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Remote Ready Biology Learning Activities

Remote Ready Biology Learning Activities has 50 remote-ready activities, which work for either your classroom or remote teaching.


This examination is designed to take you about an hour to complete, but you may, if you wish, use a period of up to three hours from first looking at the questions to completing the writing of your answers. The additional time is provided to give you time to think about the questions, and to assure that you are not pressed for time in writing your answers. Please do not consult books, notes, or other related material, or discuss the exam questions with others, during the period between first looking at the questions and completing the writing of your answers. This examination consists of twenty questions. The first ten are multiple choice (two points each). The next nine (three points each) require brief answers, which might consist of a phrase or a sentence and should in no case consist of more than three sentences. The last question (twenty points) requires a short essay (less than a page, in the space provided). If you are uncertain about your answer to any questions, leave them while you think and answer other questions, but be sure to return to unanswered questions and do the best job you can within the available time. Please do not exceed the space provided for the short answer and essay questions, and write legibly, putting your name at the top of each page.

Multiple choice questions (2 points each). Put the letter corresponding to the best answer in the space provided to the left (answers in boldface).

1. The sequence of bases in a DNA molecule directly specifies A) the sequence of amino acids in a protein molecule; B) the sequence of fatty acids in a lipid molecule; C) the sequence of sugars in a carbohydrate molecule; D) all of the above.

2. The three-dimensional structure of a protein molecule is A) fixed by its sequence of amino acids; B) varies depending on the interaction of the protein molecule with other molecules; C) is irrelevant to the function of the protein molecule; D) is determined in the process of translation of relevant genetic information coded in an RNA molecule.

3. The second law of thermodynamics says that in any isolated system things move from a less probable to a more probable state. Which of the following is inconsistent with this law? A) the equalizing of the concentration of some substance on the two sides of a partition which allows passage of the substance; B) the persistance of a difference in concentration of some substance on the two sides of a partition which doesn't allow passage of the substance; C) the existence of improbable assemblies of atoms, molecules, cells, and organisms which constitute life; D) none of the above.

4. Which structures contribute to the production of proteins by a cell? A) the nucleus; B) ribosomes; C) endoplasmic reticulum; D) all of the above.

5. Photosynthesis and chloroplasts occur in A) plant cells; B) animal cells; C) both plant and animal cells; D) only in improbable assemblies of cells.

6. Celllular respiration and mitochondria occurs in A) plant cells; B) animal cells; C) both plant and animal cells; D) only in improbable assemblies of cells.

7. In cellular respiration, A) the majority of ATP production occurs during glycolysis; B) the majority of ATP production occurs during operation of the Krebs cycle; C) the majority of ATP productions occurs in the electron transport chain; D) roughly equal amounts of ATP production occur during each of the three phases.

8. During photosynthesis, A) there is no ATP production; B) ATP production occurs during the light-dependent reactions; C) ATP production occurs during the dark reactions; D) ATP production is replaced by NADPH production.

9. Electrons move down an electron transport chain during cellular respiration and A) similarly move down an electron transport chain during photosynthesis; B) instead move upwards along an electron transport chain during photosynthesis; C) do not move along an electron transport chain during photosynthesis; D) end up in water at the end of photosynthesis.

10. Active transport (pumping) of protons to maintain a concentration gradient occurs during A) photosynthesis; B) cellular respiration; C) both photosynthesis and cellular respiration; D) neither photosynthesis nor cellular respiration.

Short Answer (3 points each). Three sentences or less. Write legibly in the space provided (sample answers in boldface).

11. Wood consists largely of cellulose, a macromolecule which is a highly improbable assembly of atoms. Briefly explain why wood is nonetheless a good building material (remains intact and solid for long periods of times), and how it can in addition provide an energy resource for termites but not for people.

In order to break down into its more probable components, cellulose must cross an energy (higher improbability) barrier and therefore normally breaks down quite slowly. Hence wood is relatively stable (a good building material) except in the presence of enzymes which lower the barrier, increasing the rate of breakdown. Termites possess appropriate enzymes, and can use the breakdown to acquire energy (improbability) for themselves; human lack the necessary enzymes.

12. Briefly explain why one has to worry about keeping both the temperature and the pH of water within appropriate fairly narrow ranges in order to assure the health of fish in a home aquarium .

Fish, like all living organisms, depend on protein enzymes to catalyze essential underlying chemical reactions. The emzymatic ability of proteins is closely associated to particular three dimensional shapes, the stability of which is very sensitive to both temperature and other charged particles (including hyrdrogen ions) in their surroundings.

13. Imagine a box with a partition that allows particles to move from one side to the other, as discussed in class. Briefly compare what will happen if one starts with lots of particles on one side of the box and none on the other with what will happen if one starts with the same number of particles on both sides, explaining what accounts for both the similarities and the differences in the two cases.

In both cases one will end up, after a period of time, with similar (but fluctuating) numbers of particles on both sides, since in this state movement of particles across the partition will occur at the same average rates in both directions. This state represents no change from the initial state in the second case, since average particle movement in both directions is already equal. In the first case, the equal particle state will take some time to achieve, as the system moves, due simply to random particle movement, from a less probable to a more probable state.

14. Briefly describe how an improbable assembly, such as a stable large difference in numbers of particles on the two sides of a box, can come into existence in a non-biological situation without violating the second law of thermodynamics.

Maintained heating of one side and cooling of the other will yield a stable large difference in particle number on the two sides. This represents addition of energy (or improbability) to the system, and hence the situation does not represent a violation of the second law of thermodynamics, which characterizes change in "isolated" systems (which the present one is not, due to the heating and cooling).

15. Eukaryotic cells consist of a number of bounded, semi-autonomous parts, which need to communicate to behave in a coordinated fashion. Briefly illustrate this point with reference to specific components of a eukaryotic cell and how communication can occur among them.

Cellular constituents, such as membranes and ribosomes, depend for their function on proteins which are coded for in DNA. Information for these proteins must diffuse out of the nucleus in the form of RNA. The production of proteins, which represent a way for the nucleus to affect the cell, in turn, however, depends on the presence in the cell of the structures necessary for translation of the RNA into protein.

16. Briefly explain the distinctions between the following three ways of moving materials in biological systems: diffusion, active transport, bulk transport..

Diffusion involves movement of materials down their concentration gradient, is slower since the underlying particle movement is randomly directed, and does not depend on energy. Active transport and bulk transport can both move materials against a concentration gradient, involve directed movement of particles and depend on energy. Active transport may be specific for particular materials while bulk transport moves all materials present in a given transported volume.

17. Briefly describe the ways in which photosynthesis and cellular respiration are reciprocal parts of a cycle.

The former begins with carbon dioxide and water and yields carbohydrate and oxygen. The latter begins with carbohydrate and oxygen and yields carbon dioxide and water. Energy enters the system during photosynthesis and leaves it during cellular respiration, returning the matter involved to its original form.

18. Photosynthesis and cellular respiration are both complex sets of chemical reactions catalyzed by specific enzymes. It is possible to gently dissociate (take apart) either chloroplasts or mitochondria in such a way as to preserve all of their parts and the integrity of all of their enzymes in test tube solutions. Under these circumstances, however, neither photosynthesis nor cellular respiration occurs. Briefly explain why

The electron transport chain involved in both involves a specific three dimensional arrangement of electron exchanging protein molecules to assure that as electrons lose energy this energy is collected in appropriate small amounts for use in pumping protons. Without this arrangement, the proton pumping would not occur. Similarly, the processes depend on the orientation of proteins in a membrane across which a proton gradient can be established. Dissociating the structures disupts the essential three dimensional arrangements.

19. Briefly explain how the nucleus and its associated genetic information are able both to affect the rest of the cell and the cell's surroundings and to be affected by the rest of the cell and its surroundings.

DNA in the nucleus of a cell is transcribed into RNA which in turn diffuses and is translated into proteins in the cytoplasm of a cell. Other materials in the cytoplasm of the cell may diffuse into the nucleus and bind to the DNA in such a way as to alter its production of RNA. Proteins produced in the cell may be secreted to affect the surroundings; similarly, materials in the surroundings may enter the cell, either actively or passively, and ultimately affect production of RNA.

Short Essay (20 points). One page or less, written legibly in the space provided (sample answer in boldface).

20. The evolution of life appears to be a process which creates over time more and more organization (molecular and supramolecular assemblies of greater and greater improbability). Write a brief essay describing, in terms of molecules and macromolecular assemblies, what makes possible the creation of increasing organization, given the second law of thermodynamics, and what drives the process.

The second law of thermodynamics specifies that change can occur in isolated systems if they are initially in an improbable state. and that the direction of such change will always be from a more improbable to a less improbable state. Change from a more improbable to a less improbable state can, however, cause a second system to move in the opposite direction, as shown, for example, by the formation of bubbles during the heating of water. Living systems seem to be a phenomenon of this sort, one in which the continuing loss of organization by the sun (among other things) causes movement and interaction of atoms and molecules needed to create from them less probable assemblies. Interactions of these, again driven by the movement from more improbable to less improbable in the universe as a whole, can in turn lead to improbable assemblies at higher and higher levels of organization. The whole process seems to be driven by the random interactions of elements at successive levels of organization and, in this sense, to constitute an ongoing exploration of the possible forms of organization which can exist given a particular simple set of starting materials and rules of interaction, an exploration which can and will continue only so long as there is a corresponding loss of improbability to sustain it.

Some student responses

Living organisms, even at the cellular level, are created by and kept in existence by molecules obeying the second law of thermodynamics. Often, when one molecule goes from less to more probable, it affects another molecule or structure, causing the second molecule to go from more to less probable. Therefore, the more complex a structure, the more dependent on the second law its existence becomes.

Organisms, over time, have bcome increasingly organized and complex due to the random movement of molecular components. From this random movement comes a gradually more complex form of life. ... Randomness, which fules the gradual increase of molecular improbability, is itself fueld by the conversion of energy into less useful forms.

As the sun moves from a highly improbable ball of mass to chaos, it diffuses out light energy which is the force which drives life on earth. In other words, this movement drives things on earth to move from probable to improbable.

In the face of ever-increasing entropy, disorder, it is important to remember also that the energy being given off by this more from greater improbability to greater probability is not "going anywhere", not vanishing; it is merely changing form ... This constant presence of energy is what allowed and continues to allow life to evolve, along with the characteristic random movement of molecules. ... This explains how improbable assemblies are able to come into existence, but hot why they combine in the ways that they do, as opposed to all of the other billions of possible ways of combining. Perhaps it is once again the result of randomness - two atoms, moving randomly, joined together, found it worked out pretty well, and so on through macromolecular structures, up to multicellular organisms consiting of a bunch of things constantly interacting, giving up energy, taking energy, changing that shape, etc; all because they tried it and it worked. ... [This] does not exclude the existence of a higher force or Force, since we do not know where or how that original energy which created the sun, the earth, the molecules, and all of life (and what it not alive) originated. What we do know, however, is that after that mystery, the original energy and random movement drove the processes that made life and continue to allow it to flourish.

Evolution has led organisms to a state of more complexity, more organization and less probability by channeling the very disorder that occurs naturally.

What drives life and evolution is the ability to transfer the energy released when order breaks down so that another system's order can increase.

The constant movement of molecules and macromolecules results in different combinations of these, which further result in more and more improbable molecular assemblies.

What becomes clear to me is that like each organism there are countless "boxes within boxes" which depend on each other in the same way that the nucleus and the rest of a cell depend on each other. The process drives itself. The question is how did it begin and for what purpose? It seems to me that this is a wonderful fun and creative game. Who or what could possibly be playing? Perhaps the player is one with the game, perhaps they are inseparable.

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