| What're 2 important things about NAD+? | -Positively charged coenzyme
-High energy electron carrier (oxidized form) |
| What is ATP made of? | Sugar ribose, 3 phosphate groups and a nucleotide base (adenine) |
| What is ATP? | A universal energy currency - large amount of free energy that a lot of life forms use |
| Where is energy stored in ATP? | In the phosphate bonds |
| What happens during ATP hydrolysis? | ATP breaks down to produce ADP, a phosphate group and a large amount of energy |
| What is the difference between ATP and ADP? | ATP: 3 Phosphates
ADP: 2 Phosphates |
| What is ATP synthesis? | Combining of ADP with phosphate (required energy) |
| What are ATP and ADP forms of? | ATP and ADP are forms of RNA |
| What are the 2 ways ATP is formed? | -Substrate level phosphorylation
-Oxidation Phosphorylation |
| What is substrate level phosphorylation? | Formation of ATP by a direction transfer of a phosphate group (from a substance) to ADP
-> Enzyme catalyzed |
| What is oxidation phosphorylation? | Formation of ATP using energy transferred indirectly from a series of redox reactions
-> Involves final electron accepter (Oxygen - electronegative) |
| What're molecules with lots of C-H bonds high in? | High in energy |
| When is potential energy stored in food molecules released? | Released during oxidation reactions |
| What is oxidation? | Loss of electrons (removal of H, addition of O) |
| What is reduction? | Gain of electrons (removal of O, addition of H) |
| What happens to the energy released during oxidation reactions? | Energy released is transferred to energy carrying molecules |
| What are the two energy carriers? | -NAD+
-NADH |
| What're 2 important things about NAD+? | -Positively charged coenzyme
-High energy electron carrier (oxidized form) |
| What're 2 important things about NADH? | -Reduced form of NAD+
-Carries potential energy to drive ATP synthesis |
| What respiration do both plants and animals use? | Aerobic cellular respiration to extract energy from food when oxygen is persent |
| What is aerobic cellular respiration? | Process that uses oxygen to harvest energy from organic compounds |
| What is the aerobic cellular respiration formula? | : |
| How does the oxidation of glucose occur ? | The oxidation occurs through a series of enzyme catalyzed reactions |
| Where does aerobic cellular respiration occur? | Occurs in the cytoplasm and mitochondria of cells |
| What generates the most amount of ATP used in eukaryotes? | Mitochondria generates most of the ATP in Eukaryotes |
| What're two ways to extract energy from food in absence of oxygen? | -Anaerobic respiration
-Fermentation |
| What does anaerobic respiration to do produce ATP? | Uses an inorganic substance other than oxygen as the final oxidizing agent to produce ATP |
| What does fermentation do in order to produce ATP? | Uses an organic compound as the final oxidizing agent to produce ATP |
| What are two types of fermentation? | Alcohol fermentation and lactate fermentation |
| Provide an example of a use of ATP energy for each
of the following tasks:
(a) chemical work
(b) mechanical work
(c) transport work | a) An example of chemical work using ATP is supplying energy for non spontaneous, endergonic reactions, including protein synthesis and DNA replication.
b) An example of mechanical work using ATP energy is the beating of cilia or movement of flagella, contraction of muscle fibres, or movement of chromosomes during mitosis/meiosis.
c) An example of transport work using ATP energy is pumping substances such as Na+ or K+ ions across membranes against their concentration gradient. |
| What does the universality of ATP in all living species suggest about the relationship of species to one another? | The universality of ATP as an energy source for every type of cell in every living organism supports an argument that all species have evolved from one original organism. |
| (a) Describe the structure of an ATP molecule.
(b) How does the structure of the ATP molecule
relate to the large amounts of free energy it
contains? | a) ATP can be described as a phosphorylated sugar. It has a triphosphate group attached to a ribose sugar molecule, which is attached to a molecule of adenosine.
b) Structure of ATP molecule permits it to contain large amounts of free energy; the unique feature that permits this is the triphosphate tail where several high energy bonds are located. These bonds can be recycled through cellular machinery. |
| Describe the process of ATP hydrolysis. | ATP hydrolysis is the process by which ADP and Pi (phosphate) are formed and water is consumed. The process releases free energy. |
| During the hydrolysis of ATP, energy is released, but most of the molecule, the ADP portion, remains intact. How does this compare to what happens to a molecule of glucose when it is used as an energy source? | During the hydrolysis of ATP the ADP is retained and recycled. This is in contrast to the oxidation of glucose, in which the entire molecule is catabolized. When a cell uses glucose during cellular respiration the entire molecule is oxidized and converted into water and carbon dioxide. |
| Why is it necessary for cells to “recycle” ADP and Pi rather than just release them as waste products? | There is very little ATP in the diet and it is a relatively large and energy-rich molecule. It would be extremely wasteful and inefficient to use an “entire ATP” and discard it just to obtain the energy released by a single hydrolysis reaction. |
| Explain, in your own words, why both gasoline and glucose make good fuels. | Both gasoline and glucose make good fuels. Chemically both compounds contain a very high percentage of high-energy C–H bonds. When these molecules react with oxygen, their high-energy valence electrons form strong bonds with the very electronegative oxygen atoms, causing the release of energy. In cars, liquid fuel is advantageous as it is easy to transport. In organisms, a solid power that can be dissolved within the body is beneficial as it allows for easy storage and transport throughout the body and easy absorption from food sources. |
| (a) Write the chemical equation for the complete combustion of glucose.
(b) Which is the oxidizing agent?
(c) Which is the reducing agent? | (a) C6 H12 O6 + 6 O2 -> 6 CO2 + 6 H2O
(b) Oxygen is the oxidizing agent.
(c) Glucose is the reducing agent. |
| Use diagrams to explain how the relative positions of electrons change during a redox reaction, and how these positions are related to energy changes during the reaction. | x |
| Explain the gaining and releasing of energy by electrons, as related to changes in position relative to one or more atomic nuclei. | For any atom, an electron that is farther from the nucleus contains more potential energy than an electron that is more closely held by the nucleus. At the same time, an electron has more potential energy relative to a large nucleus than it would have relative to a small nucleus. As a result, an electron releases energy if it moves closer to a large nucleus and must absorb energy to be pulled away. |
| List two examples of slow oxidation events and two
examples of rapid oxidation events. | Two examples of slow oxidation events are the formation
of patina on copper roofs and the rotting of fruits. Two examples of rapid oxidation are the burning of gasoline and the light given off from a road flare. |
| How is it beneficial for organisms to use controlled oxidation rather than rapid combustion to release energy from their food? Provide at least two benefits. | Controlled oxidation is a benefit to an organism because less energy is lost or wasted as thermal energy during controlled oxidation than would be lost during rapid oxidation. In addition, the cell could suffer damage from the high temperatures required, and created, by rapid combustion. |
| What happens during cellular respiration? | Nutrients like glucose are oxidized to provide the cell with useful energy. |
| How many stages are there in cellular respiration? | 3 distinct stages |
| What are the 3 distinct stages of cellular respiration? | -Glycolysis (in cytoplasm and anaerobic)
-Citric acid cycle (also known as Kreb's cycle: found in matrix/fluid of mitochondria and is aerobic)
-Electron transport chain (ETC) (Found in inner membrane of mitochondria [cristae] and is aerobic) |
| Stage 1 of Glycolysis | -Start with Glucose (0 ATP, 0 NADH)
-ATP phosphorylates glucose to G6P
-Phosphate attaches
-Becomes G6P |
| Stage 2 of Glycolysis | -Glucose 6 Phosphate (G6P) (-1 ATP, 0 NADH)
-Rearranged into fructose 6 phosphate
-G6P rearranged into F6P |
| Stage 3 of Glycolysis | -Fructose 6 phosphate (F6P) (-1 ATP 0 NADH)
-ATP phosphorylates F6P to F1,6-BP
-Another phosphate added, activation energy still not met |
| Stages 4 & 5 of Glycolysis | -Fructose 1, 6-bisphosphate (F1, 6-BP) (-2 ATP, 0 NADH)
-Splitting (F1, 6-BP)
-F1, 6BP splits into 2 molecules of G3P
-New molecules are Glyceraldehyde 3-phosphate (G3P) |
| Stage 6 of Glycolysis | - 1-3Bisphosphorglycerate (BPG) (-2 ATP, 2 NADH)
- Two empty boxes are a NAD+ taking a hydrogen and becoming NADH
- Each G3P breaks down into BPG and in that process we build a molecule of NADH (Energy carrier) and there are 2 NADH (since it split earlier) |
| Stage 7 of Glycolysis | - 3-Phosphohlycerate (3PG) (0 ATP, 2 NADH)
-The arrows are meant to be the other way, so ADP comes and explodes into ATP
-BPG oxidized and phosphate breaks off and attaches to an ADP (ATP after attachment), 2 ATP made (b/c there are 2 molecules)
-Each BPG breaks down into 3PG whilst making ATP molecule |
| Stage 8 of Glycolysis | - 2-Phosphoglcerate (2PG) (0 ATP, 2 NADH)
- 3PG rearranges to form 2PG |
| Stage 9 of Glycolysis | -Phosphoenolpyruvate (PEP)
-Hydrogen and OG cleaved off, forms water and PEP
-Each 2PG are converted into a PEP by the removal of water |
| Stage 10 of Glycolysis | - Pyruvate (2 ATP and 2 NADH)
-The arrows are meant to be reversed, another ADP comes and becomes ATP
-Each PEP breaks down into a pyruvate while building a molecule of ATP |
| Where does the citric acid cycle (kreb's cycle) happen? | Happens in the matrix (fluid) of the mitochondria |
| Is the citric acid cycle aerobic or anaeorbic? | Aerobic |
| How does the citric acid cycle begin? | Begins when pyruvate is shuttled through the mitochondrial membranes and into the matrix |
| What must happen to pyruvate before it enters the matrix? | Must be oxidized |
| Please fill in the boxes and describe what is happening | Pyruvate is converted into acetyl-COA . Pyruvate oxidation ends. Pyruvate started with no ATP, NADH, or FAOH. Acetyl-COA ended up with no ATP, NADH, or FADH but did make a CO2. |
| Please fill in the boxes and describe what is happening Step 1 | Oxaloacetate has 2 ATP, 8 NADH, 2 FADH2, and 6 CO2. It is the first step in the citric acid cycle. |
| Step 2 | Acetyl group (from earlier) joins to oxalocetate to form citrate |
| Step 3 | Citrate is rearranged to form isocitrate |
| Step 4 | Isocitrate is converted to alpha ketoglutarate through oxidization. 0 ATP, 4 NADH, 0 FADH2, 4 CO2. |
| Step 5 | Alpha-ketoglutarate is converted to succinyl-COA. |
| Step 6 | Succinyl-COA loses coenzyme A to become succinate. A free-floating phosphate group is added to a GDP molecule to make GTP. GTP reverts to GDP and transfers the phosphate group to an ADP to produce an ATP molecule. |
| Step 7 | Succinate is converted to fumarate. Correction: Fumarate has 2 FADH2 |
| Step 8 | Fumarate is converted to malate |
| Step 9 | Malate is converted to oxaloacetate |
| (a) What is the final energy-rich product of the
pathways that extracts energy from food?
(b) What is this product responsible for in the
cell? | (a) The final energy-rich product of the pathways that extract energy from food is
ATP.
(b) ATP is responsible for providing energy to drive almost all metabolic activities within
the cell. |
| Explain the main difference between aerobic respiration and anaerobic respiration. | aerobic respiration uses oxygen as a final electron acceptor to produce ATP,
and anaerobic respiration uses an inorganic oxidizing agent other than oxygen. |
| Use a Venn diagram to compare and contrast anaerobic respiration with fermentation. | . |
| Describe the differences between the following:
• obligate aerobes
• obligate anaerobes
• facultative anaerobes | -obligate aerobes cannot survive without oxygen
-obligate anaerobes cannot survive in the presence of oxygen
-facultative anaerobes can live with or without oxygen. |
| (a) What is the overall equation that represents aerobic cellular respiration?
(b) Describe this equation using simple words that a non-scientist could understand. | (a) (b)Glucose, or sugar, reacts with oxygen to produce carbon dioxide, water, and energy stored in molecules called ATP. |
| How many stages are involved in aerobic cellular respiration? Briefly describe each stage. | Aerobic cellular respiration consists of four main stages:
-glycolysis, pyruvate oxidation, the citric acid cycle, and electron transport.
-In glycolysis, glucose is broken down into pyruvate, producing some ATP and NADH.
-Pyruvate oxidation converts pyruvate into carbon dioxide, acetyl molecules, and NADH.
-The citric acid cycle fully oxidizes acetyl molecules to CO2, generating more ATP, FADH2, and NADH.
-In electron transport, NADH and FADH2 from the previous stages are used to produce ATP through an electron transport system. |
| Some bacteria cells are quite similar in structure to mitochondria. Both contain their own DNA, and
both are able to divide on their own (mitochondria divide within eukaryotic cells). However, bacteria
cells are able to survive independently, while mitochondria are not.
(a) What part of the aerobic respiration pathway cannot be performed by mitochondria?
(b) In terms of energy pathways only, what two chemicals (in addition to ADP and Pi) do mitochondria need to take in to generate ATP? | (a) The part of the aerobic respiration pathway that cannot be performed by mitochondria is glycolysis.
(b) Mitochondria need to take in pyruvate and oxygen in order to generate ATP. |
| Glycolysis, pyruvate oxidation, and the citric acid cycle produce only a small amount of ATP from
the energy in a glucose molecule. In what form(s) is (are) the rest of the harvestable energy that is
converted to ATP in the electron transport chain and chemiosmosis? | NADH, FADH2, ADP, and Pi |
| Where does the electron transport chain (ETC) occur? | Occurs in the inner membrane of mitochondria (cristae) |
| What series does the ETC process involve? | Involves a series of membrane proteins called cytochromes |
| What do NADH and FADH2 do when they interact with cytochromes?
Where is NADH and FADH2 made? | NADH and FADH2 (produced during CAC) give up H+ ions and electrons to cytochromes |
| What is transported through the chain of cytochromes? | Electrons |
| Where do H+ ions accumulate in ETC? | H+ ions accumulate in the intermembrane space b/c electrons are claustrophobic and spread out |
| What happens when there is a high concentration of H+ ions in the intermembrane space? | High concentration of H+ ions in the intermembrane space creates concentration gradient and electrostatic gradient |
| What do gradients do in the ETC? What is the motor ? | Drive H+ ions through a protein channel; providing energy to synthesize ATP.
Think of H+ as air or water and the channels as motors; the H+ ions (in high concentration) want to run through this motor to a less concentrated area; making ATP (energy), the motor is ATP synthase. |
| How does the Electron transfer chain work? What is the equation used for the production of water? | 1. Electrons released by NADH and FADH2 move through the ETC
2. Each cytochrome is alternately reduced and then oxidized
3. All happens until electrons combine with final electron accepter oxygen
4. Once electrons are accepted by the O2, H+ ions are also picked up, resulting in the formation of H20
5. 1/2 O2 + 2H+ -> H20 |
| Theoretically, how much NADH, FADH, and ATP is made in glycolysis, pyruvate oxidation, and kreb's cycle? | Glycolysis
-6 ATP (2 NADH * 3)
Pyruvate oxidation
- 6 ATP (2 NADH * 3)
Krebs's cycle
-18 ATP (6 NADH * 3)
-4 ATP (2 FADH * 2)
In total: 38 ATP per glucose |
| When muscles are overworked, what happens in ATP production? What toxic byproduct is made? | For glycolysis to continue, NAD+ must be replenished in animals, this occurs through lactic acid fermentation. Total production of 2 ATP per glucose molecule. Lactic acid is the toxic byproduct.
Glucose
-2 NADH and 2 ATP
2 Pyruvate
-2 NAD+
end result
- 2 Lactic acid |
| What is the other way to quickly make energy, which only happens in bacteria and yeast? | For glycolysis to continue, NAD + must be replenished. In bacteria and yeast, this occurs through alcohol fermentation, total production is 2 ATP per glucose.
Glucose
-2 NADH and 2 ATP
2 Pyruvate
-2 CO2
2 Acetaldehyde
-2 NAD+
End product
-2 ethanol |
| How does the electron transport chain produce ATP? What is the driving force? | 1. ETC transfers electrons from NADH and FADH2 to O2 through 4 complexes
-Each complex increases in electron affinity
2. 2 Electron shuttles help move electrons between complexes
3. O2 High affinity takes electrons from the cytochrome
4. Causing a sequence where electrons from more electronegative molecules move to less electronegative ones
-Drives the ETC |
| (a) Do the electrons in NADH have the most or the least free energy in the electron transport
chain?
(b) The electrons in NADH form bonds as they move through the electron transport chain.
Do these bond formations use or release energy? | (a) The electrons in NADH have the most free energy in the electron transport chain.
(b) These bond formations result in energy being released as the electrons form stronger and
stronger bonds as they move through the electron transport chain. |
| Which stages of aerobic cellular respiration occur in the mitochondria, and which stages do not? | The stage of aerobic cellular respiration that does not occur in the mitochondria is glycolysis. Glycolysis occurs in the cytosol. All of the other stages of aerobic respiration—pyruvate oxidation, the citric acid cycle, the electron transport chain, and chemiosmosis—occur in the mitochondria. |
| What is the primary function of the proton-motive force? | The primary function of the proton-motive force is the establishment of a chemical and concentration gradient of protons across the membrane.
This represents a source of energy that can be harnessed to do work.
Cells use the proton-motive force in the process called chemiosmosis, which synthesizes ATP. |
| Give an example of how uncoupling is used by organisms to increase survival. | An example of uncoupling is brown adipose fat. This fat can use uncoupling to generate thermal energy from the electron transport chain instead of generating ATP. Uncoupling produces energy to maintain body temperature in hibernating animals and in very young offspring, including human infants. |
| When does anaerobic respiration occur? | Occurs when oxygen is limited or absent
Some environments like that are the human gut, underground and oceans |
| What're 2 anaerobic processes? | Alcohol fermentation and Lactate fermentation |
| Which organisms carry out alcohol fermentation? | Bacteria and yeasts |
| What happens in alcohol fermentation? | Pyruvate (product of glycolysis) is decarboxylated to produce acetaldehyde
then used to oxidize NADH, regenerating NAD+. |
| What are the final products of alcohol fermentation? | CO2, ethanol, and NAD+. |
| When does lactate fermentation occur? | Occurs in muscle cells during intense physical activity when oxygen supply is insufficient to meet energy demands. |
| What happens in lactate fermentation? | Pyruvate is converted into lactate to regenerate NAD+ so that glycolysis can continue at a high rate. |
| What happens to lactate after a strenuous activity? | It's transported to the liver
where it is converted back to pyruvate
and enters the citric acid cycle and electron transport chain
when sufficient oxygen is available. |
| Which is more efficient, anaerobic (alcohol and lactate fermentation) or aerobic respiration? | Aerobic
Alcohol and lactate fermentation are much less efficient in terms of ATP production compared to aerobic respiration. |
| How much ATP do anaerobic pathways make? Why? | 2 ATP per glucose molecule due to the formation of ethanol or lactate, which are energy-rich compounds. |
| What can organisms use when glucose is scarce? | Proteins and fats |
| How can proteins and fats be broken down? (What do they become after breaking down)
Why is this important? | Proteins are broken down into amino acids, while fats are broken down into fatty acids and glycerol.
They're important breakdown products b/c they can be converted into intermediates that feed into glycolysis and the citric acid cycle. |
| Compare aerobic respiration and fermentation in terms of the amount of ATP that can be generated
from a single glucose molecule. | Aerobic respiration and fermentation can generate quite different numbers of molecules of
ATP from a single glucose molecule. Cells that rely on fermentation to generate ATP using only
glycolysis generate 2 ATP per molecule of glucose. Conversely aerobic respiration uses an
electron transport chain and produces approximately 36–38 ATP per molecule of glucose. |
| (a) What is the difference between fermentation and glycolysis?
(b) Why do cells rely on fermentation rather than glycolysis alone? | (a) The major difference between fermentation and glycolysis is that the fermentation pathway
includes additional reactions needed to regenerate the NAD+ that was reduced during glycolysis.
(b) If cells relied on glycolysis alone, they would quickly run out of NAD+, a necessary reactant in glycolysis. They rely on fermentation to regenerate the NAD+. |
| Do our muscle cells produce alcohol? Given that alcohol and lactate fermentation both yield two
ATP molecules for every glucose molecule, do you think it would make any difference which pathway
was used? Explain. | No, our muscle cells do not produce alcohol; instead they undergo lactate fermentation under
anaerobic conditions. Even though they produce the same number of ATP per molecule of
glucose, alcohol is toxic. Producing it in large amounts during strenuous exercise would cause
a variety of problems for the cell and for the organism as a whole. |
| What do chloroplasts do? What is their overall equation? | Convert light energy into glucose
6 Co2 + 12 H2O -> (light) C6H12O6 + 6O2 + 6H20 |
| What 2 stages does photosynthesis occur? | Light reactions and Calvin cycle
In light reactions, it's the thylakoid of the chloroplasts
In the Calvin cycle its the stroma of the chloroplasts |
| What do cross sections of leaves show? | Show that leaves have photosynthetic cells that contain chloroplasts |
| What do cross sections of chloroplasts show? | Show that chloroplasts have thylakoid membrane systems and stroma (surrounding fluid) |
| What do photosynthetic pigments do? | They capture energy from photons of sunlight |
| What are photons? | Packets of energy that have properties of particles or waves |
| What characteristic do photons have? | They have the characteristic wavelength (distance covered in one cycle of wave) |
| What is the ruling regarding energetic photons and wavelengths? | Shorter wavelengths have more energy and thus most energetic photons travel at shorter wavelengths |
| Compare red light to blue light. | Red light is a long wavelength and blue light is a short wavelength, although the amplitudes of each wave are the same, more waves per time for blue light. |
| How do photosynthetic pigments work? | Photosynthetic pigments are sensitive to specific ranges of spectrum, electrons within pigments are excited by a specific wavelength of light. |
| What do chlorophyll a and b absorb? | Absorb blue and red wavelengths whilst reflecting and transmitting wave lengths in the middle of visible spectrum (green and yellow) |
| What are carotenoids? | Pigment that absorbs some blue and green wavelengths |
| What are phycobilin? | Pigments that absorb most of green, yellow and orange wavelengths |
| Why do leaves appear green, why do they change color? | Leaves appear green because "chlorophylls" are most abundant pigments, but other pigments are hidden beneath this overpowering green color. In Autumn, chlorophylls break down revealing presence of other pigments. |
| Why are photoautotrophs considered to be primary producers? | Photoautotrophs are considered to be primary producers
they use photosynthesis to produce food for themselves and consumers
at higher trophic levels. |
| Draw a labelled diagram that illustrates the relationship between the two stages of photosynthesis. Refer to your diagram to explain why these stages are considered interdependent. | The diagram illustrating the relationship between the two stages of photosynthesis should show how the products of one stage are used in the reactions of the second stage. In the light-dependent stage, light energy is captured and used to generate high energy NADPH and ATP. In the light-independent stage (the Calvin cycle), these high energy products are used to fix carbon in the form of energy-rich organic molecules. |
| Use a diagram to explain the relationship between the absorption of light energy and electron energy levels within an atom. Describe the three possible fates of an electron after it has jumped to a higher
energy state. | When an electron absorbs light energy and moves from a lower energy level (ground state) to a higher energy level (excited state) within an atom, it can do one of three things:
1. Return to its ground: state by emitting a less energetic photon (fluorescence) or by releasing energy as heat.
2. Return to its ground: state by transferring its energy to a nearby electron in a neighboring pigment molecule.
3. Move to another molecule. |
| Certain marine algae are able to live in low light,
at depths of more than 100 m. These algae appear
almost black deep under water, but usually appear
red when brought to the surface. T/I
(a) Would you expect these species to contain more
or less chlorophyll than green algae? Why?
(b) Would you expect these species to perform
photosynthesis more efficiently under a green
light source or a red light source? Explain your
reasoning.
(c) Things tend to look bluish underwater because
water absorbs red light more effectively than blue
light. How might this fact help account for the
characteristics of the deep-water species of algae? | (a) Algae living in low-light depths have less green chlorophyll and more red pigments, like carotenoids, making them appear red when brought to the surface.
(b) These algae likely photosynthesize more efficiently under green light than red light because red pigments reflect red light and absorb green light.
(c) Deep-water species have adapted to absorb light at the opposite end of the spectrum since very little red light penetrates deep water. When at depth, they reflect red light, but their environment lacks significant red light. |
| What are the thylakoids? Why are they important for photosynthesis? | Thylakoids are flattened, closed sacs inside the chloroplasts
that house the pigments and other molecules
where the light-dependent reactions of photosynthesis take place.
They are important for photosynthesis because the thylakoids are where light energy is actually absorbed to begin photosynthesis. |
| Compare an absorption spectrum of a pigment with the action spectrum for photosynthesis. | The absorption spectrum of a pigment reveals how much light it absorbs at various wavelengths. The action spectrum for photosynthesis indicates the wavelengths of light most useful for driving photosynthesis.
This action spectrum is shaped by the various pigments in a plant's chloroplasts. The combined absorption spectrum of these pigments aligns with the plant's action spectrum, confirming their role in absorbing light for photosynthesis. |
| What 3 steps does light reaction occur? | Pigments in thylakoid membranes that absorb sunlight and give up electrons to membrane proteins, these pigments are organized into 2 photosystems.
Movement of electrons and H+ ions leads to production of NADPH and ATP
Electrons released by pigments are replaced by splitting of H2O (Photolysis) producing O2
Overall result is the formation of ATP + NADPH which is used in the calvin cycle to make glucose |
| In the cell of a plant, what happens regarding light energy and photosystem 2? | Light energy of a certain wavelength (680 NM) excites chlorophyll A in photosystem 2, causing the release of electrons |
| What is photolysis, how does it aid in photosynthesis? | Photolysis is the splitting of water by light; provides electrons to replace those lost by chlorophyll A and oxygen gas |
| What happens to electrons in photosynthesis? | Electrons released by chlorophyll A transfer through a series of proteins in the thylakoid membrane until they reach photosystem 1. |
| Where do the electrons move in the thylakoid membrane, what does this result in? | Just as with ETC the movement of electrons through thylakoid membrane results in a build up of H+ ions within the thylakoid space
H+ ion gradient is used to power synthesis of ATP |
| In the cell of a plant, what happens regarding light energy and photosystem 1? | Light energy (700 nm) excites chlorophyll A in photosystem 1 causing electrons to move into second series of membrane proteins |
| What is the final electron acceptor in photosynthesis? | Coenzyme NADP+ is the final electron accepted, and it is reduced to form NADPH |
| What are ATP and NADPH used for in the calvin cycle? | ATP and NADPH are used in calvin cycle to build organic molecules like glucose |
| Describe how a low-energy electron in water become a high-energy electron on the primary acceptor of a reaction centre. | In photosystem II, the antenna complex absorbs a photon, energizing chlorophyll P680. This excites an electron, which moves to the primary acceptor. P680 becomes positively charged and removes an electron from water, splitting the water molecule. This process repeats, transferring high-energy electrons to the primary acceptor. |
| Sketch the linear electron transport chain that ends with the passing of final electrons to NADP+ to create NADPH. | . |
| Why is light energy essential for photosynthesis to occur? | Light energy is essential for photosynthesis because electrons need a boost of energy from photons of light at photosystems I and II in order for the electron transport to continue. |
| Describe three steps that contribute to the buildup of the proton gradient across the thylakoid membrane. | Three steps that contribute to the buildup of the proton gradient across the thylakoid membrane are
1) the splitting of water inside the membrane by P680+ which increases the concentration of protons in the lumen,
2) the transport of protons into the membrane during electron transport by plastoquinone (PQ) as it moves from photosystem II to the cytochrome complex and back again, and
3) the depletion of protons in the stroma outside the thylakoid by
NADP+ reduction. |
| Why and how do protons move through the thylakoid membrane from the lumen to the stroma? | Protons move through the thylakoid membrane from the lumen to the stroma because there is a higher concentration of protons inside the lumen than outside. They move through the ATP synthase complex releasing free energy that it used to phosphorylate ADP (chemiosmosis). |
| Use a t-chart to compare the electron transport chains found in mitochondria and chloroplasts. | . |
| Consider the analogy of the cyclist (page 224).
(a) Illustrate the analogy. Include labels for photosystem I, photosystem II, and ATP production.
(b) Is the analogy a good one? Why or why not? | b) |
| What happens to the first major step in carbon fixation (Calvin cycle)? | First major in carbon fixation is catalyzed by the enzyme ribulose-1, 5 bisphosphate carboxylase/oxygenase (RuBiCo) |
| What are the 3 sections in calvin cycle? | -Carbon fixation
-Reduction Reactions
-Regeneration of RUBP (Ribulose 1,5-bisphosphate ) |
| What happens in the first phase of the calvin cycle? | Rubisco catalyzes the reaction of 3 CO2, with 3 RuBP to form 6 PGA |
| What happens in the second phase of the calvin cycle? | 6 PGA are "Reduced" to form 6 "1,3-BPG" which is then "reduced" to 6 G3P. These reactions require 6 ATP and 6 NADPH |
| What happens in the third phase of the calvin cycle? | 5 G3P molecules are used to regenerate the 3 RuBP we began with. 3 ATP are required. 1 G3P can go towards making glucose. 2 turns of the Calvin cycle to make a glucose. 9 ATP and 6 NADPH used total |
| What is another name for calvin cycle, why is this incorrect? | Another name for the calvin cycle is "dark reaction" or "Light independent reaction" and is misleading since although light is not needed directly, the products of light reactions are. Calvin cycle indirectly requires light. |
| Simplified over-view of photosynthesis | . |
| Careful measurements indicate that the Calvin cycle in a plant leaf is occurring very slowly. In such a situation, there is a reduced demand for both NADPH and ATP.
(a) What benefit (if any) would the light-dependent reactions still have for this plant?
(b) Can you think of any environmental conditions under which such a situation might arise? | (a) The light-dependent reactions would still be supplying the NADPH and ATP that the
Calvin cycle requires, even though it is occurring very slowly.
(b) This situation might arise if the plant is in a very hot or very dry environment. The stomata of
the leaf may close to conserve water, which would also block the intake of carbon dioxide. |
| Analysis of a plant’s leaf showed an unusually high amount of ATP, but relatively little NADPH. Which
electron transport method is probably working much more predominantly in this leaf? Which photosystem is probably absorbing more light energy? Explain your answer. | Cyclic electron transport is likely working much harder in a leaf with an unusually high amount of ATP and relatively little NADPH than the linear electron transport chain, since cyclic electron transport creates ATP, but not NADPH. Photosystem II does not factor into cyclic electron transport, so photosystem I is absorbing more light energy than photosystem II. |
| Rubisco is the world’s most abundant protein, yet it is not found inside any animal cells. Suggest a
reason why animals do not need or use this protein. | Animals don’t need or use rubisco because they don’t need to fix carbon dioxide since they obtain carbon that is already fixed by consuming other organisms. |
