Biology Chapter: Energy and Reactions

Kinetic Energy

• Kinetic energy is specifically related to the speed and mass of an object. It plays a crucial role in understanding various physical phenomena and is essential in fields such as mechanics and engineering.

• Energy of motion

• The faster an object moves, the greater its kinetic energy

• Examples: a moving car, a flowing river, a bouncing ball

Energy Transformation Efficiency

• Energy transformations are never 100% efficient
• Some energy is always lost as heat
• Heat is a form of energy that is difficult to utilize for other purposes

ATP Structure and Function

• Adenosine triphosphate (ATP) is the primary energy currency of cells
• Composed of an adenine base, a ribose sugar, and three phosphate groups
• The bonds between the phosphate groups store energy, which is released when a phosphate group is broken off

Catabolic Reactions

• Break down complex molecules into simpler ones
• Release energy
• Examples: digestion of food, cellular respiration

Anabolic Reactions

• Build up complex molecules from simpler ones
• Require energy
• Examples: protein synthesis, DNA replication

Enzyme Function

• Biological catalysts that speed up chemical reactions without being consumed in the process
• Enzymes lower the activation energy of a reaction, making it easier for the reaction to occur
• They do this by providing an alternative reaction pathway with a lower activation energy

Competitive vs Noncompetitive Inhibition

• Competitive inhibition occurs when an inhibitor binds to the active site of an enzyme, preventing the substrate from binding
• Noncompetitive inhibition occurs when an inhibitor binds to a site on the enzyme other than the active site, changing the enzyme's shape and making it less active

Endergonic Reactions

• Require energy input
• Products have more energy than reactants
• Graph: The products are higher than the reactants on the y-axis

Exergonic Reactions

• Release energy
• Products have less energy than reactants
• Graph: The products are lower than the reactants on the y-axis

Activation Energy Location on Graphs

• The activation energy is the difference in energy between the reactants and the transition state
• On both endergonic and exergonic reaction graphs, the activation energy is the vertical distance from the reactant level to the peak of the curve

Feedback Inhibition

• A metabolic pathway's product can inhibit earlier steps, regulating pathways and preventing overproduction, e.g., ATP inhibits glucose breakdown.

Cellular Respiration Reaction

• Reaction: C6H12O6 + 6O2 → 6CO2 + 6H2O + energy (ATP)
• Catabolic reaction
• Occurs in the cytoplasm and mitochondria

Plants and Cellular Respiration

• Plants do undergo cellular respiration. They require ATP for normal cell function.
• They produce glucose via photosynthesis, and use that as a source of energy in cellular respiration

Redox Reactions and Cellular Respiration

• Redox reactions are reactions where electrons are transferred from one molecule to another
• Oxidation is the loss of electrons
• Reduction is the gain of electrons
• Redox reactions are critical in cellular respiration
• They occur in the electron transport chain

Oxidation

• Loss of electrons
• Often accompanied by the loss of hydrogen atoms
• Increasing oxidation state

Glycolysis

• Occurs in the cytoplasm
• Glucose is broken down into two pyruvate molecules
• Produces 2 ATP and 2 NADH

Krebs Cycle (Citric Acid Cycle)

• Occurs in the mitochondrial matrix
• Pyruvate is further oxidized to carbon dioxide
• Produces 2 ATP, 6 NADH, and 2 FADH2

Electron Transport Chain

• Occurs in the inner mitochondrial membrane
• Electrons from NADH and FADH2 are passed along a series of electron carriers, releasing energy
• Energy is used to pump protons across the membrane, creating a proton gradient
• Protons flow back across the membrane through ATP synthase, producing ATP
• Produces approximately 32 ATP

NAD and FAD in Cellular Respiration

• NAD+ and FAD are electron carriers
• They accept electrons and become reduced (NADH and FADH2)
• Then they donate electrons to the electron transport chain

Oxygen's Role in Cellular Respiration

• Oxygen is the final electron acceptor in the electron transport chain
• It combines with protons and electrons to form water (H2O)
• This process is essential for maintaining the proton gradient that drives ATP production

Lactic Acid Fermentation

• Occurs in the absence of oxygen
• Pyruvate is converted to lactate
• Produces very little ATP
• Occurs in muscle cells during intense exercise

Alcoholic Fermentation

• Occurs in the absence of oxygen
• Pyruvate is converted to ethanol and carbon dioxide
• Used by yeast and some bacteria

Cellular Respiration Process

• Glycolysis: Glucose is broken down into pyruvate in the cytoplasm, producing 2 ATP and 2 NADH.
• Krebs Cycle: Pyruvate is further oxidized, producing 2 ATP, 6 NADH, and 2 FADH2 in the mitochondria.
• Electron Transport Chain: Electrons from NADH and FADH2 are passed along a series of carriers in the inner mitochondrial membrane, generating a proton gradient that drives ATP synthesis. The final electron acceptor is oxygen, which forms water.

Photosynthesis Reaction

• Reaction: 6CO2 + 6H2O + light energy → C6H12O6 + 6O2
• Anabolic reaction
• Occurs in the chloroplasts of plant cells

Gas Exchange in Plants

• Gases enter and exit the leaf through tiny pores called stomata
• Carbon dioxide enters for photosynthesis
• Oxygen produced during photosynthesis exits

Photosynthetic Pigments

• Photosynthetic pigments are located in the thylakoid membranes of chloroplasts
• These pigments absorb light energy

Light-Dependent Reactions

• Light energy absorbed by chlorophyll in thylakoid membranes excites electrons, producing ATP and NADPH, while splitting water and releasing oxygen.

Light-Independent Reactions (Calvin Cycle)

• In the chloroplast stroma, carbon dioxide is converted into glucose using ATP and NADPH.

Electron Flow in Photosy

Products of Light-Dependent Reactions

• ATP and NADPH are produced during the light-dependent reactions
• These are sent to the Calvin Cycle to drive the process of carbon fixation

Main Colors for Photosynthesis

• Photosynthesis is mainly driven by red and blue light
• Chlorophyll absorbs most wavelengths of light except for green, which is reflected
• This is why plants appear green