BIO 110- Chapter 6 - Review

What initial observation led scientists to hypothesize that brown fat may be activated by cold temperatures?

Brown fat tissue was found at higher levels when the scans were taken during cold weather.

___________________ is always lost during photosynthesis and cellular respiration?

Energy

___________ generates fewer molecules of ATP because it contributes its electrons further along the electron transport chain?

FADH₂

If you opened a wine vat, would the yeast inside continue to perform alcoholic fermentation? Briefly explain your answer with some details about what would happen.

No, because they would be exposed to atmospheric oxygen and they would preferentially per- form aerobic respiration.

The driving force behind oxidative phosphorylation is ____________? a. oxygen b. carbon dioxide c. NADH d. H₂O

a. Oxygen

Plants release what gaseous by-product as a result of photosynthesis? a. O₂ b. CO₂ c. H₂O d. Solar energy

a. O₂

________________________ uses the energy found within a proton gradient to drive the syn- thesis of ATP?

ATP Synthase

How is ATP produced in cells; what is the difference between the energy-producing process in animal cells and plant cells? How much ATP is produced?

Answer 1: How living things produce usable energy is important not only from the perspective of understanding life, but it could also help us to design more efficient energy harvesting and producing products - if we could "mimic" how living cells deal with their energy balance, we might be able to vastly improve our technology. For example, a plant is a much better harvester of sunlight than even our best solar panel. And of course, if we understand energy use, it can also help us deal with human diseases such as diabetes. Now, the answer to your question can be found in any basic biology text book, but sometimes, there is so much information packed into such a text book that it can be difficult to extract the information you need or more often, to view all of that information in a larger context. Let's try to tackle your question in several parts. First, we need to know what ATP really is - chemically, it is known as adenosine triphosphate. ATP is a usable form of energy for cells - the energy is "trapped" in a chemical bond that can be released and used to drive other reactions that require energy (endergonic reactions). Photosynthetic organisms use energy from sunlight to synthesize their own fuels. They can convert harvested sunlight into chemical energy (including ATP) to then drive the synthesis of carbohydrates from carbon dioxide and water. When they synthesize the carbohydrates, oxygen gets released. Globally, more than 10 billion tons of carbon is "fixed" by plants every year - this means that carbon molecules are converted from being part of a simple gas (carbon dioxide) into more complex, reduced molecules (carbohydrates), making carbon available as food for non-photosynthesizers (and of course, providing oxygen). They use some of the carbohydrate for their own growth and reproduction. It is pretty remarkable when you think about it - have you been to Sequoia National Park or seen the redwoods along our northwest coast? Massive trees, right? Think about the fact that most of that mass is in the form of carbon that was pulled out of the air as carbon dioxide! The process of photosynthesis is two-part. First, there are the light reactions, where light is converted into chemical energy (a reduced electron carrier and ATP). This occurs in the thylakoids (stacked membranes) of the chloroplasts. The ATP and electron carriers are then used in a second set of reactions, called the light-independent reactions. This also occurs in the chloroplasts, but in an area called the stroma. In this case, carbon dioxide gets used to produce sugars in a series of reactions called the Calvin Cycle, C4 photosynthesis, and crassulacean acid metabolism. You can look in any basic bio textbook to see how much "energy" or "sugar" is produced in each step of the process. In non-photosynthesizers, the fuel has to be consumed. The most common chemical fuel is the sugar glucose (C6H12O6)... Other molecules, such as fats or proteins, can also supply energy, but (usually) they have to first be converted to glucose or some intermediate that can be used in glucose metabolism. Now this brings us to the next part - how do we go from glucose to ATP? This is achieved through the process of "oxidation" - and this is carried out through a series of metabolic pathways. Complex chemical transformations in the cell occur in a series of separate reactions to form each pathway, and each reaction is catalyzed by a specific enzyme. Interestingly, metabolic pathways are similar in all organisms, from bacteria to humans. In eukaryotes (plants and animals) many of the metabolic pathways are compartmentalized, with certain reactions occurring in specific organelles. Basically, cells trap free energy released from the breakdown (metabolism) of glucose. This energy gets trapped in the ATP as it converts from ADP to ATP by the addition of phosphate. There are 3 main pathways for harvesting energy from glucose: Glycolysis - begins glucose metabolism in all cells to produce 2 molecules of pyruvate. Occurs outside of mitochondria, usually in cytoplasm. Cellular Respiration - uses oxygen from the environment and converts each pyruvate to three molecules of carbon dioxide while trapping the energy released in this process in ATP. There are 3 sub-pathways of cellular respiration - pyruvate oxidation, the citric acid (Krebs or Tricarboxylic Acid) cycle and the electron transport chain. Occurs in different sub-compartments of mitochondria. Fermentation - converts pyruvate into lactic acid or ethanol; does not need oxygen. It is not as efficient as cellular respiration; it occurs in the cytoplasm. In terms of how much ATP is produced, you can look in your basic texts and assess how many ATPs are used versus how many are produced for each aspect of metabolism Answer 2: ATP is created through a complex enzyme-driven process. There are a couple of ways this works in cells: -glycolysis, in which glucose is broken up into two subunits, called pyruvate, which creates two units of ATP per molecule of glucose. This happens in the cytoplasm, in both animal and plant cells. -respiration, in which pyruvate is combined with oxygen to form carbon dioxide and water, which creates a lot of ATP per unit of pyruvate (16 I think). Obviously, glycolysis has to happen first, in order to make the pyruvate. This happens in the mitochondrion, which likewise exists in both animals and plants. -light-dependent photosynthesis, in which electrons are cycled around photosynthetic pigments after being jostled around by mid-high-energy photons (light particles), which filter through an electron pump that makes ATP. This happens in chloroplasts, and as such only occurs in plants. Note: there is one more major (eukaryotic) ATP-generating reaction, called "fermentation", which takes pyruvate and turns it into carbon dioxide and ethyl alcohol. Neither animals nor plants can do this, but fungi can do it. There is also light-independent photosynthesis, which USES ATP and creates glucose from carbon dioxide and water, producing oxygen as a waste product. This is really an energy storage mechanism, so that the organism doing it can later burn the glucose through glycolysis and respiration. This also happens in chloroplasts, so plants can, and animals can't.

CO₂ is a gaseous by-product of cellular respiration that you exhale with each breath. Briefly explain where the CO₂ comes from?

The CO₂ comes from the organic molecules (food) that you consume and is a by-product of cellular respiration.

The overall chemical equation for cellular respiration is: C₆H₁₂O₆ + 6O₂ →→→→ 6CO₂ + 6H₂O Briefly explain why the equation has multiple arrows.

The arrows represent the fact that cellular respiration consists of multiple chemical reactions. * Cellular respiration is the chemical reaction in which glucose and oxygen are turned into water, carbon dioxide, and energy (ATP). In this reaction, glucose and oxygen are reactants, while water, carbon dioxide, and energy (ATP) are products.

How are photosynthesis and cellular respiration linked on a molecular level?

They are linked in that the products of one are the reactants of the other. How are photosynthesis and cellular respiration related to each other? Cellular respiration and photosynthesis act as parallel processes. They are both similar in that both are designed to harvest energy through synthesis of ATP. However, the direction of electron movement is opposite in the electron transfer chain. Additionally, cellular respiration uses food to harvest energy, while photosynthesis uses light energy.

Students frequently have the misconception that plant cells don't perform cellular respiration. Briefly explain the basis of this misconception?

This misconception arises because plant cells perform photosynthesis, which creates the as- sumption that plant cells do not perform cellular respiration.

Which of the following is the correct order of the main stages of cellular respiration? a. Citric acid cycle, glycolysis, oxidative phosphorylation b. Glycolysis, citric acid cycle, oxidative phosphorylation c. Citric acid cycle, oxidative phosphorylation, glycolysis d. Oxidative phosphorylation, glycolysis, citric acid cycle

b. Glycolysis, citric acid cycle, oxidative phosphorylation *Cellular respiration uses energy in glucose to make ATP. Aerobic ("oxygen-using") respiration occurs in three stages: glycolysis, the Krebs cycle, and electron transport. In glycolysis, glucose is split into two molecules of pyruvate.

Any substance that inhibits the transportation of oxygen from the lungs affects _____________? a. photosynthesis b. cellular respiration c. chloroplasts d. none of the above

b. cellular respiration

A drug is administered to a person that causes the inner mitochondrial plasma membrane to become permeable to H+. What effect will this have on oxidative phosphorylation? Are there possible repercussions for the other stages of cellular respiration?

A weight loss drug decreases the synthesis of ATP by making the mitochondrial membrane permeable to H+, allowing H+ to leak into the intermembrane space. It prevents ATP from being made by blocking access of H+ to ATP synthase.

What does oxidation mean?

All reactions which involve electron flow are considered oxidation-reduction reactions. The basic definition can be defined as: One reactant is oxidized (loses electrons), while another is reduced (gains electrons). For instance in cellular respiration, the oxidation of glucose (C6H12O6) produces CO2.

Fats are hydrophobic and carbohydrates are hydrophilic. Use this information to explain why humans store the majority of their excess energy as fat and not carbohydrates.

Because fats will not require water for storage.

____________is a set of metabolic reactions and processes that take place in the cells of organisms to convert biochemical energy from nutrients into adenosine triphosphate (ATP), and then release waste products.

Cellular respiration is a set of metabolic reactions and processes that take place in the cells of organisms to convert biochemical energy from nutrients into adenosine triphosphate (ATP), and then release waste products.

True or false: The transfer of H atoms from glucose to oxygen does not represent redox reactions. If false, make it a correct statement.

False, it does represent redox reactions, as oxygen gas is reduced.

True or false: Blood traveling from your leg muscles to the lungs would be high in oxygen. If false, make it a correct statement.

False, it would be low in oxygen.

True or false: A substance that makes the inner mitochondrial membrane leaky to H1 (H1 would be able to leak across the membrane at points other than ATP synthase) increases ATP production in mitochondria. If false, make it a correct statement.

False, it would decrease ATP production as ATP synthase efficiency would be reduced.

Fermentation is essentially glycolysis because glycolysis does not require _________________ to function?

Fermentation is essentially glycolysis because glycolysis does not require oxygen to function.

List two sources of evidence that indicate glycolysis is extremely old?

Glycolysis is universal, and it does not occur within a membrane-bound organelle.

You are taking a road trip from Chicago to Denver. The trip is going to take roughly 15 hours. At the start of your trip, you get a 96-oz Mega Gulp from 11-seven of Mountain Mist. This beverage will have roughly 1,360 kcal. How long into your trip will you have burned the calories from this drink? Refer to Figure 6.4 in your textbook on page 91.

It would actually take longer than your trip, a bit over 22 hours.

Briefly explain why a teeter-totter is a good analogy for describing how reductions and oxidations always go together?

It's a good analogy because, for every reduction, there is an oxidation, and vice versa. This is similar to a teeter-totter: When one side goes up, the other has to go down.

Match the following stages of cellular respiration with the correct characteristics. Some stages may have more than one characteristic or share characteristics. For glycolysis, put A; for citric acid cycle, put B; and for oxidative phosphorylation, put C. Occurs in the cytosol: ____________ Occurs in the mitochondria: ____________ Involves the splitting of glucose: ____________ Produces molecules of NADH: ____________ Produces ATP: ____________ Produces CO2: ____________ FADH2 shuttles electrons to the electron transport chain: ____________ Occurs in a plant cell: ____________ Occurs in an animal cell: ____________ Uses the potential energy of a H gradient: ____________ Produces molecules of FADH2: ____________ Substrate-level phosphorylation occurs: ____________

Occurs in the cytosol: A - glycolysis Occurs in the mitochondria: B & C - citric acid cycle & oxidative phosphorylation Involves the splitting of glucose: A - glycolysis Produces molecules of NADH: A - glycolysis and B - citric acid cycle Produces ATP: A, B, & C - glycolysis, citric acid cycle & oxidative phosphorylation Produces CO2: B - oxidative phosphorylation FADH2 shuttles electrons to the electron transport chain: C - oxidative phosphorylation Occurs in a plant cell: A, B, & C - glycolysis, citric acid cycle & oxidative phosphorylation Occurs in an animal cell: A, B, & C - glycolysis, citric acid cycle & oxidative phosphorylation Uses the potential energy of a H gradient: C - oxidative phosphorylation Produces molecules of FADH2: B - citric acid cycle Substrate-level phosphorylation occurs: A - glycolysis and B - citric acid cycle

Oxidation-reduction?

Oxidation-reduction in cellular respiration differs from photosynthesis in the direction of the electron transfer. In respiration, electrons are transferred from glucose molecules to oxygen. Therefore, glucose is oxidized, while oxygen is reduced in cellular respiration. However, in photosynthesis, electrons travel from water to CO2. In cellular respiration electrons travel from organic molecules to oxygen, while in photosynthesis electrons travel from oxygen in water to a carbon-based molecule.

Redox Reactions?

Redox Reactions are an important process for cellular respiration and photosynthesis. These reactions are also known as oxidation-reduction. In a redox reaction one reactant transfers partially or completely one or more electrons to another. The electron-losing reactant is known as the reducing agent and is considered oxidized in the reaction. The substance gaining electrons is referred to as the oxidizing agent and is considered reduced.

What must proteins be broken down into before they can be burned as energy? Refer to Figure 6.15 on page 102 in your textbook.

They must be broken down into amino acids. Proteins in food are broken down into pieces (called amino acids) that are then used to build new proteins with specific functions, such as catalyzing chemical reactions, facilitating communication between different cells, or transporting biological molecules from here to there. When there is a shortage of fats or carbohydrates, proteins can also yield energy.

Strenuous exercise uses up all ATP stores and causes a build-up of lactic acid.

This is a toxic (poisonous) substance which causes the muscles to stop working. Lactic acid can only be removed in the presence of oxygen and upon completion of hard strenuous exercise it is essential that the oxygen debt is repaid. Large amounts of oxygen are needed for this oxygen recovery. This is why we pant after hard exercise. In this way ATP stores are replenished and lactic acid removed from the muscular system.

True or false: Brown fat contains mitochondria. If false, make it a correct statement.

True

True or false: Glycolysis and the citric acid cycle both function as metabolic interchanges where the products of their chemical reactions can also be used for biosynthesis. If false, make it a correct statement.

True

In lactic acid fermentation, __________ becomes the target of reduction by NADH? a. pyruvate b. lactate c. glucose d. ATP

a. pyruvate

A buildup of ____________ initiates the inhibition of an enzyme that functions early in glycolysis. a. ADP b. ATP c. glycerol d. amino acids

b. ATP Lactic Acid

The only portion of cellular respiration that is cyclic is ____________. a. glycolysis b. the electron transport chain c. the citric acid cycle d. the oxidation of pyruvate

c. the citric acid cycle

The formation of NaCl (table salt) involves an atom of Na giving an electron to an atom of Cl. a. This would be considered a redox reaction. b. Na got oxidized. c. Cl got reduced. d. All of the above are true statements regarding the formation of NaCl.

d. All of the above are true statements regarding the formation of NaCl.