Who is Robert Hooke?
One of the first people to discover the cell and look at it under a microscope
How does a microscope work?
Light is first focused on the sample, then a combination of lenses and/or mirrors focuses an image of the illuminated sample to a detector (observer/camera)
What is the function of the plasma membrane?
- Separates the inside and outside of the cell
- Maintains structural integrity
- Regulates the passage of materials into and out of the cell
- Maintains a life-supporting internal environment
What is the purpose of the selective barrier?
- Gather nutrients from outside the cell
- Process these nutrients
- Retains the products it creates
- Manages it’s by-products with the outside cell environment (gets rid of extra waste inside the cell)
What are eukaryotic cells?
- Contain organelles
- Each organelle if enclosed within a membrane
- Animal and plant cells are eukaryotic
What is the plasma membrane largely composed of?
A lipid bilayer, which is composed of mainly phospholipids. (Hydrophilic heads on the outside and hydrophobic tails facing inwards = amphipathic)
What is spontaneous self organisation?
The process by which molecules have the ability to form a bilayer
What are detergent molecules?
Cone shaped amphipathic molecules that associate in water as spherical structures
What happens to phospholipids in water?
They associate as bilayers
What are the 3 classes that membrane lipids fall into?
- Phospholipids
- Glycolipids
- Cholesterol
What is a membrane?
A 2D fluid “substrate” where other molecules are dispersed in.
- Consist of phospholipid molecules
- With embedded or associated proteins and lipids
- Position of many of the proteins is constantly changing
What is a glycocalyx (cell coat)?
- Formed by polysaccharide side chains of proteins and lipids
- Protects the cell and may help keep other cells at a distance
- Enable cells to recognise one another and make contact
What is the function of the membrane proteins affected by?
The bilayer’s viscosity. The fluidity of the cell membranes has to be precisely regulated. The inner face has to be mostly unsaturated fatty acids, bc that makes it more fluid. The outer face has more saturated fatty acids, making it more solid or viscous
What is the purpose of cholesterol and other steroids in the membrane?
They are very hydrophobic, so they can intercalate between phospholipid molecules which:
- Prevents close packing of the phospholipids
- Decreases permeability to small water-soluble molecules
- Confers rigidity for mechanical support
To maintain membrane stability during cold seasons, which potential mechanism can these organisms use to compensate the temperature drop?
Add more fatty acids with more cis-double bonds
Why are there significant differences between the intra- and extracellular space?
Bc the distribution of phospholipids is asymmetrical
Are all major phospholipids in mammalian membranes electrically neutral?
Yes, except for phosphatidylserine which is negatively charged
What are the two main classes of membrane proteins?
- Integral
- Peripheral
Integral proteins?
- Firmly bound to the membrane
- Goes through the entire membrane (transmembrane)
- Either a a-helix or a permeable b-barrel
- Anchors, transports, ion channels, enzymes, and/or receptors
Integral proteins?
- Firmly bound to the membrane
- Goes through the entire membrane (transmembrane)
- Either a a-helix or a permeable b-barrel
- Act as: anchors, transports, ion channels, enzymes, and/or receptors
Aquaporins?
- Channel proteins
- Embedded in cell membrane and regulates flow of water through passive transport
Glycoproteins?
An oligosaccharide bonds to a protein through glycosidic linkage. This either provides protection for the cell, or the cells adhere to create mucus(waste removal)
Explain why there is spontaneous formation of phospholipids bilayers in water?
- To reduce free energy costs
- Phospholipids aggregate to shield their hydrophobic tails from the water, and expose their hydrophilic heads to water
What is the function of the plasma membrane?
Serve as a highly selective barrier
