respiration, fuels Flashcards
(50 cards)
What is β-oxidation?
The breakdown of fatty acids into 2-carbon Acetyl-CoA units for the Krebs Cycle.
How much ATP is produced from one fatty acid (e.g., palmitate)?
Approximately 106 ATP.
Can fatty acids be used under anaerobic conditions?
No, β-oxidation requires oxygen.
Why are amino acids deaminated?
To remove the nitrogenous group, allowing the remaining carbon skeleton to be used for energy.
What happens to ammonia after deamination?
It is converted to urea in the liver and excreted by the kidneys.
What are possible fates of the amino acid carbon skeleton?
Can be converted into pyruvate (gluconeogenesis) or Acetyl-CoA (Krebs/ketone bodies).
Why aren’t amino acids stored in the body?
There’s no storage form like glycogen or fat; excess is degraded.
What is the preferred fuel for the brain?
Glucose; shifts to ketone bodies during prolonged starvation.
What is the preferred fuel for red blood cells?
Glucose, because they lack mitochondria and rely on anaerobic glycolysis.
What is the preferred fuel for skeletal muscle?
Glucose (fed), fatty acids (resting), both (exercise).
What is the preferred fuel for the heart?
Fatty acids, ketone bodies, lactate.
What is the Warburg effect?
Cancer cells use high levels of glycolysis even in the presence of oxygen.
What characterises the fed state (0–4 hrs post-meal)?
ATP is made from meal nutrients; glucose stored as glycogen; excess carbs converted to fat.
What occurs during the fasting state (4–30 hrs)?
Liver uses glycogen, amino acids are used for gluconeogenesis, brain still uses glucose.
What occurs in the starvation state (>30 hrs)?
Liver makes ketone bodies, brain shifts to ketones, muscles use less glucose.
What are ketone bodies?
Carbon compounds (3+ C atoms) made from Acetyl-CoA, used by brain, heart, and muscles.
When are ketone bodies produced?
During starvation, post-exercise, or low-carb/high-fat diets.
What is diabetic ketoacidosis?
A dangerous condition in uncontrolled diabetes with high ketone levels and acidosis.
What is starvation ketoacidosis?
A result of glucose deprivation where the body depends on fats for energy.
Which tissues use ketone bodies?
Brain, heart, skeletal muscle.
How does glucose oxidation compare to fat oxidation in oxygen use?
Glucose uses about 5x less oxygen per ATP than fats.
What are the major energy stores in the body?
Primarily triglycerides in adipose tissue, followed by protein in muscle.
Which organ has the highest energy use per kg?
Heart and kidneys (~1,841 kJ/kg/day).
Why does the brain rely on glucose?
To maintain function; low glucose can cause symptoms like dizziness, sweating, and anxiety.
