Enzymes Flashcards
What is an enzyme?
A protein molecule that acts as a biological catalyst by lowering activation energy
what type of protein is an enzyme and how does it help?
globular protein so hydrophillic amino acids on outside and hydrophobic on inside - makes it soluble in water
anabolic reaction
builds up molecuels
catabolic reactions
break down molecules
metabolism
combination of anabolic and catabolic reactions - all different reactions happening in a cell
metabolic pathway
sequence of enzyme controlled reactions
extracellular
enzymes that catalyse reactions outside of cells eg. breaking down nutrient molecules for digestion
intracellular
enzymes that catalyse reactions inside cells eg. synthesising polymers from monomers like making polysaccharides
example of intracellular enzymes and what it breaks down
- catalase - hydrogen peroxide to water and oxygen
examples of extracellular enzymes and what they break down
- Amylase (produced by salivary glands and pancreas) - starch into maltose
- Trypsin (produced by pancreas) - protein into peptides
structure of an enzyme’s active site
amino acids interact with each other to maintain a specific tertiary structure - means it has a specific active site to catalyse specific reactions
induced-fit hypothesis
- the tertiary structure of the active site is flexible and changes shape slightly as the substrate enters
- the bonds formed between substrate and enzyme help catalyse the reaction, lowering activation energy
- when the product leaves the enzyme the active site returns to its inactive state
- other substrate molecules cannot form the correct bonds with the active site so the tertiary structure doesn’t change shape
lock and key hypothesis
- a specific substrate binds to the active site of a specific enzyme by interacting with R groups of the active site forming enzyme-substrate complex
- substrate reacts and products formed in an enzyme-product complex
- product released
what can the quaternary structure of an enzyme mean?
- they can have more than one active site
- eg. catalase has 4 identical polypeptide chains and therefore 4 active sites
activation energy
amount of energy that must be applied for the reaction to proceed
how do enzymes affect activation energy?
they lower it
Digestion of starch
- starch polymers broken down into maltose by amylase (produced by salivary glands and pancreas)
- Maltose broken down into glucose by maltase (produced by small intestine)
- glucose is then small enough to be absorbed by cells lining the digestive system
Digestion of proteins and where is enzyme produced?
- Trypsin is a protease that catalyses digestion of proteins into smaller peptides
- then broken down further into amino acids by other proteases and absorbed by cells lining the digestive system
- Trypsin - produced in pancreas and released into small intestine
Effect of low temp on enzyme activity
low rate of reaction
- low kinetic energy so move slowly
- few successful collisions between enzyme and substrate
effect of optimum temp on enzyme activity
high rate of reaction
- lots of kinetic energy so move quickly
- lots of successful collisions between enzyme and substrate
Effect of very high temp on enzyme activity
low rate of reaction
- heat causes loads of kinetic energy and enzymes vibrate very fast - breaks the hydrogen bonds maintaining tertiary structure of enzyme
- active site changes and substrate doesn’t fit
- enzyme denatures
- no successful collisions