Transport Across Membranes Flashcards
explain the fluid-mosaic model of the cell surface membrane
- the cell membrane consists of proteins, glycoproteins, phospholipids, carbohydrates and cholesterol
- the phospholipid molecules form a double bilayer and the molecules that it consists of are constantly moving
- the protein molecules are unevenly distributed throughout the membrane, forming a mosaic
explain the structure of channel proteins and its function
- they have a specific tertiary structure that spans the membrane and makes hydrophilic tunnels across it
- these channels are selective and will accept only one type of molecule
explain what carrier proteins structure is and their function
- they have a specific tertiary structure and allow the transport of ions and polar molecules by facilitated diffusion and active transport
- carrier proteins can change their shape to move a target molecule from one side of the membrane to the other
explain the receptors function in the cell surface membrane
- there is specific receptors for hormones with a complementary shape
- hormones attach to binding sites on the receptors
explain the structure and function of glycolipids
- they are composed of carbohydrates attached to a phospholipid
- they are important in cell recognition
explain the structure and function of glycoproteins
- they are composed of carbohydrates and protein
- they are important in cell recognition and sometimes act as antigens
explain the role of cholesterol on the cell surface membrane
- cholesterol decreases permeablity and increases the stability of the membrane by restricting the movement of other molecules
what is the equation to calculate diffusion rate
surface area x concentration gradient / diffusion distance
explain simple diffusion
- passive process
- diffusion is the net movement of molecules from a higher concenration to a lower concentration until evenly distributed
give 4 factors that affect the rate of diffusion
- temperature
- surface area
- concentration gradient
- diffusion distance
explain how temperature affects diffusion
- increases kinetic energy
- faster movement of molecules
explain how surface area affects diffusion
- more cell surface membrane for molecules to pass through
- therefore faster diffusion
explain how concentraion gradient affects diffusion
- as concentration gradient increases the rate of diffusion becomes faster
explain how diffusion distance affects diffusion
- the thinner the distance, the faster the rate of diffusion
explain the process of facilitated diffusion
- polar molecules cannot pass between the hydrophobic tails of the phospholipid bilayer
- therefore, to enter or exit the cell the molcules have to move through the membrane by channel proteins or carrier proteins
- these proteins have a specific tertiary structure and only transport molecules that have complementary shapes to their binding sites
- passive process
explain what omsosis is
- the net movement of water molecules from higher water potential to a solution with lower water potential through a partially permable membrane
- as water is a polar molecule, it requires a channel protein called an aquaporin to move down is water potential gradient
what is the highest value of water potential
pure water
* 0
adding a solute makes the solution ________
negative
True or False
if water is seperated by a partially permeable membrane, it will diffuse from the region of higher water potential to the region of lower water potential
True
what way will the water move?
-1.23kpa ——- -3.45kpa
to the right side (-3.45kpa)
give the definition for hypotonic
the solution inside of the cell has a lower water potential than the solution outside of the cell
- water moves into the cell
give the definition for hypertonic
the external solution has a lower water potential than the solution inside the cell
* the water moves out of the cell
give the definition for isotonic
the external solution and internal solution has the same water potential
* no net movement
what is active transport used for
used to transport molecules accross the membrane against their concentration gradient. From low concentrtion to high concentration
what protein does active transport use
carrier proteins
explain how carrier proteins work
- the molecule for transport binds to the binding site of the specific carrier protein
- the hydrolysis of atp provides a small amount of energy
- this causes the protein to change shape which “pushes” the molecule through the membrane
co-transport are a type of ______ proteins
carrier
whats the difference between a normal carrier protein and a co-transporter protein
- co-transporter proteins bind two molecules at a time
explain the equation
C1 x V1 = C2 x V2
- C1 = concentration of the stock solution (the original solution)
- V1 = volume of the stock solution
- C2 = concentration of the desired solution
- V2 = volume of the desired solution
