The Digestive System – TEST IT!
1.
Scientists can use a glucose biosensor to test for the concentration of glucose in a solution. It consists of the enzyme glucose oxidase.
a) A glucose biosensor only picks up glucose. Explain why using what you know about hoe enzymes function.
b) When testing for glucose in a blood sample it’s better to use a biosensor as opposed to the Benedict’s test. Give two reasons why.
i. _________________________________________________
ii. _________________________________________________
2.
Enzymes are a major part of the digestive process.
a) Describe their role in the complete breakdown of the carbohydrate, starch.
b) Carbohydrate is broken down into glucose.
i. How is glucose absorbed?
ii. Describe the process.
3.
Cholera bacteria are prokaryotic cells.
a) Name two structures found in prokaryotic but not eukaryotic cells.
i. _________________________________________________
ii. _________________________________________________
b) Cholera travels into the small intestine where it causes an increase in the secretion of chloride ions into this organ. Using what you know about water potential, how could this increase lead to diarrhoea?
c) Oral rehydration solutions (ORS) consist of a powder and are used to help replace lose fluid. The powder needs to be mixed with water. Why should boiled water be used to mix?
d) ORS contains glucose. Name one other substance that needs to be included.
ANSWERS
1.
a) An enzyme has an active site specific to its substrate. Only glucose has the correct shape and will bind to the active site.
b) Answers include:
i. The Benedict’s test detects all reducing sugars
ii. The biosensor provides a reading not just a colour change
iii. The biosensor is more sensitive and can detect lower concentrations of glucose
iv. The biosensor can monitor blood glucose at a continuous rate
v. The red colour of the blood would mask the results
2.
a) In the mouth, salivary amylase begins to digest the starch. Although not much digestion takes place it helps to rid the mouth of starch which helps prevent bacterial infection. The rest of the starch is digested by pancreatic amylase in the duodenum to create maltose, a disaccharide. Disaccharides are digested in monosaccharides by disaccharidases: maltose by maltase, sucrose by sucrase, and lactose by lactase.
b)
i. Coupled active transport
ii. The active transport protein, sodium potassium ATPase, works by constantly pumping potassium ions in and sodium ions out of the cell. It requires ATP to hydrolyse in order to function as the sodium ions are being pumped up their concentration gradient. The sodium-glucose co-transporter protein is the facilitated diffusion protein. This consists of two binding sites: one for sodium ions and one for glucose. This protein uses diffusion, therefore passive transport. Due to the high concentration of sodium ions outside the cell both glucose and sodium are transported into the cell: the sodium ions down their concentration gradient and the glucose molecules against their concentration gradient. The sodium gradient is restored by the sodium-potassium ATPase.
3.
a) Answers include:
i. capsule
ii. circular DNA
iii. plasmid
iv. flagellum
v. pilus
vi. 70S ribosomes
b) The water potential becomes more negative in the intestine so water enters the intestine from the cells by osmosis.
c) To kill any bacteria in the water so that it’s sterile to drink.
d) Answers include:
i. sodium ions
ii. potassium ions
iii. chloride ions
iv. citrate ions