Biologie - Travaux Dirigés 2024/2025

Questions Travaux Dirigés 2024/2025 - Séance du Vendredi 27.09

• Question Type A - Question No. 1: The correct statement regarding iron absorption and transport is that the majority of iron in the body is found within enzymes responsible for oxidation of organic matter (cytochrome C-oxydase), representing 75% of the total. Iron is transported in the blood by transferrin, not ferritin.

• Question Type A - Question No. 2: The proposition that is not essential for an organism's survival and its descendants is the need to isolate itself from its environment. Other essential aspects are: feeding, reproduction, and internal chemical transformations.

Questions Type A - Question No. 3

• Hemoglobin (Hb) transports four oxygen molecules.

• At the top of Mount Everest (with a partial pressure of oxygen (pO2) of 50 mmHg), 30% of hemoglobin is saturated. The fixation constant (Kfix) is 2.17 x 10^-4.

Questions Type A - Question No. 4

• The transfer of oxygen from hemoglobin to myoglobin is characterized by a change in the oxygen binding site; the binding site of oxygen (O₂) is different in hemoglobin and myoglobin.
• Increased oxygen pressure is favorable for the release of oxygen from hemoglobin.

Questions Type K - Question No. 5

• Oxygen (O₂) is an essential element that is transported in the body by hemoglobin, not in atomic form.
• Oxygen is not highly soluble in water.
• A significant portion (around 2/3) of the human body's mass is comprised of oxygen, not the other way round.

Questions Type K - Question No. 6

• Hydrogen (H) and deuterium (D) have the same atomic numbers and number of electrons. However, they have different mass numbers.
• The properties of H₂O and D₂O are not identical but rather different.

Questions Type K - Question No. 7

• Air is a mixture of gases.
• Oxygen (O₂) and nitrogen (N₂) can be separated using physical methods.
• The air we breathe (inspired air) contains 21% oxygen (O2).

Questions Type A - Question No. 8

• The respiratory quotient (RQ) for glutamine (C5H10N2O3) combustion is calculated based on the combustion products (nitrogen, carbon dioxide, water) - it is 0.83.

Questions Type A - Question No. 10

• To raise the temperature of a 70 kg human body from 35.5 to 36.5°C, a specific amount of glucose needs to be burned; an approximate value is 18.85 g, based on the provided data.

Questions Type A - Question No. 11

• The balanced chemical equation for the fermentation of sucrose (C₁₂H₂₂O₁₁) by yeast to produce ethyl alcohol (C₂H₅OH) and carbon dioxide (CO₂) needs to be determined.

Questions Type A - Question No. 12

• The stoichiometric coefficients for the reaction aMnO₄⁻ + bH₂SO₃ + cH⁺ → dMn²⁺ + eH₂SO₄ + fH₂O must to be found. The correct coefficients are 2,5,6,2,5,3.

Questions Type A - Question No. 13

• At a 50% saturation level for oxygen binding in myoglobin, the pressure is 2.8 Torr. Calculations are required to determine this given the known value of the fixation constant (Kf) of 266.