Exchange across cell membranes Flashcards
What is diffusion?
The net movement of particles from a high concentration to a low concentration. Particles move down a concentration gradient.
What factors increase the rate of diffusion?
Higher concentration gradient
Thinner exchange surface
Large surface area
What is facilitated diffusion?
When large or charged molecules pass through the membrane via carrier proteins and channel proteins.
Why are transport proteins needed?
Large molecules can’t fit through and charge particles diffuse too slowly, so they help speed up the rate of diffusion
What do carrier proteins do?
Change shape to allow large molecules to fit through
What do channel proteins do?
Are pores in the membrane to allow charge particles to diffuse
Which increases the rate of facilitated diffusion?
Higher concentration
Increased number of carrier and channel proteins in membrane
What is osmosis?
Diffusion of water through a partially permeable membrane from a high concentration to a low concentration
What is water potential?
The likelihood water molecules will diffuse in and out of a solution.
Higher water potential = less negative
Lower water potential = more negative
What will adding a solute to water do to the water potential?
Lower the water potential
What increases the rate of osmosis?
Higher water potential gradient
Thin membrane
Large surface area
Explain isotonic, hypertonic and hypotonic solutions
Isotonic = no net movement
Hypertonic = net movement out of the cell
Hypotonic = net movement into the cell
What is active transport?
An active process the moves solutes from a low concentration to a high concentration
What does active transport require?
ATP (hydrolysis reaction)
What transporter protein is involved in active transport?
Carrier proteins
What are co-transporters?
A type of carrier protein
What do co-transporters do?
Bind 2 molecules at the same time . The concentration of one of the molecules is used to move the other molecule against its concentration gradient
What increases the rate of active transport?
Faster speed of individual carrier proteins
High numbers of carrier proteins
High rate of respiration
Availability of ATP
Explain the process of glucose and sodium ions
- Sodium ions actively transport out of the epithelial cells into the blood via a sodium potassium pump
- This creates a concentration gradient and causes ions to diffuse from lumen of ileum to epithelial cells down the concentration gradient by sodium glucose co-transporter proteins
- The co-transporters carry glucose into cell with the sodium. This increases the concentration of glucose in the cell
- Glucose diffuses out cell into the blood down the concentration gradient through a protein channel by facilitate diffusion
