UCLA - LS7A Midterm
Nicotinamide adenine dinucleotide is an electron carrier in many important cellular reactions. It exists in an oxidized form (NAD+) and a reduced form (NADH). What is the missing component in the reaction: NAD+ + ____ + H+ → NADH?
2e-
Which of the statements is true of allosteric inhibitors of an enzyme?
Allosteric inhibitors decrease enzyme activity.
Which molecule would most likely require a transport protein to cross the plasma membrane of a red blood cell?
C6H12O6
Compared to when the Na+ channel is closed, how will the transport of Waste molecules change when the Na+ channel is open? The rate of Waste transport out of the cell will:
Decrease
Many cellular processes represent work that requires the expenditure of energy. Which of the actions is not a cellular process that requires the cell to expend energy?
Diffusion of water into cells.
The drug you are developing is intended for patients who have enzymatic activity that is too low, so the drug is used to increase enzyme activity. Which drug would be more effective for treatment?
Drug A
Which drug causes the enzyme to reach saturation at the lowest substrate concentration?
Drug B
Which statement is true about exergonic reactions?
Energy is released from the reactants.
Reaction B could be coupled to Reaction D:
False
The graph below shows the effects of two drugs on enzyme activity. Use this graph to answer the questions below. Drug A could be working as an allosteric inhibitor at all substrate concentrations:
False
The reaction of iron with oxygen to form iron oxide is an example of an oxidation-reduction reaction: 4Fe + 3O2 → 2Fe2O3. In this reaction ______ loses electrons and is _________.
Fe; oxidized
The concentration of Waste molecules is ________ inside the cell compared to the outside.
Lower
Which example represents the reduced forms of the two major electron carriers?
NADH and FADH2
The diagram below shows a cell with three different membrane transport proteins. The Na+/K+ Pump is a primary active transporter and the Na+/Waste Co-transporter is a secondary active transporter. Arrows show the direction of net movement of molecules through the Pump and Co-transporter. The Na+ Channel can exist in either a closed state (no Na+ can pass through) or an open state (Na+ can pass through). Use this diagram to answer the questions below. What will happen to the net movement of Waste molecules if the Na+/K+ Pump stops working?
Net movement of Waste out of the cell will continue for some time and then all net movement of Waste in or out of the cell will stop
The reaction of iron with oxygen to form iron oxide is an example of an oxidation-reduction reaction: 4Fe + 3O2 → 2Fe2O3. In this reaction ______ gains electrons and is _________.
O2; reduced
Which of the factors accounts for the higher potential energy of C-C and C-H bonds compared to C-O and H-O bonds?
The C-C and C-H bonds are weak, thus requiring a lot of energy to hold together.
Although the phospholipid molecules can be in constant lateral movement, they very rarely flip from one side of the bilayer to the other. Which of the answer choices could explain this?
The head groups are repelled by the hydrophobic membrane interior.
In the experiment that showed membrane fluidity, what was the purpose of shining a laser on the membrane?
The laser light destroys the dye fluorescence.
A beaker contains two solutions of salt dissolved in water. The two solutions have different concentrations of salt (measured by molarity, M) and are separated by a membrane that is permeable to both salt and water. The salt and water will move through the membrane by diffusion. Which statement is true about the diffusion of these solutions?
There will be a net movement of salt from side B to side A and net movement of water from side A to side B.
What will happen when the Na+ channel is open?
There will be net movement of Na+ into the cell through the channel
Most patients respond well to treatment with the most effective drug (your answer to question 4). However, one unusual patient responds poorly, and her enzymatic activity decreases even further when she takes the drug. From this observation you can conclude that:
This patient's substrate concentration is below 100 uM
Drug B could be working as an allosteric inhibitor at all substrate concentrations:
True
Reaction A should occur at a faster rate than Reaction D:
True
Refer to the free energy diagrams below to answer the following questions. You may assume that the y-axis is the same and directly comparable for all four reactions. Reaction C is endergonic:
True
A bacterial cell, a plant cell, and an animal cell have which structure in common?
a cytoplasm
Which of the choices is an example of kinetic energy?
a photon of light
Which of the statements is true regarding a polar molecule?
a polar molecule is hydrophilic and will dissolve in water
In a reaction, enzymes change the:
activation energy.
You notice that a chemical reaction in your system is happening at a slow rate. You want to speed up the reaction. What do you do?
add an enzyme that catalyzes the reaction
Which of the choices is an example of potential energy?
an electrochemical gradient across the cell membrane
In the metabolic pathway illustrated, the reactant (substrate A) is converted equally to one of two end products, E or G. Use the diagram of the pathway to answer the question. Letters indicate the substrates and products, and numbers indicate the enzymes. In this pathway, the intermediate, C, is a substrate for both enzyme 3 and enzyme 5 and is converted with equal efficiency to D and F. If end product G inhibits enzyme 5, what would you expect to observe as the amount of G increases in the cell?
an increase in the production of E
Which of the processes requires energy input in the form of ATP?
anabolism
How do eukaryotic plant and animal cells differ from one another?
animal cells do not have chloroplasts and cell walls, and plant cells do
Which labeled arrow in the figure represents the activation energy (EA)?
arrow b
If you added an enzyme that catalyzes the reaction shown, you would predict that ____ would be reduced but ____ would remain the same.
arrow b; arrow e
Which labeled arrow in the figure represents the change in free energy of the reaction (G)?
arrow e
An example of potential energy is a ball sitting _____ of the stairs.
at the bottom, at the top, & in the middle (all of these choices are correct)
When chemical reactions occur the _____ but the _____.
atoms retain their identities; arrangement of bonds changes
The transition state is that portion of the progress of a chemical reaction with a large amount of energy found in _______ reactions.
both endergonic and exergonic
Anabolic pathways of metabolism are pathways that
build complex molecules from simple one
If present in a molecule, which atom is least likely to participate in hydrogen bonds with water?
carbon
The plasma membrane is composed of a phospholipid bilayer and associated proteins. What else is commonly found in the plasma membranes of animal cells?
cholesterol
The phosphorylation of glucose during glycolysis serves to: Select all that apply.
destabilize the molecule, making it easier to cleave, trap imported glucose inside the cell.
The beaker in the illustration contains two solutions of salt with different concentrations (measured by molarity, M). The two solutions are separated by a membrane that is permeable to water but not to salt. What will occur in this container?
diffusion of water from A to B but no diffusion of salt
Three carbon atoms are linked by single covalent bond such that those carbon atoms and bonds together form the shape of a V. All of the unshared electrons form covalent bonds with hydrogen. How many hydrogen atoms does this molecule contain?
eight
Consider the graph. In this figure the solid blue curve plots free energy of a reaction against progress of that reaction. This reaction is:
endergonic.
The first phase of glycolysis requires the input of two ATP molecules. It is therefore:
endergonic.
The first law of thermodynamics states that:
energy cannot be created or destroyed.
Molecule X could form a hydrogen bond with another Molecule X:
false
Molecule X could form an ionic bond with Cl-
false
Three different molecules are shown below. The electronegativity of sulfur (S) is similar to the electronegativity of carbon (C) and the electronegativity of nitrogen (N) is similar to the electronegativity of oxygen (O). T/F: Molecule 1 only contains nonpolar covalent bonds.
false
Three different molecules are shown below. The electronegativity of sulfur (S) is similar to the electronegativity of carbon (C) and the electronegativity of nitrogen (N) is similar to the electronegativity of oxygen (O). T/F: Molecule 2 is hydrophilic.
false
Three different molecules are shown below. The electronegativity of sulfur (S) is similar to the electronegativity of carbon (C) and the electronegativity of nitrogen (N) is similar to the electronegativity of oxygen (O). T/F: Molecule 3 could form a hydrogen bond with water.
false
Water is neither hydrophilic nor hydrophobic, because these terms only define the interaction of other molecules with water molecules.
false
In an ice crystal, any single water molecule typically forms hydrogen bonds with how many other water molecules?
four
The carbon atom in CO2 shares _______ electron pairs. After the reaction with H2O to form H2CO3 is completed the carbon atom shares ________ electron pairs.
four; four
All cells have:
genetic information
Which of the following examples describe catabolic processes? Select all that apply.
hydrolysis of glycogen (a glucose polymer) during physical activity, use of fat (triglyceride) stores as a cellular energy source, a person losing weight on a calorie restriction diet
The interior region of a phospholipid bilayer is characterized as:
hydrophobic
Which of the types of molecules depicted in the figure is amphipathic?
integral membrane proteins, cholesterol, and phospholipids
In a metabolic pathway, a series of enzymatic reactions catalyzes the conversion of molecule A to molecule E. Several intermediate steps are involved in which the product of one reaction becomes the substrate for the next. The graph illustrates the changes of free energy that occur at each step in the pathway. Overall, this _____, based on the changes in free energy that take place as A is converted to E.
is an anabolic pathway
What else is necessary in order for a hydrogen atom in a molecule to participate in a hydrogen bond?
it must be bonded to a more electronegative atom
The image illustrates our understanding of how typical cell membranes are structured. Which line is pointing at a protein?
line a
The image illustrates our understanding of how typical cell membranes are structured. Which arrow is pointing at the hydrophilic head group of a phospholipid?
line b
The image illustrates our understanding of how typical cell membranes are structured. Which arrow is pointing at a cholesterol?
line d
The reaction of iron with oxygen to form iron oxide is an example of an oxidation-reduction reaction: 4Fe + 3O2 → 2Fe2O3. In this reaction each iron atom will:
lose 3 electrons.
Which eukaryotic organelle is associated with the breakdown of macromolecules?
lysosome
Spontaneous reactions have a _____ ΔG.
negative
A molecule that is _____ loses electrons, and a molecule that is _____ gains electrons.
oxidized; reduced
In cellular respiration, glucose is _____ to CO2 and oxygen is _____ to water.
oxidized; reduced
When chemical reactions occur the _____________ but the _____________.
pairing of atoms that share electron pairs changes; individual atomic nuclei stay the same
The hydrogen atoms in a water molecule have a ________ charge while the oxygen atom has a _________ charge.
partial positive; partial negative
A protein that is temporarily associated with a biological membrane is a(n):
peripheral membrane protein
Which of the reactions would you predict could be coupled to ATP synthesis from ADP + Pi? Select all that apply. Recall that the delta G of ATP synthesis is +7.3 kcal/mol.
phosphoenolpyruvate + H2O → pyruvate + Pi, ΔG - 14.8 kcal/mol, creatine phosphate + H2O → creatine + Pi, ΔG - 10.3 kcal/mol
The lipid components of cellular membranes often include:
phospholipids and cholesterol
What kind of bond joins hydrogen to oxygen in a water molecule?
polar covalent
The unique properties of water are due to the _____ of water molecules and the ability of water to form _____ with other water molecules and with other polar molecules.
polarity; hydrogen bonds
A carbohydrate such as glucose has a great deal of ______ energy.
potential
Which stages of cellular respiration produce CO2 as a waste product?
pyruvate oxidation, and the citric acid cycle
Consider the reactions. The reactions shown present the overall oxidation-reduction reaction in which elemental iron and molecular oxygen react to form iron oxide (A), and also the half reactions showing the oxidation part and the reduction part (B & C). Compare this reaction and its half reactions to the reaction of nicotinamide adenine dinucleotide as an electron carrier in many important cellular reactions: NAD+ + 2e- + H+ → NADHWhich reaction or half reaction is most similar to this NAD+/NADH reaction?
reaction C
The _____ forms of the electron carriers NAD+/NADH and FAD/FADH2 have high potential energy.
reduced
Reactions in which there is a negative change in free energy (-ΔG) are:
spontaneous and exergonic.
In glycolysis, ATP is synthesized by:
substrate-level phosphorylation.
Which eukaryotic cell structure plays a role in protein trafficking and sorting?
the Golgi apparatus
Gibbs free energy is defined as:
the amount of energy available to do work.
Why does ice float?
the crystal lattice forces a less dense arrangement of molecules
In eukaryotic cells, glycolysis occurs in:
the cytoplasm.
Water is able to dissolve many compounds as a result of which fact?
the fact that water molecules are polar
Although the phospholipid molecules can be in constant lateral movement, they very rarely flip from one side of the bilayer to the other. Which of the answer choices could explain this?
the head groups are repelled by the hydrophobic membrane interior
Table sugar can burn in the reaction if ignited: C6H12O6 + 6O2 → 6CO2 + 6H2O and in the process some potential energy of the sugar becomes kinetic energy. Which of the choices represents kinetic energy from this reaction?
the products and their surroundings have more heat
The second law of thermodynamics states that:
there is an increase in disorder in the universe over time.
What are the functions of an enzyme? Select all that apply.
to increase the rate of a specific reaction, to lower the activation energy for the reaction
The highest free energy is found in the _____(s) of a reaction.
transition state
If cells had single-layer membranes like micelles, how would the structures of transmembrane proteins be affected?
transmembrane proteins would possess a hydrophobic region in the cell interior and a hydrophilic region in the extracellular space
Consider the molecule shown here (Molecule X). The minus sign next to oxygen represents a full negative charge on that atom. Answer the following questions about Molecule X. Molecule X contains at least one nonpolar covalent bond:
true
Molecule X could form a hydrogen bond with water:
true
Molecule X could form an ionic bond with Na+:
true
Three different molecules are shown below. The electronegativity of sulfur (S) is similar to the electronegativity of carbon (C) and the electronegativity of nitrogen (N) is similar to the electronegativity of oxygen (O). T/F: Molecule 1 could form a hydrogen bond with another Molecule 1.
true
Which of the choices is considered a form of kinetic energy?
wind, light, heat, & a rolling ball (all of these choices are correct)
When H2CO3 reacts to form CO2 and H2O, what is the net change in the number of shared electron pairs?
zero
