Topic 1b - Biological Molecules and Transport in Cells Flashcards
What is an enzyme?
proteins that act as biological catalysts to speed up the rate of a chemical reaction without being changed or used up in the reaction
What do enzymes do?
- reduce the need for high temperatures
- speed up the useful chemical reactions in the body
- help speed up process of breaking down substances
What do the enzymes produced by living things act as?
Biological catalysts
What is the rule for enzymes and catalysing reactions?
- The active site can only catalyse one reaction at a time.
- Once all the active sites are full, increasing the amount of substrates has no effect on the rate, as there are no available enzymes to catalyse further reactions.
- Increasing the substrate concentration has no effect, so the rate will depend on the number of enzymes around
What is a catalyst?
a substance which increases the speed of a reaction, without being changed or used up in the reaction
What is a substrate?
the substance the enzyme acts on
What is the active site lock and key theory?
When the enzyme is in the optimum temperature, it doesn’t let a chemical reaction occur, with a substrate.
When the enzyme isn’t at optimum temperature, the substrate binds with the enzyme, and then a chemical reaction takes place. After the chemical reaction occurs, products are released.
What is the rate of reaction and temperature graph trend?
Increasing the temperature, increases the rate of reaction because the reactions have more energy, so they move about more, and collide with each other more often
What does the enzyme rate of reaction and temperature graph show?
- Changing the temperature, changed the rate of an enzyme-catalysed reaction.
- A higher temperature increases the rate at first, but if it 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 anymore (it is denatured).
- Enzymes in the human body usually work best around 37 degrees celsius.
At what temperature to human enzymes denature?
around 45 degrees celsius
What does the substrate concentration graph show?
- The higher the substrate concentration, the faster the reaction, because it is more likely that the enzyme will meet up with a substrate molecule.
- There is a steady increase in rate as more substrate molecules are available.
- After that, there are so many substrate molecules that the enzymes have as much as they need, as all the active sites are full, and adding more makes no difference, so the rate remains constant.
What is respiration?
the process of breaking down glucose, which transfers energy
What does a high pH mean?
it’s alkaline
What does a low pH mean?
it’s acidic
What happens if the pH is too low or too high?
the pH interferes with the bonds holding the enzyme together, which changes the shape of the active site and denatures the enzyme
At what pH does pepsin work best at?
pH 2
What is the optimum pH for enzymes?
pH 7
How do you investigate the effect of pH on amylase?
1) Put a drop of iodine solution into every well of a spotting tile.
2) Place a Bunsen burner on a heat-proof mat, and a tripod and gauze over the Bunsen burner. Put a beaker of water on top of the tripod and heat the water until it reaches the optimum temperature of the amylase you are using. (Use a thermometer to measure the temperature.) Try to keep the temperature of the water constant throughout the experiment.
3) Use a syringe to add 3 cm^3 of amylase solution and 1 cm^3 of a buffer solution with a pH of 5 to a boiling tube. Using test tube holders, put the boiling tube into the beaker of water and wait for five minutes.
4) Next, use a different syringe to add 3 cm3 of a starch solution to the boiling tube.
5) Immediately mix the contents of the boiling tube and start a stop clock. 6. Use continuous sampling to record how long it takes for the amylase to break down all of the starch. To do this, use a dropping pipette to take a fresh sample from the boiling tube every thirty seconds and put a drop into a well on the spotting tile. When the iodine solution remains browny-orange, starch is no longer present.
7) Repeat the whole experiment with buffer solutions of different pH values to see how pH affects the time taken for the starch to be broken down.
8) Remember to control any variables each time you repeat the experiment to make it a fair test. Variables that need controlling include the concentration and volume of the amylase and starch solutions and the temperature of the reaction mixture.
What is the rate of reaction used to measure?
how much something changes over time
How do you calculate the rate of reaction?
rate = 1000 ÷ time taken
What is a biological molecule?
molecules found in living organisms
What are some examples of biological molecules?
- Carbohydrates
- Lipids
- Proteins
What do enzymes catalyse?
breakdown reactions
What are some examples of enzymes catalysing break down reactions?
- Many of the molecules in the food we eat are too big to pass through the walls of our digestive system, so digestive enzymes break them down into smaller, soluble molecules. These can pass easily through the walls of the digestive system, allowing them to be absorbed into the bloodstream. They can then pass into cells to be used by the body.
- Plants store energy in the form of starch (a carbohydrate). When plants need energy, enzymes break down the starch into smaller molecules (sugars). These can then be respired to transfer energy to be used by the cells
What does enzyme amylase break down starch to?
maltose
How do you investigate the effect of pH on amylase?
1) Put a drop of iodine solution into every well of a spotting tile.
2) Place a Bunsen burner on a heat-proof mat, and a tripod and gauze over the Bunsen burner. Put a beaker of water on top of the tripod and heat the water until it reaches the optimum temperature of the amylase you are using. (Use a thermometer to measure the temperature.) Try to keep the temperature of the water constant throughout the experiment.
3) Use a syringe to add 3 cm3 of amylase solution and 1 cm3 of a buffer solution with a pH of 5 to a boiling tube. Using test tube holders, put the boiling tube into the beaker of water and wait for five minutes.
4) Next, use a different syringe to add 3 cm3 of a starch solution to the boiling tube.
5) Immediately mix the contents of the boiling tube and start a stop clock. 6. Use continuous sampling to record how long it takes for the amylase to break down all of the starch. To do this, use a dropping pipette to take a fresh sample from the boiling tube every thirty seconds and put a drop into a well on the spotting tile. When the iodine solution remains browny-orange, starch is no longer present.
7) Repeat the whole experiment with buffer solutions of different pH values to see how pH affects the time taken for the starch to be broken down.
8) Remember to control any variables each time you repeat the experiment to make it a fair test. Variables that need controlling include the concentration and volume of the amylase and starch solutions and the temperature of the reaction mixture. See p.10 for more on fair tests.
How do you calculate the rate of reaction?
rate = 1000 ÷ time taken
What is the unit for the rate of reaction?
s^-1
What is the rate used to measure?
how much something changes of time
What is a biological molecule?
a molecule found in living organisms
What are some examples of biological molecules?
- Carbohydrates
- Proteins
- Lipids
What do enzymes catalyse?
breakdown reactions