1. Structure and function of cell components
Carbohydrates
Lipids
Proteins
Nucleic Acids
Membranes
Cytoskeleton

2. Cell membranes
Many organelles contain or are enclosed by membranes, including
Plasma membrane
Mitochondria
Chloroplasts
Nuclear envelope
Endoplasmic reticulum
Golgi apparatus
Lysosomes
Microbodies (aka perioxisomes)
Remind selves of what all of these cell parts do. ER = phospholipid synthesis and protein synthesis. Golgi = modify, store and transport proteins and other secretory substances. Lysosomes = digest foreign invaders and unwanted organelles. Microbodies = contain enzymes that need to be kept separate from the rest of the cytosol. The functions of each of these also lead to some of the roles of the membranes in cells

3. Role of Cell Membranes
Based on the functions of the above organelles / membranes write down some of the roles of the membranes in the cells
(Leave some space as we will be adding to this list)

4. Structure of Cell membranes
Fluid Mosaic Model
Study the diagram – What features do the students already know about. Which are new? What isn’t shown in this diagram? (how saturated the fatty acids in the chains are and the movement of the lipids). Note the phospholipids can move around the circumference of an average cell in a few seconds.

5. Electron micrograph of cell membrane

6. Structure of Cell membranes
Lipids
Remember lipids have hydrophilic head and hydrophobic tails
To avoid the hydrophobic tails coming in contact with water a continuous bilayer sphere is formed.
Therefore hydrophobic interactions hold membranes together

7. Structure of Cell Membranes
Proteins
Integral proteins (intrinsic)
Proteins that are embedded in the membrane
They are held in place by hydrophobic interactions (integral proteins have hydrophobic groups on their outer surface)
Peripheral proteins (extrinsic)
Proteins attached to the surface of the membrane (often forming non-covalent bonds with integral proteins)

8. Proteins cont…

9. Function of Membrane Proteins
Attachment
Cytoskeleton
Extracellular matrix
Intercellular Junctions
Plasmodesmata
Tight Junctions
Gap Junctions
Desmosomes
Plasmodesmata – between plant cells. Tight junctions = 2 membranes fused together to produce a water tight seal to prevent fluid leaking into or out of extracellular space. Gap junctions – areas where cells have a low blood supply and therefore they rely on links (via channel proteins) to get nutrients they require. Desmosomes ‘tie’ cells together to keep them in place.

10. Function of Membrane Proteins
Transport
Carrier Proteins
Channel Proteins
Receptors
Enzymes
Cell to Cell recognition
Receptors – binding of regulatory protein e.g. a hormone, which can stimulate or inhibit molecular events in the cell. Cell to cell recognition – glycoproteins provide markers for an organism to recognise self and organise tissues. Proteins on non-self cells act as antigens and stimulate the production of antibodies.

11. Learning Activities
Use all resources to find out more about the functions of membrane proteins.
Based on the functions of proteins, add to your list on the role of membranes in cells
Read DART pgs 54 – 56
Scholar 5.1 (of interest, but you aren’t required to know it, may be the history of understanding the cell membrane structure)
The Structure of Membranes worksheet
The Role of Membranes worksheet
Advanced Higher Questions