Chapter 12 :Transport in living organisms :2

 8) Define and explain plasmolysis.
     PLASMOLYSIS :
                   The shrinkage of protoplasm due to the loss of water is called plasmolysis.
     EXPLANATION :
                    Wilting in plants occurs as a result of plasmolysis or loss of turgidity.Artificially this process takes place when the cell is placed in concentrated solution.As a result the water of the cell sap diffuses out.The shrinkage condition is known as plasmolysis or flaccidity and the cell in which the shrinkage is taken place is called plasmolysed cell or flaccid cell.


 9) Define and explain turgidity.
     TURGIDITY :
              When a cell absorbs water,it swells and becomes turgid.This phenomenon is called turgidity.
      EXPLANATION :
               When all the cells in the leaf of a plant are turgid,the whole structure is firm and hard.
      In plants it is the turgor of their cells which keeps the stem upright.The water in side the cell at the time of turgidity increases the pressure inside.It is known as TURGOR PRESSURE.
      If the cell loses water faster than they can take in,the pressure in the vacoule falls and the cells lose their turgor gradually.The leaf becomes limp and the plant is said to be willed.


 10) Define and explain wilting with examples.
       WILTING :
                It is defined as the drooping of leaves and the great tender stems of a plant as a result of excessive evaporation as compared to the uptake of water by roots.
      EXPLANATION :
                It usually occurs in hot weather,when the rate of transpiration exceeds water absorption.The plants also wilt there is no water in the soil.During wilting the plants,especially the leaves lose their turgidity,which leads to wilting.


 11) Write a note on the transport of water and salts in unicellular and simple multicellular plants.
         TRANSPORT OF SALTS AND WATER IN UNICELLULAR AND SIMPLE MULTICELLULAR PLANTS :
               In unicellular or simple multicellular plants,the exchange of substances with the enviroment occurs by diffusion,osmosis or active transport through their general surface.


 12) Write a note on ascent of sap in flowering plants.
        ASCENT OF SAP :
                     The rising of soil water from the bottom to the top of a plant through xylem is called ascent of sap.
        EXPLANATION :
                      The flowering plants on the other hand are multicellular and complex.All of their cells are not exposed to the external enviroment.For this purpose flowering plants need a special transport system called vascular system.
      Flowering plants absorb water and salts from the soil by their roots through osmosisand active transport collectively.The path of transport from the soil to roots is root hairs,cortex,endodermis and finally xylem of the root.From the xylem it rises up to the top of the plant.


 13) Write a note on transport of food and its storage.
        TRANSPORT OF FOOD :
                   The food manufactured in the leaves of the green plant is transported in the phloem to various parts of a plant body for use or storage.The process of transport of food in the plant body is the opposite of water transport.In the transpiration stream,water and dissolved salts move from the roots to the leaves whereas the food materials travel down from the leaves towards the stem and roots.under certain conditions,the food can travel in opposite direction i.e from the root to the stem and leaves.In such situation the stored food in the roots is carried upwards for distributin to other parts of the body.
        STORAGE OF FOOD :
                        A portion of the carbohydrates made by the leaves during photosynthesis is used for growth and development of leaves.The remainder sugar and starch not used in the leaf are carried to other parts of a plant through the phloem.The underground structures,which store food,are root tubers of carrot and stem tubers of potatoes.In addition to sugar and starch,some minerals are also transported to the underground parts for storage.During spring,when the buds are sprouting,starch stored in the underground parts is again converted into sugars.The sugars and amino acids travel up the stem to supply energy and raw materials for growth of buds and shoots.These food materials are also supplied to developing seeds and fruits.
    Plants store mostly carbohydrates in their roots,stem and leaves in the form of starch.the fruits and seeds are sites for storing proteins,fats and minerals in addition to carbohydrates.During germination of the seed,the stored carbohydrates and proteins are used till the seedling starts manufacturing its own food.


 14) Define transpiration.Describe the factors effecting transpiration.
       TRANSPIRATION :
                      It is defined ass "the evaporation of water from the aerial parts of the plant mainly through stomata."
       FACTORS EFFECTING TRANSPIRATION :
                      There are several factors which effect the rate of transpiration.
   a) LIGHT :
                 Light has a direct effect on transpiration.Primarily it opens the stomata and secondly it increases the temperature.Both these factors increase the rate of transpiration.The stomata normally opens in light and closes in dark.
   b) TEMPERATURE :
                  The rate of transpiration increases with the increase in temperature.The rate of transpiration becomes approximately double for every 10 degree centigrade rise in temperature.It means that the rate of transpiration is directly proportional to the temperature upto certain limits.
  c) HUMIDITY :
                 The rate of transpiration increases with decrease in humidity of the air.It means that the rate of transpiration is inversely proportional to the atmospheric humidity.Dry and less humid air increases the rate of transpiration.
  d) WIND :
                 Moving air is called wind,which increases the rate of transpiration.Wind replaces moist air from the surroundings of leaves with dry air,which favours transpiration.
  e) SOIL MOISTURE :
               Transpiration depends on the availibility of water in the soil and its absorption by the roots.If transpiration is not accompanied by sufficient moisture available from the soil,then the plants start wilting.under such conditions the stomata get closed and the rate of transpiration decreases.

Chapter 12 :Transport in living organisms :1

1) Define transport :
    TRANSPORT : 
                           The movement of substances from one part to another part within the body of an organism is called transport.



2) How transport is done in unicellular organisms?
    TRANSPORT IN UNICELLULAR ORGANISMS :
                           In simple and unicellular living organisms there is no need of any special transport system.The oxygen and dissolved substances from the outside enviroment can diffuse into the protoplasm directly.



3)What is vascular system?
    VASCULAR SYSTEM :
                         In plants the system which is responsible for the transport of material throughout the plant body is called vascular system.Vascular system consists of Xylem and Phloem.
    XYLEM :
                   The vessels which are responsible for the transport of minerals are called xylem vessels.
    PHLOEM :
                   The vessels which are responsible for the transport of food are called phloem vessels.



4) Define passive transport and active transport.
    There are two basic processes responsible for the transport of materials across the cell membrane.They are :
     a) Passive transport        b) Active transport
     PASSIVE TRANSPORT :
                     The movement of the materials across the cell membrane without the expenditure of metabolic energy is called passive transport e.g Diffusion , Osmosis , Plasmolysis etc.
     ACTIVE TRANSPORT :
                     It is defined as the movement of substances across the cell membrane against the concentration difference with the help of energy input.



5) Describe the importance of water in the transport of materials?
    IMPORTANCE OF WATER :
                              Living organisms depend on water for their existance.
    a) MAJOR CONSTITUENT OF THE CELL :
                       The protoplasm of the cell contains 70% to 95% of water , which shows that water is the major constituent of a cell.
    b) UNIVERSAL SOLVENT :
                         Water is said to be the best solvent , capable of dissolvig many substances like sugar , salts or even proteins.This property of water is advantaceous to all living organisms in transport of materials across their cell membrane.
    c) MEDIUM OF TRANSPORT :
                         Water in plants acts as a medium of transport for minerals from roots to leaves of the plant.
    d) WATER AS A METABOLITE :
                           Water acts as a metabolite and is required in many metabolic reactions occuring in the cell.In photosynthesis it provides hydrogen to Carbondioxide for making glucose.
           In hydrolytic reactions water molecules are added to break large molecules into smaller ones.
           In condensation reactions small molecules are joined together by the removal of water molecules to form large molecules.
           Transpiration of water also regulates temperature and help in circulation of nutrients.



  6) Define and explain the process of diffusion.
      DIFFUSION :
                           The movement of molecules or ions from the region of their higher concentration to the region of their lower concentration is known as diffusion.
      EXPLANATION :
                          Diffusion play a very important role in the transport of materials across a cell membrane.water enters a cell through cell membrane and is transported from cell to cell by diffusion.The rate of diffusion depends upon the concentration difference and the nature of the path way the molecules have to take.
     a) DIFFUSION IN PLANTS :
                           Plants during photosynthesis and respiration , are entirely dependent on diffusion for exchange of carbon dioxide and oxygen between the cell and the external enviroment.In transpiration , water diffuses out from leaves through stomata , which helps in the circulation of nutrients.
    b) DIFFUSION IN ANIMALS :
                          Many small animals such as Amoeba and Hydra for obtaining oxygen and getting carbondioxide out depend on diffusion.
       In case of large animal there are special organs for respiration like Lungs , which play imporatant role in respiration and bring fresh supplies of air into body. However even in lungs the final stage in the exchange of gases between air and blood depends on diffusion.



  7) Define and explain osmosis with the help of experiment.
      OSMOSIS :
                        The diffusion of water molecules or any other solvent through semi permiable membrane is known as osmosis.
      EXPLANATION :
                         The process of osmosis play very important role in the transport of material across the cell membrane.
      The plants depend mainly on osmosis for absorption of water through their roots and its translocation from the roots to the leaves.The process of osmosis can be best explained by an experiment which is as follows.
      EXPERIMENT :
                          Take a thistle funnel and tie a piece of cellophane papaer tightly over its mouth.Fill the funnel with concentrated sugar solution.Mark the level of the solution in the funnel.Lower the funnel into a beaker of water so that the liquid levels inside and outside the funnel are the same.Set up a control experiment with distilled water.
               The level of the solution in the funnel gradually rises and then becomes steady.The reason is that the beaker contains 100% pure water , this means that the concentration of water molecules is higher in the beaker than in the sugar solution.Therefore , there is a net flow of water molecules from beaker into sugar solution , raising its level in the stem of thistle funnel.The movement of water molecules from beaker into funnel is called end-osmosis.
               The  sugar solution  exerts a downward pressure by its weight and some water is pushed outside.This movement of water from the inside to the outside is called exosmosis.Inspite of exsosmosis ,the water molecules in the beaker exert pressure on the solution inside the funnel.This pressure is known as osmotic pressure.