3. Alcohol and Human Health

Question 1

What is another term for drunkenness?

Answer 1

Intoxication, from the Latin toxicum, a poison (as in toxic)

Question 2

A litre can be divided into…

Answer 2

100 centilitres (100 cl) or 1000 millilitres (1000 ml)

Question 3

If 12% of a 75 cl bottle of wine is pure alcohol, what is the volume of pure alcohol in the bottle?

Answer 3

Question 4

What volume of pure alcohol would you consume if you drank half a litre of beer with an alcohol content of 5%? Express your answer in millilitres (ml).

Answer 4

Question 5

What is binge drinking?

Answer 5

‘drinking to get drunk’

Question 6

What is alcoholic poisoning?

Answer 6

Intoxication so extreme that it leads to unconsciousness that can result in death

Question 7

What is alcoholic liver cirrhosis?

Answer 7

A chronic effect on individuals who regularly abuse alcohol.

The liver is so damaged by prolonged excessive consumption of alcohol that scar tissue replaces a large proportion of its normal structure. This severely impairs the liver’s ability to remove toxic substances (including alcohol) from the blood.

Question 8

What is the chemical name of alcohol?

Answer 8

Ethanol

Question 9

What are the two main types of chemical bonding?

Answer 9

1. Covalent bonding
2. Ionic bonding

Question 10

What is ionic bonding?

Answer 10

An atom can lose an electron (sometimes more than one) which is itself donated to the atom of another element.

The atom receiving the electron becomes negatively charged. This process of electron loss or donation is referred to as ionisation and the charged particles formed are known as ions.

The ions now have equal and opposite electrical charges and so attract one another and it is this electrical attraction which holds the salt crystals together.

Question 11

What is covalent bonding?

Answer 11

An outer electron from each of two adjacent atoms is shared between the two atoms, forming an electron­pair bond.

This type of bonding is called covalent bonding.

Question 12

What is the chemical formula and how does a structural fomula look like (for water)?

Answer 12

Chemical formula: H₂O

Structural formula: H-O-H

Question 13

What is the chemical formula of ethanol?

Answer 13

C₂H₅OH

Question 14

What is a -OH-part in a molecule called?

Answer 14

Hydroxyl group

Question 15

Explain the electrical charge of the atoms in a water molecule.

Answer 15

The oxygen is slightly negatively charged, and the hydrogen atom it is attached to slightly positively charged.

Question 16

Why does NaCl dissolve in water?

Answer 16

Sodium chloride contains Na+ ions and Cl− ions.

The slightly negatively charged end of the water molecule – the O atom – is attracted to the positively charged Na+ ion, and each Na+ ion becomes surrounded by a sphere of water molecules which encapsulate it.

The two ions (Na+ and Cl−) are now effectively separated from each other by the water molecules, and can act independently – this is the process of dissolving, and it is shown in the short animation below.

Question 17

Why does ethanol dissolve in water?

Answer 17

Because in both molecules there are –OH (hydroxyl) groups with uneven concentrations of electric charge, and so the molecules are weakly attracted to each other.

Question 18

Some atoms are better at attracting electrons to themselves than others: oxygen is one of these, and it is said to be…

Answer 18

electronegative

Question 19

What is hydrogen bonding?

Answer 19

H^d+ of one molecule is attracted to the O^d- of a neighbouring molecule.

The separation of charges on the -OH groups of both ethanol and water molecules means that these two molecules also form weak hydrogen bonds with each other, and so ethanol dissolves in water

Question 20

What means BAC?

Answer 20

Blood-alcohol concentration

It is usually quoted in mg/100 ml of blood.

Question 21

Ethanol is metabolised (broken down) in the liver in three stages. Which are those?

Answer 21

1. ethanol → acetaldehyde
2. acetaldehyde → acetic acid
3. acetic acid → CO₂ and + H₂O

Question 22

What is also needed for the metabolism of ethanol in the liver?

Answer 22

Enzymes

An enzyme is a molecule that has the ability to accelerate a particular chemical reaction in a cell, allowing it to take place at body temperatures.

Question 23

Molecules such those enzymes, which make a reaction go faster but which can be recovered unchanged at the end of the reaction, are known as…

Answer 23

Catalysts

Question 24

Which enzyme is needed for ethanol to convert into acetaldehyde?

Answer 24

Alcohol dehydrogenase (ADH)

Question 25

What is acetaldehyde and what does it cause in the body?

Answer 25

## Footnote Acetaldehyde is the result of ethanol reacting with ADH. It is more toxic than ethanol and makes people feel sick.

Question 26

Does ADH only exist in a single form?

Answer 26

No, there are different isoforms of ADH. Which ADH isoforms are present in a particular individual depends on the genetic makeup of that person. Two of the five types of ADH metabolise ethanol to acetaldehyde **more rapidly**, resulting in the accumulation of **higher amounts of acetaldehyde** and making a drinker who possesses these forms feel **uncomfortable more quickly** (Asian).

Question 27

Which enzyme is needed for the second ethanol reaction, acetaldehyde → acetic acid?

Answer 27

## Footnote Aldehyde dehydrogenase (ALDH)

Question 28

What is the bond dissociation energy?

Answer 28

## Footnote The input of energy needed to break a bond between two atoms.

Question 29

## Footnote How does the absorption process (into the bloodstream) work?

Answer 29

## Footnote The absorption process involves the molecules that are released from the digested food passing through the wall of the gut and into the surrounding blood vessels.

Question 30

What happens to food before passing into the small intestine?

Answer 30

## Footnote They have to pass the **pyloric sphincter**, which is a muscular constriction which closes when food is present in the stomach, ensuring that food is sufficiently digested before it is released into the small intestine.

Question 31

Which two possibilities/places are there for ethanol being absorbed?

Answer 31

## Footnote Ethanol is absorbed into the blood at a greater rate through the wall of the **small intestine** compared with the wall of the **stomach**. Therefore if ethanol is retained in the stomach (by the closure of the pyloric sphincter) it will be absorbed more slowly, but once the ethanol passes into the intestine it will be absorbed rapidly.

Question 32

## Footnote If there is food in the stomach, what effect will it have on the speed with which the ethanol from a drink enters the bloodstream?

Answer 32

## Footnote The presence of food in the stomach will delay the rate at which ethanol in the stomach enters the small intestine because the **pyloric sphincter** will be closed to retain the food.

Question 33

Why does absorption of food is much faster in the small intestine?

Answer 33

## Footnote The surface area of the lining of this tube is greatly increased by the presence of numerous villi. A larger surface area means absorption of nutrients can occur at a faster rate.

Question 34

## Footnote Molecules of ethanol are not broken down in the gut, but...

Answer 34

They **diffuse** through the wall of the gut into the adjacent blood vessels.

Question 35

## Footnote Blood is transported around the body in pipes known as **blood vessels**. Which types are there?

Answer 35

## Footnote Large vessels that carry blood **away** from the heart are known as **arteries.** Large vessels that carry blood **towards** the heart are **veins**. The arteries and veins branch into a network of tiny **capillaries** that infiltrate all of the tissues of the body.

Question 36

## Footnote The small blood vessels that carry blood away from the gut converge to form a large vein. What's the name?

Answer 36

## Footnote **Portal vein**, which leads directly to the **liver** where some of the ethanol is removed.

Question 37

## Footnote The blood vessels themselves are affected by the presence of ethanol in the blood. How?

Answer 37

The skin becomes warmer and flushed due to an effect called **vasodilation**. The narrow blood vessels immediately beneath the skin **dilate** – they get wider so they carry more blood. * This mechanism, together with sweating, is normally used as a way of cooling the body when it is too hot:* * more flow of blood under the surface of the skin - more cooling can occur- heat can escape.*

Question 38

## Footnote Is an alcoholic drink a good way to warm someone up on a cold evening?

Answer 38

## Footnote An alcoholic drink might indeed make a cold person *feel* warmer as their skin will warm up due to **vasodilation**, but it would increase their actual loss of body heat to the environment, so their core body temperature would *fall*.

Question 39

Why will ethanol affect some organs sooner than others?

Answer 39

## Footnote The rate at which ethanol leaves the blood and enters the organs is dependent upon how rich the **blood supply** is to the particular organ. Organs with a particularly rich blood supply include the brain and the lungs, so ethanol will tend to affect these organs sooner than others.

Question 40

## Footnote If a man and a woman of identical weight each simultaneously drank two glasses of wine, what would you expect to observe if you measured their blood-ethanol concentration 1 hour later and why?

Answer 40

## Footnote The blood-ethanol concentration would be higher in the woman than the man. The woman has a smaller volume of water-based tissues for the ethanol to dissolve in than the man because a higher proportion of her body weight is fat. *(very little ethanol diffuses into fatty tissue because ethanol is more soluble in water than it is in fat)*

Question 41

## Footnote The liver plays an important role in a number of body functions, including:

Answer 41

## Footnote digestive processes, regulation of blood glucose levels, storage of vitamins and the destruction of noxious substances (like ethanol)

Question 42

## Footnote All of the blood from the portal vein, complete with any absorbed nutrients or other substances (ethanol, toxins, drugs, etc.) passes through the liver before reaching the general circulation. What advantage and what risks can you see in this arrangement of the blood flow to the liver?

Answer 42

## Footnote While this arrangement means that the liver can efficiently process absorbed substances such as ethanol and other toxins, it also means that the liver is exposed to higher concentrations of ethanol than any other organ.

Question 43

What means excretion? Which is the most important organ for it?

Answer 43

The **kidneys** are responsible for excretion of waste substances from the blood through the **production of** **urine**. Excretion = separation of waste products from the blood

Question 44

Each kidney contains around a million structures known as .... which filter the blood and produce the urine.

Answer 44

nephrons

Question 45

The brain secrets a special hormone when it detects decreased water levels. Which hormone is this?

Answer 45

Vasopressin ## Footnote

Question 46

Vasopressin travels to an organ. Which one and what does it do there?

Answer 46

Vasopressin travels to the kidneys after detection of decrease in water levels. It then increases the ability of the cells in the nephrone tubes to move more water from within the tubules back to the bloodstream. = reduction of amount of water lost in urine

Question 47

What happens to the vasopressin-kidney-interaction when ethanol is in the body?

Answer 47

Ethanol inhibits the release of vasopressin. So: Increases amount of water lost in the urine = dehydration

Question 48

What is a 'reward' (in evolutionary terms)?

Answer 48

A reward is something that animals, including humans, strive to obtain and will invest effort in gaining. A ‘natural reward’ refers to such things as food, water and sex, as distinct from such ‘unnatural rewards’ as alcohol.

Question 49

What are recreational drugs?

Answer 49

Drugs like alcohol, unnatural rewards They exhibit some similar properties to natural rewards in terms of the desire to obtain them, some of their effects on the **brain**, and the tension created when access is denied.

Question 50

What is a reinforcer (in psychology)? Is alcohol one?

Answer 50

## Footnote In psychology, a reinforcer refers to a factor that strengthens a tendency to engage in a particular behaviour. The tendency to drink alcohol is increased by its **anxiety-lowering effects** in the past. Alcohol can lower painful self-consciousness, hence improving one’s own self-image.

Question 51

What is alcohol myopia?

Answer 51

## Footnote Myopia means literally **‘short-sightedness’**. By analogy, the term ‘alcohol myopia’ indicates alcohol’s effect in inducing ‘psychological short- sightedness’. Alcohol lowers the range of **attention**. It gives a bias in favour of attending to immediate internal and external cues and against considering more remote events.

Question 52

Which two chemicals are most important when it comes to the neurotransmitters and ethanol? Which one is excitatory?

Answer 52

GABA and glutamate. Glutamate is excitatory GABA is inhibitory

Question 53

## Footnote Ethanol is an antagonist to glutamate. How will this affect the activity of a postsynaptic neuron?

Answer 53

## Footnote By antagonising excitatory glutamate, ethanol **decreases** the action potential frequency in this case.

Question 54

## Footnote Ethanol is an agonist to GABA. How will this affect the activity of a pre/postsynaptic neuron?

Answer 54

## Footnote By attaching to sites at a presynaptic neuron that employs GABA, ethanol triggers the release of GABA, and by attaching to sites on the postsynaptic neuron, ethanol boosts the actions of GABA. As GABA is an inhibitory neurotransmitter, the frequency of **action potentials decreases** even more.

Question 55

What is the activity in the prefrontal cortex (PFC)?

Answer 55

The activity of neurons there is associated with voluntary control of behaviour (**self-control**) and restraint.

Question 56

What does ethanol cause in the PFC?

Answer 56

## Footnote Mild to moderate doses of alcohol selectively lower the activity of neurons in the PFC. = People who are intoxicated with alcohol are less restrained

Question 57

## Footnote Stimuli associated with natural rewards, such as the sight of food when hungry, tend to excite a group of neurons in the brain that...

Answer 57

## Footnote use **dopamine** as their neurotransmitter.

Question 58

What does ethanol do with dopaminergic neurons?

Answer 58

## Footnote By its chemical action on the dopaminergic neurons in this pathway, ethanol **increases** their activity, leading people to seek rewards more actively.

Question 59

## Footnote Ethanol has a number of effects in the brain that reinforce each other to increase the tendency to **engage in sexual behaviour**. Can you suggest two of these?

Answer 59

1. Ethanol excites the **dopaminergic** neurons, which cause a person to seek rewards (in this case sex). 2. Ethanol can also reduce the **restraining** activity of the prefrontal cortex.

Question 60

Name some characteristics of **addiction**.

Answer 60

- **craving**: intense conscious occupation with thoughts of the object of the addiction) - **dependence**: addicts come to depend upon the drug for their ‘normal’ mental functioning - **tolerance**: over time, a need for an increasing amount of alcohol to obtain the same level of intoxication - **withdrawal symptoms**: characteristic physiological signs associated with a negative mood when the drug is not taken

Question 61

## Footnote There are at least two psychological explanations (or ‘orientations’) for addiction. Which are these?

Answer 61

1. **exposure orientation**: addiction arises simply ## Footnote as a consequence of frequent use of a drug 2. **adaptive orientation**: addicts try to use a drug to solve an emotional problem in their personal life

Question 62

## Footnote What class of chemical intervention blocks the effect of a neurotransmitter?

Answer 62

antagonists

Question 63

What kind of drug could help against addictions?

Answer 63

## Footnote The evidence points to neurons that employ neurotransmitters of the class termed **opioids** as forming the biological basis of reward and pleasure. Therefore, if an intervention were able to **disrupt** **synapses that employ opioids**, maybe the attraction of alcohol could be reduced. A drug of this class is naltrexone, which antagonises opioid neurotransmission.

Question 64

## Footnote Another class of intervention is to try to create unpleasant consequences of drinking. You met an example of such a drug in Section 2.4.1. Can you recall its name and how it acts?

Answer 64

## Footnote The drug is **Antabuse**, which acts by preventing the conversion of acetaldehyde into acetic acid.

Question 65

## Footnote If unusually **high levels of acetaldehyde** accumulate following an alcoholic drink, how could this have been caused by (a) the rate of reaction of an ADH isoform, and (b) the rate of reaction of an ALDH isoform?

Answer 65

ADH promotes acetaldehyde production isoform with *high* rate = more acetaldehyde ALDH 'removes' acetaldehyde isoform *with* slow rate = more acetaldehyde

Question 66

Ethanol causes abdominal pain, nausea and vomiting during 'hang over'. Why?

Answer 66

- **dehydration** (vasopressin) - at a high concentration, ethanol damages cells on contact = irritation of the stomach and intestinal lining resulting in **inflammation** - ethanol also increases the production of **gastric acid** and intestinal secretions

Question 67

Name the three progressive stages of alcoholic liver disease.

Answer 67

1. fatty liver 2. hepatitis 3. cirrhosis

Question 68

Explain the 'fatty liver'.

Answer 68

## Footnote - early and reversible consequence of excessive alcohol consumption - fat accumulates within the cells of the liver (release of fats from adipose tissue) - reduced fat breakdown in the liver - in cases of chronic alcoholism other nutritional deficiencies play a role

Question 69

What is hepatitis?

Answer 69

## Footnote Hepatitis means ‘**inflammation of the liver**’ and can range from being mild (only detectable through blood tests) to severe, causing sickness, jaundice (yellowing of the skin) and pain. Very severe hepatitis can lead to liver failure which is often fatal.

Question 70

What is cirrhosis?

Answer 70

## Footnote Cirrhosis is a gradual and irreversible change in about 10% of chronic heavy­ drinkers whereby **liver cells are replaced by scar tissue**. - decrease the ability of the liver to perform its many essential biological functions - disrupts the blood flow through the liver tissue which causes serious complications such as damage to the spleen (an organ involved in blood maintenance) and the blood vessels of the gut (as blood pressure increases in the portal vein)

Question 71

Why does the disruption caused by cirrhosis affects many body systems?

Answer 71

Because the liver is responsible for many important functions, for example: - digestive processes - regulation of blood glucose levels - storage of vitamins - break­down of noxious substances

Question 72

## Footnote Chronic consumption of high levels of alcohol can cause irreversible damage to the nervous system. For example:

Answer 72

- **dementia** (loss of intellectual abilities due to shrinkage of brain tissue) - damage to the **peripheral nerves** (i.e. those connecting the central nervous system, CNS, with the rest of the body). _Symptoms_: sensory disturbances (numbness or pain), motor disturbances (weakness and muscle wasting) and some problems with speech, swallowing, heart rate, pupil function, erectile function, breathing during sleep, etc.

Question 73

What is the fetal alcohol syndrome, FAS?

Answer 73

A disorder associated with maternal alcohol consumption during pregnancy. _FAS is defined by four criteria:_ 1. alcohol consumption during pregnancy 2. a characteristic pattern of minor facial abnormalities and other malformations (in particular of the limbs and heart) 3. growth retardation 4. central nervous system abnormalities

Question 74

## Footnote The proportion of fat per body weight increases with age. How might this affect older drinkers?

Answer 74

## Footnote The increased proportion of fat to muscle in older people will result in a **decrease in total body water**. As ethanol is water­soluble, the same amount of ethanol will be dissolved in a smaller amount of water, resulting in a **higher BAC** in an older person than a younger. Unless the body responds by making more enzymes, this will result in higher levels of intoxication after smaller amounts of ethanol.

Question 75

## Footnote If the reaction catalysed by ALDH to form acetic acid is faster than the production of acetaldehyde (catalysed by ADH), how will this affect the drinker?

Answer 75

## Footnote There will be no build­up of acetaldehyde because it will metabolise to acetic acid as soon as it is made. So, the drinker will not experience the flushing, increased heart rate, dizziness or nausea associated with a build­up of acetaldehyde.

Question 76

What is coronary heart disease (CHD)?

Answer 76

## Footnote This condition occurs when the arteries supplying oxygen and nutrients to the heart muscle become blocked by fatty deposits known as plaques, and areas of heart muscle die as a result.

Question 77

What is a confounding factor?

Answer 77

Any factor which is **statistically associated** with a particular outcome (e.g. the incidence of a disease), but which is ***not involved in its causation***. The association is said to be ‘confounding’ because it can disguise the true cause (or causes) of the outcome.