Enzymes Flashcards
(24 cards)
What are enzymes?
They are globular proteins that are catalysts
Why are enzymes advantageous?
4
- They speed up reactions (by lower the activation energy of reactions)
- They are not used up
- They are not changed
- They catalyse many reactions per second
How do extracellular enzymes work?
The enzymes are secreted from cells through exocytosis and to catalyse extracellular reactions.
Give one main example of extracellular in mammals?
The secretion of amylase in the salvary glands.
Give one main example of extracellular in Bacteria/Saprotrophic fungi?
They secrete amylase,lipases and proteases onto their food.
How does intracellular enzymes (in solution) work?
Intracellular enzymes act in solution, inside cells
Give and example of intracellular (in solution) in mammals?
Enzymes that catalyse glucose in glycolysis
Give and example of intracellular (in solution) in plants?
enzymes in solution in the stroma of the chloroplasts catalyse the synthesis of glucose
How does intracellular enzymes (membrane-bound) work?
intracellular enzymes (membrane-bound) may be attached to membranes.
Give the main example of intracellular enzymes (membrane-bound)?
On the cristae of mitochondria and the grana of chloroplasts, where they transfer electrons and hydrogen ions in ATP formation
What is the complex known as when a substrate binds to an active site?
An enzyme-substrate complex
what happens after a enzyme-substrate complex occurs?
Products are release, leaving the enzyme unchanged with the active site ready to receive another substrate molecule
What is activation energy?
The minimum amount of energy required for molecules to react, breaking existing bonds and making new ones
What can temperature, P.H do to enzymes?
They can change the three dimensional structure of the enzyme and can break and alter the configuration of active sites
What positive effect does temperature do to enzymes?
Increases kinetic energy of enzymes and substrates resulting in more successful collisions thus increasing the rate of reaction
What negative effect can temperature (if too high) do to enzymes?
(2)
- The vibrations breaks hydrogen bonds also changing the tertiary structure
- Can denature the enzyme so the substrate wont fit
What negative effect can temperature (if too low) do to enzymes?
The enzyme will be inactive as there is very low kinetic energy.
What happens to enzymes if the P.H is extreme?
In can denature the enzyme
What happens to enzymes if the P.H is small?
it can cause (reversible) changes in the enzyme structure and reduce activity
How are amino acid side chains on enzymes active sites affected by hydrogen and hydroxyl ions?
- At low PH, excess H+ ions are attracted to negative charges and neutralises them
- At high PH, excess OH- ions are attracted to positive charges and neutralises them.
What bonds are affected by hydrogen and hydroxyl ions?
They disrupt the ionic and hydrogen bonds maintaining the the shape of the active site
What effect occurs if the substrate concentration is at a constant?
The rate of reaction increases as the substrate concentration increases.
What effect occurs if the substrate concentration is low?
The enzyme molecules have only a few substrate molecules to collide with so don’t work to their full capacity
What effect occurs if the substrate concentration is high?
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