U1: C3 Cellular Metabolism

Question 1

Aerobic Resipiration (for euk)

1. 4 steps
2. Location of each step
3. net/glu for each step
4. Total ATP production per step

Answer 1

1. Glycolysis
   
   • Cytoplasm
   • 1 glu-> 2 pyr + 2 ATP + 2 NADH
     
     • 2 input ATP, 4 ouput ATP
   • 2 ATP + (2 NADH * 2 ATP/NADH (bc costs 1 ATP to transport into matrix) =
     
     • 6 ATP (for euk),
     • 8 ATP (for prok)
2. Pyruvate decarboxylation (req ATP to travel)
   
   • mitochondrial matrix
   • (1 pyr -> acetyl group + NADH + CO₂) x 2
     
     • (1 CoA + 1 NAD⁺ input) x 2
   • 2 NADH * (3 ATP/NADH) = 6 ATP
3. Kreb Cycle
   
   • mitochondrial matrix
   • (1 acetyl CoA + oxaloacetic acid (4C) -> citrate (6C) + 3 NADH + 1 FADH + 1 GTP + 2 CO₂) x 2
   • (1 GTP + [3 NADH x (3 ATP/NADH)] + [1 FADH₂ x (2 ATP/FADH₂)] x 2
     
     • 24 ATP
4. ETC
   
   • oxidation phosphoralyation occurs here.
   • All the NADH and FADH₂ used to make ATP
   • Glycolysis is the only step that does not utlized ETC and uses substrate phosphorylation
5. TOTAL ATP

• EUK (6+ 6 + 24) = 36 ATP
• PRO (6 + 8 + 24) = 38ATP

Question 2

FADH₂ = how much ATP

NADH = how much ATP

Answer 2

• FADH₂ = 2 ATP
• NADH = 3 ATP if produced in mitochondrial matrix
• NADH = 2 ATP if produced in cytosol (in the euk only)
• 1 ATP is req to transport Pyr into the matrix, that is why 1 NADH is removed in euk.
  
  • prok do not have organelles

Question 3

Metabolism consists for 2 parts

Answer 3

1. Catabolism breaks down stuff for energy
2. Anabolic: uses energy to build stuff for storage

Question 4

What steps are in aerobic/anaerobic metabolism?

Answer 4

1. aerobic
   
   1. glycolysis (not req oxygen)
   2. oxidative decarboxylation
   3. kreb cycle
   4. ETC
2. anerobic (no oxygen req)
   
   1. glycolysis
   2. Alcohol and lactic acid fermentation

Question 5

Aerobic metabolism of glucose

Answer 5

• Complete oxidation of metabolite (glucose) to carbon dioxide.
• ~ 36 ATP produced per glucose.
• C₆H₁₂O₆ + 6O₂ => 6CO₂ + 6H₂O
• C₆H₁₂O₆: this is glucose. You get it from your diet.
• 6O₂: this is molecular oxygen that you breath in.
• 6CO₂: this is carbon dioxide produced by the Krebs cycle. Both the carbon and oxygen in this CO₂ comes from the metabolite (glucose).
• 6H₂O: this is water produced in the electron transport chain. The oxygen comes completely from the molecular oxygen that you breath in.

Question 6

Aerobic Metabolism of glucose

• if we follow the carbon from glucose where does it end up
• ”” oxygen from glucose..
• ”” oxygen you breath in..
• ’’ hydrogens from glucose..

Answer 6

• If we were to follow the carbon in the metabolite (glucose), it will end up in carbon dioxide.
• If we were to follow the oxygen in the metabolite (glucose), it will end up in carbon dioxide.
• If we were to follow the oxygen you breath in, it will end up in water.
• As for the hydrogens, they’ll either be in water, exist as protons in solution, or be transferred to some other entity.
• As we can see, the total reaction involves complete oxidation of the metabolite (glucose) and complete reduction of molecular oxygen.
• When electrons pass from the metabolite (glucose) to molecular oxygen, energy is released.
• The electron transport chain harnesses this energy.

Question 7

Anaerobic metabolism of glucose

Anaerobic metabolism of glucose

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Answer 7

• Partial oxidation of metabolite (glucose) to pyruvate.
• 2 net ATP produced per glucose.
• Pyruvate is then reduced to either alcohol or lactate.
• Bacteria reduce pyruvate to alcohol in a process called alcohol fermentation.
• Humans reduce pyruvate to lactate in a process called lactic acid fermentation.
• Partial oxidation of metabolite (glucose) to pyruvate.
• 2 net ATP produced per glucose.
• Pyruvate is then reduced to either alcohol or lactate.
• Bacteria reduce pyruvate to alcohol in a process called alcohol fermentation.
• Humans reduce pyruvate to lactate in a process called lactic acid fermentation.

Question 8

Electron transport chain, oxidative phosphorylation, substrates and products, general features of the pathway

Answer 8

1. The electron transport chain (ETC) is essentially a series of redox reactions, where NADH gets oxidized to NAD⁺ and O₂ gets reduced to H₂O.

• The series of redox reactions consists of electrons passing from NADH to FMN, to Coenzyme Q, iron-sulfur complexes, and cytochromes (cytochrome b, c and aa₃) before finally being used to reduce oxygen.
• NADH is highest in energy, while O₂ is lowest in energy. When electrons are passed from NADH down a series of proteins and finally to O₂, energy is released.

1. FADH₂ is lower in energy than NADH, that’s why it releases less energy when it gets oxidized.
   * FADH₂ skips FMN and passes its electrons to Coenzyme Q.
2. The energy released from these reactions generates a proton gradient, which drives ATP synthase to make ATP. This is called oxidative phosphorylation.

Question 9

Proton gradient

Answer 9

• The energy released from passing electrons down the ETC is used to pump protons into the intermembrane space of the mitochondria.
• H+ concentration is very high in the intermembrane space (higher than those in the matrix). Thus, this establishes an electrochemical gradient called the proton gradient.
• H+ wants to migrate down the proton gradient (from the intermembrane space back into the matrix), but it can only do this by going through the ATP synthase.
• Like a water mill, ATP synthase harnesses the energy of the falling protons to convert ADP into ATP.

Question 10

ETC is inhibited by ..

Answer 10

certain antibiotics, by cyanide, azide, and carbon monoxide.

Question 11

Fat metabolism (review org)

Answer 11

1. Location: beta-oxidation occurs in the matrix of the mitochondria.
2. Ester hydrolysis occurs in the cytosol.
   
   1. Fatty esters gets hydrolyzed into free fatty acids by lipases.
3. For example, triacylglycerol gets hydrolyzed into free fatty acids and glycerol.
   
   1. With the help of ATP, the fatty acid is “activated” at the acid end by CoA (to be precise, it turns into a thioester).
   2. A process called beta-oxidation breaks down the fatty-CoA, 2 carbons at a time, to make acetyl CoA.
   3. β-oxidation produces acetyl CoA and also FADH2 and NADH.

The acetyl CoA feeds into the Krebs cycle, and the FADH2 and NADH feed into the ETC.
4. On a per gram basis, fats give more energy than any other food source.

Question 12

Protein metabolism (review org)

Answer 12

1. Proteins are broken down into amino acids by peptidases.
2. The nitrogen in the amino acid is converted to urea (for desert animals, birds and reptiles, it is uric acid).
3. The carbon in the amino acid is converted to pyruvate or acetyl-CoA, (or other metabolical intermediates such as oxaloacetate), depending on what amino acid it is.
   
   1. The carbon products from amino acid metabolisms can either feed into the Krebs cycle, or be the starting material for gluconeogenesis.

Question 13

Anaerobic Respiration

1. Steps
2. Types

Answer 13

1. Glycolysis and Fermentation

• Glycolysis: makes 2 ATP/ glu
• Fermentation: oxides coenzyme
  
  • NADH-> NAD+ to cycle back into glycolysis.

2. Ethanol (yeast and bacteria) & lactic acid (bacteria and muscle cells when no Oxygen)

Question 14

ETC (Image)

Question 15

Kreb (image)

Question 16

Fates of Pyruvate

Question 17

Pyruvate Decarboxylation (image)

Question 18

Glycolysis (image)

Question 19

Carbohydrate Alternative E source

Answer 19

Glycogen (stored in liver)

glycogen hydrolysis-> GAL-P —> GLYCOLYSIS

Question 20

Fats Alternative E sources

Answer 20

Triglyceraldehyes (stores in adipose tissue)

break down into glycerol and Fatty Acids

Glycerol -> GAL-P —> GLYCOLYSIS

Fatty acids -beta oxidation-> Acetyl CoA –> KREB

Question 21

Protein Alternative E source

Answer 21

Amino acids (R, COOH, NH2)

Deamination-> alpha keto acid-> acetyl coa + pyr

Transamination-> ketoacid -> acetyl coa + any intermediate of kreb cycle

Question 22

B oxidation

Answer 22

cleaves 2 C @ a time of a fatty acid

and produces 1 NADH + 1 FADH₂ per cleavage

Question 23

Anytime a molecule is transported into a matrix, what occurs

Answer 23

ATP input required.

1. Pyruvate (1 NADH)
2. Fatty Acids (1 ATP into mitochondria, 1 ATP into matrix)