3.2.3 (transport of substances) Flashcards
(27 cards)
What is simple diffusion?
Net movement of small/ non polar molecules down a concentration gradient until evenly distributed
What type of process is simple diffusion?
Passive
Depends on kinetic energy of molecules
How does temperature affect diffusion and why?
Increasing temperature increases kinetic energy of molecules and speeds up diffusion
What is diffusion rate proportional to?
(SA x difference in concentration gradient) / length of diffusion pathway
What is rate of diffusion proportional and inversely proportional to?
Proportional to surface area and concentration difference
Inversely proportional to thickness of membrane
How are cells adapted for faster diffusion across membranes?
Large surface area
-membranes folded
-many channel + carrier proteins
Maintained conc gradient
-blood flow, extensive capillary network
Thin diffusion pathway
-one cell thick
Describe facilitated diffusion
Large molecules and polar molecules can enter the cell by facilitated diffusion down their conc gradient with the aid of proteins
Passive process
Involves carrier and channel proteins
Describe channel proteins’ role in facilitated diffusion
Channel proteins form pores in the membrane
Charged particles can diffuse down their conc gradient
Different channel proteins will enable diffusion of different charged particles
Describe carrier protein’s roles in facilitated diffusion
Have specific shape to match the molecule they transport
When the molecule binds to the site the carrier protein changes shape
Molecule can then pass through to other side of membrane
Once molecule has left protein reverts back to its original shape
Name factors affecting rate of facilitated diffusion
Concentration gradient
Number of channel/ carrier proteins
How is active transport similar to facilitated diffusion?
Molecule attaches to carrier protein
Protein changes shape
Molecule moves across membrane and is released to other side
How is active transport different to facilitated diffusion?
AT requires energy wheres FD is passive
AT moves against conc gradient (low to high) whereas FD moves down conc gradient (high to low)
AT doesn’t use channel proteins
What are co-transporters?
A type of carrier protein
Binds to 2 molecules at same time
Concentration gradient of one molecule used to move a different molecule against its own concentration gradient
Describe how co-transport is used to absorb glucose
- Na actively transported out of epithelial cells into blood via sodium-potassium pump (K diffuses into e. cells as a byproduct)
- Na diffuses from ileum into epithelial cells down conc gradient via sodium-glucose co transporters
- Glucose moves from epithelial cells to blood via facilitated diffusion through a channel protein
What is osmosis?
Movement of water molecules
Across partially permeable membrane
From high water potential to low water potential
What is the symbol for water potential and what is it measured in?
Water potential = ψ
Measured in kPa
What is the water potential of pure water and therefore why is the water potential of any solution negative?
Pure water = water potential of zero
Higher concentration of solute= more negative water potential
Define hypertonic
When the solution has a lower water potential than in the cell
Define isotonic
When the water potential inside the cell is the same as outside the cell
Define hypotonic
When the solution has a higher water potential than in the cell
Describe what would happen to a cell in a hypertonic, isotonic and hypotonic solution
Hypertonic- water would exit the cell
Isotonic- no net movement of water
Hypotonic- water would enter the cell
Define flaccid
The result of an animal cell being placed in a hypertonic solution
Water has exited the cell by osmosis
Define hemolysed
The result of an animal cell being placed in a hypotonic solution
Water has entered the cell by osmosis
Define plasmolysis
The process of a plant cell being placed in a hypertonic solution
Water has exited the cell by osmosis
