Bio Chapter 2 - Movement of Substances Flashcards
What is the definition of diffusion
Diffusion is the het movement of particles from a region of higher concentration to a region of lower concentration that is, down a concentration gradient, not requiring a membrane
Name two examples of diffusion occurring
Gaseous exchange in human lungs
Gaseous exchange in leaves
How does diffusion occur in the gaseous exchange in human lungs?
Oxygen diffuses into the bloodin the blood capillaries from the alveolus, small air sacs surrounded by a network of blood capillaries
Carbon dioxide diffuses out of the blood capillaries to the alveolus
How does diffusion occur during photosynthesis
When plants photosynthesise,
There is a net movement of carbon dioxide into the leaf from the atmosphere
Het movement of oxygen and water vapour out of leaf to the atmosphere
How does diffusion our when plants are not photosynthesising
Net movement of oxygen into leaf from the atmosphere
Net movement of carbon dioxide and water vapour out the leaf to the atmosphere
What are the three factors that affect the rate of diffusion and osmosis?
Diffusion/ osmosis distance
Concentration / water potential gradient
Surface area to volume ratio
What is the relationship between diffusion/ osmosis distance and the rate of diffusion/osmosis
The shorter the diffusion/osmosis distance, the higher the rate of diffusion
Name and describe an example of short diffusion distance
Cells in the wall of the alveolussome one cell thick, decreasing diffusion distance that carbon dioxide molecules have to pass through from blood capillaries to the alveolus
And for oxygen molecules to pass through from alveolus into blood capillaries
Thus, increasing rate of diffusion of carbon dioxide and oxygen
What is the relationship between surface areato volume ratio and the rate of diffusion / osmosis
The greater the surfaceareato volume ratio, the higher the rate of diffusion / osmosis
Name and describe an example of increased surface area to volume ratio increasing the rate of diffusion
The epithelial cell has microvilli that helps to increase rate of digested nutrients from small intestine into the cell by increasing surface area to volume ratio
What is the relationship between the concentration of particles / water potential and the rate of diffusion/osmosis
The greater the difference in concentration of particles / water potential, the faster the rate of diffusion
What is the definition osmosis
The net movement of watermorelures from a solution of higher water potential to a solution lower potential , through a partially permeable membrane, that is, down a water potential gradient
What is water potential?
Measure of tendency of water molecules to move from one place to another down a water potential gradient
What happens when a plant cell is placed in a solution of higher water potential
The cell sap has a lower water potential than that of the external solution
By osmosis, water molecules enter the cell through the partially permeable cell membrane
As water molecules enter the cell, vacuole increases in size and pushes the cytoplasm against the cell wall
The cell does not burst as it is protected by inelastic cell wall
As a result, the cell expands and becomes turgid
What happens when a plant cell is placed in a solution of lower water potential
The cell sap has a higher water potential than the external solution
By osmosis, water molecules from the vacuole and cytoplasm leave the cell through the partially permeable cell membrane
Plasmolysis occurs where as the cell loses water, vacuoles decreases in size and cytoplasm shrinks away from cell membrane.
As a result, the cell decreases in size and becomes flaccid or limp
What happens when an animal cell is placed in a solution of higher water potential
The cytoplasm has a lower water potential than the solution outside the cell
Water molecules more into the cell by osmosis
Animal cell will swell and may burst because unlike plants, animal cells do not have cell walls to protect them
What happens when an animal cell is placed in a solution of lower water potential
The cytoplasm has a higher water potential than the external solution
Water molecules move out of the cell by osmosis
Cremation occurs where animal cell shrinks and spikes appear on the cell surface
The cell will become dehydrated and eventually die
Why is turgor important in plants?
Young stems and leaves of herbaceous and non-woody plants are able to remain firm and erect because of turgor pressure within the cell
When there is a high rate of water loss, cells will lose turgidity and the plant will eventually wilt
Why is it not advisable to add excessive fertiliser around roots?
The soil solution will become very concentrated as water molecules leaving the roots by osmosis
What will happen if the roots are unable to absorb water while there is continued evaporation of water from leaves
Unless sufficient water is added to dilute the soil solution, the plant will eventually wilt
