chapter 10

cellular respiration:

in respiration, glucose is oxidized and oxygen is reduced

energy is released as the electrons associated with hydrogen ions are transferred to oxygen (when water is produced)

NAD+ is a coenzyme that functions as an oxidizing agent (gets reduced to NADH) during respiration

steps of cellular respiration:

• glycolysis

• citric acid cycle

• oxidative phosphorylation

for each one molecule of glucose degraded to CO2 and H2O by respiration, the cell makes up to 32 molecules of ATP

glycolysis

• breaks down glucose into 2 pyruvate

• occurs in the cytoplasm

• has two main steps: energy investment and energy payoff (the energy investment step is the only step in the whole process of respiration that uses ATP)

  • first two ATP split glucose into two G3P (1)

  • then the G3P molecules are oxidized, and the electrons are taken by NAD+ which becomes NADH (2)

  • the two G3Ps become two pyruvates, releasing four ATP in the process (2)

• anaerobic

• 2 ATP net production

citric acid cycle

• aerobic

• occurs in the mitochondrial matrix

• breaks down pyruvate into CO2

  • before the cycle, pyruvate is turned into acetyl CoA

• generates 1 ATP, 1FAHD2, 3 NADH per turn

  • 1 glucose (2 pyruvates, 2 acetyl CoA) means two cycles, so there is 2 ATP, 2 FADH2, and 6 NADH in total

• eight steps:

  • acetyl CoA + oxaloacetate → citrate (1)

  • decomposing the citrate back into oxaloacetate, forming the cycle (2-8)

• the NADH and FADH2 are crucial for the next part of the process, since they’re important electron donors (reducing agents)

• 2 ATP net production

oxidative phosphorylation

• occurs along the electron transport chain in the inner membrane of the mitochondrion (cristae)

• electron carriers are constantly switching between reduced and oxidized states during this

• electrons are transferred from NADH or FADH2 to the electron transport chain

• electrons are passed through a bunch of proteins called cytochromes to O2 (the final electron acceptor in the ETC)

• H+ is pumped from the mitochondrial matrix to the intermembrane space

• then it moves down its concentration gradient back across the membrane through the ATP synthase

  • this is chemiosmosis, the use of energy in a H+ gradient to drive cellular work

• 28 ATP net production

only about 34 percent of the energy in a glucose molecule is converted to ATP, the rest is lost as heat

most of the co2 released during respiration is produced in the citric acid cycle

2 electrons form one water

anaerobic respiration:

• so4 2- is the final acceptor for electrons

• fermentation regenerates nad+

gain of h+ is reduction