B4 - Enzymes Flashcards
What are enzymes?
Biological catalysts that speed up chemical reactions but are not changed or used up in the process
- long chains of amino acids that fold up to have different shapes that allow specific binding of substrates
- they are protein molecules
Metabolic pathways
Sequences of enzymatically catalysed chemical reactions in a cell
- since every chemical reaction within a cell is controlled by an enzyme: a group of these reactions makes a metabolic pathway
Catabolic pathways
Complex molecules are broken down to simpler ones and energy is released
- e.g. digestion
Anabolic pathways
Build up large chemicals and compounds which requires energy
- e.g. making glycogen in your liver
Lock and Key Theory
Theory of enzyme catalysis stating that the active site’s structure is complementary to the structure of the substrate
Active site
A region on an enzyme that binds to a protein or other substance during a reaction
- complementary in shape to the substrate it binds to forming an enzyme-substrate complex
Substrate
A specific reactant acted upon by an enzyme
Factors affecting enzyme activity (4)
- Temperature
- pH
- Enzyme concentration
- Substrate concentration
Enzyme Concentration on Enzyme Activity
- Increasing the concentration of enzymes increases the rate of reaction
- Enzymes are more likely to collide with substrates and therefore more E-S complexes form
- If the concentration of substrate is limited then eventually there will be no further effect
Substrate Concentration on Enzyme Activity
- Increasing the concentration of substrate increases the rate of reaction (True up to a saturation point)
- Collisions are more likely so more E-S complexes form
- The concentration will decrease over time therefore the rate of reaction will also decrease
- therefore, the initial rate is the highest
What are optimum conditions?
Conditions in which the enzyme works best in
Optimum temperature for enzymes
37˚C body temp
What are reactions without enzymes like?
The reactions would need a lot more energy to take place
- chemical reactions need something to decrease their duration and increase their quality
Temperature on enzyme activity
- Increasing the temperature increases the rate of reaction
- The increase in kinetic energy means they can move faster and are more likely to collide and form E-S complexes
- Increasing the temperature above the optimum can break bonds which results in the active site changing
- The substrate no longer fits as the enzyme is denatured and doesn’t function as a catalyst
Complementary shape of an enzyme
The shape of the active site of an enzyme which is corresponding to the shape of the substrate
Denatured enzyme
An enzyme which no longer functions because its shape and active site has been changed and the substrate can no longer fit
pH on enzyme activity
- All enzymes have an optimum pH value.
- Higher or lower than this the enzyme will denature and the active site changes shape
- At this point the enzyme is no longer functional.
Optimum pH for enzymes
Differs from enzymes, the only optimum condition enzymes in animal bodies share is optimum temperature
Pepsin
Enzyme that breaks down proteins in the stomach
Amylase
Enzyme in saliva that breaks the chemical bonds in starches
Trysin
An enzyme in pancreatic juice that breaks down protein molecules
Optimum pH for amylase, trysin and pepsin
- amylase: approx. 7 pH
- trypsin: 8-8.5 pH
- pepsin: 1.9 pH
Range of activity for amylase
approx. 4-10
Range of activity for trypsin
approx. 5.8-10
Range of activity for pepsin
0-3.5
