Cell Membrane Components Quiz

Cell Membrane Components

• Phospholipid Structure: Composed of charged, polar hydrophilic heads and non-polar, hydrophobic fatty acid tails.
• Organization: Heads face aqueous solutions while tails face inward, forming a bilayer.
• Selective Permeability: Allows passage of small, non-polar, and fat-soluble substances.

Membrane Proteins

• Peripheral (Extrinsic) Proteins:

  • Small molecules, loosely attached to membrane surfaces.
  • Located outside the lipid bilayer.

• Integral (Intrinsic) Proteins:

  • Larger, firmly attached molecules embedded within the lipid bilayer.
  • Some extend across the entire membrane (transmembrane proteins).

Protein Synthesis

• Free Ribosomes: Synthesize proteins for internal cell use (e.g., mitochondria, nucleus).
• Attached Ribosomes (RER): Produce proteins to be secreted or sent to cell membranes and lysosomes.

Proteasomes

• Function: Barrel-shaped organelles that degrade cytoplasmic proteins tagged with ubiquitin.
• Importance: Removes excess and improperly folded proteins, and destroys viral proteins; defects can lead to diseases like Alzheimer’s.

Cytoskeleton Components

• Microfilaments (Actin Filaments):

  • Diameter: 5-7 nm, consisting of F-actin formed by G-actin polymerization.
  • Functions include cell support, muscle contraction, and shape changes (endocytosis/exocytosis).

• Microtubules:

  • Diameter: 24 nm, hollow cylinders made of α and β tubulin subunits.
  • Involved in cell shape, intracellular transport, and formation of mitotic spindles during cell division.

Centrosome and Cell Division

• Centrosome Structure: Two cylindrical structures (centrioles) that are perpendicular, involved in microtubule organization.
• Function: Form mitotic spindles for cell division and regulate microtubule growth.

Nucleus Structure and Function

• Largest Organelle: Contains DNA and is essential for cell life.
• Components: Nuclear envelope, chromatin, nucleolus.

Chromatin Types

• Euchromatin: Extended, transcriptionally active, visible in active cells (e.g., liver).
• Heterochromatin: Condensed, transcriptionally inactive, predominant in inactive cells (e.g., small lymphocytes).

Cell Cycle Phases

• Interphase: Accounts for 90% of the cell cycle, includes G1, S (synthesis), and G2 phases.
• Mitosis: Process of cell division.

Apoptosis

• Active Cell Death: Morphological changes include chromatin condensation, nuclear fragmentation, and membrane blebbing, resulting in apoptotic bodies.

Stem Cells

• Definition: Undifferentiated cells capable of self-renewal and differentiation.
• Types:
  • Embryonic stem cells (found in embryos).
  • Adult stem cells (located in tissues like bone marrow and skin).
• Static Cell Populations: Cells that no longer divide (e.g., CNS and cardiac muscle).
• Stable Cell Populations: Cells that divide slowly to maintain tissue structure (e.g., liver cells).
• Rapidly Renewing Populations: Cells that frequently divide (e.g., blood cells and skin epithelium).

Test your knowledge on the structures and functions of cell membrane components, including peripheral and integral proteins, as well as the roles of phospholipids. Understand the characteristics of hydrophilic and hydrophobic parts of cell membranes. Perfect for students in the Faculty of Medicine.