Biological Molecules Flashcards
(23 cards)
name three examples of monomers found in carbohydrates
glucose, fructose, galactose
what is maltose made of
alpha glucose + alpha glucose
What types of molecules are reducing sugars?
All monosaccharides and some disaccharides
how does cellulose differ from starch
cellulose: beta glucose, bonds form above and below, hydrogen bonding between straight chains which are branched. Starch: made from alpha glucose, arranged in a helix shape, unbranched
test for starch
add iodine solution: starch = orange to blue/black
how does alpha glucose differ from beta glucose (structure
the H and OH groups on c1 are switched (OH on bottom for alpha glucose)
test for presence of reducing sugars
benedicts solution + heat = red solution
test for non reducing sugars:
add HCl (hydrolyses bonds) + HEAT + sodium hydrogen carbonate (neutralizes acid) and then carry out regular test with benedicts solution.
How do the features of cellulose relate to it’s function?
Straight chains of Beta glucose form many hydrogen bonds between them forming microfibrils which provide collective strength for its role as structural support for plant cells.
Cellulose is also insoluble.
Describe the structure of a triglyceride and explain how it forms.
Three fatty acids joined to a glycerol molecule by condensation reactions to form ester bonds.
What’s the difference between a saturated, monounsaturated and polyunsaturated fatty acids?
Saturated fatty acids contain only single bonds between carbons
monounsaturated fatty acids contain one double bond between two of the carbons in the chain
polyunsaturated fatty acids contain more than one double bond between carbons in the chain
What are the important properties of triglycerides?
They contain lots of energy making it good for storage
Insoluble so they don’t affect water potential
How could you test for the presence of lipids?
Shake the sample with ethanol, add to water. A milky emulsion indicates that lipids are present.
How does a dipeptide form?
A peptide bond forms directly between the N of the amine group of one amino acid and the C of the carboxyl group of another amino acid, with the loss of H from the amine group and OH from the carboxyl group to form water in a condensation reaction.
What is meant by the term ‘secondary structure’?
Formation of hydrogen bonds between amine and carboxyl groups of amino acids within the polypeptide chain to form either alpha helix or beta pleated sheet.
What is meant by the term ‘tertiary structure’?
Folding of the polypeptide chain by the formation of hydrogen bonds, ionic bonds and disulphide bridges between R groups of amino acids to give the chain a 3D shape.
What is meant by the term ‘quaternary structure’?
Some proteins consist of more than one polypeptide and some are associated with non-protein prosthetic groups to make them functional.
How could you test for the presence of proteins?
Biuret test – add sodium hydroxide followed by copper II sulphate solution. The presence of protein will cause a colour change from blue to purple.
Describe the induced fit model
The active site changes shape and moulds around the substrate to become complementary as they bind. changing shape of the active site holds them close together, reducing any repulsion between them.
Why is the rate of an enzyme catalysed reaction slower when the pH is lower than the optimum?
The presence of H+ ions when the pH is low disrupts some of the ionic and hydrogen bonds in the enzymes active site causing it to change shape and denature.
How do competitive inhibitors reduce enzyme activity?
Competitive inhibitors bind to the active site of an enzyme, preventing the substrate from binding.
How can the effect of competitive inhibitors be reduced?
Increasing the concentration of substrate increases the chance of substrate binding to active sites.
How do non-competitive inhibitors reduce enzyme activity?
Non-competitive inhibitors bind to a region on the enzyme other than the active site. This disrupts the tertiary structure causing the enzyme and therefore the active site to change shape.
