B3 - Digestion Flashcards
What is a tissue?
A group of cells with similar structure/function
What is an organ?
A group of tissues that perform a specific function together
What are enzymes?
Biological catalysts with a specific active site that speed up reactions
What is the first organ in the digestive system and what is its role?
- Food chewed in mouth
- Mouth enzymes in saliva begin to digest starch and break it down into smaller sugar molecules
How does the food travel from the mouth into the stomach? What happens in there?
- food passes down oesophagus to stomach
- enzymes begin digestion of protein
- stomach has hydrochloric acid that helps digest proteins
- stomach muscles churn the food and turn it into a liquid, increasing surface area for enzymes to digest
What happens after food has left the stomach?
- fluid passes to small intestine
- pancreas releases enzymes into intestine, continue digestion of starch and proteins and lipids
- liver releases bile into intestine to speed up digestion of lipids, bile neutralises acid from the stomach
- small molecules are absorbed into the bloodstream by diffusion/active transport
What are the substances that can diffuse through the cell membrane?
Glucose, water, oxygen and amino acids ( acids that form together to make proteins)
What substances cant diffuse through cell membranes?
Proteins and starch molecules, too big
Where does the food go after the small intestine?
Food ends up in large intestine where water is absorbed into the bloodstream, the faeces are released from the body through the anus
How does an enzyme work?
- Lock and key model - each substrate fits into the active site of the enzyme, substrate binds together as they fit together
- The enzyme breaks down the substrate into products
The reaction can continue to happen in it, until the enzyme becomes denatured- it changes shape.
What effect does temperature have on enzyme activity?
Temperature increases=rate of reaction increases
Optimum temperature - reaction works as fast as possible
After optimum temperature enzyme begins to denature and stops working
How are enzymes denatured by temperature?
- the high temperature causes the protein chains to unravel
- changes shape of active site
Why do enzymes have an optimum pH?
- Forces holding the protein chains in position are affected by pH
- A change in pH can change the shape of the active site
What 3 places is amylase made in? Its function?
- Made in: salivary glands, pancreas, small intestine
- Function: breaking down starch into glucose
What 3 places is protease made in? Its function?
- Made in: stomach, pancreas, small intestine
- Function: breaking down proteins into amino acids
What 2 places is lipase made in? Its function?
- Made in: pancreas, small intestine
- Function: breaking down lipids into fatty acids and glycerol
What is the general function of digestive enzymes?
To food into small soluble molecules that can be absorbed into the bloodstream
What are products of digestion used for?
Used to build new carbohydrates, lipids and proteins
What enzyme breaks down carbohydrates?
Carbohydrases break down into simple sugars
What 2 places is starch digested in the body?
Mouth
Small intestine
What 2 places is protein digested in the body?
Stomach
Small intestine
What place is fat digested in the body?
Small intestine
Why is starch not digested in the stomach?
Stomach has no amylase
Conditions are too acidic for amylase to work
How can the mouth break down starchy foods?
Teeth break down food
Saliva has amylase
Where is bile made?
Liver
Where is bile stored?
Gall bladder
What is bile? How does it help in digestion?
- Alkaline to neutralise hydrochloric acid in the stomach
- Emulsifies fat into small droplets, increases surface area increasing breakdown of fat by lipase
Explain how protein is digested
1) First broken down mechanically into smaller pieces by chewing in the mouth
2) Protease enzymes break down protein in the stomach and small intestine
3) Protease broken down into amino acids
Food test 1 - what is the test for starch?
- solid food groud up using pestle and mortar and add to water
- add iodine to sample
- iodine present = yellow–>blue/black
Food test 2 - what is the test for sugar?
-make food solution
-place 2cm^3 of solution in test tube
- 10 drops of benedicts solution (blue)
- warm solution with hot water bath
- green= small amount of sugar
-yellow= some amount of sugar
-brick red = a large amount of sugar
Food test 3 - what is the test for proteins?
-make food solution
-place 2cm^3 of solution in a test tube
-add 2cm^3 of biuret solution (blue)
- change from blue to purple /lilac
Food test 4 - what is the test for lipids?
- grind food with mortar and pestle and add distilled water, but don’t filter as lipid molecules can stick to filter paper
- put 2cm^3 of food solution into test tub
- add few drops of distilled water and few drops of ethanol
- gently shake solution
- if present, solution will turn cloudy
Required Practical 5: investigate the effect of pH on the rate of reaction of amylase enzyme
How is the small intestine adapted for absorption?
Walls covered in villi and each villus is covered in microvilli. These increase the surface area for absorption
The wall of the small intestine is very thin which shortens the diffusion path
Villi have a very rich blood supply which maintains a steep concentration gradient for diffusion to occur rapidly
What is the role of the liver in digestion?
The liver produces bile, which emulsifies lipids and breaks lipids into small droplets,
aiding their absorption
What is the role of the pancreas in digestion?
The pancreas produces digestive juices, including enzymes used in chemical digestion of proteins, lipids and carbohydrates
Food test 2 - what is the test for glucose?
- solid ground up using pestle and mortar and added to water
- add benedicts reagent to food sample
- heat with bunsen burner/hot water bath
- glucose present = red, orange, green or yellow
Food test 3 - what is the test for protein?
- solid ground up using pestle and mortar and add to water
- add birute reagent to food sample
- protein present = blue–>purple/lilac
Food test 4 - what is the test for lipids?
- solid ground up using pestle and mortar and add water - don’t filter as lipid molecules can stick to paper
- add a few drops of water and ethanol to solution
- gently shake solution
- lipids present=colourless—>cloudy
Required practical 5 - investigating enzymes
- Add iodine solution to each well in spotting tile
- In water bath at set temperature, add 2cm^3 of starch, amylase and pH buffer solution(5) and leave for 5 minutes
- Mix all 3 solutions together and stir
- Return to water bath and start stopwatch
- Every 30 seconds add a few drops to spotting tile using pipette
- Repeat using different pH buffers
Why would you expect it to take longer for starch to disappear at lower temperatures?
- Molecules have low kinetic energy so fewer collisions between starch and amylase
How could you use this experiment to determine the pH amylase works best in?
- look for quickest time iodine stopped turning blue/black
