Week 4b: Passive + Active Movement Flashcards
(33 cards)
What is diffusion?
Molecules move from regions of high concentrations to low concentration.
Diffusion is passive, meaning:
It does not require energy.
The greater the difference in concentration,
the steeper the gradient.
The steeper the gradient,
the more rapidly diffusion will occur.
Diffusion occurs: down or against the gradient?
Down the gradient - from a high concentration to a low concentration.
WHhy can only SMALL NON POLAR MOLECULES diffuse across the membrane?
The membrane is made of HYDROPHOBIC lipids.
What is osmosis?
The diffusion of water across a semi-permeable membrane, from a low to high concentration.
The effect of osmosis can be: (3)
- Hypertonic
- Isotonic
- Hypotonic
Hypertonic
A higher solute concentration than the cell
Isotonic
Same solute concentration as the cell
Hypotonic
A lower solute concentration than the cell
Osmotic pressure
Pressure causing water to move in it’s direction
Osmosis has a more significant effect on animal cells compared to plant cells. Why?
Animal cells lack a cell wall.
If an animal cell loses water:
It will become flaccid/shrivelled
If an animal cell gains too much water:
It will swell/burst
What is facilitated diffusion?
Diffusion of large and/or polar molecules, which need assistance in moving across the cell membrane
Proteins which allow molecules to move along concentration gradients:
- Channel proteins
- Carrier proteins
Channel proteins (function)
Provide a pore in the membrane for hydrophilic molecules such as glucose to move through
Carrier proteins (function)
Bind to a specific molecule which then changes its shape and release the molecule inside the cell
Why does facillitated diffusion not require an input of energy?
The molecules move along their concentration gradient
What is active transport?
Movement of solute molecules from a low concentration to a high concentration (against the gradient)
Does active transport require energy?
Yes, from ATP
How are carrier proteins used in active transport?
Change shape to move molecules
The movement of large molecules (ie: proteins) involve:
Membrane bound sacs called vesicles