IB Biology HL Y1 Quarter 4

Blue highlight = example / Green highlight = important info i think probably

Standards - B2.1, D2.3,

B2.1 Membranes and Membrane Transport

Phospholipids - make up cell membranes as a bilayer, barrier to large as well as hydrophilic molecules

Integral proteins - integrate/go into membrane (sometimes all the way through)

Peripheral proteins - attached to one surface or the other

Glycoproteins and glycolipids - used for cell adhesion + cell to cell recognition

Fluid Mosaic Model - model for the phospholipid bilayer

Fatty acids of lipid bilayer - has varying degrees of saturated vs unsaturated hydrocarbon (fatty acid) chains

  • Animals in colder areas - more unsaturated fatty acids - do not freeze as easily and remain more flexible

  • Saturated fatty acids - stronger membrane but can stiffen at low temperatures

Cholesterol - attached to head of one and tail of adjacent phospholipid, only in animals

  • Modulator of fluidity - lowers at high temperatures, prevents stiffening at low temperatures

  • Lowers permeability

Cell Adhesion Molecules - specialized protein membranes that allow attachment of cells to other cells, either directly attached or indirectly anchored to extracellular matrix, important in many cellular processes (like growth), different molecules mean different cell-cell junctions

Simple Diffusion - small, nonpolar molecules (nonspecific) can move between phospholipids through the membrane, passive, high to low concentration in the gradient, O2 and CO2

Facilitated Diffusion - uses protein channels to facilitate movement of small (typically), polar molecules (specific), passive, high to low concentration in the gradient, Na+ and K+

  • Types of protein channels: leakage, voltage, ligand-gated

  • Osmosis - specialized type of facilitated diffusion (passive) for water, moves through protein channels known as aquaporins, low to high solute

Active Transport - uses protein pumps and ATP (energy = not passive!) to move molecules (specific), low to high concentration in the gradient, Na+ & K+ & glucose

Endocytosis and Exocytosis

  • Allows large molecules/amounts of material to move across plasma membrane

  • Endocytosis is for entering the cell by pinching and exocytosis is for exiting the cell by fusing and releasing - possible due to the fluidity of the membrane

  • Vesicles either form in endocytosis or fuse with the membrane in exocytosis

  • They are essentially the inverse of each other

D2.3 Water Potential

hi