Ch7 - Cellular respiration and fermentation

Question 1

Main purpose of cellular respiration

Answer 1

• make ATP and NADH
• mostly uses glucose but other organic molecules are also used

Question 2

4 steps of glucose metabolism

Answer 2

1. glycolysis
2. breakdown of pyruvate
3. citric acid cycle
4. oxidative phosphorylation

Question 3

Glycolysis

Answer 3

• step 1 of cellular respiration
• can occur with or without oxygen
• happens in the cytosol
• nearly identical in all living species
• has ten steps that occur in three phases
  
  1. energy investment
  2. cleavage
  3. energy liberation

Question 4

energy investment

Answer 4

• first phase in glycolysis
• steps 1-3
• 2 ATP hydrolyzed to create fructose-1,6-biphsophate

Question 5

cleavage

Answer 5

• second phase of glycolysis
• steps 4-5
• 6 carbon molecules broken into two 3 carbon molecules of glyceraldehyde-3-phosphate

Question 6

energy liberation

Answer 6

• third phase of glycolysis
• steps 6-10
• two glyceraldehyde-3-phosphates broken into two pyruvate molecues
• produces 2 NADH and 4 ATP
• net ATP is 2 (cuz two invested in investment phase)

Question 7

Warburg effect

Answer 7

• cancer cells preferentially use glycolysis while decreasing oxidative phosphorylation
• healthy cells generate most ATP from oxidative phosphorylation
• this is because tumors aren’t usually vascularized, so they aren’t getting enough oxygen to do oxidative phosphorylation
• used to diagnose cancers in PET scans

Question 8

Breakdown of pyruvate

Answer 8

• stage 2 in cellular respiration
• pyruvate is transported to mitochondrial matrix (in Eukaryotes)
• molecule of CO2 removed from each phosphate
• remaining acetyl group attached to CoA to make acetyl CoA
• yield: 1 NADH per pyruvate

Question 9

how is pyruvate brought into the mitochondria

Answer 9

• transported from cytosol to mitochondrial matrix via symporter
• brings in H+ and pyruvate at the same time

Question 10

pyruvate dehydrogenase

Answer 10

• enzyme that breaks down (oxidizes) pyruvate once in the mitochondrial matrix

Question 11

Citric Acid Cycle (Krebs cycle)

Answer 11

• stage 3 of cellular respiration
• breakdown of carbohydrates to CO2
• acetyle is removed from Acetyl COA and attached to oxaloacetate
  
  • forms citrate (citric acid)
• 8 steps release 2 CO2, 1 ATP, 3NADH, and 1 FADH2
• oxaloacetate is regenerated

Question 12

8 molecules in citric acid cycle (one for each step)

Answer 12

1. citrate (6C)
2. isocitrate (6C)
3. ketoglutarate (5C)
   
   • Co2 is byproduct of formation
4. succinyl-CoA (4C)
   
   • Co2 is byproduct of formation
5. succinate (4C)
6. Fumarate (4C)
7. malate (4C)
8. oxaloacetate (4C)
   can I keep selling stuff for money, officer?

Question 13

Oxidative phosphorylation

Answer 13

• stage 4 of cellular respiration
• high energy electrons removed from NADH and FADH2 to make ATP via electron transport chain
• Typically requires oxygen
• phosphorylation occurs at ATP synthase to make ATP

Question 14

Oxidation by electron transport chain (ETC)

Answer 14

• involves proteins and small organic molecules embedded in the inner mitochondrial membrane
• series of redox reactions accept and donate elections in a linear manner
• each movement of electrons punts H+ against the electrochemical gradient
  
  • the buildup of electrons provides the energy to make ATP
• FADH2 produces less usable energy because it skips a pump

Question 15

chemiosmosis

Answer 15

• chemical synthesis of ATP as a result of pushing H+ across a membrane

Question 16

ATP synthase

Answer 16

• protons can only pass through the inner mitochondrial membrane through ATP synthase
• uses free energy from protons passing through to phosphorylize ADP into ATP

Question 17

maximal amount of ATP from NADH

Answer 17

• yield = 30-34 ATP molecules per glucose
• maximal amount is rarely achieved
  
  • NADH also used in anabolic pathways
  • H+ gradient used for other purposes
    ex: pyruvate gets into the mitochondria via symport with H+, so those hydrogens can’t be used to make ATP

Question 18

ATP synthase

Answer 18

• converts energy from the proton motive force of the H+ gradient to chemical bond energy in ATP
• as the H+ flows through, the green guy spins, bringing the ADP and inorg phosphate together
• conformation changes produce ATP
• be able to draw vaguely - the balloon part in the in matrix

Question 19

carbohydrate, protein, and fat metabolism

Answer 19

• carbs, protein, and fat can be used for energy, not just glucose
• use same pathways to increase efficiency, but enter glycolysis or citric acid cycle at different points

Question 20

anabolism

Answer 20

• using metabolism to make molecules

Question 21

strategies for environments that lack oxygen

Answer 21

1. use substance other than oxygen as the final electron acceptor in ETC
   
   • ex: E.coli uses nitrate
2. produce ATP only via substrate level phosphorylation

Question 22

substrate level phosphorylation

Answer 22

• method of synthesizing ATP that occurs when an enzyme directly transfers a phosphate from an organic molecule to ADP
• phsosphorylated organic molecule and ADP bind to the enzyme and, therefore, are the enzyme’s substrates
  
  • ADP is then phsophorylated to form ATP

Question 23

Fermentation

Answer 23

• the breakdown of organic molecules without net oxidation
• in anaerobic conditions, organisms that use O2 as final electron acceptor need another way to produce ATP (like glycolysis)
• Glycolysis makes too much NADH, which is bad (no longer have NAD+)
• muscles solve this by reducing pyruvate into lactate
• yeast solve this by making ethanol
• fermentation makes a lot less ATP than oxidative phosphorylation