EBIO Midterm #2 Practice Questions & Clickers

What is the formula of the molecule made by adding one fructose to a molecule of lactose? A) C18H32O16 B) C12H24O12 C) C18H34O17 D) C18H30O15 E) C12H22O11

A) C18H32O16 Narration: Fructose is a hexose monosaccharide; lactose is a disaccharide made of two hexoses (glucose and galactose). The lactose molecule was already formed from the dehydration synthesis of two hexoses, i.e., 2 x C6H12O6 - H2O = C12H22O11. Adding another hexose (fructose) to lactose through dehydration synthesis yields C12H22O11 + C6H12O6 - H2O = C18H32O16

Four of the five statements below apply to both photosynthesis and respiration. Which does NOT? A) The energy for ATP formation comes from energy-rich bonds of sugars. B) Flow of protons downhill from high to low concentration through an ATP synthase converts the potential energy of a proton gradient to ATP. C) Electrons give up their energy step by step while passing through an electron transport chain. D) High-energy electrons pass through an electron transport chain. E) Electrons provide the energy to move protons from low to high concentration.

A) The energy for ATP formation comes from energy-rich bonds of sugars. Narration: In both photosynthetic and mitochondrial electron transport chains, high-energy electrons pass through the chains, give up their energy step by step, and move protons uphill from low to high concentration. In both cases, downhill flow of protons through an ATP synthase fuels ATP formation. The energy for ATP formation comes from energy-rich food molecules only in respiration (in either plants or animals). In contrast, the energy for ATP formation in photosynthesis is provided by sunlight.

Deduce what type of transport is involved. How does movement of protons through the electron transport chain occur? Via A) active transport B) passive transport

A) active transport

The oxygen released in photosynthesis is a by-product of which specific reaction? A) extraction of electrons from water molecules B) addition of a phosphate group to ADP C) conversion of CO2 to sugar D) synthesis of water molecules E) extraction of electrons from CO2

A) extraction of electrons from water molecules Narration: The electrons that flow through the photosynthetic electron transport chain are obtained by splitting H2O into two electrons, two protons, and oxygen. Oxygen is a byproduct of water splitting. Synthesis of H2O from electrons, protons, and oxygen occurs only in mitochondria. No electrons are extracted from CO2. CO2 is converted to sugar in the Calvin cycle by adding electrons and protons to form C-H bonds; no oxygen is released in this process. (You do not need to know the following details for the exam: One oxygen from CO2 winds up in the sugars formed. The second oxygen from CO2 winds up as part of a phosphate group. ATP transfers a high-energy phosphate group to a three-carbon product and when the phosphate group comes off again later, it takes an oxygen with it.)

NAD+ can be loaded with high-energy electrons in which reaction(s) or location(s)? A) in the citric acid cycle and in glycolysis B) at the end of the mitochondrial electron transport chain C) at the end of the photosynthetic electron transport chain D) only in glycolysis E) only in the citric acid cycle

A) in the citric acid cycle and in glycolysis Narration: At the end of the mitochondrial electron transport chain, electrons are passed on to oxygen. At the end of the photosynthetic electron transport chain, electrons are loaded onto NADP+. NAD+ can be loaded with high-energy electrons in both glycolysis and the citric acid cycle.

Where in a leaf are ATP synthases located? A) only in the thylakoid membrane and the inner mitochondrial membrane B) only in the inner mitochondrial membrane C) in the thylakoid membrane, the cell membrane, and the inner mitochondrial membrane D) only in the cell membrane E) only in the thylakoid membrane

A) only in the thylakoid membrane and the inner mitochondrial membrane Narration: Leaves have both chloroplasts and mitochondria, each with ATP synthases. The outer cell membrane contains only ATP-using pumps, but no ATP-forming turbines.

Deduce how the movement of protons through the mitochondrial ATP synthase occurs. Via A) passive transport B) active transport C) simple diffusion

A) passive transport

Prokaryotes carry out all of the following except: A) movement work using motor proteins. B) ATP formation in mitochondria. C) active transport of substances across membranes. D) ATP formation using energy sources from the environment. E) energy-dependent synthesis of large molecules.

B) ATP formation in mitochondria. Narration: Recall what cellular features prokaryotes do and don't have, and what functions these features carry out. Prokaryotes do not have mitochondria, chloroplasts, or membranes around their nucleus. They therefore cannot carry out functions associated with mitochondria, such as ATP formation in mitochondria. Prokaryotes do have cell membranes and use energy sources to produce ATP; they use this ATP to fuel all their cellular work, such as movement via motor proteins, transport of substances across membranes, and synthesis of molecules needed in the cell.

"Fast-twitch" muscle fibers are used for sprints and "slow-twitch" fibers for extended exercise. Predict which is correct: A) Fast-twitch fibers store mostly fat, while slow-twitch fibers store mostly glycogen B) Fast-twitch fibers store mostly glycogen, while slow-twitch fibers store mostly fat C) Both fiber types store mostly glycogen D) Both fiber types store mostly fat

B) Fast-twitch fibers store mostly glycogen, while slow-twitch fibers store mostly fat

Four of the five bonds or molecules contain high-energy electrons that enter the process of cellular respiration. Find the exception. A) food molecules B) H-O-H C) proteins D) C-H bonds E) sugars

B) H-O-H Narration: The source of high-energy electrons for respiration is any food molecule with C-H bonds, like sugars, proteins, and other food molecules. Water does not contain any high-energy electrons. Water is merely the source of the electrons that become energized by sunlight and are fed into the photosynthetic electrons transport chain in the chloroplast. These electrons will eventually work their way into the process of respiration. Cellular respiration forms water when oxygen picks up electrons at the end of the mitochondrial electron transport chain.

Predict the relative rates of photosynthesis versus respiration over the lifespan of a green leaf. A) Overall photosynthesis rates and respiration rates of a leaf should be the same. B) Overall photosynthesis rates of a leaf should be higher. C) Overall respiration rates of a leaf should be higher.

B) Overall photosynthesis rates of a leaf should be higher.

Deduce how the movement of protons from the mitochondrial matrix into the intermembrane space occurs. Via A) passive transport B) active transport C) simple diffusion

B) active transport

Complete the sentence correctly. ATP is produced: A) only by producers. B) by producers and consumers. C) in respiration, but not in photosynthesis. D) as a convenient storage form of energy in producers. E) only by consumers.

B) by producers and consumers. Narration: While ATP for cellular work is produced in cellular respiration in both plants (producers) and consumers, ATP is also produced in photosynthesis; the light reactions produce ATP that fuels the conversion of CO2 to sugar. The highly reactive, unstable ATP cannot be used for energy storage.

Predict in which environments C3 plants versus C4 plants should each be most successful. C3 plants will be most successful in __________ environments, and C4 plants will be most successful in __________ environments. A) sunnier and drier; less sunny but moister B) less sunny but moister; sunnier and drier C) less sunny but drier; sunnier and moister D) sunnier and moister; less sunny but drier

B) less sunny but moister; sunnier and drier

Which dietary carbohydrates will most strongly activate genes that promote fat storage in humans? A) sugars and amylose B) sugars and amylopectin C) all starches D) cellulose

B) sugars and amylopectin Narration: High intake of free sugars, as well as of starches that can be rapidly broken down into free sugars, strongly increases blood sugar levels and promote fat storage. The starch amylopectin has many branches, allowing access to many sugar-cleaving enzymes at the same time, which permits rapid breakdown into many glucose molecules. In contrast, the starch amylose is a single strand of hundreds of glucose molecules without branches, which only allows gradual clipping of sugars from the two ends. Humans do not synthesize an enzyme that can clip glucose monomers from cellulose (fiber), which makes the glucose in this polymer inaccessible.

Humans generate much more heat than alligators. Predict what this is due to: A) a greater number of energy transformations per minute in humans. B) a higher percentage of energy loss per transformation in humans. C) Both A and B

C) Both A and B

Predict the energy content of sugar: A sugar should have ____________ energy content compared to a fatty acid with the same number of C atoms. A) a similar B) about twice the C) about half the D) about one quarter the

C) about half the

Hemoglobin _____ O2 in the lungs and _____ O2 in the muscle; the binding capacity of hemoglobin for O2 is ____ in the lungs and _____ in the muscle region. A) binds; releases; low; low B) releases; binds; high; low C) binds; releases; high; low D) binds; releases; low; high

C) binds; releases; high; low

Deduce which of the following does NOT represent a state of high energy. A) electrons loaded onto NADPH B) the H+ gradient across the thylakoid membrane C) electrons in the water molecule D) the ATP formed E) electrons excited by sunlight

C) electrons in the water molecule

Deduce which took place in the ABSENCE OF molecular oxygen (O2) or ozone (O3). A) evolution of organisms from the ocean to the terrestrial (land) habitat B) evolution of multi-cellular organisms C) evolution of prokaryotes that use fermentation D) evolution of ATP formation in mitochondria E) evolution of plants and animals

C) evolution of prokaryotes that use fermentation

Deduce what force drives the build-up across the photosynthetic membrane of the proton (H+) gradient that subsequently serves to drive ATP formation. A) an ATP-fueled proton pump B) water C) light-driven electron transport D) ATP E) an ATP-fueled electron pump

C) light-driven electron transport

Deduce what type of transport is involved. How does the movement of protons through the ATP synthase occur? Via A) simple diffusion B) active transport C) passive transport

C) passive transport

Compare ATP formation by the photosynthetic electron transport chain to the operation of a hydroelectric dam. Fill in the blanks: Water stands for ________, the turbine stands for ________, and the lit-up light bulb stands for _________. A) the ATP synthase, the protons (H+), the ATP produced B) the protons (H+), the ATP produced, the ATP synthase C) the protons (H+), the ATP synthase, the ATP produced D) the ATP produced, the protons (H+), the ATP synthase

C) the protons (H+), the ATP synthase, the ATP produced

Predict where the "used-up" ADP and P go after ATP fuels the Na+/K+ pump at the cell membrane in an animal cell. A) ADP and P accumulate in the cytosol and don't form ATP again. B) ADP and P are regenerated to ATP by the Na+/K+ pump running in reverse. C) ADP and P are regenerated to ATP in the chloroplasts. D) ADP and P are regenerated to ATP in the mitochondria. E) C and D

D) ADP and P are regenerated to ATP in the mitochondria.

Draw conclusions about lactose intolerance. Choose the best answer. A) Lactose tolerance is the original human condition for adults from the time of hunter-gatherers. B) Lactose intolerance is the original human condition for adults from the time of hunter-gatherers. C) In ancient human populations that raised dairy cows, adults who were lactose intolerant had a lesser chance of survival and reproduction. D) B and C E) A and C

D) B and C

Predict the formula for a disaccharide made from two hexoses. A) C2H4O2 B) C6H12O6 C) C12H24O12 D) C12H22O11 E) C12H20O10

D) C12H22O11 Deduce answer by combining pieces you already know. Hexose has 6 carbons Carbohydrates (simple sugars) have general formula of H-C-OH or (CH2O)n C6H12O6 for a hexose When two hexoses are connected, one H2O molecule comes out: C6H12O6 + C6H12O6 = [C12H24O12 - H2O] = C12H22O11

Four of the statements below are false. Deduce which one is TRUE. A) C3 plants are able to fix CO2 with their stomates (leaf pores) less widely open than C4 plants. B) C3 plants are more productive in dry climates than C4 plants. C) C4 plants need more water than C3 plants. D) C4 plants need more energy (sunlight) to make sugars than C3 plants. E) C3 plants operate two CO2 fixation cycles.

D) C4 plants need more energy (sunlight) to make sugars than C3 plants.

Sunlight energizes electrons that pass into an electron transport chain where they give up some of their energy. The energy lost by the electrons is used to move ______ from low to high concentration. The electrons receive a second boost from sunlight and are transferred to ______ at the end of the photosynthetic electron transport chain. A) H2O; ATP B) NADP+; H+ C) ADP; NADPH D) H+; NADP+ E) H+; ATP

D) H+; NADP+ Narration: The energy lost by high-energy electrons flowing down the electron transport chain is used to move protons from low concentration in the stroma to high concentration in the inner thylakoid space. (Electrons coming out of the water-splitting photosystem are first transferred to an electron carrier that picks up protons on the stroma side and are then transferred to the next electron carrier that only carries electrons without protons and is bound on the inner side of the thylakoid membrane. It is on that side of the membrane that the no-longer-needed protons are dumped and piled up like water behind a dam.) The electrons receive a second boost from sunlight in the NADPH-producing photosystem that transfers electrons to NADP+.

A cell that contains enzymes, DNA, ribosomes, a cell membrane, and mitochondria could be a cell from A) a bacterium. B) an animal, but not a plant. C) a plant, but not an animal. D) a plant or an animal. E) any kind of organism.

D) a plant or an animal.

Cells release the energy of energy-rich food molecules. Deduce which of the steps below represent(s) a change from one form of energy to another? A) use of energy-rich electrons to build up a proton gradient B) use of the proton gradient to drive ATP formation C) use of an uncoupling protein to generate heat D) all of the above E) only A and B

D) all of the above

Ethanol is produced as a biofuel by fermentation of monosaccharides. Deduce which of the plant sources below is DIFFICULT to break down into monosaccharides. A) sucrose from sugarcane B) starch from corn C) starch from grasses D) cellulose from grasses E) sucrose from C4 plants

D) cellulose from grasses

Comparing the photosynthetic light reactions with the Calvin cycle, which of the two processes PRODUCE(S) NADPH? A) extraction of electrons from sugars B) only the Calvin cycle C) both the light reactions and the Calvin cycle D) only electron transport in the light reactions E) neither the light reactions nor the Calvin cycle

D) only electron transport in the light reactions Narration: The electrons dropped onto the NADPH shuttle come out of the photosynthetic electron transport chain (the light reactions). The Calvin cycle uses up NADPH and PRODUCES NADP+; sugars are formed in the Calvin cycle by forming C-H bonds with electrons provided by NADPH that is thereby consumed, and not produced, in the Calvin cycle. Extraction of electrons from sugars occurs in the cytosol (glycolysis) and in the mitochondria (citric acid cycle) as part of cellular respiration; protons and high-energy electrons are transferred from sugars to the H shuttle NAD+.

Glucose made in photosynthesis can be used by a plant in any of the following processes EXCEPT: A) to fuel the plant's cellular respiration. B) synthesis of sucrose. C) cellulose synthesis. D) synthesis of glycogen as an energy store. E) synthesis of starch as an energy store.

D) synthesis of glycogen as an energy store. Narration: Cellulose and starch are both made of glucose monomers; both polysaccharides are synthesized in leaves from glucose made in photosynthesis. Glucose made in photosynthesis is burned in plant's mitochondria to make ATP for cellular work. Sucrose (made from 1 glucose + 1 fructose) is used to transport sugars from leaves to other parts of the plant. Plants do not make glycogen. Glycogen (another polysaccharide made of glucose) is synthesized in the human liver as a means for storing sugar.

H2O is converted to O2 by __________, while O2 is converted to H2O by ___________. A) the thylakoid membranes; the Calvin cycle B) the inner mitochondrial membranes; the thylakoid membranes C) the mitochondrion; the chloroplast D) the thylakoid membranes; the inner mitochondrial membranes E) the Calvin cycle; the citric acid cycle

D) the thylakoid membranes; the inner mitochondrial membranes Narration: The chloroplast's water-splitting photosystem bound to the thylakoid membranes extracts electrons from H2O for photosynthetic electron transport and forms oxygen (O2) as a byproduct. The mitochondrion uses oxygen (O2) as its terminal acceptor for the electrons passing through the mitochondrial electron transport chain in the inner mitochondrial membranes, combining this oxygen with electrons and protons to form water.

Cells use the energy of energy-rich food molecules to form ATP. Deduce which of the following does NOT represent a state of high energy. A) the C-H bonds in food molecules B) the H (electrons + H+) in NADH C) the H+ gradient across the mitochondrial membrane D) the water formed E) the ATP formed

D) the water formed

All EXCEPT which of the processes below DIRECTLY involves electrons? These electrons are either dropped into the mitochondrial electron transport chain, picked up from this chain, or enable the process while passing through the chain. A) formation of water from O2. B) movement of protons from the matrix across the inner mitochondrial membrane. C) movement of protons into the intermembrane space. D) turning of the ATP synthase to generate ATP (from ADP and phosphate). E) regeneration of NAD+ from NADH.

D) turning of the ATP synthase to generate ATP (from ADP and phosphate). Narration: Movement of protons from low concentration in the matrix to high concentration in the intermembrane space across the inner membrane is fueled directly by electrons flowing through the mitochondrial electron transport chain step-by-step. The electrons that combine with oxygen to form water at the end of the electron transport chain come directly out of this chain. NADH is reconverted to NAD+ when it drops its electrons into the mitochondrial electron transport chain, causing the electrons to flow through the electron transport chain. It is not the electrons that directly turn the ATP synthase turbine, but rather protons flowing back downhill through the turbine from the intermembrane space to the matrix.

Predict features of C3 and C4 plants resulting from the fact that (i) C4 plants operate two CO2-fixing cycles instead of only one like C3 plants and that (ii) C4 plants are able to fix CO2 at much lower concentrations than C3 plants. A) C4 plants do not need to open their leaf pores as widely as C3 plants to do photosynthesis. B) C4 plants lose less water than C3 plants through their leaf pores. C) C4 plants need more energy from sunlight than C3 plants D) A and B E) A, B, and C

E) A, B, and C

Predict the effect of cyanide or carbon monoxide: A) No ATP is produced by the ATP synthase. B) Electron transport stops. C) The citric acid cycle stops. D) A and B E) A, B, and C

E) A, B, and C

Predict the effect of the uncoupling protein: A) No ATP is produced by the ATP synthase. B) Glycolysis and the citric acid cycle continue to run. C) Electron transport continues to run and the energy of high-energy electrons is released as heat. D) A and C E) A, B, and C

E) A, B, and C

The immediate next energy-rich state formed with the help of energy given up by electrons flowing through the mitochondrial electron transport chain is: A) ATP B) glucose C) NADH D) H2O E) a proton gradient

E) a proton gradient Narration: Electrons flowing through the mitochondrial electron transport chain step-by-step fuel the movement of protons into the mitochondrion's intermembrane space, where protons pile up like water behind a dam (just as is the case in the inner thylakoid space in chloroplasts that are absorbing light). Therefore, the immediate next energy-rich state to which energy lost by electrons flowing through the chain is converted is a proton gradient. ATP is only the next step following after that. Mitochondria do not form glucose. Water does not represent an energy-rich state; water formation in mitochondria does not require energy input; the electrons that combine with oxygen to form water have already lost all their energy. The energy for NADH formation in mitochondria is provided by transfer of high-energy electrons to NAD+ from remainders of glucose molecules in the citric acid cycle. NADH is the source of the energized electrons that enter the mitochondrial electron transport chain.