Cell Theory: History and Modern Tenets
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Questions and Answers

Robert Hooke coined the term 'cells' based on his observation of which of the following?

  • Living bacteria under high magnification.
  • Animal tissues dividing rapidly.
  • Plant tissues undergoing crystallization.
  • Thin sections of cork resembling honeycombs. (correct)

How did Matthias Schleiden contribute to the development of the cell theory?

  • He disproved the theory of spontaneous generation.
  • He proposed that all cells arise from pre-existing cells.
  • He identified similarities between plant and animal tissues at the cellular level.
  • He described plant tissues as being composed of cells. (correct)

Theodor Schwann's primary contribution to cell theory involved:

  • Postulating that cells only exist in plant tissues.
  • Realizing the similarities between plant and animal tissues at a cellular level. (correct)
  • Developing the first microscope capable of viewing cells.
  • Discovering that cells spontaneously generate from non-living matter.

Which statement best reflects Rudolf Virchow's contribution to the cell theory?

<p>He popularized the concept that all cells arise from pre-existing cells. (A)</p> Signup and view all the answers

How did Robert Remak's findings influence the development of cell theory?

<p>He provided evidence that cells are derived from other cells through cell division. (B)</p> Signup and view all the answers

What was a key difference between Schleiden's and Schwann's initial views on cells?

<p>Schleiden believed cells formed through crystallization, while Schwann did not. (D)</p> Signup and view all the answers

Which of the following best describes the significance of Hooke's contribution to cell theory?

<p>He was the first to observe and name cells, though he didn't know their function. (B)</p> Signup and view all the answers

How does modern cell theory build upon the work of Schleiden and Schwann?

<p>It incorporates their discovery that cells are the basic components of plants and animals. (B)</p> Signup and view all the answers

What was the primary reason many physicians initially dismissed the idea that microbes caused postsurgical infections, despite high mortality rates?

<p>They adhered to the miasma theory, which attributed disease to bad air. (B)</p> Signup and view all the answers

How did Joseph Lister contribute to the reduction of postsurgical infections?

<p>By using carbolic acid as a disinfectant/antiseptic during surgery. (D)</p> Signup and view all the answers

What is the significance of Koch's postulates in the history of microbiology?

<p>They provided a framework for definitively linking specific microbes to specific diseases. (D)</p> Signup and view all the answers

How did Koch's work influence the understanding of the cause of infectious diseases?

<p>It shifted the focus from environmental factors to specific microorganisms as causative agents. (B)</p> Signup and view all the answers

In the clinical focus case described, what findings led the PA to suspect Barbara had pneumonia?

<p>Greenish sputum, crackling sounds in the lungs, and a shadow on the chest radiograph. (C)</p> Signup and view all the answers

What is the term for the condition where Barbara has a lower-than-normal level of oxygen in the blood?

<p>Hypoxemia (B)</p> Signup and view all the answers

What is the primary purpose of using a stethoscope during a physical examination, as mentioned in the clinical scenario?

<p>To detect abnormal sounds in the heart, lungs, and digestive system (B)</p> Signup and view all the answers

How did Joseph Lister's approach differ from that of many physicians regarding postsurgical infections?

<p>He recognized the role of microbes in causing infections and insisted on cleanliness. (D)</p> Signup and view all the answers

What was a key outcome of Koch's postulates in the field of infectious diseases?

<p>The ability to definitively identify the pathogens responsible for specific diseases. (A)</p> Signup and view all the answers

In the scenario with Barbara, which diagnostic tool provided visual evidence of a potential issue in her lungs?

<p>Chest radiograph (B)</p> Signup and view all the answers

Which of the following pieces of evidence most strongly supports the endosymbiotic theory regarding the origin of mitochondria and chloroplasts?

<p>The structural similarity between mitochondrial and chloroplast ribosomes and bacterial ribosomes. (A)</p> Signup and view all the answers

How did the work of Semmelweis and Snow collectively challenge the miasma theory of disease?

<p>By showing that disease is not only transmitted through the air but also through contaminated items. (B)</p> Signup and view all the answers

What was a key reason why Fracastoro's early proposal of the germ theory of disease was not widely accepted in the 16th century?

<p>The prevailing scientific understanding at the time favored alternative theories, and his ideas were largely forgotten. (D)</p> Signup and view all the answers

Which of the following statements best describes the contribution of Ibn Zuhr to understanding the causes of disease?

<p>He documented that the common skin condition scabies was caused by tiny mites that bored into the skin. (B)</p> Signup and view all the answers

How did Pasteur's swan-neck flask experiments contribute to the development of the germ theory of disease?

<p>They showed that airborne microbes, not spontaneous generation, were the cause of food spoilage. (D)</p> Signup and view all the answers

What critical observation led Semmelweis to suspect that physicians were transmitting puerperal fever to their patients?

<p>The correlation between physicians performing autopsies and subsequently examining patients without washing their hands and higher rates of puerperal fever. (C)</p> Signup and view all the answers

Which of the following is a valid conclusion based on Snow's epidemiological study of cholera outbreaks in London?

<p>Cholera is transmitted via drinking water contaminated by sewage. (C)</p> Signup and view all the answers

Mitochondrial DNA is reduced compared with nuclear DNA because:

<p>Many essential genes have been transferred from the organelles into the host cell's nucleus. (B)</p> Signup and view all the answers

Which theory did the ancient Greeks propose to explain the origin of disease before the discovery of microbes?

<p>The miasma theory, stating that disease originated from particles emanating from decomposing matter. (A)</p> Signup and view all the answers

Ibn Sina (Avicenna) proposed a mode of transmission for tuberculosis. What was it?

<p>Through people's breath when in close proximity. (C)</p> Signup and view all the answers

What is the significance of the discovery of endosymbiotic bacteria in modern-day eukaryotic cells in the context of endosymbiotic theory?

<p>It provides direct evidence supporting the theory that endosymbiosis is an ongoing evolutionary process. (B)</p> Signup and view all the answers

In what fundamental way did the work of Pasteur, Koch, and Lister advance the understanding of disease beyond the contributions of Semmelweis and Snow?

<p>They identified the specific microbial agents responsible for causing various diseases. (B)</p> Signup and view all the answers

Which of the following characteristics of mitochondria and chloroplasts provide evidence for their endosymbiotic origin?

<p>Their mode of replication through binary fission, resembling that of bacteria. (C)</p> Signup and view all the answers

Which of the following statements accurately reflects a significant difference between the work of Semmelweis and Snow in addressing disease?

<p>Semmelweis implemented a preventative measure (handwashing) based on observation, while Snow conducted an epidemiological study to identify the source of infection. (A)</p> Signup and view all the answers

Photosynthetic bacteria-like organelles are found in:

<p>Protists (C)</p> Signup and view all the answers

Which action by Rudolf Virchow is most debated regarding the articulation of cell theory?

<p>Publishing the idea that all cells arise from other cells without crediting Robert Remak. (A)</p> Signup and view all the answers

What factor, besides Virchow's reputation, contributed to the lack of immediate repercussions for his alleged plagiarism of Remak's work?

<p>The absence of established standards for academic integrity during the 19th century. (B)</p> Signup and view all the answers

How do modern practices in scientific publishing help to prevent plagiarism, in contrast to the practices during Virchow's time?

<p>Peer review processes and easy access to scientific literature make plagiarism more easily detectable. (A)</p> Signup and view all the answers

What was Robert Brown's primary contribution to the study of cells?

<p>First describing observations of nuclei in plant cells. (A)</p> Signup and view all the answers

What critical role of chloroplasts was first described by Andreas Schimper?

<p>Their function in starch formation during photosynthesis. (A)</p> Signup and view all the answers

Konstantin Mereschkowski's work, predating Lynn Margulis, significantly contributed to the development of the endosymbiotic hypothesis. What was his key proposition regarding the origin of chloroplasts?

<p>Chloroplasts arose from symbiotic relationships with ancestral photosynthetic bacteria. (D)</p> Signup and view all the answers

How did Ivan Wallin attempt to support the endosymbiotic hypothesis experimentally?

<p>By culturing mitochondria outside of eukaryotic host cells. (C)</p> Signup and view all the answers

Why were Ivan Wallin's ideas regarding the endosymbiotic hypothesis initially dismissed by the scientific community?

<p>Scientists at the time were unaware that organelles contained their own DNA. (C)</p> Signup and view all the answers

What critical evidence led to the revival and wide acceptance of the endosymbiotic theory in the 1960s?

<p>The discovery of mitochondrial and chloroplast DNA. (A)</p> Signup and view all the answers

What was Lynn Margulis's primary contribution to the endosymbiotic theory?

<p>She compiled and presented extensive evidence supporting the prokaryotic origins of eukaryotic organelles. (B)</p> Signup and view all the answers

Before the wide acceptance of Margulis's endosymbiotic theory, what technological advancement significantly contributed to the understanding of cell structure that supported her claims?

<p>Advances in microscopy that allowed differentiation between prokaryotic and eukaryotic cells. (A)</p> Signup and view all the answers

According to modern understanding, what defines the endosymbiotic theory?

<p>The theory that mitochondria and chloroplasts originated from symbiotic relationships between prokaryotic cells and a eukaryotic host. (C)</p> Signup and view all the answers

How did genome sequencing contribute to disproving Wallin's claim that mitochondria could be cultured independently?

<p>It revealed that mitochondria lack the necessary genes for independent survival, as many genes had been transferred to the host cell's nucleus. (A)</p> Signup and view all the answers

What was the main focus of Margulis's expanded theory in her 1981 book, Symbiosis in Cell Evolution, following the initial acceptance of her endosymbiotic theory?

<p>Expanding on the implications and broader applications of symbiosis in cell evolution. (B)</p> Signup and view all the answers

Which of the following statements best describes the lasting impact of the endosymbiotic theory on modern biology?

<p>It remains a foundational concept for understanding the evolution of eukaryotic cells and the origins of organelles. (B)</p> Signup and view all the answers

Flashcards

First tenet of cell theory

All living things are composed of one or more cells.

Second tenet of cell theory

Cells arise from pre-existing cells.

Robert Hooke

First to use the term "cells" to describe small chambers within cork.

Matthias Schleiden

Observed plant tissues and described them as composed of cells.

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Theodor Schwann

Observed animal tissues and realized the similarities between plant and animal tissues.

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Robert Remak

Showed cells are derived from other cells via cell division.

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Rudolf Virchow

Popularized cell theory with 'omnis cellula a cellula'.

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Omnis cellula a cellula

All cells arise from pre-existing cells.

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Joseph Lister

British surgeon who introduced antiseptic surgery.

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Carbolic acid

A chemical (phenol) used by Lister as a disinfectant/antiseptic.

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"One microbe, one disease"

The concept that a specific disease is caused by a specific microbe.

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Koch's postulates

A set of principles linking specific diseases to specific microbes.

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Hypoxemia

A lower-than-normal level of oxygen in the blood.

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Pulse oximeter

Instrument to check oxygen levels in the blood

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Crackling sound in the chest

Abnormal sounds caused by air moving through airways containing fluid

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Shortness of breath

Shortness of breath.

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Sputum

Mucus coughed up from the lower airways (trachea and lungs).

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Pneumonia

A condition in which the lungs fill with mucus.

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Rudolf Virchow's Contribution

Proposed all cells arise from other cells.

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Robert Remak's Discovery

Published the idea that all cells arise from other cells 3 years before Virchow.

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Robert Brown's Discovery

Described observations of nuclei in plant cells.

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Andreas Schimper's Discovery

First described chloroplasts and their role in starch formation.

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Konstantin Mereschkowski

Suggests chloroplasts originated from ancestral photosynthetic bacteria living symbiotically inside a eukaryotic cell.

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Ivan Wallin's Experiments

Furthered the endosymbiotic hypothesis and experimentally examined similarities between mitochondria, chloroplasts, and bacteria.

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Endosymbiotic Theory

The theory that mitochondria and chloroplasts arose from prokaryotic cells establishing a symbiotic relationship within a eukaryotic host.

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Lynn Margulis's Contribution

Published ideas regarding the endosymbiotic hypothesis of the origins of mitochondria and chloroplasts in 1967.

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Chloroplast

Organelle of plant cells that conducts photosynthesis.

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Virchow's medical contributions

First to name numerous diseases and create many medical terms.

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Mitochondria

An organelle found in large numbers in most cells, in which the biochemical processes of respiration and energy production occur.

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Nucleus

The central and most important part of an object or group, forming the basis for its activity and growth.

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Plagiarism

The stealing or passing off as one's own of the ideas or words of another.

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Virchow's Innovative Approaches

Determining the causes of various diseases by examining their effects on tissues and organs.

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Cellular Pathology "Cell Divison"

Conducted an essay where Virchow proposed the central tenet of modern cell theory that all cells arise from other cells

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Endosymbiosis

Evolution of organisms driven by symbiosis, where one organism lives inside another.

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Organelle DNA Similarity

Mitochondria and chloroplasts share DNA/structure with bacteria, suggesting common ancestry.

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Miasma Theory

Theory that diseases originate from decaying matter's particles, infecting nearby humans.

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Ibn Sina & Tuberculosis

Proposed tuberculosis spread through close proximity breathing.

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Ibn Zuhr & Scabies

Documented scabies caused by tiny mites burrowing into skin.

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Girolamo Fracastoro

Proposed seed-like spores transmit diseases through contact/air.

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Germ Theory of Disease

Diseases result from microbial infections.

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Ignaz Semmelweis's Observation

Observed higher puerperal fever deaths in physician-attended births.

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Semmelweis's Solution

Handwashing with chlorinated lime water reduces puerperal fever cases.

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John Snow & Cholera

Cholera spread via sewage-contaminated water sources.

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Snow's Epidemiological Study

First known epidemiological study, linking cholera outbreaks to water sources.

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Pasteur's Discovery

Airborne microbes cause food spoilage, not spontaneous generation.

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Germ Theory Foundation

Microbes can cause infections.

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Symbiosis

Organisms live inside another.

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Organelle Ribosomes

Mitochondrial and Chloroplast ribosomes resemble bacterial ribosomes.

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Study Notes

  • Modern cell theory's two tenets are that all living things are composed of one or more cells, and that the cell is the basic unit of life.
  • Modern cell theory is fundamental to understanding of life.
  • Robert Hooke first used the term "cells" in 1665 to describe small chambers within cork observed under a microscope.
  • Hooke likened the cork sections to "Honey-comb".
  • Matthias Schleiden in 1838 described plant tissues as composed of cells, believing they formed through crystallization.
  • Theodor Schwann in 1839 recognized similarities between plant and animal tissues, laying the foundation for cells as fundamental components.
  • Robert Remak in 1852 published evidence that cells are derived from other cells via cell division.
  • Rudolf Virchow in 1855 popularized cell theory "omnis cellula a cellula" ("all cells arise from cells") in an essay.
  • Controversy exists over who should receive credit for cell theory due to the similarity of Virchow's work to Remak's.

Ethical Controversy: Virchow and Remak

  • Virchow did not credit Remak for the idea that all cells arise from other cells which Remak published 3 years prior.
  • Virchow dismissed Remak's letter pointing out similarities by stating his publication was an editorial piece and didn't require citation.
  • Virchow's actions would be considered plagiarism by today's standards.

Discovery of Structures Within Cells

  • Robert Brown in 1831 first described observations of nuclei in plant cells.
  • Andreas Schimper in the early 1880s first described chloroplasts of plant cells and their role in starch formation.
  • Konstantin Mereschkowski in 1905 suggested chloroplasts may have originated from ancestral photosynthetic bacteria living symbiotically inside a eukaryotic cell, and proposed similar origin for nucleus, it was the first articulation of the endosymbiotic hypothesis.
  • Ivan Wallin furthered the endosymbiotic hypothesis in the 1920s, experimentally examining the similarities between mitochondria, chloroplasts, and bacteria.
  • Wallin claimed he could culture mitochondria outside of eukaryotic host cells, but many scientists dismissed his cultures as bacterial contamination.
  • Lynn Margulis in 1967 published ideas regarding the endosymbiotic hypothesis of the origins of mitochondria and chloroplasts.
  • It argued that eukaryotic organelles like mitochondria and chloroplasts are of prokaryotic origin based on microscopic, genetic, molecular biology, fossil, and geological data.
  • Endosymbiotic theory states that mitochondria and chloroplasts arose as prokaryotic cells established a symbiotic relationship within a eukaryotic host.
  • Mitochondrial DNA and chloroplast DNA are highly related to their bacterial counterparts, but reduced as many genes have moved to the host cell's nucleus.
  • Mitochondrial and chloroplast ribosomes are structurally similar to bacterial ribosomes.
  • Binary fission of these organelles resembles bacterial binary fission.

Historical Theories of Disease

  • The ancient Greeks proposed the miasma theory, which held that disease originated from particles emanating from decomposing matter.
  • Ibn Sina proposed that tuberculosis was likely spread by people's breath in close proximity.
  • Ibn Zuhr documented that scabies was caused by tiny mites that bored into the skin.
  • Girolamo Fracastoro in 1546 proposed that seed-like spores may be transferred between individuals, as an early proponent of the germ theory of disease.
  • Ignaz Semmelweis in 1847 observed that handwashing with chlorinated lime water reduced puerperal fever, demonstrating its effectiveness in disease transmission.
  • John Snow in 1848 traced cholera outbreaks to contaminated water sources, demonstrating that cholera bacteria were transmitted via drinking water, an early example of epidemiology.
  • Louis Pasteur discovered properties of fermentation by microorganisms, suggesting microbes could also cause infection, laying the foundation for germ theory.
  • Joseph Lister in 1867 began using carbolic acid spray disinfectant/antiseptic during surgery, reducing postsurgical infection and establishing cleanliness as standard practice.
  • Robert Koch proposed Koch's postulates, attributing specific diseases to specific microbes.
  • Koch and colleagues identified causative pathogens for anthrax, tuberculosis, and cholera, solidifying the shift from miasma theory to germ theory.

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Explore the evolution of cell theory, from Hooke's initial observations to the modern understanding that all living things are composed of cells. Learn about the key contributions of Schleiden, Schwann, Remak, and Virchow, and the theory's fundamental role in biology. Consider the ethical controversies of cell theory.

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