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CELL STRUCTURE ( 細胞的結構)

BIOLOGY. AL Teaching Notes. CELL STRUCTURE ( 細胞的結構). A. Terms. 1. Cell - the basic unit of structure and function in living organisms. 2. Cytology - the study of cells, especially by microscopy. 3. Light microscope

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CELL STRUCTURE ( 細胞的結構)

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  1. BIOLOGY AL Teaching Notes CELL STRUCTURE (細胞的結構)

  2. A. Terms • 1. Cell - the basic unit of structure • and function in living organisms. • 2. Cytology - the study of cells, • especially by microscopy. • 3. Light microscope • 4. Electron microscope

  3. Cell Structure • Cell wall (細胞壁) • Cell membrane (細胞膜) • Protoplast (原生質)- the living contents within the cell: nucleus (細胞核) and cytoplasm (細胞質)

  4. Cell membrane (細胞膜) • Chemical components :consists of 60% protein (蛋白質) , 35% phospholipid (磷脂) and 5% polysaccharides (多糖) • Two models: Unit membrane model(單位膜模型) Fluid mosaic model (流體鑲嵌模型)

  5. The Structure of Cell membrane

  6. Fluid mosaic model (流體鑲嵌模型).a three-layered ( trilaminar 三層 ) structure         - Hydrophobic tails of two layers of phospholipid molecules point inward to form a phospholipid bilayer (磷脂分子雙層) , while the protein molecules is embedded in the phospholipid bilayer (嵌於磷脂分子之間) or transmembrane (跨膜). Fluidity (流動):due to the lateral movement(橫向)of phospholipid molecules. • Mosaic(鑲嵌) : protein molecules are interspersed (散佈)among phospholipid molecules.

  7. Under electronic microscope • The upper and lower darker regions in the 3 layered image of cell membrane corresponds to the_______ molecules and __________ portions of phospholipids whereas the middle lightregion corresponds to the ____________ tails of the phospholipid bilayer.

  8. Protein molecule • The protein molecules were in form of g_________ protein which can be embedded in the phospholipid molecules or transmembrane.   • (1) membrane g___________ - as markers, recognition sites • (2) ________ proteins – transmembrane, have ________ / ionic channel that allows __ molecules and ions to pass through. They are for facilitated diffusion. • (3) ________ proteins - for facilitated diffusion • (4) membrane bound proteins - single enzyme or aggregated to form multi-enzyme complexes • to speed up chemical reactions.

  9. Function of cell membrane • (i) Compartmentalization (分室作用) • (ii) Control exchange of substances between two sides of membrane by selective / differentiate permeability (控制物質進出) • (iii)Site of membrane-bound enzyme reaction (提供酶反應的位置) • (iv) For recognition of stimuli (記認刺激), e.g insulin (胰島素) • (v)For cell identity e.g. antigen • (vi) For endocytosis (胞吞) and exocytosis (胞吐作用) • Provides electrical insulation (提供絕緣作用)

  10. How these components affect the permeability to different substances(這成分如何影響不同物質的透性) • Phospholipid bilayer allows lipid soluble molecules / non-polar molecules to diffuse more readily across membranes • (雙磷脂層讓脂溶分子 / 非極性分子易於擴散過膜)

  11. How these components affect the permeability to different substances(這成分如何影響不同物質的透性) • Hydrophobic inner zone forms a physical barrier to polar molecules which are polar / hydrophilic / ions (疏水的內層對極性的 / 親水的分子 / 離子形成物理屏障) • Channel proteins (通道蛋白 / 蛋白質形成孔道,讓離子/極性分子擴散)

  12. How these components affect the permeability to different substances(這成分如何影響不同物質的透性) • Carrier proteins / proteins bind with specific molecules and bring them to the opposite side of membrane (載體蛋白 / 蛋白質與特定分子結合,將其運至膜的另一邊) • Carrier proteins facilitate diffusion of some molecules e.g glucose (載體蛋白 將某些分子易化擴散,如葡萄糖 • Carrier proteins allow active transport of molecules (載體蛋白容許分子進行主動運輸)

  13. Nucleus (細胞核) • 1. In all eukaryotic cells , bounded by nuclear • membrane (envelope) • 2. Contains chromatin (染色質) and nucleolus (核仁) 3. DNA + histone  short and thickened chromosomes

  14. Structure of Nucleus (細胞核的構造) • Nucleolus is a conspicuous rounded structure inside the nucleus. There may be one or more in number, its function is to make ribosomes (核糖體) by combining rRNA with proteins.

  15. Function of Nucleus(細胞核的功能) • Controls all the activities and functions of the cell (所有細胞活動), cell division (細胞分裂) and carries genetic information for heredity (盛載遺傳訊息) • Stores genetic material e.g. DNA • Site of synthesis of rRNA (formation of ribosome[核糖體]) and mRNA (for protein synthesis[蛋白質製造])

  16. Nuclear membrane (核膜) • Double membrane (雙層) • Similar structure as cell membrane • Continuous with endoplasmic reticulum(E.R.) (與內質膜相連) • With nuclear pores (核膜孔) for exchange of materials between nucleus and cytoplasm

  17. Nucleoplasm • Nuclear sap • Gel-like (黏稠性液體) • Denser than cytoplasm • Contains proteins, enzymes and RNAs

  18. Chromatin (染色質) • Consists of DNA and protein ( histone, 組蛋白 ) • Condense to rod-shape chromosome (緊縮成棒狀染色體) just prior to nuclear division (核分裂前) • Carry genetic materials which determine organisms’ characteristics (特徵) and transmit these characteristics to next generations (遺傳至下一代)

  19. Nucleolus (核仁) • Composed of DNA mainly • Act as the manufacturing site of ribosomal rRNA (rRNA) and ribosomes (核糖體)

  20. Ribosomes (核糖體) • Particles synthesis in nucleolus and then pass through the nuclear pores to the cytoplasm • Made of protein and rDNA • The site for protein synthesis (合成蛋白質的地點) • Made of two subunits (亞基) • Non-membrane bound

  21. Endoplasmic Reticulum ( E.R.)(內質網) • Membrane-bound structure (膜包圍) • A system of parallel flattened membrane-bounded sacs (扁平片狀囊) called cisternae (瀦泡 / 池) • Continuous with the outer membrane of the nuclear envelope • Act as an intracellular transport system (胞內運輸系統) • There are two types of E.R - Rough ER (粗糙內質網) and smooth ER (平滑內質網)

  22. Rough E.R. (粗糙內質網) • Ribosomes are attached to its surface (表面附核糖體) • Transports proteins made by the ribosomes through the cisternae to smooth ER and then to Golgi appartus (高爾基體) for further modification (加工)

  23. Smooth E.R. (平滑內質網) • Without ribosomes attached to its surface • Transport lipids • Synthesis of lipids and steriod (類固醇) and glycogen metabolism (糖原的代謝)

  24. Diagram of Golgi apparatus

  25. Golgi Apparatus • Usually located near the nucleus (近細胞核) • Consists of stacks of flattened membrane bounded sacs called cisternae and many vesicles (多單層膜組成的球囊和小泡) • At one end of the stacks new cisternae are constantly formed by fusion of vesicles pinched from smooth ER; at the other end, small Golgi vesicles (泡囊) are pinched off constantly • Transport in vesicles of many cell materials, such as enzymes(酶) from ER • Involved in secretion (分泌作用)and lysosome formation (形成溶酶體)

  26. Lysosomes (溶酶體) • A spherical sac bounded by a single membrane (單膜) • Contain digestive (hydrolytic) enzymes (水解酶) • Intracellular digestion (胞內消化)of food materials eg. Amoeba (變形蟲) • Destroy the worn-out organelles inside cell (分解衰老的細胞器) • For self-destruction of cells in developmental process (自體溶解)

  27. Mitochondrion (線粒體) • Surrounded by an envelope of two membranes(兩層膜), the inner being folded to form cristae (嵴/脊膜/脊) • Contains a matrix (基質) with respiratory enzymes for the Krebs cycle (克雷伯氏循環) • Rich in cell which require large amount of energy such as sperm (精子), muscle cell (肌肉細胞) cristae matrix outer membrane inner membrane

  28. Mitochondion • The cristae increase the surface area (表面積) for attachment of respiratory enzymes, in form of spherical stalked particles (球形有柄小體), • In aerobic respiration, cristae are the sites of oxidative phosporylation (氧化磷酸化作用) and electron transport (電子傳遞鏈)

  29. Function of Mitochondrion • Act as power house of a cell (site of respiration) (進行呼吸作用的地點) • The energy releasing reactions of respiration occur in matrix and on the cristae

  30. Centrioles (中心粒) • Adjacent to nucleus, outside nuclear membrane • Internal structure of a centriole is similar to that of basal body of a cilium (纖毛), with 9 micotubules (微管) • Forming the spindle fibres (紡錘絲) and microtubules during nuclear division to control the separation of chromosome (染色體分離)

  31. Microtubule (微管) • Act as cytoskeleton (細胞骨架) which support the cell (支持細胞) • Involves in the movement of substances inside the cell (物質運動) • Forming the spindle fibres which involve in the separation of chromatids and chromosome

  32. Cell wall (細胞壁) • Only found in plant cells • Rigid and rather permeable (通透) • Made of cellulose (纖維素) • Usually modified by lignin (木質素) • with pores which are penetrated by plasmodesmata (胞間連絲)

  33. Function of Cell wall • Provides mechanical support and protection of the cell • Allows a pressure potential (壓力勢/壓力潛能) to be developed which aids in support • Prevent osmotic bursting (脹破)of the cell

  34. Chloroplast (葉綠體) • Large plasmid (質粒) containing chlorophyll (葉綠素) which absorb light for photosynthesis • Bounded by two membrane (兩層膜) • Consists of chloroplast envelope, stroma (基質), lamella (薄片) and granum (基粒)

  35. Vacuole (液泡) • Absence or small in animal cells • Common and large in plant cells • The enclosing membrane is called tonoplast (液泡膜) • Contain the internal cell sap (細胞液) which is a concentrated solution consists of water, sugar, salts, fat, oils, proteins and pigment(色素)

  36. Function of Vacuole • Store various substances eg. Food and wastes • Maintenance of turgor (硬脹) for support • Contain hydrolytic enzymes (水解酶) to acts as lysosomes during life and cause autolysis (自體溶解) after death

  37. Plant Histology (組織學) • Parenchyma (薄壁組織) • Collenchyma (厚角組織) • Sclerenchyma (厚壁組織) • Xylem Tissue (木質部) • Phloem Tissue (韌皮部)

  38. Parenchyma (薄壁組織) • Plant cells with thin cell wall and living protoplasm • Roughly isodiametric(等徑) (spherical, 圓形) with intercellular spaces • Found in cortex (皮層) and pith (髓) of stems and root, mesophyll of leaves (葉肉) and packing tissues in xylem and phloem

  39. Function of Parenchyma • Act as packing tissues between more specialized tissues • Turgidity (硬脹度) of these cells can provide support (支持作用) in herbaceous plant (草本植物) • Store food (貯藏食物) • Intercellular air spaces (細胞間隙) allow gaseous exchange • Metabolically active for biochemical processes such as photosynthesis and synthesis (代謝活動較活躍可進行光合作用及合成) • Their cell walls are important pathway for the water and mineral salts through the plant (for absorption of water)

  40. Leaf epidermis (葉表皮) • Protective tissue[保護組織] (usually single layer) • Modified from parenchyma [由薄壁細胞而形成] • Elongated cell with thin cell wall [長形] • Mainly colourless (except guard cells[保衛細胞]) • Compact in arrangement without intercelluar space (排列緊密沒有細胞間隙) • Presence of stoma (氣孔) for gaseous exchange(氣體交換) • Presence of cuticle (角質層)to reduce transpiration (蒸騰作用)

  41. Collenchyma (厚角組織) • Characterized by the deposition of extra cellulose at the corners of the cells so have thickening cell wall of their corners (只在角隅處加原) • They are living cells (有生命) • Cell are capable of stretching (有彈性) • Found in regions beneath the epidermis of stem (hypodermis[下皮]) and near the vascular tissues, eg, midrib of leaves [葉的中脈] • Mechanical tissue for support (支持組織)

  42. Sclerenchyma (厚壁組織) • Plant cells with evenly thickened cell wall (均厚的細胞壁) which is usually lignified (木質化) • They are dead cells (死細胞) • Support the cells • There are two types: fibres (纖維) and Sclereids (石細胞)

  43. Fibre (纖維) • Long narrow cell shape with tapering ends (細長,兩端尖銳), wall with few pits • Found in cortex(皮層), pericycle(柱鞘), vascular tissues, surrounding vascular bundles (維管束)

  44. Sclereids (石細胞) • Short and relatively spherical in shape (圓形) • Found in almost everywhere in plant body, especially in cortex, phloem of stems and roots (根及莖的韌皮部), in fruit wall (果皮) and seed coat (種皮) • Act as main cell type for mechanical support (機械性的支持作用) and protection (保護)

  45. Xylem (木質部) • Consists of tracheary elements (tracheids[管胞], vessels[導管]), fibres (纖維) and parenchyma (薄壁細胞) • Tracheary elements are dead and empty cells (中空) for transporting water and support

  46. Tracheids (管胞) • Narrow elongated (長圓筒形) cell with finely tapering ends (兩端尖銳) , without protoplasm at maturity, with heavily lignified (木質化)and pitted secondary cell wall (次生細胞壁) • Passage of water from cell to cell is facilitated through pit-pairs which allow lateral transport of water • Act as the only water conducting elements in gymnosperms (裸子植物) and primitive vascular plant; (具有維管組織的低等植物) small amount in angiosperms (開花植物)

  47. Xylem vessel (木質導管) • Long , tubular(管狀) and hollow [中空] (end walls broken down 端壁) • Without protoplasm at maturity • Join each other at end walls to form longitudinal conducting tubes (細胞首尾相連接形成導管) • Shorter, greater in diameter than tracheids

  48. Xylem vessel • Water moves from cell to cell • Cell wall lignified (木質化) and strengthened to prevent collapse (塌陷) • More specialized for water conducting than tracheids (較管胞更專門於輸送水) • Only present in angiosperms (只出現在開花植物)

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