Chapter 13 & 14: How Cells Obtain Energy From Food Flashcards
Stages for the breakdown of food molecules?
3 stages
Describe stage 1 of food breakdown
- breakdown of large food molecules to simple subunits (proteins to amino acids, polysaccharides to simple sugars, fats to fatty acids glycerol)
Describe stage 2 of food breakdown
- breakdown of simple subunits to acetyl CoA
- limited amounts of ATP and NADH produced
Describe stage 3 of food breakdown
- complete oxidation of the acetyl group in acetyl CoA to H2O and CO
- large amounts of ATP produced on the inner mitochondrial membrane
Why do cells oxidize food in steps?
- 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
Describe net result of oxidation of food molecules (redox rxn)
Food + O2 —-> ATP + NADH + CO2 + H2O
NADH activated carrier
redox reaction
- process/reaction that involves transfer of electrons from one molecule to another
-oxidation/reduction
OIL RIG
- oxidation is loss of e-
- example: glucose oxidized in food molecules
- reduction is gain of e-
- example: NAD –> NADH
Addition of electron
- often accompanied by addition of H+
- process called hydrogenation, so hydrogenation = reduction reaction
Dehydrogenation
- these reactions or oxidation reactions, loss of e- and H+
- energy released
Glucose food example: step 1
- aerobic respiration
- C6H12O6 +6O2 —> 6CO2 + 6H2O
- glucose and oxygen creates energy (heat and chemical)
- redox reaction: glucose oxidized, oxygen reduced (to water
Glucose food example: step 2
- 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)
Fermentation
- NAD+ reformed when fermentation happens here
- instead of creating pyruvate, it creates lactate
Mitochondria
- 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
What is the origin of mitochondria?
- endosymbiosis
- prokaryote engulfed by endocytosis by anerobic eukaryotic cell
- one organism (endosymbiont) living inside of cell of another organism (host) for their mutual benefit
Glucose example (final) Step 3
- citric acid cycle
- electron transport
Citric acid cycle
- 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
Electron transport chain
- 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
How does NADH transfer electrons to oxygen?
- Through three large enzyme complexes embedded in the inner membrane
Three large enzyme complex process to transfer electrons to oxygen from NADH explained
-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.
What can iron in a heme group provide?
- can serve as an electron acceptor within three complexes of the electron transport chain
- iron-sulfur centers also can carry electrons
Chemiosmosis
- 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
Describe how ATP synthase uses energy stored in electrochemical proton gradient to produce ATP
- 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
What is uncoupling?
- 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
