Transport across Cell Membranes Flashcards
WHat is selective transport?
Selective transport - because only certain substances are able to cross.
What are the two types of transport that move substances needed by the cell into and out of the cell? What does each type mean?
Passive transport - No energy spent by cell
Active transport - Energy (ATP) is used
What is movement across cell membranes without an input of energy? What does it include?
Passive Transport. Includes diffusion, osmosis, and facilitated diffusion.
What is Brownian motion?
The fact that the particles that make up all matter are in constant, random motion. This random motion allows for the net movement of particles towards areas of lower concentration.
When is a state of equilibrium reached?
Once molecules are distributed evenly.
What is the concentration gradient?
The difference in concentration between two areas when a specific type of molecule is distributed unevenly.
Define diffusion
A type of passive transport. The random movement of molecules from an area of high to low concentration (across the concentration gradient)
Describe the movement of molecules/
Always move from high concentration to low concentration regardless of the number of other substances mixed with them.
What causes diffusion? What are the 3 factors that affect the rate of diffusion?
Molecular collisions cause diffusion. Factors that affect the rate of diffusion:
- Concentration gradient: Greater difference between 2 areas = faster diffusion.
- Temperature: Greater temp = faster particle movement
- Particle Size: Larger particle size = slower movement
Diffusion will continue until what state is reached?
A condition where the concentration of particles is equally distributed - equilibrium
At the point where equilibrium is reached, what will occur?
Dynamic equilibrium occurs. Diffusion stops but molecules continue to cross the membrane at an equal rate (back and forth, even distribution on both sides)
What is facilitated diffusion?
Uses transport proteins to aid, assist, or facilitate the diffusion of particles across the cell membrane. Charged or polar molecules which may have trouble crossing the cell membrane can use transport proteins. This is still a form of passive transport (no energy use)
What are transport proteins?
Membrane proteins that help move materials across the membrane. 2 types, recognized based on shape, size, and electrical charge. NO ENERGY USED
What are carrier proteins?
A membrane protein that changes shape to allow certain molecules to cross the cell membrane
Which type of membrane protein forms tunnel-like pores in the cell membrane, allowing electrically charged ions in and out of the cell?
Channel Proteins
