Chapter 1: Introduction Flashcards
Discovery of Cells Basic Properties of Cells Two Fundamentally Different Classes of Cells Viruses
How did the study of cell and molecular biology come about?
Attributed to human curiosity and human creative intelligence
Microscope
instrument that provides a magnified image of a tiny specimen
Robert Hooke
Credited with the discovery of cells - observed cork and examined empty cell walls of dead plant tissue - had a position as a curator of the Royal Society of London
Anton van Leeuwenhoek
First to describe bacteria - constructed a simple microscope of remarkable quality - observed “animalcules” in pond water
What is the smallest living organism and its approximate size?
Mycoplasma sp.
0.2 micrometer diameter
Enumerate 4 inventions/techniques created that helped enable the study of cell and molecular biology and what it accomplishes
Polymerase Chain Reaction (PCR): amplifies DNA fragments
Spectrophotometer: quantify DNA or protein extracted from a cell
Electrophoresis: separation of nucleic acids or proteins based on molecular weight
Flow Cytometer: count number of cells/chromosomes
How big is the genome of prokaryotes?
Fewer than 500 genes
Enumerate the types of microscopes
Compound Light Microscope: for viewing objects with higher magnification, not as detailed
Scanning Electron Microscope: for visualization of external structures in detail
Transmission Electron Microscope: for visualization of internal structures in detail
Matthias Schleiden
Observed that plants are made of cells
Concluded that the plant embryo arose from a single cell
Theodor Schwann
Published a comprehensive report on the cellular basis of animals
Proposed 2 tenets of the cell theory:
1) All organisms are composed of one or more cells
2) Cells are the basic structural unit of life
Rudolf Virchow
Cells can only arise from pre-existing cells
What was the first culture of human cells grown and who grew it?
HeLa cells: obtained from a malignant tumor
Researchers: George and Martha Gey
Donor: Henrietta Lacks
TRUE OR FALSE
in vitro: within the body:: in vivo: outside the body
FALSE
in vitro refers to cells that are grown outside the body in an artificial medium
in vivo refers to cells within the body
What are the basic properties of cells?
- Highly complex and organized
- Possess a genetic program and the means to use it
- Capable of producing more of themselves
- Acquire and utilize energy
- Carry out a variety of chemical reactions
- Ability to respond to stimuli
- Capable of self-regulation
- Evolve
What does it mean to be highly complex and organized?
[COPC]
Complex: greater number of cellular structures
Organized: cellular structures all have proper places within the cell
Highly precise & more regulation: less tolerance of errors in interaction of parts
Consistent: organelles have the same shape, same location, and same composition of macromolecules arranged in a predictable pattern across different cells
What is the advantage of evolution proceeding slowly at the level of cells?
Information obtained from cells in one type of organism usually has a direct application to another organism
Give an example demonstrating the complexity and organized nature of cells
Epithelial cells: line the intestine and facilitate absorption of nutrients
- have microvili that contain internals skeletons made up of filaments
- filaments are made up of actin
- have mitochondria at the basal end: provides energy to fuel transport processes
Where is the genetic information of cells stored and what are the means by which it is used?
Found in the chromosomes.
Enables the construction of cellular structures
Directs cellular activities
Guides reproduction of a cell
Mutations provide the basis for biological evolution.
How do cells reproduce?
Division wherein each daughter cells receives a complete set of genetic information from the parent cell
Differentiate between how plant cells (photosynthetic) acquire energy and how animal cells do
Photosynthetic cells capture light energy and through photosynthesis, convert this to chemical energy
Animal cells have energy pre-packaged in glucose
How do human cells acquire and utilize energy?
Glucose is released into the bloodstream via the liver where it circulates throughout the body delivering chemical energy to all the cells where it is broken down into a readily available form or energy: ATP
These are the molecules that enable chemical reactions to proceed faster
Enzymes
The sum total of all the chemical reactions in a cell
Metabolism
Enumerate the mechanical activities cells engage in
- Transport of cellular materials
- Assembly and disassembly of cellular structures
- The entire cell moves
How do the mechanical activities that occur in the cell proceed?
Changes in the shape of motor proteins and other molecules
_____ provide pathways through which external stimuli can evoke specific responses within target cells
Receptors
Enumerate the ways in which a cell responds to external stimuli
- Alteration of metabolic activities
- Moving
- Committing suicide (Apoptosis)
What is the importance of cell turnover?
Maintains the integrity of organelles and macromolecules
Ligands
Signal molecules received by the cells receptors that illicit a response
TRUE or FALSE
The robustness of a cell means it is able to protect itself from dangerous fluctuations in composition and behavior
True
What is the importance of self-regulation in a cell? Provide an example
In the event that a mistake is made during DNA replication, if the feedback circuits do not correct the mistake this could lead to a debilitating mutation such as the breakdown of the growth-control safeguards that would then lead the cell to become a cancer cell.
What is self-regulation in a cell?
The spontaneous occurrence of each step of a process within cell that serves as a trigger for the next step
LUCA
Last Common Universal Ancestor from which all cells arose from
What is evolution?
Evolution is the on-going process wherein the properties of cells continue to be modified as external and internal factors change
Enumerate the common features between prokaryotic and eukaryotic cells?
- Plasma membrane of similar construction
- Genetic information encoded in DNA using an identical genetic code, located in the nuclear region
- Similar mechanisms for transcription and translation and similar ribosomes
- Shared metabolic pathways
- Similar apparatus for conservation of chemical energy in the form of ATP
- Similar mechanism of photosynthesis
- Similar mechanisms for synthesizing and inserting membrane proteins
- Proteasomes of similar construction
Explain how eukaryotic and prokaryotic organisms, being two fundamentally different classes, can have shared properties?
The shared properties between the two indicate that eukaryotes evolved from prokaryotes which lines up with the idea that all cells arose from a single cell (LUCA)
Compare and contrast the nuclear region of prokaryotes and eukaryotes
Prokaryotes: nucleoid - lacks a boundary membrane
Eukaryotes: nucleus - bounded by the nuclear envelope
Describe the plasma membrane structure
Semi-permeable phospholipid bilayer made up of hydrophilic glycerol heads and hydrophobic fatty acid tails
Compare and contrast the DNA-containing chromosomes of prokaryotes and eukaryotes
Prokaryotes: single circular chromosome
Eukaryotes: numerous separate chromosomes containing a single linear DNA tightly associated with histones to form chromatin
Enumerate some features of eukaryotic cells that are not found in prokaryotic cells
- Separation of the cell into cytoplasm and nucleus by way of the nuclear envelope
- Complex chromosomes composed of DNA and histones that are capable of compacting into mitotic structures
- Complex membranous organelles in the cytoplasm
- Specialized cytoplasmic organelles for aerobic respiration and photosyntheis
- Complex cytoskeletal system and motor proteins
- Complex flagella and cilia
- Ability of phagocytosis
- Cellulose-containing cell walls in plant cells
- Cell division involving a mitotic spindle that separates chromosomes
- Presence of two copies of genes per cell
- Presence of 3 different RNA polymerases
- Sexual reproduction requiring meiosis and fertilization
Compare and contrast the mechanism for translation and transcription between prokaryotes and eukaryotes
Both: same mechanisms for translation and transcription
Prokaryotes: translation occurs in the cytoplasm
Eukaryotes: translation occurs in either the cytoplasm or the ribosomes attached to the rough ER
What are some of the membranous organelles found in the cytoplasm of eukaryotes?
Mitochondria Golgi complexes Endoplasmic reticulum Lysosomes Endosomes Peroxisomes
TRUE or FALSE
All prokaryotic organisms are devoid of cytoplasmic membranous organelles
FALSE
Cyanobacteria is an exception to this because of the presence of complex photosynthetic membranes
TRUE or FALSE
ATP is synthesized in the mitochondria for both prokaryotes and eukaryotes
FALSE
Prokaryotes: Do not have mitochondria, ATP is synthesized in the cell membrane
Eukaryotes: Yes
What is the function of proteasomes and how is it carried out?
Digest non-functional proteins via ubiquitination - process of tagging obsolete proteins with ubiquitins for the proteasomes to identify and digest via enzymes
What are the two metabolic pathways shared by prokaryotes and eukaryotes?
Glycolysis and Tricarboxylic acid cycle
What are examples of organisms in domain Archaea?
Halophiles: salty conditions
Methanogens: capable of producing methane
Thermophiles: extreme temperature conditions
Acidophiles: acid-loving
What organism is the most complex under eukaryotes and why is it so?
Protists are the most complex because all the complex activities in which the organism engages in are confined within a single cell
How does differentiation occur? Give examples of differentiated cells
Differentiation is determined by the specific signals received by the cell from the environment
- Skeletal muscle cells
- Red blood cells
- Cartilage cells
Name common model organisms used in cell and molecular biology
- Arabidposis thaliana - mutations
- Mus musculus
- Zea mays - transposons
- Caenorhabditis elegans - human diseases
- Escherichia coli - molecular biology of the cell
- Saccharomyces cerevisiae - identification of genes through mutants
- Danio rerio - sex determination, animal development
- Drosophila melanogaster - genetic mutation, animal development, neurobiology of simple behavior
What is the importance of cell differentiation?
Cell differentiation allows certain cells to perform specific tasks vital to the life of an organism
What unit of measure is used to measure macromolecules
Angstrom (A) or nanometer (nm)
Give the measurements of the ff:
- Myoglobin
- Collagen
- DNA
- Ribosomes, microtubules, microfilaments
- 4.5 x 3.5 x 2.5 nm
- over 100nm
- 2.0nm diameter
- 5-25nm diameter
What is the reasoning behind the small size of cells?
If the cell were too large…
a) Longer synthesis of cellular messages
b) Smaller surface area - might not be enough to support substances necessary for metabolic activites
c) Increased distance between interior and exterior of the cell = diffusion will become prohibitively long
Why do cells in the body need to be replaced?
Diseases are a result of the death of specific cells
How did the following diseases arise?
- Type 1 diabetes
- Parkinsons disease
- Heart failure
- Death of beta cells (responsible for insulin production) in the pancreas
- Loss of dopamine-producing neurons
- Death of cardiomyocytes
How are lymphomas and leukemia treated? What is the rationale behind this?
Bone Marrow Transplantation
Bone marrow contains hematopoietic cells that are capable of proliferate and restock RBC and WBC
What are the types of therapy under cell replacement?
- Adult Stem Cell
- Embryonic Cell
- Induced Pluripotent Stem Cells
- Direct Cell Reprogramming
Stem cells
Undifferentiated cells that are capable of self renewal and are multipotent
These cells are capable of replacing the cells of the tissue from which they are found in
Multipotent
Ability to differentiate into two or more mature cell types
Name 3 examples of stem cells
- Hematopoietic stem cells
- Satellite cells (adult skeletal muscle cells)
- Cardiomyocytes (cells found in heart muscle tissue and blood cells in the heart)
Who were responsible for the discovery of HSCs
James Till & Ernest McCulloch
Autologous treatment
An advantage of adult stem cell therapy wherein the risk of immune rejection is removed because the donor of the cells is also the patient receiving the cells
What are some disadvantages of adult stem cell therapy?
- Not easy to isolate stem cells
- Stem cells usually only replace the cells of the tissue in which they are found
- Scarcity of stem cells
Differentiate between adult stem cells and embryonic stem cells
Adult Stem Cells: Multipotent
Embryonic Stem Cells: Pluripotent
What are embryonic stem cells?
Undifferentiated cells retrieved from young mammalian embryos that give rise to all the structures of a mammalian fetus
Pluripotent
Capable of differentiating into all types of cells
What were the injuries/disorders first addressed in human trials for embryonic stem cells?
debilitating spinal injuries
Stargardt’s muscular dystrophy
Where are embryonic stem cells usually obtained from?
in-vitro fertilization clinics provide embryonic stem cells from human embryos
Oligodendrocytes
cells forming the myelin sheath that wraps around the nerve cells
What does the culture for oligodendrocytes contain?
Insulin, thyroid hormone, and other growth factors
What are the disadvantages of ES cell therapy?
- risk of immunologic rejection
- teratoma formation
- use of non-human biological materials
Teratoma
benign tumor w/ a mass of various differentiated cells
What is the purpose of Somatic Cell Nuclear Transfer (SCNT)?
To reduce the risk of immunologic rejection by customizing the ES cells to have the same genetic makeup as the recipient
How is the process of SCNT?
Nucleus of an unfertilized egg is replaced with the nucleus from a cell of the patient
What are the disadvantages of SCNT?
- Expensive
- Highly-demanding
- Ethical problems
Induced Pluripotent Stem Cells (iPS)
Pluripotent stem cells that had been induced to be so from a previous state of differentiation
How did Shinya Yamanaka create iPS?
Introduced the OSKM genes into a differentiated cell
OSKM genes
Encode for the proteins characteristic of ES cells that maintain the cells in an undifferentiated form and allow them to self renew
Oct4
Sox2
Klf4
Myc
List the advantages and disadvantages of iPS cells
Advantages:
1) does not require an embryo as the source of cells
2) easier to generate personalized iPS cells
Disadvantages:
1) exhibit genetic abnormalities (presence of extra copies and random segments of genes)
2) contain traces of the original cell
3) may give rise to teratoma formation
4) may stimulate an immune attack
Directed Cell Reprogramming/Transdifferentiation
Transformation of one differentiated cell into another without the pluripotent stage
How is transdifferentiation made possible?
Cells are forced to express genes that normally play a role in the embryonic formation of another differentiated cell
Give an example of directed cell reprogamming
Acinar cells being directly converted into pancreatic beta cells
TRUE or FALSE
Adenoviruses used to transport the genes needed to transform acinar cells into beta pancreatic cells remained a part of the final recipient cell
False
Virion
Virus living outside a host cell; incapable of reproduction
What are the characteristics of a virus?
- Obligatory intracellular parasite
2. Contains a single nucleic acid (RNA or DNA) encapsulated within the capsid (protein coat)
Bacteriophages
Viruses that affect bacterial cells; most abundant biological entity
TRUE or FALSE
Viruses are living organisms
FALSE
Viruses are not considered to be living organisms because they cannot reproduce or metabolize without a host cell
Retrovirus
Virus containing RNA
Can undergo reverse transcription by the enzyme reverse transcriptase
Compare and contrast the two types of viral infection
- Lytic infection - virus redirects the cells normal synthetic activities to utilize its materials for the formation of more virions
- Integration - does not lead to the death of the host cell but inserts its DNA into the host’s chromosomes (Provirus)
What are the applications of using viruses in research?
- tool to study the mechanism of DNA replication and gene expression
- means of introducing foreign genes into human cells
- against insect pests and bacterial pathogens
