Environment and the Brain 3

Question 1

True or false? Explain your answer if appropriate. (1)

Diet sits on a spectrum of impact on brain health, with a Mediterranean and anti-inflammatory diet on the good end, and Ultra-processed and Western diet on the bad end.

Answer 1

True

Question 2

Give an example of a diet which is used as a medical treatment. (1)

Answer 2

Ketogenic diet for epilepsy

Question 3

Give three circumstances where the ketogenic diet is used as a treatment for epilepsy. (3)

Answer 3

• In drug-resistant epilepsy
• In children especially (but can also be used in adults)
• In GLUT1 deficiency (where it is the standard treatment)

Question 4

Does the ketogenic diet lead to improved symptoms in all patients with epilepsy? (1)

Answer 4

No

Question 5

Complete the sentence regarding a ketogenic diet and epilepsy. (4)

When using a ketogenic diet to help treat epilepsy, patients must be monitored by a medical team to ensure …………………… of the diet, and …………………….

However, this treatment has been used for ……………….. years, and is advised by ……………………….

Answer 5

Effectiveness

nutritional balance

more than 100

the NICE guidelines

Question 6

Describe the ketogenic diet, in terms of the intake of the following food groups. (3)

a) fat

b) carbohydrate

c) protein

Answer 6

a) high fat (75% of diet)

b) low carbohydrate (5% of diet)

c) controlled protein intake (about 20% of diet)

Question 7

Describe how the ketogenic diet alters the body and brain’s main energy source. (1)

Answer 7

Changes the main energy source from carbohydrates (glucose) to fats (ketones)

Question 8

Give five ways in which the ketogenic diet impacts neurobiology. (5)

Answer 8

• Increases mitochondrial function and biogenesis
• Reduces oxidative stress
• Impacts gut-brain axis via changes in gut microbiota
• Mediates reduction in neuroinflammation
• Widespread changes in gene expression

Question 9

Suggest a mechanism by which the ketogenic diet may have an impact on neurobiology, such as gene changes, neuroinflammation, and mitochondrial function. (1)

Answer 9

Changes likely mediated by circulating miRNA and epigenetic molecules

Question 10

The ketogenic diet is able to result in widespread changes in gene expression in the brain.

Give three general categories of genes (what brain function they are associated with) which are downregulated by a ketogenic diet. (3)

Answer 10

• Ion channels
• Neurotransmission
• Synapse structure

Question 10

Suggest a general group of ion channel genes which may be downregulated in a ketogenic diet. (1)

Answer 10

Potassium channels

Question 10

The ketogenic diet is able to result in widespread changes in gene expression in the brain.

Give three general categories of genes (what brain function they are associated with) which are upregulated by a ketogenic diet. (3)

Answer 10

• Ion channels
• Synapse structure
• Growth factor

Question 11

Suggest a general group of ion channel genes which may be upregulated in a ketogenic diet. (1)

Answer 11

Calcium channels

Question 12

Is the MAOA gene upregulated or downregulated in a ketogenic diet? (1)

Answer 12

Downregulated

Question 13

Is the BDNF gene upregulated or downregulated in a ketogenic diet? (1)

Answer 13

Upregulated

Question 14

Is gene expression of orexins upregulated or downregulated in a ketogenic diet? (1)

What role do the orexins play? (1)

Answer 14

• Downregulated
• Play a role in wakefulness

Question 15

Fill the gaps relating to GLUT1 deficiency. (3)

GLUT1 deficiency results in low ………………. levels in the CSF, and a developmental delay featuring ………………….. and ……………………

Answer 15

glucose

movement disorders

a generalised intractable epilepsy

Question 15

ketogenic diet is the standard treatment for GLUT1 deficiency.

What is GLUT1? (1)

What is the role of GLUT1? (1)

Answer 15

Glucose transporter

Expressed on erythrocytes and BBB endothelial cells, so facilitates glucose transport across the BBB

Question 16

Describe how a ketogenic diet is able to successfully treat GLUT1 deficiency. (3)

Answer 16

It provides an alternative energy source to the brain

Ketones cross the BBB via the MCT1 transporter

So it ‘doesn’t matter’ that GLUT1 isn’t working

Question 17

Describe the metabolic pathway which allows fat to be used as energy in the brain. (5)

Answer 17

Lipolysis of dietary or stored fat

forms free fatty acids

FFAs can be converted to beta-hydroxybutyrate in liver mitochondria and then cross BBB

Or can cross BBB first and then be converted to beta-hydroxybutyrate

Beta-hydroxybutyrate converted to Acetyl-CoA in neurones and used in TCA cycle

Question 18

Give two general food groups that the Mediterranean diet is based around. (2)

Answer 18

• Plant-based foods
• Healthy fats

Question 19

Give six key stapes of the Mediterranean diet. (6)

Answer 19

• Seafood
• Fruits and vegetables
• Wholegrains
• Nuts and legumes
• Good oils/fats (olive oils, avocado, nuts)
• Water as a drink (plus a little bit of wine)

Question 20

Complete the sentence relating to diet and mental health. (1)

A Mediterranean diet, or even just a healthy diet, are associated with less …………………….. symptoms.

Answer 20

depressive

Question 21

When looking at studies investigating the impact of Mediterranean and Healthy diet on development of depression, in which of the following ranges would you expect the odds ratios to be in, for development of depression with Healthy/Mediterranean diet? (1)

a) 0-1

b) 1-2

c) 2-3

d) 3-4

Describe what this means in words. (1)

Answer 21

0-1

Mediterranean or healthy diet decreases risk of developing depression

Question 22

Give four anti-inflammatory molecules found in a healthy/Mediterranean diet which may be responsible for the decrease in depressive symptoms seen with these diets. (4)

Answer 22

• Omega3 polyunsaturated fatty acids
• Unsaturated fatty acids
• Polyphenols
• Dietary fibre

Question 23

Omega3 polyunsaturated fatty acids have been suggested to be part of a Mediterranean/healthy diet that decreases inflammation and is good for health.

Give a food group which contains high levels of omega3 fatty acids. (1)

Answer 23

Seafood

Question 24

Unsaturated fatty acids have been suggested to be part of a Mediterranean/healthy diet that decreases inflammation and is good for health.

Give a food group which contains high levels of unsaturated fatty acids. (1)

Answer 24

Olive oil

Question 25

Polyphenols have been suggested to be part of a Mediterranean/healthy diet that decreases inflammation and is good for health.

Give three foods which contain high levels of polyphenols. (3)

Answer 25

• Cocoa
• Blueberries
• Curcumin/turmeric

Question 26

Dietary fibre has been suggested to be part of a Mediterranean/healthy diet that decreases inflammation and is good for health.

Give two food groups which contain high levels of dietary fibre. (2)

Answer 26

• Vegetables
• Wholemeal products

Question 27

Suggest a way that dietary fibre may act as an anti-inflammatory food and confer a health benefit. (1)

Answer 27

Can promote beneficial gut microorganisms

Question 28

Give the two most abundant components/molecules of the brain. (2)

Answer 28

FIRST = water

SECOND = fat

Question 29

Give two general roles of fat in the brain. (2)

Answer 29

• Formation of cell membranes
• Formation of myelin

Question 30

Apart from forming cell membranes and myelin, give two other specific roles for omega 3 and omega 6 fatty acids in the body and brain. (2)

Answer 30

• Precursors for molecules regulating blood pressure
• Precursors for molecules regulating inflammation

Question 31

Approximately 90% of dietary fats are in what form? (1)

a) monoglycerides

b) diglycerides

c) triglycerides

Answer 31

c) triglycerides

Question 32

Describe the general structure of a triglyceride molecule. (2)

Answer 32

3 fatty acid molecules

Attached to a glycerol backbone

Question 33

Describe what is meant when referring to the alpha and omega end of a fatty acid. (2)

Answer 33

Alpha end is acid end with COOH

Omega end is other end with just carbon bonds and no functional group

Question 34

Briefly describe the general structure of an omega-3 fatty acid. (2)

Answer 34

Polyunsaturated fatty acid

with a double bond connecting the 3rd and 4th carbon from the omega end

Question 35

Name the three main omega-3 fatty acids. (3)

Answer 35

• Alphalinoleic acid (ALA)
• Eicosapentaenoic acid (EPA)
• Docosahexaenoic acid (DHA)

Question 36

Name an omega-6 fatty acid which must be obtained from the diet. (1)

Answer 36

Linoleic acid

Question 37

Fill the gaps relating to omega-3 fatty acids. (4)

The body is ………………………(able/unable) to make alphalinoleic acid. Therefore it ………………………(must/must not) be obtained from the diet.

ALA can then be used to make small amounts of two other omega-3 fatty acids, called ……………………… and ………………………..

Answer 37

unable

must

eicosapentaenoic acid (EPA)

docosahexaenoic acid (DHA)

Question 38

Docosahexaenoic acid (DHA), an omega-3 fatty acid, can be synthesised from alphalinoleic acid (ALA), another omega-3 fatty acid, in the body.

Despite this, a dietary source of DHA is still required. Describe why this is. (3)

Answer 38

• ALA must also be obtained from the diet
• And only a small amount can then be converted to DHA
• So relying on ALA to DHA conversion is not a reliable way of getting DHAs

Question 39

Docosahexaenoic acid is a dietary component which is thought to confer a health benefit.

What type of molecule is docosahexaenoic acid? (1)

Answer 39

Omega-3 fatty acid

Question 40

Docosahexaenoic acid is an omega-3 fatty acid. Small amounts can be made in the body, however most must come from the diet.

Most people do not get enough omega-3 in their diet - is it more beneficial to add in more omega-3-rich foods, or to take supplements? (1)

Answer 40

Adding in more omega-3-rich foods

Question 41

Docosahexaenoic acid (DHA) is an omega-3 fatty acid which is thought to be beneficial to the body and brain.

Higher DHA blood levels are associated with a lower risk of developing which two neurological illnesses? (2)

Answer 41

• All-cause dementia
• Alzheimer’s disease

Question 42

In older adults (>65yrs), eating one or more fatty fish meals per week reduces the risk of dementia and Alzheimer’s disease.

Why is this thought to be the case? (1)

Answer 42

Due to docosahexaenoic acid (DHA) in fatty fish

(DHA is an omega-3 fatty acid)

Question 43

Describe two pieces of evidence that support the fact that docosahexaenoic acid and omega-3 fatty acids may protect against developing dementia and Alzheimer’s disease. (2)

Answer 43

• Omega-3 supplements can be beneficial in early stages of Alzheimer’s
• High dose docosahexaenoic acid (DHA) supplement could be beneficial for carriers of the APOE4 gene before onset (or potentially in early stages) of Alzheimer’s

Question 44

Give a group of patients who may particularly benefit from a high-dose docosahexaenoic acid (DHA) supplement before onset or in early stage Alzheimer’s disease. (1)

Answer 44

Carriers of APOE4 gene

Question 45

Fill the gaps relating to omega-3, docosahexaenoic acid (DHA), and dementia. (4)

The benefits of DHA on cognition may be due to its ability to control ………………………. via its downstream products.

Three examples of these downstream products are: …………………….., ………………………….., and ……………………..

Answer 45

neuroinflammation

D-series resolvins

maresins

protectins

Question 46

It is thought that DHA may benefit the brain and reduce the risk of dementia via its downstream products. One of which is neuroprotectin D1.

Describe the general effects of neuroprotectin D1 in terms of the following domains. (4)

a) neuronal death

b) brain cell survival

c) ageing

d) neurodegenerative disease

Answer 46

a) prevents neuronal death

b) improves brain cell survival

c) improves repair in ageing

d) improves repair in neurodegenerative diseases

Question 47

It is thought that DHA may benefit the brain and reduce the risk of Alzheimer’s and dementia via its downstream products. One of which is neuroprotectin D1.

Give four effects of neuroprotectin D1 related to Alzheimer’s disease. (4)

Answer 47

• Reduces amyloid beta 42
• Represses inflammation
• Represses oxidative stress
• Represses apoptosis

***Last three are all usually induced by amyloid beta 42 (so does DHA reduce these by reducing Ab42?)

Question 48

Give three mechanisms which Neuroprotectin D1, a downstream product of docosahexaenoic acid (DHA), may use to reduce amyloid beta 42 and protect against Alzheimer’s disease. (3)

Answer 48

• Upregulation of PPAR-gamma
• Upregulation of amyloid precursor protein alpha
• Downregulation of beta amyloid precursor protein

Question 49

What is PPARy? (1)

Answer 49

A ligand-activated transcription factor, which can induce changes in gene expression and act as an anti-inflammatory factor.

Question 50

What is the NOVA food classification system? (1)

Answer 50

Food classification which groups foods (into 4 groups) according to how processed the foods are.

Question 51

Describe group 1 of the NOVA food classification system. (1)

Answer 51

Unprocessed/minimally processed foods such as fruit/veg/milk/meat/nuts/eggs

Question 52

Describe group 2 of the NOVA food classification system. (1)

Answer 52

Processed culinary ingredients such as olive oil/butter/sugar/salt/honey/vinegar

Question 53

Describe group 3 of the NOVA food classification system. (1)

Answer 53

Processed foods such as ham/cheese/fresh bread/bacon/salted nuts/tinned fruit in syrup/tinned tuna

Question 54

Describe group 4 of the NOVA food classification system. (1)

Answer 54

Ultra processed foods such as supermarket bread/ready meals/breakfast cereal/biscuits/cakes/crisps

Question 55

What is an ‘ultra processed food’? (3)

Answer 55

An industrially formulated edible substance

generated from compounds extracted/derived/synthesised from food, food substrates, or organic compounds

and contain 5 or more ingredients which are rarely/never used in home kitchens (for example artificial food additives).

Question 56

Ultra processed foods make up more than half of the total dietary energy consumed in high income countries.

Give three reasons why this is. (3)

Answer 56

• Cheaper
• More palatable
• Longer shelf-life

Question 57

Meta-analyses have found that higher consumption of processed food increases risk of developing what two neurological conditions in the future? (2)

Answer 57

Anxiety

Depression

Question 58

Processed foods are thought to be particularly bad for health because they are energy rich, but lack nutritional components.

Give four ingredients in processed foods which make them energy rich, but don’t really have any nutritional value. (4)

Answer 58

• Refined starches
• Sugar
• Sodium
• Saturated and trans fats

Question 59

Processed foods are thought to be particularly bad for health because they are energy rich, but lack nutritional components.

Give four nutritional components that are thought to be beneficial to health, but that are usually lacking in processed food. (4)

Answer 59

• Omega-3 fatty acids
• Fibre
• Polyphenols
• Minerals

Question 60

Describe in general the mechanism by which artificial sweeteners and monosodium glutamate can affect the brain and mental health. (1)

Answer 60

Impact synthesis/release of DA, NA, and 5HT

Question 61

Describe in general the mechanism by which dietary emulsifiers can affect the brain and mental health. (1)

Answer 61

Increased inflammation due to dysregulation of the gut microbiota

Question 62

Describe the effect that aspartame is thought to have on the brain and mental health. (1)

Answer 62

Increased anxiety

Question 63

A study investigating aspartame and its effects on the brain gave rodents either plain water, 0.03% aspartame (15% of FDA maximum daily dose), or 0.015% (8% of FDA maximal dose).

The open field test was carried out every 2 weeks for a few months.

What was the affect of aspartame on the open field test results? (1)

What does this indicate? (1)

Answer 63

Reduced time in centre for both doses

Indicates increased anxiety

Question 64

A study investigating aspartame and its effects on the brain gave rodents either plain water, 0.03% aspartame (15% of FDA maximum daily dose), or 0.015% (8% of FDA maximal dose).

What was the effect of 0.015% aspartame on the elevated zero maze at 12 weeks? (1)

What does this indicate? (1)

Answer 64

Rodents showed less time in open arms with aspartame

This indicates increased anxiety

Question 65

A study investigating aspartame and its effects on the brain gave rodents either plain water, 0.03% aspartame (15% of FDA maximum daily dose), or 0.015% (8% of FDA maximal dose).

They concluded that rodents that had received aspartame showed more anxiety on the open field test and elevated zero maze.

Suggest a way that you could confirm that the altered behaviour shown on the behavioural tests is due to increased anxiety. (1)

Answer 65

Give the rodents diazepam and look for reduced anxiogenic behaviours.

Question 66

A study investigating aspartame and its effects on the brain gave rodents either plain water, 0.03% aspartame (15% of FDA maximum daily dose), or 0.015% (8% of FDA maximal dose).

One part of the study took the rodents that had received aspartame for 12 weeks and had them perform on the open field test twice, once with saline and once with diazepam (repeated measures).

Describe the results of this part of the study. (1)

Compare what was seen with aspartame+diazepam to what was seen with no aspartame. (1)

Give a short conclusion. (1)

Answer 66

Spent more time in centre of field with diazepam.

However still spent less time compared to rodents which had no aspartame.

Conclusion: diazepam can reduce aspartame-induced anxiety, however cannot fully ameliorate effect (animals will still have more anxiety than animals who never had aspartame).

Question 67

A study investigating aspartame and its effects on the brain gave rodents either plain water, 0.03% aspartame (15% of FDA maximum daily dose), or 0.015% (8% of FDA maximal dose).

They found alterations in GABAergic and glutamatergic pathways in which part of the brain? (1)

Answer 67

Amygdala

Question 68

A study investigating aspartame and its effects on the brain gave rodents either plain water, 0.03% aspartame (15% of FDA maximum daily dose), or 0.015% (8% of FDA maximal dose).

They found alterations in GABAergic and glutamatergic pathways in the amygdala at 12 weeks, by looking at gene expression related to these pathways.

Give three changes in gene expression that were seen with aspartame, relating to GABAergic and glutamatergic pathways. (3)

Answer 68

Upregulation of NMDA receptor subunit 2D (Grin2d gene)

Upregulation of metabotropic glutamate receptor 4 (Grm4 gene)

Downregulation of GABA-A receptor associated protein (Gabarap gene)

Question 69

A study investigating aspartame and its effects on the brain gave rodents either plain water, 0.03% aspartame (15% of FDA maximum daily dose), or 0.015% (8% of FDA maximal dose).

They found that aspartame increases anxiety and alters GABAergic and glutamatergic neurotransmission.

Describe how this study tested whether the effect on anxiety was transgenerational. (1)

What were the results? (2)

Answer 69

• Test offspring for anxiety (this study tested 2 further generations), for example with open field test
• F1 and F2 generations showed less time in centre of open field test
• This was rectified by diazepam, which shows that the behaviour changes seen were due to anxiety

Question 70

A study investigating aspartame and its effects on the brain gave rodents either plain water, 0.03% aspartame (15% of FDA maximum daily dose), or 0.015% (8% of FDA maximal dose).

They found that aspartame increases anxiety and alters GABAergic and glutamatergic neurotransmission, and that these effects were transgenerational.

Describe a drawback of this study concluding that the effects are transgenerational. (1)

Answer 70

Only tested paternal offspring (with anxiety passed down from Dad), so more replication is needed to confirm these effects.

Question 71

What is the general role of dietary emulsifiers? (1)

Answer 71

Enable the homogenisation of immiscible substances

Question 72

Give 2 product categories (other than food) where dietary emulsifiers may be used. (2)

Answer 72

• Cosmetics
• Pharmaceuticals

Question 73

Give two general positive results of using dietary emulsifiers in food. (2)

Answer 73

• Improve texture
• Extend shelf-life

Question 74

Give two examples of dietary emulsifiers. (2)

Answer 74

Carboxymethylcellulose (CMC)

Polysorbate-80 (P80)

Question 75

Give five specific uses of the dietary emulsifier, carboxymethylcellulose, in specific foods. (5)

Answer 75

• Gives quality based texture and creamy mouthfeel in ice cream
• Regulates viscoelastic behaviour of fruit syrups and juices
• Used as a fat reducer in meat products
• Prevents layer formation and stabilises texture of acidic drinks at high/low temperatures
• Used as a thickening or dewatering agent in dairy products

Question 76

Briefly describe the general effect of dietary emulsifiers on the brain and mental health. (1)

Answer 76

Increase anxiety

Question 77

A study assessed the effects of dietary emulsifiers on the brain and mental health. They gave mice 1% of either carboxymethylcellulose (CMC) or polysorbate-80 (P80) in drinking water, or just plain water.

They tested the effects in both males and females.

Give the results for the open field test and the elevated plus maze. (2)

Answer 77

In males, CMC and P80 reduced time in centre of open field test.

This was not seen in females, or on the elevated plus maze.

Question 78

A study assessed the effects of dietary emulsifiers on the brain and mental health. They gave mice 1% of either carboxymethylcellulose (CMC) or polysorbate-80 (P80) in drinking water, or just plain water.

They tested the effects in both males and females.

Describe how the emulsifiers affected amount of adipose tissue and spleen size in both males and females. (4)

Answer 78

Increased adipose tissue in males

Increased adipose tissue in females

Larger spleen in males

No change to spleen size in females

Question 79

A study assessed the effects of dietary emulsifiers on the brain, body, and mental health. They gave mice 1% of either carboxymethylcellulose (CMC) or polysorbate-80 (P80) in drinking water, or just plain water.

They tested the effects in both males and females.

Give two general physiological changes that were seen in mice that had consumed dietary emulsifiers. (2)

Answer 79

• Increased adipose tissue (in males and females)
• Larger spleen (in males)

Question 80

A study assessed the effects of dietary emulsifiers on the brain, body, and mental health. They gave mice 1% of either carboxymethylcellulose (CMC) or polysorbate-80 (P80) in drinking water, or just plain water.

They tested the effects in both males and females, and found that dietary emulsifiers increased the size of the spleen in males.

What might this indicate? (1)

Answer 80

Systemic inflammation

Question 81

A study assessed the effects of dietary emulsifiers on the brain, body, and mental health. They gave mice 1% of either carboxymethylcellulose (CMC) or polysorbate-80 (P80) in drinking water, or just plain water.

They tested the effects in both males and females.

One of the tests looked at the preference for a novel mouse, as a measure of social interest.

Describe the results for both males and females. (2)

Why is interpreting and accurately drawing conclusions from this kind of data on social interactions difficult? (1)

Answer 81

Males - no effect on preference for novel mouse

Females - Decreased preference for novel mouse with dietary emulsifiers (so decreased social interest)

Difficult to interpret because female mice have different social interactions than male mice.

Question 82

A study assessed the effects of dietary emulsifiers on the brain, body, and mental health. They gave mice 1% of either carboxymethylcellulose (CMC) or polysorbate-80 (P80) in drinking water, or just plain water.

They tested the effects in both males and females.

One test looked at the amounts of neuropeptides in the arcuate and paraventricular nuclei of the hypothalamus.

Give two neuropeptides which were shown to be affected. (2)

Answer 82

Agouti-related peptide

Alpha melanocyte stimulating hormone

Question 83

A study assessed the effects of dietary emulsifiers on the brain, body, and mental health. They gave mice 1% of either carboxymethylcellulose (CMC) or polysorbate-80 (P80) in drinking water, or just plain water.

They tested the effects in both males and females.

One test looked at the amounts of neuropeptides in the arcuate and paraventricular nuclei of the hypothalamus.

Give the results regarding agouti-related peptide for both males and females. (2)

What is the usual role of agouti-related peptide? (1)

Answer 83

Males - increased agouti-related peptide

Females - no change to agouti-related peptide

Usually stimulates food intake and reduces anxiety

Question 84

A study assessed the effects of dietary emulsifiers on the brain, body, and mental health. They gave mice 1% of either carboxymethylcellulose (CMC) or polysorbate-80 (P80) in drinking water, or just plain water.

They tested the effects in both males and females.

One test looked at the amounts of neuropeptides in the arcuate and paraventricular nuclei of the hypothalamus.

Give the results regarding alpha melanocyte stimulating hormone for both males and females. (2)

What is the usual role of alpha melanocyte stimulating hormone? (1)

Answer 84

Males - reduced aMSH

Females - reduced aMSH

would normally reduce food intake and increase anxiety

Question 85

What are insecticides? (1)

Answer 85

Compounds that kill insects

Question 86

Give three general uses of insecticides. (3)

(You can give an example if you can think of one)

Answer 86

• Crop protection
• Human health (stopping malaria spread etc)
• Veterinary use (tick/mite removal)

Question 87

Describe the general, non-specific method by which insecticides kill pests. (1)

Answer 87

Target proteins involved in neurotransmission and muscle contraction

Question 88

Complete the sentence relating to insecticides. (1)

Insecticides kill pests by interfering with the nervous system or muscle contraction. Many are based on ……………………………

Answer 88

natural neurotoxins

Question 89

Describe why insecticides in the past were more harmful than they are now. (1)

What has changed to make them less harmful? (1)

Answer 89

They had negative effects on humans and non-pest animals as well as pests

However they are now designed with the intention of being pest-selective

Question 90

Give three groups of pesticides which are older and confer a larger risk to humans and non-pest animals, so are no longer used. (3)

One of these groups has two specific examples/subgroups which are particularly dangerous. Name them. (2)

Answer 90

Organochlorines (DDT and cyclodienes)

Organophosphates

Carbamates

Question 91

Fill the gaps relating to insecticides. (4)

Newer insecticides have good selectivity for their target ………………… in ……………………, and are relatively non-toxic to ………………….. and ……………………..

Answer 91

proteins

pests

humans

non-pest animals

Question 92

Give an example of a newer insecticide which is more pest-selective and confers lower risk to humans and non-pest animals. (1)

Answer 92

Pyrethroids

Question 93

Why are new types of insecticides being continually produced and brought onto the market? (1)

Answer 93

Insecticides tend to have a finite life span due to insects becoming resistant.

Question 94

Give a few examples of types/groups of insecticides which are either used now or have been used in the past. (9)

Answer 94

• Organochlorines
• Organophosphates
• Carbamates
• Pyrethroids
• Phenylpyrazoles
• Neonicotinoids
• Diamides
• Butenolides
• Sulfoximines

Question 95

Fill the gaps relating to insecticides. (2)

All types of insecticide target the nervous system except ………………………., which target …………………….

Answer 95

diamides

muscle

Question 96

Give two types of insecticides which act on voltage-gated sodium channels. (2)

In addition, give a natural toxin which acts on this target, that the insecticides may be based upon. (1)

Answer 96

• DDT (which is an organochlorine)
• Pyrethroids

Pyrethrins are natural toxins which act on VGSCs.

Question 97

Give two types of insecticides which act on the enzyme acetylcholinesterase. (2)

Answer 97

• Organophosphates
• Carbamates

Question 98

Give three types of insecticides which act on nicotinic acetylcholine receptors. (3)

In addition, give a natural toxin which acts on this target, that the insecticides may be based upon. (1)

Answer 98

• Neonicotinoids
• Sulfoximines
• Butenolides

Nicotine is a natural toxin which acts at this target.

Question 99

Give two types of insecticides which act on chloride channels on the post-synaptic membrane. (2)

Answer 99

• Organochlorides
• Phenylpyrazoles

Question 100

Describe the exact target of the diamide insecticides in muscle. (1)

Answer 100

Ryanodine receptors on the sarcoplasmic reticulum

Question 101

Describe the general effect of insecticides targeting and binding to voltage gated sodium channels. (1)

Answer 101

Binding to VGSCs stops it from inactivating

Question 102

Describe the general effect of insecticides targeting and binding to the enzyme acetylcholinesterase. (1)

Answer 102

Prevents ACh breakdown, so higher synaptic ACh concentration

Question 103

Describe the general effect of insecticides targeting and binding to nicotinic acetylcholine receptors. (1)

Answer 103

Binding causes activation of the nAChRs

Question 104

Describe the general effect of insecticides targeting and binding to chloride channels. (1)

Answer 104

Prevents activation

Question 105

Describe the general effect of insecticides targeting and binding to ryanodine receptors. (1)

Answer 105

Increased calcium release into cytosol

Question 106

Give five specific targets that insecticides may bind to in order to kill pests. (5)

Answer 106

• Voltage gated sodium channels
• Acetylcholinesterase
• Nicotinic acetylcholine receptors
• Chloride channels
• Ryanodine receptors

Question 107

Insecticides may exert their effects by targeting and binding to chloride channels on the post-synaptic membrane.

Describe a key difference between chloride channels found in invertebrates, and chloride channels found in vertebrates. (2)

Answer 107

In invertebrates, chloride channels are activated by glutamate

In vertebrates, chloride channels are activated by GABA

Question 108

Pyrethroid insecticides are based around which naturally occurring neurotoxin? (1)

Answer 108

Pyrethrins

Question 109

Pyrethrins are naturally occurring neurotoxins which can act as starting points for the development of some insecticides.

Name the plant that pyrethrins are derived from (common and scientific names). (2)

Answer 109

Pyrethrum daisy

Tanacetum cinerariifolium

Question 110

Pyrethroid insecticides act on which target protein in the nervous system? (1)

Answer 110

Voltage gated sodium channels

Question 111

Give three specific effects that pyrethroid insecticides have on voltage-gated sodium channels. (3)

Answer 111

• Sensitize channels to voltage
• Reduce inactivation (closing of inactivation gate)
• Prevent deactivation (closing of activation gate)

Question 112

Do pyrethroid insecticides cause a gain or loss of function to voltage gated sodium channels? (1)

What is the overall consequence of the effect of pyrethroids on voltage gated sodium channels? (1)

Answer 112

Massive gain of function

Consequence is that the neurone is persistently depolarised (so cannot repolarise and produce more action potentials)

Question 113

Describe the molecular mechanism of how pyrethroids are mostly selective for insects and not humans. (1)

Answer 113

Most of the selectivity can be traced back to a single amino acid difference between insect and human voltage gated sodium channels.

Question 114

There have been some cases of farmers experiencing symptoms after using pyrethroid insecticides.

Give three symptoms experienced by farmers after using pyrethroids. (3)

Answer 114

Redness in skin

Tingling sensation

Burning pain in extremities

Question 115

There have been cases where farmers using pyrethroid insecticides have complained of redness, tingling, and burning pain in their extremities.

Describe a piece of evidence relating to a medical condition with similar symptoms, which supports the fact that pyrethroids cause these symptoms.

Also, describe how this evidence may point to a mechanism of how pyrethroids might cause these symptoms. (4)

Answer 115

• Symptoms similar to those found in primary erythromelalgia (PE)
• PE caused by gain of function mutation in Nav1.7 channels
• which sensitises channels to voltage (meaning less depolarisation required for activation)
• So with the similarities in symptoms, it would be reasonable to assume that effects seen in farmers using pyrethroids may also be due to changes in or binding to Nav1.7 channels

Question 116

It is thought that farmers using pyrethroids may experience symptoms such as burning pain in the extremities, due to the insecticide acting on Nav1.7 channels.

What is the Nav1.7 channel, and explain why changes to this channel may account for the symptoms seen in farmers. (2)

Answer 116

Subtype of human voltage gated sodium channel

Found in the PNS and associated with causing burning pain - so changes to channel may account for causing burning pain in extremities.

Question 117

It is thought that symptoms seen in farmers after using pyrethroid insecticides (such as redness, tingling, and burning pain in extremities), may be due to the pyrethroids acting on Nav1.7 channels.

This is because similar symptoms are seen in a medical condition called Primary Erythromelelgia (PE), which is caused by a gain of function mutation in Nav1.7 channels.

Describe a more specific collection of evidence supporting the Nav1.7 channel in the toxicity of pyrethroids, again, linking the changes seen with pyrethroids to changes known to occur in PE. (3)

Answer 117

• Mutations seen in PE are commonly in the DIIS4-S5 linker, and DIIS5
• In insects, pyrethroid resistance mutations occur in similar places (eg. the M918T mutation, which occurs in DIIS4-S5 linker)
• This suggests that the DIIS4-S5 linker and the DIIS5 regions are regions of the VGSC where pyrethroids may bind to cause death in insects, and symptoms in humans

Question 118

It is thought that symptoms seen in farmers after using pyrethroid insecticides (such as redness, tingling, and burning pain in extremities), may be due to the pyrethroids acting on Nav1.7 channels.

Give two specific molecular regions (ie. domains and segments) where pyrethroids may act on the VGSCs in both insects and humans. (2)

Describe one piece of evidence from humans, and one piece of evidence from insects, which supports these regions as important for pyrethroid binding. (2)

Answer 118

DIIS4-S5 linker

DIIS5

HUMAN EVIDENCE:

• These are the most common regions for mutations to be in primary erthyromelalgia, which causes similar symptoms to pyrethroid exposure

INSECT EVIDENCE:

• Common mutations which result in pyrethroid resistance occur in these regions

Question 119

Experimental evidence supporting pyrethroids affecting human Nav1.7 channels include patch clamp experiments of TE671 cells.

Why are TE671 cells ideal for investigating Nav1.7 channels? (1)

Answer 119

They only express Nav1.7 channels

Question 120

Experimental evidence supporting pyrethroids affecting human Nav1.7 channels include patch clamp experiments of TE671 cells.

Describe how this experiment could be carried out, including what could be measured. (4)

Answer 120

Activate channels at a range of depolarising voltage pulses

In the presence of different concentrations of different pyrethroids

Measure sensitivity to membrane potential (measure V50.act)

Also measure Tinact (how long inactivation takes) at a specific depolarising voltage

Question 121

Experimental evidence supporting pyrethroids affecting human Nav1.7 channels include patch clamp experiments of TE671 cells.

In these experiments, V50.act was measured for different concentrations of pyrethroids.

Describe what is meant by V50.act in the context of pyrethroids acting on Nav1.7. (1)

Give an interpretation of V50.act (ie. what does a high/low number mean?). (1)

Answer 121

Membrane potential required to activate half of the available Nav1.7 channels on the cell.

Lower V50.act indicates a more excitable channel

Question 122

Experimental evidence supporting pyrethroids affecting human Nav1.7 channels include patch clamp experiments of TE671 cells.

In these experiments, Tinact was measured for different concentrations of pyrethroids.

Describe what is meant by Tinact in the context of pyrethroids acting on Nav1.7. (1)

Give an interpretation of Tinact (ie. what does a high/low number mean?). (1)

Answer 122

Time constant describing how long it takes for currents to decay and the channel to inactivate.

Higher Tinact indicates a channel which stays open for longer.

Question 123

Experimental evidence supporting pyrethroids affecting human Nav1.7 channels include patch clamp experiments of TE671 cells.

In these experiments, V50.act and Tinact were measured for different concentrations of different members of the pyrethroid group of insecticides.

In general, what would you expect to see for both V50.act and Tinact in the presence of pyrethroids? (2)

Answer 123

Lower V50.inact

Higher Tinact

Question 124

Experimental evidence supporting pyrethroids affecting human Nav1.7 channels include patch clamp experiments of TE671 cells.

In these experiments, V50.act and Tinact were measured for different concentrations of different members of the pyrethroid group of insecticides.

Which of these measurements was changed more significantly in the presence of pyrethroids? (1)

Answer 124

V50.act

Question 125

Experimental evidence supporting pyrethroids affecting human Nav1.7 channels include patch clamp experiments of TE671 cells.

In these experiments, V50.act and Tinact were measured for different concentrations of different members of the pyrethroid group of insecticides.

Which member of the pyrethroid group of insecticides particularly causes a change in these properties when added to a sample of TE671 cells? (1)

What changes are seen? (2)

Write a short conclusion explaining the effect of pyrethroids (particularly permethrin) on Nav1.7 channels in humans. (1)

Answer 125

Permethrin

• Lower V50.act
• Higher Tinact

Permethrin results in a more excitable channel which stays open for longer.

Question 126

Experimental evidence supporting pyrethroids affecting human Nav1.7 channels include patch clamp experiments of TE671 cells.

As well as measuring V50.act and Tinact, tail currents were measured in the presence of different concentrations of different members of the pyrethroid insecticide family.:

• Permethrin
• Deltamethrin
• Cypermethrin
• Tau-flu

Describe the tail currents seen in the presence of these pyrethroids (not taking into account concentrations). (4)

State what was seen in the normal ‘control’ conditions without any pyrethroids added. (1)

Answer 126

Relatively large and long-lasting tail currents seen with DELTAMETHRIN, CYPERMETHRIN, TAU-FLU.

No tail currents with PERMETHRIN.

No tail currents in control groups without pyrethroids added.

Question 127

Experimental evidence supporting pyrethroids affecting human Nav1.7 channels include patch clamp experiments of TE671 cells.

As well as measuring V50.act and Tinact, tail currents were measured in the presence of different concentrations of different members of the pyrethroid insecticide family.:

• Permethrin
• Deltamethrin
• Cypermethrin
• Tau-flu

With some of these pyrethroids, large and long-lasting tail currents were seen. What are these tail currents indicative of? (1)

Answer 127

Ion channels closing more slowly

Question 128

Experimental evidence supporting pyrethroids affecting human Nav1.7 channels include patch clamp experiments of TE671 cells.

As well as measuring V50.act and Tinact, tail currents were measured in the presence of different concentrations of different members of the pyrethroid insecticide family.:

• Permethrin
• Deltamethrin
• Cypermethrin
• Tau-flu

Describe the concentration-dependency of the tail currents seen in the presence of these molecules. (1)

Answer 128

The pyrethroids which showed larger and longer-lasting tail currents (DELTAMETHRIN, CYPERMETHRIN, TAU-FLU) acted in a concentration-dependent manner (higher dose = larger tail current).

Question 129

Fill the gaps relating to insecticides and their effects on humans. (5)

Human Nav1.7 shows sensitivity to ……………………….. at relatively low concentrations.

There is a ………………………. shift in V50.act, ……………………. inactivation, and we also see ……………………….. when looking at the action potential profile.

These features all indicate ………………………………….

Answer 129

pyrethroids

negative

slowed

tail currents

increased excitability

Question 130

Give three electrophysiological findings supporting pyrethroids acting on Nav1.7 channels in humans. (3)

Answer 130

IN PRESENCE OF PYRETHROIDS, NAV1.7 SHOWS…

• Lower V50.act (increased excitability)
• Higher Tinact (longer inactivation)
• Tail currents

Question 131

It is thought that farmers get symptoms such as redness, tingling, and burning due to pyrethroid insecticides acting on Nav1.7 channels.

However, not all farmers get these symptoms.

Describe a theory which would explain why only some farmers experience these symptoms. (3)

Answer 131

• Some farmers could also have mutations in Nav1.7 channel
• Like mutations seen in primary erythromelalgia (which causes similar symptoms)
• Leading to a synergistic effect of mutation + pyrethroids and the appearance of symptoms

Question 132

Give two natural toxins from which neonicotinoid insecticides are developed. (2)

Answer 132

• Nicotine
• Epibatidine

Question 133

Name the plant that produces nicotine as a natural insecticide (common and scientific name). (2)

Answer 133

Tobacco plants

Nicotiana tabacum

Question 134

Epibatidine is a natural neurotoxin produced in the environment, which may act as a starting point for developing insecticides.

How is epibatidine produced in the environment? (1)

What target does it act on? (1)

Answer 134

Produced by Epipedobates tricolour frogs

Acts on nicotinic ACh receptors

Question 135

What target protein do neonicotinoid insecticides act on in the nervous system? (1)

Describe briefly (one word) how neonicotinoids affect this protein. (1)

Answer 135

Nicotinic acetylcholine receptor

Agonists

Question 136

True or false? Explain your answer if appropriate. (1)

Neonicotinoid insecticides are very selective for insect acetylcholinesterase, so they do not pose much risk for humans.

Answer 136

False - they are very selective for insect NICOTINIC ACH RECEPTORS

They do not act on AChE, but the rest is true, they are very selective

Question 137

Fill the gaps relating to neonicotinoid insecticides. (5)

Neonicotinoids act as …………………… at nicotinic ACh receptors.
Because ………………………. cannot break down neonicotinoids like it does with ACh, there is a large ……………….. of function at AChRs because they are persistently ……………………..
This leads to the organism becoming ………………………

Answer 137

agonists

acetylcholinesterase

gain

activated

paralysed

Question 138

Give three reasons why neonicotinoids are particularly effective to use as insecticides. (3)

Answer 138

• Resistance is slow to develop
• They are systemic (incorporate into whole plant)
• Can be applied through seed treatment

Question 139

Neonicotinoids are very effective insecticides, and one reason for this is because they can be applied through seed treatment.

Describe how insecticides are applied through seed treatment and why this is effective. (4)

Answer 139

• Treat seeds with insecticide
• Insecticide distributes throughout plant during growth
• So the whole plant is covered
• And target insects are killed when they feed on the plant

Question 140

Give two advantages and one disadvantage of insecticides like neonicotinoids being applied through seed treatment. (3)

Answer 140

ADVANTAGES:

• Whole plant is covered
• No indiscriminate spraying

DISADVANTAGE:

• Also incorporates into pollen so can affect pollinators such as honeybees

Question 141

Seed treatment with insecticides such as neonicotinoids can affect honeybees by getting into the plant’s pollen.

Describe a legislation which has aimed to protect pollinators such as honeybees from insecticides such as neonicotinoids. (1)

Answer 141

EU enforced ban of some neonicotinoids in 2013

Question 142

Apart from honeybees, there is some concern that other beneficial invertebrates may be at risk from neonicotinoid insecticides.

Give two examples of beneficial invertebrates which may be at risk. (2)

Answer 142

• Earthworms
• Leeches

(Both come under ‘annelid’ category)

Question 143

There is some concern that neonicotinoid insecticides may be a danger to annelids such as earthworms and leeches.

An experiment aimed to test whether annelid muscle nAChRs are sensitive to neonicotinoids. They used a leech muscle contraction assay, with 2 neonicotinoids (imidacloprid, acetamiprid) and 1 butenolide (flupyradifurone).

What would be seen on a control assay when increasing concentrations of ACh are added? (1)

Answer 143

Step-wise contractions with increasing concentrations of ACh

Question 144

There is some concern that neonicotinoid insecticides may be a danger to annelids such as earthworms and leeches.

An experiment aimed to test whether annelid muscle nAChRs are sensitive to neonicotinoids. They used a leech muscle contraction assay, with 2 neonicotinoids (imidacloprid, acetamiprid) and 1 butenolide (flupyradifurone).

What would be seen on a control assay when increasing concentrations of ACh are added in the presence of eserine? (1)

Why would this be seen? (1)

Answer 144

Step-wise contractions which begin at lower concentrations of ACh, than when ACh is added without eserine.

Eserine is an acetylcholinesterase inhibitor so keeps ACh in the synapse/NMJ for longer

Question 145

There is some concern that neonicotinoid insecticides may be a danger to annelids such as earthworms and leeches.

An experiment aimed to test whether annelid muscle nAChRs are sensitive to neonicotinoids. They used a leech muscle contraction assay, with 2 neonicotinoids (imidacloprid, acetamiprid) and 1 butenolide (flupyradifurone).

What would be seen on muscle contraction assays with these three insecticides? (1)

HINT: Same effect is seen for all three

How could we prove that the effects seen were due to activation of the nAChR? (1)

Answer 145

Step-wise muscle contractions with increasing concentrations (this begins at relatively low concentrations of insecticide)

Contractions gradually reduce with addition of increasing concentrations of a competitive nAChR antagonist

Question 146

There is some concern that neonicotinoid insecticides may be a danger to annelids such as earthworms and leeches.

An experiment aimed to test whether annelid muscle nAChRs are sensitive to neonicotinoids. They used a leech muscle contraction assay, with 2 neonicotinoids (imidacloprid, acetamiprid) and 1 butenolide (flupyradifurone).

All of these insecticides caused muscle contractions.

Describe how the ‘strength’ of the effects seen with the insecticides compare to the following situations. (2)

a) If just ACh was added to muscle

b) If ACh + Eserine was added to muscle

Write a short sentence to conclude the effects of insecticides on the nAChR and muscle contraction. (1)

Answer 146

a) effects of insecticides were stronger than just adding ACh

b) effects of insecticides were weaker than with ACh+Eserine

Insecticides have a strong agonistic effect on nAChRs, causing a strong muscle contraction.

Question 147

There is some concern that neonicotinoid insecticides may be a danger to annelids such as earthworms and leeches.

An experiment aimed to test whether annelid muscle nAChRs are sensitive to neonicotinoids. They used a leech muscle contraction assay, with 2 neonicotinoids (imidacloprid, acetamiprid) and 1 butenolide (flupyradifurone).

The insecticides caused strong muscle contractions at relatively low concentrations.

Describe whether the insecticides would be considered full agonists or partial agonists, and explain why. (2)

Answer 147

Full agonists

because they produce the same maximal response as ACh

***However, imidacloprid produced a larger Rmax, so could be considered more than a full agonist

Question 148

Fill the gaps relating to neonicotinoid insecticides. (3)

Neonicotinoids cause substantial ………………………….. in annelids (leeches, earthworms) at relatively low concentrations.
…………………….. insecticides work in the same way.
Like in pests/target insects, the molecular mechanism of the insecticides is …………………………..

Answer 148

muscle contraction

butenolide

agonising the nAChR

Question 149

Give two next steps when investigating and mitigating the effect of neonicotinoid insecticides on beneficial invertebrates like annelids (leeches and earthworms). (2)

Answer 149

• Limit treatment with neonicotinoids to seeds
• More testing of other beneficial invertebrates may be useful