| What are the major characteristics that plants have to differ them from animals? | Their ability to manufacture food through photosynthesis and unlimited growth in localized regions
(plants and animals do not differ at a molecular level. |
| How do plants and animal cells differ? | Presence of cell wall
absence of centrioles
presence of different types of plastids (chloroplast, chromoplast, amyloplast, leucoplast. )
presence of large central vacuole in differentiated cells that generally occupies around 90% of the cell volume, large vesicle filled with solution variety. |
| Talk about the structural organization of plants. | Some are unicellular, but most of them are multicellular organized in basis of tissues organs and systems.
plant body contains two major parts or systems : root and shoot (stems, leaves and reproductive organs- flowers and cones.) |
| What is a plant cell wall? | a strong porous rather rigid outer boundary of cells consisting of non-living structure, secreted by the living part of the cell, although it is a product of protoplasm it is not a part of it. |
| Talk about the function of cell wall. | Constitutes a kind of exoskeleton providing mechanical support and protection required for plant cells, also provides transport functions between cells through plasmodesmata, substances can freely pass through it without selectivity. |
| Talk about cell plate formation. | granules appear between daughter cells, these granules containing hemicellulose and pectin fuse together to form the cell plate which will then develop into the middle lamella (intercellular layer common to both cells, viscous nature of pectin gives the middle lamella a cement role connecting the cell walls of adjacent cells. |
| Talk about primary cell wall. | first part of the cell wall laid down against the middle lamella by the protoplast of a young growing cell . Its plastic and capable of extension as cell grows, consists of carbohydrates (90%) and hydrated proteins. |
| Talk about the constituents of primary cell wall. | cellulose lined and unbranched macromolecule of glucose linked together.
Hemicellulose a mixture of neutral polysaccharides including pentoses (xylose and arabinose) and hexose ( most frequent being galactose, mannose and glucose)
Pectin ( gel mixture consisting of acidic polysaccharides)
Small amount of glycoproteins |
| Talk about the molecular structures in primary cell wall. | Skeleton is made up from cellulose molecules linked by H-bonds to form microfibrils, which are twisted to form macrofibrils, which group to form fibers that form irregular meshwork constituting bulk of cell wall, Hemicellulose and pectin and glycoproteins form an amorphous matrix in which cellulose fibers are embedded. |
| How does primary cell wall become more rigid? | As more cellulose molecules are added after cell has reached its maturation size. |
| Where are primary cell wall mainly found? | they are the only cell walls of undifferentiated cells as well as some differentiated cells, and of cells whose growth has not been achieved yet. |
| Talk about the function of primary cell wall. | Capable of growing in length (stretching of network of microfibrils) and in width (synthesis of new constituants: microfibrils and matrix.), therefor it participates by growing to elongation of young cells which is necessary for the growth in length of plant organs. |
| Talk about secondary cell wall. | Found in parts of the plant and cells with relatively thick walls, usually of three layers (S1--S3 from out to in) produced and deposited between primary wall and plasma membrane after cell growth is over which increases in width not length. |
| Talk about the constituents of secondary cell wall. | Much thicker than primary cell wall and composed of a succession of compact layers of lamella, made of cellulosic material, fibrils lie parallel to each other and generally oriented at an angle 60 degrees to the fibrils of the next lamella, In addition they may have lignin which is a complex insoluble polymer |
| Talk about the role of secondary cell wall. | The arrangement of fibrils gives it strength unlike the primary cell wall which has irregular orientation of fibrils. In addition cells with lignin have a lot of hardness and decay resistance quality (woods), so lignin adds strength to the cell wall. |
| Where are secondary cell walls mainly present? | Devoid of living material at maturity, dead empty cells which main function is structural strength, mechanical support and protection |
| Talk about pits and plasmodesmata | There are often tiny holes within the cell walls through which various protoplasmic connections between adjacent cells may run. Called plasmodesmata which promotes material exchange through protoplasmic connections, usually located in areas called pits where the cell wall is thin and no secondary cell wall is found. |
| Talk in general about the classification of plant tissues | Differentiated tissues are derived from undifferentiated ones, called meristems, the process of transformation is called differentiation, there are different types of differentiated tissues based on their functions |
| Talk about the plant tissues of high land vascular plants. | Two major categories:
Meristems (primary and secondary)
Differentiated tissues (protective epidermis and periderm/ Ground tissues parenchyma, collenchyma and sclerenchyma/ Vascular tissues Xylem and phloem/ Secretory tissues that are plant specific) |
