Ch.04 How Cells Obtain Energy

____________ respiration takes place in the ____________.

Aerobic, Mitochondria

Metabolism

All the chemical reactions that take place inside cells, including those that use energy and those that release energy

Endergonic

Describes a chemical reaction that results in products and store more chemical potential energy that the reactants.

Exergonic

Describes a chemical reaction that results in products with less chemical potential energy than the reactants, plus the release of free energy.

Catabolic

Describes the pathway in which complex molecules are broken down into simpler ones, yielding energy as an additional product of the reaction.

Anabolic

Describes the pathway that requires a net energy input to synthesize complex molecules from simpler ones.

With regard to enzymes, why are vitamins and minerals necessary for good health? Give examples.

Most vitamins and minerals act as cofactors and coenzymes for enzyme action. Many enzymes requires the binding of certain cofactors or coenzymes to be able to catalyze their reactions. Since enzymes catalyze many important reactions, it is critical to obtain sufficient vitamins and minerals from diet and supplements. Vitamin C (ascorbic acid) is a coenzyme necessary for the action of enzymes that build collagen.

Two molecules of ATP and two molecules of __________ are formed for every glucose molecule that is broken down.

NADH

Heat energy

The energy transferred from one system to another that is not work.

Allosteric inhibition

The mechanism for inhibiting enzyme action in which regulatory molecule binds to a second site (not the active site) and initiates a conformation change in the active site, preventing binding with the substrate

Chemiosmosis

The movement of hydrogen ions down their electrochemical gradient across a membrane through ATP synthase to generate ATP.

We inhale oxygen when we breathe and exhale carbon dioxide. What is the oxygen used for and where does the carbon dioxide come from?

The oxygen we inhale is the final electron acceptor in the electron transport chain and allows aerobic respiration to proceed, which is they most efficient pathway for harvesting energy in the form of ATP from food molecules. The carbon dioxide we breathe out is formed during the citric acid cycle when the bonds in carbon compounds are broken.

Gylcolysis

The process of breaking glucose into two three-carbon molecules with the production of ATP and NADH

ATP

(adenosine triphosphate) the cell's energy currency.

How many ATP molecules are produces from the glycolysis of one six-carbon glucose?

2 net ATP, 4 are produced.

Why is there a net gain of only two ATP molecules in the gylcolysis of one six-carbon glucose?

4 are produces, but 2 are used for ADP + P; is a net gain of 2 ATP/

Competitive inhibition

A general mechanism of enzyme activity regulation in which a molecule other than enzymes's substrate is able to bind the active site and prevent the substrate itself from binding, thus inhibiting the overall rate or reaction for the enzyme.

Noncompetitive inhibition

A general mechanism of enzyme activity regulation in which a regulatory molecule binds to a site other than the active site and prevents the active site from binding the substrate; thus the inhibitor molecule does not compete with the substrate for the active site; allosteric inhibition is a form of noncompetitive inhibition.

Feedback inhibition

A mechanism of enzyme activity regulation in which the product of a reaction or the final product of a series of sequential reactions inhibits an enzyme for an earlier step in the reaction series

ATP synthase

A membrane-embedded protein complex that regenerates ATP from ADP withe energy from protons diffusing through it.

Substrate

A molecule on which the enzyme acts

Enzyme

A molecule that catalyzes a biochemical reaction

Citric acid cycle

A series of enzyme-catalyzed chemical reactions of central importance in all living cells that harvests the energy in carbon-carbon bonds of sugar molecules to generate ATP; the citric acid cycle is an aerobic metabolic pathway because it requires oxygen in later reactions to proceed.

Electron transport chain

A series of four large, multi-protein complexes embedded in the inner mitochondrial membrane that accepts electrons from donor compounds and harvests energy from a series of chemical reactions to generate a hydrogen ion gradient across the membrane

Explain in your own terms the difference between a spontaneous reaction and one that occurs instantaneously, and what causes this difference.

A spontaneous reaction is one that has a negative ^G and thus releases energy. However, a spontaneous reaction need not occur quickly or suddenly like an instantaneous reaction. It may occur over long periods of time due to a large energy of activation, which prevents the reaction from occurring quickly.

The energy currency used by cells is ________. A. ATP B. ADP C. AMP D. Adenosine

A. ATP

Which of the following fermentation methods can occur in animal skeletal muscles? A. Lactic acid fermentation B. Alcohol fermentation C. Mixed acid fermentation D. Propionic fermentation

A. Lactic acid fermentation

Which of the following is not true about enzymes? A. They are consumed by the reactions they catalyze B. They are usually made of amino acids C. They lower the activation of energy of chemical reactions. D. Each one is specific to the particular substrate(s) to which it binds

A. They are consumed by the reactions they catalyze

Glycolysis is an___________ process because it does not require oxygen.

Anerobic

The cholesterol synthesized by cells uses which component of the glycolytic pathway as a starting point? A. Glucose B. Acetyl CoA C. Pyruvate D. Carbon dioxide

B Acetyl CoA

What do the electrons added to NAD+ do? A. They become part of a fermentation pathway B. They go to another pathway for ATP production C. They energize the entry of the acetyl group into the citric acid cycle D. They are converted into NADP.

B. They go to another pathway for ATP production

Energy is stored long-term in the bonds of ______ and used short-term to perform work from a(n) _____ molecule. A. ATP; glucose B. An anabolic molecule; catabolic C. Glucose; ATP D. A catabolic molecule; anabolic molecule

C. Glucose; ATP

Beta oxidation is _________. A. The breakdown of sugars B. The assembly of sugars C. The breakdown of fatty acids D. The removal of amino groups from amino acids

C. The breakdown of fatty acids

Chemiosmosis involves A. The movement of electrons across the cell membrane B. The movement of hydrogen atoms across a mitochondrial membrane C. The movement of hydrogen ions across a mitochondrial membrane D. The movement of glucose through the cell membrane

C. The movement of hydrogen ions across a mitochondrial membrane

Organisms obtain energy in a process called...

Cellular Respiration

Glycolysis takes place in the __________.

Cytoplasm

Which of the following is not an example of energy transformation? A. Heating up dinner in a microwave B. Solar panels at work C. Formation of static electricity D. None of the above

D. None of the above

The glucose that enters the glycolysis pathway is split into two molecules of ___________. A. ATP B. Phosphate C. NADH D. Pyruvate

D. Pyruvate

ATP is used to provide__________ for cells to do work.

Energy

Alcohol fermentation is found in some bacteria and in humans.

False

Electron transport is the first step in the breakdown of glucose.

False

Fermentation occurs in the mitochondria.

False

The hydrogen necessary in the electron transport chain comes from the splitting of carbon dioxide molecules.

False

In __________, glucose is broken down into pyruvate.

Glycolysis

Both prokaryotic and eukaryotic organisms carry out some form of glycolysis. How does that factor support or not support the assertion that glycolysis is one of the oldest metabolic pathways?

If glycolysis evolved relatively late, it likely would not be as universal in organisms as it is. It probably evolved in very primitive organisms and persisted, with the addition of other pathways of carbohydrate metabolism that evolved later.

Does physical exercise to increase muscle mass involve anabolic and/or catabolic processes? Give evidence for your answer.

Physical exercise involves both anabolic and catabolic processes. Body cells break down sugars to provide ATP to do the work necessary for exercise, such as muscle contractions. This is catabolism. Muscle cells also must repair muscle tissues damaged by exercise by building new muscle. This is anabolism.

acetyl CoA

The combination of an acetyl group derived from pyruvic acid and coenzyme A which is made from pantothenic acid (a B-group vitamin)

Bioenergetics

The concept of energy flow through living systems

Thermodynamics

The science of the relationship between heat, energy, and work.

Fermentation

The steps that follow the partial oxidation of glucose via glycolysis to regenerate NAD+; occurs in the absence of oxygen and uses an organic compound as the final electron acceptor.

Kinetic energy

The type of energy associated with objects in motion

Potential energy

The type of energy that refers to the potential to do work

Anaerobic cellular respiration

The use of an electron acceptor other than oxygen to complete metabolism using electron transport-based chemiosmosis.

Would you describe metabolic pathways as inherently wasteful or inherently economical, and why?

They are very economical. The substrates, intermediates, and products move between pathways and do so in response to finely tuned feedback inhibition loops that keep metabolism overall on an even keel. Intermediates in one pathway may occur in another, and they can move from one pathway to another fluidly in response to the needs of the cell.

Cellular respiration in eukaryotes is slightly more efficient than in prokaryotes.

True

Skeletal muscle produces lactic acid when the body cannot supply enough oxygen.

True

The Krebs cycle is sometimes called the TCA cycle or the citric acid cycle.

True

The anaerobic pathway that follows glycolysis is the absence of oxygen is fermentation.

True

The two pyruvate molecules formed during glycolysis result in two, turns of the Krebs cycle.

True

When muscle cells run out of oxygen, what happens to the potential for energy extraction from sugars and what pathways do the cell use?

Without oxygen, oxidative phosphorylation and the citric acid cycle stop, so ATP is no longer generated through this mechanism, which extracts the greatest amount of energy from a sugar molecule. In addition, NADH accumulates, preventing glycolysis from going forward because of an absence of NAD+. Lactic acid fermentation uses the electrons in NADH to generate lactic acid from pyruvate, which allows glycolysis to continue and this a smaller amount of ATP can be generated by the cell.

Active site

a specific region on the enzyme where the substrate binds

Activation energy

the amount of initial energy necessary for reactions to occur

Oxidative phosphorylation

the production of ATP by the transfer of electrons down the electron transport chain to create a proton gradient that is used by ATP synthase to add phosphate groups to ADP molecules.