biology chapter 5

ATP

Adenosine triphosphate, a small, energy rich organic molecule that is used to store energy and to move it from one part of a cell to another. Every living cell uses ATP.

Metabolism

All the chemical reactions that occur inside living cells, including those that release and store energy.

electron transport chain

An elaborate chain of chemical events in which electrons and protons (H+) are handed over to other molecules that ultimately generates ATP and NADPH.

Two students are debating whether switching energy production from fossil fuels to traditional biomass would reduce carbon dioxide emissions. Explain the role of photosynthesis in storing carbon dioxide in these two energy sources. What is the total energy consumption shown for these two energy sources?

Fossil fuels, such as oil and petroleum, were created when ancient organisms used photosynthesis to capture energy from sunlight. Part of the process of photosynthesis is the production of sugars from carbon dioxide. Traditional biomass, including wood and agricultural fuels, also relies on photosynthesis as a way to capture light energy and store it as chemical energy that is released when these materials are burned. The total energy consumption from fossil fuels and traditional biomass is 87.2 percent.

Which of the following statements is not true?

Glycolysis produces most of the ATP required by aerobic organisms like us.

List the energy carriers in a cell. Which of the energy carriers carries the most energy?

The energy carriers are ATP, NADPH, NADH, and FADH2. ATP carries the most energy.

Rubisco

The enzyme that catalyzes the first step in the light-independent reactions of photosynthesis, fixing a carbon molecule from CO2.

Which step of cellular respiration occurs outside the mitochondria?

glycolysis

Plants in the genus Ephedra have been harvested for their active substance ephedrine for centuries. Ephedrine is used to reduce the symptoms of bronchitis and asthma, as a stimulant and study aid, and as an appetite suppressant. It is also the main ingredient in the illegal production of methamphetamine. Since 2006, the sale of ephedrine and related substances has been limited and monitored in the United States. One effect of ingesting ephedrine is greatly increased metabolism, which has been known to kill users of ephedrine. How might an increased metabolic rate cause death?

if metabolic processes occur at a higher rate than can be sustained by cellular respiration, then it is possible to die from lack of usable energy

cellular respiration

in which sugars are broken down into energy usable by the cell.

after an enzyme catalyzes a chemical reaction there is a(n) ________ in the concentration of _______

increase, enzyme

You have been transported into the future, where a nanosensor can be inserted into a living cell and subsequently travel into any organelle. The sensor relays information stating that it has lodged itself in a compartment of the mitochondrion, where t here is a concentration gradient of hydrogen ions (H+) and levels of ATP production are high. From what you know about cellular respiration in mitochondria, where is the sensor lodged

inner mitochondrial membrane

Krebs cycle

(Also called citric acid cycle) The second of three stages of cellular respiration. In this sequence of enzyme driven reactions, the pyruvate made in glycolysis is broken down, releasing CO2 and producing large amounts of energy carriers, including ATP, NADH, and FADH2.

Light Independent Reactions (Calvin Cycle)

(Also called the Calvin cycle or carbon fixation) .*The second of two principal stages of photosynthesis, in which a series of enzyme catalyzed chemical reactions converts carbon dioxide (CO2) into sugar, using energy delivered by ATP and electrons and hydrogen ions donated by NADPH.

Metabolic pathways

are often organized as a multistep sequence of reactions.

Which of the following is a product of the light reactions of photosynthesis?

oxygen, ATP, and NADPH

Calvin Cycle

(also called Carbon Fixation) The second of two principal stages of photosynthesis, in which a series of enzyme catalyzed chemical reactions converts carbon dioxide (CO2) into sugar, using energy delivered by ATP and electrons and hydrogen ions donated by NADPH

Steps of cellular respiration in order

*glycolysis, krebs cycle, electron transport chain *Glucose is broken down to produce ATP and NADH. *If oxygen levels are adequate, pyruvate is transported into the mitochondrion. If oxygen levels are very low, fermentation proceeds. *The Krebs cycle produces the energy carriers NADH, FADH2, and ATP. *An electron transport chain produces ATP from ADP.

Chlorophyll

A green pigment that is specialized for absorbing light energy.

Fermentation

A metabolic pathway by which most anaerobic organisms extract energy from organic molecules. It begins with glycolysis and is followed by a special set of reactions whose only role is to help perpetuate glycolysis. Fermentation enables organi sms to generate ATP anaerobically.

energy carrier

A molecule that can store and deliver usable energy.

The chemical 3-(3,4-dichloro-phenyl)-1,1-dimethylurea (DCMU) blocks the movement of electrons at the point indicated by the black, downward-pointing arrow in the figure below. Which of the following would be an immediate effect of treating a chloroplast with this drug?

A proton gradient would not be created, so ATP could not be made.

metabolic pathway

A series of chemical reactions that either builds a complex molecule or breaks down a complex molecule into simpler compounds.

Enzyme

A type of protein that speeds up a chemical reaction in a living thing

The most common energy carrying molecule in all organisms is

ATP

Which of these molecules carries the most energy?

ATP

Which of the following statements describe the function of the light reaction in photosynthesis?

As electrons move through the light reaction, they release energy that is used to concentrate protons in the thylakoid.

Is the burning of wood most representative of anabolism or catabolism?

Burning wood releases energy and breaks down larger molecules into smaller components. Therefore, burning of wood represents catabolism.

What would be the initial outcome of decreasing the number of photosynthetic organisms on Earth with no change in the number of organisms using cellular respiration?

Carbon dioxide levels would increase.

The step of cellular respiration that produces a product that will also be used in the Calvin cycle is the ________.

Kreb Cycle

Anabolism

Metabolic pathways that create complex biomolecules from smaller organic compounds.

Catabolism

Metabolic pathways that release chemical energy in the process of breaking down complex biomolecules.

n 2012, an Illinois man was killed by cyanide poisoning after he won a million dollars in the lottery. Cyanide is a lethal poison because it interferes with the electron transport chain in mitochondria. What effect would cyanide have on cellular respiration?

Oxidative phosphorylation would be inhibited.

What is the importance of photosynthesis to organisms other than plants?

Photosynthesis captures energy that other organisms access when they eat either plants or organisms that eat plants.

Defend the following statement by discussing the importance of the products of photosynthesis: "The evolution of photosynthesis was an essential event for the evolution of life as we know it."

Photosynthesis produces oxygen, which allows other organisms to conduct cellular respiration rather than fermentation. This allows these organisms to produce much more ATP. Photosynthesis also produces sugars, which are used as an energy source by other organisms.

Excess carbon dioxide in the atmosphere is increasing climate change. How do photosynthesis and cellular respiration relate to this issue, and how can we use this knowledge to help decrease this problem?

Photosynthesis takes in carbon dioxide; respiration produces it. If we increase the number of photosynthetic organisms, we could decrease the concentration of carbon dioxide in the atmosphere.

Humans store sugars in the form of glycogen. Glycogen is made by linking many glucose molecules together. This process is ________.

Polysaccharides

The Calvin cycle reactions are sometimes called the "light independent reactions" or "dark reactions" to contrast them with the light (or light dependent) reactions. Can the Calvin cycle be sustained in algae that are kept in total darkness for several days? Why or why not?

The Calvin cycle cannot be maintained indefinitely, because it requires a source of energy to produce ATP. This energy source (glucose) is created from sunlight energy during the light reactions.

Plants and animals use different energy storage molecules, yet they both use the same mechanism to "burn" their stored energy. How can plants and animals both be successful, even though they "burn" different energy storage molecules?

The breaking of the chemical bonds of a storage molecule transfers energy, no matter what molecule is stored.

A chemical reaction that uses ATP to build cellular components is

anabolic

Glycosis

The first of three stages of cellular respiration. During glycolysis, sugars (mainly glucose) are split to make the three carbon compound pyruvate. For each glucose molecule that is split, two molecules of ATP and two molecules of NADH are released.

light reactions

The first of two principal stages of photo synthesis, in which chlorophyll molecules absorb energy from sunlight and use that energy for the splitting of water, which in turn produces oxygen gas (O2) as a by product that is released into the atmosphere.

Photosynthesis

The process by which organisms capture energy from the sun and use it to create sugars from carbon dioxide and water, thereby transforming light energy into chemical energy stored in the covalent bonds of sugar molecules.

Two students are discussing the importance of glycolysis in human cells. One student states that the main function of glycolysis is to produce ATP. The other states that the main function is to produce NADH. Which student is correct?

The second student is correct. Although glycolysis does produce some ATP, the NADH produced by glycolysis will be used by the electron transport chain to produce much more ATP. Therefore, the bulk of the ATP produced is due to the production of NADH rather than ATP directly in glycolysis.

oxidative phosphorylation

The third of three stages of cellular respiration. During this process, the chemical energy of NADH and FADH2 is converted into the chemical energy of ATP, while electrons and hydrogen atoms removed from NADH and FADH2 are handed over to molecular O2, creating water (H2O). A large amount of ATP is generated.

A mutation in a plant cell produces rubisco enzymes, which can only bind O2 (and not CO2). What would be the outcome of this mutation?

This plant would not be able to produce sugars in the Calvin cycle because they would not bind the carbon needed to produce the sugars.

The image below diagrams the action of an enzyme. Notice that the enzyme is depicted as being more tightly wrapped around the substrates in step 2 than it is in step 1. Why is this?

When a substrate locks into the active site of an enzyme, the enzyme changes shape to mold itself around the substrates.

After strenuous exercise, you may notice that your muscles burn and feel sore the next day. Which statement best explains this phenomenon?

Without adequate oxygen, muscle cells are fermenting pyruvate into lactic acid.

Cells contain the molecule GTP (guanosine triphosphate). Would this molecule be useful as an energy carrier (similar to ATP)?

Yes because it contains a nitrogenous base just like ATP

The ________ of an enzyme is an area with a specialized shape and set of chemical properties that allows the enzyme to bind with a particular substrate.

active site

A plant cell is mutated so ATP synthase no longer functions. Which process will be affected?

both photosynthesis and respiration

chemical reactions that break down lipids are

catabolic

The reaction sugar + oxygen → carbon dioxide + water + ATP is part of

cellular respiration.

When ATP breaks down into ADP and a phosphate group,

energy is released and can power cellular activities

The energy required for life processes must be extracted from an organism's

environment

Which of the following events in a cell would require ATP?

linking together amino acids to form a protein

If the mitochondria of a cell did not produce an inner membrane, the mitochondria would be unable to

maintain the proton gradient required for ATP production.

In the reaction C6H12O6 + 6 O2 → 6 CO2 + 6 H2O, the 6 CO2 molecules are examples of

products

Glycolysis is an anaerobic process, indicating that the glycolytic reactions

require no oxygen.

Carbon dioxide is one product of a metabolic process, which occurs in both plants and animals. This process is called

respiration

Enzymes

speed up reactions that would otherwise occur much more slowly.

The major product of photosynthesis is

sugar

Photosynthesis and cellular respiration are both complementary and relatively balanced, but early history of life on Earth showed increasing oxygen concentrations. This indicates that

the amount of photosynthesis occurring exceeded the amount of cellular respiration.

Enzymes can catalyze a reaction only if

they encounter a substrate that fits their active site

The Krebs cycle functions to

transfer chemical energy from pyruvate to energy carriers.

Events in Calvin Cycle

use ATP and NADPH to produce sugars.