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Questions and Answers
What is the role of mRNA in the process of transcription?
What is the role of mRNA in the process of transcription?
- To unwind the DNA molecule
- To carry genetic information from the nucleus to the cytoplasm (correct)
- To encode specific proteins
- To synthesize complementary strands of DNA
During translation, what forms the translational complex?
During translation, what forms the translational complex?
- Free amino acids and nucleotides
- Ribosomes and restriction enzymes
- DNA, RNA polymerase, and ribosomes
- mRNA, tRNA, and ribosomes (correct)
Which process involves cutting DNA at specific locations?
Which process involves cutting DNA at specific locations?
- DNA replication
- DNA transformation
- DNA sequencing
- Recombinant DNA technology (correct)
What does DNA cloning aim to achieve?
What does DNA cloning aim to achieve?
Which tool is primarily used in DNA sequencing to determine base sequences?
Which tool is primarily used in DNA sequencing to determine base sequences?
What did Robert Hooke first observe that led him to coin the term 'cells'?
What did Robert Hooke first observe that led him to coin the term 'cells'?
Which of the following limitations hindered early cell biology?
Which of the following limitations hindered early cell biology?
What advancement was made by using compound microscopes in the 1830s?
What advancement was made by using compound microscopes in the 1830s?
What aspect did Robert Brown's observations with the microscope primarily focus on?
What aspect did Robert Brown's observations with the microscope primarily focus on?
Which of the following contributed to the development of modern cell biology?
Which of the following contributed to the development of modern cell biology?
What was the primary focus of cell biology in its early days?
What was the primary focus of cell biology in its early days?
Which of the following structures was identified by Robert Brown using microscopy?
Which of the following structures was identified by Robert Brown using microscopy?
How did Robert Hooke's observations differ from later studies in cell biology?
How did Robert Hooke's observations differ from later studies in cell biology?
What is the main function of antibodies in fluorescence microscopy?
What is the main function of antibodies in fluorescence microscopy?
Which microscopy technique utilizes a laser beam to illuminate a specific plane of the specimen?
Which microscopy technique utilizes a laser beam to illuminate a specific plane of the specimen?
How does the limit of resolution vary between light microscopy and electron microscopy?
How does the limit of resolution vary between light microscopy and electron microscopy?
What is the resolution limit for a standard light microscope?
What is the resolution limit for a standard light microscope?
What characteristic of brightfield microscopy affects the accuracy of living cell representation?
What characteristic of brightfield microscopy affects the accuracy of living cell representation?
In which microscopy technique are electrons transmitted through the specimen?
In which microscopy technique are electrons transmitted through the specimen?
What does the resolving power of a microscope refer to?
What does the resolving power of a microscope refer to?
Which of the following objects can be observed using light microscopy?
Which of the following objects can be observed using light microscopy?
What is a primary advantage of phase-contrast and differential interference contrast microscopy?
What is a primary advantage of phase-contrast and differential interference contrast microscopy?
Which of the following statements about green fluorescent protein (GFP) is true?
Which of the following statements about green fluorescent protein (GFP) is true?
At what scale can ribosomes be observed?
At what scale can ribosomes be observed?
What does scanning electron microscopy (SEM) detect?
What does scanning electron microscopy (SEM) detect?
Which aspect of microscopy is not effective for observing very small structures like proteins and DNA?
Which aspect of microscopy is not effective for observing very small structures like proteins and DNA?
What defines the resolving power of the electron microscope compared to the light microscope?
What defines the resolving power of the electron microscope compared to the light microscope?
Which of the following microscopy techniques does not require staining of samples?
Which of the following microscopy techniques does not require staining of samples?
How does an increase in object density affect light microscopy?
How does an increase in object density affect light microscopy?
What is one of the key conclusions of the cell theory postulated by Schwann?
What is one of the key conclusions of the cell theory postulated by Schwann?
Which strand of biological inquiry focuses specifically on the chemical processes and molecular interactions within cells?
Which strand of biological inquiry focuses specifically on the chemical processes and molecular interactions within cells?
Why has microscopy been crucial for cell biologists?
Why has microscopy been crucial for cell biologists?
What is the size of a micrometer (µm) in standard metric units?
What is the size of a micrometer (µm) in standard metric units?
Which measurement unit would be appropriate for assessing the size of DNA molecules?
Which measurement unit would be appropriate for assessing the size of DNA molecules?
What addition to the cell theory was made by Virchow in 1855?
What addition to the cell theory was made by Virchow in 1855?
Which of the following is true regarding the dimensions of bacterial cells compared to plant and animal cells?
Which of the following is true regarding the dimensions of bacterial cells compared to plant and animal cells?
What is the angstrom (Ã…) primarily used for in cell biology?
What is the angstrom (Ã…) primarily used for in cell biology?
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Study Notes
Cell Biology Overview
- Cell is the basic unit of life, constantly changing
- Modern cell biology combines cytology, genetics, and biochemistry
- Fluorescence microscopy visualizes cell nuclei (red), microtubules (green), and cell-cell contacts (blue)
History of Cell Theory
- Robert Hooke (1665) first observed and named cells after compartments in cork, using a microscope
- Early progress in cell biology was hindered by limited microscope resolution and descriptive nature of studies
- Compound microscopes (1830s) improved magnification and resolution, allowing observation of structures as small as 1 µm
Development of Cell Theory
- Robert Brown discovered the nucleus within plant cells using a compound microscope
- Matthias Schleiden concluded all plant tissues are composed of cells
- Thomas Schwann made the same conclusion for animal tissues
- Schwann (1839) proposed the cell theory:
- All organisms are composed of one or more cells
- Cells are the basic structural unit of all organisms
- Virchow (1855) added to the cell theory:
- All cells come from preexisting cells
Modern Cell Biology
- Integrates three strands of biological inquiry: cytology, biochemistry, and genetics
- Cytology: focuses on cellular structure and uses optical techniques
- Biochemistry: studies cellular structure and function
- Genetics: focuses on information flow, heredity, and genome sequencing
Cellular Dimensions
- Micrometer (µm, micron): one millionth of a meter (10−6 m)
- Bacterial cells are a few µm in diameter
- Plant and animal cells are 10-20 times larger than bacteria
- Organelles are comparable in size to bacterial cells
Microscopy
- Light microscopy (brightfield microscopy):
- Earliest tool for cytologists
- Allows identification of cellular structures like nuclei, mitochondria, and chloroplasts
- Requires dead, fixed, and stained samples
- Limits of Resolution:
- The minimum distance between two objects for them to be seen as separate
- Light microscope resolution is about 200–350 nm
Specialized Light Microscopes
- Phase-contrast microscopy: enhances contrast in transparent specimens
- Differential interference contrast (DIC) microscopy: enhances contrast and creates a three-dimensional effect
- Fluorescence microscopy: detects fluorescent proteins, DNA sequences, or molecules by binding to antibodies
- Antibodies can be coupled to fluorescent molecules
- Green fluorescent protein (GFP) can be used to study protein distribution
- Confocal microscopy: uses a laser beam to illuminate a single plane of a fluorescent specimen
- Digital video microscopy: uses video cameras to capture images
Electron Microscopy
- Uses a beam of electrons for higher resolution and magnification
- Transmission electron microscopy (TEM): electrons are transmitted through the specimen
- Scanning electron microscopy (SEM): surface of the specimen is scanned by detecting deflected electrons.
- Electron microscope:
- Resolution is about 100 times better than light microscopes
- Magnification can be up to 100,000×
Working with DNA
- Recombinant DNA technology:
- Uses restriction enzymes to cut DNA at specific sites
- Creates recombinant DNA molecules from different sources
- DNA cloning: generates multiple copies of a specific DNA sequence
- DNA transformation: introduces DNA into cells
Sequencing DNA
- DNA sequencing methods determine the base sequence of DNA molecules
- Entire genomes (all DNA content of a cell) can be sequenced
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