Molecular Biology Exam queries and
answers graded A+
What features distinguish the 3 domains of life, and how were eukaryotic cells thought to originate?
- ANS✅✅Prokaryotes: no nucleus
Eukaryotes: single cell or multicellular
Bacteria: for energy production
Archaea: for information of molecules (RNA, histones)
Endosymbiosis: progenitor engulfed; where one organism lives inside the other. The original
internalization of prokaryotes by an ancestral eukaryotic cell forming mitochondria & chloroplasts.
What are typical sizes and volumes for different types of cells? - ANS✅✅Bacteria: Radius; 0.5-1
micrometer; Volume; 1 femtoliter
Archaea : Radius; 2.5 micrometer; Volume; 60 femtoliters
Eukaryote: Radius; 25 micrometer; Volume; 5000 femtoliters
What are the key microscopy concepts that are relevant for visualizing cells and intracellular
structures? - ANS✅✅Magnification: increase in size
Resolution: minimum distance b/w objects that can be resolved
Light Microscopy: d=0.2 micrometers
Electron Microscopy: d=2 nanometers
Contrast: difference b/w object and background
What are the key types of molecules relevant to cell biology, and how common is it that they
interact with each other? - ANS✅✅Nucleic Acids (RNA, DNA)
Proteins & protein complexes
Lipids
MANY interactions between them
Advantages of Compartmentalization & Organization - ANS✅✅- Provide distinct
microenvironments (ex: low pH in lysosome)
- Sequester harmful molecules
- Concentration specific molecules
, - Enable regulation
- Increased membrane surface area
How many of each type of molecule are present in a simple cell, and how crowded with molecules is
the cell interior? - ANS✅✅- Water: 2x10^10
- mRNA: 2x10^3
-Membrane Protein: 10^6
-Ribosome: 2x10^4
-Inorganic ion: 6x10^7
-DNA: 5x10^6 bp
-Lipid: 2x10^7
-Protein: 2x10^6
What techniques do cell biologists use to localize specific molecules in cells? - ANS✅✅- Use
fluorescent microscopy; creates fluorophores
- Green fluorescent protein (GFP)
*Emission wavelength is longer than excitation wavelength*
What are the three major types of lipids that make up cell membranes? - ANS✅✅-
Phosphoglycerides: charged, contains double bond
- Sphingolipids
- Cholesterol: bc it's rigid increases stiffness and reduces fluidity
Why do cellular lipids spontaneously form bilayers? - ANS✅✅They spontaneously form lipid
bilayers because of the shape and amphipathic nature of lipids
How do lipids behave in cellular membranes - are they generally ordered or disordered, are they
fluid? - ANS✅✅Bilayers are disordered and fluid
What is FRAP and how can FRAP be used to observe the fluid movement of membrane proteins in
membranes? - ANS✅✅- Fluorescence recovery after photobleaching
Steps
1. Express GFP-tagged protein
answers graded A+
What features distinguish the 3 domains of life, and how were eukaryotic cells thought to originate?
- ANS✅✅Prokaryotes: no nucleus
Eukaryotes: single cell or multicellular
Bacteria: for energy production
Archaea: for information of molecules (RNA, histones)
Endosymbiosis: progenitor engulfed; where one organism lives inside the other. The original
internalization of prokaryotes by an ancestral eukaryotic cell forming mitochondria & chloroplasts.
What are typical sizes and volumes for different types of cells? - ANS✅✅Bacteria: Radius; 0.5-1
micrometer; Volume; 1 femtoliter
Archaea : Radius; 2.5 micrometer; Volume; 60 femtoliters
Eukaryote: Radius; 25 micrometer; Volume; 5000 femtoliters
What are the key microscopy concepts that are relevant for visualizing cells and intracellular
structures? - ANS✅✅Magnification: increase in size
Resolution: minimum distance b/w objects that can be resolved
Light Microscopy: d=0.2 micrometers
Electron Microscopy: d=2 nanometers
Contrast: difference b/w object and background
What are the key types of molecules relevant to cell biology, and how common is it that they
interact with each other? - ANS✅✅Nucleic Acids (RNA, DNA)
Proteins & protein complexes
Lipids
MANY interactions between them
Advantages of Compartmentalization & Organization - ANS✅✅- Provide distinct
microenvironments (ex: low pH in lysosome)
- Sequester harmful molecules
- Concentration specific molecules
, - Enable regulation
- Increased membrane surface area
How many of each type of molecule are present in a simple cell, and how crowded with molecules is
the cell interior? - ANS✅✅- Water: 2x10^10
- mRNA: 2x10^3
-Membrane Protein: 10^6
-Ribosome: 2x10^4
-Inorganic ion: 6x10^7
-DNA: 5x10^6 bp
-Lipid: 2x10^7
-Protein: 2x10^6
What techniques do cell biologists use to localize specific molecules in cells? - ANS✅✅- Use
fluorescent microscopy; creates fluorophores
- Green fluorescent protein (GFP)
*Emission wavelength is longer than excitation wavelength*
What are the three major types of lipids that make up cell membranes? - ANS✅✅-
Phosphoglycerides: charged, contains double bond
- Sphingolipids
- Cholesterol: bc it's rigid increases stiffness and reduces fluidity
Why do cellular lipids spontaneously form bilayers? - ANS✅✅They spontaneously form lipid
bilayers because of the shape and amphipathic nature of lipids
How do lipids behave in cellular membranes - are they generally ordered or disordered, are they
fluid? - ANS✅✅Bilayers are disordered and fluid
What is FRAP and how can FRAP be used to observe the fluid movement of membrane proteins in
membranes? - ANS✅✅- Fluorescence recovery after photobleaching
Steps
1. Express GFP-tagged protein
