Enymes Flashcards
bbc bitesize
Active site
def
The part of the enzyme to which a specific substrate can attach to or fit on to
Catalyst
def
A substance that changes the rate of a chemical reaction without being changed or used up by the reaction itself
Carbohydrate
def
Food belonging to the food group consisting of sugars, starch and cellulose. Carbohydrates are vital for energy in humans and are stored as fat if eaten in excess. in plants carbohydrates are important for photosynthesis
Amino acid
def
The building blocks that makes up a protein molecule
Iodine solution
A solution of iodine in potassium iodine solution, also referred to as potassium triiodide solution
Benedict’s solution
A solution that can be used to test for the presence of a reducing sugar (or the presence of an aldehyde group)
Biuret reagent
Chemical which turns purple or maybe in the presence of protein
Calorimeter
def
A machine used to measure the energy involved in a chemical process
calorimetry
def
Measuring the amount of heat given out or taken in by a process, such as the combustion of a fuel
collagen
def
The most common protein found in connective tissue of animals
Concentration
def
The concentration of a solution tells us how much of a substance is dissolved in water. The higher the concentration, the more particles of the substance are present.
Emulsion
def
Cloudy mixture formed between a lipid and water
Enzyme
def
Enzymes are proteins that function as biological catalysts. So, they are molecules that speed up a chemical reaction without being changed by the reaction.
Fats
def
Naturally occurring compounds of carbon, hydrogen and oxygen. They are esters made from fatty acids and glycerol
fructose
def
A monosaccharide which joins with glucose to make sucrose
Glucose
def
A simple sugar used by cells for respiration
Glycerol
def
A soluble carbohydrate which is coverted into glucose by the liver
Glycogen
def
The storage form of glucose in animal cells
Haemoglobin
def
The red protein found in red blood cells that transports oxygen round the body
Joules
def
The unit of work or energy, written as J
Keratin
def
A fibrous protein found in hair and fur
Lipid
def
Fat or oils, composed of fatty acids and glycerol
Lock and key hypothesis
def
Model which compares the specificity of enzymes with a key and its lock
Metabolism
def
All the chemical reactions in the cells of an organism, including respiration
Oils
def
Natural substances produced from the reaction of glycerol with fatty acids.
Optimum
def
The best or most appropriate - for instance, the conditions under which an enzyme works best (eg temperature and pH)
PH
def
Scale of acidity or alkalinity. A pH (power of hydrogen) value below 7 is acidic, a pH value above 7 is alkaline
Substrate
def
A substance on which enzymes act
Sucrose
def
A disaccharide made from glucose and fructose. It is used as table sugar
Synthesise
def
To construct a larger biological molecule from smaller ones
Lock and key hypothesis
Enzymes are folded into complex 3D shapes that allow smaller molecules to fit into them. The place where these molecules fit is called the active site.
In the lock and key hypothesis, the shape of the active site matches the shape of its substrate molecules. This makes enzymes highly specific. Each type of enzyme can usually catalyse only one type of reaction (some may catalyse a few types of reactions).
Denaturing enzymes
If enzymes are exposed to extremes of pH or high temperatures the shape of their active site may change.
If this happens then the substrate will no longer fit into the enzymes. This means the key will no longer fit the lock. We say that the enzyme has been denatured.
It is important you use ‘denatured’ and not ‘killed’ as enzymes have never been alive.
The rate of an enzyme-catalysed reaction is calculated by…
+Calculation
measuring the rate at which a substrate is used up or by the rate at which a product is formed.
rate of reaction = (amount of substrate used or amount of product formed) ÷ (time taken)
How does temperature effect the reaction rate of an enzyme-catalysed reaction?
As with many chemical reactions, the rate of an enzyme-catalysed reaction increases as the temperature increases. However, at high temperatures the rate decreases again because the enzyme becomes denatured and can no longer function.
As the temperature increases so does the rate of enzyme activity. An optimum activity is reached at the enzyme’s optimum temperature. A continued increase in temperature results in a sharp decrease in activity as the enzyme’s active site changes shape. It is now denatured.
How does pH effect the reaction rate of an enzyme-catalysed reaction?
Changes in pH also alter the shape of an enzyme’s active site. Each enzyme work bests at a specific pH value. The optimum pH for an enzyme depends on where it normally works. For example, enzymes in the small intestine have an optimum pH of about 7.5, but stomach enzymes have an optimum pH of about 2.
In the graph above, as the pH increases so does the rate of enzyme activity. An optimum activity is reached at the enzyme’s optimum pH, pH 8 in this example. A continued increase in pH results in a sharp decrease in activity as the enzyme’s active site changes shape. It is now denatured.
How does substrate concentration effect the reaction rate of an enzyme-catalysed reaction?
Enzymes will work best if there is plenty of substrate. As the concentration of the substrate increases, so does the rate of enzyme activity. However, the rate of enzyme activity does not increase forever. This is because a point will be reached when the enzymes become saturated and no more substrates can fit at any one time even though there is plenty of substrate available.
As the substrate concentration increases so does the rate of enzyme activity. An optimum rate is reached at the enzyme’s optimum substrate concentration. A continued increase in substrate concentration results in the same activity as there are not enough enzyme molecules available to break down the excess substrate molecules.
Investigating the effect of pH on enzyme
activity
Aim:
To determine the optimum pH at which an enzyme’s activity is greatest.
Method
Risks
Method:
1) Set up a Bunsen burner, heatproof mat, tripod and gauze.
2) Place a beaker of water on the gauze and adjust the flame to keep the water at about 35°C.
3) Now put two drops of iodine solution into each spot of a spotting tile.
4) Add 2 cm3 of amylase enzyme solution to a test tube.
5) Place 2 cm3 of starch solution into the same tube.
6) Finally add 1 cm3 of pH solution to the tube. This will keep the pH constant.
7) Mix the solution in the test tube and place it into the beaker of water on the Bunsen burner.
8) Use a pipette to remove a few drops of solution every 20 seconds from the test tube and put them into a different well of the spotting tile.
9) Repeat until the iodine solution stops turning black.
10) Record the time this takes.
11) Repeat with different pH solutions.
Risks:
-Iodine solution is an irritant. If it touches skin it should be washed off.
-Goggles should be worn at all times.
Enzymes and food
Carbohydrates, proteins and lipids are large molecules that are needed by the body for growth, repair and metabolism. They are found in our food. These molecules are too large to pass from the intestine into the blood, so digestive enzymes break them down into smaller molecules. Once in the body, different enzymes use these raw materials to synthesise larger molecules.
Carbohydrates
Carbohydrates include glycogen, starch, sucrose and glucose.
The basic building block of a carbohydrate is a monosaccharide. This is simple sugar, such as glucose and fructose. Enzymes join monosaccharides together to form disaccharides (two monosaccharides) and polysaccharides (long chains of monosaccharides).
Carbohydrase enzymes break disaccharides and polysaccharides into monosaccharides (simple sugars). Carbohydrase enzymes are produced in your mouth (in saliva), pancreas and small intestine.
Proteins
Proteins are large molecules made from amino acids joined together to form chains. They include enzymes, haemoglobin, collagen and keratin. Each protein has hundreds, or even thousands, of amino acids joined together in a unique sequence and folded into the correct shape. This gives each protein its own individual properties.
Protease enzymes are responsible for breaking down proteins in our food into amino acids. Then different enzymes join amino acids together to form new proteins needed by the body for growth and repair. Protease enzymes are produced in your stomach, pancreas and small intestine.
Lipids
Lipids are fats and oils. Lipids are large molecules made from smaller units of fatty acids and glycerol.
Digestive enzymes such as lipase break down lipids in the diet into fatty acids and glycerol. Lipase enzymes are produced in your pancreas and small intestine.
Calorimetry
A calorimeter is a machine used in the process of calorimetry. Small samples of material are placed in the machine which burns them. The energy given off when the material burns is measured.
Calorimeters are often used in the food industry to measure the energy in food. This value is given in joules or calories in the nutritional information panel on the food packaging.
The simplest calorimeter can be made by arranging a beaker of water above a burning sample. The change in temperature of the water is a direct measure of the energy held within the sample.
