Organisation Flashcards
definition of enzyme
biological catalyst that speeds up the rate of a chemical reaction without being altered or used up itself in the reaction
definition of active site
small dent on the surface of the enzyme where the substrate binds and where the chemical reaction takes place.
State what type of molecule enzymes are
Proteins
large molecule made from many amino acids joined together
State 4 factors that affect the activity of enzymes
pH
temperature
concentration of enzyme
concentration of substrate
State the two different types of chemical reaction
Catabolic
Anabolic
Definition of a catabolic reaction
chemical reaction that breaks down larger molecules into smaller molecules
Definition of an anabolic reaction
A chemical reaction that builds up smaller molecules into a larger molecules (the product)
Define the term metabolism
sum total of all chemical reactions that take place inside a cell
(includes all the catabolic and anabolic reactions)
Describe the structure of an enzyme
enzyme has a dip on its surface (called the active site)
The active site has a complementary shape to its specific substrate
Explain why enzymes are specific
Each enzyme has an active site unique to specific substrates for one chemical reaction
active site is only complementary to one substrate
Hence each enzyme can only catalyse one specific reaction
Describe the relationship between the active site and the substrate
complementary to each other
Name the model that describes how enzymes work
Lock and key theory
Explain the lock and key theory model
active site on enzyme acts as a lock
complementary substrate acts as a key that fits into the active site
chemical reaction then takes place
The substrate is converted to the product
The product is released
The enzyme remains unaltered and can carry out further identical reactions
Define the term enzyme-substrate complex
An enzyme that has it specific substrate bound to its active site
Explain the effect of low temperatures on enzyme activity
substrate and enzyme have very little kinetic energy
very few collisions between the substrate and the active site
Very few enzyme-substrate complexes form
very little product is made
enzyme is described as inactive
The rate of reaction is very low
Explain the effect of high temperatures on enzyme activity
substrate and enzyme have a high amount of kinetic energy
many collisions between the substrate and the active site
high temperature changes the shape of the enzyme
alters the shape of the active site
substrate is no longer complementary to the active site
NO enzyme-substrate complexes form
NO product is made
The enzyme is described as denatured
The rate of reaction is zero
Describe the effect the optimum temperatures on enzyme activity
both the substrate and enzyme have very high kinetic energy
many collisions between the substrate and the active site
High numbers of enzyme-substrate complexes form
lot of product is made
enzyme is described as working at its maximum rate
The rate of reaction is at its maximum
What is the typical optimum temperature for human enzymes?
37oC
Name an human enzyme that works at an optimal pH of 1-2 (acidic)
Pepsin
State 2 human enzymes that work at an optimal pH of 7 (neutral)
Amylase
Catalase
Lipase
Carbohydrases
Proteases (except trypsin)
How do you calculate the rate of reaction?
Amount of product formed divided by the time
State the 3 main groups of enzymes that are involved in digestion
Lipases
Carbohydrases
Proteases
Describe the action of a protease enzyme
break proteins down into amino acids
Describe the action of a lipase enzyme
break lipids down into 3 fatty acids and 1 glycerol
Describe the action of a carbohydrase enzyme
break complex carbohydrase down into simpler sugars (e.g. glucose)
State how you can investigate the effect on pH on enzymic activity
- put a drop of iodine solution into every well of a spotting tile
- place bunsen burner on a heat-proof mat and a tripod and gauze over bunsen burner
- heat beaker of water until its 35 degrees
- add 1cm of amylase solution and 1cm of buffer solution to a boiling tube and put in the water
- mix
- record and repeat
what do digestive enzymes do
convert food into small soluble molecules that can be
absorbed into the bloodstream.
State 3 places in the human body where amylase is produced
Mouth (salivary amylase)
Pancreas
Small intestine
State 3 places in the human body where proteases are produced
Pancreas
Stomach
Small intestine
State 2 places in the human body where lipase is produced
Pancreas
Small intestine
Describe what happens to the fatty acids and glycerol that are produced after digestion
fatty acids and glcyerol are absorbed into the blood stream
This absorption occurs in the small intestine
They are absorbed into the lacteals
then used by cells to make new lipids
The new lipids are used to make new cell membranes for the production of new cells or stored for energy
What is the function/role of bile?
- neutralises stomach acid
- emulsifies lipids
It breaks large lipids into smaller droplets of lipid
This increases the surface area for the lipase enzymes
Hence the rate of reaction increases
How does the emulsification of lipids affect the activity of lipases?
Emulsifying the fats into smaller droplets increases the surface area
This increases the activity of lipase
Explain why the pH falls (becomes more acidic) in during a reaction catalysed by lipase
Lipase breaks down lipids into 3 fatty acids and glycerol
As more lipids are broken down more fatty acids are produced
The greater the accumulation of fatty acids the more the pH decreases (becomes more acidic)
State where bile is stored
Gall bladder
Explain why it is important bile is released into the small intestine to allow digestion to occur
- hydrochloric acid in the stomach makes the pH too acidic for enzymes in the small intestine to work properly
- bile is alkaline so neutralises the acid and makes conditions alkaline
- enzymes work best in these alkaline conditions
State where bile is produced
Liver
What test would you use to detect the presence of reducing sugars?
Benedict’s test
Describe the results of a positive Benedict’s test
solution would change from blue to green to yellow to orange to brick red
What colour is a negative Benedict’s test?
Blue
Describe how to carry out a Benedict’s test
1) prepare a food sample and transfer 5cm to a test tube
2) prepare a water bath so it is set to 75 degrees
3) Add 10 drops of Benedict’s solution to test tube using a pipette
4) Place test tube in water bath and leave for 5 mins
State 3 safety precautions you should take when carrying out a Benedict’s test
- Wear safety goggles
- Make sure the test tube is pointing away from you in the water bath
- Do not ingest the Benedict’s solution – it is harmful
What test would you use to detect the presence of starch?
Iodine solution
Describe the results of a positive starch test
A blue-black solution
What colour is a negative starch test?
A yellow-brown solution
Describe how to carry out a starch test
1) make a food sample and transfer 5cm to a test tube
2) add a few drops of iodine solution and shake the tube to mix contents
What test would you use to detect the presence of lipids?
Sudan III stain solution
Describe the results of a positive Sudan III test
2 layers will form
The top layer will be bright red
Describe the results of a negative Sudan III test
No separate red layer will form
Describe how to carry out a Sudan III test
- prepare a sample of food and transfer 5cm to a test tube
- using pipette add 3 drops of Sudan III stain solution to test tube and shake it
What test would you use to detect the presence of proteins?
Biuret solution
Describe the results of a positive Biuret test
Purple solution
Explain the purpose of digestion (3 key points)
- To use enzymes to break down large insoluble molecules
- into small and soluble molecules
- that can be absorbed into the bloodstream
Describe the results of a negative Biuret test
Blue solution
Describe how to carry out a Biuret test
- prepare a sample of your food and transfer 2cm to a test tube
- add 2cm of biuret solution to the sample and gently shake it
Give 2 properties that amino acids, glycerol, simple sugars and fatty acids have that enable them to be absorbed into the plasma
Small and soluble
