Plant Cell PDF - Biology Study Guide

‫‪Plant cell‬‬ ‫املصدر‪ /‬الكتاب الجامعي‬  Plant cell ✓ In 1665, Robert Hooke looked at cork under a Cells consisting of protoplasm + cell membrane. microscope & saw multiple chambers,which he called “cells”....

‫‪Plant cell‬‬ ‫املصدر‪ /‬الكتاب الجامعي‬  Plant cell ✓ In 1665, Robert Hooke looked at cork under a Cells consisting of protoplasm + cell membrane. microscope & saw multiple chambers,which he called “cells”. Biologists IDENTIFY two basic types of cells: ✓ 1838, Schleidern & Schwann stated that cell theory: 1- Prokaryotic cells: simple , having no nuclear 1. all plants and animals are composed of cells. envelop, & found only in single-celled & some 2. cell is the most basic unit (“atom”) of life. simple, multicellular organisms & all bacteria. ✓ In 1858, Virchow stated that 2 - Eukaryotic cells: having nuclear envelop & are 3. all cells arise by reproduction from previous cells found in most higher plants , algae, , fungi, & (“Omnis cellula e cellula” in Latin). animals.  Plant cell Cell Wall: ✓ The evolution of lignified secondary cell walls ✓ A fundamental difference between plants & provided plants with the structural reinforcement animalsis that each plant cell is surrounded by rigid necessary to grow vertically above the soil. cell wall. ✓ Cell wall (common in plants & fungi) surrounds the ✓ It is rigid structure in mature cells. cell & limitsexpansion due to osmosis. ,osmosis may ✓ Composed of:- result in uncontrol able expansion of cell. 1. CELLULOSE MICRO-FIBRILS. ✓ Cell wall Encloses & protects the cell contents & 2. POLYSACCHARIDES & LIGNIN. plays a vital role in cell division & expansion. 3. SOME (GUMS, RESINS, SILICA, CALCIUM ✓ It has pits that function in communication between CARBONATE, WAXES & CUTIN). cells. ✓ Plant cells have two types of walls: ✓ In plants cell migrations are prevented because each 1. Primary cell walls: are typically thin (less than 1 μm) walled cell & its neighbor are cemented together by outer , & are characteristic of young,growing cells. a middle lamella (composed of pectin ). 2. Secondary cell walls are thicker (inner) & stronger & ✓ plant development , depends solely on patterns of are formed when most cell enlargement has ended. cell division & cell enlargement. ✓ Secondary cell walls owe their strength & toughness ✓ Bryophytes, which lack lignified cell walls, are to lignin, a brittle, glue like material. unable to grow more than a few centimeters above ✓ Symplast: is the name of continuous cytoplasm the ground. inside of cells. ✓ Plasmodesmata: thin bridge between neighbor cells.  Plant cell Plasms Membranes: ✓ Membranes composed of : ✓ Cell membrane are composed primarly of (fatty- ✓ Membranes perform many important tasks in cell acid (lipids) & proteins). metabolism: ✓ Membrane proteins are two types : 1. They divide the cell into numerous compartments. 1. Extrinsic proteins : Is loosely attached by ionic 2. They regulate the passage of molecules into & out bonds or Ca bridges to the bilayer , they can also of cells. attached to the Intrinsic proteins 3. Heat, cold, poisons, alcohol—are able to kill 2. Intrinsic proteins : are firmly embedded within because they disrupt membranes Without phospholids. membranes, life would be impossibl. ✓ Lipids are two types (phospholipids & sterols (cholesterol) ). ✓ Membrane have amphiphilic property (having dual attraction i.e containing both lipid soluble & water soluble region ). ✓ lipids as building blocks of cellular membranes. ✓ membranes actively involved in metabolism contain higher proportion of protein.  Plant cell Membranes Properties: 1. Open channels : allow ions to diffuse directly into the cell. ✓ Can grow: Membranes are formed molecule by 2. facilitators : which help solutes diffuse the lipids. molecule in certain regions of the cell. 3. pumps : which force solutes through the ✓ Membrane fusion allows the transport of materials membrane. ✓ (This exocytosis means to excrete almost anything: ✓ Particles too large are often swallowed or wastes, debris, mucilage, proteins, & disgorged whole by opening & closing of the polysaccharides.) membrane. ✓ Permeability(semi-permeable , partially permeable): ✓ CYTOPLASM& CYTOSOL : is the component of the ✓ the chemical structure of the membrane makes is cell surrounded by the membrane. flexible , the ideal boundary for rapidly growing & ✓ all organelles are present in cytoplasm. it help in dividing cells. large cellular activities such as glycolysis or nuclear ✓ Lipids soluble & some small molecules can cross division. the membrane , but other larger , water soluble ✓ The inner concentrated region of the cytoplasm is molecules & charged ions are repelled by the called endoplasm. mambrane. ✓ the outer region of cytoplasm is called ectoplasm. ✓ Transport of vital substane is carried out by clasess ✓ Cytosol (matrix of the cytoplasm ) : it surrounds the of intrinsic proteins : organelles , all metabolic reactions occur here.