CP Biology
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KEY
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HOMEWORK PACKET
UNIT 2B:
Basic Biochemistry
Part 2– Proteins, Enzymes, pH
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CP Biology
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Enzymes & pH HW#1
1. What is a chemical reaction?
When one set of chemicals (molecules or compounds) changes into a different set of chemicals, making or
breaking bonds.
2. Complete the table about chemicals in a chemical reaction.
Chemicals in a Chemical Reaction
Chemicals
Definition
Reactants
Elements or compounds that enter into a reaction (ingredients)
Products
Elements or compounds that are a result of the reaction.
THINK VISUALLY
3. The graphs below show the amount of energy present during two chemical reactions. One of the reactions is an
energy-absorbing reaction, the other is an energy-releasing reaction.
 Draw an arrow on each graph to show the energy of activation.
REACTION "A"
REACTION "B"
Activation Energy
Activation Energy
4. Which of the above reactions would be considered an energy-absorbing (endergonic) reaction? Why?
Reaction “A” is endergonic – the products have more energy (larger, more complex, less stable)
than the reactants.
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5. Define "activation energy".
The amount of energy needed to begin or get a reaction started.
6. Which reaction - A or B (from the graphs in Question #3) - has a higher activation energy? (circle one)
7. Regardless of whether an organism makes its own high-energy nutrients or must obtain them by
eating, all organisms must perform the following reaction to release energy for the cell(s):
a. photosynthesis
b. cellular respiration
c. fermentation
8. Which example below illustrates a "reversible" reaction?
a.
b.
9. When chemical bonds are broken, energy is __?__; when new bonds are formed, energy is
__?__.
a. released; released
c. required; required
b. released; required
d. required; released
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CP Biology
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Enzymes & pH HW#2
Proteins are some of the largest and most complex compounds found in living organisms. Although
70% of your body is made of water, most of the other 30% is protein. A cell's DNA or genetic code determines
what types of proteins are made by that cell. As a result, proteins play a large role in determining the structure
and function of a cell.
1. Fill in the missing words in the paragraph below.
The words listed below may be used once, more than once, or not at all:
function
R groups
peptide bonds
homeostasis
number
types
sequence
proteins
amino acids
organic
speed
identity
fold
DNA
polypeptide
catalysts
Proteins are one of the four major types of _organic_______ compounds that we studied in our biochemistry
unit.
__amino acids_______ are the monomers of proteins.
When two or more of these monomers
covalently bond together it forms a polymer called a __polypeptide______. The covalent bonds which join
amino acids are specifically called _peptide bonds_____. When they are first formed (according to the
_DNA____ code of a cell), proteins are linear (straight, unfolded) chains of amino acids. Attractive forces
(such as hydrogen bonds) between the _R groups____ of the amino acids in the chain cause the chain to
_fold_________ up on itself into a 3-dimensional globular shape that is unique to each type of protein.
Remember, form leads to _function____! Once properly folded, polypeptides become functional and are
properly called _proteins___________. Proteins differ in the _number________, _____types_______, and
_sequence___________ of the amino acids they contain. A specific group of proteins is called enzymes,
which help to __speed_________ up chemical reactions in cells. Enzymes are biological _catalysts____
which are critical for the maintenance of __homeostasisin cells.
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2. What do we commonly call the organic catalysts found in cells? enzymes
3. Why is a catalyst highly effective in small amounts?
Enzymes can be reused
And, enzymes are not changed during normal rxns (not a reactant nor a product)
4. Enzymes typically have “-ase” at the end of their name like “sucrase”. Look at the picture. Describe what
sucrase does to sucrose.
Sucrase will stress the bonds in
sucrose and will help form new bonds in
the products (glucose & fructose)
5. How does heat act as a catalyst? Why can't
cells rely on heat as their main catalyst for chemical reactions?
Increase in heat, will increase the speed
of atoms and molecules – thus allowing them to interact at a higher rate.
High temperatures can cause enzymes to denature – thus they lose their ability to function.
6. How does the addition of a catalyst affect the energy of activation of a chemical reaction?
It lowers the amount of energy needed to begin the reaction (aka – activation energy).
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7. Using the analogy of a lock and key, explain what the expression “enzymes
are specific” means.
Enzymes are specific to one type of chemical reaction.
TRUE OR FALSE - if false, correct the statement.
__T___8. Enzymes are reusable.
_F____9. Substrates Enzymes strain the bonds of enzyme substrates molecules, reducing the amount of
energy needed for old bonds to break and new bonds to form.
___F__10. Enzyme-assisted reactions occur much more slowly faster than they would if the enzyme were
not present.
__F___11. A particular enzyme can catalyze many different a single specific types of reactions.
_T____12. Some enzymes assist with hydrolysis, whereas others assist with dehydration synthesis.
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CP Biology
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Enzymes and pH HW #3
_____1. Which of the following is a factor which can affect enzyme activity?
a. availability (concentration) of enzyme and/or substrate molecules
b. temperature
c. pH
d. regulatory molecules
e. all of these
_____2. Denaturation of an enzyme will usually change its structure, leading to:
a. increased rates of reaction
b. decreased rates of reaction
_____3. Which term or phrase is most related to the term "denaturation"?
a. unfolding
b. refolding
c. breaking apart
d. putting together
_____4. Enzymes tend not to work well at very low temperatures due to:
a. rapid movement of molecules and frequent collisions between substrate & enzyme
b. slow movement of molecules and infrequent collisions between substrate & enzyme
c. denaturation of enzyme molecules
_____5. Enzymes tend not to work well at very high temperatures due to:
a. rapid movement of molecules and frequent collisions between substrate & enzyme
b. slow movement of molecules and infrequent collisions between substrate & enzyme
c. denaturation of enzyme molecules
_____6. True or False: An enzyme typically works well throughout a wide range of varying temperature and
pH conditions.
7. Define homeostasis.
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Maintaining a stable internal environment.
8. Based upon your knowledge of enzyme action & denaturation, explain why excessively high temperatures
(such as heat stroke or very high fevers) can be dangerous to the human body.
Excessively high temperatures can cause enzymes to denature (unfold). Without their specific
structure/shape the enzymes cannot perform their function. Without the use of enzymes organisms
cannot maintain homeostasis.
9. What is the name for the region of an enzyme molecule which that binds with a substrate and is most
directly affected by denaturation?
a. inactive site
b. reaction site
c. active site
d. reactive site
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CP Biology
Name_________________________Date____________ Period________
Enzymes and pH HW#4 - Enzymes Review
______1.
Which statement about enzymes is NOT correct?
a. enzymes are polypeptides composed of amino acids
b. an enzyme molecule forms a temporary association with a reactant
c. enzymes are destroyed when they are used and must be synthesized for each reaction
d. enzymes are specific because of their shape and catalyze only certain reactions
______2.
Which of the following enzymes would digest a fat?
a. sucrase
b. fatase
c. protease
d. lipase
_____3. At high temperatures, the rate of enzyme action decreases because the increased heat:
a. changes the pH of the system
b. alters the active site of the enzyme
c. neutralizes the acids and bases in the system
d. increases the concentration of the enzyme
_____4. Enzymes influence chemical reactions in living systems by:
a. providing the substrate required for the reaction to occur
b. affecting the rate at which reactions occur
c. absorbing water released when polymers are formed
d. combining with excess hydrogen to form gaseous wastes
_____5. Which group of organic compounds do enzymes belong to?
a. proteins
b. starches
c. carbohydrates
d. lipids
_____6. The ‘Lock and key model” attempts to explain the mechanism of:
a. cell wall formation
c. sharing of electrons
b. dehydration synthesis
d. enzyme specificity
_____7. Any substance that is acted upon by an enzyme is called a(n):
a. coenzyme
b. substrate c. vitamin
d. polypeptide
_____8. An enzyme that hydrolyzes protein will not act upon starch. This fact is an indication that enzymes are:
a. hydrolytic
b. specific
c. catalytic
d. synthetic
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_____9. Salivary amylase is an enzyme in humans that breaks down starch. The optimum pH for this reaction is 6.7.
The enzyme's effectiveness will NOT be affected by:
a. maintaining the pH of the reaction at 6.7.
b. substrate concentration
c. enzyme concentration
d. decreasing the temperature of the reaction by 15 degrees Celsius.
_____10. A certain enzyme will hydrolyze egg white but not starch. Which statement best explains this observation?
a. Starch molecules are too large to be hydrolyzed.
b. Enzyme molecules act only on specific substrates.
c. Egg white is composed of monosaccharides.
d. Starch is composed of amino acids.
_____11. Which environmental condition would most likely have the LEAST effect on the rate of enzyme-controlled
hydrolytic reactions in humans?
a. the pH of the solution
b. the temperature of the solution
c. the amount of enzyme and substrate present
d. the amount of light present
_____12. Gastric Protease and Intestinal Protease are digestive enzymes found in humans. Which statement best
expresses the information represented in the graph shown?
a.
b.
c.
d.
The action of enzymes varies with pH.
A pH of 7 provides the optimum environment for all digestive enzymes.
Gastric protease is active at from pH 0 to 12.
Acids have a pH greater than 7.
_____13. Lipase, maltase and protease are all members of a group of catalysts known as:
a. hormones b. carbohydrates
c. lipidsd
d. enzymes
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CP Biology
Name
Date
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Enzymes and pH HW #5
1. Review your chemistry notes. What happens to an ionic compound when it is placed in water?
Ionic compounds dissociate in water (oppositely charged ions pull apart from one another).
2. What do we call a compound that releases H+ ions in solution? acid
3. What ions does HCl dissociate into?
4. What is a base?
5.
a.
b.
c.
d.
H+ (and Cl-)
A chemical that releases OH- ions in solution (in water).
Which of the following is true regarding a neutral compound?
in solution the concentration of H+ ions is the same as the concentration of OH- ions.
it has a pH = 7
pure water is an example
all of these
6. A solution with a pH of 8 contains __?__ more H+ ions than a solution with a pH of 12.
a. 1
b. 4
c. 104
d. 10,000
7. Which solution contains more OH- ions?
a. pH 8.2
b. pH 8.3
8. If we mixed KCl (a common salt) with pure water, do you predict the resulting solution would have a pH
above, equal to, or below 7? Explain.
It would only release K+ and Cl-, not H+ or OH-, therefore the
pH would remain neutral (7).
9. What does the pH scale measure?
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Concentration of H+ ions in a solution.
10. Label the following solutions as acid, base or neutral.
__Acid (strong)___pH 1
_Base (weak)________pH 8.9
_Base (stong)________pH 14
_Acid (strong)________pH 3.2
_Neutral________pH 7
11. Why is pure water neutral?
Equal amounts of H+ and OH- ions.
12. On the pH scale below, label the arrows on either side of "Neutral" to indicate which direction is increasingly
acidic and which is increasingly basic.
Acid
Base
 more acidic
more basic 
More H+ than OH-
More OH- than H+
13. Name any two solutions that have more H+ ions than OH– ions.
Acids: lemon juice, stomach acid, acid rain, orange juice, soda
14. Name any two solutions that have more OH– ions than H+ ions.
Bases: bleach, soap, blood, ammonia
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