Diffusion, Active Transport, osmosis and Co Transport Flashcards
What is the definition of simple diffusion?
Net movement of molecules or ions from a region of high concentration to a region of low concentration down a concentration gradient until evenly distributed
How do molecules made by simple diffusion across the membrane?
Move in the small gaps in the phospholipid bilayer
What molecules can move across the membrane by simple diffusion?
Lipid soluble Non- polar small molecules
Why can charged ions and polar molecules not diffuse across the membrane by simple diffusion?
Tails of phospholipid bilayer are hydrophobic so polar molecules can’t pass through them
What is facilitated diffusion?
A passive process down a concentration gradient which involves cartier and channel proteins
What are channel proteins and how do they pass molecules across the cell surface membrane?
Form water filled hydrophilic channels across the membrane where specific water soluble ions pass through they are selective with what ions pass through. Ions bind to proteins that changes shape closes one side and opens the other side of the membrane.
What are carrier proteins and how do they work?
Used for larger molecules such as glucose and amino acids causes it to change shape of molecules released to the inside of the membrane.
Why does the facilitated diffusion curve level off?
Saturation rate because the number of transport and carrier proteins limit the rate of diffusion
What are the 5 factors affecting the rate of diffusion?
- Concentration gradient
- Temperature
- Number of transport proteins in membrane
- Surface area of membrane
- Contains correct transport proteins
What is the definition of active transport?
The movement of molecules or ions into or out of a cell from a region of lower concentration to a region of higher concentration using ATP and carrier proteins
Why does active transport require ATP?
Moves molecules against a concentration gradient
In active transport what do carrier protein molecules act as?
Pumps
What so carrier proteins do in ATP?
Span membrane bind to molecule on one side and ATP binds to protein so splits into ADP and phosphate molecule. The protein changes shape opens to the opposite side of the membrane phosphate molecule is released and reverts the protein to it’s original shape.
What is the definition of cotransport?
The movement of two or more molecules or ions across the membrane together
What does symport mean in terms of cotransport?
Molecules or ions move in the same direction
What does antiport mean in terms of cotransport?
Molecules or ions move is opposite directions
What are the 5 stages of the cotransport of glucose and sodium ions?
- Sodium ions actively pumped by sodium potassium pump out if epithelial cells and into the blood
- Now have a low conc of sodium ions in epithelial cells compared to intestine lumen
- Na ions diffuse down conc gradient from lumen to epithelial cells
- Drives cotransport of glucose molecules from lumen to epithelial cells
- Glucose diffuses out the epithelial cells into the blood by facilitated diffusion down conc gradient
What is bulk transport used for?
Particularly large molecules
What is endocytosis?
Process of taking large particles into a cell by taking it into a vesicle
What is exocytosis?
Release of large particles from the inside to outside of the cell released out of a vesicle
What is the definition of osmosis?
The passage of water from a region where it has higher water potential to a region where it has a lower water potential through a selectively permeable membrane
What greek letter is water potential represented by?
Psi
What is water potential measured in?
Kilopascals
What is pure waters water potential?
0
What does an addition of solute do?
Lowers water potential makes it negative
How do you find the water potential of cells in the potato practical?
When it is isotonic and there is no net loss or gain so it must be the same water potential as the cell
What happens when the cell is higher and what is it called?
Hypotonic the cell is turgid water enters cell swells and bursts in a plant cell the protoplast is pushed against protoplast
What happens when the cell water potential is the same and what is it called?
Isotonic no change in water potential in plant cells it is in incipient plasmolysis protoplast slightly pulled away only small gaps
What is it called when the water potential is lower in the cell and plant cell?
Hypertonic leaves cells so they shrink in plant cells they become flaccid and so the protoplast completely pulls away from the cell wall
What does water potential in the cell equal?
Solute potential add pressure potential
