Lecture notes Wed. October 1

Central focus on glycolysis, Krebs cycle, and ATP production through different shuttles and metabolic pathways.

Color Printing Analogy: A color printer provides a clearer and higher quality image than a black and white printer.
The first page of discussion covers glycolysis utilizing the malate-aspartate shuttle leading to the activation of pyruvate before entering the Krebs cycle.
The electron transport chain (ETC) follows these processes, leveraging the NADH and FADH₂ produced in the mitochondria to synthesize ATP.

This shuttle predominantly operates in the liver and effectively transports electrons.
Each glucose molecule facilitates two pyruvate molecules leading into the Krebs cycle after glycolysis.
NADH & FADH₂ production: For every molecule of glucose: 2 NADH from glycolysis (with activation to pyruvate) and 6 NADH through the Krebs cycle (3 from each turn due to 2 turns per glucose).
- Formula:
  - Net NADH from glycolysis: 2 NADH
  - Krebs cycle: 6 NADH
Therefore, total NADH equals 8 NADH (2 from glycolysis activation, 6 from Krebs) which play a role in further ATP production.

The glycerol phosphate shuttle functions mainly in skeletal muscle.
While it serves a similar role to the malate-aspartate shuttle, the critical difference lies in the transport of electrons represented as FADH₂ instead of NADH.
Both shuttles yield similar outputs aside from this difference, highlighting the need for understanding the context of each shuttle based on tissue type.

Determine ATP yield based on which shuttle is used:
- Malate-Aspartate Shuttle: 40 total ATP
- Glycerol Phosphate Shuttle: 38 total ATP
Knowing which shuttle leads to which ATP total is essential for answering metabolic efficiency questions in exams.

Shuts down glycolysis when oxygen is limited, forming lactate as an end product instead of proceeding to aerobic pathways.
Important to recognize the difference in pathways when producing ATP under aerobic versus anaerobic conditions.

A focused examination on the products from the Krebs cycle is needed:
Each turn of the Krebs cycle yields 3 NADH, 1 FADH₂, and 1 ATP, producing 2 CO₂ as byproducts for each glucose molecule.
Formula for Adaptation:
- Total net NADH from cycle: 3 NADH/turn x 2 turns = 6 NADH
- From the activation of pyruvate: additional ATP and CO₂ generation.
- Each NADH via the ETC yields approximately 2.5 ATP, while FADH₂ yields roughly 1.5 ATP in ATP synthesis.

All metabolic pathways lead to an aggregate production of ATP:
- Total Energy: 40 ATP via malate-aspartate shuttle or 38 ATP via glycerol phosphate shuttle.
  - Key Calculations for group problems:
  - Total ATP yield indicated by the type of shuttle optimal for ATP production based on the cells involved in metabolism (i.e. liver or muscle).

Memorization of key differences between the two shuttles is crucial:
- Malate-aspartate = liver, glucose metabolism (40 ATP)
- Glycerol phosphate = skeletal muscle (38 ATP)
Suggestion: Download concurrent study guides or diagrams to assist learning and retention.

Transition into lipid metabolism has been established with energy breakdown from triglycerides.
- Triglyceride Structure: Consists of a glycerol backbone and three fatty acid chains.
- Lipase: Enzymes used to break down triglycerides into glycerol and free fatty acids (FFAs).
- Beta-Oxidation: This process further breaks down FFAs into acetyl-CoA which feeds into the Krebs cycle for energy production.
Important to remember that lipids yield more ATP than glucose, with a triglyceride yielding about 400-500 ATP.

Energy is primarily drawn from lipids (stored as triglycerides) and carbohydrates (glycogen).
Energy efficiencies differ for fuel brands:
- ATP is the immediate energy source for muscle contraction.
- Creatine phosphate serves as a quick source to regenerate ATP during high-intensity activities.

Understanding the impact of exercise intensity on the types of fuels utilized (higher intensity favors glucose; lower favors fat), along with misconceptions around fat burning zones and caloric expenditure during exercises.
Recognition of carb use increases when oxygen is scarce, which is important to note for endurance training strategies.

Proteins primarily break down into amino acids via proteolysis, followed by deamination process that creates an increase in blood urea as a toxic byproduct.
Amino acids can be further classified based on their metabolic pathways:
- Glucogenic: Can be converted to glucose. Min. 6 carbons required.
- Ketogenic: Convert to acetyl-CoA, entering Krebs for energy.

ATP: Primary energy currency with limited storage.
Phosphocreatine: Resupplies ATP rapidly for short bursts of activity.
Anaerobic Glycolysis: Supplies energy via glucose for immediate activity (30 seconds max).
Glycogen Stores: Complex carbohydrate reserve; approximately 4,000 Kcal available.
Lipids: Mediate vast energy reserves due to less hydration mass per gram, contributing to endurance.

Varying factors must keep in consideration for optimizing energy systems including effects of high protein diets and dynamic exercise.
Close attention must be given to exercise intensity as a modulating factor in fuel utilization and overall energy balance.
Emphasis on maintaining a balance between carb, fat, and protein intake for optimal performance and bodily function.