4. Cell Membrane

Extracellular Fluid: Fluid outside the cell, plays a role in cellular transport.
Carbohydrate: Present on the cell membrane, often linked to proteins and lipids.
Proteins: Integral (transmembrane), peripheral, and surface proteins, perform various functions.
Phospholipid Bilayer: Composed of hydrophilic heads and hydrophobic tails, forms the fundamental structure of the membrane.
Cholesterol: Stabilizes the membrane structure and fluidity.
Glycoproteins: Proteins with carbohydrate groups attached, important for cell recognition.
Glycolipids: Lipids with carbohydrate groups attached, involved in cell signaling and recognition.
Cytoskeleton: Provides structural support to the cell membrane through filaments.

Definition: A genetic form of hemolytic anemia.
Symptoms: Fatigue, dizziness, hair loss, jaundice (yellowing of eyes).
Mechanism: Dysfunctional proteins (spectrin, ankyrin) lead to loss of biconcave shape of red blood cells, resulting in spherical cells.

Cell Cortex: A network of proteins (actin, myosin, spectrin, ankyrin) that supports the plasma membrane of RBCs.
Glycocalyx: Sugar coating formed by carbohydrates attached to membrane proteins and lipids, vital for protection and recognition.

General Composition: All membranes consist of lipids (amphipathic) and proteins arranged in a lipid bilayer.
Types of Lipids: Phospholipids (main component), cholesterol, glycolipids.

Structure: Hydrophilic head (choline + phosphate) and hydrophobic tails (two fatty acids).
Commonality: Most abundant phospholipid in biological membranes, can have saturated or unsaturated tails.

Orientation: Hydrophilic heads face outward towards water, while hydrophobic tails shield from water, forming a bilayer.
Spontaneous Sealing: Bilayers naturally close to form stable compartments, minimizing exposure of tails to water.

Dynamic Nature: Phospholipids can move laterally, rotate, and occasionally flip between layers (rare).
Factors Affecting Fluidity: Temperature, lipid composition (unsaturation vs saturation of tails), cholesterol presence, and tail length influence membrane flexibility.

Synthesis: Phospholipids are synthesized in the smooth ER and randomly distributed to the non-cytosolic face.
Maturation in Golgi: Membrane asymmetry established during processing in the Golgi apparatus.

Types: Integral (cross the bilayer) vs peripheral (associated with surface), with various functions including enzymes, receptors, and transporters.
Mobility: Proteins can move laterally but can be restricted by diffusion barriers or interactions with other cellular components.

Coating: Sugar structures of glycoproteins and proteoglycans facing exterior, critical for cell recognition and adhesion.
Role in Adhesion: Facilitates cell-cell adherence and interaction, exemplified by sponge cell tissues.

Key Roles: Cell signaling, transport, cellular growth/motility, intercellular adhesion, and cell-cell recognition.

Understand the structure and function of the cell cortex, lipid bilayer formation, membrane protein dynamics, and glycocalyx roles.

Amino Acid: Basic building blocks of proteins.
Hydrophobic/Hydrophilic: Describes the affinity of molecules towards water.
Glycocalyx: Carbohydrate layer on cell surfaces for recognition and adhesion.
Transmembrane Proteins: Proteins that span across the membrane, involved in various functions.