ATP and Energy Metabolism Quiz

ATP and Energy Metabolism

• ATP (adenosine triphosphate) is the primary energy currency of cells, providing energy for various cellular processes.
• ATP is composed of adenine, a five-carbon sugar (ribose), and three phosphate groups.
• ATP plays a crucial role in linking exergonic (energy-releasing) and endergonic (energy-requiring) reactions, allowing energy transfer between them.
• During exergonic reactions, ATP is generated; during endergonic reactions, ATP is broken down to ADP (adenosine diphosphate).
• ADP is the primary recipient of energy from ATP breakdown, allowing for recycling back into ATP.
• The primary role of ADP is to accept energy from ATP breakdown to drive endergonic reactions.

Cellular Respiration and Energy Production

• The primary energy source for living organisms is the breakdown of glucose and other nutrients via cellular respiration.
• Cellular respiration is the process where organisms use oxygen to convert fuel into chemical energy, producing ATP as a byproduct.
• Anaerobic respiration is a type of respiration that generates energy in the absence of oxygen by breaking down sugars.
• The energy required for reactions not releasing energy is called activation energy.

ATP Synthesis and Phosphorylation

• ATP synthesis involves combining ADP with a phosphate molecule, a process called phosphorylation.
• The energy released from breaking a molecular bond in ATP comes from the energy stored in phosphate bonds.
• ATP is the premier energy molecule in living cells, powering various cellular processes.

The ATP-ADP Cycle

• The ATP-ADP cycle describes the continuous conversion of ATP to ADP and back again.
• ATP releases energy when a phosphate group is removed, converting it to ADP.
• The released energy powers cellular processes.
• ADP can be re-phosphorylated to ATP using energy from various sources like cellular respiration or photosynthesis.

Photosynthesis: Light-Dependent Reactions

• Chlorophyll and other pigments absorb light energy.
• Absorbed energy excites electrons in the pigments.
• Excited electrons move through an electron transport chain, generating ATP and NADPH.
• Water is split, releasing oxygen as a byproduct.

Photosynthesis: Products of the Light-Dependent Reactions

• ATP is a primary energy carrier used in the Calvin Cycle.
• NADPH is a reducing agent used in the Calvin Cycle.
• Oxygen is a byproduct released into the atmosphere.

The Calvin Cycle

• The Calvin cycle is the light-independent stage of photosynthesis.
• The cycle uses energy from ATP and NADPH's reducing power to convert carbon dioxide into sugar.
• Melvin Calvin and his team at the University of California, Berkeley, discovered the Calvin cycle.
• The Calvin cycle is also known as the Calvin-Benson cycle or the C3 cycle.
• The cycle is the main process by which plants fix carbon dioxide into organic compounds, specifically glucose.

G3P (Glyceraldehyde 3-phosphate)

• G3P is a three-carbon sugar produced in the Calvin Cycle.
• G3P is used to synthesize other sugars and organic molecules.

Carbon Fixation

• Carbon fixation is the process of incorporating CO2 into an organic material.

RuBisCo

• RuBisCo (ribulose-1,5-bisphosphate carboxylase/oxygenase) is an enzyme responsible for attaching CO2 to a five-carbon sugar molecule, ribulose bisphosphate, in the Calvin Cycle.

Six-Carbon Sugar: Fate after Carbon Fixation

• The resulting six-carbon sugar is unstable and quickly breaks down into two molecules of 3-phosphoglycerate (3-PGA).

NADPH Role in the Calvin Cycle

• NADPH provides electrons to reduce 3-PGA into G3P, used in glucose and other organic molecule synthesis.

G3P Fate: The Calvin Cycle

• Most G3P molecules regenerate the five-carbon sugar (ribulose bisphosphate) to continue the cycle.
• A portion of G3P is used to create glucose and other organic molecules, vital for plant growth and energy storage.

ADP and NADP+ Fate after the Calvin Cycle

• ADP and NADP+ formed during the Calvin Cycle return to the light-dependent reactions to be re-energized, ensuring sufficient energy carrier supply.

Rubisco Function

• Rubisco is the most abundant enzyme on Earth, crucial for the Calvin Cycle.
• Rubisco has a dual role in fixing CO2 and oxygen.
• Rubisco's affinity for oxygen can limit plant growth.

Product of Carbon Fixation

• The initial product of carbon fixation is an unstable six-carbon sugar, which breaks down into two molecules of 3-phosphoglycerate (3-PGA).

Cellular Respiration Overview

• Cellular respiration produces ATP by breaking down organic compounds.
• Both autotrophs and heterotrophs utilize cellular respiration.

Photosynthesis Relationship

• Photosynthesis converts light energy to chemical energy in autotrophs.
• Products of photosynthesis serve as reactants in cellular respiration, highlighting their interdependence.

Breakdown of Organic Compounds

• The breakdown of organic compounds releases energy, primarily used to produce ATP.

Stages of Cellular Respiration

Cellular respiration involves glycolysis, the Krebs cycle, and the electron transport chain.

• Glycolysis converts glucose to pyruvic acid, yielding ATP and NADH.
• The Krebs cycle breaks down acetyl CoA, producing ATP, CO2, and electron carriers.
• The electron transport chain generates ATP via an electron transport pathway.

Glycolysis Steps

• In glycolysis, glucose is phosphorylated into glucose-6-phosphate, split into two 3-carbon molecules (G3P), and then G3P loses electrons, transforming NAD+ into NADH.
• Phosphates are removed, generating pyruvic acid and producing ATP from ADP.

Anaerobic vs. Aerobic Conditions

• In the absence of oxygen, pyruvic acid undergoes fermentation – a process that regenerates NAD+.
• In the presence of oxygen, pyruvic acid enters aerobic respiration.

Fermentation Types

• Lactic acid fermentation converts pyruvic acid to lactic acid (e.g., in muscle cells during strenuous exercise).
• Alcoholic fermentation converts pyruvic acid to ethyl alcohol and releases CO2 (e.g., in plant cells and unicellular organisms).

Krebs Cycle and Electron Transport Chain

• Aerobic respiration involves the Krebs cycle and the electron transport chain (ETC).
• The Krebs cycle breaks down acetyl CoA, releasing CO2, hydrogen atoms, and ATP.
• The electron transport chain utilizes oxygen as the final electron acceptor, generating significant ATP.

Final Electron Acceptors and Energy Yield

• The final electron acceptor in the ETC is oxygen.
• Aerobic respiration generates significantly more ATP than glycolysis.

Energy Efficiency

• Glycolysis efficiency is measured by the energy needed to create ATP over glucose oxidation energy.
• The overall cellular respiration efficiency shows how effectively glucose is converted to usable energy.

Phases of Cellular Respiration

• Glycolysis, the Krebs cycle, and the electron transport chain are the three main phases of cellular respiration.

Location of Processes

• Glycolysis occurs in the cytoplasm.
• The Krebs cycle takes place in the mitochondrial matrix.
• The electron transport chain is in the inner mitochondrial membrane.

ATP Production

• Glycolysis yields a net gain of 2 ATP.
• The Krebs Cycle generates 2 ATP.
• The electron transport chain produces up to 34 ATP.

Byproducts of Cellular Respiration

• Carbon dioxide is a byproduct of the Krebs cycle.
• Water is a byproduct of the electron transport chain.

Substrates in Cellular Respiration

• Glucose is a substrate for glycolysis.
• Oxygen is a substrate for the electron transport chain.

NADH and FADH2

• Each NADH molecule can produce about 3 ATP in the electron transport chain.
• Each FADH2 molecule yields approximately 2 ATP.

Enzyme Deficiency Impact

• Missing or defective enzymes at any step can halt cellular respiration beyond that point.

Anaerobic Conditions

• In the absence of oxygen, pyruvic acid accepts high-energy electrons from NADH.

Fermentation Reactions

• Yeast fermentation produces ethanol, CO2, 2 ATP, and heat from glucose.
• Lactic acid fermentation produces lactate, 2 ATP, and heat from glucose.