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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
•
4. Electron microscope
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)
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)
The Structure of Cell membrane
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.
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 light region
corresponds to the ____________ tails of
the phospholipid bilayer.
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.
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)
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)
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)
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)
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
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.
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])
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
Nucleoplasm
•
•
•
•
Nuclear sap
Gel-like (黏稠性液體)
Denser than cytoplasm
Contains proteins, enzymes and RNAs
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)
Nucleolus (核仁)
• Composed of DNA mainly
• Act as the manufacturing site of ribosomal rRNA
(rRNA) and ribosomes (核糖體)
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
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)
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)
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)
Diagram of Golgi apparatus
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)
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)
Mitochondrion (線粒體)
cristae
matrix
outer
membrane
inner membrane
• 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)
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)
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
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)
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
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)
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
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)
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)
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
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)
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
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)
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)
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)
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)
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)
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)
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
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)
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
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)
Thickening of secondary wall
•
•
•
•
Annular thickening (環狀加厚)
Spiral thickening (螺紋加厚)
Recticulate thickening (網紋加厚)
Pitted thickening (紋孔加厚)
Diagram of Phloem (韌皮部)
Phloem Tissue (韌皮部)
• Sieve tube elements (篩管分子) for conduction of
food (e.g. sucrose 蔗糖)
• Sieve tube elements are elongated cells, end walls
(端壁) are modified as sieve plates (篩板)
• Sieve tube elements have no nucleus, tonoplast,
decrease in number of ER and ribosomes, with
thin layer cytoplasm to facilitate the translocation
of food (輸導作用)
Sieve Tube Element (篩管分子)
• Located on the end walls(端壁) called sieve plates
(篩板)
• Connected by sieve plates with each other to form
sieve tube (篩管)
• Present in angiosperms (有花植物)
• With companion cell (伴細胞) to help metabolic
activities (代謝活動) of the sieve tube element
and translocation of food (輪導作用)
Short assignment:
Discuss the structural adaptations
of xylem and phloem to their
functions
Blood cell (血細胞)
• Is a specialized connective tissue for
transportation of materials and body
defence (身體防衛)
• include fluid medium (plasma 血漿 55%)
and cellular constituents (red blood
cells/erythrocytes [紅血球], white blood
cells/leucocytes [白血球],
platelets/thrombocytes [血小板])
Neurones (神經元)
• Including cell body (細胞體) and nerve
fibres (神經纖維)
• located in C.N.S (中樞神經系統)
• cell body is stellate in shape
• nerve fibres are protoplasmic extensions (原
生質的伸延) of cell body, including
dendrons (樹突) and axon (軸突)
Skeletal muscle
• Innervated by the voluntary part of nervous
system
• contraction is neurogenic required nervous
stimulation
• contract and fatigue rapidly
• attached to the skeleton
• long, cylindrical with tapering or rounded
ends
Functions of skeleton muscle
• for the maintenance of posture
• for locomotion and movements of body
parts
Nerve
• a group of nerve fibres bound together by
connective tissues lying outside C.N.S
• including sensory nerve, motor nerve and
mixed nerve