Chapter 3 Flashcards
Diffusion, Osmosis, Active transport
What is Diffusion?
Diffusion is the movement of molecules/ions from a region of higher concentration to a region of lower concentration down a concentration gradient as result of their random movement.
The energy for this comes from the kinetic energy of the random movement.
Some substances move through cell membrane.
What are the factors that affect the Rate of Diffusion?
The factors are:
-SURFACE AREA; The greater, the faster the rate
-TEMPERATURE; As temperatures rise, the rate increases (kinetic energy)
-CONCENTRATION GRADIENT; The greater the difference, the faster the rate
-DISTANCE; The shorter the distance, the faster the rate
+ MOLECULE SIZE; The larger the size, the slower the rate
What is Osmosis?
Osmosis is the movement of water molecules from region of higher water potential (dilute) to a region of lower water potential (concentrated) through a partially permeable membrane.
What is meant by Water potential?
It is a measure of whehter a solution is likely to gain or lose water molecules from another solution.
What is the main solvent?
Water. Its the main solvent in ogranisms like in digestion, excretion & transport.
Why is it important for animal cells to have isotonic concentrations in & out of cells?
- This is because:
- If water potential is higher outside, then it will move into the cell by Osmosis, swelling it up and causing it to burst
- If the water potential is lower outside, water leaves the cell by Osmosis, causing the cell to shrink.
- Any excessive uptake or loss damages cells
What is the liquid outside cells called?
It is called Tissue fluid.
How is a plant cell supported (by vacuole)?
Due to many particles in the cytoplasm and cell sap, concentration of water molecules reduce.
- As a result, water diffuses into the cell and pass into the vacuole by Osmosis.
- The vacuole presses outward pressure on the cell wall and cytoplasm, supporting the cell.
What does it mean by the cell wall is inelastic? How is this a benefit?
The cell well is inelastic, so it cannot be stretched.
This means that plant cells can resist excessive uptake of water, and wont burst.
The cells becomes rigid and supported.
What is meant by the term “Turgid”?
When a vacuole is pressing outward pressure on the cell wall, the plant cell becomes rigid/supported or TURGID.
The pressure exerted by vacuole is called TURGOR PRESSURE.
What is meant by the term “Flaccid”?
When a cell loses water by Osmosis, it is no longer supported and becomes Flaccid.
What is meant by the term “Plasmolysis”?
When a cell loses a lot of water, its cytoplasm shrinks away from the cell wall.
The cells become plasmolysed, and the shape is called CRENATED.
What is Active transport?
Active transport is the movement of particles from a region of lower concentration to a region of higher concentration, against the concentration gradient using energy from respiration.
What are Protein Carriers? (Carrier proteins)
Protein Carriers transport molecules and ions across a membrane during Active transport using the energy from respiration.
