic cell. The structures that make up a Eukaryotic cell are determined by the specific functions carried out by the cell. Thus, there is no typical Eukaryotic cell. Nevertheless, Eukaryotic cells generally have three main components A cell membrane, a nucleus, and a variety of other organelles. The cell membrane. A cell cannot survive if it is totally isolated from its environment. The cell membrane is a complex barrier separating every cell from its external environment. This Selectively Permeable membrane regulates what passes into and out of the cell. The cell membrane is a fluid mosaic of proteins floating in a phospholipid bilayer. The cell membrane functions like a gate, controlling which molecules can enter and leave the cell. The cell membrane controls which substances pass into and out of the cell. Carrier proteins in or on the membrane are specific, only allowing a small group of very similar molecules through. For instance, glucose is able to enter but glucose is not. Many molecules cannot cross at all. For this reason, the cell membrane is said to be selectively permeable. Cell membranes are made mostly of phospholipid molecules. They have only two fatty acid tails as one has been replaced by a phosphate group making the head. The head is charged and so polar the tails are not charged and so are non polar. The two ends of the phospholipid molecule have different properties in water. The phosphate head is hydrophyllic and so the head will orient itself so that it is as close as possible to water molecules. The fatty acid tails are hydrophobic and so will tend to orient themselves away from water. So, when in water, phospholipids line up on the surface with their phosphate heads sticking into the water and fatty acid tails pointing up from the surface. Cells are bathed in an aqueous environment and since the inside of a cell is also aqueous, both sides of the cell membrane are surrounded by water molecules. This causes the phospholipids of the cell membrane to form two layers, known as a phospholipid bilayer. In this, the heads face the watery fluids inside and outside the cell, whilst the fatty acid tails are sandwiched inside the bilayer. The cell membrane is constantly being formed and broken down in living cells. Cytoplasm. Everything within the cell membrane which is not the nucleus is known as the cytoplasm. Cytosol is the jelly like mixture in which the other organelles are suspended, so cytosol organelles cytoplasm. Organelles carry out specific functions within the cell. In Eukaryotic cells, most organelles are surrounded by a membrane, but in Prokaryotic cells there are no membrane bound organelles. Fluid mosaic model of cell membranes. Membranes are fluid and are rather viscous like vegetable oil. The molecules of the cell membrane are always in motion, so the phospholipids are able to drift across the membrane, changing places with their neighbour. Proteins, both in and on the membrane, form a mosaic, floating in amongst the phospholipids. Diffusion and Osmosis Difference and Comparison. Osmosis is the result of diffusion across a semipermeable membrane. If two solutions of different concentration are separated by a semipermeable membrane, then the solvent will tend to diffuse across the membrane from the less concentrated to the more concentrated solution. This process is called osmosis. At the cellular level, both processes are types of passive transport. Semipermeable membranes are very thin layers of material that allow small molecules, like oxygen, water, carbon dioxide, ammonia, glucose, amino acids, etc., to pass through. However, they do not allow larger molecules, like sucrose, protein, etc., to pass through. Process of Osmosis vs. Diffusion Diffusion occurs when the spontaneous net movement of particles or molecules spreads them from an area of high concentration to an area of low concentration through a semipermeable membrane. It is simply the statistical outcome of random motion. As time progresses, the differential gradient of concentrations between high and low will drop become increasingly shallow until the concentrations are equalized. Diffusion increases entropy randomness, decreasing Gibbs free energy, and therefore is a clear example of thermodynamics. Diffusion operates within the boundaries of the Second Law of Thermodynamics because it demonstrates natures tendency to wind down, to seek a state of less concentrated energy, as evidenced by increasing entropy. Osmosis is the process of diffusion of water across a semipermeable membrane. Water molecules are free to pass across the cell membrane in both directions, either in or out, and thus osmosis regulates hydration, the influx of nutrients and the outflow of wastes, among other processes. For example, if the medium surrounding the plant or animal cell has a higher water concentration than the cell, then the cell will gain water by osmosis. The overall result is that water enters the cell and the cell is likely to hydrate and swell. If the medium has lower concentration of water than the cell, it will lose water by osmosis as this time more water leaves the cell than enters it. Therefore the cell will shrink. If the water concentration in the medium is exactly the same then the cell will stay the same size while that concentration balance remains. In every situation, the movement of solvent is from the less concentrated hypotonic to the more concentrated hypertonic solution, which tends to reduce the difference in concentration equalization. Differences in Function While osmosis influences the distribution of nutrients and the release of metabolic waste products in animals in plants, osmosis is partially responsible for the absorption of soil water and for the elevation of the liquid to the leaves of the plant. Diffusion can occur through a cell membrane, and the membrane allows small molecules like water H2. O, oxygen O2, carbon dioxide CO2, and others to pass through easily. Hence while osmosis helps the plants in absorbing water and other liquids, diffusion helps other molecules to pass through and hence both facilitate the photosynthesis process. Both processes help plants to create energy and other important nutrients. Different Types of Osmosis and Diffusion The two types of Osmosis are. Reverse Osmosis The osmotic pressure defines at what point a differential gradient between high and low solute triggers osmosis. In reverse osmosis, increased volumetric or atmospheric pressure will push the higher solute particles past the membrane, overcoming the gap that may exist when the osmotic pressure wont allow diffusion through the membrane. This process is often used to filter water of impurities when their concentrations are too low for regular osmosis, but cleaner water is still needed, as in desalination and pharmaceutical operations. Forward Osmosis Unlike reverse osmosis, which goes from high to low concentrations, forward osmosis forces low solute particles to move to a higher solute in essence, the opposite of the normal osmotic process. Whereas reverse osmosis pushes particles, forward osmosis draws them in, resulting in cleaner water. The types of diffusion are. Surface diffusion Seen after dropping powdery substances on a liquids surface. Brownian motion The random motion observed under a microscope as particles skip, slip, and dart within a liquid. Collective diffusion The diffusion of a large number of particles within a liquid that remain intact or interacting with other particles. Osmosis The diffusion of water through a cell membrane. Effusion Happens as a gas disperses through small holes. Electron diffusion The movement of electrons resulting in electric current. Facilitated diffusion Spontaneous passive transport of ions or molecules across a cell membrane different because it happens outside the active phase of osmosis or intracellular diffusion. Knudsen diffusion A variable measure of particle interactivity within a membrane pore, related to the particles size and the length and diameter of the pore. Momentum diffusion The spread of momentum between particles mainly in liquids, influenced by the liquids viscosity higher viscosity higher momentum diffusion. Photon Diffusion Movement of photons within a material, then scattering as they bounce off of different densities within. Used in medical tests as diffuse optical imaging. Reverse Diffusion Similar to forward osmosis, with low concentration moving to high, but refers to a separation of particles, not just water. Self diffusion A coefficient measuring how much diffusion a type of particle will have when the chemical gradient is zero neutral or balanced.