高级微生物20141020

Why do cells need to respond to signals?
1.
Need to respond to a changing environment


Adaptation or a cellular response is critical for survival Glucose acts as a signal to yeast cells to increase number of glucose transporters and enzymes allowing efficient uptake and use of glucose
3. Cellular Response
Response is inititiated and/or occurs entirely within receiving cell
Three Stages of Signal Transduction
1. Reception
Three Stages
2aling has remained important in the microbial world.

Myxobacteria, soil-dwelling bacteria, use chemical signals to communicate nutrient availability. When food is scarce, cells secrete a signal to other cells leading them to aggregate and form thick-walled spores.

There are two sexes, a and alpha, each of which secretes a specific signaling molecule, a factor and alpha factor respectively. These factors each bind to receptor proteins on the other mating type.

Fig. 11.2
1 Individual rodshaped cells
2 Aggregation in process
0.5 mm
3 Spore-forming structure (fruiting body)
Fruiting bodies



A plasma membrane is essential for a cell It does isolate the cell from its surroundings A cell cannot survive if it cannot sense changes in the extracellular environment and respond to them
Introduction

Cell-to-cell communication is absolutely essential for multicellular organisms.

Cells must communicate to coordinate their activities.

Communication between cells is also important for many unicellular organisms. Biologists have discovered some universal mechanisms of cellular regulation, involving the same small set of cell-signaling mechanisms. Cells may receive a variety of signals: chemical signals, electromagnetic signals, and mechanical signals.

The molecular details in both yeast and animal cells are strikingly similar, even though their last common ancestor was over a billion years ago.

Signaling molecules evolved first in ancient prokaryotes and were then adopted for new uses by single-celled eukaryotes and multicellular descendents.



Cell communication is the process of cells detecting and responding to signals in the extracellular environment Needed to coordinate cellular activities in a multicellular organism One important reason for cell communication is to promote cell division



The process by which a signal on a cell’s surface is converted into a specific cellular response is a several steps in a signal-transduction pathway.
Section A: An Overview of Cell Signaling 1. Cell signaling evolved early in the history of life
2. Communicating cells may be close together or
far apart 3. The three stages of cell signaling are reception, transduction, and response



Cell communication or cell signaling involves incoming and outgoing signals Signals are agents that influence the properties of cells Signals affect the conformation of a receptor leading to a response in the cell
These communications are deliberately initiated, received, and interpreted in order to increase the physiological coordination of the cells in multicellular organisms We will consider in particular those events that follow the reception of chemical signals
Three Stages of Signal Transduction
1. Reception of extracellular signal by cell
2. Transduction of signal from outside of cell to inside of cell—often multi-stepped Note not necessarily transduction of ligand
2b. Transduction
2c. Transduction
2d. Transduction
3. Response
Responses usually involve increasing or decreasing some Protein’s Function
1. Reception
Three Stages
一、细胞通讯 (cell communication) 与 信号转导(signal transduction)概述
细胞通讯是细胞间或细胞内通过高度精确和高 效地发送与接收信息的通讯机制，对环境作出
综合反应的细胞行为。
细胞信号转导
细胞通过位于胞膜或胞内的受体感受胞外信息分子的刺激，经复杂 的细胞内信号转导系统的转换来影响细胞的生物学功能。
Signal-Transduction Emphasis
This chapter’s emphasis is on signals that are released from one cell and allowed to freely diffuse to a second (or more) recipient cell(s)
细胞通讯与信号传递引起的反应
◆酶活性的变化
◆基因表达的变化
◆细胞骨架构型
◆通透性的变化
◆DNA合成活性的变化
◆细胞死亡程序变化等。
细 胞 通 讯 的 作 用
● 细胞间的通讯对于多细胞生物体的发生和组织的构建，协调细胞的功能，控制细
胞的生长、分裂、分化和死亡是必须的。
CELL COMMUNICATION


1. Cell signaling evolved early in the history of life

One topic of cell “conversation” is sex. The yeast Saccharomyces cerevisiae, the yeast of bread, wine, and beer, identifies its mates by chemical signaling.