L13. Obtaining Energy from Food Flashcards

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1
Q

direct burning in a nonliving system vs stepwise oxidation - direct burning

A
  • large activation energy is overcome by the heat from a fire
  • all the free energy is released as heat (none is stored)
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2
Q

direct burning in a nonliving system vs stepwise oxidation - stepwise oxidation

A
  • also cellular respiration
  • small activation energies are overcome by enzymes that work at body temperature
  • some of the free energy is stored in activated carrier molecules
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3
Q

how are the activated carriers ATP and NADH are used

A
  • the energy from food breakdown (oxidation and favorable) is transferred to ATP and NADH
  • the energy from ATP is then coupled with ATP synthesis
  • energy from other carriers drive oxidative phosphorylation
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4
Q

what is oxidative phophorylation

A
  • takes place in inner mitochondrial membrane
  • it is when the cell uses energy from activated carriers to drive ATP production
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5
Q

what are the three stages to breaking down food molecules

A
  1. mouth, gut, and lysozymes
  2. cytosol
  3. mitochondria
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6
Q

three stages to breaking down food molecules - mouth, gut, and lysozymes

A

large macromolecules are digested and converted into simple monomers via enzymes

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7
Q

three stages to breaking down food molecules - cytosol

A
  • glucose enters via glucose/Na+ symporter
  • gradual oxidation breakdown of simple monomers via glycolysis
  • glycolysis takes 1 glucose and converts it into 2 pyruvates
  • also produces ATP and NADH
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8
Q

three stages to breaking down food molecules - mitochondria

A
  • pyruvate enters the mitochondria matrix and is converted into Acetyl CoA
  • acetyl CoA then goes into the citric acid cycle and this makes a large amount of NADH
  • electrons from NADH is passed to the electron transport chain
  • this causes oxidative phosphorylation to begin, producing a large amount of ATP
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9
Q

explain the location of the reactions for aerobic respiration

A
  • glycolysis: cytosol
  • citric acid cycle and oxidative phosphorylation: mitochondria
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10
Q

three stages to breaking down food molecules: cytosol - explain ATP and NADH in glycolysis

A
  • 2 ATP is required and produces 4 ATP with a net ATP of 2
  • also produces 2 NADH
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11
Q

three stages to breaking down food molecules: cytosol - glycolysis in absence of O2

A

products are ethanol or lactic acid fermentation

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12
Q

three stages to breaking down food molecules: cytosol - glycolysis in presence of O2

A

pyruvate goes to mitochondria

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13
Q

three stages to breaking down food molecules: cytosol - how does glycolysis initiate the breakdown of sugars

A
  • the breakdown of glucose provides energy for ATP synthesis from ADP and Pi
  • during ATP synthesis, substrate-level phosphorylation occurs
  • NADH electron is then donated to the electron transport chain (for aerobic organisms)
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14
Q

three stages to breaking down food molecules: cytosol - substrate level phosphorylation

A

Pi is transferred from substrate molecules (sugar intermediates) to ADP

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15
Q

three stages to breaking down food molecules: cytosol - explain NAD+

A
  • an intermediate in catabolic reactions that generate ATP through the oxidation of food molecules
  • it is an oxidizing agent (takes e-)
  • kept high in the cell
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16
Q

three stages to breaking down food molecules: cytosol - NADPH

A
  • operates with enzymes that catalyze anabolic pathways
  • it is a reducing agent (gives e-)
  • kept low in the cell
17
Q

three stages to breaking down food molecules: cytosol - anaerobic metabolism

A
  • anaerobic organisms use glycolysis
  • pyruvate and NADH remain in the cytosol
  • after glycolysis, fermentation begins
  • NADH will give up an electron to be turned into NAD+
18
Q

three stages to breaking down food molecules: cytosol - define fermentation

A

energy-yielding pathways that break down sugar in absence of O2

19
Q

three stages to breaking down food molecules: anaerobic metabolism - what does pyruvate convert to after fermentation

A
  • muscle cells: lactate
  • yeast: ethanol and CO2
20
Q

three stages to breaking down food molecules: cytosol - explain how reactions are coupled for glycolysis

A
  • during step 6: an energetically favorable C-H bond is oxidized and it drives the unfavorable NADH synthesis and the formation of a high-energy phosphate bond
  • during step 7: an energetically favorable hydrolysis of the phosphate bond drives ATP synthesis
21
Q

three stages to breaking down food molecules: cytosol - explain the ΔG° for ATP formation to be coupled

A

since the transfer of Pi is favorable, the ΔG° for hydrolysis of the phosphate bond must be more negative for the donor than the acceptor

22
Q

three stages to breaking down food molecules: cytosol - what is gluconeogenesis

A
  • it makes glucose from pyruvate (opposite of glycolysis)
  • it is costly and anabolic
  • uses many of the same enzymes as glycolysis but uses specific enzymes to bypass the three irreversible steps in glycolysis
23
Q

three stages to breaking down food molecules: cytosol - example of an enzyme in gluconeogenesis

A
  • phosphofructokinase
  • it is allosterically regulated
  • activated by ADP, AMP, and Pi
  • and inhibited by ATP
24
Q

three stages to breaking down food molecules: mitochondria - explain the pyruvate dehydrogenase complex

A

converts pyruvate to acetyl CoA and CO2

25
Q

three stages to breaking down food molecules: mitochondria - explain how fatty acids are converted to acetyl CoA

A
  • lipases cleave the bonds that link fatty acids to glycerol
  • the fatty acids are then coupled to coenzyme A
  • fatty acyl CoA is then oxidized in a four-enzyme cycle, generating one molecule of acetyl CoA and one each of NADH and FADH2
26
Q

three stages to breaking down food molecules: mitochondria - explain the citric acid cycle

A
  • it does not use O2 but it requires it for the turnover of NADH to NAD+ (keeps electron transport chain running)
  • it completely oxidizes carbon atoms from acetyl CoA to CO2
27
Q

three stages to breaking down food molecules: mitochondria - explain GTP and FADH

A
  • produced from the citric acid cycle
  • they are both activated carriers (donates electrons)
  • they have high-energy electrons stored and it can be used to produce ATP via oxidative phosphorylation (the only step that directly requires O2)
28
Q

three stages to breaking down food molecules: mitochondria - explain the process of oxidative phosphorylation

A
  • NADH and FADH2 transfers electrons to the electron transport chain via electron carriers embedded in the inner mitochondrial matrix
  • in the chain, the energy released will be used to drive H+ efflux across the inner membrane
  • this creates a gradient and will be used to ATP synthesis (ADP phosphorylation)
  • electrons are added to O2 and it will be combined with H+ to generate H2O
  • creates more ATP than glycolysis