UNIT 5 Flashcards
What is an enzyme?
A protein that acts as a biological catalyst. They lower the activation energy without being used up in a reaction and remain unchanged.
What structure of protein are enzymes?
They are tertiary- proteins where the polypeptide chain is folded into a globular shape, held by peptide, hydrogen, disulphide and ionic bonds.
What are the two ways enzymes can function?
Intracellularly (lysosomes) or extracellularly (amylase).
What are anabolic reactions?
These involve the building up of large complex molecules from small molecules.
What are catabolic reactions?
These involve the breaking down of large molecules into small molecules.
What is lock and key theory?
The active site which is specific to the enzyme is an exact match to its substrate, with only a single substrate being a precise match for the enzyme.
What is induced fit theory?
The substrate molecule changes the shape of the active site and the active site changes to fit the substrate perfectly. This means that several different substrates can react with the same enzyme.
What are the factors affecting the rate of enzyme activity?
Temperature, pH, enzyme and substrate concentration.
How does temperature affect the rate of enzyme activity?
As temperature increases, rate of reaction increases as molecules gain more kinetic energy, which results in more successful collisions. As temperature increases beyond the optimum, rate of reaction decreases due to the active site denaturing, resulting in fewer successful collisions.
How does pH affect the rate of enzyme activity?
As pH decreases away from the optimum and becomes more acidic, H+ disrupt bonds and decreases rate of reaction. As pH increases away from the optimum and becomes more alkaline, OH- disrupt bonds and decreases rate of reaction.
How does increasing substrate concentration affect the rate of enzyme activity?
Increasing substrate concentration increases rate as more collisions can occur so more product can be formed. Further increasing the concentration does not affect the rate as all active sites are occupied at a fixed enzyme concentration.
How does increasing enzyme concentration affect the rate of enzyme activity?
Increasing enzyme concentration increases rate as more active sites become available so more product forms. This relationship only occurs when the substrate is in excess.
What is an inhibitor?
Any substance or molecule that slows down the rate of an enzyme controlled reaction by affecting the enzyme molecule in some way.
What is a competitive inhibitor?
Binds to the active site of the enzyme as it is a similar shape and prevents enzyme-substrate complexes forming, so no product. It is generally reversible and decreases the rate of reaction.
What is a non-competitive inhibitor?
Binds to the allosteric site of the enzyme and changes the shape of the active site to stop enzyme-substrate complexes forming. It is permanent denaturation and decreases the rate of reaction.
What are immobilised enzymes?
Enzymes that are fixed to an inert support such as alginate beads or a cellulose membrane.
What are the advantages of immobilised enzymes?
The enzyme does not contaminate the product
Greater control over the process
Enzymes can be recovered and reused
Only a small quantity of enzymes needed
How do buffers work?
They are capable of either binding to or releasing H+ ions depending on the H+ concentration within a solution.
What are the layers of the gut wall?
Serosa- a layer of connective tissue
Muscularis- contains inner circular and longitudinal muscles for peristalsis
Sub-mucosa- contains a rich supply of blood vessels and nerves
Mucosa- innermost later. Epithelium is folded to maximise surface area. Secretes mucus to lubricate and protect against autolysis
Lumen
How to convert mm to nm?
mm x1000 -> μm x1000 -> nm
What is the null hypothesis in a Chi² test?
There is no significant difference between the observed and expected values, and any differences are due to chance alone.
How to calculate degrees of freedom?
Number of data sets minus one.
What conclusion do you draw if the Chi² value is lower than the critical value?
The null hypothesis is accepted as there is no significant difference between the observed and expected results, and any differences are due to chance alone.
What conclusion do you draw if the Chi² value is greater than the critical value?
The null hypothesis is rejected as there is a significant difference between observed and expected results, and there must be another explanation for the data.
Why do we carry out repeat readings?
To reduce uncertainties in raw data measurements, allowing a mean to be calculated which is more reliable than individual results, increasing confidence in results.
What do short range bars indicate?
Consistency of the raw data and reliability of the mean.
What are the adaptions of the villus for absorption?
Folded epithelium with microvilli to maximise surface area
Presence of lacteals for transport of fats
Dense capillary network to maintain a concentration gradient
Epithelial lining one cell thick for a short diffusion pathway.
