Summary: Medical Biochemstry

Read the summary and the most important questions on Medical Biochemstry

• 1 Lectures block 1

• 1.4 Fat & lipid metabolism

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• The storage of what substance has no limit in the human body?

  The storage of fat.

• What are the three essential nutrients that provide the body with caloric energy?

  Protein, carbohydrates, and fats

• After uptake from the food, how are triglycerides packaged, and why?

  - Triglycerides are packaged into chylomicrons,
  - to surpass the liver, so that it is actually used for storage in the muscles and adipose tissue, instead of being broken down into something else)

• How is the fat that is produced from the excess of carbohydrates and proteins transported, and where is it stored?

  - The fat is packaged into VLDL,
  - and the VLDL also goes to muscle and adipose tissue

• What are the steps of β-oxidation?

  1. CoA is connected to the fatty acid, to form a complex called fatty acyl-CoA
  2. This fatty acyl-CoA is unable to enter the inner mitochondria, because of the CoA. Therefore, the CoA is replaced by carnitine, and the fatty acid enters the inner mitochondria.
  3. The complex is again transformed into fatty acyl-CoA.
  4. For palmitate (C16), 7 spirals in β-oxidation follow. 8 acetyl-CoA (2C) is left.

• On these steps of β-oxidation are a few exceptions. What happens to very long-chain fatty acids?

  They need chain-shortening.

• On these steps of β-oxidation are a few exceptions. What happens to unsaturated fatty acids?

  They need extra steps.

• On these steps of β-oxidation are a few exceptions. What happens to odd-chain fatty acids?

  - Instead of only acetyl-CoA molecules, 1 propionyl-CoA (3C) is left.
  - Propionyl-CoA can be converted into succinyl-CoA, which is part of the citric acid cycle.

• On these steps of β-oxidation are a few exceptions. In which type of cells β-oxidation cannot occur? How do these cells gain energy?

  - Brain-neuronal cells do not do β-oxidation,
  - they solely rely on glucose and ketone bodies.

• Which type of cells use ketone bodies as an energy source, and how can they be used as an energy source?

  - Ketone bodies are used by the brain, heart and muscle cells, but not by liver cells themselves (to prevent futile cycles)
  - Ketone bodies can be used as an energy source if they are broken down by the cells to 2 acetyl-CoA, which can enter the TCA