Transport across cell membranes Flashcards
What are the functions of Cholesterol in the cell membrane
maintains lipid bilayer during temperature fluctuations e.g. make membrane less fluid at high temperatures
What are the functions of Glycoproteins in the cell membrane
they acts as a recognition site which help cells attach to one another to form tissues and allow cells to be recognised as an organism’s own cell
What are the functions of Glycolipids in the cell membrane
they act as a recognition site that helps maintain the stability of the membrane and allow cells to attach to one another form tissues
What are the functions of Proteins in the cell membrane
imbedded in the cell membrane for mechanical support like hormone receptors and used as channel and carrier proteins for facilitated diffusion
What are the functions of the cell membrane
- boundary between the cell cytoplasm and the environment
- controls movement of substances in and out of the cell
- allow different conditions to be established in and out side of the cell
Why is membrane permeability different for different for molecules
- some molecules are to large to pass through the channels
- if they have the same charge as the proteins they get repelled
- if they’re polar they will have difficulty passing by the non-polar hydrophobic tails of the phospholipids
Describe the structure of a phosholipid
- hydroPHOBIC tails
- hydroPHILIC polar heads
Whats is meant by the Fluid Mosaic model of a cell membrane
built up of a mixture of phospholipids and proteins which gives membrane flexibility
What is simple diffusion
particles are always in motion due to kinetic energy, net movement of ions is from high to low concentration until distributed equally
What is facilitated diffusion
the diffusion of larger molecules through the bilayer with the help of channel and carrier proteins
What is a Carrier protein
an ion binds to the protein changing the shape of the protein using its kinetic energy, and opening it up to the otherside of the bilayer
allows for the diffusion of ions like glucose
What is a Channel protein
the channel is only open when an ion is present to maintain control of the entry and exit of ions
allow for the diffusion of water soluble ions
Define osmosis
the net movement of water molecules from a high to low water potential across a selectively permeable membrane
What would happen to a red blood cell in a Hypotonic, Hypertonic and Isotonic solutions
Hypotonic - lysis - water enters cell
Hypertonic - crenation - water leaves cell
Isotonic - stays intact
What would happen to a plant cell in a Dilute, Hypotonic, Hypertonic and Isotonic solutions
Dilute - rigidity of cell wall keeps it intact
Hypotonic - cell becomes flaccid - water enters cell
Hypertonic - cell plasmolysis - water leaves cell
Isotonic - stays intact
Define Dilute, Hypotonic, Hypertonic and Isotonic solutions
Dilute - Small increase of water potential but same solute concentration
Hypotonic - high water potential (when there’s a greater concentration of solutes on the outside of a cell than the inside so there is influx of solute onto cell)
Hypertonic - low water potential (when there’s a greater concentration of solutes on the inside of a cell than the outside so solute moves out of cell)
Isotonic - when the osmotic pressure in cell and environment is equal
What is water potential
the pressure created by water molecules
- high water potential = less negative number
- low water potential = more negative number
What is active transport
the movement of molecules against concentration gradient from low to high concentration with the use of ATP and carrier proteins`
Why do cells in the intestine have many mitochondria
to produce a lot of ATP for active transport to take place
How does the sodium potassium pump work
- sodium binds to the carrier protein on the outside
- ATP binds to the carrier protein
- ATP splits into ADP + Pi
- ADP is released opening the carrier protein to the inside of the membrane
- potassium bids to the carrier protein on the inside
- sodium moves in
- Pi is released and carrier protein opens to outside of the membrane
- potassium moves out to maintain concentration gradient andcharge
How is the structure of an epithelial cell in the ileum linked to its function
they have:
- a short diffusion distance
- constant blood flow to maintain concentration gradient
- microvilli, which further increase surface area for diffusion
What is co-transported alongside sodium in the small intestine
glucose is co-transported into the epithelial cells, then into the blood capillary alongside sodium by facilitated diffusion
Why are there many different protein carriers in the epithelial cells of the small intestine
for facilitated diffusion and active transport to take place at the same time
