PHBioChem (Lecture) | Module 2.6: CELL MEMBRANES AND TRANSPORT

Lipid Bilayer

two-layer-thick structure of phospholipids and glycolipids. Nonpolar tails of the lipids are in the middle of the structure and the polar heads are on the outside surfaces of the structure.

phospholipids and glycolipids

Lipid Bilayer is a two-layer-thick structure of?

exterior polar “heads,” interior polar “heads” and central nonpolar “tails”

Three distinct parts to the bilayer

Integral membrane protein and Peripheral membrane protein

TYPES OF MEMBRANE PROTEIN

Integral membrane protein

TYPES OF MEMBRANE PROTEIN: is a membrane protein that penetrates the cell membrane.

Membrane Proteins

Some ______________ penetrate only partially through the lipid bilayer, whereas others go completely from one side to the other side of the lipid bilayer

Peripheral membrane protein

TYPES OF MEMBRANE PROTEIN: is a nonpenetrating membrane protein located on the surface of the cell membrane

Transport, Catalysis and Receptor Property

Three important functions of Cell Membrane

Transport

movement of substances across the semi-permeable membrane will be determined by its lipophilicity.

lipophilicity

Transport is the movement of substances across the semi-permeable membrane will be determined by its?

Catalysis

enzymatic reactions take place along the cell membrane (due to membrane-bound enzymes)

Receptor Property

proteins bound to the membrane trigger a biological response upon binding to a substrate.

substrate

Receptor property is proteins bound to the membrane trigger a biological response upon binding to a?

Passive Transport

Concentration gradient: movement with the gradient; from high to low concentration

Cellular energy expenditure: none required

Protein help: none required

Facilitated Transport

Concentration gradient: movement with the gradient; from high to low concentration

Cellular energy expenditure: none required

Protein help: proteins serve as “gates”

Active Transport

Concentration gradient: movement against the gradient; from low to high concentration

Cellular energy expenditure: energy input required

Protein help: proteins serve as “pumps”

Active Transport

The substance moves AGAINST the concentration gradient (from The substance moves ALONG the an area of low concentration to an area of high concentration), hence, will utilize energy (ATP).

Na+-K+ ATPase pump

Example/s of Active Transport

Passive Transport and Facilitated Transport

The substance moves ALONG the concentration gradient (from an area of high concentration to an area of low concentration), hence, will not need energy.

Simple diffusion, Ligand-gated channel (Acetylcholine receptor)

Example/s of Passive Transport and Facilitated Transport