Bioenergetics Reactions Module 4

Module 4: Bioenergetics Reactions

• Bioenergetics is the study of energy in living systems and the organisms that utilize them.
• Energy is required by all organisms.
• Energy can be kinetic or potential.

Kinetic Energy

• Kinetic energy is the energy of motion.
• Examples of kinetic energy include heat and light energy.

Potential Energy

• Potential energy is energy of position.
• Potential energy is stored in chemical bonds.

Two Types of Energy Reactions

• Endergonic reactions:
  • Require a net input of energy.
  • Example: Photosynthesis.
  • The equation for Photosynthesis is: 6CO2 + 6H2O → C6H12O6 + 6O2.
• Exergonic reactions:
  • Release energy.
  • Example: Cellular respiration.
  • The equation for Cellular Respiration is: C6H12O6 + 6O2 → 6CO2 + 6H2O + ATP.

Mitochondria and Chloroplasts

• Mitochondria are sites of cellular respiration, generating ATP by extracting energy from sugars, fats, and other fuels using oxygen.
• Chloroplasts are found in plants and algae, carrying out photosynthesis. They convert light energy into chemical energy.
• Both organelles are enclosed by membranes; mitochondria have two, while chloroplasts also have two.

Mitochondria: Chemical Energy Conversion

• Mitochondria are found in nearly all eukaryotic cells (plants, animals, fungi, and most protists).
• Some cells may have only one large mitochondrion, others have hundreds or thousands.
• Mitochondria are enclosed by two membranes, each a phospholipid bilayer with unique embedded proteins.

2 Membranes of Mitochondria

• Outer Membrane: smooth membrane.
• Inner Membrane: convoluted with infoldings called cristae.
• Intermembrane Space: the narrow region between the inner and outer membranes.
• Mitochondrial Matrix: enclosed by the inner membrane.

Chloroplasts: Capture of Light

• Chloroplasts are a specialized family member of plastids.
• Amyloplasts store amylose, primarily in roots and tubers.
• Other plastids contain pigments, giving fruits and flowers their colors.

Inside Chloroplast

• Thylakoids are interconnected, flattened sacs.
• In some regions, thylakoids are stacked, forming grana.
• The fluid outside the thylakoids is called stroma, which contains chloroplast DNA and ribosomes, along with enzymes.
• Chloroplasts have three compartments: intermembrane space, stroma, and thylakoid space.

Peroxisomes: Oxidation

• Peroxisomes are specialized metabolic compartments bounded by a single membrane.
• They contain enzymes that transfer hydrogen from various substances to oxygen, producing hydrogen peroxide (H₂O₂).
• In the liver, peroxisomes detoxify alcohol and other harmful components by transferring hydrogen from the poisons to oxygen.
• Glyoxysomes are specialized peroxisomes found in fat-storing tissues of plant seeds, initiating the conversion of fatty acids to sugar.

Metabolism

• Metabolism is the sum total of all chemical activities in an organism's cells.
• Two types of metabolism:
  • Anabolic pathways: consume energy (endergonic), building complex molecules from simpler ones. Example: Photosynthesis.
  • Catabolic pathways: release energy (exergonic), breaking down complex molecules into simpler ones. Example: Cellular respiration.

Anabolic and Catabolic Pathways

• Photosynthesis: 6CO2 + 6H2O → C6H12O6 + 6O2
• Cellular Respiration: C6H12O6 + 6O2 → 6CO2 + 6H2O + ATP

Adenosine Triphosphate (ATP)

• ATP structure: adenine, ribose, and a chain of three phosphate groups.
• Three phosphate groups, two with high-energy bonds.
• The last phosphate group (PO₄) contains the most energy.

Breaking the Bonds of ATP

• Process is called phosphorylation.
• Occurs in cells continuously.
• Enzyme ATP-ase weakens and breaks the last PO₄ bond of ATP, releasing energy and free PO₄.

How Does ATP Work?

• Organisms use enzymes to break down glucose (rich in energy) to release its potential energy.
• This energy is trapped and stored in ATP.

How Much ATP Do Cells Use?

• Each cell generates and consumes approximately 10,000,000 ATP molecules per second.

Coupled Reaction - ATP

• Exergonic hydrolysis of ATP is coupled with endergonic dehydration processes by transferring a phosphate group to another molecule.

Hydrolysis of ATP

• ATP + H₂O → ADP + P (exergonic)
• Breaking the bond between the last two phosphate groups releases energy, useful for other biochemical processes

Hydrolysis is Exergonic

Dehydration of ATP

• ADP + P → ATP + H₂O (endergonic)
• The process of adding a phosphate group to ADP to form ATP, requires energy and is known as dehydration.

Dehydration is Endergonic

Explore the fascinating world of bioenergetics, which studies how energy is utilized by living organisms. The quiz covers essential concepts like kinetic and potential energy, as well as the two types of energy reactions: endergonic and exergonic. Test your knowledge of energy reactions and their significance in biological systems.