CP Biology Name Date Period
HOMEWORK PACKET
UNIT 2B:
Basic Biochemistry
Part 2– Proteins, Enzymes, pH
Proteins
1) What are the small, repeating units (monomer units) of proteins called?__amino acids______
2) What are two different names for the type of bonds which join two protein units?
___covalent bond______and ___peptide bond______
3) List the parts of an amino acid: __1) carboxyl group, 2) amino group, 3) R – group, 4) Central carbon, and 5) Lone hydrogen.______
4) Draw the general structure of an amino acid. Circle the R group, draw a square around the carboxyl group and draw a triangle around the amino group.
5) What part of an amino acid differs from one type amino acid to the next? (circle one )
amino group (-NH2-) organic acid (-COOH) central carbon R groups
6) List the name and function of a specific protein: __Hemoglobin caries oxygen in the red blood cell, actin and myosin are muscle proteins that help our heart to beat and our arm and leg muscles to move, and collagen is a protein that keeps our skin soft and supple.______
7) How many amino acids are combined to form a dipeptide? ___2______a tripeptide? ______3______
How large are most proteins? __100’s to 1000’s______
8) What is the general name of a protein that catalyzes chemical reactions? ____enzyme______
9) Give a more specific name for a protein in your digestive system that speeds hydrolysis of lipids.
____lipase______
10) What happens to the structure of a protein as it is heated to a high temperature? What effect does this have
on its function? _____High temperatures may cause a change in a protein or polypeptide’s shape, thus
______altering or causing the protein to become NON-functional (does not work).
______
11) Complete the following analogies:
a) amino acid is to protein as glycerol and 3 fatty acids are to ___triglyceride (lipid)______
b) carbohydrate is to glycogen as protein is to polypeptide (hemoglobin, collegen…)_(use an example from question #6)
c) synthesis is to proteins as hydrolysis is to __amino acids______
12) Name 5 foods that are rich sources of proteins. nuts, beans, animal meats, fish, eggs, soy.
13) How many amino acids are in the polypeptide shown below? 4
How many peptide bonds does it contain? 3
How many water molecules were created when it was formed? 3
14) All proteins contain these elements: C, H, O, N
CP Biology Name Date Pd
Enzymes & pH HW#1
1. What is a chemical reaction?
The process by which we combine or break down substances to form new products.
2. Complete the table about chemicals in a chemical reaction.
Chemicals in a Chemical ReactionChemicals / Definition
Reactants / Elements that enter into a chemical reaction (“ingredients”)
Products / Elements that are created by a chemical reaction (“results”)
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.
l Draw an arrow on each graph to show the energy of activation.
REACTION "A" REACTION "B"
Time Time
4. Which of the above reactions would be considered an energy-absorbing (endergonic) reaction? Why? Graph A: End with more energy than you began.
5. Define "activation energy".
The energy needed to begin a reaction
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
CP Biology Name Date Pd
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______, ___type______, 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 _homeostasis______in cells.
2. What do we commonly call the organic catalysts found in cells? enzymes
3. Why is a catalyst highly effective in small amounts? they are reusable (not altered or used up during the reaction) – it speeds up the reaction.
4. Enzymes typically have “-ase” at the end of their name like “sucrase”. Look at the picture. Describe what sucrase does to sucrose. sucrose is being hydrolyzed (broken down) into its monomers (glucose & fructose)
5. How does heat act as a catalyst? Why can't cells rely on heat as their main catalyst for chemical reactions? heat speeds up the movement of molecule, causing them to interact.
heat (or too high heat) can denature proteins (cause them to lose their shape), thus killing cells!
6. How does the addition of a catalyst affect the energy of activation of a chemical reaction?
The addition of a catalyst (or an enzyme) LOWERS the energy needed to begin the reaction.
7. Using the analogy of a lock and key, explain what the expression “enzymes
are specific” means. A certain enzyme will only react with a specific substrate. One enzyme, one reaction. An enzyme has a specific active site that will only allow a specific substrate to bind to it - to begin the reaction.
TRUE OR FALSE - if false, correct the statement.
__T___8. Enzymes are reusable.
Enzymes substrate(s)
__F___9. Substrates strain the bonds of enzyme molecules, reducing the amount of energy needed for old
bonds to break and new bonds to form.
faster
__F___10. Enzyme-assisted reactions occur much more slowly than they would if the enzyme were not
present.
a specific
___F__11. A particular enzyme can catalyze many different types of reactions.
__T___12. Some enzymes assist with hydrolysis, whereas others assist with dehydration synthesis.
CP Biology Name Date Pd
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
__F___6. True or False: An enzyme typically works well throughout a wide range of varying temperature and
pH conditions.
7. Define homeostasis. The ability to sustain or maintain a certain environment or condition(s), over time.
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.
Extremely high temperatures can denature enzymes (due to rapid movement of atoms & molecules) thus causing the enzyme to unfold and lose its structure (and its function). Therefore, the cell or organism may not be able to perform metabolic functions and/or maintain homeostasis. This can lead to the death of a cell or organism!
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
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 bond (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?
- sucrase b. fatase c. protease d. lipase
_____3. At very 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
_____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. The action of enzymes varies with pH.
b. A pH of 7 provides the optimum environment for all digestive enzymes.
c. Gastric protease is active from pH 0 to 12.
d. 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. lipids d d. enzymes
CP Biology Name Date Pd
Enzymes and pH HW #5
1. Review your chemistry notes. What happens to an ionic compound when it is placed in water?
Ionic compounds will dissociate (or separate) in water.
2. What do we call a compound that releases H+ ions in solution? acid
3. What ions does HCl dissociate into? H+
4. What is a base? pH greater than 7, more OH- ions than H+ ions, tastes bitter, feels slippery
5. Which of the following is true regarding a neutral compound?
a. in solution the concentration of H+ ions is the same as the concentration of OH- ions.
b. it has a pH = 7
c. pure water is an example
d. 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.
Below or less than 7 (acid). KCl releases more H+ ions into solution.
9. What does the pH scale measure? Concentration of H+ ions.
10. Label the following solutions as acid, base or neutral.
___A______pH 1
___B______pH 8.9
___B______pH 14
___A______pH 3.2
___N______pH 7
11. Why is pure water neutral?