C1.1 (Enzymes and metabolism) Flashcards
(49 cards)
What is the role of enzymes as catalysts?
- biological catalysts
-
speeds up reactions in living cells;
-allows reactions to occur at much lower temperatures than would be possible otherwise - Faster waste removal to prevent accumulation + toxicity
- Faster *response to injury**
What is metabolism? What is the role of enzymes in metabolism?
Metabolism -> complex network of interdependent and interacting chemical reactions occurring in living organisms;
enzyme specificity (where one enzyme catalyzes on reaction);
- many different enzymes are required by living organism;
- control over metabolism can be brought about through these enzymes;
What are anabolic reactions? + 3 ex
when macromolecules are built from monomers by condensation reactions (protein synthesis, photosynthesis, DNA synthesis)
What are catabolic reactions? + 3 ex.
Those that break down larger molecules into smaller ones (Ex. Glycolysis, digestion, citric acid cycle)
What is an active site? ( structure + role)
- Only composed of a few amino acids
- Globular protein structure
- Binds to substrates
-Allows reactions to occur
How do interactions between substrate and active site to allow induced-fit binding?
Both enzyme + substrate changes shape. As the fit is induced, the catalysis can take place, at a lower energy level than normal
What is the role of molecular motion and substrate-active site collisions in enzyme catalysis?
- Substrates need to collide with the enzyme active site with sufficient energy and at the correct orientation;
- Enzymes can be immobilized by being embedded into membranes;
- Sometimes substrates can also be immobilized (such as glycogen)
What is the relationship between the structure of the active site, enzyme-substrate specificity and denaturation?
- precise shape
- Only fits particular substrate
- Highly specific
- Denaturation leads to the shape of the active site no longer fitting the substrate, therefore leading to a loss of activity of enzyme
What are the effects of temperature on the rate of enzyme activity?
- Increased temperature increases the chance of enzyme substrate collisions
- Optimal temperature
- Beyond such temp. Increased molecular motion leads to disruption of intermolecular interactions
- Can denature
What are the effects of pH on the rate of enzyme activity?
Altering pH can alter intermolecular interactions within the protein:
- Between r groups
- Within active site
- Can be Irreversable
What are the effects of substrate concentration on the rate of enzyme activity?
- More substrate = more product
- Rate of reaction increases
- Does plateau at one point
What is activation energy?
-Amount of energy required to allow a particular reaction to occur
- Energy is needed to break bonds
- Enzymes reduce activation energy required
What are intracellular and extracellular enzyme-catalyzed reactions? What is an example of each?
-
Intracellular enzyme reaction takes place in cells
(Such as glycolysis in cytoplasm) -
extracellular enzyme reaction takes place outside
(Such as chemical digestion in gut)
What is generated by all reactions of metabolism?Why is this inevitable?How is this useful?
- Heat is generated
- Metabolic reactions are not 100% energy effective
- Some mammals/ animals depend on heat to produce maintenance of constant body temp.
What are the two major types of pathways in metabolism?
Linear - one product becomes the reactant in the next reaction (ex. Glycolysis)
Cyclical - Final product is again fed back to become react in first step (ex. Krebs + Calvin)
What are allosteric sites?What is non-competitive inhibition of enzymes?
Allosteric sites are binding site(s) away from the active site of an enzyme.
-Non-competitive inhibitors are substances that can bind to allosteric site;
-binding is reversible; causes conformational (shape) changes
What is competitive inhibition? + 1 ex
When a molecule structurally similar to the substrate binds to the active site
ex. statins- compete for active site of enzyme involved in cholesterol synthesis therefore reducing it
How are metabolic pathways regulated by feedback inhibition?Use
isoleucine as an example
- Non competitive inhibitor chnages shape, meaning end product of a pathway can inhibit enzyme needed for first step of metabolic pathway
- This is negative feedback
- Isoleucine is an end product, stopping from it being converted stops production of isoleucine
How is penicillin an example of mechanism-based inhibition?
- Penicillin Binds irreversibly to enzymes in bacteria involved in cell wall synthesis
- Therefore weakens cell wall and burst, killing the bacteria
What is metabolism?
The sum of all chemical reactions taking place in a cell at one time.
What does metabolic pathway being interdependent mean?
They rely on each other to occur. e.g. A+B=C then C+D=E
4 different forms of energy important to organisms:
- Kinetic energy
- Potential energy
- Chemical energy
- Thermal energy
structure of ATP
- Phosphate group + ribose + adenine
Physical attributes of Enzymes
- Globular
- 3D proteins
- Compact molecules
