Ap Biology: Respiration and Photosynthesis, Ch 9 and 10
What is fermentation?
the 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 compounds other than O2 and yields ATP
Cell respiration includes both ____ and ____ respiration but is often used to refer to _____ respiration
aerobic, anaerobic, aerobic
What is the chemical formula for respiration?
C6H12O6 --> 6CO2 + 6H2O + Energy (ATP + heat)
transfer electrons between reactants; are called oxidation-reduction reactions
a substance loses electrons
a substance gains electrons
During respiration, the fuel (glucose) is ______ and O2 is _____
What are the three stages of cell respiration?
glycolysis, the citric acid cycle, and oxidative phosphorylation
what is glycolysis?
breaks down glucose into two molecules of pyruvate; occurs in the cytoplasm and has two major phases: energy investment and energy payoff
what is the citric acid cycle?
it completes the breakdown of glucose
what is oxidative phosphorylation
it accounts for most of the ATP synthesis
Why does oxidative phosphorylation generate the most ATP?
because it is powered by redox reactions.
What are the two phases of glycolysis?
Energy investment (glucose goes in, 2 ATP used --> 2 ADP + 2P) Energy payoff (4 ADP + 4P --> 4 ATP; 2 NAD+ + 4e- + 4H+ --> 2 NADH + 2 H+) NET: Glucose --> 2 Pyruvate + 2 H2O 4 ATP formed - 2 ATP used --> 2 ATP 2 NAD+ + 4 e- + 4 H+ --> 2 NADH + 2 H+
Before the citric acid cycle can begin, pyruvate must be converted to __________ which does what?
acetyl CoA, which links the cycle to glycolysis
Where does the citric acid cycle (Krebs cycle) take place?
in the mitochondrial matrix
where does glycolysis take place?
in the cytoplasm
The NADH and FADH2 produced by the citric acid cycle do what?
relay electrons extracted from food to the electron transport chain
following ____ and the ______ NADH and FADH2 account for most of the energy extracted from food
glycolysis, and the citric acid cycle
Where is the ETC located?
in the cristae of the mitochondrion
where are electrons transferred from to the ETC?
from NADH or FADH2
what generates no ATP?
what is the ETC's function?
to break the large free-energy drop from food to O2 into smaller steps that release energy in manageable amounts
what is chemiosis?
the use of energy in a H+ gradient to drive cellular work (electron transfer in the ETC causes proteins to pump H+ from the mitochondrial matrix to the intermembrane space. the H+ then moves back across the membrane, passing through channels in ATP synthase. ATP synthase uses the exergonic flow of H+ to drive phosphorylation of ATP)
what is the proton-motive force?
the H+ gradient is referred to as a proton-motive force, emphasizing its capacity to do work
what does the energy stored in a H+ gradient do?
couples the redox reactions of the ETC to ATP synthesis
During cellular respiration, most energy flows in this sequence:
glucose -> NADH -> ETC -> proton-motive force -> ATP
what % of energy in a glucose molecule is transferred to ATP during cell respiration? How many ATPs are made?
40%; 38 ATP are made
Most cellular respiration requires O2 to produce ATP; what process can produce ATP with or without O2?
in the absense of O2, glycolysis couples with what to produce ATP?
couples with fermentation or anaerobic respiration to produce ATP
Anaerobic respiration uses what with the ETC?
electron acceptor other than O2 (ie sulfate)
Fermentation uses ___________ instead of an __________ to generate ATP.
Fermentation consists of _______ plus reactions that regenerate _____ which can be reused by __________.
glycolysis, NAD+, glycolysis
What are the two common types of fermentation?
alcohol and lactic acid
In alcohol fermentation what happens?
pyruvate is converted to ethanol in two steps, with the first releasing CO2
In lactic acid fermentation, what happens?
pyruvate is reduced to NADH, forming lactate as an end product, with no release of CO2
Human muscle cells use _____________ to generate ATP when O2 is scarce
lactic acid fermentation
What are similarities between fermentation and aerobic respiration?
1. both use glycolysis to oxidize glucose and other organic fuels to pyruvate.
What are differences between fermentation and aerobic respiration?
1. they use different final electron acceptors - an organic molecule (such as pyruvate or acetaldehyde) in fermentation - O2 in cellular respiration 2. Amount of ATP produced: - Cell respiration produces 38 ATP per glucose molecule - fermentation produces 2 ATP per glucose molecule
What are obligate anaerobes?
they carry out fermentation or anaerobic respiration and cannot survive in the presence of O2
what are facultative anaerobes?
means that they can survive using either fermentation or cellular respiration (yeast and many bacteria)
What probably evolved in ancient prokaryotes before there was oxygen in the atmosphere?
What are major intersection to various catabolic and anabolic pathways?
gycolysis and the citric acid cycle
Glycolysis accepts a wide range of _______
catabolic pathways funnel electrons from many kinds of organic molecules into what?
proteins must be digested to what? These groups can do what?
amino acids; amino groups can feed glycolysis or the citric acid cycle
Fats are digested to what system? what are they used for? where?
glycerol (used in glycolysis) and fatty acids (used in generating acetyl CoA)
Fatty acids are broken down by what? what do they yield?
broken down by beta oxidation, yield acetyl CoA
An oxidized gram of fat produces more than ______ as much ATP as an oxidized gram of ________
What is the most common mechanism for control?
When does respiration slow down? (regarding ATP concentration)
if ATP concentration begins to drop, respiration speeds up; when there is plenty of ATP, respiration slows down
Control of catabolism is based mainly on what?
regulating the activity of enzymes at strategic points in the catabolic pathway.
What is the term for metabolic pathways that release stored energy by breaking down complex molecules?
when a glucose molecule loses a hydrogen atom as the result of an oxidation-reduction reaction, the molecules becomes________
Where does glycolysis take place?
the ATP made during glycolysis is generated by ______
Which process in eukaryotic cells will proceed normally whether oxygen (O2) is present or absent?
Why are carbohydrates and fats considered high energy foods?
they can have very long carbon skeletons
In addition to ATP, what are the end products of glycolysis?
NADH and pyruvate
Starting with one molecule of glucose, the "net" products of glycolysis are
2 NADH, 2 H+, 2 pyruvate, 2 ATP, and 2 H2O
a molecule that is phosphorylated has ___________________
has an increased chemical reactivity; it is primed to do cellular work
Which of the following intermediary metabolites enters the citric acid cycle and is formed, in part, by the removal of a carbon (CO2) from one molecule of pyruvate?
During cellular respiration, acetyl CoA accumulates in which location?
Carbon dioxide (CO2) is released during which of the following stages of cell. respiration?
oxidation of pyruvate to acetyl CoA and the citric acid cycle
Cellular respiration harvests the most chemical energy from which of the following?
Where are the proteins of teh electron transport chain located?
mitochondrial inner membrane
the primary role of oxygen in cellular respiration is to ________
act as an acceptor for electrons and hydrogen, forming water
During oxidative phosphorylation, H2O is formed. Where does the oxygen for the synthesis of the water come from?
molecular oxygen (O2)
When hydrogen ions are pumped from the mitochondrial matrix across the inner membrane and into the inter-membrane space, the result is _______
creation of a proton gradient
Where is ATP synthase located in the mitochondrion?
Which of the following produces the most ATP when glucose (C6H12O6) is completely oxidized to carbon dioxide (CO2) and water?
oxidative phosphorylation (chemiosmosis) AKA the electron transport chain
In liver cells, the inner mitochondrial membranes are about 5X the area of the outer mitochondrial membranes, and about 17 X that of the cell's plasma membrane. What purpose must this serve?
it increases the surface for oxidative phosphorylation
Which of the following normally occurs whether or not oxygen is present?
Light energy absorbed by chlorophyll drives what?
synthesis of organic molecules in the chloroplast
CO2 enters and O2 exits the leaf through the _____
What is the mesophyll?
the interior tissue of the leaf
How many chloroplasts does the typical mesophyll cell have?
What is the equation for photosynthesis?
6 CO2 + 12 H2O + Light energy --> C6H12O6 + 6 O2 + 6 H2O
Photosynthesis is the redox process in which what is oxidized and what is reduced?
H2O is oxidized and CO2 is reduced
What occurs during the light reactions?
Split H2O, release O2, Reduce NADP+ to NADPH, generate ATP from ADP by photophosphorylation
What is the photo part of photosynthesis?
the light reactions
What is the synthesis part of photosynthesis?
the Calvin cycle
What occurs during the Calvin Cycle?
forms sugar from CO2 (using ATP and NADPH)
Where is the Calvin cycle (photosynthesis)?
in the stroma
Where do the light reactions occur?
in the thylakoids
What is photophosphorylation?
generates ATP from ADP
What does the Calcin cycle begin with? (photo)
carbon fixation (incorporating CO2 into organic molecules)
What is carbon fixation?
incorporating CO2 into organic molecules
What does wavelength determine? (photo)
determines the type of electromagnetic energy
What is the electromagnetic spectrum?
range of electromagnetic energy, or radiation
What are pigments?
substances that absorb visible light (different pigments absorb different wavelengths)
Does chlorophyll reflect or absorb green light?
it reflects and transmits green light
What is an absorption spectrum?
a graph plotting a pigment's light absorption versus wavelength
What is an action spectrum?
profiles the relative effectiveness of different wavelengths of radiation in driving a process
Who first demonstrated an action spectrum?
Theodore W. Engelmann
What did Engelmann do?
exposed different segments of a filamentous alga to different wavelengths - found that areas receiving wavelengths favorable to photosynthesis produced excess O2, growth of aerobic bacteria clustered along the alga as a measure of O2 production
What is the main photosynthetic pigment?
What does chlorophyll b do?
broaden the spectrums used for photosynthesis
What do carotenoids do?
absorb excessive light taht would damage chlorophyll (orange)
What is the reaction-center complex?
a type of protein complex, surrounded by light-harvesting complexes
What are light-harvesting complexes?
pigment molecules bound to proteins, funnel the energy of photons to the reaction center
What is the primary electron acceptor? Where is it?
accepts an excited electron from chlorophyll a (transfer of an electron from a chlorophyll a molecule to the primary electron acceptor is the first step of the light reactions); in the reaction center
What wavelength is Photosystem II best at absorbing? What is the reaction-center called?
best at absorbing a wavelength of 680 nm; reaction-center is called P680
What wavelength is Photosystem I best at absorbing? What is the reaction-center called?
best at absorbing at 700 nm; reaction-center is called P700
What is linear electron flow?
the primary pathway for electron flow, involves both photosystems (II and I); produces ATP and NADPH using light energy
Explain the steps of linear electron flow.
1. a photon hits a pigment, energy is passed among pigment molecules until it excites P680 (PS II) 2. excited electrons from P680 is transferred to the primary electron acceptor (P680+ [P680 that is missing an electron] is a very strong oxidizing agent) 3. H2O is split by enzymes 4. Electrons are transferred from the hydrogen atoms to P680+ thus reducing it to P680 5. O2 is released as a by-product 6. Each electrons "falls" down an ETC from the primary electron acceptor of PS II to PS I 7. Energy released by the fall drives the creation of a proton gradient across the thylakoid membrane 8. diffusion of H+ (protons) across the membrane drives ATP synthesis 9. PS I - loses an electron to an electron acceptor. P700+ accepts an electron passed down from PS II via the ETC 10. Each electron "falls" down an ETC from the primary electron acceptor of PS I to the protein ferredoxin (Fd) 11. The electrons are transferred to NADP+ and reduce it to NADPH
What occurs during PS I? (linear electron flow)
transferred light energy excites P700, loses an electron to an electron acceptor; P700+ (missing an electron) accepts an electron passed down from PS II via the ETC
What is unique about the cyclic electron flow?
uses only PS I, produces ATP but no NADPH, generates surplus ATP for the Calvin cycle, thought to have evolved before linear electron flow, may protect cells from light-induced damage
What are the similarities between the chemiosmosis in chloroplasts versus in mitochondria?
they both: - generate ATP by chemiosmosis
What are the similarities between the chemiosmosis in chloroplasts versus in mitochondria?
They have different sources of energy (Mitochondria transfer chemical energy from FOOD to ATP ..... Chloroplasts transform LIGHT ENERGY into ATP)
what do mitochondria and chloroplasts use to transfer to ATP?
mitochondria transfer chemical energy from FOOD to ATP. Chloroplasts transform LIGHT ENERGY into ATP
What about the the spatial organization between chemiosmosis in the mitochondria and in chloroplasts is different?
mitochondria: protons are pumped to the INTERMEMBRANE SPACE; drive ATP synthesis as they diffuse back into the MITOCHONDRIAL MATRIX
chloroplasts: protons are pumped into the THYLAKOID SPACE; drive ATP synthesis as they diffuse back into the STROMA
the Calvin cycle uses ____ and ____ to convert CO2 to _____
ATP and NADPH to convert CO2 to sugar
Describe the Calvin Cycle in photosynthesis
it regenerates its starting material after molecules eneter and leave the cycle, builds sugar from smaller molecules (using ATP from teh reducing power of electrons carried by NADPH); Carbon enters at CO2 and leaves as G3P (glyceraldehyde-3-phospate)
for 1 G3P how many times must the calvin cycle take place?
3 times, fixing 3 molecules of CO2
What are the three phases of the Calvin cycle? (photo)
carbon fixation (catalyzed by rubisco); reduction; regeneration of the CO2 acceptor (RuBP)
What are the alternative mechanisms of carbon fixation in hot, arid climates?
plants close stomata, to conserve H2O (because dehydration is a problem), but photosynthesis is limited (reduces access to CO2 and causes O2 to build up); favors photorespiration
What is photorespiration?
consumes O2 and organic fuel and releases CO2 without producing ATP or sugar
What happens in photorespiration?
rubisco adds O2 instead of CO2 in the Calvin cycle
What are the problems with photorespiration? advantages?
problem: can drain up to 50% of the carbon fixed by the Calvin cycle advantage: limits damaging products of light reactions that build up in the absence of the Calvin cycle
What are C3 plants?
initial fixation of CO2, via rubisco forms a three-carbon compound
What are C4 plants?
they minimize photorespiration; incorporate CO2 into four-carbon compounds in MESOPHYLL cells; requires the enzyme PEP carboxylase; PEP carboxylase has a higher affinity for CO2 than rubisco does (can fix CO2 even when CO2 concentrations are low); four-carbon compounds are exported to BUNDLE-SHEATH cells, where they release CO2 that is then used in the Calvin cycle
What is unique to C4 leaves?
the bundle-shealth cells
What are CAM plants?
crassulacean acid metabolism; open their stomata at night, incorporating CO2 into organic acids, Stomata close during the day, CO2 is released from organic acids and used in the Calvin cycle (ex. Pineapple)
Describe the structure of a chloroplast.
Describe the relationship between an action spectrum and an absorption spectrum.
Trace hte movement of electrons in linear electron flow.
Trace hte movement of electrons in cyclic electron flow
Describe the similarities and differences between oxidative phosphorylation in mitochondria vs photophosphorylation in chloroplasts
Describe the role of ATP and NADPH in the Calvin cycle.
Describe the major consequences of photorespiration
Describe two important photosynthetic adaptations that minimize photorespiration