TEACHER / INSTRUCTORS NOTES
AIM: 1) Give general overview of the four major processes in chemistry: synthesis, decomposition, single replacement,
and double replacement to help students prepare for regions exam. The DO NOW assignment can be an introductory tool,
or a review / assessment tool.
2) Relate Synthesis to substances found in the body, such as the catecholamines (DA, NE, Epi), and show relevant
biochemical pathway for the synthesis of these transmitters/hormones. Give examples of the functions of each, and state
the relevance to the students’ lives in practical examples.
If students ask: “Why should I care how neurotransmitters or hormones such as the catecholamines are synthesized?”
Answer: “You will gain an understanding of how your body and brain manufacture and use chemicals that make you feel
things such as pleasure (food, sex, drugs, rock and roll) anxiety (fight or flight response), and pay attention and stay
focused (ADHD).
Points to discuss and write on board as we cover the material.
1) Catecholamines are manufactured / synthesized by specialized cells of the adrenal medulla (lies above the kidney)
and also by specialized cells of the CNS called neurons, located in the brain stem. (Can draw this part out).
Catecholamines are so named because they contain a catechol + an amine group.
2) Synthesis of the catecholamines takes place through several biochemical steps. What are the steps?
I. PHENYLALANINE: (PHE, or F, organic chemical) Precursor amino acid taken in through the diet. Found
in foods such as nuts, meats, chocolate. ASK: Have you ever heard that chocolate makes you feel good?
Well this is why – it is a precursor to the synthesis of a neurotransmitter called Dopamine which provides
you with pleasure.
II. PHENYLALANINE: is converted to TYROSINE by the enzyme PHENYLALANINE HYDROXYLASE
(note on tyrosine often being cited as precursor).
III. TYROSINE is converted to L-DOPA by the enzyme TYROSINE HYDROXYLASE (TH)
IV. L-DOPA is converted to DOPAMINE (DA) by AROMATIC L-AMINO ACID DECARBOXYLASE
(AADC).
 Dopamine (DA, C8H11NO2): Neurons that use DA contain only the two enzymes TH and
AADS. Therefore, the biochemical pathway of DA stops here. There are two major pathways
in the brain that utilize the chemical DA.
1. Nigrostriatal Tract: Important for control of movement. This is the pathway that is
damaged in Parkinson’s Disease (tremors, postural disturbances, difficulty in initiating
voluntary movements).
2. Mesocoroticolimbic Pathway: Important for learning the reward value of stimuli - this
pathway is activated during drug abuse, sexual activity, and eating. There are also
disturbances of function in this pathway in people who have Schizophrenia.
 BUT, now we turn to other neurons that use NE and Epi, because they contain additional
enzymes such as dopamine β-hydroxylase (DBH) that enable further conversions into NE and
Epi.
V. DA is converted to NOREPINEPHRINE (NE, a.k.a. noradrenaline, C8H11NO3) by DβH
VI. NE is converted into Epi (a.k.a. adrenaline, C9H13NO3) by the action of N-METHYL-TRANSFERASE
 NE: acts as a stress hormone, affecting parts of the brain where attention and responding
actions are controlled. Medication attempting to control ADHD target this chemical.
 EPI, along with NE mediates the fight-or-flight response by directly increasing heart rate,
triggering the release of glucose from energy stores, and increasing blood flow to skeletal
muscle.
 EPI also used therapeutically in cardiac arrest, or to reverse severe allergic reactions to antibiotics and other substances.
http://www.youtube.com/watch?aq=f&emb=0&eurl=http%3A%2F%2Fvideo.google.com%2Fvideosearch%3Fq%3Dcatecholamine+synthesis&v=r71RoIkftd4
http://www.youtube.com/watch?v=r71RoIkftd4
Do now: There are four major types of reactions that you should know about in chemistry.
1. Read the definitions of each type of reaction aloud, paying careful attention to the general formula given for each.
2. Each of the pictures below can be related to a specific type of chemical reaction. Circle the name of the type of
reaction that you think best fits what is taking place in the pictures.
3. Write the general formula for the type of the reaction in box to the left.
4. After working with the images and general formulas, try to work with real chemical equations.
Synthesis: Synthesis occurs when two or more reactants combine to form a single product. This means that two or more
elements can combine to form a compound, or two or more simple compounds can combine to form a more complex
compound. The general formula is: A + B  AB
Decomposition: Decomposition occurs when a single compound is broken down into two or more simpler substances. A
single compound can be broken down into simpler compounds, or it can be broken down into elements. The general
formula is: AB  A + B
Single Replacement: In this type of reaction, one “free standing” element replaces another element from a compound.
The replacement occurs because the “free standing” element is more reactive than the element it replaces in the
compound. Because the element is more reactive than the one it has replaced, the reverse action can never take place.
The general formula is: A + BX  B + AX
Double Replacement: In this type of reaction, parts of two compounds switch places to form two NEW compounds.
Two reactants yield two products. The general formula is: AB + CD  AD + BC
__________________
decomposition
synthesis
single replacement
double replacement
__________________
decomposition
synthesis
single replacement
double replacement
______________
decomposition
synthesis
single replacement
decomposition
synthesis
single replacement
double replacement
_________________
double replacement
Working with real chemistry!
Circle the type of reaction you think is taking place and write the general formula in the space to the left.
2H2 + O2  2H2O
decomposition
synthesis
2H2O  2H2 + O2
decomposition
synthesis
Zn + 2HCl  ZnCl2 + H2
decomposition
synthesis
___________________
single replacement
double replacement
___________________
single replacement
double replacement
___________________
single replacement
double replacement
AgNO3 + NaCl  AgCl + NaNO3 ___________________
decomposition
synthesis
single replacement
double replacement
NAME _________________________
DATE __________________
Catecholamine Synthesis: Fill in the blanks or circle the answers!
1) L-Tyrosine is an __ __ __ __ __ - __ __ __ __, which
acts as a __ __ __ __ __ __ __ __ __ to the synthesis of
the chemical L-DOPA.
2) Tyrosine hydroxylase is an __ __ __ __ __ __ that
acts as a __ __ __ __ __ __ __ __, which speeds up the
rate of chemical reactions.
3) L-DOPA is acted upon by an enzyme that converts it
to the neurotransmitter Dopamine (DA). Circle the
name of the enzyme in the figure to the left that
facilitates this chemical reaction.
4) L-DOPA is given to patients that have __ __ __ __ __
__ __ __ __’__ disease because it facilitates the
production of DA.
5) DA is important for normal __ __ __ __ __ __ __ __,
and for us to having feelings of __ __ __ __ __ __ __ __
from natural rewards such as food and sex, but also
from drugs of abuse.
6) DA β-__ __ __ __ __ __ __ __ __ __ __ is the
enzyme that converts DA into Norepinephrine (NE).
7) Circle the enzyme that converts NE into Epinephrine
(Epi).
8) NE and Epi are released by the adrenal medulla,
which is located on top of the __ __ __ __ __ __ __.
9) Epi circulates throughout the blood stream and acts as
a stress __ __ __ __ __ __ __ to increase things such as
heart rate, and to trigger glucose stores, as well as
increase blood flow to skeletal muscle.
10) The specific name for this type of response is the
__ __ __ __ __ __ - __ __ __ __ __ response.
11) The molecular formulas for DA, NE and Epi are
DA: _________
NE: _________
Epi: _________