4 Tenets of the Cell Theory
1. All living things are made of cells
2. The cell is the basic functional unit of life
3. All cells arise from pre-existing cells
4. Genetic info is carried in the form of DNA and is passed from parent to daughter cell
Briefly describe the function of the:
Nucleus
The nucleus stores genetic information and is the site of transcription.
Briefly describe the function of the:
Mitochondria
The mitochondria are involved in ATP production and apoptosis.
Briefly describe the function of the:
Lysosome
Lysosomes break down cellular waste products and molecules ingested through endocytosis, and also can be involved in apoptosis.
Briefly describe the function of the:
Rough ER
The rough ER synthesizes proteins destined for secretion.
Briefly describe the function of the:
Smooth ER
The smooth ER is involved in lipid synthesis and detoxification.
Briefly describe the function of the:
Golgi Apparatus
The Golgi apparatus packages, modifies, and distributes cellular products.
Briefly describe the function of the:
Peroxisome
Peroxisomes break down very long chain fatty acids, synthesizes lipids, and contribute to the pentose phosphate pathway.
A child is diagnosed with an enzyme deficiency that prevents the production of hydrogen peroxide. What would the likely outcome be with such a deficiency?
Peroxisomes are dependent on hydrogen peroxide for their functions, so an enzyme deficiency that results in an inability to form hydrogen peroxide would likely result in an inability to digest very long chain fatty acids. These fatty acids would build up in peroxisomes until they displaced cellular contents, ultimately resulting in cell death.
What are the predominant proteins in each cytoskeletal element:
Microfilaments
Microtubules
Intermediate filaments
Microfilaments are composed of actin.
Microtubules are composed of tubulin.
Intermediate filaments differ by cell type, but may be composed of keratin, desmin, vimentin, and lamins.
How do the cytoskeletal structures of centrioles and flagella differ?
Centrioles consist of nine triplets of microtubules around a hollow center, while flagella consist of nine doublets on the outside, with two microtubules on the inside.
Classify each of the cells as epithelial cells or connective tissue:
Fibroblasts, which produce collagen in a number of organs
Connective tissue cells
Classify each of the cells as epithelial cells or connective tissue:
Endothelial cells, which line blood vessels
Epithelial cells
Classify each of the cells as epithelial cells or connective tissue:
alpha-cells, which produce glucagon in the pancreas
Epithelial cells
Classify each of the cells as epithelial cells or connective tissue:
Osteoblasts, which produce osteoid, the material that hardens into bone
Connective tissue cells
Classify each of the cells as epithelial cells or connective tissue:
Chondroblasts, which produce cartilage
Connective tissue cells
In what ways are Archaea similar to bacteria?
Archaea are similar to bacteria in that both are single celled organisms that lack a nucleus or membrane bound organelles, contain a single circular chromosome, and divide by binary fission or budding.
In what ways are Archaea similar to eukaryotes?
They are similar to eukaryotes in that they start translation with methonine, contain similar RNA polymerases, and contain DNA associated with histones.
Three common shapes of bacteria?
spherical (cocci)
rod-shaped (bacilli)
spiral-shaped (spirilli)
What difference between the envelopes of gram-positive and gram-negative bacteria make gram-positive bacteria more susceptible to antibiotics such as penicillin?
The antibiotic penicillin targets the enzyme that catalyzes the cross-linking of peptidoglycan. Gram positive bacteria have a thick layer of peptidoglycan and lipoteichoic acid, and contain no outer membrane, whereas gram negative bacteria have only a thin layer of peptidoglycan but also have an outer membrane containing lipopolysaccharides and phospholipids. Penicillin and antibiotics with similar function can more easily reach and weaken the peptidoglycan layer of gram positive bacteria.
How do the structures in Eukaryotic and Prokaryotic flagella differ?
Eukaryotic flagella contain microtubules composed of tubulin, organized in a 9 + 2 arrangement.
Bacteria flagella are made of flagellin and consist of a filament, a basal body, and a hook.
Describe the bacterial genetic recombination mechanism:
Transformation
Transformation is the acquisition of exogenous genetic material that can be integrated into the bacterial genome.
Describe the bacterial genetic recombination mechanism:
Conjugation
Conjugation is the transfer of genetic material from one bacterium to another across a conjugation bridge; a plasmid can be transferred from F+ cells to F- cells, or a portion of the genome can be transferred from an Hfr cell to a recipient.
Describe the bacterial genetic recombination mechanism:
Transduction
Transduction is the transfer of genetic material from one bacterium to another by a bacteriophage.
What are the four phases of the bacterial growth curve & what are the features of each phase?
Lag Phase: bacteria get used to the environment; little growth
Exponential (Log) Phase: bacteria use available resources to multiply at an exponential rate
Stationary Phase: bacteria multiplication slows as resources are used up
Death Phase: Bacteria die as resources become insufficient to support the colony.
Why are viruses considered obligate intracellular parasites?
Viruses do not contain organelle such as ribosomes; therefore, in order to reproduce and synthesize proteins, viruses must infect cells and hijack their machinery.
A coronavirus, which causes the common cold, is described as an enveloped, single-stranded positive-sense RNA virus. What does this indicate about the virus?
This description indicates that the virus contains an outer layer of phospholipids with an inner capsid. Within the capsid, their is a single-stranded RNA that can be immediately translated to protein by the ribosome of the host cell.
Briefly describe the pathway of retroviral nucleic acids from infection of a host cell to release of viral progeny?
The nucleic acid enters as a single-stranded RNA, which undergoes reverse transcription (using reverse transcriptase) to form double-stranded DNA.
This DNA enters the host genome and replicates with the host cell.
The DNA is transcribed to mRNA, which can be used to make structural proteins.
This mRNA doubles as the viral genome for new virons.
Once new virons are assembled form the structural proteins and mRNA (single stranded RNA) genome, the virons can be released to infect other cells.
What are the differences between the lytic and lysogenic cycles?
In the lytic cycle, bacteriophages replicate in the host cell in extreamely high numbers until the host cell lyses and releases the virons.
In the lysogenic cycle, the bacteriophage genome enter the host genome and replicated within the host cell as a provirus. In response to an appropriate stimulus, the provirus may leave the host genome and can be used to synthesize new virons.
How do prions cause disease?
Prions cause disease by triggering a change in the conformation of a protein from an a-helix to a B-pleated sheet. This change reduces solubility of the protein and makes it highly resistant to degradation.