cellular respiration

Anabolism and Energy

Sugars are combined through dehydration reactions to form carbohydrates.
Anabolism, where smaller molecules combine to form larger ones, requires energy.
ATP (adenosine triphosphate) provides this energy, converting to ADP (adenosine diphosphate) as it loses a phosphate group.
The release of the phosphate group from ATP is what provides energy for reactions.

ATP supplies energy for anabolism, such as when amino acids combine to form proteins.
ATP is converted to ADP when it loses a phosphate group, thereby releasing energy.
ATP's role as an energy provider depends on the presence of its phosphate group. Removal or oxidation of this group renders ATP unable to provide energy.

Cellular respiration involves multiple phases.
Key concepts include oxidation (loss of electrons) and reduction (gain of electrons), summarized by the mnemonic "OIL RIG" (Oxidation Is Loss, Reduction Is Gain).

Cellular respiration has nine steps, while the Krebs cycle has approximately ten steps.

Cells constantly perform processes, including active transport, requiring ATP (adenosine triphosphate) for energy.
ATP is a type of nucleic acid composed of adenosine and three phosphates.
Cells, whether prokaryotic or eukaryotic, must produce ATP through various processes.
Aerobic cellular respiration occurs in eukaryotic cells, which contain membrane-bound organelles like the nucleus and mitochondria.
Mitochondria play a central role in aerobic cellular respiration.

The primary goal of aerobic cellular respiration is to produce ATP.
The overall equation for aerobic cellular respiration involves reactants (inputs) on the left side and products (outputs) on the right side.
This equation is similar to that of photosynthesis, with reactants and products on opposite sides.
In photosynthesis, organisms produce glucose, while in cellular respiration, glucose is broken down to generate ATP.
A germinating bean seed relies on stored glucose and cellular respiration to produce ATP for growth until it develops leaves and can perform photosynthesis.
Plants perform both photosynthesis (to make glucose) and cellular respiration (to break down glucose).
Non-photosynthetic organisms, like humans and amoebas, must obtain glucose from food sources to initiate cellular respiration.

Glycolysis occurs in the cytoplasm and does not require oxygen (anaerobic).
During glycolysis, glucose is converted into pyruvate, a more usable form.
Glycolysis requires a small amount of ATP to initiate.
The net yield from glycolysis is approximately two pyruvate molecules, two ATP molecules, and two NADH molecules.
NADH is a coenzyme that transfers electrons, which are used to produce more ATP later.

Pyruvate molecules are transported into the mitochondrial matrix via active transport.
In the mitochondria, pyruvate is oxidized and converted to acetyl CoA, which is used in the next step (Krebs cycle).
Carbon dioxide is released, and two NADH molecules are produced during this step.

The Krebs cycle occurs in the mitochondrial matrix and is considered an aerobic process.
While the cycle does not directly consume oxygen, some events within it require oxygen to continue.
During the Krebs cycle, carbon dioxide is released, and two ATP molecules, six NADH molecules, and two FADH2 molecules are produced.
FADH2, like NADH, is a coenzyme that assists in transferring electrons to produce more ATP.

In eukaryotic cells, the electron transport chain and chemiosmosis occur in the inner mitochondrial membrane and require oxygen (aerobic).
Electrons are transferred from NADH and FADH2 to protein complexes and electron carriers.
The electrons are used to generate a proton gradient by pumping protons (H+) across the intermembrane space, creating an electrical and chemical gradient.
Protons travel down their electrochemical gradient through ATP synthase, an enzyme that produces ATP by adding a phosphate to ADP.
Oxygen acts as the final electron acceptor. When oxygen combines with two hydrogens, water (H2O) is produced.

The electron transport chain and chemiosmosis produce significantly more ATP than the previous steps.
The number of ATP molecules produced per glucose molecule varies depending on factors like the proton gradient across the mitochondrial membrane.
Estimates range from 26 to 34 ATP molecules produced by the electron transport chain and chemiosmosis alone.
Including the other two steps (Krebs cycle and glycolysis), the total ATP production ranges from 30 to 38 net ATP molecules per glucose molecule.

In the absence of oxygen, some cells perform fermentation to produce ATP, although it is less efficient.

ATP production is crucial for cells.
Substances like cyanide can block steps in the electron transport chain, inhibiting ATP production and potentially causing death.
Mitochondrial diseases are an area of increased research due to the mitochondria's central role in ATP production.

The first step of cellular respiration is glycolysis.
The word glycolysis means “cutting the sugar”.
The glucose is snipped in half in your cells.
The snipping of sugar gives two smaller pieces called pyruvate.
Glucose \rightarrow 2 \space Pyruvate This process is an example of catabolism.
The splitting of glucose into pyruvate happens in the cytoplasm.
Free energy is ATP - the glucose broken into pyruvate produces ATP and gives reduced electron carriers called NADH.

Acetyl CoA - This is a ticket to the next energy ride.
It jumps into this spinning cycle, a spinning cycle. With every spin, products are created:
2 ATPs
NADH and FADH2. (Electron Carriers)
Carbon Dioxide

NADH and FADH2, these "energy delivery trucks" drop off elections off at Electron Transport Chain (ETC)
Hot potato, machine pass along the electrons from "energy delivery trucks", they pump protons (H+) across the wall, builds pressure and then Chemomyosis.
Chemo Osmosis: Gradient is being established when moving protons(H+) from high to low concentrations.
When the protons reach a space of lower concentration, the moving protons spin a machine call ATP synthase, which is like a tiny windmill, making a ton of ATP.
Finally, oxygen comes in, grabs the used electrons and Hydrgon and forms water.