Cellular Respiration
101
This week, I will be covering Cellular Respiration easily and shortly for those learning this concept or reviewing it.
Cellular Respiration is the lengthy term for describing the biochemical process of how our body converts energy from glucose (without sunlight) into ATP.
This process occurs in both eukaryotic and prokaryotic cells and is broken down into 4 Steps. Although the stages do not occur in all the same areas of the mitochondria.
Overall Equation: C6H12O6 + 6O2 --> 6CO2 + 6H2O + BUNCH OF ATP
Essentially, glucose (C6H12O6) along with the input of oxygen (important=aerobic respiration) creates carbon dioxide, water, and a BUNCH of ATP (important: roughly 32-36 ATP molecules)
Stage 1: Glycolysis
Glycolysis occurs in the cytoplasm, outside of the mitochondria this is the free space within the cell.
Glucose a 6-carbon molecule is split into two 3-carbon molecules called pyruvate. This is done through the process we call "investment phases". Requiring an input of 2 ATP with an output we call "payoff phase" generates 4 ATP, resulting in a net of 2 ATP.
Coupled with producing 2 NADH molecules transferring electrons to NAD+.
NET INPUT: Glucose - NAD+ - 2ATP
NET OUTPUT: 2 Pyruvate - 2 ATP - 2 NADH
Stage 2: Pyruvate Oxidation
Pyruvate Oxidation occurs within the mitochondrial matrix.
Each pyruvate molecule is first converted to acetyl-CoA (coenzyme A). Coupled with carbon being released as CO2 (byproduct) from each pyruvate molecule. NAD+ is then reduced again converting to more NADH
NET INPUT: 2 Pyruvate - 2 NAD+
NET OUTPUT: 2 Acetyl-CoA - 2 NADH - 2 CO2
Stage 3: Citric Acid Cycle (Krebs Cycle)
Krebs Cycle similarly, occurs in the mitochondrial matrix.
Acetyl-CoA forms citrate, broken down continuously again through redox reactions (you do not need to remember this for the AP exam). Just know that through these redox reactions, citrate is continuously broken down thus releasing CO2.
NAD+ along with FAD are reduced to NADH and FADH2. ATP is synthesized through substrate-level phosphorylation.
NET INPUT: 2 Acetyl-CoA - 6 NAD+ - 2 FAD
NET OUTPUT: 6 NADH - 2 FADH2 - 2 ATP - 4 CO2
Stage 4: Oxidative Phosphorylation
Oxidative Phosphorylation occurs within the inner membrane of the mitochondria. If the matrix is the folding of the mitochondria, visualize this location as the inner area.
Remember the NADH and FADH2 molecules produced through earlier stages? These molecules are electron carriers oxidizing themselves and donating electrons to the electron transport chain (ETC)
Through the donation of electrons, this generates a proton pump (H+) into the intermembrane space. Similarily to photosynthesis electron gradient is formed in the lumen, this process is called chemiosmosis. This makes protons favorable to flow into ATP synthase spinning the rotor, and generating loads of ATP.
Oxygen is the final electron acceptor (H+) forming water as a byproduct.
Oxidative Phosphorylation generates roughly (28-32 ATP molecules)
NET INPUT: 6 NADH - 2 FADH2
NET OUTPUT - 28-32 ATP - 6 H2O - 6 NAD+ - 2 FAD
Key Ideas
Remember cellular respiration is also known as aerobic respiration. This process is under the condition that glucose and oxygen are present. This process produces a higher yield of ATP in comparison to anaerobic respiration (this was covered in an earlier topic)
