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Vision

A1  0.50 Determine the coefficient $k$. The distance between the thumb and the eye is $l=60$ cm.

1 Triangle similarity $\frac{r}{\Delta x} = \frac{l}{s}$. 0.20
2 Formula $k=l/s$. 0.20
3 Numerical answer $k=10$. 0.10
A2  0.20 Determine the distance $r$ to the car from the example above.

1 Numerical answer $r = 20~ \text{m}.$ 0.20
A3  0.80 A person observes a tree with a height of $h=3.0$ m at a distance of $d=100$ m. It turns out that the size of the tree's image on the retina is $l=0.6$ mm. Using this data, determine the focal length $F$ of the crystalline lens. The optical system of the eye can be considered to consist of a single thin converging lens (the crystalline lens) and a screen (the retina) on which the image is formed.

1 The distance from the lens to the image $f=d \frac{l}{h}.$ 0.20
2 Thin lens formula $\frac{1}{F} = \frac{1}{d} + \frac{1}{f}$. 0.20
3 Final equation $F = \frac{d}{h/l+1}$. 0.20
4 Numerical answer $F=20~\text{mm} \in [19.5; 20.5]~\text{mm}.$ 0.20
A4  0.40 Choose which lenses (Fig. 2) are suitable for glasses to correct farsightedness. Farsightedness is a condition where distant objects are seen clearly but near objects appear blurred. Lenses are made of glass with a refractive index greater than that of air.

1 Any explanation, why convex lens is needed (scheme of light rays, etc). 0.10
2 Final score for this question = $\max \left[ 0.1 \cdot (\#\text{right} - \# \text{wrong} ) ; 0 \right]$,
where
$\#\text{right}$ is the number of selected among $\{ 3, 5, 6\}$,
$\#\text{wrong}$ is the number of selected among $\{ 1, 2, 4\}.$
3 × 0.10
A5  1.10 A very nearsighted person's eye lacks accommodation, meaning this person's eye can only clearly see objects at a distance of $x = 25$ cm. Determine the focal length of glasses would be needed so that this person could clearly see very distant objects. Here we neglect the distance between the lens of the eye and the lens of the glasses. What lens shape (Fig. 2) would be suitable for such glasses?

1 Thin lens formula for case without glasses:
$$\frac{1}{F_0} =\frac{1}{x}+ \frac{1}{f}.$$
0.20
2 Thin lens formula for case with glasses:
$$\frac{1}{F} + \frac{1}{F_0} = \frac{1}{\infty} + \frac{1}{f}$$(term $\frac{1}{\infty}$ could be omitted).
0.20
3 $\frac{1}{F}= - \frac{1}{x}$ or $F = -x.$ 0.20
4 $F=-25~\text{cm}.$ 0.20
5 Final score for this question = $\max \left[ 0.1 \cdot (\#\text{right} - \# \text{wrong} ) ; 0 \right]$,
where
$\#\text{right}$ is the number of selected among $\{ 1, 2, 4\}$,
$\#\text{wrong}$ is the number of selected among $\{ 3, 5, 6\}$.
3 × 0.10
A6  0.30 The argon-fluorine excimer laser generates ultraviolet radiation with a wavelength of $\lambda=193$ nm. Calculate the energy of one photon of this radiation.

1 $\nu = \frac{c}{\lambda}.$ 0.10
2 Equation $$E = \frac{h c }{ \lambda}.$$ 0.10
3 Numerical answer $$E = 1.03 \cdot 10^{-18}~\text{J}.$$ 0.10
A7  0.40

The "evaporation" of microscopic tissue layers using a controlled laser beam occurs due to several processes, one of which is bond cleavage. Compare the obtained laser photon energy with the energies of chemical bonds in corneal biomolecules. Mark the bonds for which the excimer laser photon energy suffices for cleavage.


$E_{\mathrm{(C-C)}} = 348$ kJ/mol


$E_{\mathrm{(C-N)}} = 305$ kJ/mol


$E_{\mathrm{(N-H)}} = 391$ kJ/mol


$E_{\mathrm{(C-H)}} = 413$ kJ/mol


$E_{\mathrm{(C-O)}} = 360$ kJ/mol


$E_{\mathrm{(O-H)}} = 463$ kJ/mol


1 Understanding that photon energy should be converted to $k\text{J/mol}$ or chemical bond energy should be converted to $J$ (per one bond). 0.10
2 Correct calculation.

$$E = 1.03 \cdot 10^{-18}~\text{J}/\text{photon} \cdot 6.022 \cdot 10^{23}~\text{photon} \cdot \text{mol}^{-1} = 620~\text{kJ}/{\text{mol}}.$$
0.20
3 All bonds are selected. 0.10
B1  0.70

Calculate the molar mass of the opsin P08100. Round your answer to the nearest whole number. Ignore any post-translational modifications. The molar masses of amino acids are provided in the answer sheets.


1 For alanine $N=32.$ 0.10
2 Total $N = 348.$ 0.10
3 Any indication, that one water should be subtracted when one bond is formed. 0.10
4 Total molar mass of all amino acids $\in [45\,000; 50\,000]~\text{Da}.$ 0.10
5 Final answer $\in [37\,897; 39\,897]~\text{Da}.$ 0.10
6 Final answer $38\,897~\text{Da}.$ 0.20
B2  0.20 The figure shows two absorption spectra (Fig. 3). Determine which form of the protein (opsin or rhodopsin) these spectra correspond to.

1 Opsin - spectrum 1.
Rhodopsin spectrum 2.
0.20
B3  0.60 Determine the concentration of retinaloxime in the solution at the end of the experiment if the optical path was $l=10$ mm.

1 Absorbance value from the graph after the reaction: $A_{365}^{RO} \in [0.63, 0.69]$. 0.30
2 Equation for concentration: $c=\frac{A_{365}^{RO}}{\varepsilon_{365}^{RO}\cdot l} $. 0.10
3 Numerical answer:

$c\in [18; 22]~\mu\text{M}.$
0.20
B4  0.50 Determine the extinction coefficient of rhodopsin $\varepsilon_{500}^{Rhodo}$ based on the experimental data.

1 Usage of the fact that one molecule of rhodopsin is converted into one molecule of retinal oxime during the reaction (e.g. stating that concentration of rhodopsin before the reaction is equal to the concentration of retinal oxime after the reaction). 0.10
2 Absorbance value from the graph befor the reaction: $A_{500}^{Rhodo} \in [0.79, 0.81]$. 0.10
3 Relationship between two exctinction coefficients: $\varepsilon_{500}^{Rhodo} = \frac{A_{500}^{Rhodo}}{A_{365}^{RO}}\cdot {\varepsilon_{365}^{RO}}.$ 0.20
4 Numerical answer $$\varepsilon_{500}^{Rhodo} \in [38\,600, 42\,800]~\text{M}^{-1} \cdot \text{cm}^{-1}.$$ 0.10
B5  0.40 Determine the number of rhodopsin molecules in the solution if the volume of the solution $V=2$ ml, the optical path $l=10$ mm.

1 Number of molecules in solution: $N=N_A \nu.$ 0.10
2 Moles of molecules in solution: $\nu=c V.$ 0.10
3 Numerical answer $N \in [2.0, 2.8] \cdot 10^{16}.$ 0.10
4 Numerical answer $N \in [2.2, 2.6] \cdot 10^{16}.$ 0.10
B6  0.40 Determine the ratio $r$ of the sensetivities of the long-wavelength $L$ and medium-wavelength $M$ cones to excitation by monochromatic yellow light ($580$ nm).

1 The sensitivity value for $\text{L}$ at a wavelength of $580~\text{nm}$ is $\in [0.94, 0.96].$ 0.10
2 The sensitivity value for $\text{M}$ at a wavelength of $580~\text{nm}$ is $\in [0.55, 0.57].$ 0.10
3 The ratio $\in [1.65, 1.75].$ 0.20
B7  0.90 Determine the intensity ratio $x$ of a mixture of red ($630$ nm) and green ($530$ nm) light so that this light is perceived as yellow from the previous question.

1 The sensitivity value for $\text{L}$ at a wavelength of $630~\text{nm}$ is $\in [0.33, 0.35].$ 0.10
2 The sensitivity value for $\text{M}$ at a wavelength of $630~\text{nm}$ is $\in [0.01, 0.03].$ 0.10
3 The sensitivity value for $\text{L}$ at a wavelength of $530~\text{nm}$ is $\in [0.83, 0.85].$ 0.10
4 The sensitivity value for $\text{M}$ at a wavelength of $530~\text{nm}$ is $\in [0.98, 1.00].$ 0.10
5 Correct equation to find $x$, e.g.:

$$\frac{\text{sensitivity L}}{\text{sensitivity M}}=\frac{0.35\cdot x + 0.84 \cdot 1}{0.02 \cdot x + 0.99 \cdot 1}=\frac{0.95}{0.56},$$
or, general from:

$$\frac{\text{sensitivity L}}{\text{sensitivity M}}=\frac{L_{630}\cdot x + L_{530} \cdot 1}{M_{630} \cdot x + M_{530} \cdot 1}=\frac{L_{580}}{M_{580}}.$$
0.20
6 Final equation (marked full is the numerical answer is OK)

$$x = \frac{r M_{530} - L_{530}}{L_{630} - r M_{630}}, $$
where $r = L_{580} / M_{580}.$
0.10
7 Correct calculation for own data (if they are correct).
For values above the numerical answer is in range $x \in [2.51, 2.83].$
0.20
B8  1.10 The light now contains a mixture of three colors: red ($650$ nm), green ($547$ nm), and violet ($420$ nm). What intensity ratio ($y$: red/violet, $z$: green/violet) must be taken to produce a color identical to the monochromatic color corresponding to a wavelength of $500$ nm (blue)? Is it possible to obtain the desired monochromatic color by mixing three selected colors?

1 Correct ($\pm 0.01$) sensetivity for each receptor. 3 × 0.10
2 Equation on sensetivities for one pair of receptors, for example:

$$\frac{\text{sensitivity L}}{\text{sensitivity S}}=\frac{0.13 \cdot y+0.96 \cdot z+0.08 \cdot 1}{0 \cdot y+0⋅z+1 \cdot 1}=\frac{0.56}{0.09}.$$
0.10
3 Equation on sensetivities for another pair of receptors, for example:

$$\frac{\text{sensitivity M}}{\text{sensitivity S}}=\frac{0 \cdot y+0.96 \cdot z+0.14 \cdot 1}{0 \cdot y+0⋅z+1 \cdot 1}=\frac{0.8}{0.09}.$$
0.10
4 Correct solution to a system of linear equations. 0.10
5 $x \in [-21, -19].$ 0.20
6 $y \in [8, 10].$ 0.20
7 Statement that the desired color cannot be obtained by mixing the three given colors. 0.10
B9  0.50

A father and son have protanopia, but the mother has normal color vision. From whom (mother/father/unable to determine) did the son inherit his protanopia?


1 Father genotype is $\mathrm{X^pY}$ ($\mathrm{p}$ is the protanopia gene). 0.10
2 Mother genotype is $\mathrm{X^PX^?}$. Here $?$ could be anything. 0.10
3 Son genotype is $\mathrm{X^pY}.$ 0.10
4 Son inherited protanopia from his mother. 0.20
B10  1.00

A man with deuteranopia and protanopia married a woman with normal vision. They had a son with deuteranopia (without protanopia) and a daughter with protanopia (without deuteranopia). What is the probability of this marriage having a healthy child? What is the probability of having a child with both anomalies?


1 Father genotype is $\mathrm{X^{pd}Y}$ (protanopia and deuteranopia). 0.10
2 Son genotype is $\mathrm{X^{Pd}Y}$ (deuteranopia, no protanopia). 0.10
3 Daughter genotype is $\mathrm{X^{pD}X^{pd}}$ (protanopia [therefore $\mathrm{pp}$], no deuteranopia [therefore definitely $\mathrm{D}$]) [from father $\mathrm{X^{pd}}$]. 0.10
4 Mother genotype is $\mathrm{X^{Pd}X^{pD}}$ (normal in both [must have $\mathrm{P}$ and $\mathrm{D}$]) [$\mathrm{X^{Pd}}$ for son, $\mathrm{X^{pD}}$ for daughter]. 0.10
5 Possible gametes of mother are $\mathrm{X^{Pd}}$, $\mathrm{X^{pD}}.$ 0.10
6 Possible gametes of father are $\mathrm{X^{pd}}$, $\mathrm{Y}.$ 0.10
7 Correct table with genotype of the offsprings. 0.20
8 The probability of being born healthy is $0/4 = 0\%$. 0.10
9 The probability of being born with two diseases is $0/4 = 0\%$. 0.10
B11  1.10

A man with protanopia and tritanopia married a woman with normal vision. They had a son with tritanopia (without protanopia) and a daughter with protanopia (without tritanopia). What is the probability of having a healthy child from this marriage? What is the probability of having a child with both anomalies?


1 Daughter genotype is $\mathrm{aaX^pX^p}$ (protanopia and no tritanopia). 0.10
2 Son genotype is $\mathrm{AaX^PY}$ (tritanopia, no protanopia). 0.10
3 Father genotype is $\mathrm{AaX^pY}$ (protanopia and tritanopia [therefore $\mathrm{A}$, the second one is definitely $\mathrm{a}$, because must have it for daughter]). 0.10
4 Mother genotype is $\mathrm{aaX^PX^p}$ (normal in both [must have $\mathrm{X^P}$ for son]). 0.10
5 Possible gametes of the father are $\mathrm{aX^p}$, $\mathrm{aY}$, $\mathrm{AX^p}$, $\mathrm{AY}.$ 0.20
6 Possible gametes of the mother are $\mathrm{aX^P}$, $\mathrm{aX^p}.$ 0.10
7 Correct table with genotype of the offsprings. 0.20
8 The probability of being born healthy is $2/8 = 25\%$. 0.10
9 The probability of being born with two diseases is $2/8 = 25\%$. 0.10
C1  0.70 Specify the maximum absorption spectra of the samples (with an accuracy of $\pm 10$ nm).

1 Statement "If a sample has a certain color, it absorbs all other colors" in any correct form. 0.10
2 Orange sample 1 does not absorb red and green, but does absorb blue; therefore, the leftmost curve. 0.10
3 Blue sample 2 does not absorb blue/cyan, but does absorb red and some green; therefore, the rightmost curve. 0.10
4 Violet sample 3 does not absorb blue or red, but does absorb green; therefore, the middle curve. 0.10
5 1: $\in 480; 500~\text{nm}.$ 0.10
6 2: $\in 580; 600~\text{nm}.$ 0.10
7 3: $\in 535; 555~\text{nm}.$ 0.10
C2  0.30 Determine which direction (outward or inward) the proton is pumped in this experiment?

1 Answer: microbial rhodopsins pump protons from the solution into the cell in this experiment. 0.30
C3  0.70

Estimate the initial pumping rate $q$. The pumping rate equals to the number of protons pumped per unit of time by microbial rhodopsins through all the cells of this experimental system.


1 Correct method of estimation, the most simple is to use starting point. 0.10
2 Understanding, how to convert pH to concentration. 0.10
3 Correct equation for $\frac{dC}{dt}.$ 0.20
4 $q=\frac{dC}{dt} VN_a = 2.47 \cdot 10^{13}~\text{s}^{-1}.$ 0.20
5 Numerical answer $q \in [2.2;3.2] \cdot 10^{13}~\text{s}^{-1}.$ 0.10
C4  0.70

Estimate the surface area of one E. coli cell using electron microscopy image (Fig. 9).


1 Formula for estimation $S=2\pi rl.$ 0.20
2 Correct estimation of $l$ from photo. 0.20
3 Correct estimation of $r$ from photo. 0.20
4 Numerical answer $S \in [3.0; 7.5]~ \mu\text{m}^2.$ 0.10
C5  0.50 Estimate the pumping rate $q_1$ through one molecule of microbial rhodopsin. The cell concentration in the vessel is $n_{cells}=6.4 \cdot 10^9$ ml$^{-1}$. Electron microscopy analysis of the membrane surface revealed that the concentration of microbial rhodopsin molecules on the membrane surface is $\sigma = 5 \cdot 10^3 \mu m^{-2}$.

1 Number of cells

$$N_{cell}=nV=1.92 \cdot 10^{10}.$$
0.10
2 The rate of pumping through one cell

$$q_{cell}=\frac{q}{N_{cell}} = 1.290 \cdot 10^3~ \text{s}^{-1}.$$
0.10
3 The number of proteins in one cell:

$$ N_{prot}=\sigma S = 1.87 \cdot 10^4 . $$
0.10
4 The rate of pumping through one molecule (equatioin):

$$q_1 = \frac{q_{cell}}{N_{prot}} = 6.9 \cdot 10^{-2}~\text{s}^{-1}.$$
0.10
5 The rate of pumping through one molecule

$$q_1 \in [3, 12] \cdot 10^{-2}~\text{s}^{-1}.$$
0.10
C6  1.00 Based on the results of the experiment, determine $\alpha$. Indicate the units of measurement for $\alpha$.

1 At the end, equilibrium is established and the fluxes are:

$$j = \frac{q}{SN_{cell} } = 345~ \frac{1}{\mu \text{m}^2 \cdot s}.$$
0.10
2 According to the graph, at 300 s, saturation can be assumed and the final concentration outside is

$$c_{out}= 10^{-6.7}~\text{mol}/\text{L} = 2.0 \cdot 10^{-7} ~\text{mol}/{L}.$$
0.10
3 We estimate the volume of one cell as

$$V_1 = \pi r^2 l = 0.50~\mu \text{m}^3.$$
0.20
4 We calculate the final concentration inside using the fact that the number of protons that entered the cell is equal to the number of protons that left the volume of liquid.

$$c_{in} = \frac{c_0 V_1 N_{cell} + (c_0-c_{out,f} ) V }{ V_1 N_{cell} } = c_0+ \frac{(c_0-c_{out,f} )V }{V_1 N_{cell}}.$$
0.20
5 Numerical value $$c_{in} = 2.49 \cdot 10^{-4}~ \text{mol}/{L}.$$ 0.10
6 We calculate the permeability:

$$\alpha = \frac{q}{SN_{cell} (n_{in}-n_{out} ) } = \frac{2.47 \cdot 10^{13}~\text{s}^{-1}}{3.73 \cdot 10^{-12}~\text{m}^2 \cdot 1.92 \cdot 10^{10} \cdot 1.50 \cdot 10^{23}~\text{m}^{-3} } = 2.3 \cdot 10^{-9}~\text{m}/\text{s}.$$
0.10
7 Numerical answer

$$\alpha \in [0.8, 11] \cdot 10^{-9}~\text{m}/\text{s}.$$
0.10
8 Indication the units of measurement for $\alpha$ 0.10