B2.1 Flashcards
What is diffusion
Diffusion is the overall movement of particles from an area of high concentration to an area of low concentration. They move down a concentration gradient.
- diffusion continues until the concentration of the particles are the same everywhere ( at this point the concentration gradient is 0)
Is energy transferred during diffusion?
No. It is a passive process
How do particles move?
Particles move constantly and randomly by diffusion
What key gases do we need to diffuse from our lungs to our blood stream?
Oxygen
What key nutrient do we need to diffuse from our blood stream to our muscle cells?
Glucose
Where do glucose and oxygen diffuse into?
The cells that need them (through the cell membrane)
Diffusion in your body?
Substances (oxygen, carbon dioxide, water, dissolved nutrients and urea) can move into and out of a cell or organism via diffusion.
This happens across the cell membrane which is selectively permeable
What factors affect the rate of diffusion?
- surface area
- concentration gradient
- distance
- temp
How does distance affect the rate of reaction
- decrease the amount of distance the particles needs to move, it will take less time to travel as it is a shorter distance
- decreasing distance, increases the rate of reaction
EXAMPLE: blood capillaries are only one cell thick. This increases the rate of diffusion of gases into and out of the blood stream.
How does concentration gradient affect diffusion?
- increase concentration gardening -> increase rate of reaction
- the steeper the gradient, the greater the overall movement of particles
- The greater the difference in concentration, the quicker the rate of diffusion.
EXAMPLE: as plant cells use carbon dioxide for photosynthesis, the carbon dioxide concentration inside the plant cells drops. This increases the diffusion rate of carbon dioxide into the cells.
How does surface area affect rate of diffusion?
- increasing the surface area allows more space for diffusion so more particles can move in one period of time
-The greater the surface area, the faster the rate of diffusion
EXAMPLE: the small intestine wall is highly folded, increasing the surface area that is in contact with the blood stream. This increases the rate of diffusion of molecules produced in digestion, such as glucose and amino acids.
How does temp affect the rate of diffusion
The higher the temperature, the more kinetic energy the particles will have, so they will move and mix more quickly.
- increases rare if diffusion
What is osmosis?
- Osmosis is a special type of diffusion. It is the diffusion of water molecules across a selectively permeable membrane. It explains how water gets into and out of cells.
- movement of water from an area of high water concentration to an area of low water concentration through a partially permeable membrane
Permeable meaning
Allows liquids or gases to go through it
What is water potential?
- water potential is the ability of water to leave its system.
- concentration of free water molecules
What is osmosis?
Osmosis is the movement of water molecules from a high water potential to a lower water potential (down a concentration gradient).
How does the water potential affect the rate if osmosis
The greater the difference in water potential, the greater the rate of osmosis
Explain the term ‘turgid’
When water enters the cell by osmosis and fills the vacuole. This pushes against the cell wall, making the cellturgid
Explain the term ‘flaccid’
When water moves out of the cell by osmosis, the vacuole shrinks and the cell becomes flaccid
EXPLAIN osmosis in plant cells if the concentration of the surroundings is the SAME:
If a Cell placed into a solution with the same concentration as its contents, There is no overall movement of water.
The cell remains the same
- water comes in and it goes out (same)
EXPLAIN osmosis in plant cells if the concentration of the surroundings has a HIGHER concentration (lower water potential)
If a Cell is placed into more concentrated solution, It loses water by osmosis.
The turgor (hardness) pressure falls. The cell becomes flaccid (soft).
Eventually the cell contents collapse away from the cell wall. This is called a plasmolysed cell.
- water only leaves the cell
EXPLAIN osmosis in plant cells if the concentration of the surroundings has a LOWER concentration (higher water potential )
Cell placed into a dilute solution. It takes up water by osmosis.
The pressure in the cell increases; this is called turgor (hardness) pressure.
The cell becomes firm or turgid.
- water only enters the cell
Describe osmosis in animal cells
Animal cells also take in and lose water by osmosis. They do not have a cell wall, so will change size and shape when put into solutions that are at a different concentration to the cell contents.
Example (animal cells): red blood cell
WHAT would happen if the surroundings had the same concentration as a cell contents?
Cell placed into a solution with the same water potential as its contents. There is no overall movement of water. The cell remains the same.
- water goes in and water goes out
Example (animal cells): red blood cells
What would happen if the surroundings had higher concentration (lower water potential) than cell contents?
Cell placed into a more concentrated solution. It loses water by osmosis.
The cell becomes crenated (it crinkles).
- water only goes our
Example (animal cell): red blood cells
What would happen if the surroundings have a lower concentration (higher water potential) than cell contents?
Cell placed into a solution that is more dilute than its contents.
It takes up water, swells, and may burst.
This is called lysis.
-water only goes in
Lysis meaning
the disintegration of a cell by rupture of the cell wall or membrane.
What is active transport
Active transport is the movement of dissolved molecules into or out of a cell through the cell membrane, from a region of lower concentration to a region of higher concentration.
The particles move against the concentration gradient ,using energy released during respiration
What are the 3 key features of active transport?
• particles are transported (pumped) against a concentration gradient
• ATP is required - this comes from respiration
• the process makes use of carrier proteins in the cell membrane.
Cells that carry out a lot of active transport contain a lot of…..
….mitochondria meaning that they can respire rapidly to produce large quantities of ATP.
What does the rate at which active transport can occur depend on?
The rate of respiration to produce the required ATP
What are carrier proteins?
-Carrier proteins are special proteins that span (stretch across) the width of the cell membrane.
-A particular molecule that the cell requires binds to a specific carrier protein.
-Energy is transferred from an energy store to the protein so that it can change shape or rotate.
-The carrier protein transports the molecule into the cell
The greater the respiration rate…
The greater the rate of active transport
Where are carrier proteins found in the cell?
Cell membrane
When is active transport used?
Whenever a substance needs to be moved against a concentration gradient
Examples of active transport: (e.g.1)
- One example is during digestion. In your small intestine carbohydrates are broken down into glucose.
-The glucose is actively transported into the bloodstream through the villi.
-The blood takes the glucose to wherever it is needed in the body.
Examples of active transport (e.g.2)
-Active transport is also used in nerve cells.
-A carrier protein actively pumps sodium ions out of the cell.
-At the same time potassium ions are pumped back in.
-The sodium potassium pump plays an important role in creating nerve impulses.
Examples of active transport:
Plants use active transport to take in minerals from the soil.
For example, plants need nitrate ions to make proteins for growth.
There is normally a lower concentration of nitrate ions in the soil water surrounding the roots than in the plant. The plant root hair cells use active transport to move these ions across the cell membrane and into the root cell
What is the difference between active transport and diffusion
Diffusion is the movement of particles from a high to lower concentration.
Active transport moves particles from low to higher concentration.
