Cell Membrane Functions Quiz

Week 3 Concepts

• Principles of Cell Theory (C150):
  • The smallest structure capable of carrying out life processes is a cell.
  • Every organism consists of one or more cells.
  • Cells arise only from pre-existing cells.
• Organization of cells:
  • Prokaryotic cells: Lack an organized nucleus.
  • Eukaryotic cells: Contain an organized and well-defined nucleus.
• Four structures common to most cells:
  • Plasma (cell) membrane: Separates internal and external environments.
  • DNA: Genetic material that controls an organism's composition.
  • Cytoplasm: Consists of cytosol (liquid portion) and organelles.
  • Organelles: Specialized structures within the cell, including ribosomes (protein synthesis site).
• Eukaryotic Human Cells:
  • Cytoskeleton: Intracellular support, used in cell movement and organelle transport.
  • Cells: Composed of plasma membranes, cytoplasm, and cytosol.
• Cytosol: The clear gel within the cell referred to as intracellular fluid; cytoplasm includes the cytosol and cytoskeleton.
• Gamete and Somatic Cells:
  • Gametes: Sex cells (sperm and ovum) that replicate via meiosis.
  • Somatic cells: All other cells in the body that replicate via mitosis.

Introduction to Cell membranes and their function (C151)

• Functions of the cell membrane:
  • Acts as a barrier protecting the cell's inner content from the extracellular environment.
  • Anchors the cytoskeleton.
  • Shapes the cell.
  • Allows for cell communication through chemical passage.
• Movement of essential molecules into and out of cells.
• Made from a phospholipid bilayer:
  • Hydrophilic (water-loving) heads
  • Hydrophobic (water-hating) tails
• Molecules embedded in phospholipid bilayer:
  • Transmembrane proteins: Span the membrane width.
  • Peripheral proteins: Found on one surface.
  • Cholesterol: Creates fluid mosaic structure and flexibility.
  • Sugars: Glycolipids and glycoproteins (cell markers).

Plasma Membrane Proteins

• Integral proteins: Span the entire width of the membrane's inner and outer surfaces.
  • Examples: Ion channels, proton pumps.
• Channel proteins: Allow ions to pass through.
• Carrier proteins: Transport specific substances across the membrane.
• Receptor proteins: Recognize and bind to specific molecules (ligands).
• Cell identity markers: Allow cells to be identified by the immune system.
• Na+/K+ ATPase pump: Maintains electrochemical gradient.
• Gap junctions: Connections between cells.
  • Also include cell adhesion molecules, and enzymes catalyzing reactions.
• Peripheral proteins: Found on the inner or outer membrane surface.
  • Examples: Cadherins, Cytoskeletal proteins, and Cytocrome C
• Spectrin: Important in maintaining red blood cell shape.

Other structural components of the cell membrane

• Sugars: Provide protection, display signals, and attach cells.
• Cholesterol: Decreases membrane fluidity, offering structural support and insulation.
• Phospholipid bilayer: Forms a double layer with hydrophilic heads facing the exterior and hydrophobic tails facing the interior.

Passive Transport

• Mechanisms of movement of materials across the cell membrane without using ATP, from higher to lower concentration.
  • Simple diffusion: Movement of molecules without assistance.
  • Facilitated diffusion: Uses a transport protein for assistance.
  • Osmosis: Water movement across a semipermeable membrane from a lower solute concentration to a higher solute concentration.

Active Transport

• Movement of molecules across the cell membrane against their concentration gradient.
• Requires energy input (e.g., ATP).
• Bulk Transport: Large molecule movement using vesicles. Includes endocytosis (bringing material into the cell) and exocytosis (releasing material from the cell).

Membrane Potential

• Cells maintain a difference in electrical charge across the cell membrane.
• Ions and protein pumps maintain this voltage known as resting membrane potential (RMP). A negative voltage means the inside of the cell is more negatively charged then the outside.

Organelles (C152)

• Specialized structures that perform specific cell functions.
  • Nucleus: Genetic control center directs protein synthesis.
  • Rough ER: Involved in protein synthesis.
  • Smooth ER: Involved in lipid synthesis.
  • Ribosomes: Site of protein synthesis.
  • Golgi complex: Involved in protein modification and packaging.
  • Lysosomes: Contain enzymes to break down waste materials.
  • Peroxisomes: Oxidize fatty acids and protect cells.
  • Proteasomes: Degrade unnecessary proteins.
  • Mitochondria: Generate energy (ATP) through cellular respiration.
  • Centrioles Involved in cell division.
  • Centrosome Organizes the mitotic spindle during division.
  • Basal body Point of growth for cilium or flagellum

Cell Functions (C153)

• Central Dogma:
  • DNA replication to RNA as a blueprint to create proteins
  • Transcription: DNA → mRNA
  • Translation: mRNA → Protein
• Protein synthesis:
  • Organelles responsible for making proteins
  • Genetic code using four nucleotides bases in DNA, form sequences in body
• Cellular respiration:
  • Process that utilizes oxygen and nutrients to produce energy (ATP)

Chemiosmosis

• Using the electrochemical H+ gradient to create ATP.

Cellular respiration Steps

• Glycolysis
• Krebs cycle
• Electron transport

Cell Cycle

• Series of events that lead to cell division. -Includes Interphase and the M-phase.
  • Interphase: Divided into three phases: G1, S, and G2. Preparing cell for division. -M-phase: Mitosis and Cytokinesis, resulting in two identical daughter cells.

Mitosis and cytokinesis

• Process of cell division for growth, repair, and asexual reproduction.
• Steps: Prophase, Metaphase, Anaphase, Telophase & Cytokinesis

Tissue growth, modification and repair (C130)

• Atrophy: Wasting or degeneration of cells/tissue
  • Example; Muscle atrophy with limited movement
• Necrosis: Death of cells due to disease, injury or insufficient oxygen supply.
• Apoptosis: Programmed cell death, part of normal development and growth.
• Regeneration: Restoration of tissues, where damaged tissue is replaced.
• Fibrosis: Tissue scarring after wound healing, often leading to loss of function.
• Hypertrophy: Increase in cell size, leading to tissue enlargement.

Hyperplasia-

• Increase in cell number, increase in tissue size

Metaplasia-

• Permanent or temporary permanent change in the nature of a tissue.

Dysplasia

• Presence of abnormal cells, often as a sign of early-stage cancer.

Steps of Tissue Repair After Injury-

• Inflammation- Early stage of repairing damaged tissue. -Proliferation- Renewal of tissue.
• Maturation- Long-term repair.

Membranes:

• Cutaneous membranes: Composed of epithelial tissue attached to connective tissue.
• Mucous membranes: Epithelial tissue lining cavities and organs that have openings to the outside.
• Serous membranes: Consist of epithelial tissue that lines cavities and organs.
• Synovial membranes: Line joints and secretes synovial fluid.