10 Questions
What is the product of the enzyme phenylalanine hydroxylase?
Tyrosine
What is the deficiency of phenylalanine hydroxylase associated with?
Phenylketonuria
What is the role of tetrahydrobiopterin (BH4) in the metabolism of phenylalanine?
It is a cofactor for phenylalanine hydroxylase
What is the enzyme responsible for converting tryptophan to 5-hydroxytryptophan?
Tryptophan hydroxylase
What is the product of the enzyme tryptophan hydroxylase?
5-hydroxytryptophan
What is the role of dihydropteridine reductase in the metabolism of phenylalanine?
It reduces the quinonoid form of BH2 to BH4
What is the significance of the hypothalamus in the regulation of neurotransmitters?
It regulates the release of neurotransmitters from the hypothalamus
What is the role of antipsychotics in the regulation of neurotransmitters?
They decrease the release of dopamine
What is the role of N-methyltransferase in the metabolism of neurotransmitters?
It converts norepinephrine to epinephrine
What is the significance of TRH (thyrotropin-releasing hormone) in the regulation of neurotransmitters?
It regulates the release of prolactin
Study Notes
Phenylalanine Metabolism
- Phenylalanine is converted to tyrosine by phenylalanine hydroxylase, which requires tetrahydrobiopterin (BH4) as a cofactor.
- Deficiency of phenylalanine hydroxylase leads to phenylketonuria.
- Tyrosine can be converted to L-DOPA by tyrosine hydroxylase, which also requires BH4.
- L-DOPA is converted to catecholamines, such as dopamine, norepinephrine, and epinephrine.
Neurotransmitters
- Tryptophan is converted to 5-hydroxytryptophan by tryptophan hydroxylase, which also requires BH4.
- 5-Hydroxytryptophan is converted to serotonin (5-HT).
- Norepinephrine is converted to epinephrine by N-methyltransferase.
Hormone Regulation
- TRH (thyrotropin-releasing hormone) stimulates the release of TSH (thyroid-stimulating hormone) from the hypothalamus.
- Dopamine, VIP (vasoactive intestinal peptide), and TRH are involved in regulating prolactin levels.
- The hypothalamus and hypophyseal portal system are involved in regulating hormone levels.
Protein Transport
- Facilitated diffusion is a type of carrier-mediated transport that requires a protein transporter.
- Facilitated diffusion is saturable, meaning that there is a maximum transport rate.
- The presence of a protein transporter is necessary for facilitated diffusion.
- Simple diffusion does not require a protein transporter and has a linear relationship with solute concentration.
This quiz tests your understanding of protein transporters and their role in solute transport across the plasma membrane. It covers the concept of transport rate and its relationship with solute concentration.
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