德州学院生物系张红梅

德州学院生物系 张红梅

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Chapter 1 Introduction to the cell Learning Objectives 1.About Cell Biology 2.Look briefly at the history of cell theory; 3.Consider the basic properties of cells; 4.Compare some characteristics of two different classes of cells: prokaryotes and eukaryotes; 5.Comprehend a special life: viruses

1. About “Cell Biology” The NIH of USA(1988): “What is popular in research today？”  3 kinds of diseases： cancer  cardiovascular diseases  infectious diseases：AIDS，hepatitis  5 research fields ： cell cycle control ； cell apoptosis； cellular senescence； signal transduction； DNA damage and repair. What? Forwhy? How to study? What we know//How we know.

ISI（美国科学信息研究所）, USA(1997) : SCI（Science Citation Index）Papers: Three tops of research fields: No1: Signal transduction； No2: Cell apoptosis； No3: Genome and post-genomic analysis。

2. The Cell Theory: A Brief History The discovery of cells followed from the invention of the microscope In 1665, Robert Hooke saw a network of tiny boxlike compartments that reminded him of a honeycomb. He called these little compartments “cellulae”, a Latin term meaning little room. It is from this word we get our present-day term, cell. The microscope used by Robert Hooke and the honeycomb-like network of “cell” he drawed in 1665

Cell theory has three basic tenets: 1. All organisms are composed of one or more cells. 2.The cell is basic unit of structure and function for all organisms. 3.All cells arise only from preexisting cells by division.

3. Why are cells the basic units of life? A. The cell is the structural unit of life, All organisms is make up of cells.

B.The cell is the functional unit of organisms. All metabolic activity is based on cells.

C. The cell is the foundation of reproduce, and the bridge of inheritance.

D. The cell is the growing and developing basis of life Human fetal development. (a)At 5 weeks, limb buds, eyes, the heart, the liver and rudiments of all other organs have started to develop in the embryo, which is only about 1cm long. (b)Growth and development of the offspring, now called a fetus, continue during the second trimester. This fetus is 14 weeks old and about 6cm long. (c)The fetus in this photograph is 20 weeks old. Now the fetus grows to about 30cm in length.

E. Cell (nucleus) is totipotent, which can create a new organism of the same type As a general rule, the cells of a multicellular organism all contain the same set of genes. For animals, the first evidence that even highly specialized cell carry a full complement of genes was verified by the experiment of tadpole nuclei transplanting into unfertilized egg that had been deprived of its own nucleus. Some can develop swimming tadpoles. This is animal cloning. An especially dramatic example of animal cloning was reported in 1997. Dolly the first animal ever cloned from a cell derived from an adult.

Dolly and her daughter The process of cloning Dolly Is there any practical value to such technology?

4. Basic properties of cells • Cells are highly complex and organized, capable of self-regulation; Cells acquire and utilize energy. B. All cells share similar structure, composition and metabolic features: Plasma membrane, DNA/RNA, and Ribosome.

C. Cells can capable of producing more of themselves, even grow and reproduce in culture for extended periods. HeLa cells arecultured tumor cells isolated from a cancer patient named Henrietta Lacks in 1951. It is the first human cell to be kept in culture for long periods of time and is still used today. Johns Hopkins univesity,in 1951

D. Cells are able to respond to stimuli via surface receptors that sense changes in the chemical environment. Cells within plant or animal respond to stimuli less obviously than single-celled protist. But they respond. They posses receptors that interact with substances in the environment in highly specific ways. For example, the receptor on the cell surface can respond to hormones and growth factors.

5.The Size of Cells • diameter • Measured in units of • micrometers: 1um=10-6 meter • nanometers: 1nm=10-9 meter • c) Cell size is limited: • nucleus/cytoplasm ratio; • surface area/volume ratio; • substances can efficiently travel • through the cytoplasm via diffusion.

6. Two fundamentally different classes of cells: Prokaryotes and eukaryotes A. Prokaryotic and eukaryotic cells are distinguished by the size and the types of internal structures, or organelles, especially if there is nuclear envelope. Bacteria are prokaryotes, they arose 3.5 billion years ago; Protists, fungi, plants, and animals are eukaryotes. The first eukaryotes arose 1.5 billion years ago.

B. Characteristics that distinguish prokaryotic and eukaryotic cells • Complexity: Prokaryotes are relatively simple, eukaryotes are more complex in structure and function

(2) Genetic material: All Cells Store Their Hereditary Information in the Same Liner Chemical Code (DNA) • Packaging: Prokaryotes have a nucleoid region whereas ekukaryote have a true, membrane-bound nucleus. (bacterinm:0.25-3.0 mm, to encode between several hundred and several thousand proteins,The simplest known cells have just under 500 genes). • b. Amount:Eukaryotes have several orders of magnitude more genetic material than prokaryotes.(yeast:4.6mm DNA,encoding about 6200 proteins) • c. Form: Eukaryotes have many chromosomes that are made of both DNA and protein whereas prokaryotes have a single ,“naked” DNA chromosome • Packaging: Prokaryotes have a nucleoid region whereas ekukaryote have a true, membrane-bound nucleus. • b. Amount:Eukaryotes have several orders of magnitude more genetic material than prokaryotes. • c. Form: Eukaryotes have many chromosomes that are made of both DNA and protein whereas prokaryotes have a single DNA chromosome

(3) Cytoplasm: Eukaryotes have membrane-bound organelles and cytoskeletal proteins; prokaryotes have neither. Both have ribosomes, although they differ in size. (4) Cellular reproduction: Eukaryotes divide by mitosis; prokaryotes divide by simple fission. (5) Locomotion: Eukaryotes use both cytoplasmic movement, and cilia and flagella; prokaryotes have flagella, but they differ in both form and mechanism from eukaryotic flagella.

The difference between prokaryotic and eukaryotic flagela Flagellin Human sperm

C.Three structural systems in Eukaryotes:

7.Types of Prokaryotic Cells: Two Subkingdoms(门） • Tree of life has three primary branches. • A. Subkingdom Archaea • Subkingdom Bacteria • Most Bacteria and Archaea have 1000-4000 genes • The smallest known cells • ---the Mycoplasma • 0.1～0.3μm; • smallest genome:482 genes, • minimal essential gene：256

1.Viruses are pathogens first described in the late 1800s. 2. Viral structure: a)The genetic material: Single- or double- straded DNA orRNA. B）protein. 8. Viruses Virus diversity 3.Viral infection types: a)Lytic infection; b)integrated infection

4. Viral origins: a)Viruses had to arise after their hosts evolved; b)Viruses probably arose as fragments of host chromosomes. 5.Viroids 6.prion

9. Reference book Gerald Karp. Cell and Molecular Biology：concepts and experiments，3nd Edition. Published by John Wiley & Sons,Inc. 2002 Gerald Karp. Cell and Molecular Biology：concepts and experiments，4rd Edition. Published by John Wiley & Sons,Inc. 2005 Lodish H. et al. Molecular Cell Biology. 4th Ed. Scientific American Books,Inc. 2000.

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德州学院生物系 张红梅