Week 1 Application Questions Flashcards
List the key structural differences between prokaryotic and eukaryotic cells.
Is this difference a sufficient method for classification of cells? Explain why or why not.
Eukaryote’s
(plants, fungi and animals)
• 10-100 um:
• Have a nucleus (‘karyon’) filled with DNA
• Membrane bound organelles
• Cytoskeleton
• Larger ribosomes
Prokaryotes
(Bacteria, Archaea)
• 1-10 um
• Circular, naked DNA
• No separate internal membranes (e.g. nucleus, mitochondria)
• “No cytoskeleton”
• smaller ribosomes
NO.
Today: mostly a functional differentiation but not a systematic classification.
Classification systems aim to group organisms that are more closely related together, Archaea in the prokaryotes are more closely related to eukaryotic cells than bacteria.
Today’s classification based on molecular data (sequences of rRNA), as suggested by R. Woese et al.
Describe the cellular properties that you would expect to observe in the Last Universal Common Ancestor (LUCA).
To which Domain would the LUCA belong?
Which techniques would you use to figure this out?
• Membrane; DNA; information transfer DNA, RNA to protein, ribosomes, proteins as structural and catalytic molecules, ATP, glycolysis
• Should not have properties that characterizes only one group like organelles, peptidoglycan
• Belong to none as this diversification happened after
• Electron microscopy and DNA sequencing
— compare genes for a structure that exists in all cells and changes slowly but steadily and is large enough, e.g. DNA strands that encode parts of the ribosomes. All cells have ribosomes, but there is some variation
The virus responsible for COVID-19 disease is an extremely small particle consisting of a core of RNA surrounded by a protein coat and a lipid envelope (see fig 1). It is unable to produce ATP, multiply or express its genes outside a host cell as it requires host cell enzymes to aid RNA replication and translation. (Based on definition in Henderson’s Dictionary of Biology; E. Lawrence, ed., 2016)
Based on the course material, would you classify this virus as alive?
Which of the 7 properties of life are applicable to the virus? Are there any ones that are not applicable, if yes, which ones?
Do you think this should be a new domain in our Tree of Life or could this be the LUCA?
• No do not think it’s alive.
———————————————————
Have:
• have different levels of organization,
• adapt to environment (evolve),
• reproduce (as in replicate inside host cell)
They do not have:
• metabolism
• their own energy processing (metabolism),
• homeostasis,
• growth and development
Maybe:
• response to the environment, irritability, cannot reproduce without a host
• They possess genes, they evolve by natural selection, reproduce by creating multiple copies through self-assembly
———————————————————
•Depends on previous answer: if they are not alive, the should not be on the Tree of Life.
• If this is a very different and specialized form of life, it should be in a different domain.
• If this is some kind of ancestral form of life, it predates LUCA, since it is not a full cell… misses some of the structures (ribosomes, ATP, glycolysis, …
In the video for Topic 1.4 Science and Experimental Design, you were asked to write your own a hypothesis for the sitting is the new smoking study. Write down your hypothesis and clearly mark the different elements: a more general hypothesis, the mechanism or explanation (‘because’) and the prediction with the dependent and independent variables (‘then’).
Prolonged periods of sitting result in decreased health because of increased blood pressure and instructors who sit during lectures will take more (increased) more medication to lower blood pressure.
General hypothesis: underlying biological mechanism or explanation, prediction, variables
Controlled variables: age 25+
