review metabolism Flashcards
(61 cards)
What is the primary role of carbohydrates in cellular respiration?
Carbohydrates break down into simple sugars like glucose, which is the main reactant in glycolysis. Glucose is converted into pyruvate, which forms acetyl-CoA, entering the Krebs cycle to produce ATP.
How does the body store excess carbohydrates?
Excess carbohydrates are stored as glycogen in liver and muscle cells. Glycogen can be hydrolyzed back into glucose when energy is needed.
Why are complex carbohydrates recommended over refined ones?
Complex carbs provide fiber and vitamins, while refined carbs lack these nutrients and spike blood sugar more quickly.
How are fats metabolized to produce ATP?
Fats are broken down into glycerol and fatty acids. Glycerol becomes PGAL and enters glycolysis. Fatty acids are converted into two-carbon fragments (via β-oxidation) to form acetyl-CoA, which enters the Krebs cycle to generate ATP.
Why do fats produce more ATP than carbohydrates?
Fats are more reduced, meaning they contain more hydrogen atoms per molecule, allowing them to generate approximately 2x more ATP per gram than carbohydrates.
What types of fats are considered healthier?
Unsaturated fats (e.g., olive oil, canola oil) are healthier than saturated fats (e.g., butter, margarine), which can raise cholesterol levels.
What happens to proteins in the body?
Proteins are broken down into amino acids, which can be converted to glucose or glycogen, become pyruvate or enter as intermediates in the Krebs cycle, or be stored as fat.
What are common dietary sources of protein?
Meat, poultry, fish, eggs, dairy, beans, peas, nuts, pasta, and cereal.
Why is it dangerous to restrict food too much for weight loss?
Severe food restriction can impair metabolic processes, reduce essential nutrient intake, and cause the body to break down muscle and fat inefficiently.
Why might a low-fat diet not lead to fat loss?
If excess carbohydrates are consumed, glucose can be converted into fatty acids and glycerol, then stored as fat.
What is the danger of a low-carbohydrate diet?
It forces the body to rely on fat metabolism, producing ketones as byproducts. Excessive ketone buildup can cause ketosis and may lead to ketoacidosis.
How do various macromolecules enter cellular respiration?
- Glucose → glycolysis
- Glycogen → glucose → glycolysis
- Fatty acids → acetyl-CoA
- Glycerol → PGAL → glycolysis
- Amino acids → glucose, pyruvate, or Krebs intermediates
What is β-oxidation?
It is the breakdown of fatty acids into acetyl-CoA, which then enters the Krebs cycle for energy production.
What is gluconeogenesis?
It’s the metabolic process of creating glucose from non-carbohydrate sources like amino acids or glycerol, often in the liver.
What is glycolysis?
The anaerobic breakdown of glucose into pyruvate, producing ATP and NADH in the cytoplasm.
What is fermentation?
An anaerobic process that converts pyruvate into lactic acid or ethanol to regenerate NAD⁺.
What occurs during lactic acid fermentation?
In animal cells, pyruvate becomes lactic acid, allowing NADH to be recycled to NAD⁺.
What occurs during alcoholic fermentation?
In yeast, pyruvate becomes ethanol and CO₂, recycling NADH to NAD⁺.
Where does the Krebs Cycle occur?
In the mitochondrial matrix.
What does the Krebs Cycle produce?
- NADH
- FADH₂
- ATP
- CO₂
What is the final electron acceptor in the electron transport chain?
Oxygen (O₂) accepts electrons and H⁺ to form water (H₂O).
What is ATP Synthase?
An enzyme that uses H⁺ gradient to convert ADP and Pi into ATP during chemiosmosis.
What is the Calvin Cycle?
Light-independent reactions in the stroma that fix CO₂ into glucose using ATP and NADPH.
What is Rubisco?
The enzyme that catalyzes the fixation of CO₂ to RuBP in the Calvin Cycle.
