QUIZ 1 Flashcards
What is the difference between Rayleigh and Mie scattering efficiencies, specifically their relationships between scattering efficiency and wavelength?
In Rayleigh scattering, efficiency is related inversely to the fourth power of wavelength
In Mie scattering, efficiency is not strongly dependent on wavelength
Rayleigh scattering efficiency is related to the inverse of wavelength to the fourth power
Mie scattering efficiency is not strongly related to wavelength
How does this difference rationalize the colour of the sky and the clouds?
Clouds are water vapour particles which are much larger than the small molecules making up the air. This means clouds are a result of mie scattering -> all wavelengths scattered equally efficiently (white/grey)
The general air molecules in the sky are a result of Rayleigh scattering which scatters smaller wavelengths most efficiently -> blue sky
What optical behaviour is responsible for the difference between the blue ish colour of skim milk compared to the pure white colour of whole milk?
Rayleigh and Mie scattering.
Rayleigh scattering occurs in skim milk because there are no lipid (larger) molecules and Rayleigh scattering is most efficient with small wavelengths like blue. Mie scattering occurs in whole milk because of the larger lipid molecules, resulting in scattering of all wavelengths equally and a white colour.
What is the biological optical window? (Used for diagnostics)
700-1000nm is the biological optical window
When removing phosphates from ATP, how many phosphates should be removed for maximum energy efficiency?
Only 1 phosphate should be removed ATP -> ADP +Pi (-30.5 kJ/mol)
Because the relationship is not linear as removing 2 phosphates does NOT release double the energy (-45.6kJ/mol)
Where does photosynthesis take place?
Photosynthesis occurs in the thylakoid membrane
How do chlorophylls a and b differ?
Chlorophyll b has the addition of a double bonded O which changes its absorption spectrum.
The path of a signal from reception to reaction: What steps follow the Reception step?
1) reception
2) transduction
3) conduction
4) analysis and interpretation
5) feedback
In biological sensors, the stimulus is converted to an electrical impulse during which step of a path of a signal?
Step 2) transduction: the stimulus is converted to an electrical impulse
In biological sensors, the electrical impulse is carried to the brain through the nervous system via an AP during which step of the path of a signal?
Step 3) Conduction
What are the three different types of biological sensors?
Light, chemical, mechanical
The auditory system relies on what type of biological sensor?
The auditory system, where sound waves (pressure changes) make the ear drum vibrate, relies on mechanical biological sensors
What are the 5 devices required for an artificial biosensor?
Artifical biosensor
1) biorecognition element
2) transducer
3) amplifier
4) signal converter
5) recording device
In an artificial biosensor what is the role of the transducer?
The transducer converts the stimulus into an E signal
In an artificial biosensor, what is the role of the amplifier?
The amplifier boosts the voltage of the signal
In an artificial biosensor, what is the role of the signal converter? why?
The signal converter transforms the electrical signal arriving from the transducer from analog to digital so it can be processed by a computer
In the Hodgkin Huxley Model, what do the capacitor, resistors, batteries, and current source each represent?
Capacitor represents the lipid bilayer
Resistors represent the voltage-gated ion channels
Batteries represent the electrochemical gradients
Current source represents the active pumps
What experimental technique is used to study the dynamics of ion channels in the membrane?
The patch clamp technique is used, it can study individual ion channels of a cell
Light intensity and colour vision are handled by different photoreceptor cells. Which photoreceptor cells are responsible for which?
Cone photoreceptor cells handle colour vision
Rod photoreceptor cells handle light intensity
Cone photoreceptors handle colour vision. How can cones explain how various degrees of colour blindness exist?
Various degrees of colour blindness can be explained because 3 different cone types are responsible for the visible light spectra.
Ex: one kind of colour vision deficiency is also called dichromacy because one of your 3 cones is missing or malfuctioning. The colours someone with dichromacy can see depends on which cones are missing or malfunctioning.
What is the difference between ospins and retinal?
Opsins refer to all and any light-sensitive proteins in the photoreceptor cell, whereas retinal is one specific opsin protein
What is the interaction between retinal and light that supports the function of the visual system.
Retinal absorbs incoming light and transforms into an activated version of itself. This ultimately results (*) in the perception of light or images by the brain
this is photoisomerization because light triggers a change in molecular configuration
*from wikipedia lol just for fun
Retinal catches a photon of the correct wavelength -> retinal straightens out and pushes against an opsin protein in the retina -> triggers a chemical signaling cascade -> results in the perception of light or images by the brain
How does the light detected by photoreceptors get converted to electrical impulses, to then be sent to the brain? What is this process called?
Phototransduction is the conversion process which is a result of membrane depolarization and multiple specialized proteins, including GTP and GDP
Channelrhodopsins are light-gated ion channels. What molecules do they contain to allow them to be light-gated?
Channelrhodopsins contain a chromophore located in retinal which responds to specific wavelengths
What is optogenetics?
Optogenetics is a field that uses genetic engineering of ion channel proteins to trigger membrane potential changes (and, therefore, information transfer) from light input.
- from google lol
can investigate how the neurons work together, by using light to turn some neurons on and record the response of other neurons
this is useful for understanding how and when the neurons interact with each toher
What are the three ways to express opsins in neurons?
Virus transduction, transfection and transgenic animal lines
Why would we want to express opsins in neurons?
In order to control membrane potentials with light, opsins need to be expressed in neurons
- from google lol
can investigate how the neurons work together, by using light to turn some neurons on and record the response of other neurons
this is useful for understanding how and when the neurons interact with each toher
What technique can be used to open the cell membrane, allowing the insertion of genetic material?
Electroporation uses an electric field to temporarily render the membrane porous*
*from thermofisher scientific for fun
Host cells and selected molecules are suspended in a conductive solution and an electric circuit is closed around the mix. An electric pulse of a few microseconds is discharged through the cell suspension which disturbs the bilayer, forming temporary pores. The E potential rises which allows charged molecules (DNA) to be driven across the membrane
What is the difference between the knockout mouse and the chimeric mouse?
Knockout: In the embryonic stage of growth, modified genetic material is introduced to embryonic stem cells. As a result, the knocked-out genetic material will be missing across all tissues.
Chimeric: Mice hybrids, carrying two different genomes(one modified), are bred together until a mouse homozygous for the GMO genetically material will be created naturally
In genetically modified organisms, how does light reach the modified neurons?
Small holes are drilled through the skull of the organism, and optical fibers carry light to the target region
What are the benefits of artificial photosynthesis?
Artificial photosynthesis is a
carbon-neutral,
sustainable method
for generating energy by splitting water to form molecular hydrogen.
Water splitting like this can be achieved by a proton-coupled multi-electron transfer process, allowing for net energy to be produced.
By the Huygens-Fresnel Principle,
When light interacts with a material at an interface, points of interaction will be sources for new circular waves these waves will then interact with eachother, creating a wave front
By Fermat’s principle,
Light will always take the path requiring the shortest time when traveling between two points
What determines if a photon is scattered or absorbed?
“If a photon does not strike molecules in the ““correct way””, the photon will be scattered instead of absorbed”
A mirror is an example of when reflection is diffuse or specular ?
A mirror is an example of when reflection is specular, where the angle of incident light is equal to the angle of reflected light
What causes reflection to be diffuse?
Diffuse means that light rays will be reflected in multiple different directions due to imperfections in the surface
Reflected light A has a higher intensity than reflected light B but both originate from incident light of the same intensity.
Which light has a smaller angle of incidence?
Generally, larger incident angles translate to lesser light intensities so reflected light A has a smaller angle of incidence
What are the four main behaviours that allow light to interact with matter?
reflection, absorption, emission, and scattering
A photon strikes an object and the energy of the scattered photon does not match that of the incident photon. Which kind of scattering is it?
Because of the change in energy between the incident and the scattered photons, this scattering must be inelastic so it is raman scattering
What is raman scattering?
Raman scattering is inelastic scattering which results in a polarizaility change in the molecules struck by light
What is the difference between Mie and Rayleigh scattering?
Mie and Rayleigh scattering are both elastic, but Mie scattering applies to objects similar in size to the light’s wavelength, whereas Rayleigh scattering applies to objects smaller in size to the light’s wavelength
Which type of scattering can rationalize the blue colour of the sky?
Rayleigh scattering, the elastic scattering on objects smaller than the wavelength of light, because atmospheric particles are smaller than the wavelength of light
Also, they scatter the shortest wavelengths of light (in the visible spectrum this is blue light) the most which results in the blue colour
Which kind(s) of scattering is elastic?
Both Rayleigh and Mie scattering are elastic
What is scattering?
Scattering in general is the deflection and/or diffusion of light
Do glowsticks use phosphorescence or fluorescence?
Glowsticks are able to glow for hours,
so they use phosphorescence which has lifetimes in the order of hours
Does phosphorescence or fluorescence have longer lifetimes?
Phosphorescence have longer lifetimes which are on the order of hours whereas, fluorescence lifetimes are on the order of nanoseconds
What is phosphorescence?
Phosphorescence is the absorption and subsequent emission of light which occurs for far longer
Fluorophore A’s light emission lasts for 10 ns while Fluorophore B emits light for 20ns
Which fluorophore has a higher fluorescence lifetime?
Fluorophore B has a longer light emission time therefore its fluorescence lifetime is larger
What is the fluorescence lifetime?
The fluorescence lifetime is the measure of how long the molecule in question will remain in the excited state
