bio exam 3
Cellular respiration and photosynthesis are similar in that both involve _____.
oxidation-reduction (redox) reactions Both cellular respiration and photosynthesis involve a series of oxidation-reduction events.
In cellular respiration, most ATP molecules are produced by _____.
oxidative phosphorylation
Some human cells, such as nerve cells, are restricted to aerobic respiration to recycle NADH and FADH2. If these cells are deprived of oxygen, then __________.
oxidative phosphorylation would come to a halt because there wouldn't be any oxygen to serve as an electron acceptor at the transport chain Without oxygen with its high electronegativity waiting at the end of the electron transport chain, electron flow would cease, along with the action of the protein complexes that create the proton gradients.
The light reactions produce _____.
oxygen, NADPH, and ATP
In which of the following organelles does photosynthesis take place?
chloroplast Chloroplasts use energy from light to transform carbon dioxide and water into sugar and oxygen
In the Calvin cycle, how many ATP molecules are required to regenerate RuBP from five G3P molecules?
3
Which of the following equations represents photosynthesis?
6CO2 + 6H2O → C6H12O6 + 6O2 Photosynthesis requires carbon dioxide and water for the production of sugar and oxygen.
inputs of photosynthesis
6H2O, 6CO2, (light) energy
The O2 required for __________ is supplied by __________.
Breathing supplies the O2 required for cellular respiration and also removes the CO2 as a waste product of cellular respiration.
In glycolysis there is a net gain of _____ ATP.
It takes 2 ATP to produce 4 ATP.
Which of the following is NOT an aspect of global climate change?
net growth of polar ice caps Quite the opposite is happening as a component of climate change: Polar ice caps are shrinking.
Carbon dioxide enters a leaf through the _____.
stomata These are the openings in the epidermis of leaves through which gas exchange takes place
The photosynthetic event known as the Calvin cycle occurs in the
stroma The thylakoids of the chloroplast are the sites of the light reactions, whereas the Calvin cycle occurs in the stroma.
How many NADH are produced by glycolysis?
2
In preparing pyruvate to enter the citric acid cycle, which of the following steps occurs?
A compound called coenzyme A binds to a two-carbon fragment derived from pyruvate.
In the citric acid cycle (also called the Krebs cycle), ATP molecules are produced by _____
A phosphate group is transferred from GTP to ADP.
In glycolysis, ATP molecules are produced by _____.
A phosphate group is transferred from glyceraldehyde phosphate to ADP.
What two molecules are produced by the light reactions and used to power the Calvin cycle?
ATP and NADPH ATP and NADPH are both products of the light reactions and are used to power the Calvin cycle.
Which of these enters the citric acid cycle (also called the Krebs cycle)?
Acetyl CoA is a reactant in the citric acid cycle (also called the Krebs cycle).
In what organelle would you find acetyl CoA formation, the citric acid cycle, and the electron transport chain?
All of the steps of cellular respiration except glycolysis take place in the mitochondrion.
What is the correct general equation for cellular respiration?
C6H12O6 + 6 O2 → 6 CO2 + 6 H2O + ATP energy
Which of these is NOT a product of glycolysis?
FADH2 is a product of the citric acid cycle.
For each glucose that enters glycolysis, _____ NADH enter the electron transport chain.
For each glucose molecule that enters glycolosis, a total of 10 NADH are produced -- 2 are produced in glycolysis, 2 are produced in acetyl CoA production, and 6 are produced in the citric acid cycle.
Given the relatively modest number of calories burned by anything but the most vigorous of activities, how can people consume over 2,000 kilocalories a day yet maintain a healthy body weight
Most of the energy consumed in food is spent maintaining the body's functions over the course of a day, so a healthy amount of daily exercise would require only a modest increase in the number of kilocalories consumed to maintain a healthy weight. This is true, and it's lucky for dieters. If we had to burn 2,000 kilocalories a day in exercise, we'd need to run nearly a marathon every day.
Oxidative phosphorylation is responsible for nearly all the ATP produced in your body.
NADH and FADH2 deliver electrons to the electron transport chain during oxidative phosphorylation. Chemiosmosis is the final step in oxidative phosphorylation. Without oxygen, oxidative phosphorylation would not occur.
What transports electrons from the light reactions to the Calvin cycle?
NADPH NADPH is an electron carrier that picks up electrons in the light reactions and releases them in the Calvin cycle.
Aliyah is studying cells as they proceed through redox reactions. If she could measure the number of electrons in the cells' organic fuel and the number of NADH molecules, how would they change as redox reactions proceed? Would she expect the organic fuel to gain or lose electrons? Would she expect there to be more or fewer NADH molecules?
Organic fuel loses electrons; more NADH molecules
The final electron acceptor of cellular respiration is _____.
Oxygen is combined with electrons and hydrogen to form water.
One of the important waste products of photosynthesis is oxygen gas. Where does this oxygen gas come from?
Oxygen is released when water is broken down to extract electrons and protons for use in the light reactions.
Current evidence indicates that the process of photosynthesis arose more than three billion years ago. Its origin had a huge impact on existing organisms and on the physical characteristics of the biosphere. Which major physical change could be attributed to photosynthesis?
Photosynthesis drastically increased the oxygen content of the atmosphere. Almost all molecular oxygen (O2) in Earth's atmosphere has been produced by the splitting of water via photosynthesis. Prior to the production of atmospheric oxygen, oxidative phosphorylation would not have occurred
Because of the abundance of water on planet Earth, hydrogen gas (H2) is a candidate in the search for a replacement for petroleum. However, removing hydrogen from water requires the investment of a great deal of energy. Why are plants considered to be one step ahead in the utilization of hydrogen as an alternative fuel source?
Plant cells possess water-splitting enzymes. Plant cells contain an enzyme that splits water, producing two electrons, two hydrogen ions, and one oxygen atom (1/2 O2), by lowering the activation energy. This is a more efficient process and requires much less energy than mechanically splitting H2O.
Carbon fixation involves the addition of carbon dioxide to _____.
RuBP In the Calvin cycle, carbon dioxide is added to RuBP.
Select the correct sequence of steps as energy is extracted from glucose during cellular respiration.
Select the correct sequence of steps as energy is extracted from glucose during cellular respiration.
In glycolysis, what starts the process of glucose breakdown?
Some ATP energy is used to start the process of glucose oxidation.
Imagine an organism with mutations in complexes I, III, and IV that prevent pumping of hydrogen ions into the intermembrane space but still allow electrons to pass through the electron transport chain. Which of the following is the most likely consequence of these mutations
The accumulation of hydrogen ions in the intermembrane space creates a concentration gradient across the inner mitochondrial membrane, storing potential energy. This hydrogen ion gradient causes hydrogen ions to flow down their concentration gradient through ATP synthase, powering the phosphorylation of ADP to ATP. Without the gradient, ATP synthase would not function and ATP would not be made.
During electron transport, energy from _____ is used to pump hydrogen ions into the _____.
The energy released as electrons, which have been donated by NADH and FADH2, is passed along the electron transport chain and used to pump hydrogen ions into the intermembrane space.
During photosynthesis, the light reactions convert light energy to chemical energy. Select the three true statements about the light reactions of photosynthesis.
The light reactions produce chemical energy in the form of NADPH and ATP. The light reactions take place inside the thylakoids of chloroplasts. Pigment molecules inside photosystem II and photosystem I absorb light energy from the sun.
Which statement describes the citric acid cycle?
This process produces some ATP and carbon dioxide in the mitochondrion.
Which statement describes glycolysis?
This process splits glucose in half and produces 2 ATPs for each glucose
Which of these is NOT a product of the citric acid cycle (also called the Krebs cycle)?
acetyl CoA
Considering the wavelengths of light shown below, the pigments in the granum absorb mainly in which range?
blue-violet and red-orange These are the wavelengths of light that plant pigments absorb.
Which of the following are photoautotrophs?
corn stalks just before harvest Corn plants are photoautotrophs. They produce organic molecules from inorganic molecules using the energy of light.
outputs of photosynthesis
glucose and 6 oxygen molecules
The thylakoid membranes bring together the components necessary to carry out the _____.
light reactions
A muscle cell deprived of molecular oxygen will convert glucose to lactic acid to __________.
recycle NADH through fermentation During lactic acid fermentation, pyruvate is reduced directly by NADH to form lactate. This recycles NAD+, so ATP production during glycolysis can continue.
Most NADH molecules generated during cellular respiration are produced during __________.
the citric acid cycle
When chloroplast pigments absorb light, _____.
their electrons are raised from a ground state to an excited state The absorbed energy moves the electrons to a more energetic orbital.
Fat is the most efficient molecule for long-term energy storage, even compared to carbohydrates, because __________.
with their numerous hydrogen atoms, fats provide an abundant source of high-energy electrons Because oxidative phosphorylation depends on a source of electrons (all of which are extracted from hydrogen-carbon bonds), fats, which contain primarily hydrogen and carbon atoms, are an abundant source of high-energy electrons that can be harvested for energy production.
What connects the two photosystems in the light reactions?
An electron transport chain An electron transport chain connects the two photosystems in the light reactions.
How many carbon dioxide molecules must be added to RuBP to make a single molecule of glucose?
6 Six carbon dioxide molecules are required to produce two G3P molecules, which can be combined to make one glucose molecule.
Which option properly summarizes the inputs and outputs of the Calvin cycle?
ATP + NADPH + 3CO 2 →→ G3P
What occurs as electrons pass through the multiple carrier molecules of the electron transport chain?
Energy is released in a stepwise fashion As electrons pass through the carrier molecules of the electron transport chain, energy is released. You can think of the electrons as balls that are bouncing down staircase steps as they move between carrier proteins, which are located in the inner membrane of a mitochondrion. The small amount of energy released at each step during this process is captured and used to synthesize ATP.
Which of the following statements regarding glycolysis is FALSE?
Glycolysis evolved in an oxygen-rich environment. Correct, this is the FALSE statement. Glycolysis does not require O2, and likely evolved nearly a billion years before oxygen began accumulating from photosynthesis.
Which of the following processes takes place in the cytosol of a eukaryotic cell?
Glycolysis, the breakdown of glucose into two molecules of pyruvic acid, takes place in the cytosol, outside the mitochondria.
What provides electrons for the light reactions?
H2O Electrons are stripped from water in the light reactions of photosynthesis. This is one of the reasons plants need water.
Place the following events of the electron transport chain in order. Rank the items from the event that occurs first to the event that occurs last.
In the electron transport chain, electrons move between several molecules. First, electrons on NADH are released as NADH becomes oxidized to NAD+. These electrons then enter the electron transport chain, where they are passed to carrier proteins. As they move stepwise between carrier proteins, energy is released. This energy will later be used by the mitochondrion to synthesize ATP. At the end of the electron transport chain, when electrons are released, they are next accepted by oxygen. The newly reduced oxygen also picks up two protons, forming a water molecule.
Which statement describes the electron transport chain?
In the electron transport chain, electrons move from one electron carrier to another, eventually reaching oxygen. The released energy is used to make ATPs.
In the absence of oxygen, cells need a way to regenerate which compound?
NAD+ The NAD+ needs to be regenerated, which is why pyruvate is converted to ethanol or lactic acid.
After 3-PGA is phosphorylated, it receives energized electrons from _____.
NADH NADPH supplies the electrons that reduce the phosphorylated 3-PGA
What molecule releases the electrons used in the electron transport chain?
NADH As NADH becomes oxidized to NAD+, it releases electrons into the electron transport chain. These electrons then pass through various carrier molecules of the electron transport chain, which are embedded in the inner membrane of a mitochondrion.
Although the reactions of the Calvin cycle are not directly dependent on light, they usually do not occur at night. Why?
The Calvin cycle depends on products of the light reactions. The ATP and NADPH produced during the light reactions are necessary to provide energy and high-energy electrons for the Calvin cycle.
Why is the citric acid cycle called a cycle?
The two-carbon acetyl group is transferred to the citric acid cycle utilizing Coenzyme A (CoA) where it binds to oxaloacetate, thereby regenerating citrate in cyclical fashion. The cycling referred to is that of the regeneration of the four-carbon compound, oxaloacetate at the end of the cycle, which then combines with the two-carbon acetyl group from acetyl CoA to regenerate citrate, completing one turn of the cycle.
In muscle cells, fermentation produces _____.
These are the products of fermentation as it occurs in muscle cells
Using the ATP generated during cellular respiration, the intermediates of glycolysis and the citric acid cycle, such as pyruvate and acetyl CoA, can be siphoned off and used to __________.
build amino acids, fats, and sugars The beauty of many metabolic pathways is that they can be used for both the breaking down of compounds for energy, or to synthesize complex macromolecules, depending on the needs of the cell and the availability of energy.
The most important role of pigments in photosynthesis is to _____.
capture light energy The wavelengths most effectively absorbed by pigments are those most useful as energy for the light reactions.
What provides the carbon atoms that are incorporated into sugar molecules in the Calvin cycle?
carbon dioxide Carbon dioxide provides the carbon atoms that are incorporated into sugars in photosynthesis. This is why plants need to take in carbon dioxide.
The electron transport chain is, in essence, a series of redox reactions that comprise the last stage of aerobic cellular respiration. During these redox reactions, __________.
electrons are transferred through a series of electron acceptors embedded within the inner mitochondrial membrane NADH provides these electrons to the membrane-embedded electron acceptors.
The conversion of NADP+ to NADPH occurs with the assistance of __________.
electrons from water and energy from sunlight Water is split to provide the electrons and a hydrogen ion to reduce NADP+ to NADPH. Light energy is required to drive the transfer of the electrons to NADP+.
Photosynthesis is an __________ process in which carbon is __________, whereas cellular respiration is an __________ process in which carbon is __________.
endergonic : reduced : exergonic : oxidized Photosynthesis is an endergonic process in which electrons from water are transferred to carbon dioxide, reducing it while forming sugar. During the exergonic process of respiration, energy is released from sugar when the sugar is oxidized.
The primary function of light absorption by photosystems I and II is to produce __________.
energized electrons These energized electrons power the photosynthetic electron transport chain to generate ATP, and ultimately be transferred to NADP+ to make NADPH for use in the Calvin cycle
Incoming photons of light energy initiate photosynthesis by _____.
exciting electrons in pigment molecules within the photosystems, raising them to a higher energy level
A chemist has discovered a drug that blocks phosphoglucoisomerase, an enzyme that catalyzes the second reaction in glycolysis. He wants to use the drug to treat people with bacterial infections. However, he can't do this because __________.
human cells also perform glycolysis; the drug might also poison them The chemist's drug would have a devastating effect on human cells' ability to process glucose.
During the first step of a redox reaction, what does the enzyme dehydrogenase strip from organic fuel?
hydrogen atoms
The proximate (immediate) source of energy for oxidative phosphorylation is _____.
kinetic energy that is released as hydrogen ions diffuse down their concentration gradient
The "photo-" part of the word photosynthesis refers to the __________, whereas "-synthesis" refers to __________.
light reactions that occur in the thylakoids; carbon fixation Events in the thylakoids are termed the "light reactions," and "carbon fixation" refers to the incorporation of carbon into organic molecules.
The light reactions' production of oxygen during photosynthesis is important for life on Earth. Which of the following would prevent oxygen from being made?
the inability of water to donate its electrons to photosystem II When light energy strikes the reaction center complex of photosystem II, an electron from a pair of chlorophyll a molecules is boosted to a higher energy state. To replace the captured electron, a water molecule is split and donates its electrons to photosystem II. After the water molecule split, the remaining oxygen atom is released into the thylakoid space where it combines with another oxygen atom into oxygen gas, supplying the atmosphere with the oxygen we breathe.
The light reactions take place in the _________ and the Calvin cycle takes place in the _________.
thylakoids; stroma Within the chloroplast, the light reactions take place in the flattened sacs called thylakoids and the Calvin cycle takes place in the thick fluid called the stroma.
