细胞生物学复习题 双语版 (2)

liposome脂质体：为了进一步减少双分子层两端疏水尾部与水接触的机会，脂质分子在水中排列成双分子后形成一种自我封闭的双层球型结构。

lysosome溶酶体一层单位膜构成，囊泡状，内含多种酸性水解酶类

molecular chaperone分子伴侣是一类能够协助其它多肽进行正常折叠、组装、转运、降解的蛋白，并在DNA的复制、转录、细胞骨架功能、细胞内的信号转导等广泛的领域都发挥着重要的生理作用。

cytoskeleton细胞骨架指真核细胞之中的蛋白质纤维网架体系，对于细胞的形状、细胞的运动、细胞内物质运输、染色体的分离和细胞分裂等起重要作用。主要成分为微管、微丝和中间纤维。

MTOC微管组织中心细胞质中微管组装的起点和核心，包括中心体、基体和着丝点。对微管的形成、微管极性的确定及细胞分裂中纺锤体的形成起重要作用。

chromatin染色质是间期细胞遗传物质的存在形式，由DNA、组蛋白、非组蛋白及少量RNA 等构成的细丝状复合结构，形状不规则，弥散分布于细胞核内。

chromosome染色体是指细胞在有丝分裂或减数分裂过程中，染色质经复制后反复缠绕凝聚而成的条状或棒状结构，借以保证DNA被准确的分配到子代细胞中，对物种遗传性状稳定性的维持起到重要作用。

denuclear pore complex核孔复合体核膜上间隔分布着许多由内外两层膜局部融合形成的开口，是一个复杂的盘状结构体系，称为核孔复合体。它是沟通细胞核与细胞间物质交流的通道，对大分子物质的运输具有选择性。

nucleosome核小体是染色质的基本结构单位，由长约200bp的DNA和5种组蛋白组成，组蛋白H2A,H2B,H3,H4各2分子组成一个八聚体核心，DNA在其外表缠绕1.75圈，其余60bp 左右的DNA连接相邻的核小体。若干核小体重复排列便形成串珠状纤维。

Euchromatin常染色质是DNA复制与基因转录活跃的部位，为间期核内碱性染料时着色较浅，螺旋化程度较低，处于伸展状态。

karyotype核型是指某一个体细胞的全部染色体在有丝分裂中期的表型，包括染色体的数目、大小和形态特征。

G-protein-coupled receptorG蛋白偶联受体:一种膜蛋白受体，可以激活G蛋白，介导许多细胞外信号的传导。其结构特征包括：1、一条多肽链构成，7个跨膜的α螺旋区；2、N端朝向胞外，C端朝向胞内；3、N端有糖基化位点，C端的第三袢环和C端有磷酸化位点。

G protein.G蛋白是一类在信号转导过程中，与受体偶联的、能与鸟苷酸结合的蛋白质，位于细胞膜胞质面，为可溶性的膜外周蛋白，由αβγ三个蛋白亚基组成，有GTP酶的活性，可结合GDP。G蛋白的功能主要是通过其自身构象的变化，激活效应蛋白，进而实现信号从胞外向胞内的的传递。

cell differentiation细胞分化：受精卵产生的同源后代细胞，在形态、结构、功能、蛋白合成等方面逐渐发生稳定性差异的过程称为细胞分化。

oncogene癌基因是控制细胞生长和分裂的正常基因突变的一种形式，能引起正常细胞癌变。heterochromatin异染色质在间期核中处于凝缩状态，结构致密，无转录活性，用碱性染料染色时着色较深。异染色质无转录活性，是遗传惰性区。

polyribosome多聚核糖体当进行蛋白质合成时，大、小亚基必需结合在一起才能发挥作用，而且常常是多个核糖体结合在一条mRNA分子上，称为多聚核糖体。

apoptotic body 凋亡小体：凋亡细胞的染色质凝聚、裂解形成的碎片，随之细胞膜凹陷、分割、包裹，最终形成大小不等的内含胞质、细胞器及染色质碎片的膜包小体

apoptisis细胞凋亡：即细胞程序性死亡PCD，由于生理或非生理因素诱发了细胞内原已存在的死亡机制，使其发生由基因控制的、自主而有序的死亡方式。

luxury gene奢侈基因指与各种分化细胞的特殊性状有直接关系的基因，丧失这类基因对细胞的生存并无直接影响。

1、What is a Prion?"Prion" is short for "proteinaceous infectious particle". A prion is thought to be an infectious agent that is comprised entirely of a propagated, mis-folded protein，with no nucleic acids. The mis-folded form of the prion protein has been implicated in a number of diseases in a variety of mammals, including mad cow disease. All hypothesized prion diseases affect the structure of the brain or other neural tissue, and all are currently untreatable and are always fatal.

2、What are three specific characteristics of cancer cells?1）Cancer cells don't stop reproducing. Unlike normal cells, cancer cells do not stop reproducing after they have doubled 50 or 60 times.2) Tumor forming. The cancer cells may be able to stop themselves self destructing. Or they may self destruct more slowly than they reproduce, so that their numbers continue to increase. Eventually a tumor is formed that is made up of billions of copies of the original cancerous cell. 3) Cancer cells do not obey signals. Something in the cancer cells overrides the normal signaling system. This may be because the genes that tell the cell to reproduce keep on and on firing. Or because the genes that normally tell the cell to stop reproducing have been damaged or lost.4) Cancer cells do not stick together. Cancer cells can lose the molecules on their surface that keep normal cells in the right place. So they can become detached from their neighbors.5) Cancer cells do not become specialized.

3、Please give a brief introduction to the principles and applications of flow cytometry Flow cytometry uses the principles of light scattering, light excitation, and emission of fluorochrome molecules to generate specific multi-parameter data from particles and cells. Cells are hydro-dynamically focused in a sheath before intercepting an optimally focused laser source. A number of detectors are aimed at the point where the stream passes through the light beam. Modern flow cytometers are able to analyse several thousand particles every second, and can actively separate and isolate particles having specified properties.

5、Explain how active transport differs from passive transport.Passive transport involves carriers, channels, or direct diffusion through a membrane. This type of transport always operates from regions of greater concentration to regions of lesser concentration.No external source of energy is required. In active transport it is possible to go against the concentration gradient.In active transport, a source of energy is required to move the carrier and its materials. Primary Active Transport directly uses ATP. Secondary active transport does not directly use ATP.It takes advantage of a previously existing concentration gradient (via carriers).

6、What is Cytoskeleton? What is the main function of a cytoskeleton?

The cytoskeleton is a network of long fibers that make up the cells structural framework，composed largely of microfilament，microtubules and intermediate filaments. The cytoskeleton has several critical functions, including determining cell shape, participating in cell division, and allowing cells to move. It also provides a track-like system that directs the movement of organelles and other substances within cells.

7、What are telomeres?Telomeres are a sequence of repetitive bases at the ends of linear chromosomes that prevent adjacent chromosomes from attaching to each other.They are crucial to maintaining chromosome stability.In many types of cells, telomeres lose a bit of their DNA every time a cell divides. Eventually, when all of the telomere DNA is gone, the cell cannot replicate and dies.