LS7A UCLA Midterm 1 200

In eukaryotic cells, glycolysis occurs in:

cytoplasm

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

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

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

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

The number of electrons equals the number of protons.

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

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

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.

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

chemical bond.

A polar bond is due to:

uneven sharing of electrons in a covalent bond

What kind of bond joins hydrogen to oxygen in a water molecule?

polar covalent bond

The hydrogen atoms in a water molecule have a ________BLANK charge while the oxygen atom has a _________BLANK charge.

partial positive; partial negative

In an ice crystal, any single water molecule typically forms hydrogen bonds with how many other water molecules?

4

If present in a molecule, which atom is least likely to participate in hydrogen bonds with water?

Nitrogen

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.

Why does ice float?

The crystal lattice forces a less dense arrangement of molecules.

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

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

False

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

Of the following types of bonds or interactions between atoms, which is the WEAKEST?

van der Waals forces

The ability of atoms to attract electrons is referred to as:

electronegativity

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

NH3

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 nonpolar covalent bonds.

CH4

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 ionic bonds.

KCl

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.

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 image above illustrates our understanding of how typical cell membranes are structured. Which arrow is pointing at a protein?

arrow a

The image above illustrates our understanding of how typical cell membranes are structured. Which arrow is pointing at a cholesterol?

arrow d

The image above illustrates our understanding of how typical cell membranes are structured. Which arrow is pointing at the hydrophilic head group of a phospholipid?

arrow b

Which of the types of molecules depicted in the figure above is amphipathic?

integral membrane proteins, cholesterol, and phospholipids

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 following 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.

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.

As molecules move down their concentration gradient, from a more ordered state to a less ordered state, entropy:

is increasing.

Diffusion is best described as the random movement of molecules influenced by:

the thermal energy of the environment and energy transferred from molecular collisions in the cell.

Molecules that are _____________BLANK and _____________BLANK are able to move across the cell membrane via simple diffusion.

hydrophobic; small

At equilibrium, there will be no net movement of molecules across the cell membrane.

true

Simple diffusion of a molecule down its concentration gradient requires an input of energy to the system.

false

Which of the following correctly describes the movement of water across a selectively permeable membrane during osmosis?

The water will move from high water concentration to low water concentration.

& The water will move from low solute concentration to high solute concentration.

A container is divided into two compartments by a membrane that is fully permeable to water and small ions. Water is added to one side of the membrane (side A), and a 5% solution of sodium chloride (NaCl) is added to the other (side B). If allowed to reach equilibrium, which of the following would you predict?

The NaCl concentration on side A and side B will each be 2.5%.

A container is divided into two compartments by a membrane that is fully permeable to water but not to larger molecules. Water is added to one side of the membrane (side A), and an equal volume of a 5% solution of glucose is added to the other (side B). What would you predict will happen?

The water level on side B will increase and on side A will decrease.

A beaker is divided by a membrane that is permeable to water and glucose, but not to sucrose. Equal volumes of solutions are added to side A and B with the initial concentrations as shown below. Initially, the liquid levels on both sides are the same.

After the system described above reaches equilibrium, what can you predict about the water levels?

The water will be higher on side A than on side B.

A beaker is divided by a membrane that is permeable to water and glucose, but not to sucrose. Equal volumes of solutions are added to side A and B with the initial concentrations as shown below. Initially, the liquid levels on both sides are the same.

After the system described above reaches equilibrium, what will be the concentration of glucose on side B?

0.75m

The defining characteristics of active transport are that this category of transport moves substances _________BLANK their concentration gradient and requires ___________BLANK.

against; energy

Which of the following would be the best analogy for an electrochemical gradient across a cellular membrane?

a battery

In the image shown above, an active transport proton pump drives protons out of the cell using energy from ATP. Under some circumstances pumps like this can be run in reverse. If this pump could be reversed, what would be the result in the cytoplasm?

a decrease in pH and an increase in ATP

In the example illustrated in the image above, a substance is moved _______BLANK its concentration gradient using the energy of ______________BLANK.

against; an electrochemical gradient

Why is the transporter in the figure above considered to be an example of "secondary transport"?

It is driven by the proton gradient that was created by energy from ATP.

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

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 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.

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

diffusion

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.

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.

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

Which of the following is an example of kinetic energy?

a photon of light

Which of the following is an example of potential energy?

an electrochemical gradient across the cell membrane

Table sugar can burn in the following reaction if ignited: C6H12O6 + 6O2 → 6CO2 + 6H2O In the process, some potential energy of the sugar becomes kinetic energy. Which of the following represents kinetic energy from this reaction?

The products and their surroundings have more heat.

Which of the following accounts for the higher potential energy of C-C and C-H bonds compared to C-O and H-O bonds?

The electrons in C-C and C-H are farther from the nuclei.

Many cellular processes represent work that requires the expenditure of energy. Which of the following is not a cellular process that requires the cell to expend energy?

diffusion of water into cells

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 rolling ball

light

wind

heat

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.

When chemical reactions occur the __________BLANK but the ____________BLANK.

atoms retain their identities; arrangement of bonds changes

When chemical reactions occur the _____________BLANK but the _____________BLANK.

pairing of atoms that share electron pairs changes; individual atomic nuclei stay the same

When CO2 and H2O react to form H2CO3, the number of bonds broken in H2O is____BLANK and in CO2 is _____BLANK.

one; one

The carbon atom in CO2 shares _______BLANK electron pairs. After the reaction with H2O to form H2CO3 is completed, the carbon atom shares ________BLANK electron pairs.

four; four

When H2CO3 reacts to form CO2 and H2O, what is the net change in the number of shared electron pairs?

zero

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 transition state is that portion of the progress of a chemical reaction with a large amount of energy found in ___________BLANK reactions.

both endergonic and exergonic

In the figure above, the solid blue curve plots free energy of a reaction against progress of that reaction. This reaction is:

endergonic

Which labeled arrow in the figure above represents the activation energy (EA)?

arrow b

Which labeled arrow in the figure above represents the change in free energy of the reaction (ΔG)?

arrow e

If you added an enzyme that catalyzes the reaction shown in the figure above, you would predict that ____BLANK would be reduced but ____BLANK would remain the same.

arrow b; arrow e

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.

The reaction of iron with oxygen to form iron oxide is an example of an oxidation-reduction reaction: 4Fe + 3O2 → 2Fe2O3. In this reaction ______BLANK loses electrons and is _________BLANK.

Fe; oxidized

The reaction of iron with oxygen to form iron oxide is an example of an oxidation-reduction reaction: 4Fe + 3O2 → 2Fe2O3. In this reaction ______BLANK gains electrons and is _________BLANK.

O2; reduced