Biology of Bitterness
Read Biology of Bitterness and check the IELTS Reading answers. There is a reason why grapefruit juice is served in little glasses: most people don't want to drink more than a few ounces at a time. Naringin, a natural chemical compound found in grapefruit, tastes bitter. Some people like that bitte…
Passage preview
There is a reason why grapefruit juice is served in little glasses: most people don't want to drink more than a few ounces at a time. Naringin, a natural chemical compound found in grapefruit, tastes bitter. Some people like that bitterness in small doses and believe it enhances the general flavor, but others would rather avoid it altogether. So juice packagers often select grapefruit with low naringin though the compound has antioxidant properties that some nutritionists contend may help prevent cancer and arteriosclerosis.
Vocabulary from this passage
10 words worth learning before you sit the test, each with the sentence it appears in.
- averse adjective
Having a strong dislike of or opposition to something
Most investors are risk-averse and prefer stable returns over high volatility.
- cascade noun
A process whereby something, typically information or knowledge, is successively passed on
The failure of the bank triggered a cascade of economic problems throughout the region.
- coax verb
To persuade someone gradually or by flattery to do something; to manipulate with great care
The negotiator tried to coax a compromise from the opposing factions.
- cull verb
To select from a large quantity; to obtain from a variety of sources
The data was culled from several independent studies conducted over a decade.
- dampen verb
To make something less strong or intense; to reduce or suppress
The government raised interest rates to dampen inflation.
- derive verb
To obtain something from a specified source; to arise from
Many English words derive from Latin or Greek roots.
- foolproof adjective
Incapable of going wrong or being misused; completely reliable
Security experts warn that no biometric system is entirely foolproof.
- palatable adjective
Pleasant to taste; acceptable or satisfactory to the mind or feelings
The proposed tax increase was not palatable to the general public.
- receptor noun
A specialized cell or organ that detects a stimulus and sends a signal to a sensory nerve
The drug works by blocking specific receptors in the brain to reduce pain.
- repellent adjective
Causing disgust or distaste; able to repel a particular thing
Many insects find the scent of certain plants repellent.
Answers with explanations
- 27. B
The prompt seeks an **experiment** involving bitterness. Paragraph B explicitly describes the author participating in a **test conducted** at the Linguagen Corporation where participants tasted different cups of juice to evaluate bitterness blockers.
- 28. I
The prompt looks for the **future application** of the technology. Paragraph I discusses future possibilities, noting that **In a few years**, companies might develop a **bitter blocker in a bottle** that consumers can use themselves at home.
- 29. C
The prompt asks how humans and animals interpret bitterness differently. Paragraph C explains this biological divergence: while **every other species is averse** to bitterness as a warning of poison, **humans are the only species that enjoys** it.
- 30. E
The prompt seeks the biological **spread process** of tasting bitterness. Paragraph E details this internal **cascade of chemical reactions**, explaining how a signal is received, relayed via G proteins, and **ultimately delivers a signal to the brain**.
- 31. G
The prompt requires the mechanism of how AMP blocks bitterness. Paragraph G explains exactly how the compound works: instead of changing the food, it **attaches to bitter-taste receptors**, physically blocking them from receiving bitter signals.
- 32. H
We need to find how blockers lower an **unhealthy impact**. Paragraph H explains that AMP will help make processed foods **less unhealthy** by allowing manufacturers to reduce high sodium levels, replacing salt with potassium chloride and masking its bitter aftertaste.
- 33. A
The prompt refers to bitterness introduced from a **fruit**. Paragraph A introduces the topic by discussing **grapefruit**, specifically noting that it contains a natural chemical compound called Naringin that inherently **tastes bitter**.
- 34. D
The prompt looks for the link between genetics and taste sensitivity. Paragraph D explicitly states that people's capacities for tasting bitterness vary greatly and that these **differences appear to be genetic**.
- 35. naringin
The summary requires the name of the substance in grapefruit causing the bitter taste. Paragraph A explicitly identifies **Naringin** as the natural chemical compound in grapefruit that **tastes bitter**. This fulfills the noun requirement for the blank.
- 36. poisonous
The summary discusses the biological role of bitterness for plants as a warning signal. Paragraph C explains that bitter compounds protect animals by letting them know when a plant may be **poisonous**. This adjective grammatically completes the sentence.
- 37. supertasters
The summary refers to a specific group of people with high sensitivity. Paragraph D states that individuals known as **supertasters** are especially sensitive to bitter compounds. The noun fits the plural verb 'have' in the sentence perfectly.
- 38. taste buds
The summary asks what biological feature supertasters have in abundance. Paragraph D explains their sensitivity is due to having an **unusually high number of taste buds**. The two-word phrase fits the blank accurately.
- 39. A
The question asks for the primary function of AMP. The passage clearly defines AMP as a compound that **blocks the bitterness in foods**. This perfectly matches the correct option about **offsetting bitter flavour**. Distractors are incorrect as AMP itself 'has no bitterness of its own' and does not create a citrus flavor.
- 40. D
The question asks about the specific role of the G protein. The text states that once a bitter signal is received, it is **relayed via G proteins**, which triggers reactions that **delivers a signal to the brain**. This aligns perfectly with the option about **transmitting signals**. Distractors about collecting molecules are incorrect, as that is the function of receptors.