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[BIOL 1000] - Final Exam Guide - Comprehensive Notes for the exam (39 pages long!)


Department
Biology
Course Code
BIOL 1000
Professor
Nicole Nivillac
Study Guide
Final

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York
BIOL 1000
FINAL EXAM
STUDY GUIDE

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What is light?
Visible region of the electromagnetic spectrum that is visible to the human eye
ELECTROMAGNETIC RADIATION
Variable wavelength and energy
Measured in nanometers
Wavelength and energy inversely related
HOW DOES LIGHT INTERACT WITH MATTER
1.Reflected off object
2.Transmitted through object
3.Absorbed by object
a. Absorption occurs when photon is transferred to electron within molecule (ground to
excited state
b. Only absorbed if energy of photon matches amount of energy to move the photon to
another state
a.i. If not, then its transmitted instead of absorbed
HOW IS LIGHT CAPTURED
Through pigments
oStream of energy particles called photons
oResonant structure, accessory pigments transfer energy to chlorophyll a
Conjugative system - one thing that all pigments have in common
oAlternating single/double bonds of carbon atoms
oResults in delocalized electrons (not tightly bound to carbon; easily excited)
oElectrons capture photons/energy which can be used to do work
i.e. chlorophyll
FIRST PURPOSE OF LIGHT: SOURCE OF ENERGY
HALOBACTERIUM
Does not use light energy to convert CO2 into carbs
Contains bacteriorhodopsin (light driven proton pump)
oPigments capture sunlight to drive the pump ; creating a chemical gradient (potential
energy for ATP synthase)
SECOND PURPOSE OF LIGHT: SOURCE OF INFORMATION
Many organisms use light as source of energy
Photoreceptor: light sensor
oRhodopsin - found in rods of retina
i.e. Chlamydomonas eyespot contains rhodopsin
oHas two components
Retinal (that changes shape)
1. Cis-retinal and trans-retinal
Protein (transmembrane)
oConsists of opsin protein that's binded to retinal (pigment molecule)
oHow it functions:
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Rhodopsin is inactivated when in dark environment and in cis-retinal
Result from light absorption rhodopsin is activated
1. Shifts from cis-retinal to trans-retinal - causes a change in structure of
protein
Change of the protein causes alterations in intracellular ion
concentration
oPhototaxis
An organism's response to light exposure
1. i.e reinhardti cells respond by swimming towards/away to max. amount
of photosynthesis it can carry out
oAbsorption causes action potentials to be generated in afferent neurons connected to
ommatidium (subunits of an eye - usually found in flies)
oAbsorption is linked to phototaxis through signal transduction
THE EYE
Organ used to sense light
Important for vision - distinguishing it from the eyespot
oEyespot - 2 layer carotenoid rich globs that focus and direct incoming light
Locates light direction and intensity
oVision requires the brain to interpret signals sent to it from the eye
Different types of eyes
oOcellus
oCompound
oSingle/camera
oHuman
OCELLUS EYE
Detects light but doesn’t form image
A cup full of ~100 receptor cells that are attached to ends of cerebral ganglion
oLight is stopped by pigment cup and light reaches the photoreceptors
oSends info through the ganglion
i.e. worms
oPhototaxis causes them to stray away from light and into darkness
COMPOUND EYE (flies)
Ommatidium (looks like epipen) has its photoreceptor cells within the walls of the light-blocking
pigment cells
Composition of ommatidums to form a complete picture
oLight is focused by cornea
oFiltered through crystalline cone
oPasses it down to photoreceptor cells
SINGLE/CAMERA EYE (fish eye)
Lens concentrates and focuses lights to photoreceptors located at back of eye
Retina records the image then sends the info to the brain
HUMAN EYE
Iris - composed of smooth muscles that open and close
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