Which of these substances can pass directly through cell surface membranes without using a carrier protein or channel protein? $$\(1 \mathrm{~K}^{+}\)$$and $$\(\mathrm{Cl}^{-}\)$$ $$\(2 \quad \mathrm{CO}_{2}\)$$ $$\(3 \quad \mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{6}\)$$

4.1.1 describe the fluid mosaic model of membrane structure with reference to the hydrophobic and hydrophilic interactions that account for the formation of the phospholipid bilayer and the arrangement of proteins

4.1.2 describe the arrangement of cholesterol, glycolipids and glycoproteins in cell surface membranes

4.1.3 describe the roles of phospholipids, cholesterol, glycolipids, proteins and glycoproteins in cell surface membranes, with reference to stability, fluidity, permeability, transport (carrier proteins and channel proteins), cell signalling (cell surface receptors) and cell recognition (cell surface antigens – see 11.1.2)

4.1.4.1 secretion of specific chemicals (ligands) from cells

4.1.4.2 transport of ligands to target cells

4.1.4.3 binding of ligands to cell surface receptors on target cells

4.2.1 describe and explain the processes of simple diffusion, facilitated diffusion, osmosis, active transport, endocytosis and exocytosis

4.2.2 investigate simple diffusion and osmosis using plant tissue and non-living materials, including dialysis (Visking) tubing and agar

4.2.3 illustrate the principle that surface area to volume ratios decrease with increasing size by calculating surface areas and volumes of simple 3-D shapes (as shown in the Mathematical requirements)

4.2.4 investigate the effect of changing surface area to volume ratio on diffusion using agar blocks of different sizes

4.2.5 investigate the effects of immersing plant tissues in solutions of different water potentials, using the results to estimate the water potential of the tissues

4.2.6 explain the movement of water between cells and solutions in terms of water potential and explain the different effects of the movement of water on plant cells and animal cells (knowledge of solute potential and pressure potential is not expected)