Energy Flow and Cellular Respiration

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Questions and Answers

What is the ultimate source of energy for organisms?

Photosynthesis

Chemical Bonds

Organic Molecules

The Sun (correct)

During which process are electrons removed from organic molecules to obtain energy?

Electrolysis

Combustion

Reduction

Oxidation (correct)

What is the role of electron carriers like NAD+ in cellular respiration?

To capture light energy

To produce lactic acid

To transport electrons (correct)

To store excess energy

What is the main product of the aerobic oxidation of glucose?

ATP Signup and view all the answers

In the context of cellular respiration, what occurs to energy levels as electrons move from donor to acceptor molecules?

Energy decreases Signup and view all the answers

Which process is NOT a stage of cellular respiration?

Light-dependent reactions Signup and view all the answers

What type of bond connects the carbon-hydrogen in glucose, making it a good energy source?

Non-polar covalent bond Signup and view all the answers

What is the primary function of the citric acid cycle in cellular respiration?

To oxidize acetyl-CoA and produce energy carriers Signup and view all the answers

What is one function of fermentation in the absence of oxygen?

It converts NADH back to NAD+. Signup and view all the answers

Which type of organism cannot survive in the presence of oxygen?

Strict anaerobes Signup and view all the answers

Which of the following is a reactive oxygen species (ROS)?

Hydrogen peroxide Signup and view all the answers

In anaerobic respiration, which of the following is commonly used as an electron acceptor?

Sulphate Signup and view all the answers

What is the efficiency percentage of the energy transfer process as mentioned?

30-35% Signup and view all the answers

What is the result of one molecule of glucose undergoing glycolysis?

2 ATP, 2 NADH, 2 pyruvate Signup and view all the answers

During which process is NADH produced in cellular respiration?

Krebs cycle and glycolysis Signup and view all the answers

What occurs during the conversion of pyruvate to acetyl-CoA?

CO2 is released and NADH is produced Signup and view all the answers

What drives the synthesis of ATP in oxidative phosphorylation?

Proton gradient across the membrane Signup and view all the answers

Which step in glycolysis is regulated by phosphofructokinase?

Phosphorylation phase Signup and view all the answers

What type of phosphorylation occurs in glycolysis to produce ATP?

Substrate-level phosphorylation Signup and view all the answers

In terms of electron carriers, what are the products of the citric acid cycle?

NADH, FADH2, and ATP Signup and view all the answers

Where does glycolysis occur within the cell?

Cytosol Signup and view all the answers

What is the primary function of ATP synthase in cellular respiration?

To synthesize ATP using a proton gradient Signup and view all the answers

Which of the following is true regarding the potential energy of pyruvate compared to glucose?

Pyruvate has less potential energy than glucose Signup and view all the answers

What is produced during the oxidation of each acetyl group in the citric acid cycle?

2 CO2, 1 NADH, 1 ATP, 1 FADH2 Signup and view all the answers

Which component acts as the final electron acceptor in the respiratory electron transport chain?

O2 Signup and view all the answers

What role does ATP synthase play in the process of oxidative phosphorylation?

It catalyzes ATP synthesis using H+ gradient energy. Signup and view all the answers

Which statement correctly describes the efficiency of cellular respiration when using the H+ gradient only for ATP production?

Efficiency exceeds 30%. Signup and view all the answers

During the citric acid cycle, what is generated through substrate-level phosphorylation?

ATP Signup and view all the answers

What is the approximate ATP yield from 1 NADH molecule?

2.5 ATP Signup and view all the answers

What is the primary function of the electrochemical gradient created during oxidative phosphorylation?

To provide a source of proton motive force for ATP synthesis. Signup and view all the answers

How many CO2 molecules are generated from one pyruvate during the citric acid cycle?

2 CO2 Signup and view all the answers

Study Notes

Energy Flow

Sun is the ultimate source of energy.
Photosynthesis captures light energy and converts it into chemical energy in complex organic molecules.
Organic molecules like glucose and gasoline have an abundance of carbon-hydrogen bonds, which makes them good energy sources due to the high energy levels of electrons in these bonds.
When electrons move towards the atomic nucleus, energy is released.

Cellular Respiration

Organisms obtain energy by oxidizing organic molecules produced by photosynthesis in a series of reactions.
Energy released in oxidations is captured in ATP.
Cellular respiration is a controlled combustion process that is efficient in energy transfer.
Electrons lose energy as they pass from donor to acceptor molecules, releasing free energy that can be used for work.

Electron Carriers

Electron carriers, specifically NAD+, carry energy through cellular respiration.
Dehydrogenases are enzymes that remove electrons from molecules and transfer them to NAD+, reducing it to NADH.

Cellular Respiration: 3 Stages

Glycolysis: Glucose is converted into two pyruvate molecules by oxidation and removal of electrons, producing ATP and NADH.
Citric Acid Cycle: Pyruvate is oxidized to Acetyl-CoA, which enters the cycle and is further oxidized to carbon dioxide, producing ATP, NADH, and FADH2.
Electron Transport and Chemiosmosis: NADH and FADH2 from glycolysis and the citric acid cycle are oxidized, releasing electrons that pass along the electron transport chain to oxygen, which is the final electron acceptor. This process drives the synthesis of ATP.

Glycolysis

Glycolysis is a 10-step process that occurs in the cytosol.
Glucose is oxidized to two pyruvate molecules, producing 2 ATP, 2 NADH, and 2 pyruvate.
The regulation of glycolysis is controlled by specific enzymes such as phosphofructokinase.

ATP Production

ATP molecules are generated in glycolysis and the citric acid cycle by substrate-level phosphorylation.
This process involves an enzyme-catalyzed transfer of a phosphate group from a substrate molecule to ADP.

Pyruvate Oxidation

Takes place in the mitochondrial matrix.
Pyruvate is oxidized to acetyl groups, producing 1 acetyl group, 1 NADH, and 1 CO2 for each pyruvate molecule.
Acetyl groups are attached to coenzyme A, forming Acetyl-CoA, which is then delivered to the citric acid cycle.

Citric Acid Cycle

An 8-step cycle that completely oxidizes acetyl groups to CO2.
Electrons are removed in oxidation reactions and transferred to NAD+ or FAD.
Produces 2 CO2, 1 ATP, 3 NADH, and 1 FADH2 per acetyl group.

Electron Transport Chain

Located in the inner mitochondrial membrane.
Electrons are passed from NADH and FADH2 to oxygen through a series of protein complexes and mobile carriers.
The energy released from electron transfer is used to pump protons across the membrane, creating a proton gradient.

Oxidative Phosphorylation and Chemiosmosis

ATP synthase utilizes the energy stored in the proton gradient to generate ATP.
The proton-motive force drives the rotation of the ATP synthase motor, which catalyzes ATP synthesis.

Efficiency of Cellular Respiration

Cellular respiration is about 30% efficient in utilizing the energy released from glucose oxidation.
The H+ gradient is typically used for ATP production.

Fermentation

Anaerobic process that occurs in the cytosol.
Electrons from NADH are delivered to organic acceptor molecules, regenerating NAD+.
Pyruvate is reduced, and glycolysis continues in the absence of oxygen.

Anaerobic Respiration

Found in some prokaryotes.
Electron transport chains are located on internal membrane systems.
Electron acceptors include sulfate, nitrate, and ferric ions.

Oxygen and Cellular Respiration

Oxygen is the final electron acceptor in aerobic respiration.
It is vital for oxidative phosphorylation and ATP production.

Reactive Oxygen Species (ROS)

Oxygen is inherently dangerous and can lead to the formation of reactive oxygen species (ROS).
ROS are strong oxidizing agents that can damage cells and contribute to various diseases.
Antioxidant defense mechanisms, including enzymes like superoxide dismutase and catalase, and non-enzymes like antioxidants (vitamin C and vitamin E) protect against ROS damage.

Control of Cellular Respiration

Cellular respiration is regulated by various mechanisms, including allosteric activation and feedback inhibition.
These mechanisms ensure that energy production is balanced with the body's needs.

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Description

Explore the dynamic processes of energy flow through photosynthesis and cellular respiration. This quiz covers the roles of organic molecules, energy capture in ATP, and the function of electron carriers like NAD+. Test your understanding of how energy transformations power biological systems.