AP Bio Unit 3

  • Enzyme Structure

    • The active site interacts with a specific substrate

  • Enzyme-mediated chemical reaction

    • The shape and charge of the substrate must be compatible with the active site

  • Structure and function of enzymes

    • Contribute to the regulation of biological processes

    • Catalyst

    • Lower activation energy

  • Change structure will change function

    • Denaturation

      • Occurs when protein structure is disrupted

      • Cannot catalyze reactions

      • Environmental temperatures and pH outside the normal range

      • Some enzymes can be renatured, allowing to regain activity

  • Environmental pH

    • Alter efficiency of enzyme activity

    • Disrupts hydrogen bonds

    • EQUATION: pH = -log[H+]

  • Concentration of substrates and products

    • Affects the efficiency of reactions

  • Higher environmental temperatures

    • Increase the speed of movement of molecules

    • Increase the frequency of collisions between enzyme and substrate

    • Increase rate of reaction

  • Inhibitors

    • Competitive 

      • Binds reversibly and irreversibly to the active site

    • Noncompetitive 

      • Binds to the allosteric site

      • Changing the activity of the enzyme

  • Living systems require constant input of energy

  • Life does not violate the 2nd law of thermodynamics

    • Energy input 

      • must exceed energy loss to…

        • maintain order 

        • power cellular processes

    • Cellular processes that release energy may be coupled with cellular processes that require energy.

    • Loss of order or energy flow results in death

  • Energy-related pathways in biological systems

    • are sequential to allow for a more controlled and efficient transfer of energy 

    • A product of a reaction in a metabolic pathway is generally the reactant for the next step in the pathway

  • Organisms capture and store energy for use in biological systems

    • Photosynthesis evolved in prokaryotic organisms

      • prokaryotic (cyanobacterial) photosynthesis produced an oxygenated atmosphere

      • foundation of eukaryotic photosynthesis

  • Light-dependent reactions of photosynthesis in eukaryotes 

    • involve a series of coordinated reaction pathways 

    • capture energy present in light to produce ATP and NADPH, which are essential for the subsequent light-independent reactions.

  • Cells capture energy from light and transfer it to biological molecules for storage and use

    • chlorophylls 

      • absorb energy from light

      • boosting electrons to a higher energy level in photosystems I and II

      • embedded in the internal membranes of chloroplasts 

      • Are connected by the transfer of higher energy electrons through an electron transport chain (ETC).

        • Electrons are transferred between molecules in a sequence of reactions as they pass through the ETC

        • an electrochemical gradient of protons (hydrogen ions) is established across the internal membrane.

          • proton gradient is linked to the synthesis of ATP from ADP and inorganic phosphate via ATP synthase

    • The energy captured in the light reactions and transferred to ATP and NADPH powers the production of carbohydrates from carbon dioxide in the Calvin cycle, which occurs in the stroma of the chloroplast.

  • Fermentation and cellular respiration 

    • Use energy from biological macromolecules to produce ATP. 

    • Are characteristic of all forms of life.

  • In eukaryotes it is 

    • a series of coordinated enzyme-catalyzed reactions 

    • capture energy from biological macromolecules

  • The electron transport chain 

    • transfers energy from electrons in a series of coupled reactions

    • establish an electrochemical gradient across membranes

      • occur in chloroplasts,mitochondria, and prokaryotic plasma membranes.

        • In CR electrons delivered by NADH and FADH2 are passed to a series of electron acceptors as they move toward the terminal electron acceptor, oxygen.

        • In photosynthesis, the terminal electron acceptor is NADP+ 

        • Aerobic prokaryotes use oxygen as a terminal electron acceptor

        • Anaerobic prokaryotes use other molecules

    • The transfer of electrons is accompanied by 

      • formation of a proton gradient across the inner mitochondrial membrane or the internal membrane of chloroplasts with the membrane(s) separating a region of high proton concentration from a region of low proton concentration. 

      • In prokaryotes, the passage of electrons is accompanied by the movement of protons across the plasma membrane.

    • The flow of protons back through membrane-bound ATP synthase by chemiosmosis drives the formation of ATP from ADP and inorganic phosphate. 

      • oxidative phosphorylation in cellular respiration

        • decoupling oxidative phosphorylation from electron transport generates heat

        • This heat can be used by endothermic organisms to regulate body temperature

      • photophosphorylation in photosynthesis

  • Glycolysis 

    • releases energy in glucose to form 

      • ATP from ADP and inorganic phosphate

      • NADH from NAD+

      • Pyruvate

        • transported from the cytosol to the mitochondrion, where further oxidation occurs.

  • Krebs cycle

    • carbon dioxide is released from organic intermediates

    • ATP is synthesized from ADP and inorganic phosphate

    • electrons are transferred to the coenzymes NADH and FADH2

  • electron transport chain

    • electrons extracted in glycolysis and Krebs cycle reactions are transferred by NADH and FADH2

    • in the inner mitochondrial membrane.

    • electrons are transferred between molecules in a sequence of reactions

      • forms an electrochemical gradient of protons (hydrogen ions) across the inner mitochondrial membrane is established

  • Fermentation 

    • allows glycolysis to proceed in the absence of oxygen 

    • produces organic molecules, including alcohol and lactic acid, as waste products

  • The conversion of ATP to ADP releases energy, which is used to power many metabolic processes.

  • Variation 

    • molecular level 

      • ability to respond to a variety of environmental stimuli.

    • number and types of molecules within cells 

      • provides organisms a greater ability to survive and/or reproduce in different environments

  • Examples: types of phospholipids and adaptation to environmental temperatures, types of hemoglobin and oxygen absorption at different developmental stages, different chlorophylls allow plants to exploit different forms of wavelengths for photosynthesis

Enzymes are biological catalysts that speed up chemical reactions by lowering the activation energy needed for those reactions. They have specific active sites that interact with substrates, meaning their structure is crucial for their function. Enzyme activity can be influenced by environmental factors such as temperature and pH, leading to denaturation if conditions are extreme. Enzymes may be inhibited by competitive or noncompetitive inhibitors, which disrupt their activity. Cellular processes rely on energy transfer, which can occur through pathways like glycolysis, the Krebs cycle, and photosynthesis, utilizing ATP and NADPH for energy storage and transfer.