IGCSE Biology Chapter 3 Movement In and Out of Cells PDF

BY CELL :00201110983031 00201110983031 [email protected] CELL :00201110983031 00201110983031 [email protected]  1 Describe diffusion as the net movement of particles from a region of their higher concentration to a region of their lower concentratio...

BY CELL :00201110983031 00201110983031 [email protected] CELL :00201110983031 00201110983031 [email protected]  1 Describe diffusion as the net movement of particles from a region of their higher concentration to a region of their lower concentration (i.e. down a concentration gradient), as a result of their random movement 2 State that the energy for diffusion comes from Describe osmosis as the net movement of the kinetic energy of random movement of water molecules from a region of higher water molecules and ions 3 State that some substances move into and out of potential (dilute solution) to a region of lower cells by diffusion through the cell membrane water potential (concentrated solution), through 4 Describe the importance of diffusion of gases and a partially permeable membrane solutes in living organisms 8 Explain the effects on plant cells of immersing 5 Investigate the factors that influence diffusion, them in solutions of different concentrations limited to: surface area, temperature, by using the terms: turgid, turgor pressure, concentration gradient and distance. plasmolysis, flaccid 1 Describe the role of water as a solvent in 9 Explain the importance of water potential and organisms with reference to digestion, excretion osmosis in the uptake and loss of water by and transport organ Explain the importance of active transport 2 State that water diffuses through partially as a process for movement of molecules or ions permeable membranes by osmosis across membranes, including ion uptake by root 3 State that water moves into and out of cells by hairs osmosis through the cell membrane 3 State that protein carriers move molecules or 4 Investigate osmosis using materials such as dialysis tubing ions across a membrane during active transport. 5 Investigate and describe the effects on plant tissues of immersing them in solutions of different concentrations 6 State that plants are supported by the pressure of water inside the cells pressing outwards on the cell wall. Describe active transport as the movement of particles through a cell membrane from a region of lower concentration to a region of higher concentration (i.e. against a concentration CELL :00201110983031 00201110983031 [email protected]  MOVEMENT IN AND OUT OF THE CELL 1. Diffusion The net movement of particles from a region of their higher concentration to a region of their lower concentration down a concentration gradient, as a result of their random movement. *Down and up or against concentration gradient* Down a concentration gradient means from higher concentration to lower concentration. against concentration gradient means from lower concentration to higher concentration reasons of diffusion 1- Random movement of the different molecules that provides energy for diffusion. 2- Presence of a difference in concentration of a certain substance. CELL :00201110983031 00201110983031 [email protected]  *Factors affecting the rate of diffusion: (TADS) 1. Temperature Increase in temperature increases the rate of diffusion as it increases the kinetic energy of the molecules. EX : if you hold o tube containing a substance such as ALCOHOL in your hand, rate of diffusion increases as the molecules of the substance gain heat from your hand) 2- Distance of diffusion The longer the distance the longer the time taken for diffusion and vice versa. 3-Air current If the direction of current is similar to that of diffusion, it increases the rate of diffusion and vice versa 4-Stirring It increases the rate of diffusion as it increases the kinetic energy of molecules 5-Size of molecules :(inversely proportional) when the size of molecule increases the diffusion rate increases. 6-Surface area to volume ratio: (directly proportional) when the surface area increases to volume ratio the diffusion rate increases 2. Active transport or active uptake Movement of particles in or out of a cell through the cell membrane, from a region of their lower concentration to a region of their higher concentration against a concentration gradient using energy released during respiration through a carrier protein Carrier proteins Protein found in cell membranes that force particles against their concentration gradient. Carrier proteins are specific means each type of carrier has a specific precise shape that can bind with specific particle) CELL :00201110983031 00201110983031 [email protected]  Factors affecting active uptake 1. Number of mitochondria as in the mitochondria energy is released by the process of Aerobic respiration, this energy is used in active uptake. 3. Concentration of oxygen. Increase in oxygen concentration increases the rate of aerobic respiration. 4. Number of carrier proteins in the membrane 3.OSMOSIS Net movement of water molecules from a region of higher water potential (dilute solution). to a region of lower water potential (Concentrated solution) through a partially permeable membrane. Plant cells and osmosis What will happen if a plant cell is placed in low potential of water (high concentrated solution of salt of Sugar) The cell loses water by osmosis if it loses a small amount of water The Vacuole shrinks and the cell becomes flaccid but the cell membrane remains attached to the cell wall against an inelastic cell wall) a plant cell is placed in high potential of water (e. distilled water or diluted solution.) The cell gain water by osmosis. The vacuole enlarges and the cell becomes turgid. CELL :00201110983031 00201110983031 [email protected]  The turgidity is necessary for supporting the plant ,The pressure inside the plant cell can be increased due to absorption of water without being burst as it is surrounded by a rigid cellulose cell wall. If the cell gains water it gains its turgidity once more ( reversible process). If it loses more water, the cell membrane separates away from the cell wall and the cell becomes plasmolysed. Plasmolysis It is the shrinkage of cytoplasm of a plant cell so that the cell membrane begins to tear away from the cell wall It is an irreversible condition because it damages the cell membrane when it tears away from the cell wall. Its a sensation caused by the process of osmosis. Notice Turgor pressure within cells water pressure acting against an inelastic cell wall embedded to support plant flaccid: soft and limp not firm. CELL :00201110983031 00201110983031 [email protected]  Animal cells and osmosis An animal cell is placed in higher water potential The cell gains water and bursts, therefore the pressure inside the animal cell cannot be higher than that inside the plant cell. If an animal cell is placed in lower water potential cytoplasm shrinks and the cell shrive up (It not plasmolysed as plasmolysis includes separation of the cell membrane away from the cell wall and the animal cell has no cell wall) animal cell in lower water potential (shriveled cell) animal cell in higher water potential (cell burst) CELL :00201110983031 00201110983031 [email protected]  Comparison Diffusion Osmosis 1- It is applied for movement 1.It is applied for the of any type of molecules movement of molecules of water only 2-A partially permeable 2. A partially permeable membrane not always membrane must be always involved involved Paper 4 questions Explain The differences between uptake of water and uptake of minerals by the root hair cells 1- Uptake of water takes place by the process of osmosis which is a passive process does not need energy) ,while uptake of minerals takes place by the process of active uptake which is an active process (needs energy). 2- In uptake of water, the molecules of water move from regions of their higher (potential), while in uptake of minerals the molecules move from regions of their lower concentrations to regions of their higher concentrations against their concentration gradient). Notice No active transport for water or gases Water potential of a substance: It is the measure of how much water there is in it, and how easily the water molecules can move around. EX : A substance containing a lot of water has a higher water potential, while a substance containing little water has a lower water potential.. WHAT is the Importance of osmosis to plants Absorption of water by the root hair cells Prevents wilting of the plant and provides support by turgidity CELL :00201110983031 00201110983031 [email protected]  Practical work 1. If a piece of plant such as potato tuber is placed in a concentrated solution of salt or sugar its length decreases. This due to loss of water from the cell where water potential is higher to the surrounding solution where the water potential is lower. (Decrease in this represented in a negative value ex: -1, -2) 2. In the above condition if a weight is hanged to the potato tuber as in figure below the tuber becomes unable to support the weight as its cells become flaccid) 3. piece of plant such as potato tuber is placed in distilled water or a dilute solution of salt or sugar its length increases. This is because it is water from the surrounding solution where water potential is other than that of potato tissues (Increase in length is repented a positive value +1 , +2...) 4- In the above condition weight is hanged to the potato tuber as in figure below the tuber becomes able to support the weight as its cells become turgid. CELL :00201110983031 00201110983031 [email protected] 5- Salting (e. salting of, c Sugaring of food (ex-making jam) are important ways in food preservation. Explain why As most microorganisms such as bacteria and fungi cannot live in media of high concentration of salt or sugar, because such media have low water potential, as a result of this microorganism lose water by osmosis and then die 6-Plants die as a result of irrigation with sea water Sea water has high contractions of salts ex : low potential outside the plant roots so the water moves from inside the plant to outside by osmosis , so the plants wilt and die. 7- Mean average length samples The total of the samples divided by the number of samples If 50 mm of potato strips is put in the same water for the same period of , the final length is measured the result are 51,52,54 and 59 to calculate the mean add the lengths then divide the produced value by 4 In the above example how to get more reliable values. Exclude the value 59. as it seems to be anomalous and calculate the mean of the 3 values 8- Why reposting an experiment are times in important before takin conclusion ? For more reliable results as taking the average may reduced due to defect in one or more of the samples or due to personal errors In measurements. 9. How to determine glucose concentration in potato Put potato rods of the same length and obtained from the same potato in different concentrations of glucose, the concentration of glucose that result in no change in potato is equal to that in potato because at this concentration of water net movement is zero (means that the amount of water lost is equal to that gained) CELL :00201110983031 00201110983031 [email protected]