本期内容是 实验三：细胞结构 - 细胞理论与细胞器 的实验手册，实验模拟请看下一期。本部分内容来自 University of California, Berkeley - UC Berkeley Extension, 虚拟实验的内容来自 Labster. 本部分内容均不会标记为为原创，但由于是UP主购买的课程，因此不接受非授权的转载，谢谢您的理解。

每一个生物基础实验均会分为三部分：第一部分为实验的生物理论；第二部分为实验的指导手册；第三部分为 Labster 的虚拟实验模拟。第一部分的基本信息由 Ying Liu, Ph.D. 提供，第二部分的实验手册来自 Labster, 第三部分的实验模拟过程由UP主操作。

Lab 3: Virtual Lab Manual: Cell Structure: Cell theory and internal organelles

Synopsis

What components make your cells unique? In this simulation, you will learn to distinguish the structures and internal organelles of prokaryotes and eukaryotes. Physical structures of the four basic animal cell types will be highlighted and the function and importance of each internal organelle will be discussed. 

Investigate a bear’s death

Hikers have discovered a dead bear and it’s your mission to determine why it died. First, freely explore what types of organisms are present in the forest surrounding the bear and observe real microscopic images of their tissues. Determine whether the organisms are unicellular or multicellular and sort the organisms according to whether they have a cell membrane or cell wall. Finally, build the deadly organism by building 4 cells representative of each basic type of animal tissue: neural, epithelial, muscle and connective tissue.

Apply cell theory

Students will be introduced to each principle of cell theory and apply it to understand how the cellular organization of animal cells in the forest compares to algae, mushrooms, plant roots, and leaves. An incoming storm will help you understand the implication of having a cell wall. After additionally categorizing the organisms as prokaryotes or eukaryotes, you will then build larger-than-life versions of each of the four animal cell types on the holofloor.

Challenged to choose the correct internal organelles for the animal cells, you will learn about the function and importance of the nucleus, ER, cytoskeleton, Golgi apparatus, lysosomes, ribosomes, and mitochondria.  Then, determine which cellular structures are unique to specific animal cells such as sarcomeres, tight junctions, axons, dendrites and the extracellular matrix. 

Uncover the mystery animal

Put together everything you have learned about organelles and cellular structures to build each type of cell in the mystery organism. Will you find out what killed the bear?

Learning Objectives

At the end of this simulation, you will be able to…

    ● Explain cell theory;

    ● Describe the main differences between the prokaryotes, eukaryotes, plants and animals;

    ● Describe the different intracellular and extracellular components forming eukaryotic cells.

Techniques in Lab

    ● Reading scientific papers;

    ● Analyzing blood sugar measurements.

Theory

Cell Theory

As microscopes improved throughout history, scientists were able to better examine what living tissues were made of. They often found that living organisms were composed of small compartments or pores. Robert Hooke was the first scientist to name these "cells" in 1665, after the small rooms that monks inhabit.

Two scientists are credited with developing cell theory. Matthias Jakob Schleiden was a botanist who found cells in all plants he examined. In 1839, Theodor Schwann, a physiologist, found that he also found cells in animal tissues. Together, they postulated the first two of the three cell theory tenets. However, where cells came from was still debated until, in 1855, Rudolf Virchow, a pathologist, added the third tenet to cell theory.

The three tenets of cell theory are:

    1. All living organisms are composed of cells;

    2. Cells are the structural and organizational unit of life;

    3. All cells come from pre-existing cells.

Eukaryotes vs. Prokaryotes

Cells are divided into two broad categories: prokaryotic cells and eukaryotic cells. Prokaryotic cells include the single-cell organism bacteria and archaea. Animal cells, plant cells, protists, and fungi are eukaryotes. Viruses are not included in these categories as viruses are not independently living organisms but are dependent on living cells as hosts in order to replicate.

All living cells share five components: a plasma membrane, cytoplasm, DNA, ribosomes and a cytoskeleton. However, eukaryotes and prokaryotes differ in many different ways.

Eukaryotic cells contain more specialized organelles, such as the endoplasmic reticulum, Golgi apparatus, mitochondria, and lysosomes compared to prokaryotes.

The eukaryotic ribosomes are larger. They consist of a 60S large subunit and 40S small subunit which comes together to form an 80S complete ribosome whereas the prokaryotic cells have 70S ribosomes. The DNA of eukaryotes is contained within a nucleus whereas prokaryotic DNA is found freely in the cytoplasm in a region called the nucleoid.

Prokaryotes also contain extrachromosomal DNA called plasmids which eukaryotes don’t.

Types of Animal Cells

The cells of an animal all contain the same DNA, however they have specialized throughout a process of differentiation to become unique, both functionally and structurally.

- Animal cells can be divided into 4 main tissue types:

     ● Muscle Tissues: Muscles are unique cells in our body for their ability to contract which changes both the length and shape of the cell. A group of muscle cells contracting together can produce a large force and movement in the body. There are three types of muscle: skeletal (voluntary contraction), cardiac (of the heart) and smooth (involuntary muscle). Both skeletal and cardiac contain sarcomeres, which give the muscle a striated appearance.

     ● Nervous Tissue: There are two main types of cells in the nervous system: neurons and glia. Neurons are specialized cells responsible for signal transduction in our body. Glia are support cells that support and insulate neurons.

     ● Epithelial Tissue: Epithelial cells line the outer surfaces of organs and blood vessels, as well as the inner surfaces of lumens. They maintain a strong barrier between different types of environments. There are three main shapes of epithelial cells: squamous (flat), columnar (tall), and cuboidal (square).

     ● Connective Tissues: Composed mainly of secreted proteins, connective tissue is found between other types of tissues. Adipose (fat), bone and blood are all examples of connective tissues.

感谢阅读！下一期将进行 Labster 实验！