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Document information Uploaded on September 1, 2024 Number of pages 17 Written in 2024/2025 Type Exam (elaborations) Contains Only questions Subjects as level aqa bio biology paper 2 paper 2 mark scheme 2024 a level 2024 as level aqa biology paper 2 mark £4.86
Document information Uploaded on September 1, 2024 Number of pages 17 Written in 2024/2025 Type Exam (elaborations) Contains Only questions Subjects as level aqa bio biology paper 2 paper 2 mark scheme 2024 a level 2024 as level aqa biology paper 2 mark
Document information
Uploaded on
September 1, 2024
Number of pages
17
Written in
2024/2025
Type
Exam (elaborations)
Contains
Only questions
Subjects
as level
aqa
bio
biology
paper 2
paper 2 mark scheme
2024
a level 2024
as level aqa biology paper 2 mark scheme 2024
as
Writte...
AS LEVEL AQA BIOLOGY PAPER 2 MARK SCHEME 2024
Describe and draw the structure of water.
The water molecule is made up of two atoms of hydrogen covalently bonded to one atom of
oxygen.
How does the structure of water enables it to be a good solvent?
Water is a solvent. The tiny charges on its molecules attract other molecules or ions thats
have charges on them. This is the because of the dipole.
How does water being a solvent and being able to flow play a role in the medium of life?
Cytoplasm contains many different substances dissolved in water. Water can flow and
therefore can carry dissolved substances from one place to another. This happens in our blood
and in the xylem vessels and phloem sieve tubes. Urea is removed from the body by being
dissolved in water as urine.
Draw the structure of beta glucose.
...
Draw the structure of alpha glucose.
...
What are the functions of glucose?
Glucose is used as an energy source, a transport substance and a monomer to make other
organic substances.
How does the structure of glucose enable it to be a good source of energy?
It's carbon atoms are easily oxidized to form carbon dioxide releasing energy in the process.
How does the structure of glucose enable it to be a good transport substance?
The numerous hydroxyl groups in glucose allows it to hydrogen bond with water molecules,
thus making it highly soluble in water.
How does the structure of glucose enable it to be a monomer to make other organic
substances?
The aldehyde group in glucose is very reactive so it will easily polymerize.
Describe the structure of the sucrose molecule and draw it.
A sucrose molecule is made up of an alpha glucose molecule linked to a beta fructose
molecule by a 1-2 glycosidic bond.
What are the functions of sucrose?
Sucrose is used as an energy source, a transporter and a storage material in some plants.
How does the structure of sucrose enables it to be a good energy source?
The enzyme sucrase hydrolyzes sucrose to glucose and fructose since it is unreactive. The
fructose molecule is then rearranged to form glucose.
How does the structure of sucrose enable it to be a good storage molecule and a good
transport substance ?
The aldehyde group and the ketone group are linked together in the glycosidic bond, thus has
no reactive group.
Draw the molecular structure of starch.
...
What is starch made up of and what are the types of bonds?
Starch is a mixture of amylose and amylopectin joined together by an alpha 1-4 glycosidic
bond. Amylopectin has alpha 1-6 branches which spirals to a lesser extent than the
unbranched amylose which coils up into a spiral.
Why is starch insoluble?
Starch is made up of 79% amylopectin. Amylopectin has branched chains and the more
branched chains it has, the more insoluble it is.
How does the structure of starch enable to be a good energy reserve?
, The enzyme amylase can break down starch into glucose molecules and since it coils to form
spirals, it is more compact.
Draw the molecular structure of glycogen.
...
Name the types of bonds in glycogen and the and what it is made up of?
Glycogen is made up of alpha glucose. It is made up of alpha 1-4 glycosidic bonds with alpha
1-6 branches.
Why is that glycogen so dense?
It has more branches than amylopectin so it is heavily branched, so it is less able to form
spirals
How does the structure of glycogen allow it to be a good energy reserve and source and
why is it insoluble?
Because glycogen is so widely branched, it is insoluble and it allows many enzymes to act
simultaneously to cut off more glucose molecules. The chains also coil up into helical
structures, making their final structure more compact (useful for storage).
What color does glycogen and amylopectin give with iodine?
Faint red
Draw the molecular structure of cellulose
...
What is cellulose made up of and what are the bonds?
Cellulose is made up of beta glucose. The molecules are linked with beta 1-4 glycosidic
bonds.
How does the structure of cellulose contribute to it being a very strong structure?
The cellulose molecule lies straight because of it's bonding. This allows hydrogen bonds to be
formed between with hydroxyl groups of neighboring molecules. This produces bundles of
molecules lying side by side called fibrils all held together by thousands of hydrogen bonds
which are collectively strong
How does the structure of cellulose contribute in cells?
Bundles of fibrils are called fibres. Fibers are structurally very strong because of the many
collectively strong hydrogen bonds and giving the molecule high tensile strength. This makes
cell walls able to expand without breaking.
Why is cellulose difficult to digest?
Very few animals have an enzyme that can break its beta 1-4 glycosidic bond.
How does cellulose not being able to digest be of importance in human being?
Its is a good source of dietary fiber in the human beings remaining undigested as it passes
through the alimentary canal and stimulating peristalsis.
What color does amylose give with iodine?
Blue-black
Draw the molecular structure of a triglyceride.
...
What is triglyceride made up of?
Triglyceride is made up of one molecule of glycerol attached to three fatty acids with 3
hydrophobic hydrocarbon tails attached.
Describe triglycerides' role as a source of energy.
When triglycerides are respired they make compact and efferent stores. Triglycerides are
used as thermal insulator.
What is triglycerides role in obesity?
High triglyceride levels contribute to obesity.
Draw the structure of a phospholipid molecule.
...
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