2009-7-11 21:04
斯_______
細胞分二大類:
動物細胞同植物細胞
細胞係動物(例如:人,獅子,.等)同埋植物(例如:洋蔥)都會存在
簡單黎講係有生命的野都有細胞
動物細胞的特徵係:有細胞膜,細胞質,糖原,線粒體,,細胞核,呈不規則形狀,
植物細胞的特徵係:細胞膜,細胞質,大液泡,細胞核,細胞壁,澱粉粒,葉綠體,呈長方形[規則形狀]
2009-8-3 13:58
~Gloria~
there;s simple two kind of cells: animal cell and plant cell
1, animal cell
inside a animal cell, there;s
- cell membrane
- cytoplam
- nucleus
- rough endoplasmic reticulum
- smooth endoplasmic reticulum
- mitochondrion (pural:mitochondria)
- vacuole
i,cell membrane:
-thin, flexible (surround the cell)
-differentially permeable (only allow SOME substances to pass through)
~controls the movement of substance into and out if the cell
ii,cytoplasm
-jelly-like substance (consisting of water, proteins and other chemical subsrances)
-holds all the organelles (e.g. nucleus, endoplasmic reticulum, mitochondria, vacuole)
-provides place for chemical reactions to take place in the cellx
iii,nucelus
-round-shaped, bounded by the nuclear membrane
-contains DNA, the genetic material of life
-contains thread-like chromosomes: ~ carry genetic information
~ controls all activities of the cells
iv,endoplasmic reticulum (ER)
-a network of interconnected membrance-bound sacs
-forms a link between the cytoplasm and the nuclear membrane
-two types of ER: a,rough ER: with ribosomes attached to the surface
ribosomes on it are the sites of protein synthesis
b,smooth ER:without ribosomes attached to the surface
involved in the synthesis and transport of lipids
v,mitochondrion
-rod-shaped, bounded by a double membrane
(the iner member is folded into finger-loke projections)
-main site (the energy-releasing stage of respiration takes place)
vi,vacuole
-a space containing water and dissolved substances (e.g. food,enzymes)
-bounded by a differentially permeable membrane
-contain/ holds useful substamces (sugar) or sometimes wastes
-most animals cells usually have only a few small or even no vacuole
2,plant cell
inside a plant cell, there;s
- cell membrance
- cell wall
- chloroplast
- cytoplasm
- vacuole
- nucleus
- rough endoplasmic reticulum
- smooth endoplasmic reticulum
- mitochondrioin
i,cell wall
-thick, rigid layer covering the cell membrane
-mainly made up of cellulose
-fully permeable
-protects, supports and gives shape to plant cells
ii, large central vacuole
-contains cell sap (a solution of dissolced substances e.g. food,pigment,wastes)
-usually large, located at the centre of the cell
-when it;s full of water, the cell become turgid:provide support to the plant
iii,chloroplast
-bounded by a double membrane
-contains a green pigment----chlorophyll:absorbs light energy for photosynthesis
i types these by myself
not from internet
hope this can help you ;)