Cell Membranes Flashcards
Phospholipids
Hydrophilic head faces out as it interacts with water not fat (made of phosphate)
Hydrophobic tail faces away from water mixes with fat (made of fatty acids)
Fluid mosaic model
Fluid because each individual phospholipid molecule and the proteins are in constant motion
Mosaic because the embedded proteins vary in shape size and pattern like mosaic tiles
Role of cholesterol
Adds strength to proteins
Prevents movement if urgent molecules in membrane
Extrinsic proteins
Extrinsic proteins do not pass entirely through membrane (on surface)
Some have glycolipids and glycoproteins which interact with molecules that arrive at cell surface
Intrinsic protein
Are either enzymes or act to transport water soluble substances through bilayer (channel proteins)
Simple diffusion
Transport of substances directly through lipid bilayer
Transports hydrophobic substances and small hydrophilic
These substances are said to be lipid soluble
Results of the random motion of particles
Facilitated diffusion
Diffusion involving the presence of a protein allowing passive movement Useful for larger molecules and ions Two types:channel proteins (water filled channel allowing water soluble ions and molecules to pass through) And carrier proteins (when a molecule binds to a protein, the protein changes shape and molecule is released in other side.its module specific.
Osmosis
Passage of water:
From a dilute to a concentrated solution
High concentration of water to low concentration of water
High water potential to low water potential
Osmosis trues to balance the concentration
Hydration shells:water molecules surround solutes, any frees water molecules can move back and forth but the solutes are too big so keep the water molecules on their side.
Water potential
Way of quantifying osmosis
Represented by Greek letter psi
Measured in units of pressure (pa or kpa)
Water always falls from high to low water potential
Pure water has 0 water potential
As solute is added it turns to negatives
Co transport
Carrier proteins transporting two different particles at once
Both must be present
Often both an active and passive process due to one being with and one being against a concentration gradient.
Symport
Both moved in the same direction
Antiport
Moving in opposite directions
Epithelial cells and the blood step one and two - absorbing glucose
(Sodium)
Active transport of na+ ions out of epithelial cell into blood and k+ ions from blood into epithelial cells via carrier protein (active transport)
Sodium conc is now low so
Na+ ions diffuse through carrier protein from lumen to epithelial cell and glucose is brought in via co transport against concentration gradient this step is facilitated diffusion (symport)
(Yes it’s going against its concentration gradient but no atp is used)
Step 2 absorption into blood
Glucose diffused from epithelial cells into capillary via facilitated diffusion due to concentration gradient through channel protein
Why is distilled water used for potato practical
The ions could affect osmosis
