Lec 7-8 Flashcards
(56 cards)
The visual system (the eye) transforms light into energy. In what form is this energy transformed? What is its role?
Action potential, transmitted and later interpreted by the brain
What is the process of light abosrption in the eye? (4)
1) Light goes trough layers of transparent neurons
2) Light is absorbed by cones and rods (photoreceptive layer) at the back of the retina
3) The information is processed by several layers of neurons
4) Information reacher the ganglion cells which send
thier axons to the brain
1) reception: receptors receive stim
2) transduction: light stim is converted into electrical signal
3) conduction: electrical impulse carried to the brain
4) analysis and interpretation: processing in the brain
5) reaction is triggered as result of stim
5) feedback
How are rods distributed in the eye? What is the main characterisitc about their absorption spectrum? What is their role?
Distributed everywhere except in the fovea and the blindspot. They are not color specific and are responsible for light intensity detection
How are cones distributed in the eye? What is their role?
The cones are highly concentrated in the fovea, where the visual acuity is the highest. They are not found in the blindspot. They are responsilble for color detection.
How does the concentration of cones and rods comapre?
Rods are higher in number everywhere in the retina except at the phobea. There are a lot more rods in total
How are the light-sensitive proteins found in photoreceptor cells called?
Opsins
Explain the functioning of light-sensitive proteins in photoreceptor cells. What is the process called?
A conformational change of the proteins (opsins) is induced when the appropriate wavelength of light hits it. This is called as photoisomerization. This confromational change opens the ion channels (the proteins are transmembran proteins), which leads to the release of an action potential. The transformation of light into an electrical impulse is called phototransduction.
What is the precise name of the molecule that abosrbs light in Opsins?
Retinal
What does the wavelenght of absorption by retinal depend on?
The length of its chain
What two energy carrying molecules are consumed in phototransduction?
GTP and GDP
In what two different ways can photoisomerization affect the ion channels?
Light can either close or open the ion channels
What is the formula for Coulomb’s law?
Fe = kq1q2/r^2
What is the sign of the force if it is attractive between two charged particles? if its repulsive?
F is negative for attractive, F is positive for repulsive
What are intramolecular forces?
Forces of attraction or repulsion occurring between particles within a single molecule
Between which two types of atoms does ionic bonds occur? How is the bond formed?
Between metallic and non-metallic elements, bond is formed by complete transfer of valence electrons (creates two oppostiely charged ions (ionic)). The metal loses electrons to become a cation (positive) while the non metal accepts electrons to become an anion (negative).
What is electronegativity? What is the general trend of electronegativity in the preiodic table?
Chemical property that describes the tendency of an atom to attract a pair of electrons. Electronegativity increases rightwards (more valence electrons), and upwards (smaller in size)
Between which two types of atoms do covalent bonds occur? How is the bond made? What are the two types of covalent bonds?
Between to non-metal elements, sharing of electrons. There can either be a polar or a non polar bond
What is the threshold of electronegativity difference for a covalent bond to be polar or not?
Non-polar bonds are up to 0.5, polar bonds are from 0.5 till 1.9
What are metallic bonds? What are their characterisitcs? In which substances can it occur?
Type of covalent bond that occurs specifically between atoms of metals. Velcnce electrons are free to move trough the lattice (key word). The bond is formed by the attarction of the mobile electrons, to the fixed positvely charged metal ions. Occurs in pure metlas like gold, and alumminum, or in alloys like brass or bronze
What is the Lennard-Jones potential?
It’s the potential energy of interaction between two non bonding molecules based on their disytacne of separation
What is the Lennard-James potential equation? Which factor is the largest? What variable represents the Van der Waals radius? What is the Van der Waals radius?
V(r) = 4epsilon[(sigma/r)^12-(sigma/r)^6)]
The repulsive factor is the largest
The Van der Waals raidus is represented by sigma, and this value represents the distancee when the potential between the particles is zero (perfect distance).
How does the graph fro the lennard-James potential between two molecules look?
Can’t add images without paying the subscription but mainly knowing that it starts from infinitely high, until it reaches distance sigma (0 potential), then goes until maximum depth (epsilon) then it goes back up approaching zero to infinity.
What are intermolecular forces? In terms of strength, how do they comapre with intramolecular forces?
Forces of attraction or repulsion ocurring between different molecules, and they are waker than intramolecular forces
What are the two main categories of intermolecular forces? What are they responsible for?
Short range: repulsive, occur when the centres fo the molecules are spearated by 3 agnstroms or less
Long range: Van der Waals forces
These forces are sponsible for: surface tension, friction, viscosity and different behaviorus of gases.
