UNIT 1: (1.2) Transport Across Cell Membranes Flashcards
What is the function of the cell membrane
Allow transport of molecules or ions in and out the cell
What is the cell membrane composed of ?
Phospholipid (fat) bilayer and protein molecules
What is the structure of the cell membrane called ?
What does it stand for ?
- Fluid mosaic
- Fluid : due to the constant movement of the phospholipid bilayer
- Mosaic : due to the patchy distribution of proteins throughout the bilayer
What is the definition of diffusion ?
Diffusion is the movement of molecules from a region of high concentration to a region of lower concentration down a concentration gradient
What type of transport is diffusion ?
Passive transport ( as it requires no energy )
What does it mean if the cell membrane is selectively permeable ?
It will only allow the passage of some molecules and not others
What is a concentration gradient ?
A concentration gradient is the difference in concentration between the regions of high concentration and low concentration.
What is passive transport ?
Passive transport involves the movement of molecules down a concentration gradient without using any energy
Why is diffusion important ?
multicellular organisms - it allows the movement of molecules like oxygen from the lungs into the blood .
unicellular organisms- allows it to obtain resources needed to survive like oxygen in it’s surrounding environment
What is the definition of osmosis ?
Osmosis is the movement of water molecules from a region of high water concentration to a region of lower water concentration though a selectively permeable membrane
What does osmosis only refer to ?
It only refers to the movement of water in and out of cells
What happens when a plant cell is placed in water or a dilute solution?
- water molecules move into the cell due to osmosis ( gains water )
- plant cell becomes turgid
- cell wall prevents it from bursting
What happens to a plant cell when placed in a solution of equal water concentration ?
- No net movement of water molecules due to lack of a water concentration gradient
- No change in appearance
What happens to a plant cell when placed in a concentrated solution ?
- water molecules move out of the cell due to osmosis ( loses water )
- plant cell becomes plasmolysed
What happens when a animal cell (red blood cell ) is placed in water or a dilute / weak solution ?
- water molecules move into the cell due to osmosis ( gains water )
- cell bursts
What happens when an animal cell ( red blood cell ) is placed in a solution of equal water concentration ?
- No net movement of water molecules due to the lack of a water concentration gradient
- No change in appearance
What happens when an animal cell ( red blood cell ) when placed in a strong solution ?
- water molecules move out of the cell due to osmosis ( lose water )
- cell shrinks
What is the definition of active transport ?
Active transport is the movement of molecules or ions by carrier proteins in the cell membrane from a region of low concentration to a region of higher concentration against a concentration gradient
What does active transport require ?
It requires energy in the form ATP as it moves against the concentration gradient
How is ATP produced ?
Produced by a chemical process called respiration.
What are factors that effect the rate of respiration?
- oxygen concentration
- Glucose availability
- Temperature
What does the rate of respiration also effect ?
Rate of active transport
What is an example of active transport in plants ?
Some seaweeds and corals accumulate iodine from sea water in their cells to a concentration hundreds of times greater that that in the surrounding water
What is an example of active transport in animal cells ?
Reabsorption of glucose from kidney tubules back into the bloodstream ensuring that glucose I not lost in urine .
What are examples of passive transport ?
- Diffusion
* Osmosis
What are solids, liquids and gases made up of ?
Small particals called molecules
