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Chapter 1

Biology 1000 Chapter 1 York University.docx

3 Pages

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BIOL 1000
Angelo Belcastro

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1.1 Sun converts Hydrogen to helium, converting matter into energy and giving of electromagnetic radiation 1.1b Light and Matter Lights is either reflected, transmitted or absorbed For energy to be used by living things, energy must be absorbed Photon must be transferred to a e- in a molecule, which excites it from the ground state But, a photon is only absorbed if its energy is equal to the energy difference b/t ground state and excited state PIGMENTS ex. Chlorophyll a Absorbs photons Contains a region where C atoms are covalently bonded w/ea other w/alternating single and dbl bonds Called a CONGUATED SYSTEM They contain delocalized e-, meaning free electrons that are free to interact with incoming photons 1.2 Some organisms use light energy to power proton pumps: Halobacteria 1.3a Rhodopsin Photoreceptor Rhosopsin is a universal photoreceptor Composed of OPSINS that binds pigment mol’c called RETINAL Opsins are membrane proteins The abosorption of a photon causes the retinal to change shape Shape changes cause changes in opsin, which triggers various other changes 1.3b Light w/o eyes Organisms use eyespots to sense light around them, but not used in photosynthesis Photoreceptors allow cells to sense light and move away or towards it : photoaxis Photomorphogenesis: when seedlings activate genes for photosynthesis after sensing light 1.3c The Eye Eyes focus, absorb and brain interpret Eye and brain are thought to have evolved together because the brain processes visual cues Eyes that allowed the distinction of objects and shapes Compound Eyes:100’s of units called OMMATIDIA, each an individual eye Single: camera like eye. Light enters cornea, light is focused onto photoreceptors cells of retina and brain gets info from optic nerves 1.3d Darwin and Evolution of Eye Said eye evolved to what it is today First it would have been light sensitive skin All animals have similar set of genes for eye function PaX6. 1.4 Uniqueness of Light Shorter wavelengths would have had too much energy and deystroyed chemical bonds, and in addition these wavelengths are absorbed by the ozone Longer wavelengths wouldn’t have enough energy to excite an electron from its ground state, and they are also absorbed by water 1.5a Damage
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