Term
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Definition
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Term
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Definition
| Globular proteins with a specific tertiary structure held by hydrogen bonds, ionic bonds, disulphide bridges. They act as biological catalysts that speed up the rate of metabolic reactions by lowering the activation energy. |
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| What is activation energy? |
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Definition
| Energy required for a reaction to begin. |
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Term
| What are intracellular enzymes? |
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Definition
They work inside our cells
-in solution
-membrane bound
e.g. lysosomes, DNA replication |
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Term
| What are extracellular enzymes? |
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Definition
They work outside our cells
-secreted
e.g. Amylase, protease |
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Term
| What are the two ways in which enzymes can catalyse metabolic reactions? |
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Definition
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Term
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Definition
| Forms a product e.g. Photosynthesis |
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| What does catabolic mean? |
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Definition
| Breaks a bond e.g. Respiration |
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Term
| What does active site mean? |
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Definition
| Has a specific shape, only complementary to the substrate which binds to form an ESC, one enzyme that binds to specific amino acids will not be able to bind to others. |
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Term
| What is the lock and key model? |
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Definition
-The substrate fits into the active site, they are complementary shapes this forms an ESC
-The product is then formed and as it doesn't fit into the active site, the products are released.
-Enzymes are very specific |
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Term
| What is the induced fit model? |
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Definition
-Substrate and active of the enzyme are not complementary
-When substrate binds, the active site changes shape and fits itself around the substrate
-Places a strain on the substrate and distorts a particular bond, lowering the activation energy required to break the bond
-The products are formed and leave the active site which then returns to its original shape. |
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Term
| What does the enzyme lysozyme do? |
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Definition
Helps kill bacteria by catalysing the hydrolysis of sugars in the peptidoglycan cell walls.
Cell wall is weakened and when the bacteria absorbs water by osmosis the walls burst |
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Term
| Where can lysozymes be found? |
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Definition
| Tears, saliva, human milk, and inside the lysosomes |
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Term
| What are enzymes properties? |
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Definition
-Specific-Complementary shape of the active site. This depends on the sequence of amino acids that make up the active site
-Fast acting- very high turnover number, can convert many molecules of substrate per unit time
-Soluble- with hydrophilic R grp found on the outside of the molecules |
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Term
| What factors affect the rate of enzymes? |
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Definition
-Temperatures
-pH
-Substrate Conc.
-Enzyme Conc.
-Inhibitors |
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Term
| How does pH effect the rate of enzyme activity? |
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Definition
Optimum pH-rate of reaction is at its maximum
-Enzymes only work within a narrow range of pH values
-Small deviations cause reversible changes in enzyme structure resulting in inactivation
-Extremes of pH can permanently denature an enzyme |
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Definition
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Term
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Definition
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Term
| What can cause an extreme change in pH? |
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Definition
May alter the electrostatic charge on the side chains of the amino acids.
If both the active site and substrate have the same charge they will repel. |
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Term
| What can buffers be used for? |
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Definition
| Added to enzyme-controlled reactions to maintain a constant pH. |
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Term
| What happens to the rate of reaction as substrate conc. increases? |
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Definition
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Term
| What happens to the substrate when conc. of it is low? |
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Definition
| Substrate conc. is the limiting factor |
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Term
| When does enzyme conc. becomes the limiting factor? |
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Definition
| As more substrate is added, there are more successful collisions and more enzymes sites become occupied, until eventually the rate of reaction reaches a maximum substrate of molecules are in excess. |
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Term
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Definition
| It prevents the enzymes to form ESC. |
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Term
| What is a competitive inhibitor? |
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Definition
It is like blocking, they are similar in shape to a substrate, complementary to the active site and bind to it, blocking the actual substrate from entering, so fewer esc can form.
If substrate conc. increases the inhibitor's effect is reduced |
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Term
| What is an example of competitive inhibitor? |
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Definition
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Term
| How does malonic acid work? |
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Definition
| A reaction is involved in aerobic respiration is catalysed by the enzyme succinic dehydrogenase. The competitive inhibitor malonic acid has a similar shape to the substrate succinic acid. |
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Term
| What is a non-competitive inhibitor? |
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Definition
Changes the shape of the active site
It is not similar shape to the substrate. It binds to the enzyme at a point other than the active site known as the allosteric site.
This changes the shape of the enzyme and therefore the active site so it is not complementary to the substrate. The enzyme molecule may be permanently altered. |
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Term
| What is an example of non-competitive inhibitor? |
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Definition
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Term
| Which inhibitor has the lowest rate of reaction? |
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Definition
No inhibitor-highest
Competitive - the effect of it can be reduced
Non-competitive - lowest |
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Term
| What are immobilised enzymes? |
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Definition
| Fixed, trapped or bound on an inert matrix |
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Term
| Examples of how enzymes are immobilised. (4) |
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Definition
-Adsorption onto a matrix
-Covalent binding to a support
-Trapping within a fibrous matrix
-Encapsulation behind a selectively permeable membrane |
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Term
| Why enzymes on a surface have a higher rate of reaction than those immobilised in beads? |
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Definition
In beads- have a lower r.r. because some active sites are inside and substrate will take time to diffuse into them
-On surface the active sites are more available- high r.r. |
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Term
| Advantages of immobilised enzymes ? (6) |
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Definition
-Enzymes are easily recovered for re-use
-Product is not contaminated with the enzyme
-Enzymes with different pH can be used together
-Increased stability over a range of temp.
-Enzymes can easily added or removed giving greater control over the r.r.
-Increased stability over a range of pH values |
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Term
Fill in the gaps
denature
wider
stabilises |
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Definition
| Trapping an enzyme __________ it and prevents the shape change that would ________ its active site, so it can be used under _____ range of conditions. |
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Term
| How can immobilized enzymes be used for lactose-free milk? |
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Definition
| It can be produced using lactase trapped in alginate beads in a column, which hydrolyses the lactose to its monosaccharides |
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Term
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Definition
Covert chemical signals into electrical.
Detect and measure low conc. of substrate in a mixture. |
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Term
| How are biosensors used for measurements of glucose conc.? |
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Definition
Glucose oxidase is immobilised on a selectively permeable membrane.
When in sample, it binds to glucose and small electric current is produced. Current is detected by an electrode and conc. of glucose can be read on the screen |
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Term
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Definition
| A sweetener manufactured in a multi-step process from starch. It involves several immobilised enzymes which require different conditions. |
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