·         Molecular Formula (C8H10N402)

·         Caffeine and adenosine have similar structures, which allows it to bind to adenosine receptor

https://link.springer.com/referenceworkentry/10.1007%2F978-3-319-20790-2_30-1

3. How is caffeine formed and used in nature? 
How caffeine is formed?

·         Caffeine is a stimulant drug that result from millions of years of plant evolution.

·         A natural alkaloid that can be found in about sixty plant species, the most common are coffee bean, tea leaf, kola nut, and the cocoa bean

·         A single mutation occurred, which was then replicated.

Mutations occurred for many times until caffeine was produced as a byproduct.

How caffeine is used in nature?

As pesticide

·         To repel insect from damaging plants

·         Inhibits enzymes in herbivorous insects’ nervous system, triggering paralysis and even death

·         But it also can harm other animals who ingest the plant or contaminate water supplies

 

4. What are common physiological effects of caffeine consumption? 

 - Physiological effects are those that result from some imbalance to the overall human system, or some specific part of it. 

- Activities which affect organs and systemic functions without regard to a particular disease

 -Caffeine is central nervous stimulant

 

1)    CENTRAL NERVOUS SYTEM

 

·         Can cause alertness (feel more awake, focus, less tired)

·         Manage drowsiness, headache and migraine

·         However if caffeine tolerance suddenly stop consuming it, caffeine withdrawal can occur

The symptom of caffeine withdrawal includes:

§  Anxiety

§  Irritability

§  Drowsiness

§  Achy muscle 

 

·         It is best to reduce consumption slowly rather than immediately

·         Thy symptom of caffeine overdose includes

§  Confusion

§  Hallucination

§  Vomiting

§  Irregular heartbeat and breathing trouble

 

 

2)    DIGESTIVE AND EXCRETORY SYSTEM

 

·         Increase the amount of acid in the stomach (cause hearburn or upset stomach)

·         Increase in urination

 

 

3)    CIRCULATORY AND RESPIRATORY SYTEM

 

·         Can increase blood pressure for a short time 

·         For people that have irregular heart rhythms, caffeine may increase workload for the heart

 

 

4)    SKELETEL AND MUSCULAR SYSTEM

 

·         Can cause bone thinning (osteoporosis) as caffeine in excess amount interfere with absorption and metabolism of calcium

 

 

5)    REPRODUCTIVE SYSTEM

 

·         Cause baby’s heart rate and metabolism to increase

·         Cause slow fetal growth if too much consume

·         Cause miscarriage if too much consume

·         Can interfere with estrogen production and metabolism needed to conceive

·         limit caffeine consumption between 200 and 300 milligrams per day if you’re trying to get pregnant.

 

 

, uric acids, di- and trimethylallantoin, and uracil derivatives. In humans 3-ethyl demethylation to paraxanthine is the primary route of metabolism. This first metabolic step accounts for approximately 75–80 percent of caffeine metabolism and involves cytochrome P450. The enzyme responsible for metabolism of caffeine is coded for by the gene CYP1A2 in liver.

 CYP1A2 catalyzes the 1-, 3-, and 7- demethylations of caffeine, the 7-demethylation of paraxanthine, and the 1- and 3-demethylations of theophylline. CYP1A2 is virtually responsible for most of the biochemical reactions concerning caffeine and its metabolites. Caffeine biotransformation by CYP1A2 accounts for a mean value of 84% for paraxanthine, 12% for theophylline, and 4% for theobromine. On the other hand, CYP2E1 is predominantly responsible for the formation of theophylline and theobromine. CYP2D6-Met also catalyzes caffeine demethylation and 8-hydroxylation, whereas CYP2E1 plays a more minor role in these pathways. CYP3A4 predominantly mediates 8-hydroxylation and may be involved in the in vivo synthesis of 1,3,7-TMU (trimethylurea). Thus, at least four CYP isoforms contribute to caffeine metabolism at a 3 μmol/ml caffeine concentration

 
These metabolites are then further broken down and excreted in the urine.
https://scihub.se/10.1124/pr.117.014407

2. Discuss on how Alex is not as affected by caffeine than Jenna. Could it be because he metabolizes caffeine differently than Jenna?
Yes. Someone who produces a very active version of the CYP1A2-enzyme will metabolise caffeine quickly, and it will have a shorter-lasting and mild effect throughout the body. Smokers often have increased CYP1A2 activity.(Alex). 

In contrast, a person with a less active version of the CYP1A2-enzyme will inactivate caffeine more slowly and retain it in the body for longer, and therefore experience longer-lasting and more pronounced effects(Jenna)

Adenosine A2 receptors are key to the stimulating effect of caffeine . Human studies have shown that polymorphisms of these receptors may have an effect on the body. Research suggests that the probability of having the ADORA2A genotype decreases as habitual caffeine consumption increases, meaning that individuals with this genotype may be less sensitive to the effects of caffeine and therefore be more likely to choose caffeinated beverages
https://www.coffeeandhealth.org/topic-overview/caffeine-and-metabolism/

-      Adenosine acts in the basal forebrain as sleep homeostasis. Extracellular adenosine concentrations increase during wakefulness especially during prolonged wakefulness and and lead to increased sleep and subsequent rebound sleep. 

-      Adenosine in basal forebrain acts via adenosine A1 receptors that inhibit the cholinergic neurons and provide input to the cerebral cortex. 

-      A2a receptor also implicated in sleep as A1 receptor involve normal sleep pattern and exhibit rebound sleep which affected by caffeine

-      Highly amount of adenosine in brain by breakdown of ATP to produce energy, then adenosine can bind to the adenosine receptor and make us sleep. 

https://chem.ku.edu/sites/chem.ku.edu/files/docs/CHEM190/caffeine.pdf

a. caffeine acts as an adenosine receptor antagonist.
b. it binds to adenosine receptors on the surfaces w/o activates them ( the molecule is a competitive inhibitor for adenosine)
c. when molecules bind with adenosine receptor , adenosine is blocked from attaching to them and cannot cause response of sleepiness.
d. caffeine binding to adenosine receptor causes the opposite effect which nerve cell activity speeds up, and brain blood vessels constrict. it prevents us from tiredness.
e. when caffeine binds to adenosine receptor, the pituitary gland of brain will regulates the release of hormones and increase the activity of signal to produce adrenaline or epinephrine.
f. caffeine blocking adenosine receptors is an increase in the neurotransmitter dopamine.
g. dopamine function is improves focus and attention, regulate the movements.

2. WHAT EFFECTS WOULD CAFFEINE HAVE? when adenosine levels rise and adenosine acts on its receptor to inhibit other neurons
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2769007/pdf/CN-7-238.pdf
https://thebrain.mcgill.ca/flash/a/a_11/a_11_m/a_11_m_cyc/a_11_m_cyc.html
-when adenosine levels rise up
in basal forebrain, extracellular adenosine level start to rise up due to prolonged activity during wakeful period., thus associated with depletion of ATP that reserves as glycogen in the brain
-lead of decrease neuronal activity which cause blood dilate to give good oxygenation during sleep.
-it inhibit cholinergic and noncholinergic neurons which decrease acetylcholine when adenosine receptor level is rise

The accumulation of adenosine in the body is related to the quantity of caffeine consumed during the day. By drinking beverages with high levels of caffeine, the body builds up an excessive amount of adenosine. Often this excess is not fully flushed from the body during sleep. This surplus of adenosine, therefore, contributes to the grogginess many suffer each morning. This feeling encourages people to load up on more caffeine. And on and on it goes! It’s a vicious cycle that results in poorer sleep and feeling tired all day.
https://www.sleepscore.com/blog/learn-about-adenosine/

https://pubmed.ncbi.nlm.nih.gov/1356551/
mechanism of action of caffeine on the CNS system
1. mobilization of intracellular calcium
- caffeine prolongs during the active period muscle contracting by promoting translocation of calcium through plasma membrane.
- caffeine in high concentration will interfere with the uptake and storage of calcium and increase the translocation of Ca2+ ion through plasma membrane.

2. inhibition of phosphadiesterases
- caffeine increase intracellular concentrations of cyclic adenosine monophosphate (cAMP) by inhibit phosphodiesterase enzymes in skeletal muscle and adipose tissue.
- it promotes the lipolysis via the activation of hormone sensitive lipases with release the free fatty acid and glycerol
- accumulation of cAMP stimulates the action of catecholamines
-cAMP is a second messenger that used for intracellular signal transduction (transferring into cells the effects of hormone like glucagon and adrenaline)

3. antagonism at the level of adenosine receptor
- caffeine inhibit adenosine receptor and release of norepinephrine,dopamine,acetylcholine,serotonin ,glutamate and gamma-aminobutyric acid(GABA) and perhaps neuropeptides
- main classes of adenosine receptor : a1 and A2 which caffeine acts as nonselective antagonists
- when caffeine bind to adenosine receptor, it increases the neuronal activity which causes blood vessel constrict --> prevent sleepiness.
-when neuronal activity increase, adrenaline increase, increase heartbeat,excitation and energy
- DOPAMINE- release and increase the focus, attention, regulating movement--> increase fell pleasure and stimulate us to do pleasurable thing --> dependency on caffeine

4. interaction with benzodiazepine binding
- caffeine more potent antagonism of adenosine receptor than benzodiazepine sites
-affinity of caffeine is weak ;- due to competition of two substances at the benzodiazepine receptors.
-toxic effects of high doses of caffeine can occur due to interaction with benzodiazepine receptor.

https://www.ncbi.nlm.nih.gov/books/NBK223808/

additional information
d. other effect of caffeine
- decrease in plasma potassium concentration
- increase coronary blood flow  via phosphodiesterase inhibition
-smooth muscle relaxation and bronchial dilation
- increase the blood flow, diuresis on kidney


3. HOW DOES CAFFEINE GET INTO THE THE BRAIN?

a. caffeine is both water and fat soluble which allows it pass through all membranes easily.
b. it attaches to a transporter that associated with adenosine.
c. due to the similarity structural of adenosine , adenosine acts inhibitory neurotransmitter or CNS depressant. it binds to neurotransmitter in the brain and binding which create a pathway that slows the activity of nerve cells and cause the brain blood vessel to dilate, and lead to drowsiness.
d. when adenosine enter the brain, it will bind with the specific receptors. however, caffeine is so close in structure with adenosine which can bind to the receptor which specific to adenosine.
e. but the affinity of caffeine higher than adenosine receptor which makes strong antagonist.
f. similar adenosine and caffeine ;- built up from 2 ring system (purines) (pyrimidine & imidazole ring)
caffeine has  alkene, amide, amine, carbonyl ( soluble in water)
fat soluble from 3 methyl group on the surface of caffeine,  trimethylxanthine
adenosine has amine, ether, imine, hydroxyl
(caffeine being competitive antagonist of adenosine)

https://www.acs.org/content/acs/en/education/resources/highschool/chemmatters/past-issues/archive-2013-2014/caffeine.html

https://examine.com/nutrition/how-caffeine-works-in-your-brain/

https://chem.ku.edu/sites/chem.ku.edu/files/docs/CHEM190/caffeine.pdf

-       A GPCR is made up of a long protein that has three basic regions: an extracellular portion (the N-terminus), an intracellular portion (the C-terminus), and a middle segment containing seven transmembrane domains.
-       Mediate most of the physiological responses of hormones, neurotransmitters and environmental stimulants
-       Can regulate immune system, growth, sense of smell, taste, visual, behavior, mood
-       The adenosine receptor (A2A) is a G-protein coupled receptor, which is a transmembrane protein that consists of secondary structures, such as seven alpha helical domains. When caffeine binds to this receptor, it inhibits adenosine from binding to the extracellular binding domain of the A2A receptor.

Where are these receptors located in the cell?
Located in cell membrane of a wide range of organisms, including mammals, plants, microorganisms, and invertebrates
https://www.britannica.com/science/G-protein-coupled-receptor

How do they work? Draw a diagram. (summarization)

- GPCR has seven transmembrane alpha helices (unique characteristic)

- G Proteins is a specialized protein that can bind to GDP and GTP

- G Proteins associated with GCPR are heterotrimeric meaning that they have three different subunits (alpha, beta, gamma subunits)

Steps of signal transducing pathway:

1.    Ligand binds to GCPR

2.    GPCR undergoes conformational change

3.    Alpha subunit exchanges GDP for GTP

4.    Alpha subunit dissociates and regulates target proteins, beta dimer subunit also regulate another protein

5.    Target protein relay a signal 

6.    GTP is hydrolyzed to GDP, GTP loses a phosphate in hydrolysis and become GDP, turns to normal, ligand leave

 2. What is an antagonist for a receptor? What would an antagonist do? Draw a diagram to explain this.

3. Discuss potency and efficacy. Use caffeine vs adenosine in your discussion
Potency caffeine vs adenosine
depends on the affinity of the receptors to bind the drug and how effectively the drug-receptor interaction leads to clinical response.
- Caffeine causes most of its biological effects via antagonizing all types of adenosine receptors (ARs): A1, A2A, A3, and A2B and, as does adenosine, exerts effects on neurons and glial cells of all brain areas
- Caffeine, through antagonism of ARs, affects brain functions such as sleep, cognition, learning, and memory, and modifies brain dysfunctions and diseases
- Caffeine acts most potently at A2A receptors, followed closely by A1 receptors, then A2B receptors, and as a weak antagonist at human A3  receptors.
- Adenosine A and A_2A receptors are characterized by high affinity for adenosine, while A_2B and A₃ receptors show significantly lower affinity for adenosine.
- Adenosine initiates its biological effects via four receptor subtypes, namely the A1, A2A, A2B and A3. The A1 and A2A possess high affinity for adenosine while the A2B and A3 show relatively lower affinity for adenosine receptors. These receptors belong to the superfamily of G protein-coupled receptors (GPCR).
- A1 receptor and A2A play roles in the heart that regulate mycordial oxygen consumption and coronary blood flow. A2A receptor also has broader anti-inflammatory effects in the body.

 https://blogs.scientificamerican.com/observations/is-there-really-a-difference-between-drug-addiction-and-drug-dependence/
- Do not  keep taking drug to satisfy craving and get pleasurable effect.

- Do not keep taking the drug to the point where they do not care about the harmful effect to themselves.

drug addiction
- Drug addiction, also called substance use disorder, is a disease that affects a person's brain and behavior and leads to an inability to control the use of a legal or illegal drug or medication. Substances such as heroine, marijuana and nicotine also are considered drugs. When you're addicted, you may continue using the drug despite the harm it causes.
- Addiction is a health condition in which you have strong cravings for a certain substance. These cravings occur due to physical changes in your brain after repeated exposure to a drug. These cravings can lead to uncontrolled drug use, which takes a toll on your health, relationships, career, finances, and other aspects of your life. Being addicted to drugs can cause you to engage in self-destructive behavior or make decisions that hurt other people, such as taking dangerous risks or acting in an aggressive manner toward others.

https://www.mayoclinic.org/diseases-conditions/drug-addiction/symptoms-causes/syc-20365112
- Keep taking drug to satisfy craving and get pleasurable effect.

- Keep taking the drug to the point where they do not care about the harmful effect to themselves.

2. Explain the mechanism by which adenosine contributes to caffeine dependence or

addiction.
- As we know, adenosine binds to its receptors which is located at neural membrane will cause neural activity slows down, and you feel sleepy. Mostly, people who want to stay up late doing work or want to fell fresh early in the morning are taking caffeine. This is because caffeine can make us feel energetic and increase our alertness and these are why people will keep on depending to caffeine. This can happens due to the fact that caffeine, a methylxanthine, is a nonselective adenosine receptor antagonist that can bind to adenosine receptors and block adenosine from binding to its receptor.  Whenever people who always take caffeine start to stop taking caffeine, they will get affected by the withdrawal symptoms such as headache, dizziness or nausea. One of the withdrawal symptoms is fatigue. This can happen because adenosine can bind back to its receptors because of no presence of caffeine. Therefore, people will keep taking caffeine to prevent the caffeine withdrawal symptoms which are worse and last longer at least 2 to 9 days. This leads to the caffeine dependence and it is not a substance use disorder like drug addiction that involving cocaine.

3. Explain how dopamine can contribute to caffeine dependence or addiction.

-Dopamine is a neurotransmitter and is released when your brain is expecting a reward. That is why, it contributes to a pleasure feeling. Other than that, it can also increase an alertness, focus, motivation.

https://www.healthline.com/health/dopamine-effects#definition
- Dopamine works more effectively when the adenosine receptors are blocked. A previous study reported that caffeine can induce marked changes in certain behaviors, including high level of alertness and poor sleep, in humans. This effect was associated with an increase in the availability of dopamine receptors. 

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7132598/
- Caffeine causes an increase of dopamine within the brain, but it is not a large enough  to cause unbalance the reward system in the brain , such as amphetamines and cocaine that stimulate the area of the brain linked to reward and motivation to a higher extent than caffeine does. 

- That is why caffeine addiction that happen to people who always consume caffeine is not classified as substance use disorder as the dopamine effect caused by caffeine is weaker than other stimulants such as cocaine.