What are the functions of the cell membrane
- provides a barrier b/t the cell and the enviroment
- determines what enters/exits the cell = selective permeability (only allows some things in and out)
- transits signals from the outside of the cell to the inside
- important to the attachment of cells to one another in formation of tissues
- all cells are surrounded by an aqueous enviroment
What is the structure of the cell membrane like
- flexible double layerd phospholipid membrane (phospholipid bilayer) studded with proteins
- the arrangement of phospholipids and cholestrol provide the main structure of the membrane
What is the hydrophobic effect
tendency of polar molecules (such as water) to exclude hydrophobic molecules such as fatty acids
Liposome vs Micelle vs Bilayer Sheet
Liposome: transports nutrients
Micelle: used to carry non-polar things (FATS!)
Bilayer Sheet: is the membrane
What are phospholipids
- How are they arranged
- provides what
- consist of …
produced by…
- arranged in a bilayer creating the barrier b/t the cell and the enviroment
- provides the matrix in which proteins and other macromolecules are embedded yet free to move
- consist of a hydrophilic head and a hydrophobic tail
- PRODUCED BY THE SER
What are the bonds holding the phospholipids together and what does it allow
Vander Waals forces - allows proteins to float freely and phospholipids to change locations millions of times/second
What are the 3 factors that influence fluidity
- TEMPERATURE
- C=C
- CHOLESTEROL
how does temperature influence fluidity
- as temp rises the membrane becomes more fluid and eventually loses its ability to act as a barrier
- as temp decreases membrane solidified into a gel like state
How does C=C influence fluidity
- forms kinks in phospholipid tails decreasing their ability to pack tightly together and decreases Van der Waals forces
- allows O2, H2O, N2, CO2 to enter and exit the cell
How does cholesterol influence fluidity
- acts as a wedge between phospholipid tails
- allows animal cells to function through a wide range of temperatures
- increases the permeability of the membrane because it disrupts the alignment of the phospholipid tails
What are the functions of the membrane
- Transport
- Enzymatic Activity
- Signal Transduction
- Attachment/Recognition
In terms of communication what do GLYCOLIPIDS do
function as tissue markers
In terms of communication what do GLYCOPROTEINS do
function as self markers
- are specific to you and are important to transplants and blood types
In terms of communication what do RECEPTOR PROTEINS do and give an example
bind to a specific signal molecules which then causes a biological response inside the cell
ex: insulin binds to liver cell receptors causing them to take in glucose & store it
Can molecules pass b/w the phospholipids
yes they can if they’re small enough and/or not too polar —> larger and/or polar molecules need the help of proteins to allow passage
What are the types of transport proteins?
- Channel proteins
- Carrier proteins
- Gated channels/receptors - mediated channels
- Pump proteins
What are CHANNEL PROTEINS
- forms pores through which small, water soluble molecules/ions pass
- entry of metabolite depends on size and charge
- like a tube slide and facilitates passive transport (no energy)
What are CARRIER PROTEINS
- shuttles molecules across the membrane based on shape
- protein changes shape
- facilitate passive transport
Roughly describe what GATED CHANNELS/RECEPTOR - MEDIATED CHANNELS are/do
- a neurotrasmitter binds to the proteins, the protein opens and allows the ions to flow across the membrane
What will vs will NOT pass through the cell membrane
YES:
- water (b/c it is small)
- O2 & CO2 (gases)
- small hydrophilics
NO:
- large fats
- large polar molecules
- charged/polar (proteins, amino acids, ions)
What are PUMP PROTEINS
- pumps ions in to and out of the cell
- facilitates active transport (requires energy)
- 3 ions in and 2 ions out = creates a charge and equilibrium
What are peripheral proteins
- NOT embedded in the membrane but rather attached to integral proteins through non-covalent bonds (hydrogen, ionic)
- hold integral proteins in place
*act as enzymes and help with shape changes - form part of the cytoskeleton
Proteins act as attachment points for:
- cytoskeleton elements
- extracellular matrix
What are some proteins also able to do
can recognize antigens on pathogens and trigger an immune response
