Studied by 7 peopleDuring respiration, most ATP is formed as a direct result of the net movement of
Protons (hydrogen ions) down a concentration gradient
According to the chemiosmotic theory (chemiosmotic coupling), the energy required to move protons from the mitochondrial matrix to the intermembrane space against a concentration gradient comes most directly from
Electrons flowing along the electron transport chain
Where do high energy electrons come from in cell respiration?
NADH and FADH2
In what process is O2 released as a by-product of oxidation-reduction reactions
Light-dependent reactions of photosynthesis
What is photolysis?
The splitting of a water molecule using light energy
How is oxygen released in the beginning of the light-dependent reactions?
Through the stomata
In what process is CO2 released as a by-product of oxidation-reduction reactions?
The Krebs Cycle
In what process is carbon from CO2 incorporated into organic molecules?
Calvin cycle (light-independent reactions of photosynthesis)
How does cell respiration effect pH?
pH is more acidic (lower)
What is photophosphorylation?
Adding phosphate to a molecule using light
What is photosynthesis?
The process that converts solar energy into chemical energy
What are autotrophs?
Organisms that produce their own food
What are heterotrophs?
Organisms that obtain food by consuming other living things
Where do carbon dioxide and oxygen enter and exit a leaf?
The stomata
What is the stomata?
Small holes in a leaf that allow gas exchange to occur
How many chloroplasts does a typical mesophyll cell have?
30-40
Where is chlorophyll stored?
Thylakoid membrane
What is stroma?
Fluid portion of the chloroplast; outside of the thylakoids
What are thylakoids?
Saclike photosynthetic membranes found in chloroplasts
What is the equation for photosynthesis?
6 CO2 + 6 H2O + light energy → C6H12O6 + 6 O2
What is the equation for cellular respiration?
C6H12O6 + 6 O2 → 6 CO2 + 6 H2O + ATP
What does the splitting of water allow to happen?
Hydrogen electrons are incorporated into sugar molecules
What is a redox reaction?
A chemical reaction that transfers electrons
Photosynthesis is a redox process where what is oxidized and what is reduced?
Water is oxidized and carbon dioxide is reduced
What occurs in the light reactions of photosynthesis?
Water is split, oxygen is released, NADP+ is reduced to NADPH, and ATP is generated from ADP by photophosphorylation
Where does photosynthesis occur?
Chloroplast
Where does the Calvin Cycle occur?
Stroma of the chloroplast
How does the Calvin Cycle begin?
Carbon fixation, incorporating CO2 into organic molecules
What do the light reactions convert?
Solar energy to the chemical energy of ATP and NADPH
What is the electromagnetic spectrum?
The entire range of electromagnetic energy or radiation
Photosynthesis is a series of what kind of reactions?
Anabolic
Cell respiration is a series of what kind of reactions?
Catabolic
Is photosynthesis aerobic?
No
Is cell respiration aerobic?
Yes
What does glucose get oxidized into in photosynthesis?
6CO2
What does 6O2 get reduced into in photosynthesis?
6H2O
What is Chlorophyll a?
Main photosynthetic (light capturing) pigment
What are accessory pigments?
Chlorophyll b and carotenoids which absorb light and transfer it downward to the primary pigment (chlorophyll a) reaction center
What does chlorophyll b do?
Broadens the spectrum used for photosynthesis
What do caretenoids do?
Absorb excessive light that would damage chlorophyll
What is a photosystem?
A cluster of pigments and proteins that work together to capture light energy
What do light harvesting complexes in photosystems do?
Funnel energy from photons into reaction center
Explain the first step of the light reactions
A photosystem consisting of a reaction-center complex surrounded by light-harvesting complexes is present
The light-harvesting complexes (pigment molecules bound to proteins) funnel the energy of photons to the reaction center
A primary electron acceptor in the reaction center accepts an excited electron from chlorophyll a
An electron from a chlorophyll molecule is transferred via solar power to the primary electron acceptor
How does linear electron flow during the light reactions generate ATP and NADPH?
The passing of an electron from the primary electron acceptor of photosystem 2 to photosystem 1 puts out ATP, and the addition of electrons to NADP+ reduce it into NADPH
Where are the photosystems located?
Embedded in the thylakoid membrane
What is the concentration of H+ ions in the thylakoid space compared to the stroma?
The thylakoid has a high concentration of H+ ions while the stroma has a low concentration of H+ ions
Where do the ATP and NADPH produced during the light-dependent reactions go when the process is complete?
The Calvin Cycle
How is the Calvin Cycle similar to the Citric Acid Cycle
It regenerates its starting material after molecules enter and leave the cycle
What does the Calvin Cycle build?
Sugar from smaller molecules by using ATP and the reducing power of electrons carried by NADPH
How is carbon converted during the Calvin Cycle?
It enters as CO2 and leaves as glyceraldehyde-3-phosphate (G3P)
How many times must the Calvin Cycle occur for net synthesis of 1 G3P?
3 times
What are the 3 phases of the Calvin Cycle?
-Carbon fixation (catalyzed by rubisco)
-Reduction
-Regeneration of the CO2 acceptor (RuBP)
What is photorespiration?
A respiratory process in many higher plants by which they take up oxygen in the light and give out some carbon dioxide, contrary to the general pattern of photosynthesis. (Oxygen is put into the Calvin Cycle rather than photosynthesis and CO2 is omitted without producing ATP or Sugar)
What does photorespiration limit?
Damaging products of light reactions that build up in the absence of the Calvin cycle
Why is photorespiration a problem for a plant?
It can drain as much as 50% of the carbon fixed by the Calvin Cycle
What is a C4 plant?
A plant in which the Calvin cycle is preceded by reactions that incorporate CO2 into a four-carbon compound, the end product of which supplies CO2 for the Calvin cycle ( Requires enzyme PEP carboxylase which has a higher affinity for CO2 than Rubisco, meaning it can fix CO2 even when CO2 concentrations are low)
When C4 plants go through photo respiration where are there 4 carbon compounds exported?
Bundle-sheath cells
What are CAM plants?
Plants that open their stomata during the night and close them during the day
What is fermentation?
A partial degradation of sugars that occurs without O2
What is aerobic respiration?
Consumes organic molecules and O2 and yields ATP
What is anaerobic respiration?
Consumes organic molecules and compounds other than oxygen and yields ATP
What does the transfer of electrons during chemical reactions do?
Release energy stored in organic molecules which is ultimately used to synthesize ATP
What is an electron donor called?
Reducing agent
What is an electron acceptor called?
Oxidizing agent
What becomes reduced in cell respiration?
Oxygen which forms CO2 and Water
What becomes oxidized in cell respiration?
"Fuel" (Glucose)
What are the 3 stages of cellular respiration?
-Glycolysis (breaks down glucose into two molecules of pyruvate)
-The citric acid cycle (completes the breakdown of glucose)
-Oxidative phosphorylation (accounts for most of the ATP synthesis)
What occurs in the link reaction?
Pyruvate loses a CO2 molecule and two hydrogens and becomes Acetate
Hydrogens accepted by NAD to form NADH.
Acetate combines with coenzyme A (CoA) to form acetyl CoA.
What accounts for almost 90% of the ATP generated by cellular respiration and where is the rest of the ATP formed?
Oxidative phosphorylation/smaller amount of ATP is formed in glycolysis and the citric acid cycle by substrate-level phosphorylation
What is glycolysis?
The breakdown of glucose into 2 molecules of pyruvate
What are the two major phases of glycolysis?
Energy investment phase and energy payoff phase
Where does glycolysis occur?
Cytoplasm
What is the net gain of glycolysis?
2 ATP, 2 NADH, 2 H2O, 2H+ ions, and 2 pyruvate molecules
Pyruvate enters the mitochondria only in the presence of what molecule?
Oxygen
What is pyruvate converted to before the citric acid cycle
Acetyl-CoA
What is produced in the link reaction?
2 NADH, 2 CO2, 2 Acetyl CoA
Where does the citric acid cycle take place?
Mitochondrial matrix
What compound is the final product of the electron transport chain?
Water
What molecule is phosphorylated during oxidative phosphorylation?
ADP
How many turns of the citric acid cycle occur for one glucose molecule?
2
Explain what occurs in the citric acid cycle
•The acetyl group of acetyl CoA joins the cycle by combining with oxaloacetate, forming citrate
•The next seven steps decompose the citrate back to oxaloacetate, making the process a cycle
•The NADH and FADH2 produced by the cycle relay electrons extracted from food to the electron transport chain
What is produced with one turn of the citric acid cycle?
1 ATP, 3 NADH, and 1 FADH2
What is lost in the citric acid cycle?
2 CO2
What does NADH and FADH2 donating their electrons to the electron transport chain power?
ATP synthesis via oxidative phosphorylation
Where does the electron transport chain occur?
Cristae of mitochondria
Explain what occurs in the electron transport chain
Electrons are passed through multiple integral proteins, making the carriers switch between their oxidized and reduced states, eventually being passed to oxygen to form water. Electron transfer in the electron transport chain causes proteins to pump H+ from the mitochondrial matrix to the intermembrane space. H+ then moves back across the membrane, passing through channels in ATP synthase which uses the exergonic flow of H+ to drive the phosphorylation of ATP
What does electron transfer in the electron transport chain cause?
Proteins to pump H+ from the mitochondrial matrix to the intermembrane space
What is the proton motive force?
The force provided by a transmembrane hydrogen ion gradient
How do chloroplasts and mitochondria generate ATP?
Chemiosmosis
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