UCLA LS7A Final

Sometimes, atoms gain or lose particles. The loss of which of the following results in a change of atomic mass?

a neutron and a proton

Which of the following CORRECTLY pairs the particles of an atom with their physical properties?

proton-positively charged; neutron-uncharged; electron-negatively charged

Sometimes, atoms gain or lose particles. The loss of which of the following would result in a change of overall electrical charge?

protons or electrons

For an atom that is NOT an ion, which of the following must be TRUE?

The number of electrons equals the number of protons.

A woman's doctor tells her to gargle with salt water. She stirs a tablespoon of salt into a cup of warm water and watches it dissolve. Why does the salt dissolve in water?

The positive hydrogen atoms in water molecules are attracted to chlorine ions, and the negative oxygen atoms in water molecules are attracted to sodium ions.

A polar bond is due to:

uneven sharing of electrons in a covalent bond.

The structural formula for hydrogen gas (H2) is represented as H?H. Here, the dash (?) represents a(n):

chemical bond.

A molecule of common table salt, or NaCl, is the result of _____ bond forming between a sodium (Na) atom and a chlorine (Cl) atom.

an ionic

Which of the following statements is TRUE regarding a polar molecule?

A polar molecule is hydrophilic and it will dissolve in water.

Water is able to dissolve many compounds as a result of which of the following?

the fact that water molecules are polar

Water is neither hydrophilic nor hydrophobic, because these terms only define the interaction of other molecules with water molecules.

False

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

How many hydrogen atoms are present in a hydrocarbon chain of five carbon atoms with two double bonds and two single bonds?

8

Refer to the periodic table, and decide which of the following molecules is held together by ionic bonds.

KCl

Three carbon atoms are linked by single covalent bonds such that they form the shape of a V. All of the unshared electrons form covalent bonds with hydrogen. How many hydrogen atoms does this molecule contain?

8

Refer to the periodic table, and decide which of the following molecules is held together by polar covalent bonds.

NH3

Refer to the periodic table, and decide which of the following molecules is held together by nonpolar covalent bonds.

CH4

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 a hydrogen bond with another Molecule X:

False

Molecule X could form an ionic bond with Na+:

True

Molecule X could form an ionic bond with Cl-:

False

The lipid components of cellular membranes often include:

phospholipids and cholesterol.

Which one of the following is NOT a component of an animal cell's plasma membrane?

nucleic acid

The interior region of a phospholipid bilayer is characterized as:

hydrophobic.

A protein that is temporarily associated with a biological membrane is a(n):

peripheral membrane protein.

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.

All cells have:

genetic information.

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 eukaryotic organelle is associated with the breakdown of macromolecules?

lysosome

Which of the following eukaryotic cell structures plays a role in protein trafficking and sorting?

the Golgi apparatus

A bacterial cell, a plant cell, and an animal cell have which of the following structures in common?

cytoplasm

A beaker contains two solutions of salt dissolved in water. The two solutions have different concentrations (measured by molarity, M) and are separated by a membrane that is permeable to salt.

Which of the following statements is TRUE?

There will be a net movement of salt from side B to side A

Some plant cells take advantage of the high concentration of protons outside the cell to move solutes, such as sucrose, across the plasma membrane into the cell where the sucrose concentration is already relatively high. This type of transport is an example of:

secondary active transport.

During osmosis, water moves from a region of _____ to a region of _____.

Both "high solvent concentration; low solvent concentration" AND "low solute concentration; high solute concentration" are correct answers.

Which of the following molecules does NOT easily diffuse across a plasma membrane?

large polar molecules

The random movement of molecules from areas of high concentration to low concentration is referred to as:

diffusion.

Why does active transport require ATP?

An input of energy is needed to allow the movement of molecules from an area of low concentration to one of higher concentration.

A beaker contains two solutions of salt dissolved in water. The two solutions have different concentrations (measured by molarity, M) and are separated by a membrane that is permeable to both salt and water.

Which of the following statements is TRUE?

Side A is hypotonic relative to side B.

The plasma membranes of some plant cells use transport proteins to move protons out of the cell against their concentration gradient (from areas of low proton concentration to areas of high proton concentration). This is an example of:

active transport.

In the figure below, the cell is _____ to the solution. If the membrane is permeable to water, but not to solutes, net movement of water will be _____ the cell. (Note that the units mM represent the total concentration of solute in the solution.)

hypotonic; out of

The beaker in the illustration below contains two solutions of salt with different concentrations (measured by molarity, M). The two solutions are separated by a membrane that is permeable to both salt and water.

Which of the following will you observe immediately in this container?

Net diffusion of water from A to B and of salt from B to A.

The beaker in the illustration below contains two solutions of salt with different concentrations (measured by molarity, M). The two solutions are separated by a membrane that is permeable to both salt and water.

Which of the following will you observe after a long time has passed?

No net diffusion of water or salt across the membrane.

Why does a phospholipid on the cytoplasmic side of the cell membrane rarely flip to the extracellular side if both environments are polar?

The polar head group cannot pass through the nonpolar interior.

Which one of the following molecules would MOST likely require a transport protein to cross the plasma membrane of a red blood cell?

C6H12O6

Phospholipase is an enzyme that cleaves the phosphate head group off a phospholipid molecule. The plasma membrane is not, however, permeable to the enzyme. Imagine a cell where phospholipid A is present in the layer of phospholipids facing the exterior of the cell, and phospholipid B is present in the layer of phospholipids facing the interior of the cell. After adding phospholipase to the medium in which the cell is growing, what would you expect to find in the fluid surrounding the cell?

the phosphate head group from phospholipid A only

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 concentration of Waste molecules is ________ inside the cell compared to the outside.

Lower

What will happen when the Na+ channel is open?

There will be net movement of Na+ into the cell through the channel

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

Anabolic pathways of metabolism are pathways that:

build complex molecules from simple ones.

Energy input in the form of ATP is needed in which of the following processes?

anabolism

Imagine that a bowling ball is placed at various locations along a staircase. At which location does the ball possess the GREATEST amount of potential energy?

at the top of the stairs

Which of the following is considered a form of kinetic energy?

All of these choices are correct.

A carbohydrate such as glucose has a great deal of _____ energy.

potential

The first law of thermodynamics states that:

energy cannot be created or destroyed.

The second law of thermodynamics states that:

there is an increase in disorder in the universe over time.

Which of the following statements violates the first law of thermodynamics?

Cells make energy when they produce ATP.

Which of the following describes ATP hydrolysis? (Select all that apply.)

spontaneous

exergonic

often coupled to a reaction that has a positive ΔG

Which of the following is true about spontaneous chemical reactions?

The reactions are exergonic.

Reactions in which there is a negative change in free energy (-ΔG) are:

spontaneous and exergonic.

Which of the following is TRUE about exergonic reactions?

Energy is released from the reactants.

Gibbs free energy is defined as:

the amount of energy available to do work.

The highest free energy is found in the _____(s) of a reaction.

transition state

What is the function of an enzyme?

to both increase the rate of a specific reaction and decrease the amount of energy needed to reach the transition state

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 following is TRUE of allosteric inhibitors of an enzyme?

Allosteric inhibitors decrease enzyme activity.

In a reaction, enzymes change the:

activation energy.

Consulting Figure 7.3 if necessary, during which stage(s) of cellular respiration is carbon dioxide released?

stages 2 and 3

A molecule that is _____ loses electrons, and a molecule that is _____ gains electrons.

oxidized; reduced

Which one of the following represents the REDUCED forms of the two major electron carriers?

NADH and FADH2

The _____ forms of the electron carriers NAD+/NADH and FADH/FADH2 have high potential energy.

reduced

In cellular respiration, glucose is _____ to CO2 and oxygen is _____ to water.

oxidized; reduced

In eukaryotic cells, glycolysis occurs in:

the cytoplasm.

The first phase of glycolysis requires the input of two ATP molecules. It is therefore:

endergonic.

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.

In glycolysis, ATP is synthesized by:

substrate-level phosphorylation.

At the end of glycolysis, the carbon molecules originally found in the starting glucose molecule are in the form of:

two pyruvate molecules.

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

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 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 B could be coupled to Reaction D:

False

Which of the following examples is considered catabolism? (Select all that apply.)

a person losing weight on a calorie restriction diet

use of fat (triglyceride) stores as a cellular energy source

hydrolysis of glycogen (a glucose polymer) during activity

Which of the following reactions would you predict could be coupled to ATP synthesis from ADP + Pi? (Select all that apply.)

creatine phosphate + H2O → creatine + Pi, ΔG - 10.3 kcal/mol

phosphoenolpyruvate + H2O → pyruvate + Pi, ΔG - 14.8 kcal/mol

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

In the metabolic pathway illustrated below, the starting material (substrate A) is converted equally to one of two end products, E or G. Use the diagram of the pathway below to answer the following questions. 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, which of the following would you expect to observe as the amount of G increases in the cell?

an increase in the production of E

When carbohydrates are oxidized, the C-H bonds of the carbohydrate become C=O bonds of carbon dioxide. Oxidation is defined as a loss of electrons, but carbon does not become positively charged in the process. Why then is this considered oxidation?

The shared electrons in C-O bonds spend less time close to the carbon nucleus than the shared electrons in C-H bonds.

Which of the following is/are TRUE regarding redox reactions? (Select all that apply.)

If a molecule accepts electrons, it has been reduced.

A molecule that has gained H atoms is said to be reduced.

Oxidizing agents accept electrons.

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

Drug B could be working as an allosteric inhibitor at all substrate concentrations:

True

Which drug causes the enzyme to reach saturation at the lowest substrate concentration?

Drug B

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

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

In eukaryotes, pyruvate oxidation takes place in the:

mitochondrial matrix.

When a single pyruvate is converted to acetyl-CoA, the other products of the reaction are:

NADH and CO2.

Pyruvate oxidation is an important stage in cellular respiration because it:

links glycolysis with the citric acid cycle.

The citric acid cycle takes place in the:

mitochondrial matrix.

A single molecule of glucose requires _____ "turn(s)" through the citric acid cycle for its chemical energy to be completely harvested.

2

During the citric acid cycle:

ATP is synthesized by substrate-level phosphorylation.

During the citric acid cycle, the production of CO2 is the result of the _____ of intermediate compounds of the citric acid cycle coupled to the production of _____.

oxidation; NADH

What is the FINAL electron acceptor in the electron transport chain?

oxygen