Cell Membrane Structure and Function Quiz

Physiology of Cells and Tissues

• The presentation covers various aspects of cell and tissue physiology.
• Topics include plasma membranes, membrane transport, cell division and apoptosis, cellular aging, cancer, and tissue response to injury.

Contents

• Plasma Membrane: Function, Lipids, Proteins
• Membrane Transport: Passive Transport, Active Transport.
• Cell Division and Apoptosis: Cell division process & programmed cell death.
• Cellular Basis of Aging and Cancer: Aging hypotheses and tumor formation.
• Response to Tissue Injury: Inflammation and repair mechanisms.

Plasma Membrane

• The plasma membrane is composed of a phospholipid bilayer with embedded proteins.
• Phospholipids have polar heads and nonpolar tails.
• It controls what enters and leaves the cell.

Membrane Lipids

• Phospholipids are the major component of the lipid bilayer, forming the membrane.
• Cholesterol contributes to membrane stability and fluidity.
• The bilayer structure allows for various transport mechanisms.

Membrane Proteins

• Membrane proteins are crucial for various cell functions.
• Integral proteins span the lipid bilayer, while peripheral proteins are attached to the surfaces.
• Different protein types have specific roles, including transport, enzymes, and receptors.

Functions of Membrane Proteins

• Attachment proteins bind cells to other cells or extracellular matrix.
• Marker molecules (e.g., glycoproteins) identify cells.
• Receptor proteins receive chemical signals.
• Enzymes catalyze specific reactions.
• Transport proteins facilitate movement of molecules across the membrane.

Major Classes of Transport Proteins

• Channel Proteins: Leak channels are always open, while gated channels open or close in response to stimuli (e.g., ligand-gated, voltage-gated).
• Carrier Proteins: Uniport moves one molecule, symport moves two molecules in same direction, and antiport moves two molecules in opposite directions.
• ATP-Powered Pumps: These require cellular energy to move substances against their concentration gradient.

Receptor Proteins

• Membrane proteins or glycoproteins with receptor sites on their outer surface.
• Receptors bind to chemical signals, initiating intracellular responses.
• Types of receptor proteins include those linked to channel proteins and those linked to G-protein complexes.

G-Protein Complex-Receptor Interaction

• G-protein complexes mediate cellular responses activated by specific receptor binding.
• G-proteins are composed of alpha, beta, and gamma subunits.
• Binding of chemical signals causes changes in the G-protein subunits, leading to downstream effects.

Membrane Transports

• Plasma membranes have mechanisms to selectively move materials in and out of cells.

Cell Membrane Transport

• Membranes are selectively permeable. Types of cell transport include passive transport (no energy needed) and active transport (energy needed). Vesicular transport is a subtype of active transport.

Summary of Cell Movement

• Various transport mechanisms like diffusion, osmosis, facilitated diffusion, active transport, endocytosis, and exocytosis for movement across membranes are characterized. Energy requirements are listed for each.

Passive Transport

• Simple diffusion occurs when solute moves from high to low concentration.
• Osmosis is the diffusion of water across a selectively permeable membrane.
• Facilitated diffusion uses membrane proteins to move substances down a concentration gradient.

Active Transport

• Types include primary active transport, using ATP directly, and secondary active transport, using an electrochemical gradient created by a primary pump.

Vesicular Transport

• Endocytosis brings materials into the cell, while exocytosis releases materials from the cell.

Endocytosis

• The process of taking materials into the cell via vesicle formation. Different types of endocytosis, such as phagocytosis (taking in solid particles) and pinocytosis (taking in fluid), exist. Receptor-mediated endocytosis involves specific receptors for capturing certain molecules.

Exocytosis and Transcytosis

• Exocytosis—transporting materials out of the cell. Transcytosis – transporting materials through the cell (endocytosis followed by exocytosis).

Cell Division and Apoptosis

• Cell division produces daughter cells.
• Mitosis is for somatic cells; meiosis is for reproductive cells.
• Mitosis (prophase, metaphase, anaphase, telophase) and cytokinesis are the major stages of cell division.
• Interphase is the phase between cell divisions.
• DNA replication happens in the S phase of interphase.

Apoptosis

• Programmed cell death, regulated by specific genes (p53, Bcl-2, BAX).
• Apoptosis occurs in developing fetuses, in adulthood, and in cells affected by injury, infection, or malignancy.
• Apoptosis involves a series of cellular changes culminating in cell death.

Cellular Basis of Aging and Cancer

• Theories of aging include cellular clock, death genes, DNA damage, free radicals, and mitochondrial damage.
• Cancer is uncontrolled cell proliferation. Malignant tumors are cancerous and spread, while benign tumors are non-cancerous and do not spread.

Tissue Response to Injury

• Inflammation is the initial response to injury, involving factors such as histamine and prostaglandins that trigger vasodilation, permeability changes, and migration of white blood cells.
• Tissue repair involves replacing damaged cells with viable cells. Regeneration replaces the damaged cells with the same cell type. Replacement involves replacement by a different cell type. Stages of repair include bleeding, inflammation, proliferation, and remodeling.
• Cells have different regeneration capacities (labile, stable, permanent).

Skin Repair Process

• Stages involved in skin repair include formation of clot, inflammatory response, and granulation tissue formation.