Chapter 4- 4.2- Factors effecting enzyme activity Flashcards
By increasing the temperature of reaction environment what does this also increase?
The kinetic energy of the particles. As temperature increases the particles move faster and collide more frequently. in an enzyme controlled reaction and increase in temperature will result in more frequent successful collisions between substrate and enzyme.this leads to an increase in the rate of reaction.
what is meant by the term temperature coefficient, Q10?
It is the measure of how much the rate of reaction increases with a 10°C rise in temperature.
For enzyme controlled reaction is this is usually taken us 2,which means that the rate of reaction doubles with a 10°C temperature increase.
Explain what happens when an enzyme denatures from temperature?
Because enzymes are proteins the structure is affected by temperature.
At higher temperatures the bonds holding the protein together vibrate more.
As the temperature increases the vibrations increase until the bonds strain and then break.
The breaking of these bonds results in a change in the precise tertiary structure of the protein.
The enzyme has changed shape and is said to have been denatured.
What happens when an enzyme is denatured?
The active site changes shape and is no longer complimentary to the substrate.
The substrate can no longer fit into the active site on the enzyme will no longer function as a catalyst.
What is meant by the term optimum temperature?
The optimum temperature is the temperature at which the enzyme has the highest rate of activity.
The ups and temperature of enzymes can vary significantly.
Many enzymes in the human body have a twin temperature is around 40°C meanwhile thermophilic bacteria found in hot Springs have enzymes with optimum temperatures of 70°C and psychrophilic organisms that live in areas that are cold such as the Antarctic and Arctic regions have enzymes with optimum temperature is below 5°C.
Explain why once the enzyme has denatured above the optimum temperature why the decrease in rate of reaction is so rapid?
It is so rapid because there only needs to be a slight change in shape of the active site for it to no longer be complimentary to the substrate.
This happens to all of the enzyme molecules at about the same temperature so the loss of activity is relatively abrupt.
At this point in an enzyme controlled reactionThe temperature coefficient does not apply any more as the enzymes have denatured.
Why is the decrease in the rate of reaction below the optimum temperature less rapid?
Because the enzymes have not denatured they are just less active
What are three examples of extremely cold environments and how are the enzymes controlling the metabolic activities of organisms living in these environments adapted to the cold?
Deep oceans,high altitude and polar regions.
Enzymes adapted to the cold tend to have more flexible structures particularly at the active site making them less stable than enzymes work at higher temperaturesand smaller temperature changes will denature them.
What is the name for organisms adapted to living in very hot environments and what are two examples of these hot environments?
Thermophiles
Hot springs and deep sea hydrothermal vents.
The enzymes present in these organisms are more stable than other enzymes due to the increased number of bonds particularly hydrogen bonds and sulphur bridges in the tertiary structure.
The shapes of these enzymes, and the active sites, are more resistant to change as the temperature rises.
When are enzymes more likely to come into contact with the substrate?
When temperature and substrate concentration are increased
Why does pH affect enzymes?
Hydrogen bonds and ionic bonds between amino acid R-groups hold proteins in the precise three-dimensional shape. These bonds result from interactions between the polar and charged R-groups present on the amino acids forming the primary structure. A change in pH refers to a change in hydrogen ion concentration. More hydrogen ions are present in low pH (acid) environments and fewer hydrogen ions are present in high pH (alkaline) environments.
What is renaturation ?
The active site will only be in the right shape at a certain hydrogen ion concentration. This is the optimum pH for any particular enzyme. When the pH changes from the Optimum becoming more acidic or alkaline the structure of the enzyme and therefore the active site is altered. However if the pH returns to the optimum in the protein Will resume its normal shape and catalyse the reaction again. This is called the naturation
What happens when the pH changes more significantly (beyond a certain pH) ?
The structure of the enzyme is irreversibly altered and the active site will no longer be complementary to the substrate. The enzyme is now said to be denatured and substrates can no longer bind to the active sites. This will reduce the rate of reaction.
Hydrogen ions interact with polar and charged R-groups. Changing the concentration of hydrogen ions therefore changes the degree of this interaction. The interaction of R-group with hydrogen ions also affects the interaction of R- groups with each other.
The more hydrogen ions present (low pH) the less the R-groups are able to interact with each other. This leads to bonds breaking and the shape of the enzyme changing. The reverse is true when fewer hydrogen ions (high pH) are present. This means the shape of an enzyme will change as the pH changes and therefore it will only function within a narrow pH range.
What are the pH conditions under which the various enzymes of the human digestive system function including saliva, gastric juice and pancreatic juice?
Saliva - in the mouth and throat the pH is neutral (7-8). The enzyme is amylase and it’s function is to turn starch into maltose.
Gastric juice- in the stomach the pH is acidic (1-2). The enzyme is pepsin and its function is to turn proteins into polypeptides.
Pancreatic juice- in the small intestine/ duodenum the pH is slightly alkaline (8). The enzyme trypsin turns protein into polypeptides. The enzyme lipase turns triglycerides into glycerol and fatty acids. Amylase turns starch into maltose. Maltase turns maltose into glucose.
When the concentration of substrate is increased what does this mean?
The number of substrate molecules, atoms, ions in a particular area or volume increases.
