Lecture 1 and 2
- TOPIC #1 MEMBRANE STRCTURES
- Saccharomyces cerevisiae: budding yeast, single-celled eukaryote
o Important model system for study because similar things happen in human cells
o It has a membrane enclosed nucleus
o Has plasma membrane that regulates the influx of materials to the cell
o Has cell wall (not found in animal cells) but it helps this organism protect itself from harsh environments
- Multicellular organisms are composed of many different cell types
o Carry out very distinct functions
- Typical Animal Cell has:
o Extracellular matrix: helps give tissue support, found in many animal cells
o Lysosomes: helps to digest material, animal specific
- Typical plant cell:
o Has nucleus, ER, golgi apparatus, peroxisome, mitochondria (NRG is produced by cell that fuels
processes), plasma membrane
o Vacuole takes up more than 1/3 of cell volume
o Vacuole:
Fluid filled area that helps provide turgor pressure against cell wall that keeps the plant rigid
Digestion of components also occurs here
Storage of small molecule and proteins
Some single-celled organisms also have a vacuole
o Plant cell wall gives it a rigid structure
- Cytoplasm: content of the cell outside the cell nucleus. It includes that organelles that are found w/in cell but
outside cell nucleus
- Cytosol: aqueous part of cytoplasm. Doesn’t include other membrane bound organelles. Odes include the
solubilised protein structure
o Eg. Ribosomes (carry out protein synthesis), cytoskeleton etc
- Lumen: inside of the specific organelle
- MEMBRANE STRUCTURE:
- Many cellular functions occur at membranes:
1. Compartmentalization: allow diff processes to occur in diff parts of cell.
a. Plasma membrane: separates entire cell from environment
2. Scaffold for biochemical activities: diff proteins found w/in diff membranes
a. Eg. Transport in mitochondria generates ATP
3. Selectively permeable barrier to outside. Movement is regulated by specific proteins
4. Transporting solutes
5. Responding to external signals: caused by specialized proteins on cell membrane called receptors. They bind
to diff proteins and initiate cascade of events that allow cellular change
6. Interactions b/w cells: make channel that allow solutes to be transferred
- CLICKER QUESTION: Which of the following statements best describes the structure of membrane:
o The lipid bilayer is composed of three different types of lipids. Incorrect: 3 main types of lipids, but there
are 100’s of diff types of lipids in membrane. 500-1000 lipids make cellular membranes.
o It is a fluid bilayer composed of hundreds of diff types of lipids and proteins
o Bilayer of amphiphilic lipids, glycoscolated on cytoplasmic leaflet. Incorrect: they are glycosolation
happens outside of cell. Protective coating for cell. Has important signaling for cell.
o All of the lipids in bilayer have 2 Hydrophobic hydrocarbon tails. incorrect: b/c chlorestrol does not have
2 HC tails.
- Cell Membranes:
o Divides cell into compartments
o Control movement of molecules
o Lipid bilayer: basic unit of membrane
Provides membrane with a lot of its properties
Fluid structure. Lipids are not immobile, they are able to move w/in membrane
o Membrane proteins: suspended w/in bilayer
Receptors, channel proteins
Able to move within bilayer
o The fluid mosaic model of membrane: fluid b/c everything is able to move. Mosaic b/c there are not
identical or repeating structures in bilayer
o Lipid bilayer is amphiphilic