BIOE Exam 1 Chapter 1 Flashcards
What is the central dogma of biology?
DNA => transcription => RNA => translation => Protein
When was the first cell thought to have arisen?
at least 3.8 billion years ago by the
enclosure of self-replicating RNA in a phospholipid membrane
What is metabolism?
the set of life-sustaining chemical reactions in organisms including energy conversion, biosynthesis, and waste elimination.
All cells use what as their primary energy source?
Adenosine 5’-triphosphate (ATP)
What are the three main metabolic pathways?
Glycolysis, Photosynthesis, and Oxidative Metabolism
What is glycolysis?
A metabolic pathway that breaks down glucose into pyruvate, producing ATP and NADH. Occurs in the cytoplasm
What is the purpose of photosynthesis?
To convert light energy into chemical energy (glucose) using CO₂ and H₂O. Occurs in the chloroplasts of plants
What is oxidative metabolism
The process of producing ATP through cellular respiration, using oxygen to break down glucose in the mitochondria
What are the key differences between prokaryotic and eukaryotic cells?
Prokaryotic cells: No nucleus, small, simple structure, single circular chromosome.
Eukaryotic cells: Have a nucleus, organelles, multiple linear chromosomes.
What structures do prokaryotic cells have?
Cell wall (contains peptidoglycan in bacteria, absent in archaea)
Plasma membrane (separates the cell from the environment)
Nucleoid (region where DNA is located)
Ribosomes (protein synthesis)
Bacteria and Archaea are what type of cells?
Prokaryotic ( They lack a nucleus and membrane-bound organelles
How do Bacteria and Archaea differ?
Bacteria: Have peptidoglycan in their cell walls, use formyl-methionine as the initiator tRNA.
Archaea: Lack peptidoglycan, use methionine as the initiator tRNA, have unique membrane lipids
What are the key organelles found in both plant and animal eukaryotic cells?
Both have a nucleus, mitochondria, endoplasmic reticulum, Golgi apparatus, cytoskeleton, and plasma membrane.
What unique structures are found in plant cells that are absent in animal cells?
Plant cells have a cell wall (made of cellulose), chloroplasts for photosynthesis, and a large central vacuole for storage.
What are some features unique to animal cells compared to plant cells?
Animal cells typically have lysosomes and centrosomes and lack a rigid cell wall, which allows for more flexible cell shapes.
What are the key functions of the nucleus?
Stores DNA, directs synthesis of ribosomes and proteins.
What is the role of mitochondria?
ATP production via cellular respiration.
What is the function of the endoplasmic reticulum (ER)?
Rough ER: Modifies proteins.
Smooth ER: Synthesizes lipids, detoxifies chemicals.
What is the function of the Golgi apparatus?
Modifies, sorts, and packages proteins and lipids for transport.
What are the two prokaryotic domains of life?
Archaea and
Bacteria
The evolution of
eukaryotic cells (Eukarya)
from the Archaea involved
the formation of
mitochondria by what?
endosymbiosis
What is Endosymbiosis
one cell living
inside another
What are the simplest eukaryotes?
Yeasts
(Saccharomyces cerevisiae)
What is a germ layer?
a primary layer of cells that forms
during embryonic development
What are the three primary germ layers formed during embryonic development and what do they become?
Endoderm (internal layer): Forms internal organs such as the digestive tract, lungs, and liver.
Mesoderm(middle layer): Gives rise to muscles, bones, the circulatory system, and connective tissues.
Ectoderm(external layer) : Develops into the skin, nervous system, and parts of the sensory organs.
What is cell formation during embryonic development?
Cell formation, or embryogenesis, is the process where a fertilized egg (zygote) divides and differentiates into various cell types, ultimately forming tissues and organs.
What does cell culture of animal cells allow us to do?
Study metabolic functions
What was the first Human Cell Line?
HeLa Cells, cultured from a biopsy of a cervicale cancer taken from 30 yr-old Henrietta Lacks (February 1951)
What is the 293 T Human Cell Line
an epithelial-like cell
that was isolated from the
kidney of a patient
What is the U87 Glioblastoma Human Cell Line ?
U-87 MG is a cell line with
epithelial morphology that was
isolated from malignant gliomas
from a male patient, likely with
Glioblastoma.
What are primary cell cultures?
Primary cell cultures are cells directly isolated from living tissue that are cultured in the lab for research purposes. These cells have a limited lifespan and more closely resemble cells in vivo
What is the difference between primary cells and cell lines?
Primary Cells: Directly isolated from living tissue, have a limited lifespan, and maintain closer resemblance to in vivo conditions.
Cell Lines: Cultured cells that can proliferate indefinitely, often from transformed or immortalized cells (e.g., HeLa cells). They may not accurately reflect the behavior of primary cells.
What are the advantages of using primary cells in research?
-Closer to in vivo behavior
-Better mimic human disease models
-Retain tissue-specific functions and structures
What are the disadvantages of using primary cells in research?
Limited lifespan and proliferation potential
Expensive and difficult to obtain
Variability between samples
What are the advantages of using cell lines in research?
Can be cultured indefinitely (immortalized)
Easier to maintain and handle
Provide consistency between experiments and batches
What are the disadvantages of using cell lines in research?
-Lack of tissue-specific characteristics
-May not accurately reflect in vivo cell behavior
-Can mutate over time and lose original traits
Plant cell culture has several advantages over animal cell culture. What is one main advantage?
In many instances, an entire adult plant capable of reproduction can be regenerated from cells in plant tissue culture
What is a limit of light microscopy?
It isn’t powerful enough to reveal fine details of cell structure, for which resolution
How does light microscopy work?
Light is focused on the
specimen by the
condenser lens and
then collected by the
objective lens of the
microscope
What is the refractive index of the medium used in light microscopy?
Air or oil
What are the different types of Light Microscopy?
Brightfield : Produces an image on a bright background ( used as the standard microscopy)
Darkfield: Useful for viewing live specimens. Produces a bright image on a darker background
Phase Contrast : Creates high-contrast, high-res images useful for viewing live specimen and structures such as endospores and organelles.
Differential interference contrast (DIC) : Produces high-contrast images of living organisms with 3-D appearance, useful in distinguishing structures in live-unstained specimens. Images reveal detailed structures within cells
Fluorescence : Uses fluorescent stains to produce images. Used to identify pathogens, find particular species, distinguish living from dead cells or find locations of particular molecules within cells. Used for immunofluorescence
Confocal: Uses a laser to scan multiple z-planes. Useful for examining thick specimens such as biofilms.
Two-photon: Uses scanning technique, fluorochromes and wavelength light (infrared) to penetrate into thick specimens
What causes an electron to transition to a higher excited energy state?
Excitation of a fluorophore entails absorption of light energy of a particular wavelength
What is the result after an excited electron returns to its ground state?
The emission of light at a longer wavelength.
What is DAPI ?
A DNA specific probe which forms a fluorescent complex by attaching in the minor grove of A-T sequences of DNA
What is Confocal microscopy used for?
Sharpening the focus and seeing cells deeper within living tissue
In multiphoton excitation microscopy, what is the specimen illuminated by?
A wavelength twice the excitation wavelength of the fluorophore
What does excitation of the fluorophore require?
Simultaneous absorption of two or more photons
What is the range of the super-resolution microscopy?
10-100 nm
What does Super-resolution microscopy use to improve resolution?
Fluorescent probes.
To who was the 2014 Nobel Prize in Chemistry awarded to?
Eric Betzig, Stefan Hell and William Moerner, for the development of super-resolution microscopy.
What is STORM and when was it developed?
Developed in 2006, stands for stochastic optical reconstruction microscopy. Has a resolution of 20 nm. Produces high res images by compiling individual images from thousands to millions of individual fluorescent molecules.
In Conventional fluorescence microscopy…
all of the fluorescent molecules in a
sample fluoresce at the same time resulting in a blurred image
in STORM…
only a small random fraction of the probes are fluorescent at any one time
What is the practical limit of resolution of the electron microscope?
1-2 nm
What is the main difference between SEM and TEM?
- SEM creates an image by detecting reflected or knocked-off electrons
- TEM uses transmitted electrons (electrons passing through the sample) to create an image. TEM also requires the samples to be thin while SEM doesn’t
What is subcellular fractionation?
process where cells are lysed and their components are separated using differential centrifugation.
What is the purpose of differential centrifugation?
To separate subcellular components based on their size and density through successive centrifugation steps.
What happens after each centrifugation step?
The organelles that sediment to the bottom form the pellet, while the remaining solution (supernatant) is recentrifuged at a higher speed.
What is the pellet in differential centrifugation?
It is the solid material at the bottom of the tube that contains the organelles separated by centrifugation.
How are organelles separated in differential centrifugation?
By increasing centrifugation speeds, allowing larger organelles to sediment first and smaller ones later.
How can a greater degree of purification be achieved?
By density-gradient centrifugation in which organelles are separated by sedimentation through a gradient of dense substance (sucrose)
How are subcellular components separated in density gradients?
on the basis of their buoyant density, independent of their size and shape
In equilibrium centrifugation, how is the sample centrifuged?
It is centrifuged in a gradient containing a high concentration of sucrose or cesium chloride
What occurs in velocity centrifugation?
Particles are separated based on their sedimentation rate or “velocity” in a centrifuge. Larger or denser particles will pellet first
In equilibrium centrifugation, where does sedimentation stop and where can the purified organelles be collected at?
At the equilibrium position :)
