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BIEN 210 quiz 1 > Lec 7-8 > Flashcards

Lec 7-8 Flashcards

1
Q

The visual system (the eye) transforms light into energy. In what form is this energy transformed? What is its role?

A

Action potential, transmitted and later interpreted by the brain

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2
Q

What is the process of light abosrption in the eye? (4)

A

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

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3
Q

How are rods distributed in the eye? What is the main characterisitc about their absorption spectrum? What is their role?

A

Distributed everywhere except in the fovea and the blindspot. They are not color specific and are responsible for light intensity detection

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4
Q

How are cones distributed in the eye? What is their role?

A

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.

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5
Q

How does the concentration of cones and rods comapre?

A

Rods are higher in number everywhere in the retina except at the phobea. There are a lot more rods in total

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6
Q

How are the light-sensitive proteins found in photoreceptor cells called?

A

Opsins

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7
Q

Explain the functioning of light-sensitive proteins in photoreceptor cells. What is the process called?

A

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.

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8
Q

What is the precise name of the molecule that abosrbs light in Opsins?

A

Retinal

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9
Q

What does the wavelenght of absorption by retinal depend on?

A

The length of its chain

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10
Q

What two energy carrying molecules are consumed in phototransduction?

A

GTP and GDP

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11
Q

In what two different ways can photoisomerization affect the ion channels?

A

Light can either close or open the ion channels

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12
Q

What is the formula for Coulomb’s law?

A

Fe = kq1q2/r^2

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13
Q

What is the sign of the force if it is attractive between two charged particles? if its repulsive?

A

F is negative for attractive, F is positive for repulsive

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14
Q

What are intramolecular forces?

A

Forces of attraction or repulsion occurring between particles within a single molecule

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15
Q

Between which two types of atoms does ionic bonds occur? How is the bond formed?

A

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).

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16
Q

What is electronegativity? What is the general trend of electronegativity in the preiodic table?

A

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)

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17
Q

Between which two types of atoms do covalent bonds occur? How is the bond made? What are the two types of covalent bonds?

A

Between to non-metal elements, sharing of electrons. There can either be a polar or a non polar bond

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18
Q

What is the threshold of electronegativity difference for a covalent bond to be polar or not?

A

Non-polar bonds are up to 0.5, polar bonds are from 0.5 till 1.9

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19
Q

What are metallic bonds? What are their characterisitcs? In which substances can it occur?

A

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

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20
Q

What is the Lennard-Jones potential?

A

It’s the potential energy of interaction between two non bonding molecules based on their disytacne of separation

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21
Q

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?

A

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).

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22
Q

How does the graph fro the lennard-James potential between two molecules look?

A

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.

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23
Q

What are intermolecular forces? In terms of strength, how do they comapre with intramolecular forces?

A

Forces of attraction or repulsion ocurring between different molecules, and they are waker than intramolecular forces

24
Q

What are the two main categories of intermolecular forces? What are they responsible for?

A

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.

25
Q

What are the three types of Van der Waals forces?

A

Dipo-dipole interactions (polar-polar, H-bonds)

Dipoles and induced diples (Polar-induction)

London Dispersion Forces(Induction-Induction)

26
Q

Why do Dipole-Dipole forces occur? What is the prerequisite?

A

These forces occur when the partially positively charged part of a molecule interacts with the partially negative charged part of the neighbouring molecule. The prerquisite is there has to be partial charges on the molecules due to differences in electronegativity (dipole moments).

27
Q

What makes H-bonds particular? To which elements are these bonds usually associated to?

A

They’re dipole-dipole interactions between molecules whose atoms have a particulary significant difference in electronegativity. They’re typically associated to bonds between hydogen and Nitrogen, Oxygen and Fluorine

28
Q

What are London dispersion (or London Fritz) forces? How are they created? What is the relationship between the strength of this forces and the number of electrons in a molecule?

A

They are temporary attractive foces between the molecules. They occur due to the random movement of electrons. The electrons of adjacent atoms of each molecule ocupy postions that make them form temporary dipoles, which creates a shift in the electron cloud, which induces an attraction between the dipoles. The more electrons a molecule has, the stronger the London dispersion forces.

29
Q

What is a disulfide bond (bridge)? How are they derived? What are their role in protein structures?

A

A disulfide bond is a covalent bond derived from the oxidation of two tihiol (S-H) groups
Intramolecular disulfide bonds stabilize tertiary structure, while intermoleculer disulfide bonds stabilize quaternary structure.

30
Q

Wha causes capillary action? Where can it occur?

A

Capilarry action occurs due to forces of cohesion (attractions within the molecules of water) and adhesion (attractions towards the sruface). It only occus in tubes of small diameter, where the adhesive forces are stronger thatn the cohesive forces.

31
Q

What forces create surface tension? What does it create? What is it’s effect on movement in and on top of water?

A

Surface tension is a result of cohesive forces. It leads to a surface film, which makes it more difficult to break trough the film than it is to move inside the liquid. Allows for animals to walk on top of water

32
Q

What is the role of surfactants? What property allows them to carry it out? How does the process work? Give an example in the human body

A

They’re compounds which lower surface tension by disrupting intermolecular forces. They’re amphipathic (amphipathic) molecules. The hydrophilic part faces liquid, the hydrophobic part the air. The intermolecular forces between water molecules and surfactant are much lower than just water. Surfactants can be found inside the alveoli of lungs and water striders.

33
Q

What is the Young-LaPlace law for surface Pressure?

A

Pa = 2*T/r

34
Q

What is self assembly? What forces drive it?

A

Process in which a disordered system forms an organized structure as a consequence of specific, local interactions spontaneously. Electrostatic intramoleculr and intermolecular interaction (H-bonds), electric magnetic flow and gravitational forces, interface forces (electrsotatic and entropic)

35
Q

What is the formula for Gibbs free energy? When is a process spontaneous?

A

deltaG = deltaH - TdeltaS
(G = gibbs free energy
H = enthalpy
T= temperature
S= entropy)
A process is spontaneous when delta G is negative

36
Q

How does hydrophobicity lead to self assembly? What is an important example of this?

A

Hydrophobic molecules in water aggregate to increase entropy in the system. In an unaggregated state, water molecules for highly orderd strucutres around them, when they aggregate, the water population is less ordered and entropy is increased. This is the process forthe lipid bilayers and protein folding with hydrophobic amino acids.

37
Q

What is the blidnspot in the retina?

A

Place where the optic nerve passes trough the reitna, there are no rods or cones

38
Q

How is the superhydrophobic effect created?

A

Superhydrophobic effects are due to the presence of micro- and nano-structured patterns.

39
Q

What is the contact angle in hydrophobicity?

A

Angle formed by a liquid at the three pahse boundary

40
Q

What instrument is used to measure the superhydrophobic contact angle?

A

Goniometer

41
Q

What is the formula to calculate the superhydrophobic contact angle?

A

Ysg = YsL +YLg cos (theta)

42
Q

What is the minimum contact angle for it to be considered superhydophobicity?

A

More than ninety degrees

43
Q

What are the two regimes of superhydrophobicity?

A

The two regimes are Wenzel (water flows into the structure) and Cassie-Baxter (water does not flow into the structure).

44
Q

What are the three types of structures that can be used for superhydrophobcity

A

The three strucures are nanostructure (smallest), microstrucutre and hierarchical (mix of both).

45
Q

What is the basic definition of networks?

A

Combinations of various nods (elements) linked together trough edges (lines between the elements)

46
Q

What is the Leidenfrost effect?

A

Effect by which a drop of liquid evaporates slower than it should on top of a extremely hot surface due to a layer of vapor forming underneath (video of worker passing his hand trough molten metal)

47
Q

Explain the coffee ring effect? What are its applications?

A

Process of self-assembly driven by surface tension and convection. The temperature gradient before the water droplet dissapears forces the molecules towards the sides. Their position is determined by size, larger molecules are closer to the center while smaller molecule can move much further. It can be applied to analysis of substances by separating its components by size. Separation decreases with volume fraction.

48
Q

What are modules/nodes in a network?

A

Integrated units that can be combined in many ways

49
Q

What is the topology of a network? What are the three kinds?

A

The way the nodes are connected in a network:
Hierarchical, scale-free (some individuals connected to lots of others, most connected to only a few), distributed

50
Q

What is the emergent behaviour/properties of a network?

A

The output of a network

51
Q

What does the robustness of a network mean?

A

Ability of the network to provide the same output despite internal or external changes

52
Q

What are interactomes?

A

They describe molecular interactions within a cell or organism

53
Q

What is one application of scale-free networks?

A

Understanding the connection between diseases to facilitate their study (there are diagrams in the slides no idea how in detail we have to know them)

54
Q

What systems utilize the hydrophobic effect?

A

Detergents, cellular membrane, protein folding, protein purification

55
Q

What are some applications of superhydrophobic surfaces?

A

Oil/water spearation, self-cleaning materials, anti-corrosion

56
Q

Can you think of conditions where a negative entropy leads to spontaneous slef-assembly?

A

At very low temperatures

BIEN 210 quiz 1 (5 decks)

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