7913816
Description
Flashcards by Tania Parvaiz, updated more than 1 year ago
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Created by Tania Parvaiz
about 7 years ago
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| Question | Answer |
| How do you test for protein? | 1. Add a few drops of biuret solution to the test tube. 2. Blue -> purple/lilac (contains protein) |
| How do you test for starch? | 1. Add a few drops of iodine dissolved in potassium iodide to test tube 2. Yellow/brown -> blue/black (starch present) |
| How do you test for lipids? | 1. Add 2cm cubed of ethanol and shake 2. Pour the liquid into a test tube of water (2cm cubed) 3. Clear liquid -> cloudy white emulsion (lipid present) |
| How do you test for reducing sugar? | 1. Add a few drops of benedict's reagent. 2. Place test tube in a water bath and heat for approx. 3 mins. 3. Blue -> red (lots present) Blue -> green (not much present) |
| How do you test for non-reducing sugar? | 1. Take new sample in new test tube. 2. Add 1cm cubed HCl and heat for 3min 3. Add sodium hydrogencarbonate in small amounts (upto 1 spatula) 4. Add benedicts and reheat 5. Blue -> red (lots present) Blue -> green (not much present) |
| What is an enzyme made of and what can you say about its structure? | Made of amino acids and it has a tertiary structure (Active site) |
| Is the active site of an enzyme and the substrate the same shape? | No - they are complimentary |
| 2 main theories which describe how enzymes act? | •Lock and key theory •Induced fit theory |
| After an enzyme-substrate complex is formed, what happens to the enzyme and substrate? | •Enzyme = can go react with other molecules to form more complexes •Substrate = converted into product |
| What is the lock and key theory? | Only one specific shape of an enzyme will match the substrate as they are complimentary |
| What is the induced fit theory? | Substrate and enzyme don't have to be complimentary initially - can have minor differences. Active site changes shape to mould itself around the substrate to form an enzyme-substrate complex |
| What 4 things affect the rate of enzyme reaction? | •Temperature •pH •Concentration of substrate OR enzyme •Inhibitors |
| How does an increasing temperature affect the rate of reaction of enzymes? | •Rate of reaction increases as the temperature increases upto optimum temperature •Temperature increase gives substrate molecules more kinetic energy which means they move faster, resulting in a higher collision rate •This means more enzyme-substrate complexes are formed per second |
| How does optimum temperature affect the rate of reaction for enzymes? | At the optimum temperature, the rate of reaction is at its highest with the quickest rate of enzyme-substrate complexes being formed |
| How does a temperature above optimum temperature affect the rate of reaction for enzymes? | •Very high temps break the hydrogen bonds holding the tertiary structure •This causes the enzyme to denature and so enzyme-substrate complexes can no longer form as the active site has changed shape |
| How does a low pH affect the rate of reaction of enzymes? | Some enzymes will denature at a very low pH (acidic) |
| How does optimum pH affect the rate of reaction of enzymes? | At an optimum pH the enzyme is working at the maximum rate of reaction with the max rate of enzyme-substrate complexes being formed |
| What is the pH of a solution a measure of? | Hydrogen ion concentration |
| How do you calculate the pH of a solution? | |
| How does enzyme concentration affect enzyme activity? | |
| Why does increasing the substrate concentration increase the rate of reaction? | Increasing the concentration means more collisions are possible so enzyme-substrate complexes are produced at a rapid rate |
| What would happen to the rate of reaction if the substrate concentration was increased after the maximum rate of reaction had been achieved? | Would stay the same because all the active sites of every enzyme are already occupied and so no more enzyme-substrate complexes can form at a greater rate |
| How could the rate of reaction be increased beyond the maximum rate of reaction? | Increase enzyme concentration |
| What is an inhibitor and what are the 2 types? | •A substance that slows down or stops enzyme action •Competitive and non-competitive |
| Describe the task of competitive inhibitors? (3) | •Have a similar shape to substrate •Bind to active site's specific tertiary structure •Substrate is prevented from binding to the enzymes active site •Therefore less or no enzyme substrate complexes are formed |
| Describe the task of non-competitive inhibitors? (3) | •Have a different shape to substrate •Bind to enzyme away from active site which changes tertiary shape of enzyme's active site •Means substrate cannot bind and so prevents enzyme-substrate complexes being formed |
| How do inhibitors affect the rate of enzyme reaction? | |
| How do you measure the rate of change at any point on a graph? | Measure the gradient of the chosen point by drawing a tangent and calculating the gradient by doing y/x |
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