Biological Molecules Flashcards
What is each disaccharide made up of?
Maltose = glucose and glucose
Sucrose = fructose and glucose
Lactose = galactose and glucose
How are the polysaccharides glycogen, starch and cellulose adapted?
• Insoluble - do not interfere with the water potential/osmosis effect
• They are compact - easily stored
• Glycogen is highly branched - so it can be readily hydrolysed into glucose
How to test for a reducing sugar
Add Benedict’s solution
Heat/boil the sample using a water bath
A brick red precipitate = positive result
The test for a non-reducing sugar
Add dilute hydrochloric acid
Neutralise using sodium hydrogen carbonate
Carry out Benedict’s test as normal
Brick red precipitate = positive result
2 comparisons of cellulose and starch
Cellulose has only 1,4 glycosidic bonds whereas starch has 1,4 and 1,6 glycosidic bonds
Cellulose is made from beta glucose whereas starch is made from alpha
How is beta glucose organised?
Long straight chains
Linked together by many hydrogen bonds
To form fibrils
Provides strength
Test for lipids
Emulsion test
Add alcohol
Then add water
Shake
Turns milky/white emulsion
Protein structure - primary, secondary, tertiary and quaternary
1° Specific sequence of amino acids
2° form an alpha helix (structural) or a beta pleated sheet (globular)
3° forms hydrogen bonds, ionic bonds and disulphide bridges, 3D structure
4° Functional protein, contains more than one polypeptide
Biuret test
Biuret reagent
Detects peptide bonds
From blue to lilac
What are enzymes
They increase the rate of reaction by decreasing the activation energy
Their shape is determined by the specific sequence of amino acids (primary)
Explain the induced fit model of enzymes
Shape of enzyme changes slightly to allow the substrate to bind to it
Enables the enzyme-substrate complex to form (ESC)
Puts strains on substrate bonds, lowering the activation energy
How has the model of enzyme action changed
Was - Lock and Key Model - A rigid shape of active site complementary to the substrate
Now - Induced Fit Model - enzyme shape changes slightly in order to bind to the substrate and create the ‘enzyme substrate complex’
