BIOL 1000 Lecture Notes - Thylakoid, Uracil, Phenylalanine

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31 Jan 2013
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Biology 1010
Lecture 1
Light and Life
o Light provides energy for life
o N2, H2, O2
o Must put everything into perspective (essentially must know all that’s going on around
EG Trees could hold bacteria to cure cancer etc. Notice all thats around you.
o What is masked? (if someone is colour-blind they see nothing)
o Observe how are things are different than the background
o All life depends on the sun, photosynthesis to food
o Capture sunlight and use it in different ways
o The energy is released when the bonds are broken
o Not magical radiation
o Bond breaks to allow the energy to be used somewhere else
o Takes up lots of space (large molecule therefore it moves things around when it is
placed in certain areas)
o If it binds, it moves things (due to size as well as negativity)
o It is negative therefore it will attract or repel things
o 2 different membranes (this is talking about chloroplasts)
o Chlorophyll is in the thylakoid
o Beta-carotene is VITAMIN A
o Lots of ring structures (ring structures are what absorbs light)
o Aromatic rings because of the double bonds
o Ringed carbon structures in large molecules absorb light
The light Spectrum
o Wavelength is inversely proportional to energy (λ ~ 1/Eλ)
o Violet = high energy
o Red = low energy
o UV light has massive effects on life
o EM waves travel perpendicular to each other (One about the xy plane, another about
the xz or yz plane)
o Wave is made of the path of photons (particle of light)
o Photon is equal to an electron in mass and energy and have different levels of energy
o Photons are absorbed by electron orbitals of similar energy
o If red, green and blue light hit a particular spot of chlorophyll :
The red will excite electrons to a slightly higher level
Blue excites it to an even higher energy level
The green is either passed through or reflected and therefore plants look green
o With chlorophyll the high energy electrons get passed on and start a cascade to perform
o O2 gas is a product of photosynthesis
o The peak photosynthesis are occurring at 425 nm (Blue) and at 700 nm (red)
o Green stimulates minimal photosynthesis
575 nm (green) stimulates a little photosynthesis in this system due to:
Experimental error
Other pigments (may use green light and release something else)
Chlorphyll will only absorb a little light at 575 nm
Light is used as a source of information
o Chlamydomonas is a unicellular eukaryote
Eyespot is a patch of proteins (etc.) and pigment s that absorb light
o Photomorphogenesis is the use of light to change and grow
Proteins + pigment a response
In some cases, changing the pattern of “gene expression” (which genes *on
DNA] are used to make protein)
o Rhodopsin
A protein
The light changes the structure in retinal (changes from cis to trans)
Retinal changing structure causes (de)activation of other structures
Retinal See sheet 2
o Eyes and brain must co-evolve
o Flatworm (Planaria)
Light reaches photoreceptors from one side, cup on the other
Eyespots connected to Planaria’s nervous system
o Insects
Sections of the eye and the photoreceptors are multi-cellular
o Higher Animal
Retina and corneal as well as the lens used to focus and things like that
This is much more advanced, used to tell where light is coming from, etc.
o Flat all the photoreceptor cells can just detect the presence of light with minimal
o Eyecup allows organisms to determine direction (essentially “where is the light
coming from”)
GOING TO the light means something is photosynthetic
MOVING FROM the light means it is prey so they can hide in the dark
Most evolved eyes best resolution
o They can see the best difference between two or more things
o Edges and things like that are more distinct (does not necessarily mean better
Light and Behaviour
o Circadian rhythm how one reacts to night and day (hours of dark vs. Hours of light)
Some animals have evolved for night time (nocturnal)
SCN (Supra chiasmatic nucleus) [this is within the brain]
Light causes (via the SCN) the inhibition of the work of the pineal gland
At night, melatonin is produced by the pineal gland
Melatonin is used amongst other things to aid with sleep
For some reason, the melatonin system doesn’t kick in very quickly so they need
to sleep in
o Behaviour, evolution, light, and habitat
o Eye and brain
o Having a plant that is the only attraction for certain pollinators essentially means that
the plant will not waste any pollen uselessly
o Due to protein activity
o GFP (Green Fluorescent Protein) often used in biotechnology
Often comes from squids
Clone the GFP gene into other cells along with a gene of interest
Green fluorescence will show on the cells that have picked up the genes
Can show evolution etc and is now a benefit to man in science
The “Dark Side” of Light
o Light can damage molecules such as DNA
This can cause mutation, loss of function
Break up cells can kill things etc.
Fading of books
o Cancer genes, everyone has them, they are turned off
o Melanin is our protection from this
Direct light causes damage to the molecule (eg. UV light will create Thymine
dimers [two Thymine molecules link together])
Indirect light will create molecules that then damage proteins and DNA, etc.
(eg. Light Oxygen radicals, peroxides from O2, H2O, etc)
Products (O*) are very reactive
Break bonds in proteins or DNA etc