Chapter 13 & 14: How Cells Obtain Energy From Food Flashcards

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1
Q

Stages for the breakdown of food molecules?

A

3 stages

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2
Q

Describe stage 1 of food breakdown

A
  • breakdown of large food molecules to simple subunits (proteins to amino acids, polysaccharides to simple sugars, fats to fatty acids glycerol)
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3
Q

Describe stage 2 of food breakdown

A
  • breakdown of simple subunits to acetyl CoA
  • limited amounts of ATP and NADH produced
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4
Q

Describe stage 3 of food breakdown

A
  • complete oxidation of the acetyl group in acetyl CoA to H2O and CO
  • large amounts of ATP produced on the inner mitochondrial membrane
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5
Q

Why do cells oxidize food in steps?

A
  • activation energy smaller, and they can store energy in activated carriers (ATP, NADH)
  • direct burning of sugar caues large activation energy overcome by the heat of fire, so all free energy released as heat(none stored)
  • small activation energies overcome by enzymes that work at body temperature, some free energy stored in activated carriers
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6
Q

Describe net result of oxidation of food molecules (redox rxn)

A

Food + O2 —-> ATP + NADH + CO2 + H2O

NADH activated carrier

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7
Q

redox reaction

A
  • process/reaction that involves transfer of electrons from one molecule to another
    -oxidation/reduction
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8
Q

OIL RIG

A
  • oxidation is loss of e-
  • example: glucose oxidized in food molecules
  • reduction is gain of e-
  • example: NAD –> NADH
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9
Q

Addition of electron

A
  • often accompanied by addition of H+
  • process called hydrogenation, so hydrogenation = reduction reaction
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10
Q

Dehydrogenation

A
  • these reactions or oxidation reactions, loss of e- and H+
  • energy released
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11
Q

Glucose food example: step 1

A
  • aerobic respiration
  • C6H12O6 +6O2 —> 6CO2 + 6H2O
  • glucose and oxygen creates energy (heat and chemical)
  • redox reaction: glucose oxidized, oxygen reduced (to water
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12
Q

Glucose food example: step 2

A
  • glycolysis
  • occurs in cytoplasm
  • anaerobic(no oxygen required)
  • makes small amounts of energy
  • net result: glucose —> 2 pyruvate + 2 ATP + 2 NADH

redox reactions, so taking up electrons and a proton at same time (NAD+ –> NADH)

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13
Q

Fermentation

A
  • NAD+ reformed when fermentation happens here
  • instead of creating pyruvate, it creates lactate
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14
Q

Mitochondria

A
  • dynamic in structure, location, and number
  • contains an outer membrane, intermembrane space, inner membrane, and two internal compartments
  • large internal space called the matrix
  • citric acid cycle within the matrix with NADH
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15
Q

What is the origin of mitochondria?

A
  • endosymbiosis
  • prokaryote engulfed by endocytosis by anerobic eukaryotic cell
  • one organism (endosymbiont) living inside of cell of another organism (host) for their mutual benefit
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16
Q

Glucose example (final) Step 3

A
  • citric acid cycle
  • electron transport
17
Q

Citric acid cycle

A
  • NADH carries electrons that are stripped off
  • one turn of the cycle produces 3 NADH, 1 GTP, and 1 FADH2
  • releases two molecules of CO2
  • uses lots of carbon in order for all 8 steps to happen
18
Q

Electron transport chain

A
  • high energy electrons are carried by NADH
  • high energy since thare held weakly, making them reactive
  • high energy electrons donated to electron transport chain complexes in the mitochondrial inner membrane
  • NADH oxidized back to NAD+
  • electrons held tigher and tighter down chain
  • final electron acceptor O2 when O2 is reduced to H2O
  • now electrons are lowest energy state
  • they are held tightly by the O2
19
Q

How does NADH transfer electrons to oxygen?

A
  • Through three large enzyme complexes embedded in the inner membrane
20
Q

Three large enzyme complex process to transfer electrons to oxygen from NADH explained

A

-High-energy electrons are transferred through three respiratory enzyme complexes in the inner mitochondrial membrane.
- During the transfer of electrons from NADH to oxygen, protons derived from water are pumped across the membrane from the matrix into the intermembrane space by each of the complexes
- Ubiquinone (Q) and cytochrome c (c) serve as mobile carriers that ferry electrons from one complex to the next.
- The three respiratory enzyme complexes associate to form a supercomplex that is thought to facilitate the passage of electrons.

21
Q

What can iron in a heme group provide?

A
  • can serve as an electron acceptor within three complexes of the electron transport chain
  • iron-sulfur centers also can carry electrons
22
Q

Chemiosmosis

A
  • accumulation of protons in the intermembrane spaces drives protons into the matrix via diffusion
  • membrane relatively impermeable to ions
  • most protons can only reenter matrix through ATP synthase(uses energy of gradient to make ATP from ADP and Pi

most cells obtain most energy by membrane-based mechanism(s), like mitochondria and chloroplasts

23
Q

Describe how ATP synthase uses energy stored in electrochemical proton gradient to produce ATP

A
  • ATP synthase converts mechanical energy (rotation of stalk) to chemical bond energy
  • ADP +Pi –> ATP
  • central stalk spins rapidly by electrochemical proton gradient
  • when stalk not fully connected, can produce reverse reaction
  • example of chemiosmosis
24
Q

What is uncoupling?

A
  • electron transport can be uncoupled from ATP synthesis
  • has H+ going out.in, O2 coverting to H2O in end
  • electron transport will run at max capacity to reestablish H+ gradient
25
Q

uncoupling proteins (UCPs)

A
  • made in brown fat-energy lost as heat
  • put holes in inner membrane, so H+ proton gradient is lost
  • so no ATP made
26
Q

Describe why mitochondria maintains a high ATP to ADP ratio in cells

A
  • carrier protein in the inner mitochondrial membrane exchanges ATP for ADP
  • molecules produced by ATP hydrolysis in the cytosol rapidly entemjtochondria for recharging
  • ATP molecules formed in mito matrix by oxidative phosphorylation are rapidly pumped into the cytosol where they are needed
  • ATP drives energetically unfavorable reactions, like a battery for an engine; if battery/mito blocked, ATP levels fall and battery runs down
  • can cause cell to do die
27
Q

Mitochondrial disease

A
  • mitchondrial defect is primary cause
  • defect in mito encoded genes
  • maternally inherited
  • defects in respiration in high respiring tissues, skeletal muscle, neurons
28
Q

Mitochondira involved in Neurodegenerative diseases

A
  • mitochondrial dysfunction secondary to disease process
  • alzheimer’s
    -parkinson’s
  • huntington’s
    multiple sclerosis

can be nuclear encoded mito genes or increases ROS

29
Q

How can Mitochondrial Respiration be measured?

A

Respirometry- O2 consumption inhibitors of the electron transport chain

roteonone and oligomycin

30
Q

Respiratory control

A
  • electrochemical proton gradient inhibits rate of electron transport
  • uncoupler can collapse the proton gradient, electron transport is free to run unchecked at the maximal rate
  • this increases the proton gradient, which inhibits electron transport