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Biological Molecules Exam Questions with Correct Answers
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Biological Molecules Exam Questions with Correct Answers
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Biological Molecules Exam Questionswith Correct Answers
using your knowledge of the formation of structural polysaccharides, describe the
formation of the chitin molecule from its monomer and predict its structure - Answer--
formed by condensation
- water released
- alternate monomers are rotated through 180
- because of the position of OH / H on carbon 1
- forms an unbranched polymer
- similar to cellulose
many multicellular organisms need to be able to convert monosaccharides into
polysaccharides and back again
mammals convert the monosaccharide glucose into a highly branched polysaccharide
called glycogen which gets stored in liver cells
explain why mammals store glycogen instead of glucose - Answer-glycogen is:
- insoluble so has no effect on water potential
- metabolically inactive
- compact / lots can be stored in a small space
- able to store large amounts of energy
- highly branched so has lots of ends for adding / removing glucose when needed / can
be broken down fast to release glucose
explain how the students would use the calibration curve to estimate the glucose
concentration of the fruit juices - Answer-- find the absorbance [using a colorimeter]
- find the concentration that corresponds to this absorbance
- follow the absorbance value across to the line of best fit and then down the
concentration
describe how you would carry out a controlled experiment to test this hypothesis without
using a colorimeter - Answer-- taste the fruit juices to see how sweet they are
- place a sample of each fruit juice in a biosensor AND take a reading
- obtain rank order for fruit juice glucose concentration
- compare rank orders for sweetness and glucose concentration
- how a variable was controlled glucose concentration test
suggest one reason why the results for this experiment might not support the student
hypothesis - Answer-- tasting is subjective / qualitative / hard to quantify sweetness /
people may have different judgement
- colour judgement in benedicts is subjective
- may contain sucrose / other (named) sugar
, state 2 ways in which the molecular structure of cholesterol is similar to the molecular
structure of glucose - Answer-- both contain C AND H atoms
- contain O atoms
- have OH groups
state the physical property of glucose that allows it to be easily transported in the
bloodstream - Answer-- glucose is soluble in water
another disaccharide is maltose. maltose and lactose both contain the same number of
atoms of each element C, H and O
state 2 other structural similarities between lactose and maltose - Answer-- 2 membered
rings / hexoses
- 1,4 glycosidic bonds
- 2 CH2OH groups
- rings contain 1 O atom
lactose is a reducing sugar
benedict's reagent can be used to detect the presence of lactose in a solution
a colorimeter can be used to measure the concentration of lactose
the colorimeter first needs to be calibrated
describe how a method that uses benedict's reagent and a colorimeter could be
calibrated to measure the concentration of lactose in an unknown sample - Answer-- 0
the colorimeter/ set to 0
- using blank
- use red filter
- use known concentrations of lactose
- produce serial / series dilutions
- construct calibration curve
- test unknown sample
- read from calibration curve to determine unknown concentration
give 3 properties of cellulose that make it suitable as the basis of plant cell walls -
Answer-- insoluble
- unreactive / inert
- high tensile strength
- flexible
- can form hydrogen bonds with neighbouring chains
state 2 similarities and 2 differences between the structures of chitin and glycogen -
Answer-similarities:
- polymers / polysaccharides
- have 6 carbons in the sugar
- have 1,4 glycosidic bonds
- have CH2OH side group in monomers
differences:
- chitin has beta glycosidic bonds
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