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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 consists of nine multiple choice questions, nine short answer questions, and two short essay questions (from which you are to pick one to answer), and is due at the beginning of class on Monday, 9 November. Once you have completed studying for the exam, you are free to look at the questions at any time, and are encouraged to do so well prior to writing your answers so as to give yourself time to think about them. While thinking about the questions, please do not consult your notes or textbook or talk with others about them. The examination is designed to take an hour to write your answers, and you should gauge the appropriate length of answers accordingly. You may, however, take up to two hours to actually write the answers, to assure that you don't feel pressed for time. Whether you are entirely confident with your answers to any given question or not, be sure to do the best job you can with each question. Answers to multiple choice and short answer questions should be provided on the exam itself and in the space provided. Please be legible and put your name on the top of each page. Your essay may be written legibly in the space provided or may be typed and attached to the exam. In either case, be sure to indicate which question you are responding to and write no more than one page.

MULTIPLE CHOICE. (2 pts ea) 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) the color of an organism's eyes.

2. The three-dimensional structure of a protein: A) is determined and 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 by genetic information.

3. The second law of thermodynamics says that in any isolated system things move from a less probable (more organized) to a more probable (less organized) 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 temporary existence of a concentration difference on the two sides of a partition which allows passage of the substance; C) the existence of the improbable assemblies of atoms, molecules, cells, and organisms which constitute life; D) none of the above.

4. Which of the following is not a membrane bound organelle? A) nucleus; B) endoplasmic reticulum; C) Golgi apparatus; D) ribosome.

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

6. Mitochondria are found in: A) eukaryotic animal cells; B) eukaryotic plant cells; C) both eukaryotic animal and plant cells; D) prokaryotic cells.

7. ATP is synthesized during: A) cellular respiration; B) photosynthesis; C) both cellular respiration and photosynthesis; D) only under highly unusual circumstances.

8. Carbon is reduced during: A) cellular respiration; B) photosynthesis; C) both cellular respiration and photosynthesis; D) only under highly unusual circumstances.

9. The electrons lost by a chlorophyll molecule during photosynthesis are: A) replaced by electrons from water molecules; B) replaced by hydrogen ions; C) replaced by the breakdown of ATP; D) not replaced.

SHORT ANSWER (3 pts ea). Four sentences or fewer. Write legibly in the space provided (sample answers in boldface).

10. 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 time), and how it can in addition serve as an energy source for termites but not for people.

Cellulose spontaneously breaks down into a more probable state but does so very slowly because of a high energy of activation barrier. For this reason it remains intact and solid for long periods of time. Termites but not people have enzymes which can lower the energy activation barrier, causing cellulose to break down more rapidly and hence making available useable energy from it.

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

Enzyme structure is critical to function, depends on weak molecular interactions, and hence is highly sensitive to both temperature (random movement) and pH (electrical environment). Substantial variations in either temperature or pH will therefore produce major disruptions in the web of chemical reactions which constitute living systems, fish included.

12. Changes in protein shape play important roles in cellular function. Give two illustrative examples.

In non-competitive inhibition, the binding of one molecule to a receptor site on an enzyme changes its shape so that molecules whose reaction is normally catalyzed no longer fit a second receptor site. Changes in protein shape also underlie the ability of cells to move and to move substances within themselves.

13. Imagine a box with a partition that allows particles to move form 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 of the box, explaining what accounts for both the similarities and the differences in the two cases.

In both cases, the box will end up in a state of dynamic equilibrium, with particles continuing to move back and forth but roughly equal numbers of particles on each side of the box at any given time. It will take some time to reach this state in the first case while in the second the starting condition will simply be maintained.

14. Large regions of DNA molecules code for proteins which leave the vicinity of the DNA molecules and act in the cytoplasm of the cell. Other regions play important roles without coding for such proteins. Briefly describe two such functions.

Some regions of DNA code for regulatory proteins which act on the DNA itself to enhance or diminish the expression of regions coding for proteins which act outside the nucleus. Other regions of DNA serve as the binding sites for such proteins.

15. Briefly describe the sequence of transformations in going from information in DNA to a functional protein molecule.

The information in a DNA molecule is represented in a linear sequence of bases. This is first transcribed into a corresponding sequence of bases in a messenger RNA molecule and subsequently translated into the linear sequence of amino acids in a polyptide chain. The latter folds into a functional protein molecule and each step in the sequence depends on a host of other molecules.

16. Briefly contrast diffusion and active transport as methods for moving materials from one place to another in a cell.

Active transport is an energy dependent process and can move materials both rapdily and against a concentration gradient. Diffusion is a spontaneous process. Materials are moved more slowly and only down a concentration gradient.

17. Briefly describe ways in which photosynthesis and cellular respiration are reciprocal parts of a cycle and ways in which they are not.

Carbon dioxide and water are used to make glucose and oxygen in photosynthesis, while glucose and oxygen are combined to yield carbon dioxide and water in cellular respiration; the same atomic constitutents are simply cycled back and forth between a more probable and a less probable state. Photosynthesis requires energy from the sun, while cellular respiration yields usable energy in the form of chemical bonds in ATP. Usable energy is passed through the system, rather than being cycled back and forth.

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

Both processes depend not only on a host of functional enzymes but also on a particular three dimensional arrangement of those enzymes rather than on the random arrangement of them which would be present in a test tube solution. The electron transport chain, for example, depends on neighborhood relations among proteins, as well as their orientatiion across a membrane so as to allow the creation of a proton gradient.

SHORT ESSAY (20 pts). Pick one of the following two questions to answer, being sure to indicate which you are writing about. One page or less, written legibly in the space provided or typed and attached.

A. "Genetic information is likely to influence virtually all aspects of an organism's structure and behavior, but not to wholely determine any aspect." Write a brief essay justifying this assertion given what you currently know of the molecular basis of genetic information and its expression.

B. 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 molecular assemblies, what makes possible the creation of increasing organization, given the second law of thermodynamics.

Some student responses

A. --- Genetic information in the form of DNA provides a set of possibilities for what can happen in a cell .... However, there are many possible things that can change or influence the effects of any process during the production of proteins.

A. --- In conclusion, the nucleus is influential but is also influenced by factors beyond its control. The entire cell, not just the nucleus, works together to contribute to the life of the cell.

A. --- The process of transmitting genentic information, which is largely stored in the nucleus, to the rest of the cell is a long and complicated one. Due to all of the steps and structures that are involved, an organism's phenotype does not directly reflect its genotype. Additionally, there are influences that control the genetic information itself ...

B. --- Living organisms are examples of things becoming orderly because in so many other areas things are becoming disorderly.

B. --- Thus, the Second Law of Thermodynamics demonstrates the importance of the Brownian motion observed in the laboratory. Far from a trivial molecular phenomenon, the tendency toward dynamic equilibrium and probability over large time scales maintains the improbable assemblies of life.

B. --- The sun is the driving force behind greater improbability ... Out of probability we get improbability.

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