5.3- Diffusion Flashcards
Whta is simple diffusion>
The net movement of particles from a region of high to low concentration
PASSIVE
Why does simple diffusion occur
The particles in gas or liquid have kinetic energy
This movement is random adn an unequal distribution eventual becomes equal - particles on stop but movement is equal in both directions
Why is diffusion fast over fast distance but slow over large
Because particles move at high speed
Collid lots- large
Plasma membrane- simple diffusion
Small lipid soluble, uncharged molecules
Random process relying on kinetic energy of particles
E,g, o2, co2, h20, steroid hormones
What is facilitate diffusion
The hydrophobic interior of the membrane repels substances sith a positive or negative charge
Polar molecules e.g. H20 move at SLOW rate
Transmembrane channels- gated , open adn closed - regulating flow of ions or small polar molecules
Can also involve carrier proteins which change chaos when a specific molecule binds
Carrier proteins
Down a. Concentration gradient
Doesn’t require EXTERNAL energy
PASSIVE
Factors affecting rate of diffusion
Temperature- higher temp= higher rate of diffusion= more Ke adn more speed
Concentration difference= greater means faster
Surface area= as surface area to volume ratio increase sm so does diffusion rate
Distance- greater= slower
Size of molecule
Simple diffusion summar
I assisted diffusion
Occurs through phospholipids
Transports small, non polar particles
Occurs directly through cell surface membranes
Rat of diffusion is directly proportional to concentration gradient and membrane permeability of solute molecule
FACILITATED diffusion summary
Transport a substance across a biological membrane
Carrier protein or protein channels
Movement of molecules down grading
Large and polar
Rate depends on kinetics of carrier- meditated transport
Differentiation
Different cell types have differnent membranes with different proportions of protein channels and carriers
Why is diffusion not enough to met the needs of the cell
Moving LARGE amounts
Ensuring one way flow
Concentration gradient- so you can go from low to high
Speed - diffusion isn’t very fast
What is active transport
The movement of ions or molecules against concentration gradient across membranes
Uses ATP to drive protein ‘oumps’ within membrane
Active transport across plasma membranes
- The molecule or ion binds t the receptors in the channel f the carrier protein on the outside of the cel
- On the inside of the cell , atom binds to the carrier protein adn is hydrolysed to ADP adn Pi
- Binding of the phosphate molecule to the carrier protiens causes the protein to change shape ( active configuration) opening up to the inside of the cell
- The molecule or ion is released inside the cell
- The phosphate molecule is released form the carrier protein and recombined with ADP to form ATP
- The carrier protein returns to original shape ( binding configuration ) available to take up glucose
What is bulk transport
Another form of active transport
Large molecules like enzymes , hormones or whole cells like bacteria are too large to move through channel or Carrier proteins
Phagocytosis
Solids
