Biology Chapter 5: The Working Cell Flashcards

Membrane Structure and Transport

• Fluid Mosaic Model: Describes the membrane as a diverse mosaic of protein molecules within a fluid phospholipid bilayer.
• Selective Permeability: Membranes allow some substances to cross while blocking others, essential for cell function.
• Diffusion: Spontaneous movement from a region of higher concentration to one of lower concentration.
• Concentration Gradient: Indicates how the density of a substance varies in space; cells maintain gradients to facilitate movement.
• Passive Transport: Movement of substances across membranes without energy expenditure, relying on concentration gradients.
• Osmosis: Diffusion of water through a selectively permeable membrane.
• Tonicity: Influences whether cells gain or lose water based on surrounding solution concentrations.

Solution Types

• Isotonic: No net water movement as solute concentrations are equal inside and outside the cell.
• Hypotonic: Surrounding solution causes cells to gain water, potentially leading to swelling.
• Hypertonic: Surrounding solution results in water loss from the cell, causing it to shrink.

Cellular Processes

• Osmoregulation: Maintaining solute balance and regulating water gain/loss within cells.
• Facilitated Diffusion: Requires specific transport proteins for substances to move across membranes down their concentration gradients.
• Aquaporins: Specialized transport proteins that enhance water movement across cell membranes.

Active Transport Mechanisms

• Active Transport: Moves substances against their gradient, requiring energy input (ATP).
• Exocytosis: Process of expelling materials from a cell via vesicle fusion with the plasma membrane.
• Endocytosis: Uptake of substances through vesicle formation from the plasma membrane, including types like phagocytosis and pinocytosis.
• Receptor-Mediated Endocytosis: Specific uptake of molecules via vesicles organized around receptor-protein complexes.

Energy Concepts

• Energy: Capacity to perform work or cause change.
• Kinetic Energy: Energy of motion; relates to moving objects.
• Potential Energy: Energy stored due to position or arrangement; includes chemical bonds and gravitational potential.
• Thermodynamics: Study of energy transformations in matter.

Laws of Thermodynamics

• First Law: Energy conservation; energy can’t be created or destroyed, only transformed.
• Entropy: A measure of disorder; increases with energy transformations, mirroring the second law.
• Second Law: Every energy conversion results in increased entropy, implying a reduction in order.

Metabolism and Reactions

• Cellular Respiration: Aerobic breakdown of food to liberate energy usable by cells.
• Metabolism: Total chemical reactions in an organism, encompassing both energy-releasing and energy-consuming pathways.
• Energy Coupling: Utilizes energy from exergonic reactions to fuel endergonic reactions.

ATP and Reactions

• ATP: Main energy currency of cells; provides energy for various biological processes.
• Enzymes: Biological catalysts that accelerate chemical reactions without being consumed.
• Activation Energy: Minimum energy required for reactants to start a chemical reaction.
• Substrate: Specific reactant on which an enzyme acts, with each enzyme having unique substrates.

Enzyme Functionality

• Active Site: Region on an enzyme where substrates bind, critical for catalysis.
• Induced Fit Model: Enzyme dynamically alters its shape upon substrate binding for optimal interaction.
• Cofactors and Coenzymes: Additional nonprotein molecules or organic compounds needed for enzyme activity; vitamins often serve as coenzymes.
• Inhibitors: Molecules that decrease enzyme activity; competitive inhibitors block active sites, while noncompetitive inhibitors alter enzyme structure without engaging active sites.
• Feedback Inhibition: A regulatory mechanism where the end product of a pathway inhibits an enzyme within that pathway, helping maintain homeostasis.