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Unit Test
SBI4U
Biochemistry
NAME:
/17 K
/17 I
/10 C
/10 A
/54
PART A: Multiple Choice (10 marks)
Circle the best possible answer for the following questions
1.
Glucose and galactose are considered:
a. Acidic
b. Structural isomers
c. Geometric isomers
d. Optical isomers (enantiomers)
2.
A triglyceride is a form of ___________ composed of ________________.
a. Lipid; fatty acid and glucose
b. Lipid; cholesterol
c. Carbohydrate; fatty acids
d. Lipid; fatty acids and glycerol
3.
Which of the following is not one of the most abundant elements found in living organisms?
a. C
b. N
c. H
d. O
e. Cl
4.
What is the monomer of a polysaccharide?
a. Sucrose
b. Starch
c. Monosaccharide
d. Disaccharide
5.
Which of the following is not primarily composed of protein?
a. Hair
b. Urine
c.
d.
Nails
Enzymes
6.
An example of an anabolic reaction would be:
a. Photosynthesis.
b. Digesting your lunch.
c. Breaking down glucose to form ATP
d. None of the above are examples of anabolic reactions.
7.
In a car’s muffler, platinum catalyses the reaction that converts carbon monoxide, CO, and oxygen gas, O2, into carbon dioxide, CO2.
Based on this reaction, which of the following is the substrate?
a. Platinum.
b. Carbon monoxide.
c. Oxygen gas.
d. Carbon dioxide.
e. Carbon monoxide and oxygen gas.
8.
The production of the amino acid isoleucine from threonine has five steps. Once isoleucine is created, it binds to the enzyme that catalyzes
the first step, threonine deaminase and prevents the reaction from continuing. This is an example of:
a. Competitive inhibition.
b. Feedback inhibition.
c. Non-competitive inhibition.
d. An allosteric site.
9.
Sickle cell anemia is a disease characterized by a single substitution of glutamine for valine in the polypeptide. Which of the following would be
a correct prediction? [A]
a. The primary structure would be changed.
b. The tertiary structure would be changed.
c. The biological activity of this protein might be altered.
d. All of the above are expected.
10. Which of the following is NOT TRUE of both starch and glycogen?
a. They are both polymers of glucose.
b. Glycogen is found in animals while starch is found in plants.
c. The glucose of glycogen is not digestible, but the glucose in starch is.
d. They are both used for energy storage.
PART B: Fill-in-the Blanks (15 marks)
Answer the following questions in the spaces provided.
1. Complete the following chemical reactions and identify the type of reaction shown. [K-6]
a)
glycine + _A.a or a specific one_________  __H2O__ + dipeptide
b)
HCl + NaOH  __NaCl_ + ___H2O_
c)
___triglyceride (.5 for lipid)_ + H2O  1 glycerol + 3 _fatty acids_
Reaction Type: __dehydration synthesis or condensation
Reaction Type: ___neutralization__
Reaction Type: _hydrolysis_
2. Answer the following questions based on the set of molecules provided on the next page. [I-8]
a)
What is the name of the chemical bond shown by the arrow in molecule J? ___phosphodiester bond_or covalent__
b) Which amino acid would be involved in disulphide bridge formation? State molecule letter. __ C
c)
What is the name of the linkage seen in molecule D? ___ ester ____
d)
Which two molecules represent structural isomers of each other? State molecule letters _G_ & _I_
e)
Which amino acid has a hydrophobic R group? State molecule letter. _F_
f)
What is the name of the linkage seen in molecule K? ___glycosidic___
g)
What is the name of the linkage seen in A? ____peptide____
h)
What is the name of the 3-carbon molecule that results when molecule D goes through hydrolysis? __glycerol__
PART C: Short Answer (30 marks)
Answer the following questions in the spaces provided. Use point form if possible.
1.
Demonstrate the synthesis of sucrose. Be sure to
label all reactants and products. Three simple
sugars are available at right for your reference. [C-3]

Glucose + fructose
3. Suppose that you received a stack of biological sketches of different molecules. You were told that each molecule belongs to one of the
following categories: carbohydrates, proteins, nucleic acids, and lipids. How would you sort out the sketches? Explain the clues you would use
to distinguish between the groups. [I-4]
 For carbohydrates look at chemical formula in 1:2:1 C:H:O or long chain of repeating 6 carbon rings, joined by glycosidic linkages
 For proteins look for peptide bond between monomer units
 For lipids – look for glycerol and 2-3 long carbohydrates chains bound by a ester linkage to the glycerol
 For nucleic acids – look for repeating nucleotides joined together by a phosphodiester bond.
Or



Separate the sketches that had only carbon, hydrogen and oxygen – these will be the lipids and carbohydrates
Then check which sketches had phosphate groups – these will be the nucleic acids and the remaining sketches with nitrogen as my
proteins **both have nitrogen but only nucleic acids have repeating phosphate groups.
I would then look at my lipids/carbohydrates and determine the carbon,hydrogen,oxygen ratios – if they are 1:2:1 they are carbs.
4. A biologist heats a beaker containing a clear, colourless aqueous solution of an unknown biological substance. After a few hours, the solution
begins to thicken. The biologist knows that either a hydrolysis or condensation reaction took place. Based on the observations available, which
type of reaction might have occurred, and why? [I-2]

Because the solution is thickening – it is loosing water or using water to make bonds. This indicates that a hydrolysis reaction is
occurring. A condensation reaction would produce more water.
5. a) Egg albumin or egg white, as it is commonly called, is the cytoplasm of an unfertilized egg. Until an egg is fertilized, it is a single cell! Egg
albumin is a globular protein with four levels of structure. Without going into detail about the specific amino acids that make up egg albumin,
describe, in detail, four levels of structure you would expect egg albumin to have. Be sure to include as much detail as possible (specific
intermolecular and intramolecular interactions) and include any appropriate terminology. You may want to use diagrams to help explain. [C-4]




Primary – long polypeptide chain of repeating amino acids
Secondary – hydrogen bonding interaction between amino acids in the polypeptide to form alpha helixes and beta pleated
sheets depending on the a.a. sequence
Tertiary – interactions between the R groups of the a.a. – hydrophilic and hydrophopic interactions, hydrogen bonding and
disulphide bridges to form a more complex folded structure – this is where the enzyme forms it globular shape
Quaternary – more than one polypeptide in tertiary structure joins through dipole interactions to form a official protein. This
is when the enzyme will get it functionability
b) Explain what occurs at the molecular level when a raw egg is cooked into scrambled eggs. Explain your answer. [A-2]
-enzymes denature when heating
-intermolecular bonds are broken, enzyme looses its 3D shape and creates new bonds – hardening of the egg.
6. a) Compare the structure of glycogen with that of cellulose. [K-2]


b)
both glycogen and cellulose are made of repeating units of glucose however, glycogen is made of repeating alpha glucose
joined by glycosidic linkages and has many branches of these chains.
Cellulose is made of beta glucose monomers and as a result every other glucose is flipped upside down. The chain is also
straight, with no branches.
If humans had the ability to digest cellulose, what would a high-fibre diet do to blood glucose levels? [A-2]

Because cellulose is made up of glucose molecules if we were able to break its glycosidic linkages, it would cause our blood sugar
levels to rise drastically in our blood which could cause major organ/body issues.
7. Using your knowledge of the structure of lipids, explain why oil in salad dressing will rise to the top of a water-based mixture of vinegar and
herbs. Feel free to draw a diagram to visualize. [A-2]



Lipids have a polar head and long non-polar hydrophobic tails. These tails are repelled by water while the head
are attracted to water. The tails are much larger and as a result the repulsive properties are greater than the
attractive ones and the oil will form a layer with the polar heads touching the water and tails pointing upward.
It rises to the top because they are less dense
Diagram should show the polar heads touching the water layer with the fatty acid tails pointing upward.
8. a) Draw an enzyme-substrate complex and label all key features of the structure. [C-3]
Substrate (.5)
Active Site (1)
Enzyme (.5)
Allosteric Site (1)
(b) Describe a hypothetical situation that would involve competitive inhibition of that enzyme. Be sure to include an explanation of how this
inhibition occurs and why it is occurring. Use your key terminology from the course. [I-3]
o
Competitive inhibition occurs when another substance, that has more affinity (attractive) power to the active site binds to the
enzyme before the substrate can. This substance then prevents the enzyme from acting on the substrate and essentially
stops its use for the time being. This can occur naturally – when the body sends competitive inhibitors to stop production
or breaking down of substrates when they are not longer needed or can occur when snake venom or another chemical
is ingested into the body, this is more likely to be irreversible.
9. The diagram below shows a key enzyme of photosynthesis involved in producing glucose called Rubisco. As a first step in this process,
Rubisco binds to a molecule RuBP like a lock and key via intermolecular attractions. A mutation has occurred in Rubisco whereby lysine
(abbreviated as lys in the diagram) is substituted with aspartic acid.
Predict how this mutation impacts the rate of photosynthesis, and explain your
prediction. [A-3]
Rubisco = enzyme
RuBP = substrate
Aspartic acid = like a competitive inhibitor
Aspartic acid is able to (through mutation) block Rubisco from
binding to its normal active site (RuBP). If Rubisco can not
bind to the active site it cannot perform work. Rubisco cannot catalyze the photosynthetic reaction.
Therefore, this mutation will act to decrease the rate of photosynthesis.