Q 01/05

The enzyme that turns L-DOPA into dopamine also makes which other famous mood chemical?

A) Oxytocin

B) Cortisol

C) Serotonin

D) Endorphin

Answer · why

C) Serotonin

Serotonin comes off the same production line: one enzyme clips a carboxyl group from L-DOPA to give dopamine and from 5-HTP to give serotonin. Childre...

Q 02/05

Rather than pleasure itself, mainstream pharmacology holds that dopamine signals what?

A) Pain intensity

B) Motivational salience

C) Sleep pressure

D) Social bonding

Answer · why

B) Motivational salience

Motivational salience is how strongly an outcome grabs you, good or bad. One group of dopamine neurons fires for unpleasant events as well as for trea...

Q 03/05

Dopamine belongs to which chemical family, along with the stress hormones epinephrine and norepinephrine?

A) Endorphins

B) Cannabinoids

C) Indoleamines

D) Catecholamines

Answer · why

D) Catecholamines

Catecholamines are built in sequence: the body turns dopamine into norepinephrine and then into epinephrine, so the so-called reward chemical is also ...

Q 04/05

Dopamine synthesis starts with which essential amino acid, named in the warning on diet-soda cans?

A) Methionine

B) Phenylalanine

C) Isoleucine

D) Tryptophan

Answer · why

B) Phenylalanine

Phenylalanine is a building block of the sweetener aspartame. The label protects people with the inherited disorder PKU, who cannot break it down, whi...

Q 05/05

Which enzyme carries out the rate-limiting step of dopamine synthesis, turning an amino acid into L-DOPA?

A) Dopamine beta-hydroxylase

B) DOPA decarboxylase

C) Tyrosine hydroxylase

D) Monoamine oxidase

Answer · why

C) Tyrosine hydroxylase

Tyrosine hydroxylase sets the pace for the whole pathway. When dopamine builds up it latches onto the enzyme and slows it down, a built-in brake again...