Section 9-2 The Krebs Cycle and Electron Transport

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At the end of glycolysis, how much of the chemical energy in glucose is still unused?

90 %

Because the final stages of cellular respiration require oxygen, they are said to be ________.

aerobic

In the presence of oxygen, how is the pyruvic acid produced in glycolysis used?

it passes to the second stage of cellular respiration, the Krebs cycle

why is the Krebs cycle also known as the citric acid cycle?

citric acid is the first compound formed in this series of reactions

What happens to pyruvic acid during the Krebs cycle?

it is broken down into carbon dioxide in a series of energy extracting reactions

when does the Krebs cycle begin?

when pyruvic acid produced by glycolysis enters the mitochondrion

what happens to each of the 3 carbon atoms in pyruvic acid when it is broken down?

one carbon atom becomes part of a molecule of carbon dioxide. two are joined to a compound called coenzyme A to form acetyl-CoA.

what happens to carbon dioxide produced in breaking down pyruvic acid?

it is released into the air

How is citric acid produced?

Acetyl-CoA adds the 2-carbon acetyl group to a 4-carbon molecule, producing a 6-carbon molecule called citric acid

During the energy extraction part of the Krebs cycle, how many molecules of CO2 are released?

2

What is the energy tally from the 1 molecule of pyruvic acid during the Krebs cycle?

It is 4 NADH, 1 FADH2, and 1 ATP
(molecules)

when electrons join NAD+ and FAD during the Krebs cycle, what do they form?

NADH and FADH2+

Why is the 4-carbon compound generated in the breakdown of citric acid the only permanent compound in the Krebs cycle?

it is regenerated at the end of each complete turn of the cycle

What is the electron transport chain?

a series of proteins in the inner membrane of mitochondira.

what does the electron transport chain use the high-energy electrons from the Krebs cycle for?

to convert ADP into ATP

How does the location of the electron transport chain differ in the eukaryotes and prokaryotes?

In eukaryotes - the chain is composed of a series of proteins located in the inner membrane of the mitochondrion.
In prokaryotes, the chain is in the cell membrane

where does the electron transport chain get the high energy electrons that are passed down the chain?

it gets them from NADH and FADH2 produced in the Krebs cycle

is the following true or False. Hydrogen serves as the final electron acceptor of the electron transport chain.

False

what is the energy of the high energy electrons used for every time two high energy electrons move down the electron transport chain?

their energy is used to transport hydrogen ions across the membrane

what causes the H+ ions in the intermembrane space to move through the channels in the membrane and out into the matrix?

During the ETC H+ ions build up in the intermembrane space, making it POSITIVELY charged. The other side of the membrane, from which the H+ ion have been taken is now NEGATIVELY charged. The charge differences that build up cause the ions to move.

On average how many ATP molecules are produced as each pair of high energy electrons move down the ETC?

3 ATP

High energy electrons from NADH and FADH2 are passed into and along the _______.

Electron transport Chain

Energy from the electrons move down the chain is used to move H+ ions across the ________.

inner membrane

H+ ions build up in the ________________ space, making it ____________ charged and making the matrix negatively charged.

- intermembrane
- Positively

H+ ions move through channels of ____________ in the innermembrane.

ATP synthase

ATP synthase use the energy from the moving ions to combine ADP and phosphate forming high energy _________.

ATP

What is the total number of ATP molecules formed during cellular respiration?

36

Why can 18 times as much ATP be generated from glucose in the presence of oxygen than when oxygen is not available?

when oxygen is not available, the krebs cycle and electron transport chain cannot proceed, and glycolysis produced just two ATP per glucose. Under aerobic conditions, the krebs cycle and electron transport enable the cell to produce 34 ATP molecules per glucose molecule.

what happens to the 62% of the total energy of glucose that is not used to make ATP molecules.

it released as heat

what are the final waste products of cellular respiration?

water and carbon dioxide

what are three sources of ATP a human body uses at the beginning of a race?

ATP already in the muscles, new ATP made by lactic acid and fermentation, cellular repiration

when runners need quick energy for a short race, what source can supply enough ATP for about 90 seconds.

lactic acid fermentation

why does a sprinter have an oxygen debt to repay after the race is over?

lactic acid fermentation produces lactic acid as a byproduct. the only way to get rid of lactic acid is in a chemical pathway that requires extra oxygen

a runner needs more energy for a long race. how does the body generate the necessary ATP?

cellular respiration is the only way to generate a continuing supply of ATP

why are aerobic forms of exercise so beneficial for weight control?

stores of glycogen used in cellular respiration usually last for 15 - 20 minutes. after that, the body begins to break down other stored molecules, including fat for energy.

If photosynthesis is the process that "deposits" energy in a "savings" account. then what is cellular respiration?

it is the process that "withdraws" energy.

how are photosynthesis and cellular respiration opposite in terms of carbon dioxide?

photosynthesis removes carbon dioxide from the atmosphere and cellular respiration puts it back.

how are photosynthesis and cellular respiration opposite in terms of oxygen?

photosynthesis releases oxygen, cellular respiration uses oxygen to release energy from food.

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