DNA: Structure The nucleic acid DNA is a polynucleotide – it is made up of many nucleotides bonded together in a long chain DNA nucleotide DNA molecules are made up of two polynucleotide str...
Mononucleotides: Structure Both DNA and RNA are polymers that are made up of many repeating units called nucleotides Each nucleotide is formed from: A pentose sugar (a sugar with 5 carbon atoms) A ...
Osmosis All cells are surrounded by a cell surface membrane which is partially permeable Water can move in and out of cells across the cell surface membrane by a process called osmosis Osmosis is t...
Active Transport Active transport is the movement of molecules and ions through a cell membrane from a region of lower concentration to a region of higher concentration Active transport requires en...
Diffusion & Facilitated Diffusion Diffusion is a type of transport that can occur across a cell membrane Note that diffusion can also happen within a cellular compartment; the presence of a mem...
Practical: Investigating Membrane Structure & Permeability The permeability of cell membranes is affected by several factors such as Temperature pH The effect of such factors on membrane struct...
Cell Membranes Membranes are vital structures found in all cells The cell surface membrane creates an enclosed space separating the internal cell environment from the external environment, and intr...
The Mammalian Lung: Structure & Function The lungs of air-breathing animals provide an ideal exchange surface for the diffusion of gases The lungs are located in the thorax, or chest cavity Som...
Fick's Law of Diffusion Fick's Law relates the rate of diffusion to the concentration gradient, the diffusion distance and the surface area This relationship can be represented by the following equ...
