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Edexcel A-Level Biology B 2024 Exam Questions with Correct Solutions
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Edexcel A-Level Biology B 2024 Exam Questions with Correct Solutions
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Edexcel A-Level Biology B 2024 ExamQuestions with Correct Solutions
Topic 1 - Answer>>Biological Molecules
Name the type of chemical reaction that joins monosaccharides
together to form an amylose molecule. - Answer>>condensation
reaction
Describe the meaning of the term hydrolysis. - Answer>>breaks
bonds via the addition of water
Describe one structural difference between amylose and
glycogen. - Answer>>Glycogen is highly branched with both 1,4
and 1,6 bonds whereas amylose is a straight chain with only 1,4
bonds.
Name the chemical bond that is formed between the
monosaccharides in an amylose molecule. -
Answer>>glycosidic bond
Explain 2 ways in which the structures of amylose and glucose
make them suitable for energy storage. - Answer>>-contain
glucose
-insoluble so don't affect osmosis
-compact so a large no. glucose molecules can be stored in a
small volume
-large molecule so too big to diffuse
Fungi produce different enzymes that can digest starch or
cellulose. Using your knowledge of the structure of starch and
cellulose, suggest why it is necessary for fungi to produce
different enzymes to digest these two substances. - Answer>>-
,different molecule shapes hence different enzymes needed /
different active site shapes
-starch is alpha glucose / cellulose is beta glucose
-only starch contains 1,6 glycosidic bonds
-starch is made of amylose and amylopectin
-cellulose is linear / starch is branched and helical
Describe the structure of starch. - Answer>>-made of alpha
glucose
-glycosidic bonds
-amylose and amylopectin
-amylose has 1,4 bonds and amylopectin has both 1,4 and 1,6
bonds
-amylose is coiled
-amylopectin is branched
-it's a compact molecule
Describe the structure of cellulose in cell walls. - Answer>>-
polysaccharide of beta glucose
-glucose molecules joined by 1-4 glycosidic bonds
-every other glucose molecule is inverted
-cellulose molecules arranged as microfibrils
-joined by hydrogen bonds
Describe the structure of haemoglobin. - Answer>>-four
polypeptide chain
-each chain attached to a haem group
Describe the meaning of the term catalyst. - Answer>>-speeds
up rate of reaction
-without being used up
-lowers activation energy / provides an alternative reaction
pathway
-does not change position of equilibrium
, Explain why increasing temperature above 45 degrees celsius
causes a decrease in enzyme activity. - Answer>>-increased
temperature alters enzyme bonding
-active site denatures
-substrate no longer fits and enzyme no longer catalyses reaction
Describe how the initial rate of reaction could be obtained from a
graph. - Answer>>-draw a tangent to the curve within the first 5-
10 seconds along the x-axis
-read off the change in x and y values
-calculate gradient
Explain why it is only when fruits are cut open that they are likely
to turn brown. - Answer>>-substrates and enzymes are
contained in cells hence have limited oxygen
-enzyme reaction only takes place when cells are broken hence
enzyme, substrate and oxygen can mix
Suggest how 2 amino acids in a sequence can be brought closer
together. - Answer>>-chain can form a secondary/tertiary
structure
-bonding between R groups e.g. hydrogen, ionic and disulphide
Explain why amylopectin is broken down at a quicker rate than
amylose by amylase. - Answer>>-amylase's active site is more
complementary to amylopectin
-amylopectin is highly branched
-amylopectin has many more terminal glycosidic bonds
Explain why a mutation may lead to a change in the activity of an
enzyme. - Answer>>-different amino acid sequence
-different R groups
-different hydrogen/ionic/disulphide bonding
-active site and enzyme activity changes
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