Chapter 3 - Movement into and out of cells Flashcards
What is diffusion?
Diffusion is the net movement of particles from a region of their higher concentration to a region of their lower concentration down a concentration gradient as a result of their random movement.
Where does the energy from diffusion come from?
The energy for diffusion comes from the kinetic energy of random movement of molecules and ions
What stops some substances from diffusing into and out of cells?
Some substances move into and out of the cell by diffusion through the cell membrane which is partially permeable meaning it allows some molecules to cross easily but others with difficulty or not at all.
How does diffusion help organisms?
Diffusion helps organisms to obtain many of their requirements, get rid of many of their waste products and carry out gas exchange for respiration.
What are some examples of diffusion?
What four factors affect the rate of diffusion?
Surface area, temperature, concentration gradient and distance.
How does surface area affect the rate of diffusion?
The bigger a cell or structure is, the smaller its surface are to volume ration is. This slows down the rate at which substances can move across its surface. Many cells that are adapted for diffusion have increased surface area in some way
How does distance affect the rate of diffusion?
The smaller the distance molecules have to travel; the faster diffusion will occur.
How does temperature affect the rate of diffusion?
The higher the temperature, the faster the molecules will move as they have more energy. This will result in more collisions against the cell membrane and therefore a faster rate of movement across them.
How does the concentration gradient affect the rate of diffusion?
The greater the difference in concentration gradient on either side of the membrane, the faster movement across it will occur. This is because on the side with the higher concentration, more random collisions against the membrane will occur.
What is water?
Water is important for all living organisms as many substances are able to dissolve in it as a solvent. This allows dissolved substances to easily be transported around organisms, digested food molecules can be moved to cells all over the body, toxic substances such as urea can dissolve in water which makes them easy to remove from the body and water is also an important part of the cytoplasm and ensure metabolic reactions can happen.
What is osmosis?
Osmosis is the net movement of water molecules from a region of high-water potential (dilute solution) to a region of lower water potential (concentrated solution), down a concentration gradient, through a partially permeable membrane. Water moves into and out of cells by osmosis through the cell membrane.
How does a plant become turgid?
When a plant cell is placed in a solution that has a higher water potential (dilute solution) than inside the cell, the water moves into the plant cell via osmosis. These water molecules push the cell membrane against the cell wall, increasing turgor pressure in the cells which then makes them turgid.
How does a plant become flaccid?
When a plant cell is placed in a concentrated solution (with a lower water potential than inside the cell) water molecules will move out of the plant cell by osmosis, making them flaccid. If plant cells become flaccid, it can negatively affect the plants’ ability to support itself.
What is plasmolysis?
Plasmolysis means that the cell membrane has pulled away from the cell wall.
Compare a turgid cell and a flaccid cell
Compare cells in a hypertonic, isotonic and hypotonic solution
How does active transport work?
Active transport works by using carrier proteins embedded in the cell membrane to pick up specific molecules and take them through the cell membrane against their concentration gradient
Describe the process of active transport
- Substance combines with carrier protein molecule in the cell membrane.
- Carrier transports substances cross membrane using energy from respiration to give them the kinetic energy needed to change shape and move the substance through the cell.
- Substance is released into the cell.
