Question

question 22
the image represents a human cell in an isotonic solution. some common cellular molecules that can freely move across the plasma membrane are shown
image of a human cell with atp, o₂, co₂, h₂o inside and outside
what do you think will happen if no energy is used?
○ a some h₂o will leave the cell.
○ b some h₂o will enter the cell.
○ c some co₂ will leave the cell.
○ d some o₂ will enter the cell.

question 23
in a molecule of double - stranded dna, the amount of adenine present is always equal to the amount of ______.
○ a thymine
○ b cytosine
○ c uracil
○ d guanine

Explanation:

Question 22

1. Analyze the cell environment: The cell is in an isotonic solution, so for water (H₂O), the net movement is zero, but individual water molecules still move in and out (osmosis, no energy needed). For O₂ and CO₂, they move by diffusion (no energy).
2. Evaluate Option a: In isotonic, H₂O movement is balanced, so "some H₂O leave" is possible (individual molecules move), but let's check others.
3. Evaluate Option b: Similarly, some H₂O can enter, but wait—wait, the question is about no energy. Wait, O₂: cells use O₂ for respiration, so O₂ concentration inside is lower than outside (since it's used up), so O₂ diffuses in (no energy). CO₂: cells produce CO₂, so inside concentration is higher, so CO₂ diffuses out (no energy). But the options:

• Option a: H₂O leaving—possible, but in isotonic, net movement is zero, but individual molecules move. But wait, the options: let's re-examine. Wait, the cell is in isotonic, so H₂O concentration is same inside and outside. So H₂O moves in and out equally (net zero). But O₂: inside the cell, O₂ is consumed (for ATP production, as ATP is shown), so O₂ concentration inside is lower than outside. So O₂ will diffuse into the cell (no energy). CO₂: inside is higher (produced), so diffuses out. Now the options:
• Option a: Some H₂O leave—since H₂O moves freely, some do leave, some enter (net zero). But is there a better option?
• Option d: Some O₂ enter the cell—since O₂ is used inside, concentration gradient (outside > inside), so O₂ diffuses in (no energy). Wait, but the question is "what will happen if no energy is used". All these movements (osmosis, diffusion) don't need energy. But let's check the options again. Wait, maybe I made a mistake. Wait, the cell has ATP, but the question is "if no energy is used"—but diffusion and osmosis don't use energy. Let's re-express:

• O₂: inside cell, O₂ is used (ATP production), so [O₂] inside < outside. So O₂ diffuses into cell (no energy) → Option d: "Some O₂ will enter the cell" is correct? Wait, but also CO₂: [CO₂] inside > outside, so CO₂ diffuses out (Option c: "Some CO₂ will leave the cell" is also correct? But the options are a, b, c, d. Wait, maybe the question is about which is a consequence of no energy (but all these are passive, no energy). Wait, maybe the key is that in the cell, O₂ is consumed, so O₂ must enter (no energy), CO₂ produced, so leaves (no energy). H₂O: isotonic, so in and out. But the options: let's check the original image. The cell has O₂ inside, and more O₂ outside. So O₂ will enter (diffusion, no energy). So Option d: "Some O₂ will enter the cell" is correct? Wait, but maybe the intended answer is d? Wait, no—wait, the cell is in isotonic, so H₂O: same concentration. O₂: inside is lower (used), so O₂ enters. CO₂: inside is higher (produced), so CO₂ leaves. So options c and d are both correct? But the question is multiple choice, so maybe the intended answer is d? Wait, no—wait, the options:

Let's re-express:

• Option a: Some H₂O leave the cell. Since H₂O is free to move, some do leave (and some enter), so this is true.

• Option b: Some H₂O enter the cell. Also true.

• Option c: Some CO₂ leave the cell. True (diffusion, no energy).

• Option d: Some O₂ enter the cell. True (diffusion, no energy).

But this can't be. Maybe the question has a typo, or I misinterpret. Wait, the cell is in isotonic, so for H₂O, net movement is zero, but individual molecules move. For O₂ and CO₂, diffusion occurs. But the options: maybe the intended answer is d? Or c? Wait, the cell has CO₂ inside, so CO₂ will leave (Op…

1. Recall DNA base pairing: In double - stranded DNA, Adenine (A) pairs with Thymine (T) via two hydrogen bonds, and Guanine (G) pairs with Cytosine (C) via three hydrogen bonds.
2. By the base - pairing rule, the number of Adenine molecules is equal to the number of Thymine molecules, and the number of Guanine molecules is equal to the number of Cytosine molecules.
3. Uracil (U) is not present in DNA (it is present in RNA, where it pairs with Adenine). So the amount of Adenine is always equal to the amount of Thymine.

Answer:

d. Some O2 will enter the cell.

Question 23