Digestion and how nutrients reach the blood

Grade 9 Science Worksheet

Circle the best answer.

1. 1.

   Ari eats a slice of bread. Salivary amylase starts breaking the starch in the mouth. What happens to that amylase in the stomach?

   • Acid stops it, so starch digestion resumes in the small intestine
   • It is used up in the mouth, so no amylase is left
   • It switches to digesting protein, since one enzyme works on any food
   • It keeps working at the same rate, since acid does not matter to enzymes
2. 2.

   Bo eats a bowl of beans. In what order do enzymes digest the protein in them?

   • Pepsin in the stomach, then trypsin from the pancreas in the small intestine
   • Pepsin in the stomach and again in the small intestine, since one enzyme finishes the job
   • Trypsin in the stomach, then pepsin from the pancreas in the small intestine
   • Lipase in the mouth, then amylase in the stomach

3. Read this first

   Map (model, not to scale)

   Glucose from rice starts in the small intestine and ends in a muscle cell. The route between the two boxes is marked ?.

4. 3.

   Jun eats a bowl of rice. Glucose from its starch is absorbed. Which route takes the glucose out of the small intestine?

   • Into a villus capillary, then the hepatic portal vein to the liver
   • Through the large intestine wall into the blood, then to the liver and the body
   • Into a lacteal, then the lymph vessels that carry it on to the blood
   • Through the stomach wall into the blood, then to the liver and the body

5. Map (model, not to scale)

   Fatty acids and monoglycerides from nut oil start in the small intestine and end in the bloodstream. The route between the two boxes is marked ?.

6. 4.

   Kira eats a handful of nuts. Long-chain fatty acids and monoglycerides from the oil are absorbed. Which route do they take?

   • Through the stomach wall into the blood, then to the liver
   • Through the large intestine wall into the blood, then to the liver
   • Into a lacteal, then lymph vessels, then the bloodstream
   • Into a villus capillary, then the hepatic portal vein to the liver
7. 5.

   Luz traces the sugars from a banana. Which organ goes in the box marked ?

   • The large intestine, where most sugars are absorbed into the blood
   • The gallbladder, which stores the sugars until they are needed
   • The stomach, where most sugars are absorbed into the blood
   • The liver, which receives blood from the small intestine
8. 6.

   Noah reads a model of a folded lining. How does folding change the area of the strip?

   • Each fold adds 40 cm², so 10 folds give 440 cm², eleven times the flat strip
   • Folding keeps the area at 40 cm², since the folded strip is the same paper as before
   • Each fold adds 8 cm², so 10 folds give 120 cm², three times the flat strip
   • Each fold adds 4 cm², so 10 folds give 80 cm², twice the area of the flat strip
9. 7.

   “A micrometer (µm) is one thousandth of a millimeter (mm)” Pia reads the lining card. Which statement matches it?

   • Villi are smaller than microvilli, and there are more of them per mm²
   • There are more villi than microvilli per mm², since villi are bigger
   • Villi and microvilli are about the same size and number
   • Microvilli are far smaller than villi, but far more numerous per mm²
10. 8.

    Ren asks why the small intestine lining has villi and microvilli. What do they do for absorption?

    • They add surface area, so more nutrients touch absorbing cells
    • They squeeze water out of the food, so the waste is much drier
    • They make bile, which then carries the nutrients into the blood
    • They grind food into smaller pieces, so the enzymes work much faster
11. 9.

    Tala eats cheese. Bile helps lipase digest its fat. Why does lipase work faster with bile?

    • Bile breaks large fat globules into droplets, so lipase reaches more fat
    • Bile is an enzyme that itself splits the fat into fatty acids and glycerol
    • Bile neutralizes the stomach acid, so that lipase can finally reach the fat
    • Chewing already broke the fat into tiny droplets, so bile adds little
12. 10.

    By the time leftovers reach the large intestine, nearly all nutrients are already absorbed. Zee asks what it mostly absorbs.

    • Starch, which it digests with amylase
    • Water and salts, taken from the leftover material
    • Fat droplets, which it digests with bile
    • Most of the sugars and amino acids, through its villi