Chapter 9-10
Biology 150l.3 with Holloway at Massachuetts College of Pharmacy & Health Sciences
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•Living cells require...
energy from outside sources
•Energy flow in the ecosystem:
Light --> Heat
photosynthesis
CO2 + H20 --> O2 + molecules (glucose)
fermentation
a partial degradation of sugars that occurs without O2
Aerobic respiration
consumes organic molecules and O2 and yields ATP
anaerobic respiration
similar to aerobic respiration but consumes compounds other than O2
cellular respiration with glucose
glucose + O2 --> CO2 + H20 + energy
redox reaction
redox reactions
The transfer of electrons during chemical reactions; releases energy stored in organic molecules
Called oxidation-reduction reactions - redox
oxidation and reduction
oxidation
substance loses electrons – increase (+) charge
reduction
substance gains electrons - increase in (-) charge
During cellular respiration, the fuel (such as glucose) is _____1_____, and O2 is _____2______
1) oxidized
2) reduced
In cellular respiration, electrons from organic compounds are usually first transferred to...
NAD+
NAD+
Coenzyme derived from Niacin (Vitamin B3)
functions as an oxidizing agent (accepts electrons)
NADH
reduced form of NAD+
represents stored energy
passes electrons to the ETC
electron transport chain (ETC)
Series of protein complexes – based on electronegativity
O2 pulls electrons down the chain in an “energy-yielding tumble”
Stages of cellular respiration
Glycolysis
The Citric acid cycle
Oxidative phosphorylation (ETC)
Stage: Glycolysis
glucose --> pyruvate
occurs in cytosol
Stage: citric acid cycle
pyruvate --> CO2
Occurs in mitochondrial matrix
Stage: Oxidative phosphorylation (ETC)
energy --> ATP
Occurs in inner mitochondrial membrane
Glucose = ?Kcal/mol (~?ATP)
686 Kcal/mol
~ 38 ATP
90 % of ATP is made by...
the ETC
most by oxidative phosphorylation because it is powered by redox reactions
_________ make ATP
Enzymes
Kinase enzymes
family of enzymes
function: movement of phosphate groups from one compound to the next
Glycolysis
probably evolved in ancient prokaryotes before there was oxygen in the atmosphere
–Evidence: location in the cytosol
Glucose (6 Carbon) split into two molecules of pyruvate (3 Carbon)
Glycolysis occurs in the cytoplasm and has two major phases (Energy investment phase & Energy payoff phase)
Energy Investment Phase of Glycolysis
steps 1-3
2 ATP
Energy Payoff Phase of Glycolysis
steps 4-10
2 ATP, 2 NADH, 2 pyruvates
In the citric acid cycle, _____1_____ must be converted to _____2______ as it enters a mitochondrion
1) pyruvate
2) acetyl CoA
Citric Acid Cycle
takes place in the mitochondrial matrix
(1) Carboxyl group removed; CO2
(2) Resulting 2 carbon molecule oxidized; electron à NAD+ (acetate)
(3) CoEnzyme A (CoA) attached --> acetyl CoA
The NADH and FADH2 produced by the ________ relay electrons extracted from food
citric acid cycle
Oxidative phosphorylation
NADH and FADH2 donate electrons to the electron transport chain – powers ATP synthesis - redox reactions
Electron Transport Chain
Found in the inner membrane of the mitochondrion
Components are proteins, which exist in 4 multiprotein complexes
Pumping protons to intermembrane space
Divides the large free-energy drop from glucose to O2 into smaller steps that release energy
Components are proteins, which exist in 4 multiprotein complexes
Pumping protons to intermembrane space
Divides the large free-energy drop from glucose to O2 into smaller steps that release energy
In the electron transport chain, electrons drop in ______1______ as they go down the chain and are finally passed to ____2_____, forming ______3_____
1) free energy
2) O2
3) H2O
2) O2
3) H2O
The 4 (I- IV) multi-protein complexes in the ETC are composed of...
catalytic enzymes
The only non protein component of the ETC is...
Ubiquinone (coenzyme Q)
True/False, the ETC produces ATP
FALSE
In the ETC, electrons are passed through...
a series of cytochromes (family of enzymes that contain Fe)
While the ETC does not produce ATP, it liberates about how much by dividing the free energy drop?
~ 50Kcal/mol
Chemiosmosis
the use of energy in a H+ gradient to drive cellular work
After the energy is liberated by the electron transport chain, the H+ moves...
back across the membrane, passing through channels in a protein complex
After the H+ moves back across the membrane, what happens?
ATP synthase uses the exergonic flow of H+ to Drive ATP synthesis and Phosphylate ADP
After ATP synthase uses the exergonic flow of H+, what happens?
Energy stored in a H+ gradient couples the redox reactions of the electron transport chain to ATP synthesis
About 40% of the energy in a glucose molecule is transferred to ATP during _____1______, making about ______2________ (how much energy)
1) cellular respiration
2) 38 ATP - 686 Kcal/mol
2) 38 ATP - 686 Kcal/mol
During cellular respiration, most energy flows in this sequence:
Glu --> NADH(FADH2) --> ETC --> pump H+ --> ATP
Most cellular respiration requires _______ to produce ATP
O2
__________ can produce ATP with or without O2
Glycolysis
In the absence of O2, glycolysis couples with:
Anaerobic respiration
Anaerobic respiration uses...
an electron transport chain with an electron acceptor other than O2
–Sulfate --> H2S
–Nitrate --> NO2 (Nitrite)
–Sulfate --> H2S
–Nitrate --> NO2 (Nitrite)
Fermentation
Uses phosphorylation instead of an electron transport chain to generate ATP
Supplies reactions that regenerate NAD+ from NADH
Alcohol or Lactic Acid
Supplies reactions that regenerate NAD+ from NADH
Alcohol or Lactic Acid
Alcohol Fermentation
Glycolysis creates pyruvate which is converted to ethanol in 2 steps:
1) release CO2
2) oxidize NADH
1) release CO2
2) oxidize NADH
Lactic acid fermentation
Pyruvate is reduced directly by NADH which forms lactate as an end product and no CO2 waste
Human muscle cells use ___________ to generate ATP when O2 is scarce
lactic acid fermentation
Fermentation Vs Aerobic Respiration
Both use glycolysis to oxidize glucose to pyruvate
The processes have different final electron acceptors:
•Fermentation: organic molecule (such as pyruvate or acetaldehyde)
•Cellular respiration: O2
Cellular respiration produces 38 ATP per glucose molecule; fermentation produces 2 ATP per glucose molecule ~ 20x more efficient
The processes have different final electron acceptors:
•Fermentation: organic molecule (such as pyruvate or acetaldehyde)
•Cellular respiration: O2
Cellular respiration produces 38 ATP per glucose molecule; fermentation produces 2 ATP per glucose molecule ~ 20x more efficient
Obligate anaerobes:
cannot survive in the presence of O2
Facultative anaerobes:
can survive using either fermentation or cellular respiration
Catabolic versatility:
Catabolic pathways funnel electrons from many kinds of organic molecules into cellular respiration
Glycolysis accepts a wide range of carbohydrates
Fats broken down to glycerol and fatty acid chains; broken down further by Beta Oxidation
Proteins must be digested to amino acids; amino groups removed
Glycolysis accepts a wide range of carbohydrates
Fats broken down to glycerol and fatty acid chains; broken down further by Beta Oxidation
Proteins must be digested to amino acids; amino groups removed
T/F Most chemical processes in a cell are reversible
TRUE
Control is based mainly on...
regulating the activity of enzymes at strategic points in the catabolic pathway
Photosynthesis
Converts light energy to chemical energy –Endergonic process
Reverses the direction of electron flow compared to respiration
–Water is split, electrons added to glucose, O2 released as waste
Photosynthesis is a redox process in which H2O is oxidized and CO2 is reduced
Reverses the direction of electron flow compared to respiration
–Water is split, electrons added to glucose, O2 released as waste
Photosynthesis is a redox process in which H2O is oxidized and CO2 is reduced
2 stages of photosynthesis
The light reactions (in the thylakoids)
– Split H2O, Release O2
– Reduce NADP+ to NADPH
– Generate ATP from ADP by photophosphorylation
The Calvin cycle (in the stroma) forms sugar from CO2, using ATP and NADPH
- begins with carbon fixation, incorporating CO2 into organic molecules
– Split H2O, Release O2
– Reduce NADP+ to NADPH
– Generate ATP from ADP by photophosphorylation
The Calvin cycle (in the stroma) forms sugar from CO2, using ATP and NADPH
- begins with carbon fixation, incorporating CO2 into organic molecules
Chlorophyll absorbs light best in the _______ & __________ spectra
blue-violet and red
Carotenoids
Accessory pigments that absorb excessive light that would damage chlorophyll – yellow or orange
Photosystem
Consists of a reaction-center complex
The light-harvesting complexes transfer the energy of photons to the reaction center
Energy released by the ETC creates a proton gradient across the thylakoid membrane
–Drives ATP synthesis
The light-harvesting complexes transfer the energy of photons to the reaction center
Energy released by the ETC creates a proton gradient across the thylakoid membrane
–Drives ATP synthesis
reaction center complex
Specialized chlorophyll molecules accept electrons
Chemiosmosis: Chloroplasts vs. Mitochondria
In mitochondria, protons are pumped to the intermembrane space and drive ATP synthesis as they diffuse back into the mitochondrial matrix
In chloroplasts, protons are pumped into the thylakoid space and drive ATP synthesis as they diffuse back into the stroma
In chloroplasts, protons are pumped into the thylakoid space and drive ATP synthesis as they diffuse back into the stroma
Calvin Cycle
The cycle builds sugar from smaller molecules
Uses ATP and electrons carried by NADPH
Carbon enters the cycle as CO2 and leaves as a sugar named glyceraldehyde 3-phospate (G3P)
Uses ATP and electrons carried by NADPH
Carbon enters the cycle as CO2 and leaves as a sugar named glyceraldehyde 3-phospate (G3P)
For net synthesis of 1 G3P, the calvin cycle must take place...
three times, fixing 3 molecules of CO2
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Naj
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