Enzymes Flashcards
What are enzymes?
Proteins that are folded into complex specific shapes that allow only a specific substrate/molecule to fit into them
Purpose of enzymes?
Biological catalysts that speed up the rate of biochemical reactions. Critical in almost all biochemical reactions that allow organisms to carry out life processes. E.g. DNA replication, mitosis, digestion, photosynthesis, respiration
Active site?
The area where the substrate molecule fits into an enzyme
Reactant substrate?
The molecule that fits into an enzyme
Enzyme-substrate complex?
When the enzyme and substrate bind together temporarily
Anabolic enzyme/reaction?
An enzyme that takes small molecules and joins them together to build larger molecules (e.g. proteins from amino acids)
Catabolic enzyme/reaction?
An enzyme that takes large molecules and breaks them up into different products
Activation energy?
The minimum amount of energy required for a chemical reaction to occur
Enzymes working as biochemical reactions…
Enzymes act as biological catalysts by lowering the activation energy of chemical reactions, by providing an alternative reaction pathway. The lower the activation energy for a reaction, the faster the rate, thus, enzymes speed up reactions
The lock & key model
The model explaining how enzymes work where the enzyme is a rigid & specific structure, allowing only a specific shape to fit into it
The induced fit model
The model showing how the enzyme changes its shape after bonding with the substrate
Particle theory?
All matter is made up of particles that are in constant motion. Temperature affects the speed of the particles
Collision theory?
In order for a chemical reaction to occur, two or more reactant particles must collide with sufficient force(energy) & at the correct orientation.
The minimum amount of energy required for a chemical reaction to occur is called ‘activation energy’
Optimum temperature
Temperature where the rate of enzyme activity is at its highest
Denaturation
Protein denaturation is the breakdown of hydrogen bonds, leading to a change in its structure. Caused by temperature (or incorrect pH)
Factors affecting enzyme activity (temperature)
High temperature, enzymes denature (change its structure due to breakdown of hydrogen bonds) due to high kinetic energy
Low temperature, particles have low kinetic energy making the rate of reaction slow down
Optimum temperature, temperature where enzyme activity is at its highest
Factors affecting enzyme activity (substrate concentration)
Low concentration of substrate means there are plenty of enzymes with active sites available. Rate of reaction is limited by the substrate concentration. High concentration of substrate, inefficient availability of enzyme active sites. The increase of substrate conc. increases the rate of reaction until the saturation point, where anything further makes no difference.
Factors affecting enzyme activity (pH)
pH is a measure of acidity. pH 1-6 acidic, 7 neutral, 8-14 basic. Changes in pH alter enzymes shape, which disrupts the bonding of the substrate. Each enzyme will function within a pH range.
Cofactors/Coenzymes
Substances that many enzymes need to work.
Cofactors (ions)
Coenzymes (organic molecules, from dietary vitamins)
Inhibitors
Poisons that bind to the active site and prevent the substrate from bonding to the enzyme, preventing catalysing reactions
