Unit 3 review

7. True or false: all inhibitors bind to enzymes and are irreversible.

False; competitive inhibition can be reversed with increased substrate concentration.

3. True or False: enzymes are consumed by reactions.

False; enzymes are not consumed by reactions

How did highlander mice who had less oxygen still live?

1. The highlander deer mice that lived in higher elevations such as on mountains where there is less oxygen had a genetic difference that allowed hemoglobin to be better able to bind with oxygen in the lungs and take more oxygen into the bloodstream. This allows for the highlander mice, who are at a disadvantage compared to the low lander mice, to still be able to produce enough ATP to power their body.

What does the golgi complex do?

14. The golgi complex, like a mail facility, receives proteins on the cis fase, modifies them and makes sure they are correctly formed, packages them, and sends them out through the trans face into transport vesicles to go to their final destination either inside the cell or outside. In addition, the golgi complex can also add molecular tags to the newly formed proteins just like stamps on envelopes.

Contrast aerobic/anaerobic respiration.

15. In aerobic respiration, 30-32 ATP are created per glucose molecule whereas in anaerobic respiration, only 2 ATP molecules are created per glucose.

Why does oxygen play such an important role in cellular respiration?

16. Oxygen plays such an important role in cellular respiration because it is the final electron acceptor at the end of the ETC. It allows for the fall of electrons to occur and the creation of an H + gradient to power ATP synthesis. Oxidative phosphorylation creates the bulk of ATP (26-28) and without oxygen, oxidative phosphorylation cannot occur which means only glycolysis can occur in anaerobic respiration.

Describe adaptations.

2. Adaptations are the result of evolution. Organisms may develop mutations in their DNA that lead to characteristics or traits that allow for them to be better suited to an environment (remember: organisms never TRY to adapt--it is totally random based on genetic mutations--it is very likely that an organism may not adapt to an environment and therfore die). Then over time, if that trait allows for their survival and reproduction, they will pass that trait down to future generations.

1. List and describe 3 factors that can affect the function of an enzyme.

3 factors that can affect the function of an enzyme are temperature, pH, and chemicals. For temperature, up to a certain point increased temperature can increase enzyme activity. Enzymes function best at a certain pH so when an enzyme is out of its normal pH range, it is unable to function properly since hydrogen bonds in the enzyme will break and change the shape of an enzyme, and shape determines function. Chemicals can inhibit enzyme activity by blocking that enzyme or stopping production of that enzyme.

15. In the Calvin cycle, how many molecules of CO2 are needed to produce one 12-carbon sugar?

3-CO2 molecules (or 3 turns of the calvin cycle, with 1-CO2 per turn) are needed to produce one net molecule of G3P, which is a 3-carbon sugar. Therefore, 12-CO2 molecules (in theory) would be needed to make one 12-carbon sugar. Note: the Calvin cycle does not produce a 12-carbon sugar directly (sucrose), G3P is actually used to create a 6-carbon glucose moleucle. This question is theoretical to get you to thinking about CO2 and its relationship to sugar.

Do organisms control how they adapt?

3. No, organisms do not control how they adapt; adaptations occur randomly based upon genetic mutations that result in an altered phenotype.

4. How is ATP synthesized in glycolysis?

ATP is synthesized in glycolysis through substrate level phosphorylation.

8. Fill in the blanks: the electrons derived from splitting water are used for the synthesis of and .

ATP; NADPH

10. How does fermentation produce alcohol?

After glycolysis, the 2 pyruvate are converted into 2 acetaldehyde after CO2 is released and then 2 NADH are used to create 2 ethanol.

11. How does fermentation produce lactic acid?

After glycolysis, the 2 pyruvate are directly reduced by NADH to form 2 lactate.

1. Differentiate between autotrophs and heterotrophs.

Autotrophs produce their own food from their surroundings whereas heterotrophs live off of other organisms since they are unable to make their own food.

13. What is the meant by the "linear flow of electrons"? How does this differ from the "cyclic flow of electrons"?

Both linear and cyclic electron flow occur in the light reactions (electron transport chain) of photosynthesis. Linear electron flow transforms energy through a flow of electrons through the photosystems and other molecular components built into the thylakoid membrane. This means that the electrons go down the line in the thylakoid membrane to produce both ATP and NADPH. Cyclic electron flow occurs (under some conditions) only at photosystem I and produces ATP without NADPH.

1. What is the overall reaction of cellular respiration?

C6H12O6 + 6 O2 -> 6 CO2 + 6 H2O + energy (ATP and heat)

17. What is the purpose of each phase of the Calvin cycle?

Carbon fixation attaches CO2 to RuBP (via rubisco) to incorporate carbon into an organic compound called 3-PGA. In reduction, ATP and NADPH are used to convert 3-PGA into G3P, which is a reduction reaction. In regeneration, the remaining G3P molecules regenerate RuBP, which allows for more CO2 entering the cycle to be fixed.

2. How do enzymes affect activation energy? (list the ways enzymes can do it specifically)

Enzymes affect activation energy by lowering it so that reactions can occur faster. To lower the activation energy, enzymes orient substances correctly, strain their bonds, provide a favorable microenvironment, or directly participate in the reaction.

2. Describe how enzymes are able to "speed up" reactions.

Enzymes are able to speed up or catalyze reactions by lowering the activation energy which allows for reactions that require a lot of energy (endergonic) to occur earlier and at a faster rate.

1. Are enzymes necessary for all living things to function? Discuss your thoughts here. (mention ex of a process that takes LONGER without)

Enzymes are necessary for all living things to function because they allow for important and vital chemical reactions to occur quickly. For example, the hydrolysis of sucrose to glucose takes nearly 1000 years, but enzymes allow cells to do to process this conversion within milliseconds.

2. Describe how enzymes are named.

Enzymes' names usually end in -ase, and they are named after the reaction or substances in the reaction that they are catalyzing.

5. True or false: the light independent reactions are also known as the dark reactions because they can only happen in the absence of light.

False. The light independent reactions are called the dark reactions because they do not require sunlight not because they only happen in the absence of light.

7. Critically think: why do fats store more energy than carbohydrates? Go back to the Mighty Mouse video/reading and your Unit 1 packet to help.

Fats store more energy than carbohydrates because of the fatty acid chains. These fatty acid chains contain many carbons.When these are broken down they release energy.

2. How does oxidation and reduction play a role in cellular respiration?

Glucose is oxidized in a series of steps, which transfers the electrons to a lower energy state, releasing energy (this is the key to why cellular respiration happens, it wants to use this energy to power cellular work) in the form of ATP. NAD+ is reduced to NADH. Oxygen is also reduced into H2O as it is the final electron acceptor of the electron transport chain.

11. Do you support this claim: the light reactions do not depend on the Calvin cycle. Why or why not?

I do not support the claim that the light reactions do not depend on the calvin cycle because the calvin cycle provides the light reactions with NADP+ and ADP + Pi to be reused and regenerated in the light reactions. Without these molecules, there would be nothing to accept electrons in photosystem I and ATP to be synthesized at the ATP synthase.

12. Do you support this claim: the Calvin cycle does not depend on the light reactions. Why or why not?

I do not support this claim that the Calvin Cycle does not depend on the light reactions because the light reactions provide ATP and NADPH needed to fix carbon dioxide and produce G3P. Without these molecules, the Calvin Cycle would not be able to reduce carbon down to G3P and regenerate RuBP.

8. Predict what would happen to a cell if it was exposed to an irreversible inhibitor, like cyanide.

If a cell was exposed to an irreversible inhibitor like cyanide, the enzymes in the cell would not be able to function. Therefore, cellular processes would not be able to occur. Since cyanide is an irreversible inhibitor, the enzymes will be blocked forever and the cell would not fulfill its necessary functions and would eventually die.

3. If a mutation occurs on a segment of DNA that codes for an enzyme, what is most likely to happen to the enzyme?

If a mutation occurs on a segment of DNA that codes for an enzyme, the enzyme will likely be nonfunctional since the mutation will cause a change in the enzyme's shape and therefore a change in the function.

8. What happens to muscle cells if they deplete their supply of oxygen and ATP?

If muscle cells deplete their supply of ATP and oxygen, they go through lactic acid fermentation.

9. Describe step-by-step what would happen if oxygen was removed from the ETC.

If oxygen was removed from the ETC, there would be no final electron acceptor to accept the electrons and remove them from the mitochondria. This means that the electrons would get backed up in the ETC and the ETC would eventually shut down segment by segment as the electrons build up (because this bulidup prevents redox reactions from occuring). This also means that there would be no ATP synthesis since no ETC means no H+ gradient and no chemiosmosis. Each step in cellular respiration would get backed up until glycolysis. The cell would not receive sufficient amount of ATP and would eventually die.

12. Justify this statement, "Cells make ATP by oxidative phosphorylation."

In the inner mitochondrial membrane, there is the ETC, in which the transport proteins alternate between reduced and oxidized states as the electrons are passed down. This ETC also pumps H+ across the membrane which powers the ATP synthase that phosphorylates ADP to create ATP.

Describe the phenomenon known as "induced fit."

Induced fit is when a substrate binds to an enzyme on the active site and the enzyme will change the shape of their active site so that the substrate can bind better.

9. Knowing about light and its importance to plants, create an explanation for why leaves change color in fall?

Leaves change color in the fall because the days become shorter and there is less sunlight. This causes the leaf cells to stop producing a lot of chlorophyll, which means that other pigments including carotenoids will be absorbing the light and they absorb at wavelengths that represent red and yellow and orange instead of green.

6. What is the primary electron carrying molecule in photosynthesis?

NADPH

4. Does the rate of an enzyme catalyzed reaction increase exponentially if the substrate concentration increases?

No, the rate of an enzyme catalyzed reaction will not increase exponentially if the substrate concentration continually increases. This is because at a certain point, all enzymes would be saturated with that substrate and thus the reaction would be working at its max rate of catalysis.

Why does photorespiration occur?

Photorespiration occurs when plants close their stomata on hot, dry days, and there is O2 trapped inside the plant but no CO2 for rubisco to bind with so it binds with O2 instead, which decreases photosynthetic output.

10. How is photosynthesis a redox process?

Photosynthesis is a redox process because both oxidation and reduction processes occur. The electrons garnered from the splitting of water in the light dependent reactions go through a series of redox reactions to eventually reduce NADP+ to NADPH; electrons are being transferred from one molecule to the next which means they are being reduced and oxidized rapidly. In the Calvin cycle, CO2 is reduced to carbohydrates, which serves as fuel for the plant.

7. In which organelle does photosynthesis take place? More specifically, where does each stage of photosynthesis take place?

Photosynthesis takes place in the chloroplast. The light dependent reactions take place in the thylakoid membranes and the Calvin Cycle takes place in the stroma.

17. Compare and contrast photosynthesis and cellular respiration

Photosynthesis: produces glucose and oxygen, takes place in the chloroplast, only autotrophs can do this, NADP+ is the final electron acceptor in ETC, 2 stages, NADPH is the electron carrier, anabolic. Cellular respiration: produces water, carbon doxide, and releases energy, takes place in cytoplasm and mitochondria, oxygen is final electron acceptor in ETC, produces ATP from breakdown of glucose, NADH and FADH2 are electron carriers, catabolic. Both: have ETCs, have ATP synthase producing ATP using H+ gradient, multiple stages

3. Plants are primary producers, what does this mean?

Plants are referred to as primary producers because they produce their own food and are the ultimate sources of organic compounds for all heterotrophs.

14. Justify this claim: rubisco is the enzyme responsible for producing the world's food.

Rubisco is the enzyme responsible for producing the world's food because it is the enzyme involved in the catalysis of carbon fixation. Carbon fixation is the first step in the Calvin Cycle, which produces sugars from carbon dioxide. Because rubisco is able to fix carbon dioxide into G3P, plants are able to use these sugars to grow. Plants are primary producers and provide heterotrophs with food which means that when organisms eat plants, heterotrophs receive their sugars produced from rubisco. So therefore, rubisco does produce the world's food.

2. Explain how temperature can increase, decrease, and stop an enzyme's function.

Temperature can increase an enzyme's function within an acceptable range by speeding up the movement of the molecules, thereby increasing the chances of collision between the enzyme and substrate. Temperature can also decrease an enzyme's function if it goes outside of the enzyme's acceptable temperature range since all enzymes work optimally at certain temperatures. Temperature can completely stop an enzyme's function when the change in temperature is extreme, thus causing the enzyme to denature.

6. What is the purpose of the citric acid cycle?

The citric acid cycle turns Acetyl CoA into citrate and releases CO2 while creating more ATP (energy) and more NADH and FADH2 (electron carriers).

3. What steps of glycolysis require energy? What steps release energy?

The energy investment stage requires energy since ATP is used to phosphorylates glucose. The energy payoff stage releases energy produced by substrate level phosphorylation.

2. What is the primary purpose of photosynthesis?

The primary purpose of photosynthesis is to convert light energy into chemical energy that plants and other autotrophic organisms can use to fuel their cells.

5. What happens to the pyruvate that is produced via glycolysis?

The pyruvate enters the mitochondria and is oxidized into Acetyl CoA.

16. What are the three phases of the Calvin cycle?

The three phases of the Calvin cycle are carbon fixation, reduction, and regeneration of RuBP.

5. True or false: enzymes oscillate between active and inactive forms.

True

4. True or false: photosynthesis has two stages.

True. light dependent reactions and the Calvin Cycle.

1. How does the structure of ATP allow for the molecule to store and release energy?

When the bonds between the second and third phosphates break, this releases energy. This release of energy is due to the lowering of free energy and not from the bond itself.

which products increase the entropy of U and Ur surroundings

heat, CO2, O2, food that comes in your body

5. Of the four classes of macromolecules, to which do enzymes belong?

proteins