Cell Membrane Coloring Worksheet

Antonie van Leeuwenhoek, a merchant from the Netherlands, was among the first to observe microorganisms with a magnifying lens. Since 1673, Leeuwenhoek wrote letters describing small creatures he called animalcules to the Royal Society of London. Through his simple microscope consisting of 1 lens, Leeuwenhoek sent pictures of animalcules in rainwater, peppercorn solution, and corrugated teeth.

At almost the same time as Robert Hooke, an Englishman used a microscope to observe bottle caps made of dead plant cell walls. Hooke called the pores between the cell walls a tiny box or cell. His discovery of the structure of the bottle cap in 1665 was the beginning of the cell theory.

Between the years 1838-1839, two German scientists, namely the botanist Matthias Schleiden and the zoologist Theodor Schwann have gathered a lot of information about the cells in living things. Their results concluded that all living things consist of cells. Subsequent studies on the structure and function of cells have always been based on this theory which is an important starting point for modern biology.

Basic Cell Membrane And Functions Worksheet
Darlene Young
February 24, 2021


In 1877, the English physicist John Tyndall demonstrated that heat-resistant microbes could not be destroyed by boiling. At the same time Ferdinand Cohn, a botanist from Germany discovered that heat-resistant bacteria can form endospores. Tyndall developed a gradual heating technique that destroys heat-resistant microbes. With this technique the solution is brought to a boil and is cooled so that the heat-resistant endospores will grow, then it is boiled again. This process of boiling and cooling is repeated many times and this method is called piercing.


Louis Pasteur and Robert Koch were the first to link microorganisms and disease. Their research results gave birth to the Microbial Theory of Disease Causes. Pasteur made vaccines, which are disease-causing microbes that are weakened to prevent disease. By injecting the vaccine into the body of experimental animals, Pasteur succeeded in obtaining animals that were resistant to erythematousism in pigs, cholera in chickens, anthrax, and rabies. Koch (1843-1910) found very strong evidence that the anthrax disease which kills cows is caused by bacteria. He observed the presence of rod-shaped bacteria.

In the spleen and blood of cows affected by anthrax, which is not present in the spleen or blood of healthy cows. Koch also succeeded in culturing these rod-shaped bacteria on an artificial medium in the laboratory. By injecting laboratory-cultured bacteria into mice,

Koch caught mice with symptoms of anthrax disease and died. The same bacteria can also be isolated from the spleen and blood of the dead mice. Koch carried out the same evidence for the bacteria that cause tuberculosis. The results of his findings resulted in the Koch (Koch Postulate) theory, namely:

  1. microorganisms suspected to be the cause of the disease must be consistently present in sick animals/humans but not in those who are healthy;
  2. The microorganisms must be able to be reproduced in vitro in the laboratory;
  3. if the pure microbial culture is injected into a suitable animal/human then the symptoms of the same disease will arise;
  4. the same organism must consistently be isolated from its new infected host.


The above discoveries are not only important but also stimulate many new discoveries in the field of microbiology. Because of the many new discoveries by scientists, the years 1875-1915 are often called the golden age. Some of the important discoveries at that time, among others:

  1. use of agar, Petri dishes to breed microbes in the laboratory, gram staining to distinguish bacteria, pasteurization to kill disease-causing microbes (pathogens);
  2. the discovery of microbes that can use inorganic compounds, such as ammonia and nitrates as sources of nitrogen, as well as bacteria that can photosynthesize;
  3. knowing the body’s defense system (antibody) in response to pathogenic microbes;
  4. discovery of antibiotic compounds;
  5. the discovery of the virus;
  6. development of vaccines and chemotherapy.
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