Name_____________________________ Course ______________________
Problem Set # 2: ENERGY, ENZYMES AND THE PLASMA MEMBRANE
1. What is meant by catabolic and anabolic reactions? Which of these refer to the following?
A. Exergonic/ Exothermic B. Endogonic/ Endothermic C. -G D. +G. What is G=0?
2. Define Oxidation, Reduction, and Redox. In the following equation, which is has been oxidized
and reduced, then tell which is the oxidizing agent and the reducing agent.
HCl  H+ Cl3. Give examples of potential and kinetic energy
4. What value determines the spontaneity of a reaction? How do you define free energy?
Enthalphy? Entropy? Is energy required to increase Entrophy?
5. Label the following below: E, E1, E2, A+B, A---B, A—E—B, AB, and t
6. Draw a cartoon picture of a protein (enzyme) containing primary, secondary, tertiary, and
quaternary structures. Tell what chemical and physical properties would destroy each structure.
7. Draw the structure of an enzyme and substrate. Label the following components: Active Site,
Reactive Site, and Allosteric Site. Describe the two theories on how enzymes bind to their
substrate. Which theory is most widely accepted? Since most enzymes are proteins, they may
have primary, secondary, tertiary and quaternary structures. Thus, enzymes are affected by the
same physical and chemical properties as proteins. How are cofactors and coenzymes
important?
8. Which of the three mechanisms of enzyme actions is depicted below? What are the other two?
9.
Define Km in words and mathematically? What might it be used to calculate? What are negative
feedback inhibitions, competitive and noncompetitive inhibitions? Draw the Michaelis-Menten
and Lineweaver-Burke Model of competitive and noncompetitive inhibitions of enzymes.
10. Rxn 1 represents data for the uninhibited enzyme reaction. Rxns 2 and 3 represent data
collected in the presence of two different inhibitors, each present at 10 mM. Assuming the amount
of enzyme is the same in each case, determine Km, and Vm for the enzyme, then tell how you
would overcome the inhibition.
[S] mM
Reaction #1
Reaction #2
Reaction #3
1
2.5
1.17
0.77
2
4.0
2.1
1.25
5
6.3
4.0
2.0
7
7.6
7.6
2.5
10
7.6
7.6
2.5
Energy and Enzymes
1. Define metabolism in your own words.
2. What is the 1st law of thermodynamics?
3. What is the 2nd law of thermodynamics?
4. For the following reaction: C6H12O6
indicate reactants and products.
+ 6 O2

6 H20 + 6CO2 + 686 kcal/mol
Is this endergonic or exergonic? How can you tell?
What would be necessary for this reaction to proceed in the opposite direction?
5. What is the difference between ATP & ADP?
6. What is the role of ATP in this reaction?
7. Enzymes are like inorganic catalysts in that they do what to the activation energy?
________________
8. What is the opening where the substrate fits into an enzyme molecule called?
9. What is the optimum temperature for most human enzymes?
10. Why do enzymes have optimal temperatures and pH for their activity
11. How are vitamins related to cofactors and coenzymes?
12. What does a competitive inhibitor compete for?
13. What molecule combines with the enzyme to cause inhibition?
What does it do to cause the inhibition?
14. What is the difference between competitive and non-competitive inhibition?
Review Questions
1. Catalysts:
slow down chemical reactions
are used up in reactions
provide an alternative reaction pathway
increase the activation energy
2. In an endergonic reaction:
energy is absorbed from the surroundings
bonds being formed are the same strength as bonds being broken
energy is released to the surroundings
bonds being formed are stronger than bonds being broken
3. Which is NOT true of enzymes:
They alter reactions thermodynamically by adding energy to the reaction
They are used in reactions in small amounts
They may require metal ions or organic molecules to function
Noncompetitive inhibitors bind to their allosteric sites
4. Examples of anabolic reactions include:
hydrolysis reactions
the breakdown of carbohydrates
the breakdown of lipids
the build up of proteins
5. The conversion of glucose to carbon dioxide and water is an example of:
a catabolic reaction.
a condensation reaction
an esterification reaction
an anabolic reaction
6. Which of the following is not a feature of collision theory?
at high temperatures molecules have more energy than at low temperatures
the rate of chemical reactions increases with increasing temperatures
the more molecules present, the faster the reaction
the reaction is faster in dilute solute solutions than in concentrated
1. Draw a phospholipid with a serine head (phosphatidylserine). Tell why the head gives the plasma
membrane an overall negative charge.
2. Draw the following peptide and tell which secondary structure it would form:
Ser-Tyr-Lys-Thr-Asp-Gln-Apn
Plasma Membrane
Please provide the best answers to each question in the space provided below, then for each question,
explain why the answer you chose is correct.
For Example: Autotrophs make their food by which of the following processes?
a. Respiration
b. Photosynthesis
c. Fermentation
d. Oxidation
Answer: B. Photosynthesis is the process whereby autotrophs make their own food using carbon dioxide
and water in the presence of sunlight and chlorophyll.
Which of the following Scientist(s) described the contemporary “fluidmosiac”model of the plasma Membrane
a. Davson and Nicholson
b. Nicholson and Danielle
c. Singer and Davson
d. Nicholson and Singer
Answer:_________________________________________________________________
________________________________________________________________________
1.
The “fluid-mosaic” model of the PM differ from the first proposed model in that:
a. The first model did not have cholesterol
b. The first model was devoid of some lipids
c. The first model was devoid of some proteins
d. The first mode was devoid of some carbohydrates
Answer:_________________________________________________________________
________________________________________________________________________
2.
3.
Which is most likely to be a membrane receptor protein?
a. A glycosylated protein containing three hydrophobic regions
b. A glycosylated protein devoid of hydrophobic regions
c. A protein containing hydrophobic regions but devoid of sugars
d. A glycosylated protein devoid of hydrophilic regions
Answer:_________________________________________________________________
________________________________________________________________________
4.
Which secondary structures of proteins are formed within the PM?
a. Alpha-pleated sheets
b. Beta-pleated sheets
c. Alpha-helicies
d. Beta-helicies
Answer:_________________________________________________________________
________________________________________________________________________
5.
Intergal proteins project
a. entirely outside of the bilayer on the extracellular surface
b. entirely through the membrane having N- and C- terminus exposed.
c. entirely outside of the bilayer on the cytoplasmic surface
d. outside bilayer but covalently linked to lipids within membrane
Answer:_________________________________________________________________
________________________________________________________________________
6.
Which is the driving force which maintains the lipid bilayer?
a. Van der waals forces
b. Hydrophobic interactions
c. Hydrophilic interactions
d. Ionic interactions
Answer:_________________________________________________________________
________________________________________________________________________
7.
What affect do lipids with double bonds in their nonpolar tails have on the integrity of the PM?
a. They increase the fluidity of the PM
b. They decrease the fluidity of the PM
c. They allow more lipids to pack tighter in the membrane
d. They cause the membrane to become less stable
Answer:_________________________________________________________________
________________________________________________________________________
8.
As the fluidity of the PM increases, what happens to the entropy?
a. increases
b. decreases
c. stays the same
d. none of the above
Answer:_________________________________________________________________
________________________________________________________________________
9.
The consistency of membranes at various temperatures can be understood using the
Margarine and Butter analogy. Butter contains longer saturated chains of fat derived from
animals while Margarine contains short polyunsaturated fats derived from corn oil. When
taken directly from the refrigerator, Margarine can be spread with ease while the Butter does
not. What conclusion should you draw regarding how the composition of membrane lipid
regulate the fluidity of the PM?
a. Longer chains exhibit more double bonds and increases contact of lipids
b. Longer chain exhibit fewer double bonds and increases contact of lipids
c. Shorter chains exhibit more double bonds and increases contact of lipids
d. Shorter chains exhibit more double bonds and increases contact of lipids
Answer:_________________________________________________________________
_____________________________________________________________________
10.
Which PM lipid covalently anchors proteins?
a. Phosphoglycerides
b. Sphingolipids
c. Cholesterol
d. Triglycerides
Answer:_________________________________________________________________
________________________________________________________________________
11.
Which PM lipid is the least amphipathic?
a. Phosphoglycerides
b. Sphingolipids
c. Cholesterol
d. Triglycerides
Answer:_________________________________________________________________
________________________________________________________________________
12.
Which of the following is not a function of the PM?
a. Signal Transduction
b. Energy Transduction
c. Regulates which molecules enters and exits cell
d. Site of Biochemical events such as production of macromolecules
Answer:_________________________________________________________________
________________________________________________________________________
13.
Which two PM phospholipids have negative charges?
a. Phosphatidylcholine and Phosphatidylethanolamine
b. Phosphatidylethanolamine and Phosphatidylserine
c. Phosphatidylinositol and Phosphatidylserine
d. Phosphatidylserine and Phosphatidylcholine
Answer:_________________________________________________________________
________________________________________________________________________
14.
Which PM lipid is the only true glycolipid?
a. Phosphatidylcholine
b. Phosphatidylethanolamine
c. Sphingolipid
d. Cholesterol
Answer:_________________________________________________________________
________________________________________________________________________
15.
Which is NOT a function of the Plasma Membrane
a. It serves as a barrier allowing all molecules to enter cell
b. It serves as a site for energy and signal transductions
c. It is composed of lipids, proteins, and carbohydrates
d. It compartmentalizes the cells
Answer:_________________________________________________________________
________________________________________________________________________
16.
Cholesterol, which is not present in bacteria, controls the PM fluidity of animal cells. Which is
the CORRECT orientation of the hydroxyl group of the four-member ring of cholesterol in the
PM.
a. The hydroxyl group is oriented inside the membrane
b. The hydroxyl group is oriented toward the cytoplasm
c. The hydroxyl group is oriented toward other cholesterol molecules
d. The hydroxyl group is oriented toward the membrane surface
Answer:_________________________________________________________________
_____________________________________________________________________
17.
PM carbohydrates are oriented:
a. Inside the membrane
b. Toward the cytoplasm
c. Toward other carbohydrate molecules
d. Away from the cytoplasm and inside organelles
Answer:_________________________________________________________________
________________________________________________________________________
18.
Sugars constituents various on red blood cells depending on blood type, why would giving
someone the wrong blood type be fatal?
a. Blood groups differ in the levels of hemoglobin they carry
b. The body would view the sugars as antigens and form antibodies against them.
c. Because of the incompatible sugar arrangement, the blood would not flow to the heart
properly.
d. The foreign sugar sequences will attack to the sugar sequences on normal cells.
Answer:_________________________________________________________________
________________________________________________________________________
19.
NaCl most likely get into cells by which of the following methods?
a. Diffusion
b. Facilitated Transport
c. Osmosis
d. Active Transport
Answer:_________________________________________________________________
________________________________________________________________________
20.
Sufferers of type II diabetes (adult onset) have normal insulin levels but no target cell
response due to deficiency in receptors for insulin. Which type of transport is missing?
a. Diffusion
b. Facilitated Transport
c. Osmosis
d. Active Transport
Answer:_________________________________________________________________
________________________________________________________________________
21.
The movement of molecules against a gradient refers to which type of transport?
a. Diffusion
b. Facilitated Transport
c. Osmosis
d. Active Transport
Answer:_________________________________________________________________
________________________________________________________________________
22.
Which is the correct exchange of sodium and potassium in the Na/K pump of cells?
a. three sodium for three potassium
b. two sodium for three potassium
c. three sodium for two potassium
d. two sodium for one potassium
Answer:_________________________________________________________________
________________________________________________________________________
23.
This type of transport is important to cells because they receive their oxygen and rid
themselves of carbon dioxide by this method:
a. Diffusion
b. Facilitated Transport
c. Osmosis
d. Active Transport
Answer:_________________________________________________________________
________________________________________________________________________
24.
Maintaining membrane fluidity is important to cells because?
a. Cells are able to maintain proper function at different temperatures
b. Cells can break down membranes lipids very quickly when energy is needed
c. Larger molecules can pass through the membrane when fluidity is increased
d. The membrane fluidity helps to maintain the positions of glycoproteins and glycolipids
Answer:_________________________________________________________________
________________________________________________________________________
25.
Scientists agreed that the plasma membrane was the site of biochemical events when
peroxide was broken to produce bubbles containing?
a. water
b. hydrogen
c. oxygen
d. carbon dioxide
Answer:_________________________________________________________________
________________________________________________________________________
Membrane Transport
Please review the following types of transport:
I.
Passive: Diffusion, facilitated, and Osmosis
II.
Active
_________Passive Transport
_________Active Transport
_________Diffusion
_________Facilitated Transport
_________Osmosis
_________Hypertonic
_________Isotonic
_________Hypotonic
A. A solution which causes cells to shrink
B. The movement of a solvent across a semi-permeable
membrane from an area of high concentration to an
area of lower concentration.
C. The Sodium Potassium Pump is an example of this
transport.
D. The movement of glucose from the blood to the
brain or kidney for excretion in diabetics.
E. The movement of oxygen from bronchioles to
bloodstream
F. A solution which causes cells to swell
G. A solution were there is no change in gain or loss
H. Gases and ions use this method of transport
I. The movement of solutes from an area of lower
concentration to an area of higher concerntration.