生物学知识琐碎，想要顾及前沿研究时课本内容更甚。本专栏供大学生或对该学科感兴趣人士梳理逻辑思路，或用于备考APS、考研专业课英语应答。

内容与逻辑

细胞生物学，从字眼上看离不开细胞和生物学。学习内容可分为两个部分：细胞，还有细胞之间的活动。学习的逻辑遵循寻常生物学的学习逻辑：结构->功能。

人体由若干细胞组成并共同行使功能，细胞生物学着重于介绍人体基础功能在细胞层次上的实现细节。下面依次介绍单个细胞、细胞间的具体内容。

单个细胞

• 蛋白质行使人体中的许多重要功能。对单个细胞而言，你可以从细胞的蛋白质运输这个功能出发，了解单个细胞的结构组成，如相关的细胞器、细胞器如何行使功能。

如，内质网->高尔基体->细胞膜，在此过程中，蛋白质在哪个细胞器进行甲基化、折叠、校正等等，最终如何包装、分选。最后，或在细胞内行使功能，或分泌到细胞外环境。

e.g. 神经突触处的神经递质释放：从细胞体，通过细胞骨架结构运输，达到轴突末端并释放；或神经递质的消化，即反向运输并消化或储存膜跑运输下的神经递质。（神经递质不仅仅有着一种运输方式）

细胞间功能

• 细胞间最重要的功能，即它们的通信，大多通过细胞信号转导实现。一般由信号分子，即配体，同细胞膜上受体结合，进而影响细胞内环境。

转导主要有两种，第一种直接由简单的配体受体结合影响胞内代谢，第二种则在结合后经过第二信使（多为代谢通路中的某个物质，如cAMP），最终影响胞内代谢。

学习内容主要在受体，受体分三类，离子通道偶联、G蛋白偶联和酶联。

e.g. G蛋白有三个部分，G-alpha,beta,gamma。未被激活时，G蛋白结合一分子GDP；激活时，受体和配体结合，改变了改受体的构象，G蛋白磷酸化变为G-GTP, Ga脱离b,y，作为Ga-GTP结合到受体上进行下一步信号转导。

Content&Logic

We approach Cell Biology by learning the function, and what structure is involved to achieve the function. Following this logic, we focus on 2 aspects: single cell, and how cell interact with each other.

Single Cell

Protein working as the function unit. So, in a cell, we should understand protein synthesis and secretion. We should also know the involved organelles (roughER, Golgi apparatus, vesicles etc), and in which one the protein is phosphorylated, sorted and packaged.

e.g. In synapses, neurotransmitter was first synthesized in the cell body, transferred on microfilaments, and then reach at the axon terminals. Vice versa, it can also be absorbed and digested by the pre-synaptic neuron.

Cell interconnection

Cells communicate by signal transduction, which is achieved by ligand-receptor binding. The binding would then affect by changing the cell metabolism. 

There are 2 ways, one is the simple ligand-receptor binding, the other is through a second messenger. And there are 3 types of receptor: Ion-channel coupled, G-protein coupled and Enzyme coupled.

e.g. G-protein are made up of G-alpha, G-beta and G-gamma. In the inactive state, G-protein would be bind with a GDP, as Ga,b,y-GDP. When activated, The GDP phosphorylated and turned into GTP. The Ga-GTP would dissociate from Gb and Gy, and bind with the ligand-receptor complex.