Becker's World of the Cell Chapter 1

What two factors restricted progress in early cell biology?

1. Limited resolution on microscopes (resolving power)

2. Descriptive nature of cell biology, the focus was on observation with little emphasis on explanation

When were compound microscopes used?

By the 1830s

Describe the apparatus of the compound microscope

Had two lenses

Both magnification and resolution were improved

Structures only 1 micrometer in size could be seen clearly

What applies to Cell Theory?

All organisms can be applied to cell theory

How did Robert Brown identify the nucleus?

Using a compound microscope, he identified as a structure inside plant cells.

What did Matthias Schleiden and Thomas Schwann conclude about plant and animal tissue?

That they’re all composed of cells.

What is cell theory?

All organisms consist of one or more cells, the cell is the basic unit of structure for all organisms, and that all cells arise only from preexisting cells

Study of the Cytology:

Focuses mainly on cellular structure and emphasizes optical techniques

The Study of Biochemistry:

Focuses on cellular structure and function

The Study of Genetics:

Focuses on information flow and heredity and includes sequencing of the entire genomes (all of the DNA) in numerous organisms

What does the cytological strand (cytology) deal with?

Primarily cellular structure and observation using optical techniques

True or false 1: Microscopy has been invaluable (extremely useful) in helping cell biologists dela with the problem of small size of cells and their components

true 1

True or false 2: The unit used to measure cells and organelles may not be familiar

true 2

Micrometer

also called the micron, is one millionth of a meter (10-6 m)

How big are bacterial cells compared to plant and animal cells?

Bacteria - few micrometers in diameter

Plants and animals - 10-20 times larger than bacterial cells

Organelles are:

comparable to bacterial cells in size

Nanometer is used for:

molecules and subcellular structures that are too small to be seen using the light microscope

Nanometer

one billionth of a meter (10-9 m)

The light microscope was the earliest tool of cytologists, what did it allow identification of?

nuclei, mitochondria, and chloroplasts within cells.

Light microscopy is also called…

brightfield microscopy because white light is passed directly through a specimen.

Brightfield microscopy samples are:

dead, fixed, and stained. The preparation process can introduce distortions not typical to living cells.

What can only be seen with an electron microscope?

viruses, ribosomes, proteins, dna, lipids, small molecules, and atoms.

A variety of special optical techniques have been developed for observing living cells directly. These include:

Phase-contrast microscopy

Differential interference contrast microscopy

Fluorescence microscopy

Confocal microscopy

Phase contrast and differential interference contrast microscopy make it possible to?

see living cells clearly

The phase of transmitted light:

changes as it passes through a structure with a different density from the surrounding medium.

Phase contrast and differential interference contrast microscopy do what to these slight changes?

enhance and amplify

Fluorescence microscopy allows for what?

Detection of proteins, DNA sequences, or molecules that have been made fluorescent by binding to antibodies.

What is an antibody?

A proteins that binds to a particular target molecule (antigen)

Whats an Antigen?

a target molecule for an Antibody.

Can an antibody be coupled to a fluorescent molecule?

Yes, which emits a fluorescence whenever the target molecule is bound by the antibody.

What does GFP stand for?

Green fluorescent protein, which can be used to study the temporal and spatial distribution of proteins in a living cell.

What does confocal microscopy use?

A laser beam to illuminate a single plane of a fluorescently labeled specimen.

What does digital microscopy use?

Video cameras to collect digital images.

The limit of resolution refers to:

How far apart objects must be to appear as distinct.

The smaller the microscopes limit of resolution…

the greater its resolving power is.

The resolution for a light microscope is related to..

the physical nature of light.

For visible light, the limit of resolution is about..

200-350 nanometers (nm).

The electron microscope was a major breakthrough for cell biology. What did it use instead of light?

A beam of electrons.

The limit of resolution of electron microscopes is about..

100 times better than that of a light microscope

The magnification of an electron microscope can go up to…

100,000x. This is might higher than light microscopes.

What does TEM stand for?

transmission electron microscopy, where electrons are transmitted through the specimen.

What does SEM stand for?

scanning electron microscopy, where the surface of a specimen is scanned by detecting electrons deflected from the outer surface.

What does specialized approaches in electron microscopy allow for?

The visualization of specimens in three dimensions and allow for the determination of protein macromolecular structures.

Around the same time cytologists were studying cells microscopy, other began to…

explore cellular function

What were these scientists trying to understand about biological molecules?

their function and their structure.

In 1828, Fredrich Wöhler showed that..

a compound made in a living organism could be synthesized in the lab.

What was thought about living organisms prior to 1828?

That they were unique and not governed by the laws of physics and chemistry.

Louis Pasteur in the 1860s showed that…

yeasts could ferment sugar into alcohol.

The Buchners in 1897 showed that…

yeast extracts could also ferment sugar into alcohol.

What two events led to the discovery of enzymes, which are biological catalysts?

The demonstration of fermentation from yeast and yeasts extracts in the 1860s and 1897.

The steps of the pathways of fermentation and other cellular processes were elucidated (explained) during what time periods?

The 1920s, 1930s, and 1940s.

Gustav Embden, Otto Meyerhof, Otto Warbur, and Hans Krebs described what?

The steps of glycolysis (also known as the Embden-Meyerhof pathway) and the Krebs cycle.

Fritz Lipmann showed that..

adenosine triphosphate (ATP) is the principal energy storage compound in most cells.

Who explained the calvin cycle?

Melvin Calvin

Subcellular fractionation

Uses centrifugation to separate/isolate different structures and macromolecules

Ultracentrifuges

are capable of very high speeds (over 100,000 revolutions per minute)

Chromatography

techniques to separate molecules from a solution based on size, charge, or chemical affinity.

Electrophoresis

Uses an electrical field to move through proteins, DNA, or RNA molecules through a medium based on size/charge.

Mass spectrometry

used to determine the size and composition of individual proteins.

The genetic strand is…

used to study the inheritance of characteristics from generation to generation.

It was not until the nineteenth century that scientists discovered what?

The nature of inherited physical entities, or genes.

Gregor Mendel’s experiments with peas in 1866 laid the foundation for the understanding of what?

The passage of hereditary factors from parents to offspring.

What are hereditary factors also known as?

Genes

Walther Flemming in 1880 saw threadlike bodies in the nucleus which are now called..

chromosomes.

What did scientists call the process of cell division?

mitosis.

What did Wilhelm Roux and August Weismen in 1883 suggest?

That chromosomes carried genetic material.

What is chromosome theory?

Mendel’s hereditary factors are located on chromosomes.

What specimen was used to connect specific traits to specific chromosomes?

the common fruit fly, drosophila melanogaster.

What did Freidrich Miescher in 1869 do to DNA and what did he call it?

He isolated it and called it nuclein.

DNA was known for a lot of things:

• To be a component of chromosomes by 1914

• To be composed of only for different nucleotides by the 1930s

• Proteins, composed of 20 different amino acids, were thought more likely to be genetic material.

What is the one gene-one enzyme concept?

That each gene is responsible for the production of a single protein

What type of experiments began to implicate DNA as genetic material?

Experiments regarding bacteria and viruses in the 1940s.

When was the double helix model for DNA structure proposed?

1953, from Watson and Crick along with Rosalind Franklin.

What advances were made to understand what in the 1960s?

DNA replication, RNA production, and the genetic code.

mRNAs (messenger RNAs)

translated to produce protein

rRNAs (ribosomal RNAs)

components of ribosomes

tRNAs (transfer RNAs)

bring the appropriate amino acids for protein synthesis

What are the exceptions to the central dogma?

Viruses with RNA genomes.

Reverse transcriptase is..

and enzyme that uses viral RNA to synthesize complementary DNA.

What is the Central Dogma?

1. DNA replication - Nuclear DNA is fully copied one time in each cell division

2. Transcription - Nuclear DNA directs the synthesis of specific mRNA molecules

3. Translation - A ribosome synthesizes the protein encoded by the mRNA

How was CRISPR discovered?

As a prokaryotic defense against viral infection, then was used as a tool for genome editing.