Biology Non Science majors Exam 2

Identify the blanks in the figure. Activation energy question 5.

1. reactants; 2. Ea; 3. energy profit This answer correctly identifies the blanks: 1. the reactants; 2. activation energy or Ea; 3. energy profit or ΔG.

If a reaction occurs at 0 degrees Kelvin and the total energy is 1000 Joules, what is the free energy?

1000 Joules H = 1000 Joules and T = 0 K.Substitute into G = H − TS and you get G = 1000 Joules − (0)S or G = 1000 Joules.

In the Calvin cycle, _______ ATP's and ________ NADPH's are required for a net output of two molecules of glyceraldehyde 3-phosphate.

18; 12 In the Calvin cycle, eighteen ATP's and twelve NADPH's are required for a net output of two molecules of glyceraldehyde 3-phosphate. Every three rounds of the Calvin cycle consumes nine ATP's and six NADPH's and produces one glyceraldehyde 3-phosphate.

The six-carbon molecule that results from carbon fixation in the Calvin cycle immediately breaks down into

3-phosphoglycerate 3-phosphoglycerate results from the breakdown of the 6-carbon molecule that forms from carbon fixation.

Visible light ranges between

380 to 750 nm.

In the regeneration phase of the Calvin cycle 10 glyceraldehyde 3-phosphates will be regenerated into __________ RuBP.

6 Because glyceraldehyde 3-phosphate is a three-carbon molecule and RuBP is a five-carbon molecule, it takes five glyceraldehyde 3-phosphates to make three RuBP molecules. Ten glyceraldehyde 3-phosphates would yeild 6 RuBPs in the Calvin cycle.

A photon with a wavelength of __________ is optimal to move an electron from ground state to an excited state in Photosystem I.

700 nm A wavelength of 700 nm is optimal at exciting an electron from Photosystem I. This is why photosystem I is also known as P700.

With respect to the nitrogen atom Redox a brief overview question 4

A is reduction; B is oxidation. A is a reduction, the charge of the resulting molecule has decreased as it gained two electrons and one proton. B is an oxidation, because the charge of the resulting molecule increased as it lost two electrons and one proton.

In redox reactions:

A molecule that reduces another is itself oxidized as it loses electrons. A molecule that reduces another gives up electrons to that other molecule, thus becoming oxidized itself.

Which of the following takes place as a result of photosynthetic electron transport?

A proton gradient is established across the thylakoid membrane. During photosynthetic electron transport, protons are pumped into the lumen of the thylakoid creating a concentration gradient. This concentration gradient is used to fuel the synthesis of ATP. As protons travel down the concentration gradient (from high to low concentration) through ATP synthase, ATP is made.

Sulfuric acid + sugar + KClO3 ⇒

A rapid release of energy in the form of combustion. Combustion is the oxidation of the carbon in the sugar with the associated uncontrolled release of energy.

Which of the following molecules are both produced by reactions in the thylakoids and consumed by reactions in the stroma?

ATP and NADPH ATP and NADPH are both made during the light dependent reactions which take place in the thylakoid. ATP and NADPH are then consumed during the reduction phase of the Calvin cycle, which takes place in the stroma.

Which statement about the Calvin cycle is incorrect?

ATP and NADPH form during the reduction phase ATP and NADPH are hydrolyzed during the reduction phase of photosynthesis.

Which of the following statements regarding ATP is true?

ATP is an energy-carrying molecule. ATP is an energy-carrying molecule. When the high energy phosphate bond is broken, energy is released and can be used to fuel endergonic reactions.

Which statement is true regarding cyclic electron flow in photosynthesis?

ATP is produced without increasing the amount of NADPH. In cyclic electron flow, excited electrons are passed down an electron transport chain and eventually passed back down to chlorophyll a, rather than being used to reduce NAD+. As electrons are passed down the electron transport chain, the energy they lose is used to create a proton gradient, which is used to fuel ATP synthesis. The result of cyclic electron flow is that ATP is produced without increasing NADPH. Cyclic electron flow takes place when NADPH levels get too high.

The end products of the light-dependent reactions of photosynthesis include

ATP, NADPH, and O2 ATP, oxygen, and NADPH are the products of the light-dependent reactions. ATP is made from the ATP synthase complex as protons flow down a concentration gradient. Oxygen is made from the photolysis of water. NADPH is made when the electrons reduce NADP.

_____________ is/are required to begin a reaction.

Activation energy The activation energy is the amount of energy needed to initiate a reaction.

Phosphate group transfers from ATP to other molecules are __________ mechanisms for delivering energy. Phosphorated intermediate question 1

All of the above Phosphate group transfers from ATP are rapid, renewable, and almost universal mechanisms for delivering energy in living organisms.

Which of the following statements regarding allosteric regulation is true?

Allosteric enzymes are often multi-subunit enzymes. Allosteric enzymes tend to be larger multi-subunit enzymes.

How is photosystem II linked to photosystem I?

An electron from photosystem II is passed to photosystem I. Electrons that are excited from photosystem II are passed down an electron transport chain to photosystem I.

Glycolysis is an ________ process in which glucose undergoes _________.

Anaerobic; oxidation Glycolysis is a process that does not require oxygen in order to take place, thus it is anaerobic. In glycolysis, glucose intermediates are oxidized. Oxidation is the removal of electrons from a molecule. In the process of glycolysis, the electrons are removed in the form of hydrogen atoms (each hydrogen atom consists of an electron and a proton).

The most likely candidate for the first photosynthetic organisms are the

Archaea. The most likely candidate for the first photosynthetic organisms are thought to be extreme halophilic, or salt-loving, Archaea.

How are C4 and CAM plants similar?

Both cases employ an enzyme other than rubisco to initially fix carbon. The C4 and CAM pathways a similar in that they initially fix carbon dioxide with enzymes other than rubisco. In the C4 pathway carbon dioxide is fixed by PEP carboxylase to form oxaloacetate. In the CAM pathway, carbon dioxide is fixed to form organic acids.

Choose the best description of the process of cellular respiration.

Carbohydrates are broken down with the consumption of oxygen to produce carbon dioxide, water and energy. In the process of cellular respiration, carbohydrates are broken down and oxygen is consumed, thereby producing carbon dioxide, water, and energy in the form of ATP and heat.

In what way do CAM plants and C4 plants differ?

Carbon fixation is not separated from the Calvin cycle in CAM plants, while it is in C4 plants. Carbon fixation occurs in the mesophyll cells of C4 plants, while the Calvin cycle occurs in bundle-sheath cells. In CAM plants, both of these events occur in the same cells, but at different times.

Which of the following statements regarding pH is correct?

Changing the hydronium ion concentration changes the rate of biological reactions. In biological systems, many reactions have rates that are dependent on the hydronium ion concentration. A change in pH will affect the speed of the reaction.

Which of the following statements regarding chlorophyll is false?

Chlorophyll a has one major absorption peak at approximately 550 nm. Chlorophyll a does not have one major absorption peak at 550 nm., it has two major absorption peaks. One is in the violet region of the spectrum (~400-450 nm) and the other is in the red region of the spectrum (~650-675 nm).

Which statement is not true?

Chlorophyll a is green because it absorbs green wavelengths. Chlorophyll a is green because it reflects green light, not because it absorbs green light.

______________ is/are stored in the bonds of a sugar molecule.

Energy Breaking the bonds of the sugar molecule releases energy that is "stored" in those bonds.

Which of the following curves shows the relationship between temperature and rate of an enzymatic reaction? Enzyme characteristics question 3

Enzymatic activity increases to a maximum and then falls off as temperature continues to increase.

Which statement about enzymes is not true?

Enzymes are nonspecific and one enzyme may catalyze many reactions by reacting with many substrates. Enzymes have specific binding sites and active groups that allow them to catalyze only specific reactions.

Which of the following molecules are not formed during glycolysis?

FADH2 FADH 2 is not formed during glycolysis. FADH2 is formed during the Krebs cycle (also known as the citric acid cycle).

Which of the following does not form during glycolysis?

FADH2 FADH2 is not formed during glycolysis, it is formed during the citric acid cycle.

During two steps in glycolysis, ATP is hydrolyzed in order to form phosphorylated intermediates. Which two enzymes mediate these respective reactions?

Hexokinase; Phosphofructokinase Hexokinase hydrolizes ATP phosphorylating glucose. Phosphofructokinase hydrolizes ATP phosphorylating fructose 6-phosphate.

Which statement regarding fermentation is true?

In alchohol fermentation, pyruvate is first converted to acetaldehyde in a decarboxylation reaction and then converted to ethanol, forming NAD+. In alcohol fermentation pyruvate is converted to ethanol in two steps. The first step releases carbon dioxide from pyruvate, forming acetaldehyde. In the next step NADH reduces acetaldehyde to ethyl alcohol, forming NAD+.

Which statement regarding the isomerase enzyme in the first half of glycolysis is true?

Isomerase interconverts glyceraldehyde-3-phosphate to dihydroxyacetone phosphate, and vice versa. Isomerase catalyzes the reversible interconversion of glyceraldehyde-3-phosphate to dihydroxyacetone phosphate and vise versa. The conversion of dihydroxyacetone phosphate to glyceraldehyde-3-phosphate is favored under conditions in the cell because glyceraldehyde-3-phosphate is consumed by the next reaction in the energy payoff phase of glycolysis.

Which of the following statements is true regarding fermentation?

It produces a NAD+ Fermentation recycles NADH to form NAD+ allowing glycolysis to continue (glycolysis cannot occur unless NAD+ is present).

Which statement about rubisco is true?

It uses carbon dioxide as a substrate. Rubisco (ribulose bisphosphate carboxylase) is an enzyme involved in the Calvin cycle. Rubisco is able to take carbon dioxide and fix it to RuBP. Once carbon dioxide is fixed, the molecule splits to form two 3-phosphoglycerate molecules.

Who found that plants give off oxygen in the presence of light and give off some carbon dioxide in the dark?

Jan Ingenhousz In 1770, Ingenhousz concluded based on many of his experiments, that in the light plants give off oxygen, and in the dark plants give off carbon dioxide.

Chlorophyll contains a porphyrin ring that has a hydrocarbon tail attached.Which of the following atoms is found in the center of the porphyrin ring?

Mg Magnesium is found in the center of the porphyrin ring of both chlorophyll a and chlorophyll b.

In the equation:B + NAD+ → C + NADH + H +the molecule which is reduced is

NAD+ NAD+ receives two electrons and a proton from B and oxidizes it to C. Thus, NAD+ is the molecule which is reduced.

Fermentation enables

NADH + H+ to be oxidized to form NAD+ so that glycolysis will continue. Fermentation enables NADH + H+ to be oxidized to form NAD+ so that glycolysis will continue. NAD+ is necessary in order for glycolysis to take place.

If an enzyme that breaks down carbohydrates is placed in a solution of proteins, what will happen?

Nothing will happen. Enzymes are very specific for their substrate. An enzyme that breaks down carbohydrates will not react with proteins.

NAD+ is a modified _____________.

Nucleotide NAD+ is a modified nucleotide. The D stands for dinucleotide. Nucleotides are made up of a sugar with a nitrogenous base and phosphate groups.

An important principle of fermentation is that

O2 is not used as a final electron acceptor. Fermentation occurs under anaerobic conditions, thus it allows for the breakdown of glucose without using O2 as a final electron acceptor.

Why is it difficult for most plants to carry out photosynthesis during hot, dry conditions?

Oxygen builds up and carbon dioxide levels get too low because of the closing of the stomata. During hot, dry conditions the stomata of most plants close to prevent excessive water loss. The Calvin cycle uses up CO2, which can not be replenished through the closed stomata. Oxygen produced in the light-dependent reactions is not able to leave through the stomata and builds up in the leaf. This slows down photosynthesis because oxygen competes with carbon dioxide in the Calvin cycle. When oxygen enters the Calvin cycle, there is no photosynthetic output.

Which takes place when a C4 plant first fixes carbon dioxide?

PEP carboxylase is required. The enzyme PEP carboxylase is required for the initial fixation of carbon dioxide in the C4 pathway.

Which statement about ATP is not true?

Part of the ATP molecule is a trisaccharide. The ATP molecule includes a monosaccharide molecule, a ribose sugar, the "tri" refers to the number of phosphate groups.

Which of the following is the major difference between cyclic and noncyclic photophosphorylation?

Photosystem II is not involved in cyclic photophosphorylation. Cyclic photophosphorylation occurs when there is a build up of NADPH. It involves Photosystem I only and produces ATP but no NADPH

Which of the following statements regarding the potential energy stored within a log is true?

Potential energy is stored in the chemical bonds of the firewood. A log stores potential energy in the organized chemical bonds of the cellulose, hemicellulose, pectin, and other molecules that comprise it.

A process during which a substance gains electrons is referred to as:

Reduction. Reduction refers to the process by which a molecule gains electrons. When a molecule gains electrons its charge goes down, thus it has been reduced. Hydrogenation, the addition of hydrogen atoms, can be a reduction reaction, but a reduction reaction does not have to be a hydrogenation. Oxidation, on the other hand, is the removal of electrons from a molecule. When a molecule undergoes a reaction that results in an increased number of bonds to more electronegative atoms, electrons will be pulled away by those atoms and the molecule is said to be reduced.

Which statment regarding stomata is false?

Stomata allow for uptake of water vapor from the atmosphere. Oxygen enters the leaf and carbon dioxide exits the leaf by means of microscopic pores called stomata. Stomata are involved in water regulation; they close to prevent desiccation, however water does not eneter the plant though the stomata.

The reactions of the Calvin cycles are referred to as light-independent reactions, yet in most plants they occur during daylight hours. Why?

The Calvin cycle depends on ATP and NADPH from the light-dependent reactions. The Calvin cycle consumes ATP and NADPH that is made during the light-dependent reactions of photosynthesis. This is why the Calvin cycle takes place during the day in most plants.

The Calvin cycle is light independent but typically occurs during the day. Why?

The Calvin cycle depends on products of the light reactions. The Calvin cycle requires ATP and NADPH+H, both of which are formed in the light dependent reactions of photosynthesis.

Which of the following statements is correct?

The Calvin cycle is an example of light independent metabolism. The Calvin cycle is a light independent metabolic pathway.

Which of the following statements adequately describes cooperativity?

The binding of a substrate molecule to a subunit stabilizes the active state of other subunits. Cooperativitys occurs when a substrate itself activates a multi-unit enzyme.

Which of these conversions in the Calvin cycle uses the NADPH and ATP from the light-dependent reactions?

The conversion of 3-phosphoglycerate to glyceraldehyde 3-phosphate. During the reduction phase of the Calvin cycle, ATP and NADPH is consumed. The first reaction involves the conversion of 3-phosphoglycerate into 1,3-bisphosphoglycerate with the consumption of ATP. Then 1,3-bisphosphoglycerate is reduced (while NADPH is oxidized) forming glyceraldehyde 3-phosphate.

Which of these statements concerning the light-dependent reactions of photosynthesis is not true?

The energy lost from the excited electrons can be used to split carbon dioxide if it is present in large quantities. The energy released from the excited lectrons is not used to split carbon dioxide if it is present. Carbon dioxide is not involved in the light-dependent reactions of photosynthesis.

Which of the following statements regarding enzymes is false?

The optimal pH for pepsin and trypsin is the same. The optimal pH for pepsin is different than that of trypsin.

The role of hexokinase in the first part of glycolysis is:

The phosphorylation of glucose A hexokinase accomplished the phosphorylation of glucose in the first step of glycolysis.

Allosteric inhibition involves

The stabilization of an enzyme in an inactive form. An allosteric inhibitor binds to the enzyme's regulatory site, rendering it inactive.

__________ is the source of energy for life on Earth.

The sun The sun serves as the source of energy for life on Earth. Photosynthetic organisms are able to use sunlight to make make complex molecules. In turn, these complex molecules serve as a source of energy for organisms.

Which statement about light is incorrect?

The wavelength of a photon is directly proportional to its energy. The wavelength of a photon is inversely proportional to its energy. The longer the wavelength, the lower the energy

Which of the following does not apply to enzymes?

They increase the energy required to activate the reaction. Enzymes decrease, not increase, the energy required to activate the reaction.

Which of the following graphs illustrate the relationship between pH and rate of reaction for pepsin and trypsin? Enzyme characteristics question 5

This figure shows that pepsin's activity range is acidic and that trypsin's activity range is basic. Also the activity curves have the shape characteristic of enzymes.

Which of the following does not take place during cyclic photophosphorylation?

Water provides electrons to photosystem I. Water donates electrons to photosystem II during noncyclic photophosphorylation. During cyclic photophosphorylation, ferredoxin donates electrons to the cytochrome complex which then return the electrons to P700.

Which molecule in the reaction pathway provided is the phosphorylated intermediate? X-OH + ATP → X-O-P + ADPA-H + X-O-P → A-X + Pi

X-O-P X-O-P is phosphorylated intermediate. X-OH is phosphorylated as ATP is hydrolyzed, forming X-O-P and ADP. X-O-P then loses its phosphate group to form the final product, A-X.

The coenzyme NAD+, is an example of ____________.

a cofactor NAD+ is an example of a cofactor. Cofactors are nonprotein molecules (or ions) that are required for an enzyme's function. NAD+ is a cofactor invloved in several steps of aerobic respiration.

Which structure is found within the thylakoid membrane?

a light-harvesting antenna Light harvesting antenna containing chlorophyll pigments are found embedded in the thylakoid membrane of the chloroplasts.

Allosteric regulation occurs when

a molecule binds to an area other than the active site of the enzyme and prevents it from assuming the conformation necessary to bind substrate. Allosteric regulation occurs when a molecule binds to a site other than the active site on an enzyme and prevents it from assuming the conformation necessary for it to act as a catalyst. This is also referred to as non-competitive inhibition.

Which of the following reactions could be coupled to an endergonic reaction with a delta G of +2.45 kJ / mole?

a reaction with a delta G of −5.34 kJ / mole. A reaction with a delta G of 2.45 kJ / mole could be coupled to a reaction with a delta G of −5.34 kJ / mole because the net reaction would have a negative delta G; thus it would be exergonic.

During photorespiration

a two-carbon molecule leaves the chloroplast for every oxygen molecule that binds to RuBP.

If abcd-ase is the enzyme used to catalyze the reaction A + B → C + D, what enzyme would catalyze the reaction C + D → A + B?

abcd-ase. Because enzymes are reversible, the same enzyme can catalyze the reaction no matter which way it proceeds.

Which of the following molecules is reduced during alcohol fermentation?

acetaldehyde Acetaldehyde is formed from the decarboxylation of pyruvate. Acetaldehyde is then reduced by NADH to form ethanol during alcohol fermentation.

The energy required to initiate a reaction is the

activation energy. The activation energy of a reaction is the energy required to initiate a reaction.

Enzyme specificity appears to be a function of the enzyme's

active site. The active site of an enzyme determines the specificity of the enzyme by dictating the types of molecules to which it can bind.

ATP is used by the cell to ATP structure and function question 6

all of the above ATP is used by the cell to fuel a variety of processes including the synthesis of biological molecules, the active transport of substances across the membrane, and to generate force.

Oxidation and reduction:

always take place together. Redox reactions always occur together. As one molecule loses electrons (oxidized) another molecule gains electrons (reduced). In reduction-oxidation (redox) reactions the molecule that gets reduced is called the oxidizing agent, while the molecule that gets oxidized is called the reducing agent.

The specificity of the active site of an enzyme is determined by the

amino acid sequence. The amino acid sequence of the protein directly determines the higher level structure of the enzyme, as well as the charge at different sites on the enzyme. This combination of shape and charge dictates the specificity of an enzyme.

An action spectrum for a plant has less extreme peaks and valleys than an absorption spectrum for chlorophyll a of the same plant because

an action spectrum reflects the presence of other pigments in the plant. An action spectrum plots the photosynthetic activity of a plant against the wavelength of light. Plants have many different pigments that allow them to absorb many different wavelengths of light; thus an action spectrum does reflect the presence of other pigments in the plant. An absorption spectrum, on the other hand, plots the absorbance against the wavelength of light, for a specific pigment.

The relative effectiveness of different wavelengths of light on the rate of photosynthesis is shown by

an action spectrum. An action spectrum shows the relative effectiveness of different wavelengths of light on the rate of photosynthesis. The rate of photosynthesis is determined by measuring the amount of oxygen produced by a plant exposed to different wavelengths of light.

In a coupled reaction,

an endergonic reaction that requires energy is paired with an exergonic reaction that gives off energy. A coupled reaction uses the energy from an exergonic reaction to drive an endergonic reaction and is the basis for many reactions in living cells.

NAD+ is

an oxidizing agent. NAD+ is able to be reduced to form NADH + H+ (thus it recieves electrons). As NAD+ is reduced, another molecule must be oxidized. A molecule that is reduced is referred to as an oxidizing agent.

Glycolysis is an _____________ process.

anaerobic Glycolysis is an anaerobic process. No oxygen is required for the cell to carry out glycolysis.

Glycolysis occurs in

animal and plant cells. Glycolysis is a pathway that involves the breakdown of organic molecules and the consumption of oxygen to provide energy to the cells. This process is extremely prevalent and takes place in animal cells and both photosynthetic and non-photosynthetic plant cells.

The light harvesting antennae

are groups of pigments that help capture energy from light in a photosystem. Light-harvesting antenna are complexes of a few hundred pigment molecules that are able to pass light energy to the reaction center of a photosystem. In the reaction center, an excited electron is passed to the primary electron acceptor. From the primary electron acceptor the electron will be passed down a series of redox reactions. The energy given off at each step will be used to make ATP.

The extant Archaean group known as the extreme halophiles use a pigment called ___________________ to harness light energy.

bacteriorhodopsin The extreme halophiles possess the pigment bacteriorhodopsin for harnessing light energy.

Which of the following is not a stage in the Calvin cycle?

carbon regeneration There is no carbon regeneration phase of the Calvin cycle. The Calvin cycle consists of three stages including, carbon fixation, reduction, and RuBP regeneration.

During photosynthesis, photophosphorylation and photolysis both occur in the

chloroplasts. Photophosphorylation and photolysis take place in the chloroplasts of plant cells. The chloroplasts are organelles that contain chlorophyll pigments and they are the site of photosynthesis.

Which type of inhibitor always binds to the active site of an enzyme?

competitive inhibitor A competitive inhibitor always binds to the active site of an enzyme. Once bound to the active site, a competitive inhibitor prevents the substrate from entering and binding to the active site.

Molecules that are similar in shape to an enzyme substrate but are nonreactive if they bind to the active site are

competitive inhibitors

Non-enzymatic molecules that are close in shape to the enzyme substrate, but are non-reactive, are

competitive inhibitors. Non-enzymatic molecules that are close in shape to the enzyme substrate, but are non-reactive, are competitive inhibitors. They compete with the substrate for access to the active site of the enzyme and slow the rate of the enzyme-catalyzed reaction.

To drive a reaction with a high positive net free energy, __________ is necessary. To speed up a reaction with a high activation energy, __________ is useful.

coupling with an exergonic reaction; a catalyst Coupling an endergonic reaction with an exergonic reaction is an effective method of achieving the energy input needed for the endergonic reaction. Catalysts are effective in lowering the activation energy of a reaction to increase the rate of the reaction.

Electrons are excited and leave Photosystem I where they are then taken up by an electron acceptor. The electron acceptor passes them down an electron transport chain of proteins and eventually they are passed back to Photosystem I. What is the name of this pathway?

cyclic electron flow In cyclic electron flow, electrons make a cycle from photosystem I, down an electron transport system and back to photosystem I. As the electrons are passed through the electron transport system the energy that they release is used to pump protons across the membrane. The concentration gradient that results is used to drive ATP synthesis.

A major difference between cyclic and noncyclic photophosphorylation is

cyclic photophosphorylation produces no NADPH. Noncyclic photophosphorylation involves both photosystems. An electron is excited from Photosystem II and passed down the electron transport chain in the thylakoid until it is passed to Photosystem I where it will be excited again and eventually used to form NADPH. Cyclic photophosphorylation involves only Photosystem I. Electrons are passed down a chain of proteins pumping hydrogen ions into the lumen of the thylacoid. No NADPH is formed during cyclic photophosphyorylation.

Glycolysis begins in the __________ and ends in the _____________.

cytoplasm; cytoplasm Glycolysis is a process that does not require oxygen and begins and ends in the cytoplasm.

Enzymes catalyze a reaction by

decreasing the amount of activation energy needed to drive the reaction. Enzymes catalyze a reaction by lowering its activation energy.

Protons in the lumen of the thylakoid

diffuse out of the lumen to make ATP. Protons diffuse out of the lumen of the thylakoid through a protein complex called ATP synthase. As the protons flow through ATP synthase they fuel the production of ATP.

Fermentation

does not require oxygen. Fermentation does not require oxygen. Fermentation is actually a mechanism for ATP production in the absence of oxygen. Fermentation oxidizes NADPH + H+ to form NAD+, which is necessary for glycolysis to take place. By recycling NAD+ in fermentation, the cell is able to exist on the ATP provided by glycolysis alone in the absence of oxygen.

During a reduction reaction,

electrons are passed from the molecule which is oxidized to the molecule which is reduced. If a molecule removes electrons from another molecule (the molecule that is oxidized), it becomes reduced (it gains electrons). The molecule that is oxidized, on the other hand, provides electrons to the molecule that thereby becomes reduced. The end result is the transfer of electrons from the molecule that is oxidized to the molecule that is reduced.

A reaction center of a chloroplast is

embedded in the thylakoid. A reaction center is embedded within the thylakoid membrane. In the reaction center, an electron from chlorophyll a is excited by a photon and passed to an electron acceptor protein. Its energy will eventually be used to fuel ATP synthesis.

A(n) __________ reaction requires a net input of energy.

endergonic A reaction that requires an input of energy is an endergonic reaction. Energy is consumed rather than released during the course of the reaction, and the reaction is not spontaneous.

Chlorophyll glows red when it is hit with UV light because

energy is released from an electron that falls to its ground state. Chlorophyll glows red as it is hit with UV because it's electron was excited to a higher energy level (by UV light) and as it falls back to the ground state, it emits light energy.

The third phosphate bond is called a high energy bond because

energy is released when the bond is broken. The phosphate bonds in ATP are called high energy bonds because they are somewhat unstable and their hydrolysis releases energy.

The breakdown of sugar is a(n) _________________ reaction.

exergonic The breakdown of sugar (into carbon dioxide and water) releases energy and is therefore exergonic.

Chlorophyll's absorption spectrum

explains why chlorophyll is green. The absorption spectrum for chlorophyll shows that green is not absorbed by chlorophyll, it is therefore reflected. Wavelengths of light that are reflected can be percieved by the eye, which explains why chlorophyll appears green.

True or false?Plants are heterotrophs, because they rely on water, light, and carbon dioxide for food.

false Plants are autotrophs because they are able to synthesize organic molecules from inorganic sources. Plants use energy from light, water, and carbon dioxide to produce carbohydrates

True or false?The cuticle is also referred to as the upper epidermis.

false The cuticle is a waxy waterproof covering that is secreted by the upper epidermis. The upper epidermis is the layer of cells on the upper surface of the leaf.

ATP acts as a phosphorylated intermediate used to fuel exergonic reactions.

false ATP is used to fuel endergonic reactions by forming phosphorylated intermediates with other molecules.

Electrons in the chlorophyll molecule become so excited that they escape to a lower energy level.

false An electron in the chlorophyll molecule gets excited by a photon of light and escapes to a higher energy level.

The C4 and C3 pathways differ in that they take place at different times, whereas CAM and C3 pathways differ in that they occur at different locations within the leaf.

false C4 plants fix carbon dioxide in the mesophyll cells, and undergo the Calvin cycle in the bundle sheath cells. C3 plants do not divide up the location of their light-independent pathways. Both use their pathways during the day.CAM plants fix carbon dioxide at night and use the Calvin cycle during the day, while C3 plants perform both of these processes during the day. The correct statement is: C4 and C3 pathways occur at different locations, while CAM and C3 pathways occur at different times.

True or false?Feedback inhibition increases the rate of production of enzymatic product.

false Feedback inhibition occurs when the product of a metabolic pathway inhibits the first enzyme in the pathway. This decreases the rate of production of that product.

Molecules exist that can inhibit enzyme activity; however, no known molecules can promote enzyme activity.

false Inhibitors can decrease enzyme activity and cofactors can promote enzyme activity.

True or false?Leaves appear green to us because green light is mostly absorbed by chlorophyll a.

false Leaves appear green to us because green light is largely reflected. Chlorophyll, a major pigment in leaves, does not absorb green wave lengths of light effectively.

The active site is a rigid pocket in the enzyme that is perfectly shaped to match the shape of the substrate molecule.

false As the substrate enters the active site of the enzyme, it is thought too induce a shape change in the enzyme, causing the active site to fit the substrate more closely.

In the following system, what is the role of thyroxin in the step labeled number 1? Feedback inhibition and cooperatively question 4

feedback inhibitor Thyroxin acts as a feedback inhibitor in this pathway. When thyroxin concentrations become high, the metabolic rate increases. Thyroxin also acts as an inhibitor to TSH, the hormone that stimulates the thyroid to produce thyroxin. This causes a decrease in thyroxin levels, decreasing the metabolic rate. This system is called feedback inhibition.

Fermentation differs from cellular respiration because

fermentation does not require oxygen. Fermentation differs from cellular respiration because cellular respiration requires oxygen, while fermentation does not.

A proton gradient is formed in both mitochondria and chloroplasts. The chloroplasts differ from the mitochondria in that their proton gradient

flows outward from a lumen rather than inward. The protons gradients produced in mitochondria and chloroplasts differ in that the proton gradient of the chloroplasts flows from the lumen of the thlylakoid (an inner compartment) out into the stroma. The proton gradient in the mitochondria flows from the intermembrane space into the matrix, which is the inner compartment of the mitochondria.

In the absence of an inhibitor or activator an enzyme that is allosterically controlled will

fluctuate between being active and inactive. The enzyme will naturally oscillate between active and inactive states.

The amount of energy available to do work in a system is the

free energy. The energy available to do work in a system is its free energy.

In general, enzymes

function most quickly at an intermediate temperature. Enzymes increase activity at higher temperatures. Above a certain temperature for a given enzyme, activity will fall sharply.

When a molecule is reduced, it

gains electrons. When a molecule is reduced it gains one or more electrons, causing a reduction in charge.

During glycolysis

glucose is broken down and oxidized to form two pyruvate molecules, a net of two ATP, and two NADH. During glycolysis, hydrogen atoms are removed from glucose. The removal of a hydrogen atom can be thought of as the removal of an electron and a proton. The removal of electrons is referred to as oxidation. Also in the process of glycolysis, a net of two ATP, and two NADH are formed.

Which of the following molecules represents the end-product of the Calvin cycle?

glyceraldehyde 3-phosphate Glyceraldehyde 3-phosphate is the end product of the Calvin cycle. For every 3 turns of the Calvin cycle one glyceraldehyde 3-phosphate is released for use as a building block for other organic molecules (such as glucose).

Which pathway is common to both fermentation and cellular respiration?

glycolysis Glycolysis occurs in both fermentation and cellular respiration. In cellular respiration, the end product of glycolysis is further broken down in the Krebs cycle and the electron transport chain to produce more ATP. In fermentation, the end-product of glycolysis is converted into either lactic acid or ethanol (depending on the organism), which will eventually get reconverted to pryuvate. This process recycles the components that are required for glycolysis to continue.

Red blood cells of mammals do not have mitochondria. Since red blood cells lack mitochondria, what process provides their energy?

glycolysis A cell that lacks mitochondria, such as a red blood cell, will not be able to undergo aerobic respiration because aerobic respiration takes place in the mitochondria. Instead, the cell will undergo anaerobic metabolism. Anaerobic metabolism involves alchohol fermentation, but alchohol fermentation does not provide energy. Glycolysis is the anaerobic process that produces the energy that the cell will use.

The pathway in which glucose is broken down to form pyruvate is called

glycolysis. Glycolysis is the process that involves the breakdown of glucose (a six carbon molecule) to form two pyruvates (two, three-carbon molecules).

Stacks of membranous compartments in chlorplasts are referred to as

grana. The stacks of membranous compartments in chloroplasts are referred to as the grana (singular: granum). Each membranous compartment is called a thylakoid.

The energy content for visible light is greatest for

green light. Green light has the shortest wavelength of all the choices, thus it has the highest energy. The shorter the wavelength of light is, the higher the frequency of the wave. Wave frequency is directly proportional to the energy content of light.

Adenosine triphosphate __________.

has unstable bonds that are weaker than most covalent bonds in organic molecules. The phosphate bonds in ATP are unstable bonds because of the crowding of the phosphate groups. Each phosphate group is negatively charged. These negative charges repel one another, making the bonds unstable and therefore fairly weak compared to other covalent bonds within the cell. Because the products of ATP hydrolysis are more stable than ATP, energy is released from its hydrolysis.

In a hypothetical scenario, the first photosynthetic unit used bacteriorhodopsin as an antennae to capture light and generate a gradient of ____________________ drove the synthesis of ATP.

hydrogen ions A gradient of hydrogen ions drives the synthesis of ATP.

Where would you expect to find the lowest pH in a chloroplast of an actively photosynthesizing cell?

in the lumen of the thylakoid The lumen of the thylakoid would have the lowest pH because a high concentration of protons is constantly being maintained within the lumen. pH is a function of proton concentration. When the proton concentration is high, the pH is low (and vice versa). During photosynthesis a proton gradient is maintained by the active pumping of protons across the thylakoid membrane into the lumen of the thylakoid.

Where is ATP produced in the light reactions?

in the stroma. ATP made during photosynthesis is produced in the stroma of the chloroplast. The energy released from electrons excited by light is used to pump protons into the lumen of the thylakoid. Protons within the thylakoid lumen diffuse out to the stroma through the ATP synthase enzyme complex. The movement of the protons through ATP sythase fuels the production of ATP from ADP + Pi.

A(n) __________ is any molecule that binds with an enzyme to down-regulate catalysis.

inhibitor An inhibitor is any molecule which binds to an enzyme, either at the active site or another regulatory site, for the purpose of down-regulating catalysis.

One round of glycolysis

involves the use of kinase enzymes to synthesize ATP. Glycolysis involves the use of kinases to synthesize ATP during the energy releasing phase. Protein kinases are enzymes that are involved in the transfer of phosphate groups to molecules. This transfer can involve the transfer of phosphate from ATP to another molecule or the transfer of a phosphate from another molecule to ADP to make ATP. The two kinases used to produce ATP in glycolysis are phosphoglycerokinase and pyruvate kinase.

The mesophyll of the leaf

is a tissue composed of cells separated by numerous air spaces. There are two types of mesophyll found within the interior of a plant leaf. The upper layer of mesophyll is referred to as the palisade parenchyma. Beneath the palisade layer is a layer called the spongy paranchyma. The spongy parenchyma consists of rounded cells that are separated by many air spaces.

If a reaction occurs and the change in G (delta G) for the reaction is −500 Joules, then the reaction

is exergonic, is catabolic, involves breaking chemical bonds All of the answers mean the same thing: the reaction gives off energy. A reaction that is catabolic involves the breaking of chemical bonds. Such a reaction is exergonic.

The major effect of an enzyme in an endergonic reaction is to

lower the activation energy required. Enzymes lower the activation energy required in an endergonic reaction.

Chloroplasts are mostly located in the __________.

mesophyll The mesophyll cells in leaves contain the majority of chloroplasts in a leaf and are responsible for the majority of photosynthesis in a plant.

The _____ is the electron donor in a reaction.

molecule which is oxidized Since reduction is a decrease in charge due to an acceptance of electrons, the molecule which is oxidized will be the species donating the electrons.

A ____ value for the free energy of reaction (delta G) indicates a spontaneous or _____ reaction that is ___________.

negative; exergonic; catabolic A negative free energy value indicates an exergonic, or energy-releasing and a spontaneous, reaction. An exergonic reaction would involve a catabolic process, such as the break down of a molecule into simpler molecules.

A component of NAD+ is obtained in the diet from:

niacin Niacin is a B vitamin that is a component of NAD+ that is obtained from the diet.

Feedback inhibition, or negative feedback, results in levels of product that

oscillate around an optimal level. Negative feedback control systems result in a level of product that increases and decreases around an optimal set point as the inhibition kicks in or is relaxed.

When an electron from Photosystem I is excited and transferred to a primary electron acceptor, the chlorophyll a in the reaction center will be __________.

oxidized When the chlorophyll a in the reaction center of Photosystem I loses an excited electron it becomes oxidized. Oxidation is the loss of electrons from a molecule or atom.

Since NAD+ is an ____________ it is able to get_________.

oxidizing agent; reduced Since NAD+ is able to accept an electron and become reduced forming NADH, it is an oxidizing agent.

The waste byproduct produced by photosynthesis in cyanobacteria is

oxygen gas Cyanobacteria use water as a source of protons in photosynthesis, as a consequence they also liberate oxygen which forms oxygen gas.

An important goal of the energy investment phase of glycolysis is the

phosphorylation of a 6-carbon molecule. The very first step of glycolysis involves the phosphorylation of glucose to form glucose 6-phosphate.

Light is composed of particles of energy called

photons. Light is composed of particles of energy called photons. Photons are discrete packets of energy.

Glycolysis accounts for all of the following except

production of pyruvic acid Pyruvate, not pyruvic acid is a product of glycolysis

Water's role in photosynthesis is to

provide electrons to the light-dependent reactions. Water's role in the light-dependent reactions of photosynthesis is to provide electrons to Photosystem II after it loses excited electrons. In order to do this, water is split in a process called photolysis forming electrons, protons, and oxygen.

What is the electron acceptor during lactic acid fermentation?

pyruvate During lactic acid fermentation, pyruvate is reduced by NADH forming NAD+ and lactate.

The conversion of NAD+ to NADH is a/an ___________ and it involves ________________.

reduction; enzymes called dehydrogenases NAD+ gains electrons when it is converted to NADH, thus it is a reduction. This reaction also involves the removal of hydrogen atoms from another molecule and their transfer to NAD+. Such a reaction is mediated by enzymes called dehydrogenases.

The Calvin cycle begins when carbon dioxide reacts with what five carbon molecule?

ribulose bisphosphate Carbon dioxide reacts with ribulose bisphosphate (RuBP) in the carbon fixing phase of the Calvin cycle. The enzyme rubisco mediates this reaction.

ATP releases energy by:

splitting into a phosphate ion and ADP When the bond is broken between the third phosphate group and the rest of the ATP molecule, the products are more stable, thus energy is released.

Carbon dioxide is taken in and water vapor and oxygen are released through the

stoma A stoma (plural stomata) is a small pore found on the surface of leaves that can open and close. Stomata function in the exchange of gases between a plant and its environment.

The fluid outside of the granum in a chloroplast is called the ___________.

stroma The fluid that surrounds the grana in a chloroplasts is referred to as the stroma. The stroma is where the synthesis of organic molecules from carbon dioxide and water takes place.

Anabolic pathways can be described as

synthetic and endergonic Anabolic pathways are the metabolic pathways that involve the formation of complex molecules from less complex ones. The formation of bonds requires an input of energy; thus reactions that build molecules are endergonic

Which environmental factors can affect an enzyme?

temperature and pH Enzymes are sensitive to temperature and pH.

A coupled reaction takes place when

the energy released from one reaction is used to fuel another. A coupled reaction takes place when the energy released from one reaction fuels another endergonic reaction. This often happens through the formation of phosphorylated intermediates. In the formation of phosphorylated intermediates, the hydrolysis of ATP is coupled to an endergonic reaction through the transfer of the phosphate group to another molecule. The phosphorylated molecule that results is less stable than it was without the phosphate group. This form of energy coupling makes the overall reaction exergonic.

Joseph Priestly discovered that

the gas that a mouse removes from the air is produced by plants. Joseph Priestly found that when he placed a plant and a mouse together in a jar, the mouse would live. If he placed the mouse alone in the jar, it would eventually run out of oxygen and die. He also found that if a candle was placed in the jar alone, it would eventually go out, while if it was placed in a jar with a plant, it would continue to burn. Priestly's experiment established that plants are able to release a gas that animals take in. This gas was found to be oxygen.

The major site of photosynthesis in plants occurs in the

the leaf. The mesophyll of the leaf is the primary site of photosynthesis in plants. Mesophyll cells are full of chloroplasts that contain chlorophyll, which is the primary pigment involved in photosynthesis.

Ribulose bisphosphate plays an important role in

the light independent reactions of photosynthesis.

The addition of carbon dioxide to a five-carbon intermediate followed by a reduction of the product of that reaction is called __________ and occurs in the __________.

the light-independent reactions; the stroma of the chloroplast This process is known as the light-independent reactions or the Calvin cycle, and it takes place in the stroma of the chloroplast. The stroma is the fluid of the chloroplast that surrounds the thylakoid.

Chlorophyll is a green pigment found embedded in

the membrane that makes up the grana. Chlorophyll is embedded in the membrane of the grana, or the thylakoid membrane.

Enzymes bind to particular substrates because

the shape and charge of the active site is complementary to the substrate. Enzymes bind particular substrates because the shape and charge of the enzyme is complementary to the shape and charge of the substrate.

In an enzyme catalyzed reaction that breaks down a sucrose molecule into a glucose and a fructose molecule, what is the sucrose molecule called?

the substrate A substrate is the molecule the enzyme works on.

In eukaryotic photosynthesis, the transfer of electrons through membrane proteins provides energy to pump protons across

the thylakoid membrane. During photosynthesis, the transfer of excited electrons through a sequence of proteins provides energy to pump protons across the thylakoid membrane into the lumen. The concentration gradient of protons in the lumen of the thylakoid is used to fuel ATP sythesis.

The first law of thermodynamics states that

the total energy of the universe is constant. The first law of thermodynamics states that the total energy in the universe remains constant. Energy cannot be created or destroyed.

The second law of thermodynamics states that

the total entropy of the universe increases with each energy transfer. According to the second law of thermodynamics, each energy transfer increases the amount of disorder, entropy, in the universe.

Aerobic respiration and the light dependent phases of photosynthesis have all of the following characteristics in common except

they both consume oxygen Both processes do not consume oxygen. Aerobic respiration uses oxygen as a final electron acceptor forming water, while the light-dependent reactions of photosynthesis release oxygen from the photolysis of water.

The first photosynthetic organisms were likely archaeans because

they evolved later than bacteria, the first heterotrophs. This is the reason why Archaea are considered a candidate for the evolution of photosynthesis.

The light-dependent reactions in plants occur in the

thylakoid membrane. The light-dependent reactions in plants occur in the thylakoid membrane. The light dependent reactions require photosynthetic pigments that are found embedded in the thylakoid membrane.

The purpose of cyclic electron flow is

to increase the ATP/ NADPH ratio. The purpose of cyclic electron flow is to produce ATP without producing NADPH. Thus cyclic electron flow increases the ATP/NADPH ratio.

The ultimate goal of cellular respiration is to

transfer energy. The ultimate goal of cellular respiration is the transfer of energy stored within the bonds of large complex molecules to a more usable form, ATP.

Pyruvate kinase

transfers a phosphate group from PEP to form ATP. The enzyme pyruvate kinase catalyzes the last step in glycolysis, which involves the transfer of a phosphate group from PEP to form ATP and pyruvate.

True or false? ATP acts as a carrier of chemical energy.

true ATP acts as a carrier of chemical energy. The hydrolysis of ATP in the cytosol releases a great deal of usable energy. This energy is used by the cell for a number of processes that require an input of energy.

An electron in chlorophyll a is excited to a higher energy level by light and is passed to a nearby electron acceptor molecule in the thylakoid.

true As one of the electrons in the chlorophyll of the antenna is excited to a higher energy level, it is transferred to an acceptor molecule to initiate electron flow.

Chlorophyll is able to act as a reducing agent.

true Chlorophyll is able to act as a reducing agent. When an electron is excited from chlorophyll, it may either fall back down to its ground state or be caught by an electron acceptor. The electron acceptor that has caught an electron is then reduced. Thus chlorophyll can act as a reducing agent.

True or false?During the C4 pathway, carbon dioxide is fixed in the mesophyll cells and enters the Calvin cycle in the bundle-sheath cells.

true In the C4 pathway, carbon dioxide is fixed onto PEP, a 3-carbon molecule to eventually form a 4-carbon compound that enters the bundle-sheath cell and releases carbon dioxide. Carbon dioxide then is made into organic material by rubisco and the Calvin cycle.

True or false?Rubisco binds to both oxygen and carbon dioxide.

true Under typical conditions rubisco will bind to carbon dioxide and fix it into the Calvin cycle. Photorespiration takes place when oxygen levels build up within the plant leaf due to the closing of the stomata under hot dry conditions. Rubisco will bind to oxygen rather than carbon dioxide and the output of the Calvin cycle will decrease as a result.

ATP is composed of the sugar ribose that has an adenine base and three phosphate groups.

true ATP is a triphosphorylated nucleotide. It consists of the sugar ribose that has an adenine group connected to the 1' carbon and three phosphate groups connected to the 5' carbon.

True or false?An allosteric site is a binding region on an enzyme other than the active site.

true Allosteric inhibitors and allosteric activators bind to sites on the enzyme that are in a different location from the active site.

True or false?Chlorophyll b and carotenoids are pigments used by plants to increase the wavelengths of light that can be used for photosynthesis.

true Chlorophyll a is the pigment involved directly in the light reactions of photosynthesis. However, chlorophyll b and carotenoids also are used for photosynthesis in some plants. They absorb light at different wavelengths allowing for a broader absorption spectrum for photosynthesis.

True or false?Glycolysis yields more ATP than fermentation alone.

true Glycolysis yields a net of two ATP while fermentation alone yields no ATP. The purpose of fermentation is to oxidize NADH + H+ to form NAD+, a necessary component for glycolysis. By reforming NAD+, a cell is able to continue glycolysis and make ATP in the absence of oxygen.

True or false?Chloroplasts are organelles that are composed of three membranes.

true Similar to mitochondria, chloroplasts have both an inner and outer membrane. In addition to these two membranes, chloroplasts also have the thylakoid membrane system consisting of thylakoids and the membranes that interconnect them, called stroma lamellae.

When a chlorophyll molecule becomes excited by light, it becomes a reducing agent.

true When a chlorophyll molecule is excited by light, one of its electrons is boosted to a higher energy level and may be passed to an electron carrier. When a molecule gains electrons it is reduced, thus chlorophyll acted as a reducing agent.

In the energy investment phase of glycolysis

two molecules of ATP are invested making glucose and its derivatives more reactive. During the energy investment stage of glycolysis, two molecules of ATP are hydrolyzed to make glucose and fructose 6-phosphate less stable and therefore more chemically reactive. This increase in reactivity is used to drive the synthesis of ATP in the latter half of glycolysis.

Which of the following sequences correctly represents the flow of electrons in the light-dependent reactions of photosynthesis?

water, Photosystem II, Photosystem I, NADP Electron flow in the light-dependent reactions of photosynthesis begins with the photolysis of water, which provides electrons to Photosystem II. Excited electrons are then passed down an electron transport chain to Photosystem I. From Photosystem I, electrons are eventually passed to NADP.

An electron from Photosystem II is lost when it is excited by a photon of light. Photosystem II is supplied with another electron from

water. The electron "hole" in Photosystem II is filled supplied from the splitting of water. Water is split into two protons, two electrons and half of an oxygen molecule by an enzyme in the thylakoid. The electrons from this split are used to replace the electrons lost by the chlorophyll a in the reaction center of Photosystem II.

Johann Baptista van Helmont concluded that the willow tree gained its weight from

water. Van Helmont concluded that the tree gained its weight from water alone. Although his conclusion was not entirely accurate, he did establish water's role in the production of plant material.

In order to prevent combustion inside our bodies when we drink a soda,

we have evolved mechanisms to regulate the release of energy from sugar. Sugar is the main source of our energy and the energy contained in its bonds is extracted in a controlled way.