Chapter 8: Harvesting Energy: Glycolysis and Cellular Respiration

Which of the following is true for one glucose molecule? a. fermentation produces two ATP b. glycolysis followed by fermentation nets four ATP c. ethanol is one end product of glycolysis d. the overall equation for photosynthesis is the reverse of that for aerobic glucose breakdown

d

fermentation a. regenerates NADH b. follows cellular respiration when oxygen is lacking c. generates additional ATP after glycolysis d. uses pyruvate as its substrate

d

Yeasts in bread dough and alcoholic beverages use a type of fermentation the generates __________ and _________. Muscles pushed to their limit use ________ fermentation. Which form of fermentation is used by microorganisms that produce yogurt, sour cream, and sauerkraut? _________

ethanol (alcohol), carbon dioxide; lactic acid; lactate fermentation

the complete breakdown of glucose in the presence of oxygen occurs in two major stages:________ and _______. the first of these stages occurs in the __________ of the cell, and the second stage occurs in organelles called ___________. Conditions in which oxygen is present are described as ________.

glycolysis, cellular respiration; cytosol, mitochondria; aerobic

glycolysis

reactions, carried out in the cytoplasm, that break down glucose into 2 molecule of pyruvic acid, producing two ATP molecules; does not require oxygen but can proceed when oxygen is present

matrix

the fluid contained within the inner membrane of the mitochondrion

intermembrane space

the fluid-filled space between the inner and outer membranes of a mitochondrion

cellular respiration

the oxygen-requiring reactions, occurring in the mitochondria, that break down the end products of glycolysis into carbon dioxide and water while capturing large amount of energy as ATP

aerobic

using oxygen

Starting with glucose (C6H12O6), write the overall equation for the glucose breakdown in the presence of oxygen, compare this to the overall equation for photosynthesis, and explain how the energy components of the equation differ.

with oxygen: C6H12O6<---- ?6CO2+6H2O+ATP (chemical energy) photosynthesis: 6CO2+6H2O+ light energy-----> C6H12O6+6O2 Each equation is essentially the reverse order of the other. Photosynthesis captures solar energy in molecules such as glucose, synthesized from CO2 and H2O. Aerobic glucose breakdown releases CO2 and H2O from glucose. The energy of sunlight captured during photosynthesis is released during the breakdown of glucose and captured in ATP. Heat energy is lost in both these metabolic pathways

anaerobic

without oxygen

Outline the two major stages of glycolysis. How many ATP molecules (overall) are generated per glucose molecule during glycolysis? Where in the cell does glycolysis occur?

(glycolysis image in notes) During the energy investment stage, glucose is rearranged and activated (by adding one phosphate group and some of the energy from each of the two ATP's), producing fructose bisphosphate. During the energy- harvesting stage, fructose bisphosphate is split into 2 G3P molecules, each retaining one phosphate. Each G3P is then converted to pyruvate, and energy is captured in two ATP's and 2 NADHs(one from each G3P). Glycolysis occurs in the cytosol.

Draw and label a mitochondrion, and explain how each structure relates to its function.

(imagine in notes) The inner mitochondrial membrane encloses the matrix, where enzymes for the krebs cycle are localized. Embedded in this membrane are the electron transport chain molecules that allow transfer of high-energy electrons from the Krebs cycle and glycolysis and controlled energy release that is used to pump H+ into the intermembrane space. This space encloses a high concentration of H+. The intermembrane also contains H+ channels linked to ATP synthase that capture energy in ATP and H+ flows through the channels down its concentration gradient

Compare the structure of chloroplasts to that of mitochondria, and describe how the similarities in structure relate to similarities in function.

Chloroplasts and mitochondria are both large, membrane enclosed organelles with addition inner membranes where important related reactions occur. Both chloroplasts and mitochondria have ETCs embedded in their inner membranes; the ETC pumps H+ into compartments formed by inner membranes (chloroplasts: interior of the thylakoid; mitochondria: intermembrane compartment). Both use the H+ gradient to generate ATP by chemiosmosis.

What molecule is the end product of glycolysis? How are the carbons of this molecule used in stage 1 of cellular respiration? In what form is most of the energy from the Krebs cycle captured?

Glycolysis produces 2 pyruvate molecules as end products. During stage 1 of cellular respiration, one carbon from pyruvate is released as CO2 during the formation of acetyl CoA. Then during the Krebs cycle, acetyl CoA is broken down, releasing two more molecules of CO2. Most of the energy captured during the Krebs cycle is in the high-energy electron carriers of NADH and FADH2.

The cyclic portion of the cellular respiration is called the __________ cycle. The molecules that enters this cycle is _________. How many ATP molecules are generated by this cycle per molecule of glucose? _________ What types of high-energy electron-carrier molecules are generated during the cycle? ___________ and __________

Krebs; acetyl CoA; two; NADH, FADH2

Why is oxygen necessary for cellular respiration to occur?

Oxygen is necessary for cellular respiration because oxygen acts as the final acceptor for the electron transport chain. Without oxygen, the transfer f high-energy electrons through the ETC would stop, the hydrogen ion gradient would dissipate, and ATP formation would cease.

Describe the electron transport chain and the process of chemiosmosis

The inner membrane of a mitochondrion has many copies of an electron transport chain (ETC), consisting of a series of electron transfer molecules. The high-energy electron carriers formed during glycolysis and the Krebs cycle deposit their electrons in the ETC. As the electrons pass through the ETC, energy is released in stages and is used to pump H+ ions across the inner membrane from the matrix to the intermembrane space. This creates an H+ gradient. during the process of chemiosmosis, H+ flows down its concentration gradient through the channel enzyme ATP synthase, which captures some of this energy to drive ATP synthesis

The portion of glucose breakdown that produces the most ATP is a. chemiosmosis b. glycolysis c. the Krebs cycle d. fermenation

a

Krebs cycle

a cyclic series of reactions, occurring in the matrix of mitochondria, in which the acetyl groups from the pyruvic acids produced by the formation of ATP and electron carriers; also called the citric acid cycle

chemiosmosis

a process of ATP generation in chloroplasts and mitochondria The movement of electrons down and ET system is used to pump H+ ions across a membrane, building up a gradient of H+ ion, the hydrogen ions diffuse back across the membrane through the ports of ATP synthesizing enzymes; the energy of their movement down their concentration gradient drive ATP synthesis

electron transport chain (ETC)

a series of electron carrier molecules, found in thylakoid membranes of chloroplasts and the inner membrane of mitochondria, that extract energy from electrons and generate ATP or other energetic molecules

alcoholic fermentation

a type of fermentation in which pyruvate is converted to ethanol (a type of alcohol) and carbon dioxide, using hydrogen ions and electrons from NADH; the primary function of alcoholic fermentation is to regenerate NAD+ (from NADH) so that glycolysis can continue under anaerobic conditions

nicotinamide adenine dinucleotide (NAD+or NADH)

an electron carrier molecule produced in the cytoplasmic fluid by glycolysis and in the mitochondrial matrix by the Krebs cycle; subsequently donates electrons to the electron transport chain

flavin adenine dinucleotide (FAD or FADH2)

an electron-carrier molecule produced in the mitochondrial matrix by the Krebs cycle; subsequently donates electrons to the electron transport chain

mitochondrion (plural, mitochondria)

an organelle, bounded by two membranes, that is the site of the reactions of aerobic metabolism

fermentation

anaerobic reactions that convert the pyruvic acid produced by glycolysis into lactic acid or alcohol and CO2, using hydrogen ions and electrons from NADH; the primary function of fermentation is to regenerate NAD+ so that glycolysis can continue under anaerobic conditions

lactic acid fermentation

anaerobic reactions that convert the pyruvic acid produced by glycolysis into lactid acid, using hydrogen ions and electrons from NADH; the primary function of lactic acid fermentation is to regenerate NAD+ so that glycolysis can continue under anaerobic cond

Conditions in which oxygen is absent are described as ________. Some microorganisms break down glucose in the absence of oxygen using __________, which generates only _________ molecules of ATP. This process is followed by _________, in which no more ATP is produced, but the electron-acceptor molecule________ is regenerated so it can be used in further glucose breakdown.

anaerobic; glycolysis, two; fermentation, NAD+

ATP synthase enzymes are located in the a. cytosol b. inner mitochondrial membrane c. intermembrane space d. mitochondrial matrix

b

Which of the following is produced in the intermembrane space of mitochondria? a. ATP b. a high concentration of H+ c. NADH and FADH2 d. acetyl CoA

b

What role to the following play in breaking down and harvesting energy from glucose: glycolysis, cellular respiration, chemiosmosis, fermentation, and the electron acceptors NAD+ and FAD?

glycolysis: a six-carbon glucose is split into two three-carbon pyruvate molecules, sotring ATP and the high-energy electron carrier HADH. Under aerobic conditions, cellular respiration breaks down the pyruvate, capturing its energy in ATP and the high-energy electron carries NADH and FADH2. Chemiosmosis: generates ATP using energy from hydrogen ion gradient, which in turn was created by the electron transport chain using the energy released by NADH and FADH2. Under anaerobic conditions, fermentation follows glycolysis and regenerates NAD+ from NADH, which means NAD+ is available to allow glycolysis to continue. NAD+ and FAD serve as electron accpetors, forming NADH and FADH2. NADH carries high-energy electrons released during glycolysis and both NADH and FADH2 carry high-energy electrons from stage 1 of cellular respiration to the electron transport chain.

During cellular respiration, the electron transport chain pumps H+ out of the mitochondrial _________ into the _________, producing a _________ of H+. The ATP produced by cellular respiration is generated by a process called _________. ATP is generated as H+ travels through membrane channels within __________.

matrix, intermembrane space, concentration gradient; chemiosmosis; ATP synthase