biology energy processing -...
TRANSCRIPT
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Biology
Energy Processing
www.njctl.org
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Vocabulary
glycolysis
aerobic anabolic pathwayanaerobic
Calvin Cycle
chlorophyllcellular respiration
FADH2
fermentation
lactic acid fermentation
metabolism
ATP
NADHcitric acid cycle
electron transport chain
Krebs cycle
electron acceptor
facultative anaerobe
Acetyl Co-A
ATP synthase
NADPH
catabolic pathway
ethanol fermentation
cyclic energy transport
light dependent reactionslight independent reactions
Click on each word below to go to the definition.
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Vocabulary
pyruvate
oxidation
reductionpyruvate decarboxylation
phosphorylationoxidative phosphorylation
obligate anaerobeobligate aerobe
photosynthesisphotosystem Iphotosystem II
noncyclic energy transport
thylakoid
Click on each word below to go to the definition.
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Energy Processing Unit Topics
· Metabolism & ATP
· Cellular Respiration
Click on the topic to go to that section
· Fermentation
· Photosynthesis
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Chapter 8Metabolism & ATP
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Metabolism is the totality of an organism’s chemical reactions.
Metabolism is a property of all life.
Metabolic Pathways
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A metabolic pathway begins with a specific molecule and ends with a product
Each step is catalyzed by a specific enzyme
Without enzymes, metabolic pathways would proceed very slowly.
Metabolic Pathways
enzyme 1 enzyme 2 enzyme 3
A B C D
Starting Molecule
Product
Reaction 1 Reaction 3Reaction 2
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There are two types of metabolic pathways:
Catabolic pathways
Anabolic pathways
Metabolic Pathways
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Catabolic pathways break down molecules from the environment.
Living things use the energy derived from breaking the bonds in these molecules to build structures and drive cell processes.
Catabolic Pathways
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Reactants
Energy
Products
Progress of the reaction
Free
ene
rgy
Amount of free energy
released (ΔG<0)
Exergonic ReactionCatabolic pathways are exergonic reactions; the change in Gibbs free energy is negative. Thus, they release energy and occur spontaneously
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Anabolic pathways synthesize complex organic molecules and power cell processes using the energy derived from catabolic pathways.
Anabolic Pathways
Examples:building bonesbuilding musclebuilding starchpowering active transport
Click here for a pneumonic device
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Reactants
Energy
Products
Progress of the reaction
Amount offree energy
required(ΔG > 0)
Free
ene
rgy
Endergonic ReactionAnabolic pathways are endergonic reactions; the change in Gibbs free energy is positive. Thus, they require an input of energy and do not occur spontaneously
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A process will occur spontaneously if the result is a reduction of the Gibbs Free Energy (G) of the system.
G takes into account the resulting change in the energy of a system and the change in its entropy.
If the effect of a reaction is to reduce G, the process will proceed spontaneously.
If ∆G is negative, the reaction will occur spontaneously.
If ∆G is zero or positive, it will not occur spontaneously.
Spontaneous Processes
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Free Energy and Metabolism
Biological systems often need an endergonic reaction to occur, but on it's own, it won't proceed spontaneously.
To be able to occur, the endergonic reaction is coupled to a reaction that is exergonic, so that together, they are exergonic.
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NH2
Glu
Non-spontaneous reaction: ∆G is positive
∆G = +3.4 kcal/molNH3Glu
Glutamicacid
Ammonia
+
ATP + H2O ADP
Spontaneous Reaction: ∆G is negative
+ Pi
∆G = -7.3 kcal/mol
∆G = –3.9 kcal/moltogether, reactions are spontaneous
Adding Coupled Reactions
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1 A spontaneous reaction _____.
A occurs only when an enzyme or other catalyst is present
B cannot occur outside of a living cellC releases free energy when proceeding in the forward
directionD is common in anabolic pathways
E leads to a decrease in the entropy of the universe
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2 Anabolic pathways are ___________ and catabolic pathways are ______________.
A spontaneous, non-spontaneousB endergonic, exergonicC exergonic, endergonicD endothermic, endergonic
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3 Which of the following correctly states the relationship between anabolic and catabolic pathways?
A Degradation of organic molecules by anabolic pathways provides the energy to drive catabolic pathways.
B Energy derived from catabolic pathways is used to drive the breakdown of organic molecules in anabolic pathways.
C Anabolic pathways synthesize more complex organic molecules using the energy derived from catabolic pathways.
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A cell does three main kinds of work:
· Mechanical (motion)· Transport (crossing a barrier)· Chemical (changing a molecule)
To do work, cells manage energy resources by energy coupling, using an exergonic reaction to drive an endergonic one
Cell Energy
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ATP
Cells can store the energy from catabolic pathways in a molecule called ATP (adenosine triphosphate). ATP can be broken down later to fuel anabolic reactions.
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ATP (adenosine triphosphate) includes three phosphate groups (PO4
-3).
Each Phosphate group has an ionic charge of -3e.
In this model of ATP, each PO4-3
is circled in blue.
ATP
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ATP
The phosphate groups repel each other, since they each have a negative charge.
Therefore it requires Work to add the second phosphate group; to go from AMP (monophosphate) to ADP (diphosphate).
To add the third group, to go from ADP to ATP (triphosphate), requires even more work since it is repelled by both of the other phosphate groups.
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ATPThis is like the work in compressing a spring.
The energy from the work needed to bring each phosphate group to the molecule is stored in that phosphate bond.
When the bond is broken to go from ATP to ADP, significant energy is released.
Going from ADP to AMP releases less energy, since there is less total charge in ADP than ATP.
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The bonds between the phosphate groups of ATP’s tail can be broken by hydrolysis.
Energy is released from ATP when the terminal phosphate bond is broken.
The released energy is equal to the work that was done to form the bond. That work overcame the electrostatic repulsion between the last phosphate group and the initial ADP molecule.
The result is a chemical change to a state of lower free energy.
ATP
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In the living systems, the energy from the exergonic reaction of ATP hydrolysis can be used to drive an endergonic reaction.
Overall, the coupled reactions are exergonic.
ATP
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ATP Performs Work
ATP drives endergonic reactions by phosphorylation, transferring a phosphate group to some other molecule, such as a reactant.
The recipient molecule is now "phosphorylated".
The three types of cellular work are powered by the hydrolysis of ATP.
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NH2
Glu
Pi
P i
P i Pi
Glu NH3
P
P
P
ATPADP
Motor protein
Mechanical work: ATP phosphorylates motor proteins
Protein moved
Membraneprotein
Solute
Transport work: ATP phosphorylates transport proteins
Solute transported
Chemical work: ATP phosphorylates key reactants
Reactants: Glutamic acidand ammonia
Product (glutamine)made
+ +
+
ATP Performs Work
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The Regeneration of ATP
ATP is a renewable resource that is regenerated by addition of a phosphate group to ADP
The energy to phosphorylate ADP comes from catabolic reactions in the cell
The chemical potential energy temporarily stored in ATP drives most cellular work
Each cell is converting millions of ATP to ADP and back again every second.
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Pi
Energy for cellular work (endergonic, energy consuming processes)
Energy from catabolism(exergonic, energyyielding processes)
+
ATP
ADP
The Regeneration of ATP
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4 In general, the hydrolysis of ATP drives cellular work by _____.
A releasing free energy that can be coupled to other reactionsBreleasing heatCacting as a catalystD lowering the free energy of the reaction
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5 What best characterizes the role of ATP in cellular metabolism?
A The release of free energy during the hydrolysis of ATP heats the surrounding environment.
BThe free energy released by ATP hydrolysis may be coupled to an endergonic process via the formation of a phosphorylated intermediate.
C It is catabolized to carbon dioxide and water.D The ΔG associated with its hydrolysis is positive.
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6 Which of the following is not an example of the cellular work accomplished with the free energy derived from the hydrolysis of ATP?A Mechanical work, such as the movement of the cell
B Transport work, such as the active transport of an ion into a cell.
C Chemical work, such as the synthesis of new proteins.
D The production of heat, which raises the temperature of the cell.
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Cellular Respiration
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Equilibrium and Metabolism
Reactions in a closed system eventually reach equilibrium and then stop.
Life is not in equilibrium
Life is an open system , experiencing a constant flow of materials and energy.
Life cannot survive without connection to the environment.
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The Production of ATPCatabolic Pathways
Cellular respiration is a catabolic pathway that consumes organic molecules and yields ATP.
Carbohydrates, fats, and proteins can all fuel cellular respiration.
We'll look first at the simplest case, the breakdown of the sugar - glucose.
But before doing that we have to learn about two molecules that are essential to respiration.
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NAD+ + 2H+ + 2e- + Energy NADH + H+
NAD+ and FADThe molecules NAD+ and FAD are used to store, and later release, energy during respiration; they are key to respiration.
Each molecule has two forms, each form stores a different amount of energy. So moving between those two forms either stores chemical potential energy or releases it.
Here are the reactions:
FAD + 2H+ + 2e- + Energy FADH2
The double arrows indicate that each reaction is reversible, they can proceed in either direction. When the reaction goes to the right, energy is stored. When it goes to the left, energy is released
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NAD+ and FAD
The amount of energy that is useable when the reaction goes to the left, depends on the availability of electron acceptors. Without a molecule, such as O2, to accept the excess electrons the energy stored in NADH and FADH2 cannot be used to make ATP.
NAD+ + 2H+ + 2e- + Energy NADH + H+
FAD + 2H+ + 2e- + Energy FADH2
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Electron Acceptors
Oxygen is the best electron acceptor because it generates the greatest free energy change (#G) and produces the most energy.
In the absence of oxygen, other molecules, such as nitrate, sulfate, and carbon dioxide can be used as electron acceptors.
If O2 is present, · 1 NADH stores enough energy to create about 3 ATPs
· 1 FADH2 stores enough energy to make about 2 ATPs
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7 NADH is converted to NAD+. During this process,
A energy is releasedB energy is storedC no energy is stored or released
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8 FADH2 is converted to FAD. During this process,
A energy is storedB energy is releasedC no energy is stored or released
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Reduction and Oxidation
When we go from left to right we are adding electrons to a molecule. That is called reducing the molecule, or the process of reduction.
Going from right to left, we are taking electrons from a molecule. That is called oxidizing the molecule, or the process of oxidation.
NAD+ + 2H+ + 2e- + Energy NADH + H+
FAD + 2H+ + 2e- + Energy FADH2
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The reason for the term oxidation is that this is the effect that oxygen usually has: it takes electrons from a molecule, oxidizing the molecule
The rusting of iron is an example of oxidation: oxygen is taking electrons from the metal, oxidizing it.
Oxidation
4 Fe + 3 O2 → 2 Fe2 O3
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Reduction and Oxidation
LEO says GER
Losing
Electrons is
Oxidation
Gaining
Electrons is
Reduction
Since it doesn't seem right that adding electrons is called "reduction"; here's a way to remember these two terms.
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9 Which of the following cannot act as an electron acceptor?
A sulfateB oxygenC ammoniaD nitrate
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10 The loss of an electron is __________ and the gain of an electron is ____________.
A oxidation, reductionB reduction, oxidationC catalysis, phosphorylationD phosphoroylation, catalysis
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11 NADH is the reduced form of NAD+.
TrueFalse
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Types of Cellular Respiration
Cells follow different paths of cellular respiration depending on the presence or absence of oxygen.
Cells can be classified into 3 categories based on their response to oxygen.
· Obligate Anaerobes - which cannot survive in the presence of oxygen
· Obligate Aerobes - which require oxygen
· Facultative Anaerobes - which can survive in the presence or absence of oxygen.
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The Stages of Respiration
Cellular respiration consists of four stages:
· Glycolysis · Pyruvate Decarboxylation· The Citric Acid Cycle (Krebs Cycle)· Oxidative Phosphorylation
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The net result is:a net of 2 ATPs are formed along with 2 NADHs and the 2 pryuvates.
Glycolysis means the splitting of glucose
Some ATP is needed to start the process (Ea)
C6H12O6(Glucose)
Gycolysis
2 ATP
4 ATP2 NADH
2 C3H4O3 (Pyruvate)
2 NAD+
Glycolysis
Glycolysis is the first stage of cellular respiration. It involves the breakdown of glucose, a 6 carbon sugar, into 2 molecules of pyruvate, a 3 carbon sugar.
Glycolysis means the splitting of glucose
The net result is:a net of 2 ATPs are formed along with 2 NADHs and the 2 pryuvates.
Some ATP is needed to start the process (Ea)
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12 Until 2.5 billon years ago there was no oxygen in the Earth's atmosphere. Which of the following was also not present?
A facultative anaerobesB obligate anaerobesC obligate aerobesD bacteria
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13 How much activation energy is required to start glycolysis?
A 0 ATPB 1 ATPC 2 ATPD 4 ATP
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14 The net products of glycolysis are:
A 2 pyruvateB 2 NADH and 2 pyruvateC 2 ATP, 2 NADH, and 2 pyruvateD 4 ATP, 2 NADH, and 2 pyruvate
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Pyruvate Decarboxylation (PD)The Citric Acid Cycle can only process 2-carbon molecules, and pyruvate is a 3-carbon molecule: C3H4O3
PDC
2 NADH
2 NAD+
2 C3H4O3 (Pyruvate)
2 CO2
2 Acetyl Co-A
PD is an enzyme catalyzed reaction that takes the 2 pyruvate molecules and converts them to 2 Acetyl Co-A molecules: these are 2-carbon molecules.
Energy is stored during PD by the converting 2 NAD+ to 2 NADH and the extra pyruvate carbons are expelled as CO2.
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The Citric Acid Cycle
This shows one cycle, which is due to one Acetyl Co-A molecule.
To account for one glucose molecule, two cycles are needed.
Let's tally up the output for one cycle to confirm our results.
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1 ATP3 NADH1 FADH2
The Citric Acid Cycle
1 ATP3 NADH1 FADH2
2 ATP6 NADH2 FADH2
But 1 glucose molecule, yields 2 Acetyl Co-A molecules, (therefore, 2 turns of the cycle) yielding :
This is one turn of the cycle, due to 1 Acetyl Co-A. Note the production of:
Click here for a video of the Citric Acid Cycle
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The citric acid cycle is sometimes called the Krebs cycle.
The cycle breaks down one Acetyl-CoA for each turn, generating1 ATP, 3 NADH, 2 CO2 and 1 FADH2 per Acetyl-CoA.
Since 2 Acetyl-CoA molecules were created from each glucose, the
Citric Acid Cycle creates 2 ATP; 6 NADH; 4CO2, and 2 FADH2 for each glucose molecule.
The Citric Acid Cycle
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15 Glycolysis produces ____ ATP.
Pyruvate Decarboxylation produces ____ ATP.
The Citric Acid Cycle produces _____ ATP.
A 1, 1, 2B 4, 0, 2C 4, 0, 4D 2, 0, 2
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16 During pyruvate decarboxylation, 3-carbon pyruvate is converted to 2-carbon Acetyl-CoA. What happens to the excess carbons atoms in this process?
A They are expelled in molecules of CH4
B They are expelled in molecules of CO2
C They are covalently bonded to NADHD They are recycled to reform glucose
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17 In total, the first 3 stages of cellular respiration produce how many molecules of carbon dioxide?
A 1B 2C 3D 6
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So far we've done a lot of work to just get a net gain of 4 ATPs.
But we have stored a lot of potential energy in the form of
NADH and FADH2.
The big energy payoff is in oxidative phosphorylation, where we convert the energy stored in those molecules to ATP.
Oxidative Phosphorylation (OP)
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Stage NADH FADH2 ATP
Glycolysis 2 0 2
PD 2 0 0
CAC 6 2 2
Total 10 2 4
Oxidative Phosphorylation (OP)We're now going to convert all the NADH and FADH2 into ATP, so the energy can be stored throughout the cell.
Here's what we start this cycle with.
When O2 is present, we get about 3 ATPs per NADH and 2 ATPs per FADH2. So how many ATPs would we have at the end of this next stage?
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Oxidative phosphorylation is powered by the electron transport chain. One way to think of the ETC is as a proton pump.
The ETC transports electrons, through chemical reactions, out and then back through a plasma membrane. The net effect is to pump protons from the inside to the outside of a plasma membrane, creating a proton gradient which is used to power oxidative phosphorylation.
Electron Transport Chain (ETC)
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Electron Transport Chain (ETC)
The electron path is shown in black.
The proton path in red.
The ETC generates no ATP, but enables Oxidative Phosphorylation, which accounts for most of the ATP produced.
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Anaerobic ETC
For the first 2 billion years of life on Earth, anaerobic (no O2) respiration was the only means of obtaining energy from food.
These organisms used the electron acceptors, NO3-, SO42-, or
CO2 to pull the electrons through the ETC. These molecules would accept the electrons at the end of the chain forming N2, H2S, and CH4 respectively.
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Aerobic ETC
Click here for a video of the ETC
But then, the Oxygen Revolution occurred about 2.5 BYA, flooding the planet with oxygen.
In aerobic respiration, the final electron acceptor of the electron transport chain is O2; forming water (H2O). Oxygen strongly attracts electrons in order to fill its outer shell. This stronger pull makes much more energy available to life, enabling the more complex food chains we see today.
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18 Which of the following is created during the electron transport chain in human cells?
I ATP
II NADH
III proton gradient
IV H2O
A I, II, III, IVB I, II onlyC III onlyD III, IV only
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19 Obligate aerobes use which of the following as their final electron acceptor?
A CO2
B NO3-
C O2
D SO42-
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Oxidative Phosphorylation (OP)The ETC creates a positive electrostatic potential outside the plasma membrane and a negative potential inside. The excess protons outside, are strongly attracted to the inside, but are blocked by the membrane. One path is open to the protons, but they must do work to use it.
ATP Synthase is essentially a motor, constructed of proteins. The protons must travel through that motor in order to return to the cell, creating an electric current that powers the motor.
As the motor turns, it adds a phosphate group to ADP, creating ATP. Electrical energy is transformed to chemical energy.
Click here for a video of ATP Synthase
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Oxidative PhosphorylationThe Hydroelectric Analogy
The Hoover Dam is a massive structure that holds back the potential energy of 9 trillion gallons of water
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Like oxidative phosphorylation,it creates a gradient then exploits the stored energy by allowing water to pass through a small pipeline, transforming it to kinetic energy.
Oxidative PhosphorylationThe Hydroelectric Analogy
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Massive turbines are spun, causing the kinetic energy to be turned into mechanical energy which is utilized to make electrical energy.
Oxidative PhosphorylationThe Hydroelectric Analogy
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We calculated earlier that we would expect to get 38 ATP molecules by the time we'd converted all the NADH and FADH2 to ATP.
The actual yield is between 36 - 38 ATP molecules per glucose molecule.
The reason for the small variance is that in some cases energy is needed to transport the NADH molecules to the site of the ETC.
Aerobic Respiration
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20 ATP synthase...
A synthesizes ATPB is an enzymeC is a protein complexD all of the above
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21 Energy released by the electron transport chain is used to pump H+ ions into which location?
A Outside the membraneB Inside the membrane
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22 What is the maximum number of ATP produced from a breakdown of a glucose molecule?
A 4B 18C 36D 38
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The Versatility of Catabolism
Catabolic pathways funnel electrons from many kinds of organic molecules into cellular respiration.
· Glycolysis accepts a wide range of carbohydrates
· Proteins must be digested to amino acids; amino groups can feed glycolysis or the citric acid cycle
· Fats are digested to glycerol which is used in glycolysis. An oxidized gram of fat produces more than twice as much ATP as an oxidized gram of carbohydrate
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The Versatility of Catabolism
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Fermentation
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When no electron acceptors are available, obligate anaerobes and facultative anaerobes can still break down glucose to release energy through a process called fermentation.
Fermentation
Fermentation begins just as cellular respiration does, with glycolysis.
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FermentationGlycolysis results in 2 pyruvate molecules and 2 NADH2
molecules. Without an electron acceptor, the energy stored in these molecules can't be used.
The net energy gain is just 2 ATPs. (Remember 2 were invested and 4 were produced, netting 2)
C6H12O6
(Glucose)
Gycolysis
2 ATP
4 ATP2 NADH
2 C3H4O3 (Pyruvate)
2 NAD+
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However, the Pyruvate still needs to be cleared from the cell, and the NADH converted back to NAD+ to begin another cycle.
The process of doing this is called fermentation.
No additional energy is released during this process.
Fermentation
C6H12O6
(Glucose)
Gycolysis
2 ATP
4 ATP2 NADH
2 C3H4O3 (Pyruvate)
2 NAD+
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Fermentation
2 NADH
2 NAD+
2 C3H4O3 (Pyruvate)
CO2 & 2 Ethanol
2 LacticAcid
Lactic AcidFermentation
EthanolFermentation
OR
Types of FermentationThere are two types of fermentation:
· Lactic acid fermentation
· Ethanol fermentation
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CO2 & Ethanol.
The pyruvates and NADHs are fermented into 2 NAD+ and either Lactic Acid or
1 glucose molecule had yielded 2 ATPs, 2 Pyruvates and 2 NADHs. That is the input to the fermentation stage of anaerobic respiration.
Fermentation
2 NADH
2 NAD+
2 C3H4O3 (Pyruvate)
CO2 & 2 Ethanol
2 LacticAcid
Lactic AcidFermentation
EthanolFermentation
OR
1 glucose molecule had yielded 2 ATPs, 2 Pyruvates and 2 NADHs. That is the input to the fermentation stage of anaerobic respiration.
FermentationFermentation breaks down the products of glycolysis so that glycolysis can be repeated with another glucose molecule.
The pyruvates and NADHs are fermented into 2 NAD+ and either Lactic Acid or CO2 & Ethanol.
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Fermentation
The result of the combined steps of glycolysis and fermentation is:
· The input is 1 Glucose + 2 ATP molecules
· The output is 4 ATP molecules (for a net gain of 2 ATP's)
In addition,
· Lactic Acid fermentation results in lactic acid
· Ethanol fermentation results in ethanol and CO2
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The big difference is that for each glucose molecule:
aerobic cellular respiration yields 36 to 38 ATPs
fermentation yields only 2 ATPs
Cellular Respiration vs. Fermentation
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· Some anaerobic bacteria rely soley on fermentation, such as lactobacillus, which is used to make cheese and yogurt.
· The alcohol in wine, beer, etc. results from yeast (a facultative anaerobe) undergoing ethanol fermentation.
· Bread rises due to the release of CO2 bubbles by fermenting yeast.
· Your muscles burn after a strenuous workout because they can't get enough O2, so they perform lactic acid fermentation. Lactic acid results in soreness.
Examples of Fermentation
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23 When a cell has completed glycolysis and lactic acid fermentation, the final products are:
I Lactic acid
II Ethanol
III Carbon dioxide
IV NADH
V ATP
A I, II, III, IV, VB I, II, III, VC I, IV, VD I, V
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24 Bread rises due to the production of _______ during fermentation.
A ethanolB carbon dioxideC lactic acidD pyruvate
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25 Muscles produce lactic acid during strenuous exercise. Therefore, muscles are an example of what kind of cell?
A facultative anaerobeB facultative aerobeC obligate anaerobeD obligate aerobe
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Photosynthesis
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Respiration gets energy from glucose and stores it as ATP.
But what is the source of glucose?
And, where did the oxygen that flooded Earth 2.5 BYA come from?
Photosynthesis
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Here's the balanced chemical equation for aerobic respiration:
And here's the balanced chemical equation for photosynthesis:
C6H12O6 + 6O2 6CO2 + 6H2O + ATP
6CO2 + 6H2O + Light Energy C6H12O6 + 6O2
Aerobic Respiration vs. Photosynthesis
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Aerobic respiration uses oxygen (O2) and glucose (C6H12 O6) to create carbon dioxide (CO2) and water (H2O)...and release energy.
Photosynthesis is the exact opposite, it takes carbon dioxide (CO2) and water (H2O) plus energy to make glucose (C6H12 O6) and oxygen (O2)
Aerobic Respiration vs. Photosynthesis
C6H12O6 + 6O2 6CO2 + 6H2O + ATP
6CO2 + 6H2O + Light Energy C6H12O6 + 6O2
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Photosynthesis and Respiration
Summing these two equations reveals that the ATP used by cells is derived from light energy, from the sun. That is the source of energy for most life on Earth.
C6H12O6 + 6O2 6CO2 + 6H2O + ATP (Energy)
6CO2 + 6H2O + Light Energy C6H12O6 + 6O2
Light Energy ATP (Energy)
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Except for a small number of bacteria that live on chemical reactions in challenging environments, the energy for all life on Earth comes from these processes...from the energy of sunlight. Even though not every organism undergoes photosythesis, the products that plants produce are used in reactions that consumers use. In this way, you can say that . . .
You are solar powered!
Light Energy ATP (Energy)
Photosynthesis and Respiration
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26What are the reactants of cellular respiration?
A Oxygen and Water
B Glucose and Carbon Dioxide
C Glucose and Water
D Glucose and Oxygen
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27What are the products of photosynthesis?
A Glucose and Oxygen
B Oxygen and Water
C Glucose and Carbon Dioxide
D Carbon Dioxide and Water
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28What are the reactants of photosynthesis?
A Carbon Dioxide and Water
B Oxygen and Water
C Glucose and Oxygen
D Glucose and Carbon Dioxide
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29Photosynthesis ____________ energy, whereas cellular respiration __________ energy.
A consumes, produces
B produces, consumes
C produces, produces
D consumes, consumes
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What is the source of glucose?
Where did the oxygen that flooded Earth 2.5 BYA come from?
Our Original Questions
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The products of photosynthesis are:
· oxygen (O2) · glucose (C 6H12O6)
Photosynthesis produces the glucose that feeds respiration, and eventually, all of us.
Photosynthesis also produces the oxygen that filled the atmosphere and made complex life, as we know it possible.
Photosynthesis
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Photosynthesis and the addition of oxygen to Earth's atmosphere, began about 2.5 BYA, and was having a major impact by 2.0 BYA.
This is called the Oxygen Catastrophe because it spelled the extinction of a vast number of obligate anaerobes. Some survive today, but only in locations where they are not exposed to the atmosphere.
The Oxygen Catastrophe
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This simple equation sums up the result of photosynthesis: its reactants and products.
However, the processes that make photosynthesis possible are not very simple.
Just like the four stages of respiration result in a simple equation, the process itself is complicated.
Similarly, the process of photosynthesis is complicated. And in some ways similar to the steps of respiration, but backwards.
Photosynthesis
6CO2 + 6H2O + Light Energy C6H12O6 + 6O2
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30 In the comparison of aerobic respiration to photosynthesis, which statement is true?
Aoxygen is a waste product in photosynthesis but not in respiration
Bglucose is produced in respiration but not in photosynthesis
Ccarbon dioxide is formed in photosynthesis but not in respiration
D water is formed in photosynthesis but not in respiration
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During respiration the molecules NAD+and FAD are used to store energy.
Photosynthesis uses the molecule NADP+, which is a lot like NAD+, to store energy, and convert it between its two stages.
The reduced form of NADP+ is NADPH.
NADPH
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Photosynthesis also depends on chlorophyll, a molecule that absorbs red and violet-blue light and uses it to energize electrons to a higher energy level.
Chlorophyll
Chlorophyll gives plants their green color.
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Chlorophyll is housed in thylakoids, membrane-bound structures within photosynthetic cells.
Thylakoids
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31 NAD+ is to NADP+ as NADH is to ______.
A NADP2+
B NADPC NADPHD NADPH2
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32 Which of the following is found stored in the thylakoid?
A ATPB chlorophyllC NADHD NADPH
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There are two types of photosynthesis:
Cyclic Energy Transport
Non-Cyclic Energy Transport
Two Types of Photosynthesis
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Cyclic Energy Transport was probably the first type of photosynthesis to originate.
It does not create glucose, it just converts solar energy to ATP.
Cyclic Energy Transport
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e-
e-
Photosystem IElectron
Transport Chain
ADP + P i
ATPATP
Synthase
Ene
rgy
of m
olec
ules
chlorophyll
e-
e-
photon
This process is "cyclic" because the final electrons return to chlorophyll after ATP is generated.
Cyclic Energy TransportCyclic Energy Transport uses Photosystem I, a protein complex embedded in the thylakoid membrane to convert light energy to ATP.
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33 Noncyclic energy transport arose before cyclic energy transport.
TrueFalse
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34 Which of the following statements about cyclic energy transport is true?
A Cyclic energy transport requires water.B Glucose is produced by cyclic energy transport.C Cyclic energy transport reduces NADP+
D Light energy is converted to chemical energy during cyclic energy transport.
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There are two major stages to Noncyclic Energy Transport:
Light Dependent Reactions
Light Independent Reactions (Calvin Cycle)
Noncyclic Energy Transport
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Light Dependent Reactions occur in membrane bound structures called thylakoids.
It's necessary to have a membrane surface separating the inside from the outside on an enclosed volume, thylakoids provide that. The inside is called the lumen; the outside is called the stroma.
Light Dependent Reactions
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Light Dependent Reactions
2 H2O + 2 NADP+ + 3 ADP + 3 Pi O2 + 2NADPH + 3 ATP
The Light Dependent Reactions use light energy and water to form ATP, NADPH, and oxygen gas.
This process requires 2 photosystems, Photosystem II and Photosystem I. They occur in this order (they were named in the order in which they were discovered).
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ThylakoidThis shows the membrane, separating the stroma from the lumen, the two photosystems and the enzymes, ATP Synthase and NADP Reductase.
The light reactions will use Photosystem II and Photosystem I to create an excess of protons in the stroma, and a deficit in the lumen.
The only way protons can get back to the lumen, is through ATP Synthase, to produce ATP.
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Photosystem IIFirst, Photosystem II absorbs light and energizes electrons, splitting a water molecule in the process. Those are used to pump protons across the membrane, creating an electrical potential difference which is used to create ATP.
e-
e-
Photosystem IIElectron
Transport Chain
ADP + P i
ATPATP
Synthase
chlorophyll
e-
e-
photon
to Photosystem IH2O
O2+2H+
Ene
rgy
of m
olec
ules
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Photosystem I
chlorophyll
e-
e-e-
Photosystem I
e-
from Photosystem II
NADP Reductase NADP+
NADPH
photon
Ene
rgy
of m
olec
ules
Then, Photosystem I absorbs more light and re-energizes those electrons. They are used to store energy by using NADP Reductase to reduce NADP+ to NADPH (adding electrons to NADP+, instead of returning them to chlorophyll as in cyclic energy transport).
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35 The inside of the thylakoid is called the ______ and the outside is called the ______.
A lumen, stromaB stroma, lumen
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36 Light dependent reaction produce ____ ATP and ____ NADPH for each O2 produced.A 1, 1B 2, 3C 3, 2D 2, 4
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37 Water is split, releasing O2, in which protein complex?
A photosystem IB photosystem IIC ATP synthaseD NADP reductase
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Light Independent ReactionsThe ATP and NADPH created during the light dependent reactions proceed to the Light Independent Reaction. The light independent reactions are also know as the Calvin Cycle or Dark Reactions.
These reactions can occur in light or dark, thus dark reactions is not an accurate name.
The Calvin Cycle uses the ATP and NADPH to convert CO2 into Glucose (C6H12 O6) in a multi step process.
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Light Independent Reactions
In 3 turns of the cycle we use9 ATPand 6 NADPHand 3 CO2
to make a 3-carbon sugar
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Light Independent Reactions
To make one 6-carbon glucose molecule:18 ATPand 12 NADPHand 6 CO2 are required.
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The Carbon Cycle
The Calvin Cycle is also called Carbon Fixing.
This means that carbon, a gas in the atmosphere, in the form of CO2 , is turned into a solid as a glucose. When glucose is used in respiration, that carbon is then released back into the atmosphere.
This process of fixing and releasing carbon is called the Carbon Cycle. Carbon is not being created or destroyed, but cycles through the environment.
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The Light Reactions produce equal amounts of ATP and NADPH, but the Calvin Cycle use more ATP (18) than NADPH (12) to make a glucose molecule.
To have enough ATP, photosynthetic organisms use Cyclic Energy Transport to create the needed ATP.
Cyclic vs. Noncyclic Energy Transport
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38 Carbon dioxide is fixed in the form of glucose in
A Krebs cycleB light-dependent reactionsC Calvin cycleD cyclic energy transport
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39 During what stage of photosynthesis are ATP and NADPH coverted to ADP + Pi and NADP+?
A light dependent reactionsB light independent reactionsC photosystem ID photosystem II
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40 Which of the following statements about photosynthesis is true?
AThe light dependent reactions can only occur in the light, the light independent reactions can only occur in the dark.
B Cyclic energy transport is more efficient at producing glucose than noncyclic energy transport.
C The light dependent reactions produce ATP which is used to power the Calvin cycle.
D Cyclic energy transport occurs only in bacteria.
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41 The Calvin cycle is an anabolic pathway.
TrueFalse
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Global Climate Change
The carbon cycle plays a key role in Global Climate Change.
Photosynthesis releases oxygen into the air, but also takes CO2 out of the air.
CO2 is a greenhouse gas, it absorbs infrared light that would otherwise carry heat away from Earth, into space; cooling Earth.
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Global Climate Change
If it were not for CO2, and other greenhouse gases, Earth would be far colder, perhaps too cold to support life as we know it.
Greenhouse gases are essential for life.
However, the amount of greenhouse gases in Earth's atmosphere is critical to maintaining a constant average temperature for the planet.
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Global Climate Change
A great deal of carbon was trapped under the surface of Earth by life forms that died over many millions of years; effectively taking that carbon out of the carbon cycle.
That reduced the CO2 in the atmosphere, reducing the temperature of Earth by allowing more heat to leave, leading to our current temperature.
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Global Climate Change
The hydrocarbons we use for energy (oil and natural gas) were formed from the breakdown of that long-dead plant and animal life.
As we burn those fuels, we are releasing CO2 back into the atmosphere, increasing the greenhouse gases in the atmosphere.
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Global Climate Change
As a result, more heat is being trapped in our atmosphere; the balance of energy brought to Earth by solar energy, and released from Earth in infrared radiation is being changed.
This is causing Earth's average temperature to rise.
The effect of this temperature rise is not that the temperature goes up in all places or in all years necessarily.
But it is projected that there will be massive changes in climate in the future, with accompanying changes in sea level, crops, plant and animal life, etc.
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42 Greenhouses gases are dangerous and should be reduced as much as possible.
TrueFalse
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43 Carbon was used from the carbon cycle, reducing CO2 in the air, as __________
A the amount of life on Earth decreasedB as animals died and were buried under earthC fermentation beganD All of the aboveE None of the above
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44 A very warm winter in New Jersey this year would indicate that global climate change is occurring.
TrueFalse
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