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Biology 1002B Study Guide - Midterm Guide: Psychrophile, Rubisco, Flavin Mononucleotide


Department
Biology
Course Code
BIOL 1002B
Professor
Denis Maxwell
Study Guide
Midterm

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1002Bio Lecture Outcomes
Collective Note on Google Docs: http://bit.ly/1ANmFUr
Lecture 1: Introduction to the Chlamydomonas
Readings: Section 1.1 in Biology: Exploring the Diversity of Life, 2nd Ed. Check out Fig. 1.1.
-Light is a source of energy that directly or indirectly sustains virtually all organisms
-It also provides organisms with information about the physical world around them
-Light from sun reaches Earth in just under 8 minutes (travelling at approximately 1.8 x 109 km/h)
-Humans can only detect 400nm – 700nm (visible light spectrum)
-Energy and wavelength are inversely proportional
-Light composed of waves of photons: particle-wave duality is observed
-Reflected, absorbed or transmitted through the object: the 3 fates of light when hitting an object
-When absorbed, it can be used as a source of energy or information
oOccurs when the energy of a photon is transferred to an electron within a molecule
oEnergy of light must exceed energy difference between electrons ground and excited states
-Pigments: major class of molecules that are very efficient at absorbing photons
oCritical feature: a conjugated system (region where carbon atoms are covalently bonded to each
other with alternating single and double bonds)
oThis results in the delocalization of electrons
oNone of these electrons are closely associated with any atom or involved in bonding
oThis allows them to interact with a photon of light
oMost pigments absorb distinctly different wavelengths due to difference in available excitable
electrons; wavelength that is not absorbed is the colour that we see for that object
1. Locate the eyespot on an image of Chlamydomonas.

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2. Characteristics of Chlamydomonas that make it a useful model system
-Each cell contains a single, large chloroplast that harvests light energy and uses it to make energy-rich
molecules through the process of photosynthesis
-Eyespot to gather information through location and intensity of light sources
-Is 10 microns in length, whereas bacteria is generally 1 micron and the average human cell is roughly
100 microns in length
-Simple lifecycle in addition to a relatively simple genome; makes it easy to study
-First organism in evolutionary history to combine a sense with movement (eyespot/flagella)
-Mutants easily isolated; Chlamy species usually haploid – making effects of mutations immediately
recognizable without further crossing

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3. Relatedness of Chlamydomonas to plants and animals
-Domain: Eukaryote (which includes plants, animals and protists)
-Kingdom: Debated, however currently it is officially classified under Protist. Traditionally, the division
Chlorophyta (green algae) is part of the kingdom of Protista.
-Chlamy would eventually branch out to plants: Crei/Otau, but cannot be classified as a plant
-Shares many similarities with fungi and animals in ways that plants do not
-Has both sexual and asexual life cycle
oUnder environmental stress, they can switch on a whole set of genes and function as gametes
(sexual reproduction) as opposed to their regular asexual method
4. Relationship between genome size and protein coding genes
E.Coli Chlamy H. Sapiens
Genome 4 Mb 120 Mb 3,000 Mb
PCG 4,000 15,000 20,000
-We are so much larger (multicellular organism) and complex (but remember that genome size does not
directly entail such a relationship)
oYet, we only have 5,000 more protein coding genes
-Humans carry a lot of junk DNA, having less PCG regions, regardless of our large genome
-More genes does not link to an increase in complexity (“C-value enigma”)
-Multicellularity:
oVolvox & Chlamy are very similar, however, Volvox is a multicellular organism
oThis allows us to find a point in which multicellularity developed in organisms
5. Phototransduction from eyespot to flagella
-Plasma Membrane: is POLARIZED (outside +, inside -). Maintained by protein pumps
Channelrhodopsin – a membrane bound pore or “channel”: only seen in the eyespot – opens up during
the absorption of light (conformational change)
oAllows ions to move into membrane (+ goes into – environment) to cause depolarization
oCalcium and hydrogen ions travel into cell, creating action potential
oSimilar to process of neuron; potential moves from eyespot to flagella
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