Cells and Cell Structures PDF

== Again observe the leaf under the microscope. You will observe that the :al ,: isi cell contents are separated from the cell wall, i.e., space between cell wall and ctrloroplast-containing cell content (protoplasm) a: Jole is widened (Figure 26D). These changes can be explained by the fact that ou...

== Again observe the leaf under the microscope. You will observe that the :al ,: isi cell contents are separated from the cell wall, i.e., space between cell wall and ctrloroplast-containing cell content (protoplasm) a: Jole is widened (Figure 26D). These changes can be explained by the fact that outer medium is hypertonic, so water moves out leaf cells to tonop ast A *D C b Plasmolysis. A-A turgid or normal plant cell of Rheo; B - D - Successive stages in the shrinkage of cell content (protoplasm) from the cellwall' cause plamoiysis. Now place some Rfteo leaves in boiling water for a few minutes. This kills the cells of a leaf. Then mount one boiled leaf on a slide and observe it under the microscope. Put a few drops of strong solution of sugar or salt on the mounted leaf on the slide. Wait for a minute and observe it again. In this experiment, you will observe that plasmolysis does not occur. This means that the process of osmosis does not occur in boiled plant (leaf) celis. In other words, it is proved by this experiment thatproperty of selective permeabilitv exists only inthe living plasma membrane. Thus, only living cells possess selectivelv permeable plasma membrane and they are, therefore, able to absorb water bv osmosis. fable 9. Differences between cell waIl and 2" It lies outside of the ce11s 1. 2. 3. It is nonliving ancl quite thick in plant cells. 4. It is rigid. 5. It is generallr'permeable. 6. It is formed of ceilulose, hemiceifulose 3. itislivingandquitethin. 4. itisflexible. 5. Itisselectivelypermeable. 6. It is formed of lipids and proteins 1. It occurs in plant cells. It is found in both piant and animal cells. It lies on the outside of animal cells and inner to u,all in plant ce11s. ce1l and small number of srnall carbohydrates (i,e., oligosaccharides). and pectin. 7. I membrane i"o to provice pr"otection arrd strengtl-r to the cel l. its niajor"function 7. Its major function is to hold cellular contents and control passage o{ materials in and out of the celi. Nature and occurrence. -r..e nucler-rs is a iarge, centrally located spherical cellular component (Actiritr 9 Ir -s --- -.,-.--;--. :' :',,. nuclearmembranes,bothforminganuclearenvelope (Frgure27). Nuclear en\-eLL-:a.--:. --....: S'-.i.ce betr.r.een two nuclear membranes and is connected to a systen"l of membranes caLle.i r:- : l. -,-..i r-:lasntic reticulum; Figure 28). = The nuciear enle--- -: = pores (the nuclear pores 28 nucleus from the cltoplasm. The nuclear enYelope contains many -::---. :r'll'rses the liquid ground substance, the nucleoplasm. Nucleopores ::::.r'ates t}-Le The Fundomeniol Unit of Life: Cell