Lecture 13: Membrane Transport Flashcards
Describe random molecular movement.
What is its role in moving materials within organisms and between organisms and their environment?
Each molecule in a population has its own random movement and can go in any direction
the random movement of individual molecules allows some to move through pores while the net population flows down a concentration gradient
Describe simple diffusion - What is its role in moving materials within organisms and between organisms and their environment?
SPONTANEOUS movement of a population of molecules from an area of HIGH concentration –> LOW concentration (down their concentration gradient) DIRECTLY ACROSS A PLASMA MEMBRANE
Describe facilitated diffusion - What is its role in moving materials within organisms and between organisms and their environment? Give an example.
Facilitated diffusion is when molecules move down their concentration gradient across a plasma membrane with the HELP of TRANSPORT PROTEINS
- these molecules are too large to cross on their own
- this process does not require energy
- does require a concentrate gradient
ex. water diffuses quickly across the cell membrane through transport proteins called aquaporins.
Describe osmosis - What is its role in moving materials within organisms and between organisms and their environment?
A type of diffusion that occurs for water molecules.
It is the movement of water in relation to other molecules when they are blocked by a selectively permeable membrane
- water will move until the solutions reach equilibrium
Describe active transport - What is its role in moving materials within organisms and between organisms and their environment?
the movement of a population of molecules from areas of LOW concentration –> HIGH concentration (AGAINST the concentration gradient)
cell membrane allows reactants to build up
*requires energy (ATP) and a transport protein
Describe isotonic solutions
the same concentration or they are at equilibrium
Describe hypertonic solutions
Higher solute concentration than the solution it is compared to
Describe hypotonic solutions
Lower solute concentration than the solution it is compared to
How do hypertonic solutions effect plant and animal cells?
ANIMAL cell in a hypertonic solution:
- water will leave the cell because there is more water inside than outside
-
How do hypotonic solutions effect plant and animal cells?
ANIMAL cell in a hypotonic solution:
- water will move into the cell because
How do isotonic solutions effect plant and animal cells?
ANIMAL:
Net movement of water is from a ____ solution –> a ____ solution
a HYPOtonic solution to a HYPERtonic solution
When a plant cell is in hypotonic solution, it becomes ___?
Turgid because water is moving into the cell and filling it up, but the cell wall keeps it from exploding
When a plant cell is in hypertonic solution, it becomes ___?
Plasmolyzed because water is leaving the cell and so the membrane will peel away from the cell wall
When a plant cell is in isotonic solution, it becomes ___?
Flaccid because water is moving in and out at the same rate.
When a plant cell is in isotonic solution, it becomes ___?
Flaccid because water is moving in and out at the same rate.
Define transport proteins
Proteins embedded in the plasma membrane help move molecules across a membrane they are too large to permeate
What’s an example of a molecule that’s too large to cross a membrane on its own?
sugar
charged molecules like Na+, Cl-
Describe aquaporins and their function
Aquaporins are a special transport protein that facilitate the diffusion of water through a membrane
Describe passive transport - which processes are considered passive?
the movement of a population of molecules from areas of high concentration to areas of low concentration (down a concentration gradient)
* no energy is required = why it’s called passive
- Simple diffusion
- facilitated diffusion
- osmosis
Describe endocytosis
the plasma membrane folds in and surrounds a molecule for transport, then pinches off from the plasma membrane to form a vesicle inside the cell
a mechanism of bulk transport across a membrane
describe exocytosis
vesicle inside cell fuses with plasma membrane and the vesicle contents are released outside the cell
When does endocytosis/exocytosis occur?
When molecules are too big to move through transport membranes, they can be moved through vesicles
What are the two mechanisms of bulk transport? do they require energy?
- endocytosis
- exocytosis
both require energy and are the transport of large molecules surrounded in plasma membrane
