Digestion: make soluble products, then absorb them
| English | 中文 | Pinyin |
|---|---|---|
| digestion/daɪˈdʒestʃn/ | 消化 | xiāo huà |
| emulsification/ɪˌmʌlsɪfɪˈkeɪʃn/ | 乳化 | rǔ huà |
What would explain this observation?
- Chewing makes food pieces smaller, but digestive enzymes change large food molecules into soluble products. Mechanical breakdown and chemical digestion 消化 have different effects.
- Start with a prediction. State the quantities or features you would compare, then decide what evidence could distinguish two explanations.
Build the model
- The mouth, oesophagus, stomach and intestines form a digestive pathway. Amylase from salivary glands, pancreas and small intestine breaks starch into sugars. Proteases produced in stomach, pancreas and small intestine digest proteins into amino acids. Lipases from pancreas and small intestine break lipids into glycerol and fatty acids. Small soluble products can be absorbed, mainly through the small intestine.
- digestion: Breakdown of food molecules into smaller soluble products; emulsification 乳化: Breaking a liquid into smaller droplets without the digestive reaction itself.
How does bile help lipid digestion?
Bile is made in the liver and stored in the gall bladder. Its alkaline character helps neutralize stomach acid entering the small intestine. It emulsifies fat into small droplets, increasing surface area for lipase. Bile is not an enzyme. Digestion products can build new carbohydrates, proteins and lipids, and some glucose is used in respiration.
Match each technical term to its precise meaning.
Use the definitions to distinguish related quantities and processes.
Choose evidence that can test it
- Bile is made in the liver and stored in the gall bladder. Its alkaline character helps neutralize stomach acid entering the small intestine. It emulsifies fat into small droplets, increasing surface area for lipase. Bile is not an enzyme. Digestion products can build new carbohydrates, proteins and lipids, and some glucose is used in respiration.
- Trace one food molecule from a digestive site through a named enzyme to its products, then to absorption and use. Use simple word equations at GCSE: protein → amino acids, and lipid → glycerol + fatty acids. AQA does not require chemical symbol equations for these digestion reactions.
Which two habits make the investigation or model in this case more defensible?
Trace one food molecule from a digestive site through a named enzyme to its products, then to absorption and use. Use simple word equations at GCSE: protein → amino acids, and lipid → glycerol + fatty acids. AQA does not require chemical symbol equations for these digestion reactions.
Work from known quantities
- State the known values and their units. Choose the relation because its assumptions fit this case, then rearrange before substitution.
- Known: a model contains 12 identical fat droplets that are divided into 48 smaller droplets while total fat amount stays the same. Droplet count rises fourfold. The increased exposed area can increase lipase action under matched conditions, but counting droplets alone cannot calculate their total area without size information.
A model divides 15 fat droplets into 60 smaller droplets. Calculate the count ratio final/initial. Use the same sequence: known quantities → model → relation → substitution → unit and interpretation.
A model divides 15 fat droplets into 60 smaller droplets. Calculate the count ratio final/initial.
The result is 4 . Known: a model contains 12 identical fat droplets that are divided into 48 smaller droplets while total fat amount stays the same. Droplet count rises fourfold. The increased exposed area can increase lipase action under matched conditions, but counting droplets alone cannot calculate their total area without size information.
Check the conclusion and its limits
- Absorption does not mean breaking the food molecule down. Bile helps lipase but does not itself digest lipid. The stomach is not the main site where every nutrient is absorbed, and digested food does not travel through the trachea.
- Return to the original observation. Explain what the result supports, which conditions it assumes, and one way to test a competing explanation.
Bile is a digestive enzyme that hydrolyses every food molecule. This claim is false: Absorption does not mean breaking the food molecule down. Bile helps lipase but does not itself digest lipid. The stomach is not the main site where every nutrient is absorbed, and digested food does not travel through the trachea.
Digestion: make soluble products, then absorb them: Bile is made in the liver and stored in the gall bladder. Its alkaline character helps neutralize stomach acid entering the small intestine. It emulsifies fat into small droplets, increasing surface area for lipase. Bile is not an enzyme. Digestion products can build new carbohydrates, proteins and lipids, and some glucose is used in respiration.
Bile is a digestive enzyme that hydrolyses every food molecule.
Absorption does not mean breaking the food molecule down. Bile helps lipase but does not itself digest lipid. The stomach is not the main site where every nutrient is absorbed, and digested food does not travel through the trachea.
Breakdown of food molecules into smaller soluble products: write the technical term.
digestion means Breakdown of food molecules into smaller soluble products.