Week 2 Flashcards
(43 cards)
Bioenergetics definition?
The flow and exchange of energy within a living system, primarily the conversion of foodstuffs (fats, proteins, carbohydrates) into usable energy for cellular work.
How this relates to performance - energy systems etc. Chemical > Mechanical
Key Components of the Cell?
Cell Membrane (Sarcolemma): Semipermeable, separates the cell from its environment.
Nucleus: Houses genes for protein synthesis.
Cytoplasm (Sarcoplasm in muscle): Fluid portion containing organelles.
Mitochondria: Site of oxidative phosphorylation.
Metabolism definition and types?
Sum of all chemical reactions in the body.
Anabolic Reactions: Synthesis of molecules (e.g., glucose stored as glycogen).
Catabolic Reactions: Breakdown of molecules (e.g., glycogen into glucose).
Types of Cellular chemical Reactions?
Endergonic: Require energy input to be added to reactants
Exergonic: Release energy.
Coupled Reactions: Energy from exergonic reactions drives endergonic reactions (e.g., ATP hydrolysis).
Oxidation-Reduction Reactions:
Oxidation: Electron removal.
Reduction: Electron addition.
Nicotinamide adenine dinucleotide (NAD) and Flavin adenine dinuceotide (FAD) act as carrier molecules in bioenergetic reactions.
First Law of Thermodynamics?
Energy cannot be created or destroyed, only transformed.
Enzymes role, characteristics and classifications? ?
Role: Proteins that are Catalysts for reactions via lowering activation energy (by forming enzyme substrate complexes which alter shape), increasing reaction speed/product formation
Key Characteristics:
Enzymes remain unchanged after reactions.
Influenced by temperature and pH(e.g., intense exercise lowers pH due to increased H+).
Kinases: Add phosphate groups.
Dehydrogenases: Remove hydrogen atoms.
Oxidases: Facilitate oxidation-reduction.
Isomerases: Rearrange molecular structures.
ATP Structure, Processes and Storage?
Structure: High-energy phosphate molecule.
Processes:
- Synthesis: ADP + Pi → ATP.
- Breakdown: ATP → ADP + Pi + Energy.
Storage: Limited intramuscular stores; sufficient for <2 seconds of all-out exercise.
Anaerobic ATP Production Pathways?
Anaerobic Pathways (Do not require oxygen): Usually in cytoplasm, uses PCr, Glucose, Glycogen, Glycerol, Some delaminated, amino acids
ATP-PC System (Phosphagen System):
- Fastest ATP production (single enzyme: creatine kinase).
- Dominates <10–15 sec of high-intensity activity.
- Reaction: PCr + ADP → ATP + Creatine
Glycolysis (Anaerobic):
Occurs in two phases:
- Energy investment phase
- Energy generation phase
- Substrates: Glucose, Glycogen
(Also minor contributions from glycerol, some amino acids) - Pathway Overview:
Glycogen → Glucose-6-Phosphate → Pyruvate →
If anaerobic: → Lactate
If aerobic: → Enters mitochondria
Net ATP Yield:
- 2 ATP (from glucose)
- 3 ATP (from glycogen)
By-products:
- 2 NADH
- 2 Pyruvate or 2 Lactate
High ATP hydrolysis by-products (like ADP, Pi) stimulate glycolytic flux.
Aerobic ATP Production Pathways?
Requires oxygen and primarily occurs in the mitochondria.
Utilizes several fuel sources:
- Fatty acids
- Pyruvate (from glucose via glycolysis)
- Some deaminated amino acids
Involves two main processes:
- Citric Acid Cycle (Krebs Cycle) – generates high-energy electron carriers (NADH, FADH₂)
- Electron Transport Chain (ETC) – uses those carriers to produce ATP through oxidative phosphorylation
This pathway is slower than anaerobic processes but produces much more ATP and supports sustained, long-duration exercise.
Citric Acid Cycle (Krebs Cycle)?
Pyruvate (from glycolysis) → Acetyl-CoA → Citrate
Net gain = - 1 ATP per cycle, 3 NADH and 1 FADH2 for the ETC, CO2 as a byproduct.
Process
1. Glycolysis generates 2 molecules of
pyruvate
2. Pyruvic acid (3-C) enters the mitochondria
and is converted to acetyl-CoA (2-C), losing
a carbon (generating CO2)
3. Acetyl-CoA combines with oxaloacetate (4-
C) to form citrate (6-C)
4. Series of reactions to regenerate
oxaloacetate (generating 2 CO2 molecules).
5. Each turn of the cycle, 1 ATP molecule is
synthesized from guanosine triphosphate
(GTP: high-energy compound) with the
release of high-energy electrons (3 NADH
and 1 FADH2)
Interactions between metabolic fuels ?
Beta Oxidation: Process of oxidizing fatty acids to Acetyl-CoA
No focus on proteins as not major fuel - only 2%
Electron Transport Chain (ETC)?
- NADH and FADH2 donate electrons Which are passed along series of carriers (cytochromes).
- Coupled with Proton (H+) pumping into intermembrane space, this pump creates an electrochemical gradient.
- ATP is produced as protons diffuse back across the membrane, through ATP synthase channel, energy from this channel drives production of ATP.
- Oxygen is the final electron acceptor, combining with hydrogen forming water. This is vital as without OP is not possible.
Aerobic ATP Yield??
Total ATP per Glucose (Textbook Standard):
- 32 ATP
- 2 from Glycolysis (net)
- 2 from Krebs Cycle
- 28 from Oxidative Phosphorylation (mostly NADH/FADH₂)
Alternative Historical Value:
- Up to 38 ATP per glucose (older textbooks)
ATP Yield per Electron Carrier:
- 2.5 ATP per NADH
- 1.5 ATP per FADH₂
- (Older values: 3 ATP/NADH, 2 ATP/FADH₂)
Efficiency of Energy Conversion:
- 34% of glucose’s energy is converted into ATP
- Based on:
(32 molATP × 7.3 kcal/mol / 686 kcal/molglucose)
× 100 ≈ 34 %
Control of bioenergetics? Examples?
Biochemical pathways are regulated by very precise control systems which are:
Rate-Limiting Enzymes:
- Early-stage control in pathways.
- Regulated by ATP availability and modulators.
Examples:
- ATP-PC: Creatine kinase, ADP stimulates, ATP inhibits
- Glycolysis: PFK, AMP,ADP, Pi and Increase pH stimulate, ATP, CP, Citrate and decrease pH Inhibit
- Krebs: Isocitrate dehydrogenase, ADP, Ca+, NAD+ stimulate, ATP and NADH inhibit
- ETC: Cytochrome oxidase, ADP,Pi stimulate, ATP inhibits
Intensity and Duration influences on systems contribution of energy metabolism?
Short-term, High-Intensity Exercise (<5s):
- ATP-PC system dominates.
Moderate-Intensity Exercise (5–45s):
- Shift to glycolysis.
Longer Duration (>45s):
- Mix of anaerobic and aerobic systems.
Prolonged Exercise (>10 mins):
- Predominantly aerobic metabolism.
Hormonal Control of Substrate Mobilization?
During exercise or periods of energy demand, the body must rapidly access fuel sources to supply muscles and organs. Hormones act as chemical messengers that regulate this process
Hormones regulate the mobilization of:
- Glucose from liver glycogen.
- Free Fatty Acids (FFA) from adipose tissue.
Key hormone types:
- Slow-acting (Permissive) hormones: Thyroxine, cortisol, and growth hormone.
— Prepare tissues to respond by upregulating enzymes and receptors - Fast-acting hormones: Epinephrine, norepinephrine, insulin, and glucagon.
— Rapidly adjust metabolism during stress or exercise by promoting glycogen breakdown, fat release, or glucose uptake
4 Key processes to maintain blood Glucose Homeostasis During Exercise ?
- Liver glycogen mobilization→ Releases glucose.
- FFA mobilization from adipose tissue→ Spares blood glucose.
- Gluconeogenesis→ Formation of glucose from non-carbohydrate sources.
- Blocking glucose entry into cells→ Encourages fat metabolism
Key Hormonal Regulators? Role?
• Thyroid Hormones (T3 & T4): Enhance effects of other hormones by increasing receptor number and affinity. T3 boosts epinephrine’s ability to mobilize fatty acids from fat stores (ineffective without T3). Levels remain stable during exercise, but hypothyroidism impairs hormone-driven fuel mobilization and lowers metabolic rate.
• Growth Hormone (GH): Promotes fat use, protein synthesis, and long bone growth, while reducing glucose use—helping preserve blood glucose during exercise. GH rises with intensity; e.g., after 60 mins at 60% VO₂max, levels are 5–6× higher than at rest. Used medically (e.g., childhood dwarfism), but high doses have adverse effects. No solid evidence it boosts strength or has anti-aging benefits; use is hard to detect in athletes.
• Cortisol: A steroid hormone from the adrenal cortex that helps maintain blood glucose. Stimulated by stress (via ACTH) and exercise. Levels rise with intensity and vary by time of day (highest in the morning). Effects are slow, acting through gene expression, likely contributing more to post-exercise tissue repair than immediate fuel mobilization
Functions of Catecholamines (Epinephrine & Norepinephrine)?
Released from the adrenal medulla as part of the “fight or flight” response
Fast-acting hormones that:
- Increase heart rate (HR)
- Elevate blood pressure (BP)
- Boost metabolic rate
Act on alpha (α) and beta (β) adrenergic receptors
- Specific effects vary depending on the hormone and receptor type
Catecholamines (Epinephrine & Norepinephrine) during exercise? Actions? Adaptations?
Catecholamines (epinephrine & norepinephrine) rise with exercise intensity and activate the sympathetic nervous system (SNS).
Key Actions:
- Act via cyclic AMP/adenylate cyclase pathway.
- β1 receptors → stimulate glycogenolysis & lipolysis.
- β3 receptors → stimulate lipolysis.
- Increase heart rate, blood pressure, and vascular tone.
Training Adaptations:
- Trained individuals have ~35% greater catecholamine capacity.
- Chronic endurance training reduces SNS response to a fixed workload.
- Plasma glucose remains more stable in trained individuals; SNS fine-tunes hormone secretion instead.
Catecholamines Links to glycogen depletion?
- Glycogenolysis and Exercise Intensity
- Higher exercise intensity → faster & greater glycogen depletion.
- Glycogenolysis is strongly linked to how hard you’re working.
- Role of Epinephrine (a catecholamine)
- Stimulates glycogen breakdown:
- Inhibits insulin (reduces glucose uptake/storage)
- Enhances glucagon (promotes glucose release)
- Result: Increased blood glucose to fuel activity.
- Plasma Epinephrine & Exercise
- Intense exercise → higher levels of plasma epinephrine.
- Correlates with increased glycogen breakdown.
- Control of Muscle Glycogen Breakdown
Redundant control system:
- Both local (muscle-based) and systemic (hormonal, e.g., epinephrine) pathways exist.
- Glycogenolysis can occur without epinephrine, but epinephrine still enhances it.
Role of Pancreas?
The pancreas has both exocrine (via ducts) and endocrine (directly into the blood) functions.
Its endocrine role involves secretion of key counter-regulatory hormones from the islets of Langerhans:
Insulin (from β-cells):
- Promotes glucose uptake and storage in tissues.
- Decreases during exercise to allow glucose mobilization for energy.
- Drives uptake and storage of substrates (e.g., glucose, fatty acids), lowering their levels in the plasma.
Glucagon (from α-cells):
- Promotes glucose release (from glycogen) and gluconeogenesis (glucose formation from non-carb sources).
- Increases during exercise, though this response may be blunted in trained individuals.
The glucagon-to-insulin ratio is crucial in regulating the mobilization of glucose and free fatty acids (FFA) during exercise and fasting.
Energy Requirements at Rest?
At rest, almost 100% of ATP is produced via aerobic metabolism.
Blood lactate levels remain low, typically below 1.0 mmol/L, indicating minimal anaerobic activity.
Resting oxygen consumption (VO₂):
- Absolute VO₂: ~0.25 L/min
- Relative VO₂: ~3.5 mL/kg/min → defined as 1 MET (Metabolic Equivalent of Task)
Rest-to-Exercise Transitions?
ATP production increases immediately when exercise begins to meet rising energy demands.
Oxygen uptake (VO₂) rises rapidly, with steady-state typically reached within 1–4 minutes depending on intensity and fitness level.
Once steady-state is achieved, aerobic metabolism becomes the primary source of ATP.
However, during the initial moments of exercise, anaerobic pathways provide most of the ATP:
- ATP-PC system (phosphocreatine breakdown)
- Glycolysis (anaerobic breakdown of glucose)
This early reliance on anaerobic systems creates an oxygen deficit—a temporary mismatch between oxygen demand and oxygen supply.
