Week 3- Biology of Cells 2: Membranes, Cytoskeleton & Cell Adhesion

Three Main Types Of Cytoskeletal Fibres Forming Cytoskeleton:

Microfilaments (actin filaments), Intermediate Filaments, Micro-tubules.

Main Types Of Cell Junctions And Their Functions:

Tight Junction, Adherens Junction, Desmosome, Gap Junction, and Hemidesmosome.

Tight Junction:

Seals neighbouring cells together in an epithelial sheet to prevent leakage of molecules

Adherens Junction:

Joins an actin bundle in one cell to a similar bundle in a neighbouring cell.

Desmosome:

Joins the intermediate filaments in one cell to those in a neighbour

Gap Junction:

Allows the passage of small water soluble ions and molecules

Hemidesmosome:

Anchors intermediate filaments in a cell to the basement membrane.

Cell Specialisations:

Microvilli, Cillia, Cytoskeleton

Microvilli:

Finger-like membrane protrusions filled with actin filaments and found on cell surfaces. It increases the surface area of the membrane, maximising absorption for enzymes, carrier proteins and glucose transports.

Cilia:

Hair-like substance 2-10 micrometers in length that mucus sits on top of. Creates current along cell surface, pushing mucus trapped with debris to mouth from lungs.

Cytoskeleton and Function:

Made up of the three filament fibres. Supports cell structures, acts as a vehicle for transport processes, also allowing for shape change and movement.

Passive Transport Types:

Diffusion, Osmosis, Facilitated Transport

Diffusion:

The process where particles of one substance spread out throughout particles of another substance

Osmosis:

Movement of a solvent across a semipermeable membrane from a region of high water concentration to a region of low water concentration.

Facilitated Transport:

Transport of molecules across cell membrane without requiring cellular energy.

Active Transport Types:

Primary and Secondary Active Transport

Primary Active Transport:

Directly uses energy, often from ATP, to move molecules across a membrane against their concentration gradient.

Secondary Active Transport:

Uses the energy stored in an electrochemical gradient to move molecules across a cell membrane against their concentration gradient.

Pinocytosis:

Cell drinker that takes only liquids in. No merger with lysosome.

Phagocytosis:

Large particle taken into cell. Phagosome fuses with lysosome, making a phagolysosome. Microbe is killed, contents are digested, and nutrients are reused or exported.