2.4 Enzymes Flashcards
How would you speed up a chemical reaction in a laboratory setting and why isn’t this possible in the human body?
-Increase pressure
-Increase temperature because thermal energy gives particles kinetic energy to collide
-Enzymes would denature and cause death
What are enzymes and what is a turnover number?
-Biological catalysts that speed up chemical reactions in living organisms, they are globular proteins
-They help sustain life by speeding up chemical reactions needed to sustain life that would happen too slowly
-The turnover number is the number of reactions an enzyme can catalyse per second
What is an anabolic and catabolic reaction?
-Anabolic: builds up and synthesise large polymers
-Catabolic: break down large organic molecules
Draw the energy graphs for an anabolic and a catabolic reaction?
Where does enzyme action occur?
-Both intracellularly and extracellularly
What do the enzymes Protease, Carbohydrase, Lipase and Cellulase catalyse?
-Protease: Proteins-peptides
-Carbohydrase: monosacharides- carbohydrates
-Lipase: Lipids- glycerol and fatty acids
-Cellulase- Cellulose- β glucose
What is catalase?
-Intracellular enzyme
-Protects cell by speeding up the reactions that breaks down hydrogen peroxide into water and oxygen
-Highest turnover number
What is a metabolic pathway?
-A series of consecutive chemical reactions with each step being catalysed by a different specific enzyme.
-If one enzyme can’t function the pathway can’t run
-Can be both catabolic and anabolic e.g photosynthesis
What is the equation for an enzyme controlled reaction?
-Enzyme + substrate -> Enzyme-substrate complex -> Enzyme-Product complex -> Enzyme + Product
How do enzymes increase rate of reaction?
-Enzymes lower the activation energy by creating an enzyme-substrate complex so the two substrates are held close to bond in an anabolic reaction or it puts strain on the complex in a catabolic reaction so it breaks down.
How are enzymes highly specific and how will temperature and PH affect it?
-The tertiary structure of the active site is complementary to the shape of the substrate which makes the enzymes function specific
-Changes in temperature and PH will affect its ability to function because the bonds holding the tertiary structure will be affected
What is the lock and key hypothesis?
-The hypothesis states that the substrate molecule fits into the active site like a key into a lock
-Various bonds hold it to form an enzyme-substrate complex
-A substrate molecule is split into two or two or more are joined together as strain is put on bonds to break them or the substrates are brought closer together to join
-The enzyme-product complex forms for a second and the products then leave the site
What is the induced fit hypothesis?
-this proposes that the active site initially isn’t an exact fit for the substrate molecule
-As the substrate moves into the enzyme it distorts the enzyme and its active site so that it tightly envelopes the substrate
What is a cofactor and the two types?
-A small protein that attaches to a molecule so that it can work
-Two types: activators (permanently bound to the enzyme so therefore a prosthetic group) and Coenzymes (large molecules that temporarily bind to the enzyme transferring a chemical group that is necessary e.g. ATP
Why is the initial rate of reaction the fastest?
-The chance of collision is at the highest because there is plenty of substrate and enzymes free
What is temperature coefficient?
-The change in rate of reaction for every 10 degrees Celsius rise.
Temperature coefficient= rate of reaction +10 degrees/rate of reaction
What happens when you change the temperature of an enzyme-controlled reaction?
-Initially increasing the temperature will increase rate as more enzyme-substrate complexes form as both the enzyme and substrate will have more kinetic energy
-When the temperature is too high however bonds that hold the tertiary structure break so the active site changes and the substrate won’t fit so the rate will decrease
-Way too much heat will cause irreversible change in the shape of the active site and the enzyme will become denatured
How does changes in PH affect enzymes?
-Hydrogen+ ions interfere with the hydrogen bonds that hold the tertiary structure together, when too acidic and when too alkaline OH- ions also affect hydrogen bonds and change the shape of the active site and the rate will decrease
-If normal PH is restored hydrogen bonds will be restored but at high levels of acidity and alkaline the active site can be permanently changed
What is a buffer?
-Something that resists change to PH e.g. Blood keeps PH at 7.4
What are two limiting factors of enzyme controlled reactions and Vmax
-Enzyme and substrate concentration
-Vmax is the maximum value the rate of reaction will increase up to if more substrate is added it will have a negligible effect as all active sites are used up
What are enzyme inhibitors?
-Inhibitors are molecules that prevent enzymes from carrying out their function or slow them down
-Two types: competitive and non-competitive
How do competitive inhibitors work?
-They have a similar shape to the substrate and compete with the substrate to bind
-They form an enzyme inhibitor complex physically preventing entry of the substrate
-However they bind to the active site with weak bonds so can be removed.
How do non-competitive inhibitors work?
-They bind to the allosteric site causing a conformational change in the active site so the substrate can’t bind
What determines wether the inhibitor is reversible or non-reversible
-Both competitive and non-competitive inhibitors can be reversible and non-reversible
-It depends on the strength of the bonds hydrogen bonds or ionic bonds are weak so can break easily but if the inhibitor forms covalent bonds it cannot be removed
Draw and explain a graph to show the effect of a competitive and a non-competitive inhibitor?
What is inside poisons?
-Poison contains inhibitors which irreversibly block enzymes like enzymes important for neuromuscular synapses causing paralysis and death
