[Biology 1002B] - Final Exam Guide - Comprehensive Notes for the exam (83 pages long!)

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29 Nov 2016
Department
Professor
Western
Biology 1002B
FINAL EXAM
STUDY GUIDE
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Biology 1002B Notes
Cycle 1: Trapping Light for Energy and Information
Characteristics of Chlamydomonas that make it a
Useful Model System
Unicellular, soil-dwelling green alga with
multiple mitochondria, two anterior flagella for
motility and mating, an eyespot, and a
chloroplast that houses the photosynthetic
apparatus and critical metabolic pathways
Reflects basic eukaryotic structure
Reproduces and grows rapidly, so lots of them
can be grown quickly
Normally haploid, so mutations are obvious
There is DNA in its nucleus and chloroplast
Contains both plant (chloroplasts) and animal
(flagella) traits
Ability to manipulate its genetics
Grows in the dark on an organic carbon source while maintaining a functional photosynthetic
apparatus
Relatedness of Chlamydomonas to Plants and Animals
Classified as a plant
Lineage diverged from land plants over 1 billion years ago
Genes can be traced to the green plant or plant-animal common ancestor by comparative
genomic analyses
Related to plants by having chlorophyll and being photosynthetic, related to animals by having
motility due to flagella and having an eyespot that can sense the environment which is similar to
animals
More closely related to plants due to their position on the phylogenetic tree, however they have
traits similar to animals, which is why they are a good model organism to test things on
Relationship Between Genome Size and Protein Coding Genes
No relationship because some genomes contain more junk DNA than others, meaning less
protein coding gene areas
Chlamydomonas has a small genome size but because it has less junk DNA it has a high number
of protein coding gene regions
Humans have a large genome but a lot of junk DNA and therefore less protein coding gene areas,
therefore showing no relation between the genome size and PCG #
Phototransduction from Eyespot to Flagella
Each cell contains a light sensor called an eyespot
allowing it to gather info about the location and
intensity of a light source
Cells can move toward or away from the light source,
for efficient photosynthesis
All cells are polarized (inside is -, outside is +)
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Channelrhodopsin
o Photoreceptor molecule of the eyespot
o Has a channel through which ions can move
o Opens up when light is absorbed and ions can move across the membrane
o Depolarization causes an action potential which causes the flagella to move
o Process is called phototaxis movement of an organism in response to light, either
towards or away from the source of the light
Advantages to Chlamydomonas in Being Phototactic
Light harvesting for photosynthesis
Can reduce damage from light if source is too strong, or move closer if more light is needed
Distinctions Between Primitive, Complex, Simple
Just because an organism is simple, does not mean it is primitive
Primitive organisms are earlier on in evolution
Complex organisms have specialized tissues (i.e. nerves, organs, or flowers)
Reasons why Chlamydomonas Might Move Towards a Light Source
It needs energy (which is produced from photosynthesis, therefore it needs light)
Reasons why Chlamydomonas Might Move Away From a Light Source
The light intensity is too much for the cell, so it moves away to create as minimal damage as
possible
Possible mutations that could cause a Chlamydomonas cell not to be Phototactic
Mutation which affects the section of the DNA which codes for the channelrhodopsin protein
(does not absorb light)
Mutation which causes a great depletion in the amount of channelrhodopsin receptors,
eventually ceasing the cells ability to be phototactic
Mutations in the ability for the Channelrhodopsin/plasma membrane to conduct a proper action
potential, therefore not enabling the flagella to receive the action potential, and stripping the
flagella of its ability to move
The Electromagnetic Spectrum
Defined as the range of wavelengths or frequencies of electromagnetic radiation extending from
gamma rays to the longest radio waves and including visible light
Light
Defined as the portion of the electromagnetic spectrum that humans can detect with their eyes
It is a stream of photons (photons discrete particles or packets of energy)
Has no mass
Behaves as a wave as it travels through space
Particle-Wave duality behaves as a particle (photon) and a wave
The longer the wavelength, the lower the energy of the photons it contains
Functions:
o Source of energy that sustains all organisms
o Provides organisms with info about the physical world that surrounds them
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