Lecture 10-11

Question 1

• Cellular respiration:

Answer 1

• Cellular respiration:
  o Collection of metabolic reactions within cells that break down food molecules and use free energy to synthesize ATP
  o Ultimate source for this process: carbohydrates, fats, proteins, photosynthesis

Question 2

• Glucose and gasoline

Answer 2

• Glucose = gas of molecules
  o Gasoline: Carbon to hydrogen bond when most energy is stored, reformation of other atoms, organic molecule
   Electrons are far away from nucleus
  o Glucose: OH (less energy than gasoline) since it has oxygen (wishes to hold on to electrons)
   Thus electrons are held closer to nucleus of oxygen atom
  o Combustion of glucose or gasoline in presence of oxygen releases heat as reactants are converted into CO2 and H2O
  o Energy produced during formation of bonds (aka products) is greater than energy required to break bonds in reactants

Question 3

Coupled Oxidation

also see diagram

Answer 3

Coupled Oxidation – reduction reactions are central to energy metabolism

• Oxidation: partial or full loss of electrons from a substance
• Reduction: partial or full gain of electrons to a substance
• Redox: coupled reaction between oxidation and reduction
• LEO THE LION SAYS GER
  o Losing electrons = oxidation
  o Gaining electrons = reduction
• Transfer of Hydrogen = transfer of electron (redox)
• When a molecule loses hydrogen, it becomes oxidized

Question 4

Cellular respiration is controlled combustion

Answer 4

Cellular respiration is controlled combustion

• Aerobic Respiration Oxidation of Glucose by O2 into CO2 and Water: C6H12O6 + 6O2 6CO2 + 6H2O G = - 686 kcal/mol By Catabolizing (releasing energy by breaking down large organic molecules into smaller ones) glucose in steps, more energy can be harnessed to make ATP

Question 5

• Aerobic Respiration:

Answer 5

• Aerobic Respiration:
  o Heat energy increase = energy is then released in one big step could denature enzyme
  o Solution: stepwise oxidation of glucose in cells, so that you don’t need to spend ATP, can capture most of the energy from glucose captured by cell, AE energy is much lower, reaction cns occur in cell without copious amounts of energy expenditure

Question 6

• Oxidation of glucose occurs through series of…

Answer 6

• Oxidation of glucose occurs through series of enzyme-catalyzed reactions with a small activation energy
  o Exergonic, same change in free energy (change in G is negative)

Question 7

• Cellular respiration = controlled combustion

Answer 7

• Cellular respiration = controlled combustion
  o Potential energy of glucose is not liberated suddenly, rather a slow release with energy being transferred to other molecule
  o Oxidation of food molecules occurs in presence of group of enzymes called dehydrogenases
   Dehydrogenases facilitate transfer of electrons from food to a molecule
  • Most common energy carrier = NAD (oxidized) and NADH (reduced)
  • NAD: Co-enzyme • Not a protein • Used in the electron transport chain Potential energy carried in NADH is used to synthesize ATP
   During respiration, dehydrogenases remove two H atoms from a substrate molecule and transfer two electrons (and only one proton) to NAD, reducing it to NADH
  • This enzyme catalyzed transfer = high effiency

Question 8

• NAD

Answer 8

• NAD
  o It is a carrier, no amino group is not a protein, work with enzyme which is protein, it is rather a co-protein, it takes on electron
  o How you capture energy (place on intermediate molecule) for later use

Question 9

• Primary goal of cellular respiration:

Answer 9

• Primary goal of cellular respiration: transform potential energy in food molecules into ATP

Question 10

• 3 phases of cellular respiration:

Answer 10

• 3 phases of cellular respiration:
  1. Glycolysis:
  a. enzymes break down food molecules and glucose into two molecules of pyruvate, some ATP and NADH are synthesized
  2. Pyruvate oxidation and citric acid cycle:
  a. Acetyl coenzyme enters metabolic cycle = completely oxidized to CO2, some ATP and NADH are synthesized
  3. Oxidative phosphorylation:
  a. NADH synthesized by glycolysis and citric acid cycle = oxidized
  b. Liberated electrons = passed along electron chain and transferred to oxygen, producing water
  c. Free energy realised during electron transport = used to generate proton gradient across membrane = used to synthesize ATP

Question 11

• Eukaryotic cell =

Answer 11

• Eukaryotic cell = citric acid cycle and oxid. Phos. occur in mitochondrion

Question 12

• Mitochondrion = powerhouse of cell

Answer 12

• Mitochondrion = powerhouse of cell, largest generator of ATP
  o Composed of 2 membranes: outer and inner
   Intermembrane space: found between outer and inner membranes
   Matrix: interior aqueous environment

Question 13

• Prokaryotic cells:

Answer 13

• Prokaryotic cells: electron transfer and oxid. Phos. occur on plasma membrane

Question 14

Glycolysis is also known as

Answer 14

splitting of glucose

Question 15

• Glycolysis : 10 sequential enzyme-catalyzed reactions leading to oxidation of 6 carbon sugar glucose
  o Produces …

Answer 15

• Glycolysis : 10 sequential enzyme-catalyzed reactions leading to oxidation of 6 carbon sugar glucose
  o Produces 2 molecules of three carbon compound pyruvate
  o Potential energy released in oxidation = synthesis NADH and ATP
  o NAD: • Strips TWO H from organic molecules (2 electrons and 2 protons) • Reduces to NADH + H+ • NADH oxidizes (releases H+ plus 2 e-) in electron transport chain to convert back to NAD

Question 16

• ATP production in glycolysis:

Answer 16

• ATP production in glycolysis:
  o Bond forms due to free energy
  o Glucose is – free energy
  o ATP is then created

Question 17

• Reactions of glycolysis

o During process no ….

Answer 17

• Reactions of glycolysis
  o During process no carbon molecules have been lost
  o ATP is generated by substrate phosphorylation
  o NAD is an oxidizing agent because it is being reduced

Question 18

• Overview Glycolysis:
   All organisms can do glycolysis
   Happens in the cytosol does not need mitochondria
   Means sweet breakdown (universal – which means it is ancient)
   Occurs in cytosol
   Cells spend 2 ATP and 2 ADP, get 2 (net change of 2 ATP)

Answer 18

• Overview Glycolysis:
   All organisms can do glycolysis
   Happens in the cytosol does not need mitochondria
   Means sweet breakdown (universal – which means it is ancient)
   Occurs in cytosol
   Cells spend 2 ATP and 2 ADP, get 2 (net change of 2 ATP)

Question 19

• Three facts of Glycolysis:

Answer 19

• Three facts of Glycolysis:
  1. Glycolysis is universal, found in 3 domains of life
  2. Does not depend upon presence of O2
  3. Occurs in cytosol of cells via soluble enzymes = does not require complicated electron transport chains and internal membrane systems to function

Question 20

• ATP molecules

Answer 20

• ATP molecules
  o Produced in glycolysis
  o Result from substrate-level phosphorylation

Question 21

• Substrate-level phosphorylation

Answer 21

• Substrate-level phosphorylation
  o Enzyme-catalyzed reaction
  o Transfers phosphate group from substrate to ADP

Question 22

3 steps in glycolysis:

Answer 22

1. Energy investment followed by payoff
2. No carbon is lost
3. ATP is generated by substrate level phosphorylation

Question 23

1. Energy investment followed by payoff

Answer 23

a. Glucose has 6 c atoms and O,
b. Spend ATP, adds phosphate group to change structure of glucose
c. Due to physical reactions, it rearranges itself
d. Spend more ATP to take phosphate group to stick at other end of molecule (to balance it out) (total of 2 phosphate groups on glucose) Investment of 2 ATP for each glucose molecules = energy reward (4 ATP and two NADH molecules are produced during energy releasing phase)
e. Enzyme comes into play and molecule splits in two, (1 glucose molecule splits into 2 molecules) 3 carbon and a phosphate and three carbon and a phosphate

Question 24

2. No carbon is lost

Answer 24

a. Reaction of glycolysis converts glucose into 2 molecules of pyruvate (oxidization results in EP of two molecules of pyruvate less than one molecule of glucose)
b. NAD captures electron and becomes NADH (spent energy)
c. Binds itself to molecule (captures energy)
d. ADP using stored energy of previous molecule to stick phosphate to ATP molecule
e. Recapture 2 ATP
f. Captured more energy than put in
g. Important you get four ATP, and you spend 2 and the result is pyruvate

Question 25

3. ATP is generated by substrate level phosphorylation

Answer 25

a. During glycolysis= ATP generated by phosphorylation | i. This process involves transfer of high-energy substrate molecule to ADP