Transport across cell membrane Flashcards
5 types of transport over cell membrane
Simple diffusion
Facilitated diffusion
Osmosis
Active transport
Co transport
Which transport processes are passive?
Simple diffusion
Facilitated diffusion
Ósmosis
What of the transport methods are non passive
Active transport
Co transport
What do passive processes mean?
does not Require energy released in the form of ATP from respiration
Simple diffusion
Net movement of particles from a region of high concentration to a region of lower concentration across the phospholipid bilayer
How does simple diffusion occur?
Simply over the phospholipid bilayer
Which has a non polar region in the centre of fatty acid tails
What molecules are transported by simple diffusion?
Non polar molecules
Small ones transported fastest eg co2 and o2
And fatty acids
What factors affect the rate of simple diffusion?
Temperature (particles have higher Ek + greater rate of diffusion)
Surface area (larger means more can happen at once)
Diffusion distance (smaller = faster)
Concentration gradient
Why cant charged/ large molecules be transported by simple diffusion?
Charged particles cannot cross the non polar fatty acid region of the phospholipid bilayer
Larger molecules transported slower over membrane
Facilitated diffusion
The movement of charged/polar substances over the phospholipid bilayer with help of SPECIFIC intrinsic membrane proteins
From an area of high concentration to an area of low concentration
Intrinsic membrane proteins for facilitated diffusion
Carrier protein
Channel protein
Carrier protein structure and how it works
The substance binds to this protein then it will change shape to release substance to other side (changed tertiary structure)
What particles transported by facilitated diffusion?
Larger water soluble/ polar molecules eg glucose
Channel proteins structure
A central pore which allows substances to move directly through
Specific shape of pore to a particular ion’s charge/shape
What molecules transported by channel proteins
Charged particles eg ions
Factors that affect rate of facilitated diffusion
Same as simple diffusion (conc gradient, temp, surface area, diffusion distance)
More membrane intrinsic proteins means more can diffuse at the same time
What is osmosis?
The passive movement of water molecules from a region of high water potential to lower water potential
Water potential
A measure of the pressure caused in membranes by collisions of water molecules
How is water potential measures?
On a scale where
0= pure water
And the further negative means less water molecules because the solution is concentrated
How come water molecules move by osmosis over the phospholipid bilayer despite being polar?
Because they are small so can diffuse through despite the non polar fatty acids region
Animal/ plant Cell in Isotonic solution effect
When the solution on either sides or the membrane has the same water potential (no movement of water molecules)
Animal Cell in a hypotonic solution
The water potential is higher outside of the cell so moves in by osmosis
Increases hydrostatic pressure in cell = swell burst without a cell wall
animal cell in a hypertonic solution
The water potential is lower outside the cell so water moves out the cell by osmosis causing the cell to shrink
Plant cell in a hypotonic solution
The water potential is higher outside the cell than inside so will move into the cell by osmosis so protoplasm (cytoplasm and membrane) pushes against cell wall, prevented from bursting (turgidity) because of cell wall
Plant cell in a hypertonic solution
The water potential is lower outside the cell than inside so water moves out of the cell by osmosis causing plasmolysis where cytoplasm shrivels and pulls away from cell wall
What is active transport?
The transport of molecules from a lower concentration that higher concentration which requires energy
Where is energy from active transport of molecules obtained from?
Respiration which uses ATP
ATP hydrolysed into ADP which releases energy
What does active transport use?
Protein pumps
How does active transport work?
Substance transported attaches to protein pump + ATP binds to protein pump
ATP hydrolysed to ADP + Pi which binds to protein pump so energy given to change tertiary structure and transport molecule
How are cells adapted to carry out active transport ?
Requires energy thus production of ATP so fell requires many mitochondria
Requires many protein pumps
What is Co transport?
The transport of
Why are Membrane transport proteins specific to a substance?
Protein has specific tertiary structure so is specific to a particular ion/ molecule
Based on this ion/molecule’s charge, size, shape etc
Relationship between rate of simple diffusion and concentration gradient
Directly proportional
Relationship between rate of facilitated diffusion and concentration gradient
Starts off directly proportional
Reaches maximum rate once transport proteins become saturated with substance = levels off
Equilibrium reached
Once the concentration of substance/ water potential on both sides is equal so the rate at which diffusion occurs back and forth is EQUAL = no net movement of substances in either direction
Adaptations of ileum cells to maximise absorption
FOLDED CELL SURFACE MEMBRANE to maximise absorption
Large number of carrier/ channel proteins so FAST RATE OF ABSORPTION
Large number of mitochondria for more aerobic respiration to produce more ATP
