BIOL exam 2

Why do the functions of many receptor kinases depend on the fluid nature of the plasma membrane?

The receptor monomers must move together and dimerize to be activated.

Suppose a plant is exposed to a toxin that causes the thylakoid membranes to become much more permeable to protons than normal. Which of the following would be true?

The reduction and regeneration steps of the Calvin cycle would slow down and eventually stop.

How would signaling be affected if a mutation caused a G protein to replace GDP with GTP on its own without needing to be activated by the G protein-coupled receptor?

The signaling pathway would be activated even when no ligand was present.

A number of mutations have been described in the G protein Ras that have profound effects on its activity. For example, some mutations greatly increase the affinity of the G protein for GDP, making it very difficult for GDP to be exchanged for GTP. Other mutations prevent the GTPase activity of Ras, preventing it from causing the hydrolysis of GTP to GDP. Which of the scenarios would result in a persisting proliferation response to growth factor receptor activation after the ligand is no longer binding to its receptor kinase? ->a mutation that blocks the GTPase activity of Ras ->a mutation that blocks the exchange of GDP with GTP ->Neither a mutation that blocks the GTPase activity of Ras nor a mutation that blocks the exchange of GDP with GTP would cause the response to persist. ->Both a mutation that blocks the GTPase activity of Ras and a mutation that blocks the exchange of GDP with GTP would cause the response to persist.

a mutation that blocks the GTPase activity of Ras

In the cleavage phase of glycolysis:

a phosphorylated sugar molecule is broken apart and the products rearranged.

From its ground state, photosystem II can:

absorb light energy

How did the earliest organisms on Earth most likely produce ATP? Please choose the correct answer from the following choices, and then select the submit answer button.

glycolysis

Based on what you know of ATP's chemistry, which of the substances is most likely to have similar functions in energy-management processes? ->potassium ions (K+) ->phospholipids ->guanosine nucleotide triphosphate ->steroids ->lysine (amino acid)

guanosine nucleotide triphosphate

Suppose that three critical amino acids in the active site of a specific enzyme are arginine, lysine, and histidine. Which of the characteristics would you predict the substrate to possess, in order to bind the active site of this enzyme?

hydrophilic with a negative charge

In the Calvin cycle, NADPH is:

oxidized

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

oxidized, reduced

A simplified overall equation for respiration is as follows: C6H12O6 + 6O2 →6CO2+ 6H2O + energy In this reaction, we can say that _____ is reduced and _____ is oxidized.

oxygen, glucose

Platelet-derived growth factor (PDGF) is a signaling molecule released by platelets at wound sites to cause nearby fibroblasts to divide and contribute to wound healing. Which type of cell signaling best describes PDGF signaling?

paracrine signaling

In the Calvin cycle, ATP is required to:

phosphorylate 3-PGA

The Z scheme is a model for the interpretation of:

the changes in the energy level of electrons as they pass through the photosynthetic electron transport chain.

Of the 6 carbons in a starting molecule of glucose, at the completion of pyruvate oxidation, _____ carbons are fully oxidized to _____, while _____ carbons remain in _____.

two; CO2; four; acetyl groups

Which of the following is a product (as opposed to a substrate) of at least one of the processes of cellular respiration?

water

Photosystem I is a _____ than photosystem II.

weaker oxidant and a stronger reductant

For every six CO2 molecules incorporated into carbohydrate molecules, how many triose phosphates can be exported from the chloroplast?

2

which of the answer choices is responsible for amplifying the signal in a cell responding to adrenaline? ->One molecule of protein kinase A (PKA) can phosphorylate and activate many target proteins. ->One activated receptor can activate many G proteins. ->One molecule of adenylyl cyclase can activate many molecules of protein kinase A (PKA). ->One adrenaline molecule binds to change the conformation of the receptor protein.

->One molecule of protein kinase A (PKA) can phosphorylate and activate many target proteins. ->One activated receptor can activate many G proteins. ->One molecule of adenylyl cyclase can activate many molecules of protein kinase A (PKA).

Which of the statements are true? Select all that apply. ->The amount of usable energy resulting from a reaction is always less than the total energy available at the start of the reaction. ->The entropy of the products of a reaction is always greater than the entropy at the start of the reaction. ->The energy for a reaction equals the sum of the energy in the product plus energy released as heat and disorder. ->The entropy at the start of a reaction is always greater than the entropy of the products.

->The amount of usable energy resulting from a reaction is always less than the total energy available at the start of the reaction. ->The energy for a reaction equals the sum of the energy in the product plus energy released as heat and disorder.

Which of the statements represent the laws of thermodynamics? Select all that apply. ->Enzymes lower the activation energy requirement of reactions. ->Matter cycles in the biosphere, but energy flows. ->The energy available to do work decreases as energy is transformed from one form to another. ->All cells arise from pre-existing cells. ->The amount of energy in the universe is constant.

->The energy available to do work decreases as energy is transformed from one form to another. ->The amount of energy in the universe is constant

What are the functions of an enzyme? Select all that apply. ->to lower the activation energy for the reaction ->to allow a reaction to be reversible ->to alter the equilibrium of a specific reaction ->to alter the ΔG of a specific reaction ->to increase the rate of a specific reaction

->to lower the activation energy for the reaction ->to increase the rate of a specific reaction

Tracing the metabolism of one glucose molecule, how many carbon atoms are available for further oxidation at the completion of the pyruvate oxidation stage?

4

Tracing the metabolism of one glucose molecule, how many carbon atoms are fully oxidized to CO2 at the completion of aerobic respiration?

6

Which of the following is required for the preparatory phase of glycolysis and then produced during the payoff phase? Please choose the correct answer from the following choices, and then select the submit answer button.

ATP

Which of the following are produced directly as a result of the movement of electrons through the photosynthetic electron transport chain?

ATP and NADH

In photosynthesis, the reduction of 3-phosphoglycerate to form carbohydrate requires:

ATP and NADPH

Which statement is true about the Delta protein? ->Delta directs adjacent cells to differentiate into glial cells. ->Delta is produced by embryonic stem cells as they differentiate into neurons in the brain. ->Delta directly signals to a Notch transmembrane protein in adjacent cells.

All of the above

Xanthophyll pigments: ->absorb light energy. ->reflect yellow light. ->convert light energy into heat. ->prevent formation of reactive oxygen species. ->all of the above

All of the answer options are correct.

Of the choices, which can be a product of a catabolic reaction? ->a lipid like cholesterol ->an amino acid like tryptophan ->a complex carbohydrate like cellulose ->a motor protein like myosin ->a nucleic acid like RNA

An amino acid like tryptophan

What is an example of potential energy? ->a moving muscle ->heat ->wind ->an electrochemical gradient ->light

An electrochemical gradient

Nicotine from cigarette smoke acts as a ligand and associates with the acetylcholine receptor on specific cells in the nervous system. Nicotine eventually produces feelings of pleasure and well-being. The listed statements are descriptions of the events that happen in the cellular response to nicotine. Place the events in the correct order to describe the steps in the signaling pathway. A) The acetylcholine receptor is an ion channel, and when a ligand binds, the ion channel opens. B) An influx of ions carries the signal to the reward areas of the brain. C) Nicotine binds to the transmembrane protein that normally binds the neurotransmitter acetylcholine. D) The signal causes release of dopamine in the brain, which causes good feelings. E) Nicotine is quickly eliminated from the body (causing cravings for more cigarettes to produce good feelings).

C,A,B,D,E

Which of the following is/are rubisco substrates?

CO2, O2, and RuBP

what is a key difference between cell signaling by a cell-surface receptor and cell signaling by an intracellular receptor?

Cell-surface receptors bind polar signaling molecules; intracellular receptors bind nonpolar signaling molecules.

Pyruvate oxidation produces a large amount of ATP through substrate-level phosphorylation.

False

Kohler and Lipton first discovered platelet-derived growth factor (PDGF) by observing that fibroblasts: ->grew at the same rate in cell culture containing either blood plasma or serum. ->grew better in cell culture blood plasma without the proteins released by platelets. ->grew better in cell culture containing blood serum containing proteins released by platelets during clotting.

Grew better in cell culture containing blood serum containing proteins released by platelets during clotting.

To which of the substances is ATP most closely chemically related? ->tryptophan ->guanine ->glucose ->phospholipid ->testosterone

Guanine

Which type of receptor is involved in rapid responses of muscle cells and neurons?

Ligand-gated ion channels

In addition to chloroplasts, which organelle of eukaryotic cells is believed to have originated by endosymbiosis?

Mitochondria

Which statement is true regarding pyruvate and glucose? ->Pyruvate can be transported across both membranes of the mitochondrion to be further metabolized, but glucose cannot. ->Both glucose and pyruvate can feed directly into the citric acid cycle, although acetyl-CoA is the preferred reactant for this process. ->Glucose and pyruvate are remarkably similar in structure, with both molecules possessing a ring shape. ->Glucose easily passes in and out of mitochondria and can often be found in the mitochondrial matrix, but pyruvate cannot. ->Pyruvate is typically "trapped" in the intermembrane space of mitochondria, where it is oxidized to form acetyl-CoA.

Pyruvate can be transported across both membranes of the mitochondrion to be further metabolized, but glucose cannot.

Which statement is true regarding pyruvate oxidation? ->Like glycolysis, pyruvate oxidation is carried out in the mitochondria. ->Pyruvate oxidation ends with the oxidation of an acetyl group, which forms CO2. ->Pyruvate oxidation forms the same number of NADH (per glucose molecule) as glycolysis. ->Pyruvate oxidation directly follows the citric acid cycle during cellular respiration.

Pyruvate oxidation forms the same number of NADH (per glucose molecule) as glycolysis.

Which compound is required for the carboxylation step of the Calvin cycle?

RuBP

The regeneration of RuBP typically limits the rate of photosynthesis under low light intensities. This is because:

RuBP regeneration requires ATP.

The Calvin cycle includes 15 enzymes, most of which are involved in:

RuBP regeneration.

Of the answer choices, what is the most likely reason that paracrine signaling does not activate the cell that is producing the signaling molecule? ->The concentration of the signaling molecule is not high enough. ->The neighboring cells are too far away. ->The cell does not have the proper receptor. ->The cell's receptors have a mutation.

The cell does not have the proper receptor.

A biologist working in a lab adds a compound to a solution that contains an enzyme and substrate. This particular compound binds reversibly to the enzyme at the active site. Once the compound is bound to the enzyme, the catalysis of substrate to product stops. Which of the statements is true of the compound?

The effect of the compound can be overcome by adding more substrate.

A researcher is carrying out an experiment where she labels a protein with a fluorescent tag (so she can visualize its location in a cell) and introduces this tagged protein into the lumen of a single thylakoid. She observes her treated cells periodically and notices that the labeled protein can move between grana and is always in the lumen, but is never observed in the stroma. What can she deduce?

The protein likely travels through a common lumen shared by thylakoid membranes and grana, and cannot easily diffuse through the thylakoid membrane.

researcher is carrying out an experiment where she labels a protein with a fluorescent tag (so she can visualize its location in a cell) and introduces this tagged protein into the lumen of a single thylakoid. She observes her treated cells periodically and notices that the labeled protein can move between grana and is always in the lumen, but is never observed in the stroma. What can she deduce?

The protein likely travels through a common lumen shared by thylakoid membranes and grana, and cannot easily diffuse through the thylakoid membrane.

You strip off all proteins on the cell surface by using a protease (an enzyme that destroys proteins). Now, when you add a specific signaling molecule, the cell still responds. What is the most reasonable explanation of this?

The receptor for this signal is inside the cell, and the signaling molecule is nonpolar and can diffuse into the cell.

Which of these best describes the benefit to early photosynthetic organisms gained by having two different photosystems in one cell?

They can use water as an electron donor

Which of the following is true when comparing the Calvin cycle and light-harvesting reactions of photosynthesis?

They take place in different compartments of the same organelle.

Rubisco can function as either a carboxylase or an oxygenase.

True

Vascular endothelial growth factor (abbreviated VEGF and pronounced "Veg-F") is a peptide signaling molecule related to platelet-derived growth factor. VEGF is important in the formation of the circulatory system because its signaling pathway causes the formation of blood vessels in developing embryos during normal development. Tumors also produce and secrete VEGF, causing nearby blood vessels to branch and grow to form new blood vessels that supply these tumors. Given what you know about the different kinds of cell signaling and VEGF, which statement is true? ->VEGF is an endocrine-signaling molecule because it circulates through the bloodstream inside of platelets. ->VEGF is a paracrine signaling molecule because it binds to receptors on nearby cells, at the site where new blood vessels are needed. ->VEGF is an endocrine-signaling molecule because it is released from platelets into the bloodstream and is carried throughout the body, causing widespread activation of platelet-derived growth factor receptors on cells in a variety of tissues.

VEGF is a paracrine signaling molecule because it binds to receptors on nearby cells, at the site where new blood vessels are needed.

Which of the following is part of the photosynthetic electron transport chain between photosystems I and II? ->plastocyanint. ->plastoquinone ->cytochrome-b6f complex

all of the above

Which type of cellular activities can be a response to cell signaling? ->Enzyme activities are changed. ->Gene expression patterns are changed. ->Cell signals are released to communicate with other cells. ->Cell division is triggered.

all of the above

Assuming that all is working properly in photosynthesis, which of the following is at a higher energy level?

an excited-state antenna chlorophyll molecule

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.

anabolic pathway.

Glycolysis is:

anaerobic

Which of these correctly lists the three phases of the Calvin cycle?

carboxylation, reduction, and regeneration

correctly lists the three phases of the Calvin cycle

carboxylation, reduction, and regeneration

Imagine that you discover a microbial deep-sea organism that can derive energy from (inorganic) hydrogen gas (H2). In addition, this microbe can synthesize organic compounds from carbon-containing inorganic molecules in the ocean. This microbe is a:

chemoautotroph

Animals such as cats, worms, and butterflies are classified as:

chemoheterotrophs

The organisms believed to be the first to use two different photosystems in a single photosynthetic electron transport chain are the:

cyanobacteria

Which of these is responsible for the transport of electrons between photosystem II and photosystem I?

cytochrome b6f

Chemicals called uncouplers can make membranes permeable to small molecules and ions. What effect might uncouplers have on photosynthesis?

decreased ATP production because the proton gradient would decrease

How does the metabolism occurring in chloroplasts differ from that of mitochondria?

different electron acceptors and electron sources

During what phase of glycolysis is NADH formed?

during phase 3, when glyceraldehyde 3-phosphate is phosphorylated

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

endergonic

The process in which one cell takes up residence in another cell is called:

endosymbiosis

Antennae work with reaction centers by providing:

energy transfer

Cyclic electron transport enhances ATP production because:

excited electrons are transferred from PS I back to plastoquinone.

The Calvin cycle is a relatively constant process, the rate of which is independent of factors such as temperature and nitrogen concentration.

false

In cellular respiration, oxygen:

gains electrons and is reduced

Which of the following are inputs, but not outputs, of glycolysis?

glucose

In addition to chlorophylls, light-harvesting antennae include other pigments. What is the benefit of these additional pigments?

increased range of wavelengths absorbed

ATP is a good energy currency for cells because it has a(n) _____ amount of Gibbs free energy.

intermediate

During pyruvate oxidation, pyruvate is broken down into CO2 and an acetyl group. The CO2 is (more/less) energetic than the acetyl group

less

ATP production in photosynthesis requires:

light, electrons, and protons

NADPH production in photosynthesis requires:

light, electrons, and protons

NADPH production in photosynthesis requires: Please choose the correct answer from the following choices, and then select the submit answer button.

light, electrons, and protons.

The chemical bonds of carbohydrates and lipids have high potential energy because:

many of these bonds are C—C and C—H bonds, in which electrons are shared equally between atoms.

Reactive oxygen species are detoxified in order to:

minimize damage to membranes

Many photosynthetic prokaryotes are capable of cyclic electron transport only. It is likely that such organisms can _____ but not _____.

produce ATP; reduce CO2

Organisms with only one photosystem cannot:

produce O2

The occurrence of photorespiration _____ CO2 and _____ ATP.

produces, consumes

phosphate groups play a key role in receptor kinase activation by:

providing binding sites to recruit and activate signal-transduction proteins.

A protein on a cell surface that binds to a signaling molecule is an example of which element of cellular communication?

receptor protein

Which step of the Calvin cycle would be affected first by a lack of NADPH?

reduction

Reactions in which there is a negative change in free energy (-ΔG) are: ->spontaneous and endergonic. ->nonspontaneous and exergonic. ->nonspontaneous and endergonic. ->spontaneous and exergonic.

spontaneous and exergonic

In glycolysis, ATP is synthesized by:

substrate-level phosphorylation

Photorespiration occurs because:

there is more O2 than CO2 in the atmosphere.

Chloroplast ATP synthases are powered by the flow of protons from the:

thylakoid lumen to the stroma.

In addition to destabilizing glucose for subsequent breakdown, what else does phosphorylation of glucose do? Please choose the correct answer from the following choices, and then select the submit answer button.

traps glucose inside the cell