Biology: ATP Creation and Function

Study Notes

ATP is created from ADP (Adenosine Diphosphate) through phosphorylation, adding a phosphate to ADP
This process requires energy input, making it an endergonic reaction
ATP Synthase is the enzyme responsible for synthesizing ATP
ATP is a very reactive molecule that releases energy quickly, making it ideal for immediate use
ATP's structure has negatively charged phosphates that repel each other, storing potential energy

ATP is the primary energy carrier in cells, powering essential processes
It is vital for the cell cycle, including cell division and overall metabolism
ATP is used to build polymers from monomers
It is required for muscle contractions and powering movement
Active transport of molecules against their concentration gradients requires ATP
ATP also plays a role in cellular signaling pathways

Passive Transport does not require energy input; molecules move from areas of high concentration to low concentration
- Simple Diffusion: Molecules move freely across a membrane without assistance
- Facilitated Diffusion: Larger molecules or hydrophilic molecules require transport proteins to move across the membrane
Active Transport requires energy to move molecules against their concentration gradient, often using transport proteins

Occurs in chloroplasts, which contain two key compartments:
- Thylakoids: Contain light-absorbing pigments and are the site of light-dependent reactions
- Stroma: The aqueous space where the Calvin cycle (light-independent phase) takes place, synthesizing sugars
Light-Dependent Reactions require sunlight and occur in the thylakoids, producing ATP and NADPH
Calvin Cycle does not require sunlight and utilizes ATP and NADPH to convert carbon dioxide into glucose in the stroma
The overall reaction is: 6 CO2 + 6 H2O + light energy → C6H12O6 + 6 O2
Oxygen is released during the splitting of water molecules within the thylakoid membrane to replace energized electrons used in chlorophyll
Chlorophyll absorbs most wavelengths except green, which is reflected, giving plants their green color

Aerobic Respiration uses oxygen to produce ATP
Begins with Glycolysis, which occurs in the cytoplasm, producing pyruvate and a small amount of ATP (2 ATP), along with NADH
The pyruvate from glycolysis enters the Krebs Cycle, also known as the citric acid cycle, which takes place in the mitochondria, producing more ATP (2 ATP), NADH, and FADH2
The final stage is the Electron Transport Chain, also in the mitochondria, which utilizes NADH and FADH2 to produce the majority of ATP (up to 34 ATP)
During the Electron Transport Chain, energized electrons pass through a series of proteins, creating a proton gradient that is used to drive ATP synthesis
Oxygen acts as the final electron acceptor, forming water
Anaerobic Respiration does not use oxygen and produces less ATP (only 2 ATP)
Common in bacteria and some eukaryotes (e.g., yeast)
Fermentation is a type of anaerobic respiration that produces energy in the absence of oxygen
- Alcoholic Fermentation: Produces ethanol (alcohol) and carbon dioxide, commonly done by yeast
- Lactic Acid Fermentation: Produces lactic acid, occurs in human muscle cells when oxygen supply is limited, leading to muscle fatigue