7.3 细菌结构
Section outline
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Does the shape matter?
::形状重要吗?It does if you're a . Prokaryotic cells are distinguished by their shape. And as you can imagine, shape may have something to do with mobility.
::如果你是... 蛋白质细胞的形状是分辨的, 并且你可以想象到, 形状可能与运动有关。Prokaryote Structure
::Prokayote 结构结构Most prokaryotic cells are much smaller than eukaryotic cells . Although they are tiny, prokaryotic cells can be distinguished by their shapes. The most common shapes are helices, spheres, and rods (see Figure ).
::大部分蛋白质细胞都比蛋白质细胞小得多。 尽管蛋白质细胞很小,但可以用其形状来区分。 最常见的形状是肝、球体和棒子(见图 ) 。Prokaryotic Cell Shapes. The three most common prokaryotic cell shapes are shown here.
::蛋白质细胞形状。 这里显示三种最常见的蛋白质细胞形状 。Plasma Membrane and Cell Wall
::等离子膜和细胞壁Like other , prokaryotic cells have a plasma membrane (see Figure ). It controls what enters and leaves the cell. It is also the site of many metabolic reactions. For example, and take place in the plasma membrane.
::与其他细胞一样,蛋白质细胞有一个等离子膜(见图 )。它控制细胞的进出,也是许多新陈代谢反应的场所。例如,在等离子膜中发生。Most also have a cell wall . It lies just outside the plasma membrane. It gives strength and rigidity to the cell. Bacteria and differ in the makeup of their cell wall. The cell wall of Bacteria contains peptidoglycan , composed of sugars and amino acids . The cell wall of most Archaea lacks peptidoglycan.
::多数也有一个细胞墙。 它就在等离子膜外。 它赋予细胞以力量和僵硬性。 细菌和细胞墙的构成不同。 细菌的细胞墙含有由糖和氨基酸构成的peptidoglycan。 大多数Archaea的细胞墙缺乏peptidogycan。Prokaryotic Cell. The main parts of a prokaryotic cell are shown in this diagram. The structure called a mesosome was once thought to be an organelle. More evidence has convinced most scientists that it is not a true cell structure at all. Instead, it seems to be an artifact of cell preparation. This is a good example of how scientific knowledge is revised as more evidence becomes available. Can you identify each of the labeled structures?
::Prokarytography 细胞。 本图中显示了一个蛋白质细胞的主要部分。 被称为中观体的结构曾经被认为是有机体。 更多的证据已经使大多数科学家相信它根本不是真正的细胞结构。 相反, 它似乎是一个细胞准备的人工制品。 这是一个很好的例子, 说明随着更多证据的出现, 科学知识是如何被修改的。 您能够辨别每个标签结构吗 ?Cytoplasm and Cell Structures
::Cytoptoplasm 和单元格结构Inside the plasma membrane of prokaryotic cells is the cytoplasm . It contains several structures, including , a cytoskeleton , and genetic material . Ribosomes are sites where are made. The cytoskeleton helps the cell keep its shape. The genetic material is usually a single loop of . There may also be small, circular pieces of DNA, called plasmids . (see Figure ). The cytoplasm may contain microcompartments as well. These are tiny structures enclosed by proteins. They contain and are involved in metabolic processes.
::蛋白质细胞的等离子膜内部是细胞图层。 它包含若干结构, 包括细胞素和遗传物质。 Riboomes 是生成细胞的场所。 细胞素帮助细胞保持其形状。 遗传物质通常是单环 。 可能还有小的、 循环的DNA, 叫做质谱( 见图 ) 。 细胞图层也可能包含微分体。 这些结构很小, 里面含有蛋白质, 它们包含并参与了代谢过程 。Prokaryotic DNA. The DNA of a prokaryotic cell is in the cytoplasm because the cell lacks a nucleus.
::蛋白质DNA 蛋白质细胞的DNA在细胞图层里 因为细胞缺乏核Extracellular Structures
::外细胞结构Many prokaryotes have an extra layer, called a capsule , outside the cell wall. The capsule protects the cell from chemicals and from drying out. It also allows the cell to stick to surfaces and to other cells. Because of this, many prokaryotes can form biofilms , like the one shown in Figure . A biofilm is a colony of prokaryotes that is stuck to a surface such as a rock or a host’s tissues . The sticky plaque that collects on your teeth between brushings is a biofilm. It consists of millions of bacteria.
::许多prokaryotes在细胞墙外有一个额外的一层,叫做胶囊。胶囊保护细胞免受化学物质和干燥。它也允许细胞粘贴在表面和其他细胞上。因此,许多prokaryotes可以形成生物胶片,如图所示。生物胶片是一个prokaryotes的聚居区,它卡在岩石或宿主组织等表面。在刷牙之间收集的粘贴板是一种生物胶片。它由数百万种细菌组成。Most prokaryotes also have long, thin protein structures called flagella (singular, flagellum ). They extend from the plasma membrane. Flagella help prokaryotes move. They spin around a fixed base, causing the cell to roll and tumble. As shown in Figure , prokaryotes may have one or more flagella.
::大多数prokaryotes也有长期的薄蛋白质结构,称为旗状(单形、旗状),它们从等离子膜延伸而来。Flagella帮助prokaryotes移动。它们绕着固定基地旋转,导致细胞滚动和滚动。如图所示,prokaryotes可能有一个或多个旗状。Bacterial Biofilm. The greatly magnified biofilm shown here was found on a medical catheter (tubing) removed from a patient’s body.
::细菌生物胶片。这里展示的放大度极大的生物胶片是在从病人身体取出的医用导管(管管)上发现的。Variations in the Flagella of Bacteria. Flagella in prokaryotes may be located at one or both ends of the cell or all around it. They help prokaryotes move toward food or away from toxins.
::细菌的旗形变异。 prokaryotes 的旗形可能位于细胞的一端或两端或四周。 它们帮助prokaryotes向食物移动或远离毒素。Endospores
::底栖Many organisms form spores for . Some prokaryotes form spores for survival. Called endospores , they form inside prokaryotic cells when they are under stress. The stress could be UV radiation , high temperatures, or harsh chemicals. Endospores enclose the DNA and help it survive under conditions that may kill the cell. Endospores are commonly found in soil and water. They may survive for long periods of time.
::许多有机体组成了螺旋。一些prokaryotes组成了生存的螺旋。被称为内栖子,当它们处于压力下时,它们会形成在蛋白质细胞中。压力可能是紫外线辐射、高温或严酷的化学物质。内栖子附上了DNA,帮助它生存在可能杀死细胞的条件下。在土壤和水中常见有内栖子。它们可能长时期生存。Summary
::摘要-
Most prokaryotic cells are much smaller than eukaryotic cells.
::大多数蛋白质细胞都比蛋白质细胞小得多。 -
Prokaryotic cells have a cell wall outside their plasma membrane.
::蛋白质细胞在等离子膜外有一个细胞墙。 -
Prokaryotic DNA consists of a single loop. Some prokaryotes also have small, circular pieces of DNA called plasmids.
::蛋白质DNA由单环组成。有些prokaryotes也有少量的圆形DNA,叫做粒子。
Review
::回顾-
Identify the three most common shapes of prokaryotic cells.
::识别三种最常见的蛋白质细胞形状。 -
Describe a typical prokaryotic cell.
::描述典型的蛋白质细胞。 -
What are the roles of flagella and endospores in prokaryotes?
::红旗和内分泌物在原虫中扮演什么角色?
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Most prokaryotic cells are much smaller than eukaryotic cells.
