Gas exchange. cell membranes and transport Flashcards
State Fick’s Law
SA x Conc. difference / thickness of GE surface
How are human lungs adapted for efficient GE?
- Large SA due to lots of alveoli air sacs
- Short diff distance: only two endotheliums must be crossed
- Maintenance of conc. grad. due to constant ventilation of air
What are some features of the phospholipid bilayer?
- Phospholipids: phosphate hydrophilic head, two hydrophobic fatty acid tails
- Glycolipids and glycoproteins are scattered
- Cholesterol creates rigidity by binding to the phospholipids
- Partially permeable: O2 and CO2 can diff. across, larger molecules require alternative transp.
Define osmosis
The net movement of water molecules from an area of high conc. to an area of low conc. across a partially permeable membrane.
Describe facilitated diffusion, a passive process
FD is for larger and or charged molecules. Carrier proteins: large molecules attach to the binding site, the protein changes shape and the molecule’s released inside the CM. Channel proteins: charged molecules diffuse down a pore in the CM. Both are specific.
Describe active transport
AT moves substances against a conc. grad. using ATP.
Uses carrier proteins.
Describe endocytosis
Endocytosis is used by the cell to ingest molecules too large for carrier proteins. Part of the membrane pinches off and engulfs the molecules, forming a vesicle, then releases it in the cell. ATP is required.
Describe exocytosis
Exocytosis is used to transport substances produced in the cell, like proteins, to the outside of the CM. Vesicles pinch off from the Golgi apparatus and fuse with the CM. ATP is required.