biological molecules

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The term 'carbohydrate' means hydrated carbon. Explain the link between the term and the general formula for a monosaccharide
ratio of hydrogen atoms to oxygen atoms is always 2:1
1 of 9
Why are molecules of glucose and fructose described as structural isomers?
same molecular formula but different structural formula
2 of 9
Describe a test that identifies the presence of non-reducing sugars
does not give a + results in simple Benedict's test; then add dilute hydrochloric acid to sample solution; add sodium hydrogen carbonate until solution stops fizzing. (neutralisation) ; then add Benedict's reagent and heat. result is +
3 of 9
Distinguish between condensation reactions and hydrolysis
condensations: form chemical bonds between monomers; water molecule produced. Hydrolysis: water breaks bonds between monomers
4 of 9
Sucrose is a non-reducing sugar, Explain why is gives a positive result when heated with Benedict's reagent, following acid hydrolysis
acid hydrolysis of sucrose releases the monomers a-glucose and B-fructose; the monomers are reducing sugars that give a + result when heated with Benedict's reagent
5 of 9
How do structures of a-glucose and B-glucose molecules differ?
a-glucose : -OH group on C1 below the plane of the ring. B-glucose: -OH group on C1 above the plane of the ring
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Why do plant cells not burst when large hydrostatic pressures develop inside them as a result of osmosis?
wall of plant cells made up of cellulose which have high tensile strength; contains content of cell (cell does not burst) when hydrostatic pressure within cell increases (because of osmosis)
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Why do starch and glycogen have little effect on the osmotic properties of cells?
both molecules virtually insoluble; therefore do not add to solute conc, in cells; therefore water potential not affected. osmotic movement of water into cell unchanged
8 of 9
For a fixed concentration of a substrate, explain why the rate of an enzyme-catalysed reaction first increases with the addition of enzyme but is then limited with the addition of even more enzyme
addition of enzymes increase no. of active sites of enzyme available to bind with substrate; ror increases; when all substrate molecules bound to active sites, further addition of enzyme doesn't increase ror-no substrate molecules to bind with AS
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Other cards in this set

Card 2

Front

Why are molecules of glucose and fructose described as structural isomers?

Back

same molecular formula but different structural formula

Card 3

Front

Describe a test that identifies the presence of non-reducing sugars

Back

Preview of the front of card 3

Card 4

Front

Distinguish between condensation reactions and hydrolysis

Back

Preview of the front of card 4

Card 5

Front

Sucrose is a non-reducing sugar, Explain why is gives a positive result when heated with Benedict's reagent, following acid hydrolysis

Back

Preview of the front of card 5
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