Cell Biology Part IV: Cellular Structure: Membrane and Framework

Flashcards of cell biology lecture notes for vocabulary review.

Cell Membrane

The flexible boundary that separates a cell and its environment, or different compartments (organelles) of a cell.

Function of Plasma Membrane: Receiving Information

Receiving chemical signals by receptor proteins.

Function of Plasma Membrane: Import and Export Molecules

Nutrient input and waste release through passive diffusion or specialized channels.

Function of Plasma Membrane: Movement

Fluidity of plasma membrane allows cytoplasm to flow toward a certain direction and result in movement.

Organelles with one layer of phospholipid bilayer

Vesicles, Lysosomes, Peroxisomes

Organelles with two layers of phospholipid bilayer

Mitochondria, Nuclei, Chloroplasts (in plants)

Basic Structure of Plasma Membrane

Phospholipid Bilayer and Transmembrane Proteins

Functions of Transmembrane Proteins

Cross membrane transportation, communication, connection.

Hydrophilic Head of a Phospholipid

Consists of a polar chemical group (including phosphate). Soluble in water.

Hydrophobic Tail of a Phospholipid

Consists of a nonpolar long carbon chain, similar to lipid molecules. Not soluble in water.

Amphipathic

The characteristic of having both hydrophilic and hydrophobic components.

Detergents

Dissolve oils and lipids by interacting with oil's long carbon chains and water.

Phospholipid Bilayer Formation

Phospholipid molecules aggregate together and form a bilayer of a vesicle.

Fluidity of Phospholipid Membrane

Allows molecules to constantly move; allows higher permeability; allows membrane to fuse with membrane.

Flippases

Actively transfer certain phospholipids from the cytosolic side to the non-cytosolic side.

Double Bonds in Phospholipids

Double bond on one of the tails makes an un-rotatable angle, resulting in a kink on the tail.

Function of Steroids in Plasma Membrane

Steroids (cholesterol) fill the space between phospholipid tails, reducing the fluidity of the phospholipid.

Glycolipids

Located mainly on the non-cytosolic side of the plasma membrane to form a layer of carbohydrate lubrication.

Functions of Membrane Proteins

Transporters, Anchors, Receptors, Enzymes

Transmembrane Proteins

Use α-helix to insert through the membrane.

Membrane Associated Proteins

Located entirely on one side of the membrane, anchoring part of its peptide in one layer of the membrane.

Lipid Linked Proteins

Protein linked with lipid groups, replacing the phosphate on the phospholipid; this becomes an anchor inserted into the membrane.

Protein Attached Proteins

Proteins that link with another protein that can insert into the membrane.

Hydrophilic Pore

Control the passage by the property of target chemicals, allowing hydrophilic to pass, but not hydrophobic.

β Barrel

Composed of 16 β sheets that curved around on each other and become a barrel.

Function of β Barrel Channels

Allow water or nutrients to come in, but still be able to prevent larger molecules (such as toxin) to enter.

Cell Cortex

Membrane surface protein meshwork that determines the shape of the cells.

Spectrin

Long thin flexible protein that connects with other protein to be meshwork cell cortex.

Glycoprotein

Proteins covalently linked with oligosaccharides (short sugar chain).

Proteinglycan

Proteins covalently linked with polysaccharides (long sugar chain).

Glycolipid

Phospholipids covalently linked with oligosaccharides (short sugar chain).

Location of Glycoprotein, Proteinglycan, and Glycolipid

Located on the noncytosolic side of membrane and form a Carbohydrate surface – Carbohydrate layer to protect the membrane by lubricating the cell membrane.