chapter 2.4 movement of substances Flashcards
Substances move in and out of cells by processes such as: diffusion, facilitated diffusion, osmosis, active transport, endocytosis, exocytosis. Explain how the structure of a membrane facilitates different processes of movement through it. Explain how factors affect the exchange of materials across membranes including: surface-area-to-volume ratio of the cell, concentration gradients, the physical and chemical nature of the materials being exchanged. Cells require an input of matter, includin
What are some cell requirements?
In order to surive cells, require an input of matter including gases, simple nutrients and ions as well as an output/ removal of waste.
What proccesses are used to move substances in and out of the cell?
Substances move in and out of cells by processes such as:* diffusion, facilitated diffusion, osmosis, active transport, endocytosis, exocytosis.*
What are passive transport proccesses?
Passive transport proccesses are types of membrane transport which do not require energy to move across cell membrane.
Types of passive transport include: simple diffusion, facilated diffusion and osmosis
What is simple diffusion?
For small uncharged particles/ molecules e.g. oxygen or carbon dioxide, these molecules can move between the phospholipids with no energy. These molecules move from an area of high concentration to an area of low concentration.
What is facilitated diffusion?
For larger or charged molecules, which have to use a protein (to travel through a channel) e.g. sodium, potassium, chlorine (ions and salts). Again it uses no energy and moves from a high concentration to a low concentration.
What is osmosis?
Osmosis is the movement of water through a semi permeable membrane.
Water molecules are so small that they travel through the membrane without assistance. Or they travel through larger quantites through protein channels like aquaporins. (does not require energy)
In osmosis water molecules travel from areas of high concentration to low conconentration. Or a low solute (more water) to a high solute (less water).
Solutes are like sugar and salt.
Osmois trys to dilute the high solute concetration to a low solute concentration.
What are the terms isotonic, hypotonic and hypertonic.
Isotonic: **solution that has the same solute concentration and water concentration
Hypotonic: **solution that has a low solute concentration and high water concentration
hypertonic ** solution that has a high solute concentration and low water concentration
What is active transport
Active transport is the movement of materials across a semi permable, requiring ATP moving against the concentration. Active trasport uses a protein pump or ion pump to push all molecules to one side, where the molcules move through a protein.
What is endocytosis?
Requires ATP(active transport) and looks at bringing larger molecules (or particles in bulk) into the cell:
- Essentially vacuoles (or vesicles) form from the cell membrane as a section of the cell memebrane forms a small depression which encloses the molecules that move into the cell. The cell membrane fuses and the vesicle is pinched off and moved by the cytoskeleton into the cell.
What is exocytosis?
Requires ATP(active transport) and looks at removing large molecules (or particles in bulk) out of the cell:
- Molecules are packaged inside vesicles which are then transported to the cell membrane by cytoskeleton. These fuse with the cell memebrane which then opens to release the molecules outside of the cell.
Efficiency of these processes can be affected by what factors?
-** Surface to volume ratio:**
Essentially (smaller the cell) the larger the SA:V the greater the efficency of the exchnage of materials. To calculate SA:V find surface area = length x width x (amount of sides) to find volume length x width x depth then write as ratio
- Concentration gradient:
A stronger concentration gradient (larger concentration difference between regions) results in faster diffusion.
- **Nature of the substances being exchanged:
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