Enzymes and How They Work (2.1.3)

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What are enzymes?
They are tertiary level globular proteins.
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What is a biological catalyst?
Something which speeds up cellular reactions but remains unchanged- can be used again & again.
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What is the shape of an enzyme?
Specific 3D shape with hydrophobic R-groups towards the middle and hydrophilic R-groups around the outside, making them soluble.
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What does it mean that enzymes are specific?
Each enzyme catalyses just one type of reaction involving one particular substrate. The active site of the enzyme has a complementary shape to just one type of substrate.
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What is an intracellular enzyme?
Works inside cells. Eg: respiratory enzymes needed for cell respiration.
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What is an extracellular enzyme?
Secreted from cells to work elsewhere. Eg: enzymes secreted from cells lining the digestive system onto food as it passes through.
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What is the active site?
The specifically shaped region of an enzyme, to which other molecules can join. Often, fewer than 10 amino acids make up the active site.
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What bonds are there in an enzyme?
Disulphide bonds, ionic bonds, hydrogen bonds.
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What is activation energy?
The initial energy that has to be put in to get a reaction started.
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What problem do enzymes solve?
Activation energy could be provided by increasing temperature, but we can't raise our body temperature much over 37 degrees C. Enzymes allow substrates to be held so they can react more easily with out the need for high temperatures.
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What is an anabolic reaction?
Reactions that join molecules together. Eg: joining glucose to make glycogen.
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What is a catabolic reaction?
'Break down' reactions. Eg: respiration breaks down glucose.
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How do enzymes and substrates join together?
They collide with each other randomly due to their kinetic energy and this allows ES (enzyme-substrate) complexes to form.
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What is the lock and key hypothesis?
The substrate fits into the enzyme active site in the same way that a key fits into a lock- a perfect fit where the substrate is held in place for the reaction to go ahead.
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What is the induced fit hypothesis?
Substrate molecule collides with enzyme active site. Enzyme changes shape slightly-allows active site to fit closely around substrate. Charges on E&S are complementary as well as shapes- attraction. Enzyme joins to substrate- ES complex forms.
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What happens when the product is formed from an enzyme-catalysed reaction?
When product is formed, it's a different shape from original substrate and no longer fits active site. Product moves away, enzyme active site is free to join with further substrate molecules.
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Why does the rate of reaction slow down from the initial rate when an enzyme and substrate are added together?
Initially, lots of substrate molecules available, so most enzyme molecules can join with one to make product. Over time, number of substrate molecules decreases as they're converted to product- fewer ES complexes a second. Less product made a second.
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Card 2

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What is a biological catalyst?

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Something which speeds up cellular reactions but remains unchanged- can be used again & again.

Card 3

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What is the shape of an enzyme?

Back

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Card 4

Front

What does it mean that enzymes are specific?

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Card 5

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What is an intracellular enzyme?

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