biological molecules Flashcards
Give two named examples of polymers and their associated monomers to
illustrate your answer -5 marks
-hydrolysis = breaking of chemical bonds by H2O e.g break glyosidic bond polysaccharide to monosaccharide
condensation bond - joins 2 monomer, + remove H2O + chemical bond e.g nucleotide to polynucleotides with phosphodiester bondMARKS
what is a polymer
a smaller, repeating unit of which larger molecules are made from
when polymer made of mixture of sugars, add up all carbon, oxygen, hydrogen atoms
- galactose = C6H12O6
- glucose = C6H12O6
- fructose = C6H12O6
Give the number of carbon atoms, hydrogen atoms and oxygen atoms in a
molecule of raffinose.
Number of carbon atoms _____18__________
Number of hydrogen atoms _______36________
Number of oxygen atoms ______12_________
A biochemical test for reducing sugar produces a negative result with
raffinose solution.
Describe a biochemical test to show that raffinose solution contains a
non-reducing sugar. 3 marks
heat - dilute HCL
Add alkalinising agent - sodium bicarbonate - benedict does not work in acid
retest normally - red precipitate
A student carried out the Benedict’s test. Suggest a method, other than
using a colorimeter, that this student could use to measure the quantity of
reducing sugar in a solution. - 2 marks
filter + dry the precipitate
find mass of dry precipitate
student wanted to identify the type of sugar in two beakers.
test 1 - normal benedicts test
test 2 - adds maltase
results
beaker 1 - red, red
beaker 2 - red, dark red - 2 marks
beaker 1 - glucose, same amount of sugar exposed so same result
beaker 2 -Because more sugar/precipitate after hydrolysis/maltase action;
Use of a colorimeter in this investigation would improve the repeatability of
the student’s results.
Give one reason why -1 mark
colour is subjective, valid data not produced
Q 2E MATHS SKILLS
Lactulose is a disaccharide formed from one molecule of galactose and
one molecule of fructose.
Other than both being disaccharides, give one similarity and one difference
between the structures of lactulose and lactose. - 2
similarity - both contain glycosidic bonds / both contain galactose
difference - lactose does not contain fructose whereas lactulose does
Glycogen and cellulose are both carbohydrates.
Describe two differences between the structure of a cellulose molecule
and a glycogen molecule. - 2 marks
difference 1 -cellulose only has 1,4 glycosidic bonds, whereas glycogen has 1,4 and 1,6 bonds
difference 2 - glycogen is coiled, cellulose has straight long chains parallel to each other
beta and alpha glucose
Starch is a carbohydrate often stored in plant cells.
Describe and explain two features of starch that make it a good storage molecule - 2 marks
- insoluble in water- does not affect cells water potential so osmosis does not happen
-branched/ coil = more compact
-branched - ends for enzymes to breakdown
Tick (✔) the box that identifies the test which would be used to show the
presence of starch. 1 mark
iodine
Describe the structure of glycogen. 2 marks
alpha g , branched 1,4 and 1,6 bonds
During early pregnancy, the glycogen in the cells lining the uterus is an
important energy source for the embryo.
Suggest how glycogen acts as a source of energy - 2 marks
- glycogen - storage molecule that has many branches so that enzymes hydrolyse into glucose
- glucose used in reparation
Name the monomers from which a maltose molecule is made. 1 mark
- glucose
Name the type of chemical bond that joins the two monomers to form maltose -1 mark
glycosidic
6c
Explain the difference in the structure of the starch molecule and the
cellulose molecule shown in the diagram above.
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