Digestion and how nutrients reach the blood
Grade 9 Science Worksheet
Circle the best answer.
Ari eats a slice of bread. Salivary amylase starts breaking the starch in the mouth. What happens to that amylase in the stomach?
- It switches to digesting protein, since one enzyme works on any food
- Acid stops it, so starch digestion resumes in the small intestine
- It keeps working at the same rate, since acid does not matter to enzymes
- It is used up in the mouth, so no amylase is left
Bo eats a bowl of beans. In what order do enzymes digest the protein in them?
- Lipase in the mouth, then amylase in the stomach
- Pepsin in the stomach and again in the small intestine, since one enzyme finishes the job
- Pepsin in the stomach, then trypsin from the pancreas in the small intestine
- Trypsin in the stomach, then pepsin from the pancreas in the small intestine
Esme drinks a glass of milk. Lactase on the small intestine lining splits the milk sugar, lactose. What does it make?
- Glucose and galactose, which can be absorbed
- Two glucose units, which can be absorbed
- Glucose and fructose, which can be absorbed
- Fatty acids and monoglycerides, which can be absorbed
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 ?.
Jun eats a bowl of rice. Glucose from its starch is absorbed. Which route takes the glucose out of the small intestine?
- 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
- Through the large intestine wall into the blood, then to the liver and the body
- Into a villus capillary, then the hepatic portal vein to the liver
Luz traces the sugars from a banana. Which organ goes in the box marked ?
- The gallbladder, which stores the sugars until they are needed
- The large intestine, where most sugars are absorbed into the blood
- The liver, which receives blood from the small intestine
- The stomach, where most sugars are absorbed into the blood
Both tubes began with the same starch and were kept at the same temperature. Milo reads a model starch test. What does the data show about amylase?
- The amylase in tube 1 is used up after 5 minutes, so starch stops falling
- Starch rises in tube 1, because amylase makes more starch from sugar
- Both tubes lose starch, but tube 1 loses it faster and ends lower
- Amylase lowers starch from 100 to 10; the water-only tube stays at 100
“A micrometer (µm) is one thousandth of a millimeter (mm)” Pia reads the lining card. Which statement matches it?
- 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
- Villi are smaller than microvilli, and there are more of them per mm²
Ren asks why the small intestine lining has villi and microvilli. What do they do for absorption?
- They make bile, which then carries the nutrients into the blood
- They grind food into smaller pieces, so the enzymes work much faster
- They add surface area, so more nutrients touch absorbing cells
- They squeeze water out of the food, so the waste is much drier
Tala eats cheese. Bile helps lipase digest its fat. Why does lipase work faster with bile?
- 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
- Bile breaks large fat globules into droplets, so lipase reaches more fat
- Chewing already broke the fat into tiny droplets, so bile adds little
By the time leftovers reach the large intestine, nearly all nutrients are already absorbed. Zee asks what it mostly absorbs.
- Fat droplets, which it digests with bile
- Starch, which it digests with amylase
- Most of the sugars and amino acids, through its villi
- Water and salts, taken from the leftover material