Exchange + Transport Flashcards
What is diffusion?
Diffusion is the movement of molecules from an area of high concentration to an area of low concentration due to random movement of molecules driven by kinetic energy.
What factors affect the rate of diffusion?
The factors affecting the rate of diffusion include:
- Steepness of the concentration gradient
- Temperature
- Surface area to volume ratio (SA:V), which decreases as organisms increase in size
- Properties of molecules (small, non-polar, uncharged molecules are fastest as they are soluble in the phospholipid bilayer)
- Thickness of the exchange surface
- Number of channel/carrier proteins available.
What is facilitated diffusion?
Facilitated diffusion is the movement of large, polar molecules or charged ions across a membrane, enabled by channel or carrier proteins.
What is the role of channel proteins in facilitated diffusion?
Channel proteins are water-filled and gated by specific stimuli. They control the movement of ions by changing shape.
What is the role of carrier proteins in facilitated diffusion?
Carrier proteins change shape to allow the passage of molecules. They may be open on one side of the membrane first.
What is osmosis?
Osmosis is the movement of water from an area of high water potential to an area of low water potential across a partially permeable membrane.
What is the water potential of water and solutions?
The water potential of pure water is 0, and the water potential of solutions is negative, measured in kilopascals (kPa).
What is a hypertonic environment?
A hypertonic environment has a higher concentration of solutes (a concentrated solution) outside the cell, causing water to move out of the cell, leading it to shrivel (crenate).
What is a hypotonic environment?
A hypotonic environment has a lower concentration of solutes (a dilute solution) outside the cell, causing water to move into the cell, leading to cell lysis.
What is an isotonic environment?
An isotonic environment has equal concentrations of solutes inside and outside the cell, resulting in no net movement of water.
What is active transport?
Active transport is the movement of substances from a low concentration to a high concentration using energy released by respiration. ATP is hydrolyzed to release energy to change the shape of the complementary carrier protein.
What is the importance of active transport?
Active transport is important for processes such as selective reabsorption in kidney tubules and absorption in the digestive tract.
What is co-transport?
Co-transport is the combination of facilitated diffusion and active transport, where the movement of certain molecules depends on each other.
How does co-transport work in the epithelium of the ileum?
In the ileum:
- Sodium ions (Na+) move into the cell via active transport, creating an Na+ concentration gradient.
- Sodium ions then move down the concentration gradient via facilitated diffusion, coupled with glucose molecules that are transported by co-transport proteins.
- This increases the glucose concentration inside the cell, creating a concentration gradient that allows glucose to move in by facilitated diffusion.
What is bulk transport?
Bulk transport is an active process involving the movement of large molecules into or out of the cell.
What is endocytosis?
Endocytosis is the movement of large molecules into the cell, where the cell membrane engulfs material and forms an endocytic vacuole around it. An example is phagocytosis (solid material) or pinocytosis (liquid material).
Label the spirometers graph correctly
