Energy systems - Chemical and food fuels Flashcards
(20 cards)
What are the body’s three energy systems?
ATP-PC
Anaerobic glycolysis
Aerobic glycolysis
which energy systems don’t use oxygen?
ATP-PC and anaerobic glycolysis
what does rate refer to?
how fast ATP can be broken down and resynthesised
what does yield refer to?
the amount of ATP produced
what is the ATP-PC system?
Fuel: ATP and phosphocreatine (PC)
Oxygen: Not required (anaerobic)
Rate: Fastest
Yield: Very low (0.7 ATP per PC)
Duration: 0–10 seconds
Used for: Short, explosive efforts (e.g. sprint, jump)
what is the anaerobic glycolysis system?
Fuel: Glucose
Oxygen: Not required (anaerobic)
Rate: Fast
Yield: Low (2 ATP per glucose molecule)
Duration: 10–60 seconds
By-product: Lactic acid
Used for: High-intensity efforts (e.g. 400m run, repeated sprints)
what is the aerobic energy system?
Fuel: Glucose, fats (and sometimes protein)
Oxygen: Required
Rate: Slowest
Yield: High (36–38 ATP per glucose)
Duration: 60 seconds to hours
By-products: CO₂, water, heat (non-fatiguing)
Used for: Long-duration, low to moderate intensity (e.g. distance running, cycling)
what is ATP?
ATP stands for Adenosine Triphosphate.
It’s the energy currency of the body, all movement and bodily functions need ATP to happen.
ATP is made of adenosine + 3 phosphate groups.
When the bond between the last two phosphate groups breaks, energy is released, and the body uses that energy to fuel movement.
What is ADP?
ADP stands for Adenosine Diphosphate.
It’s what’s left after ATP is broken down and energy is released.
ADP = Adenosine + 2 phosphates
To make energy again, your body has to add a phosphate back to ADP using the ATP-PC, Anaerobic Glycolysis, or Aerobic system.
What is CP?
CP stands for Creatine Phosphate. It’s a high-energy compound stored in muscles that quickly resynthesises ATP during short, high-intensity activities (e.g. sprinting, jumping).
It is the main fuel for the ATP-CP energy system, lasting about 0-10 seconds.
what are carbohydrates?
Carbohydrates are the body’s preferred source of fuel, especially during high-intensity and aerobic activities. They’re broken down into glucose and stored as glycogen in muscles and the liver.
sporting examples: 400m sprint, Soccer match, Middle-distance running (e.g. 1500m)
What are Fats?
Fats are a long-lasting energy source used mainly during rest and low-intensity, long-duration aerobic exercise.
They provide lots of energy (high yield) but are slow to break down.
sporting examples: Marathon running, Triathlon, Long-distance cycling
What is Protein?
Protein is primarily used for muscle repair and growth, but in extreme conditions (e.g. prolonged exercise or fasting), it can be broken down into amino acids and used for energy.
It’s a last-resort fuel.
sporting examples: Ultra-marathons (when glycogen and fats are depleted), Endurance cycling (long, extended rides), Ironman triathlon (when energy stores run low)
Food sources of carbohydrates?
Bread (especially white and whole grain)
Rice (white and brown)
Pasta
Cereal (e.g., oats or muesli)
Fruits (e.g., bananas, apples, grapes)
Vegetables (e.g., corn, peas, carrots)
Food sources of fats?
Avocados
Olive oil (and other vegetable oils)
Nuts (e.g., almonds, walnuts, cashews)
Seeds (e.g., chia seeds, flaxseeds, sunflower seeds)
Butter
Cheese
Food sources of protein?
Chicken
Beef
Fish (e.g., salmon, tuna)
Eggs
Legumes (e.g., beans, lentils, chickpeas)
what is glycogen?
Carbohydrates are consumed in foods and drinks then digested and broken down into glucose which can be used as a fuel. Glycogen is the stored form of glucose in the muscles and liver.
what is oxidation?
Oxidation is when the body uses oxygen to break down fuels (like glucose and fats) to make energy. It also removes H⁺ ions by turning them into water, helping with recovery and reducing muscle acidity.
What is the crossover point?
The crossover point is when the body switches from using fats to carbs (glucose) as the main fuel during exercise.
It happens as intensity increases, because carbs are quicker to break down for energy than fats.
What is inorganic phosphate (Pi)?
Inorganic phosphate (Pi) is a free-floating phosphate molecule in the body.
It comes from breaking down ATP and creatine phosphate (CP) to release energy.
Too much Pi in muscles can contribute to fatigue.
