Bio exam 2

A reaction has a ΔG of +20 kJ/mol. If this reaction is coupled to ATP -> ADP (ΔG = -57 kJ/mol), what is the ΔG of the coupled reaction?

-37 kJ/mol

Which of the graphs best represents the effect of temperature on membrane fluidity?

As temp increases, membrane fluidity increases

Consider the reaction M + NADH + H+ --> O + NAD+. What type of pathway likely uses this reaction and why?

A anabolic pathway because conversion of M to O is coupled to NAD+ production from NADH.

Two molecules are shown below. Which of them is able to pass more electrons to O2 and thus will release more energy when reacting with O2 and why?

A because it contains more C-H bonds than molecule B

Which statement about ∆G is correct?

A catabolic reaction typically has a negative ∆G

Which feature is shared by both chloroplasts and mitochondria?

A proton gradient is coupled to ATP synthesis.

Which of the following processes would release energy?

A reaction with a negative ΔG

In the reaction ADP + Pi → ATP + H2O :

ADP is phosphorylated and the reaction is energetically unfavorable

Most of the triose phosphate produced by the Calvin cycle is used to regenerate RuBP, which is the first reactant in the cycle. What output of the light reactions is directly required for the regeneration steps?

ATP

Based on the metabolic pathways in the figure, glucose can be converted to ethanol in the modified Caldi bacteria. From which macromolecule in switchgrass can the bacteria obtain glucose?

Cellulose

Which of the reactions below is unfavorable and would need to be coupled with the reaction ATP -> ADP?

Glucose -> polysaccharide

Which of the following best matches the order of events in cellular respiration, starting from glucose:

Glycolysis → Pyruvate oxidation → Citric acid cycle → Electron transport chain & oxidative phosphorylation

Which organelle receives proteins from the endoplasmic reticulum and glycosylates them before sorting the proteins to other organelles?

Golgi apparatus

The oxygen that enters cellular respiration is incorporated into:

H2O

What is the ultimate source of electrons for photosynthesis in plants?

H2O

Which of the following would allow an energetically unfavorable process to occur in the cell?

If the unfavorable process were coupled to a process that releases sufficient energy

In prokaryotic cells, transcription and translation take place:

In the cytoplasm

In plant cells, the enzyme Rubisco is located:

In the stroma of the chloroplast

Examine the following schematic of a metabolic pathway, in which A, B, C, and D represent molecules in these reactions. If the reaction B -> C is unfavorable under specific conditions in the cell, which of the following could make B -> C more favorable?

Increase the concentration of B.

Which of the following is facilitated diffusion?

Ions cross a membrane through a transporter to an area of lower concentration

At low temperatures, how does cholesterol influence the fluidity of a membrane and why does it have this influence?

It increases fluidity by preventing tight packing of the phospholipid fatty acid tails.

The following reaction occurs in muscle cells under specific circumstances: Pyruvate + NADH + H+ --> Lactate + NAD+ If the ΔG of the forward reaction is negative under these circumstances, this means that:

Over time, pyruvate is converted to lactate

Photosynthesis in plants involves:

Oxidation of H2O in the photosynthetic electron transport chain and reduction of CO2 in the Calvin Cycle

In the reaction to convert substrate S to product P, if the reaction is energetically favorable:

P has less energy than S, because some energy was released in the reaction

Under standard cellular conditions, which statement is correct for the reaction S2 -> P2 that is coupled to NADPH --> NADP+ ?

P2 has higher free energy

The enzyme that catalyzes the reaction shown should have what properties at its active site? glutamic acid + ATP

Positive charges, since both glutamic acid and ATP are negatively charged at the pH of the cell.

Mammalian cells typically have high intracellular concentrations of K+ as compared to the extracellular space. The ΔG of K+ movement into the cell due to the concentration gradient alone is:

Positive, because it is energetically unfavorable for K+ to enter the cell.

Which of the following types of membrane transport is NOT dependent on a concentration gradient?

Primary active transport

Which of the following uses ATP?

Primary active transport

If the glycosylation function of the Golgi were disrupted, which of the following could be observed?

Proteins on the cell surface would not have the correct sugars attached

As electrons pass through Complex I - Complex IV of the mitochondrial electron transport chain,

Protons accumulate in the intermembrane space

Which of the following is often true of the active sites of enzymes?

They can bind to and position substrates in a way that encourages a chemical reaction

Which of the following is true of membrane lipids?

They have both polar and non-polar regions

Which of the following about membrane lipids is always true?

They have both polar and nonpolar regions

The movement of protons across a cell membrane against the proton concentration gradient is an example of:

active transport

The triose phosphate produced by photosynthesis can be used to form macromolecules needed by the plant to grow. The formation of macromolecules from triose phosphate is likely _____ and would be coupled to _______.

anabolic; ATP -> ADP

Based on the model of matter and energy transformations in Figure 3 of the ICA, which product of pyruvate oxidation in bacteria could be used by the Calvin cycle in plants?

carbon dioxide

What are the net inputs to glycolysis?

glucose, ADP + Pi, NAD+

Review your models of matter and energy transformations from PCA Cellular Respiration and PCA Photosynthesis. Which molecule, made by the light reactions in plants, could be used by cellular respiration in some bacteria?

oxygen

A proton gradient established across the thylakoid membrane is necessary to:

provide the energy for the reaction ADP + Pi → ATP.

Which of the following cellular respiration stages releases carbon dioxide?

pyruvate oxidation and the citric acid cycle

When oxygen is present, which pair of processes allow conversion of NAD+ to NADH and then back to NAD+?

pyruvate oxidation and the electron transport chain

The conversion of NAD+ to NADH is energetically ______________, so in a chemical reaction, NAD+ has _______ free energy than NADH.

unfavorable; less

In photosynthesis, the movement of protons from the stroma to the thylakoid lumen is _______ and is coupled to ________.

unfavorable; the movement of energized electrons from PSII to PSI

For the cell in the diagram below ΔGout = -17.1 kJ/mol. If the solute concentration inside the cell were to increase, how would the ΔGout be affected? inside=.7M outside=0.0007M

ΔGout would become more favorable

Consider the model of the mitochondrial electron transport chain. If a chemical were added to mitochondria that allows protons to freely cross the inner mitochondrial membrane, predict what would happen to ATP production by oxidative phosphorylation. Would ATP production increase, decrease, or not change as a result?

ATP is produced by combining ADP and phosphate by ATP Synthase in the mitochondrial matrix. The production of ATP is unfavorable and is normally coupled to the favorable movement of protons from the intermembrane space into the matrix (from high H+ concentration to low), through ATP synthase. If the chemical allows protons to freely cross the membrane, the proton concentration gradient across the membrane decreases, and the movement of protons through ATP synthase becomes less favorable. ATP production by oxidative phosphorylation would decrease, because ATP synthesis depends on the favorable movement of protons through ATP synthase, and the chemical would reduce the proton electrochemical gradient and make proton movement through ATP synthase less favorable.

Some unfavorable reactions are coupled to a reaction that uses ATP. Which of the following accurately describes how ATP is used in a coupled reaction?

ATP is used to make an activated intermediate, and the activated intermediate is used to make the final product

Refer to the data in Table 1 and the metabolic pathway in Figure 2 (from ICA Model of energy and matter transformations). How would adding the gene for enzyme 2 to strain C impact ethanol production? Finally, write a linking statement that states the claim and uses since or because to link to the observations and reasoning. Which of the following is an accurate and relevant linking statement that states a claim about enzyme 2 and ethanol production?

Adding enzyme 2 to strain C would decrease the amount of ethanol produced, since both the lactic acid and ethanol pathways use pyruvate and some pyruvate will now be used to make lactic acid

Refer to the data in Table 1 and the metabolic pathway in Figure 2 (from ICA Model of energy and matter transformations). How would adding the gene for enzyme 2 to strain C impact ethanol production? Next, provide relevant reasoning. Which of the following is an accurate and relevant reasoning statement about enzymes and the pathway to support a claim about enzyme 2 and ethanol production in strain C?

Adding enzyme 2 to strain C would increase the amount of lactic acid produced from pyruvate, since enzymes increase the rate of product formation

Why is more ATP produced from the catabolism of 1 gram of fats compared to the amount of ATP produced from catabolism of 1 gram of sugars?

Because fats have more C-H bonds that allow more NADH to be produced

The image shows a protein embedded in a membrane. Which of the following statements would typically be true about the amino acids in the indicated locations and why?

Because the cytoplasm is hydrophilic, the amino acids at location D would typically be hydrophilic.

Why is the enzyme adhE required in Caldi cells to produce ethanol?

Because without this enzyme, the activation energy to convert substrates to the ethanol product would be too high

glutamic acid + atp phosphoralated glutamic acid + ammonia

Both reactions are energetically favorable

Some amino acid portions of proteins are embedded in a membrane, as shown by the red bracket in the image. Which of the following amino acids is most likely to be found in this sequence and interacting with the fatty acid tails of membrane lipids?

CH3

In the Calvin cycle:

CO2 is the input and triose phosphates are produced

In pyruvate oxidation:

CO2, NADH and Acetyl-CoA are produced

Which statement is correct about anabolism?

Coupling to favorable reactions is required

Based on figures 3 and 4 in your model of Matter and Energy Transformation from class, what happens energetically when glucose is converted to pyruvate?

Free energy is released and some of this is captured by coupled reactions that produce ATP and NADH.

The summary equation for cellular respiration is: C6H12O6 + O2 --> CO2 + H2O. Select all stages of cellular respiration that have O2 as a direct input.

Electron transport

In eukaryotic cells, which process occurs on the mitochondrial inner membrane?

Electron transport chain

In respiration, most of the ATP molecules are generated at which step?

Electron transport chain and oxidative phosphorylation

This graph shows a reaction coordinate diagram of a reaction catalyzed by the original enzyme (solid line) and the same reaction catalyzed by the enzyme with a mutation in the gene encoding the enzyme (dashed line). Free energy on the Y axis refers to the free energy of molecules in the reaction. The left side of the X axis represents molecules at the start of the reaction (substrates), and the right side represents molecules after the reaction (products).

Evidence: The enzyme after the mutation has a lower peak than the original enzyme. Reasoning: Enzymes lower the activation energy and speed up the reaction due to their interactions with substrate molecules (for example, binding to and aligning substrate molecules so they are positioned to react). The mutant enzyme shows a lower energy peak than the original enzyme, indicating a faster reaction rate for the mutant. The mutant enzyme decreases the activation energy more than the original enzyme, perhaps by having a structure that can better interact with substrate molecules and position them so they can react. Linking: The mutation causes the reaction to proceed more quickly, because the mutant enzyme lowers the activation energy to a greater degree than the original enzyme and more molecules have sufficient energy to react.

Which product of the light reactions is used by the mitochondrial electron transport chain?

O2

The image shows a cell with the indicated concentrations of Na+ inside and outside of the cell. What transport process likely occurs to bring Na+ into the cell? (assume the appropriate proteins are present if needed) inside= 10mM Na+ outside=140mM Na+

Facilitated diffusion, because molecules are moving with their concentration gradient and require a protein.

The only inputs for cellulose hydrolysis are water and cellulose. Based on figures 3 and 4 in your model of Matter and Energy Transformation from class, what happens energetically when cellulose is hydrolyzed to glucose?

Free energy is lost as heat.

The reaction below is catalyzed by lactate dehydrogenase. When lactate is used to produce pyruvate, how is the energy released in this reaction captured?

It is directly coupled to NADH production.

In pyruvate oxidation, a three-carbon pyruvate molecule is converted to a two-carbon acetyl group. What happened to the other carbon molecule?

It was released as CO2.

A cell with the indicated concentration of K+ and aquaporin proteins only (assume no other types of membrane proteins are present) is placed into fluid with the indicated concentration of K+. What will likely happen and why? inside=150mM K+ outside=10mM K+

K+ cannot cross the membrane, but water enters the cell, with its concentration gradient, through the aquaporin.

Which of the following is NOT a feature of prokaryotic cells?

Mitochondria

Which of the following is not part of the endomembrane system?

Mitochondria

Based on their structures, which of the molecules below will more efficiently cross a lipid bilayer with no proteins and why?

Molecule A, because it contains mostly nonpolar covalent bonds

Comparing cellular respiration and lactic acid fermentation, which statement is correct?

More ATP is produced during cellular respiration

Which of the following could represent an unfavorable part of a coupled reaction?

NAD+ → NADH

Which of the following provides electrons to the electron transport chain?

NADH

What is the final electron acceptor of the photosynthetic electron transport chain?

NADP+

Review this formula for estimating the ΔG for solute movement into a cell from ICA Bioenergetics and enzymes: If an uncharged solute molecule has a concentration of 50 mM outside of the cell and 5 mM inside the cell, the ΔG for solute movement into the cell is:

Negative, because it is energetically favorable for the solute to enter the cell and the natural log of a value less than 1 is negative.

A chemical reaction has a ΔG of +57 kJ/mol. The reaction ATP -> ADP + Pi under cellular conditions releases 57 kJ/mol. Could these reactions be successfully coupled in the cell?

No, because the overall ΔG would be zero and for the reaction to proceed, the ΔG needs to be negative.

Refer to the data in Table 1 and the metabolic pathway in Figure 2 (from ICA Model of energy and matter transformations). How would adding the gene for enzyme 2 to strain C impact ethanol production? First, provide an observation relevant to ethanol production and the enzymes in strain C. Which of the following is a specific and relevant observation of the pathway that could be used to support a claim about enzyme 2 and ethanol production in strain C?

Pyruvate can be converted into lactic acid by Enzyme 2, or it can be converted to acetyl Co-A and then ethanol.

Which of the following are net products of glycolysis?

Pyruvate, NADH and ATP

Review carefully the structure of ATP. In addition to being the "energy currency" for the cell, ATP is a monomer for which macromolecule?

RNA

An enzyme catalyzes a reaction by:

Reducing the activation energy for the reaction

The image shows a cell that is moving a solute in the direction indicated by the arrow. This movement:

Requires coupling to a favorable process because there is no concentration gradient, so the movement is unfavorable

Which is the central enzyme involved in the Calvin Cycle that catalyzes carbon fixation (and is the most abundant protein on earth)?

Rubisco

Refer to the data in Table 1 and the metabolic pathway in Figure 2 (from ICA Model of energy and matter transformations). Based on this information, what is the difference in ethanol production between strain B and strain C and why does this difference exist?

Strain C produces more ethanol because a gene encoding an enzyme that catalyzes ethanol production was added to create strain C.

The plant cell has the indicated proteins to import sugars into the cell. If a chemical were added that blocked the function of the proton pump:

Sugar import would decrease, because the proton gradient required for sugar import would decrease

Which of the following processes in a plant cell could produce the CO2 needed for the Calvin cycle?

The citric acid cycle

Examine the following schematic of a metabolic pathway, in which A, B, C, and D represent molecules in these reactions. As the reaction B -> C occurs, product C accumulates and makes the reaction B -> C unfavorable. Based on the schematic, which of the following would keep B -> C favorable?

The conversion of C to D, because this decreases the concentration of C

Consider the reaction: NAD(P)H + BPG --> G3P + NAD(P)+ + Pi. In chloroplasts, the reaction proceeds in the direction written (from left to right), while in the cytosol, it proceeds in the opposite direction (from right to left). What likely allows this to happen?

The different compartments have different concentrations of the substrates and products.

The graph from ICA Bioenergetics and enzymes shows the effect of an enzyme on the activation energy for a reaction. How does this illustrate the effect on reaction rate due to the enzyme?

The enzyme decreases the energy barrier for the reaction to occur, so more molecules have sufficient energy to react and the reaction rate is increased.

Consider the reaction M + NADH + H+ --> O + NAD+. Which statement accurately describes the energetic coupling in this pathway?

The favorable conversion of NADH to NAD+ is coupled to the unfavorable conversion of M to O.

The image shows an animal cell with typical Na+ and K+ concentrations and a Na+/K+ ATPase protein. How does the ATPase protein function?

The favorable process of ATP -> ADP is used to drive the unfavorable movement of Na+ out of the cell and K+ into the cell

In exergonic reactions:

The free energy of the products is lower than the the free energy of the reactants and ΔG is negative.

What would happen to the light reactions if the Calvin cycle stopped converting NADPH to NADP+?

The light reactions would stop because NADP+ is needed to accept electrons from the light reactions.

In the mitochondria, the concentration of protons (H+) is higher in the intermembrane space than in the matrix. Given this information, which of the following statements is true?

The movement of H+ into the matrix is energetically favorable

How does increasing temperature affect the reaction rate?

The reaction rate is increased, as more molecules have sufficient energy to react.

Which of the following processes is considered energetically unfavorable?

The synthesis of cellulose

According to the first law of thermodynamics:

The total energy before and after a reaction is the same

The figure shows a model of a cell with a specific molecule at the indicated concentrations outside and inside of the cell. Transport proteins are NOT shown, but assume they are there if needed and refer to them in your response. What specific form of membrane transport is likely used to bring this molecule into the cell? (Specific forms include: facilitated diffusion, osmosis, primary active transport, secondary active transport, and simple diffusion).

This molecule is polar due to the many hydroxyl groups in its structure and is at a higher concentration outside versus inside of the cell. The movement of the molecule into the cell is from high concentration to low, so this movement is energetically favorable (has a negative ΔG). Because the membrane contains hydrophobic fatty acid tails, molecules that are polar require a protein to cross the membrane, such as a carrier protein (a passive transport protein). This molecule enters the cell through facilitated diffusion, because this molecule is polar and moving in the direction of negative ΔG.

If a chemical reaction has a ΔG of -10 kJ/mol, which of the following is true?

This reaction releases energy to the surroundings.

Which of the following statements is true for the reaction below: C6H12O6+6O2 → 6 CO2 + 6 H2O

This reaction represents a catabolic pathway

Which of the following is an end product of the Calvin cycle in photosynthesis?

Triose phosphate

ATP and NADPH produced during the photosynthetic electron transport are:

Used as substrates for the Calvin Cycle

Which of the following is true of osmosis?

Water molecules cross a membrane to areas of higher solute concentration

In eukaryotic cells, the reactions of glycolysis occur in the:

cytoplasm

When no oxygen is present, which pair of processes allow conversion of NAD+ to NADH and then back to NAD+?

glycolysis and fermentation

The organization of phospholipids in a lipid bilayer is driven by:

hydrophobic clustering

Which organelle has an acidic pH and breaks down macromolecules into monomers?

lysosome

Which of the following is a feature of eukaryotic but not prokaryotic cells?

membrane-enclosed organelles

In eukaryotic cells, which organelle produces the majority of the ATP for the cell?

mitochondria

If ΔG is positive (ΔG>0), the reaction is:

non-spontaneous and endergonic

Conversion of G3P to RuBP ______ energy and it is coupled to __________.

requires; conversion of ATP to ADP + Pi

O2 and CO2 can pass through a cell membrane by:

simple diffusion

Which of the following can pass through a lipid bilayer by simple diffusion (in the absence of membrane proteins)?

small non-polar molecules

Compare the model of cellular respiration with the model of fermentation. Which process generates ATP during cellular respiration but not during fermentation?

the citric acid cycle

In secondary active transport, the movement of one molecule from an area of low concentration to an area of high concentration is coupled to:

the movement of another molecule from high concentration to low

Which of the following is true about the energetics of the reactions of photosynthesis?

the oxidation of water and chlorophyll is energetically unfavorable

The movement of most water molecules across cell membranes occurs:

through aquaporins