outside of the cell. The opposite occurs when there is not enough of the substance inside the cell. When there is too little or excess amount of water inside the cell‚ the cell excretes or takes in the water using osmosis. The membrane is selectively permeable and able to regulate what enters and exits the cell‚ thus facilitating the transport of materials needed for survival. The movement of substances across the membrane can be passive‚ occurring without the input of cellular energy‚ or active‚ requiring
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Lipids and Phospholipids The main role of phospholipids is that they can form lipid bilayers. It is an amphipathic molecule. The head which is hydrophilic contains a group of phosphate‚ a diglyceride and a simple molecule e.g. choline. The tail is hydrophobic and is made up of fatty acids. Phospholipids receive and transmit signals across the cell membrane and act as a store room for energy. The main role of phospholipids is that they can form lipid bilayers. It is an amphipathic molecule. The
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be generated if the stimulus is large enough during the relative refractory period. The membrane potential‚ in contrast to the resting phase‚ is now -80 mV. This is the equilibrium potential for potassium; this occurs because the membrane is more permeable to potassium once again. Ion concentrations are restored in the next phase‚ which is called the undershoot. Phases 5 and 6: The Undershoot and the Return to Rest There is a small capacitive current during the undershoot‚ and potassium is leaving
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(CO2)‚ and others to pass through easily. It is said to be permeable to these molecules. Osmosis is a special case of diffusion. In this case‚ a large molecule like starch‚ is dissolved in water. The starch molecule is too large to pass through the cell membrane‚ so it cannot diffuse from one side of the membrane to the other. The water molecules can‚ and do‚ pass through the membrane. Hence‚ the membrane is said to be semi-permeable‚ since it allows some molecules to pass through but not others
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gradual change in the concentration of solutes in a solution as a function of distance through a solution. crenation A process resulting from osmosis in which red blood cells‚ in a hypertonic solution‚ undergo shrinkage and acquire differentially permeable some substances pass through freely while other do not-small uncharged molecules pass through the cell membrane following their concentration gradient diffusion movement of molecules from area of high concentration to low concentration endocytosis
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Diffusion is the molecular net movement from a higher concentration to a lower concentration. For instance‚ when a person is smoking‚ the smoke diffuses into the air. The molecules in the smoke‚ released from the cigarette‚ travel through the air. Here is how it occurs. When molecules are close enough‚ they collide with each other‚ their kinetic energy changes. Due to the direct relationship between diffusion and molecular kinetic energy‚ the molecules move away from the point of the collision as
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What is osmosis? Osmosis is the diffusion of water molecules through a semi permeable membrane. Why is it important? It is important to know what Osmosis is‚ and to understand it so that we understand what we are measuring‚ and so that we can use this understanding to apply to other situations so that we can gain further knowledge. We can also use this understanding to analyse our results. What we will do: We will put potato pieces of similar sizes in to test tubes of different concentrations
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Introduction The movement of molecules from an area of greater concentration to an area of less concentration is called Diffusion. Osmosis is the diffusion of water through a selectively permeable membrane from an area with greater concentration of water to an area with less concentration. A Hypertonic Solution is a solution of a higher concentration of solutes and a smaller concentration of water molecules than another solution. However‚ an Isotonic Solution is a solution that contains an equal
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The effects of osmosis on potatoes placed in different salt concentration Introduction: Osmosis is a movement of water across a semi-permeable membrane. This may only happen when there is a difference in concentration between the two sides of the membrane. The water moves from low concentrations to high concentrations. That is because the low concentrated area tries to dilute the opposite via osmosis. The effects osmosis has on a cell are either that it becomes turgid and hard as water enters
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molecules moving from areas of high concentration to low concentration‚ thus requiring no energy. Many of the substances that enter or leave the cell do so through diffusion. Osmosis‚ a type of diffusion‚ is the movement of water across a selectively permeable membrane. In osmosis‚ water diffuses across the area of lower solute concentration to that of higher solute concentration until the solute concentrations of the environment and the cell are equal. Tonicity‚ which is the ability of a solution to gain
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