B3 Flashcards
What is a tissue made up of?
A group of similar cells that work together to carry out a particular function.
What are organs made of?
A group of different tissues that work together to perform a certain function.
What is an organ system?
A group of organs working together to perform a particular function.
What are enzymes?
They act as biological catalysts which reduce the need for high temperatures and we only have enzymes to speed up the useful chemical reactions in the body.
What is a catalyst?
A substance which increases the speed of a reaction without being changed or used up in the reaction.
What are enzymes made from?
Large proteins
How do enzymes work?
Enzymes have an active site with a unique shape that fits onto substances involved in a reaction.
They only catalyse one specific reaction.
For the enzyme to work, the substrate has to fit into its active site. If the substrate doesn’t match the enzyme’s active site, then the reaction won’t be catalysed.
What is the model that shows how an enzyme works?
The ‘lock and key’ model.
How does temperature affect the rate of an enzyme-catalysed reaction?
If the temperature gets too hot, some of the bonds holding the enzyme together break. This changes the shape of the enzyme’s active site, so the substrate won’t fit any more. The enzyme is said to be denatured.
All enzymes have an optimum temperature that they work best at.
How does the pH affect the enzymes?
If it’s too high or too low, the pH interferes with the bonds holding the enzyme together. This changes the shape of the active site and denatures the enzyme.
All enzymes have an optimum pH that they work best at. It’s often neutral pH 7 but not always.
What enzyme breaks down starch?
Carbohydrase e.g. amylase
What is starch broken down into?
Maltose and other sugars
Where is amylase made?
The salivary glands
The pancreas
The small intestine
What enzyme breaks down proteins?
Protease
Made in:
The stomach (it’s called pepsin there)
The pancreas
The small intestine
What are proteins broken down into?
Amino acids
What enzyme breaks down lipids?
Lipase
Made in:
The pancreas
The small intestine
What are lipids broken into?
Glycerol and fatty acids
What does bile do?
Bile is produced in the liver and is stored in the gall bladder before it’s released int the small intestine.
The hydrochloric acid in the stomach makes the pH too acidic for enzymes in the small intestine to work properly. Bile is alkaline - it neutralises the acid and makes conditions alkaline.
The enzymes in the small intestine work best in these alkaline conditions.
It emulsifies fats (its breaks the fat into tiny droplets). This gives the fat a much bigger surface area for the enzyme lipase to work on - which makes its digestion faster.
What are the salivary glands?
These produce amylase enzyme in the saliva.
What is the stomach?
It pummels the food with its muscular walls.
It produces the protease enzyme, pepsin.
It produces hydrochloric acid for two :
To kill bacteria
To give the right pH for protease enzyme to work
What is the liver?
Where bile is produced.
What is the pancreas?
Produces protease, amylase and lipase enzymes. It releases these into the small intestine.
What is the large intestine?
Where excess water is absorbed from the food.
What is the small intestine?
Produces protease, amylase and lipase enzymes to complete digestion.
This is where the digested food id absorbed out of the digestive system into the blood.
What is the rectum?
Where faeces (made up mainly of indigestible food) are stored before they exit through the anus.
How do you get a food sample?
Get a piece of food and break it up using a pestle and mortar.
Transfer the ground up food to a beaker and add some distilled water.
Give the mixture a good stir with a glads rod to dissolve some of the food.
Filter the solution using a funnel lined with filter paper to get rid of the solid bits of food.
How do you test for reducing sugars in foods?
Prepare a food sample and transfer 5cm3 to a test tube.
Prepare a water bath so that it’s set to 75°C.
Add some Benedict’s solution to the test tube (about 10 drops) using a pipette.
Place the test tube in the water bath using a test tube holder and leave it in there for five minutes. Make sure the test tube is pointing away from you.
If the food sample contains a reducing sugar, the solution in the test tue will change from the normal blue colour to green, yellow, or brick-red - it depends on how much sugar is in the food.
How do you test for starch?
Make a food sample and transfer 5cm3 to a test tube.
Then add a few drops of iodine solution and gently shake the tube to mix the contents. If the sample contains starch, the colour of the solution will change from browny-orange to black or blue-black.
How to test for proteins?
Prepare a food sample and tranfer 2 cm³ of your sample to a test tube.
Add 2 cm³ of biuret solution to the sample and mix the contents of the tube by gently shaking it.
If the food sample contains protein, the solution will change from blue to purple.
How to test for lipids?
Add a few drops of ethanol to the food solution.
Shake the test tube gently and leave for one minute.
Pour the ethanol solution into another test tube containing water.
lf the top of the solution turns cloudy, the food contains lipids.
