1.4 Cell transport Flashcards
Simple diffusion
Movement of particles from a region of high concentration to low concentration, down the concentration gradient.
Why does diffusion occur?
It is due to the random movement of particles
What molecules diffuse simply?
For molecules that are small, uncharged and/or non-polar
Does simple diffusion require selectively permeable membrane?
Yes and no. Usually doesn’t but eg. in alveoli it is required for gases
Factors that affect simple diffusion
- Temperature: Higher = faster diffusion
- Surface area: Increase allows more molecules to diffuse
- Concentration gradient: Bigger gradient, faster diffusion
- Size of particles: Smaller ones diffuse faster
How is facilitated diffusion different?
Requires channel proteins or carrier proteins. Size and shape are specific to molecules being transported. For molecules that are too big, polar or charged
Example of facilitated diffusion
Function of neurons: Movement of K+ ions in neurons during generation of an action potential.
Osmosis
Passive movement of water molecules from region of lower solute conc. to higher solute conc. across a partially permeable membrane
How is osmosis different from diffusion?
Only involves water molecules
Why do tissues (eg. transplant operations) need to be kept in saline solutions?
Osmolarity of saline solution must be same as that of cytoplasm in cells of tissue to prevent osmosis that would damage the cells
3 terms for differences in solute concentrations between two solutions
Hypertonic, isotonic, hypotonic
Hypertonic
When there is higher conc. of solutes
Hypotonic
When there is less conc. of solutes (eg. more water, less ions)
Relation b/w hypertonic and hypotonic
Relative relationship. Water always moves by osmosis from hypotonic solution to hypertonic solution
Isotonic
When conc. of solutes is equal
Placing a red blood cell in a hypotonic solution
Water will move into cell and cause it to swell. Eventually it will burst
Placing a red blood cell in a hypertonic solution
Water will move out of the cell and it will shrivel up.
Placing a red blood cell in an isotonic solution
No net movement of water
Active transport
Movement of particles across membranes, using energy in the form of ATP
Why is ATP required for active transport?
To move substances against the concentration gradient (lower to higher conc.)
Why do roots in plants use active transport?
Minerals are in lower concentration in the soil so they can’t diffuse naturally. Hence roots use energy to move these substances in.
Active transport by Na+/K+ pumps
- Pump opens to inside of axon and three Na+ ions enter pump and attach to their binding sites
- ATP donates phosphate group causing protein to change shape expelling Na+
- Two K+ ions attach to pump which releases phosphate
- Pumps opens to inside of axon again and expels K+
- Cycle is repeated
2 stages of endocytosis
Phagocytosis and pinocytosis
Difference between phago/pinocytosis
Pinocytosis is taking in of liquid substances by cells. Phagocytosis is absorption of solids
Example of phagocytosis (hint: WBC)
When white blood cell or phagocyte engulfs a pathogenic microbe
Endocytosis
Cellular process where cells take in molecules or substances from outside of cell by engulfing
Why is endo and exocytosis important?
Critical to survival since many important molecules cannot normally pass through cell’s hydrophobic plasma membrane
Exocytosis
Ejection of waste products from inside of cell
Can exocytosis also include useful substances?
Yes. One example could be release of hormones
2 types of exocytosis
Excretion and secretion
Excretion (exocytosis)
Undigested remains after phagocytosis that are not useful are ejected
Secretion (exocytosis)
Proteins synthesized by ribosomes on rER are passed to Golgi via vesicles to be processed and packaged before more vesicles fuse with plasma membrane for secretion
Role of vesicles
Allows cells to move molecules around inside the cell.
IV and DV in a osmosis experiment to test which solution is hypertonic and hypotonic
IV: Concentration of solution (eg. NaCl)
DV: Length or percentage change in mass of eg. plant tissue or potato tube
Difference between primary and secondary active transport
Primary requires ATP while secondary uses energy produced when a solute moves down the (electrochemical) concentration gradient
