Level 2 Bio: Cell transport Flashcards
What are the 2 types of cell transport
Passive transport and Active transport
What is passive transport
Movement of molecules across the cell membrane. Does NOT require energy.
What is active transport
Requires energy (ATP)
What are the 3 main types of passive transport
(dependent on the permeability of the cell membrane)
- Diffusion
- Osmosis
- Facilitated Diffusion
What is Diffusion
Diffusion is the movement of molecules from an area of high concentration to one of low concentration, along/down the concentration gradient. It uses no energy.
What are some examples of diffusion
Smelling perfume across a room, dye spreading through water, smelling dinner while in the lounge.
What is the concentration gradient
For things to diffuse there must be a difference in concentration between two areas. If not, the particles wont be able to move to a lower concentration. The bigger the difference in concentration the faster it will diffuse.
What does the rate of diffusion depend on
- The concentration gradient (bigger difference=faster diffusion.)
- Temperature (warmer=faster diffusion.)
- Particle size (smaller=faster diffusion.)
- State of matter (gas=faster diffusion.)
What is facilitated diffusion
Substances are helped across the membrane by carrier proteins. It still uses no energy but the proteins are specific to certain molecules.
EXAMPLE:
(cells absorb glucose by facilitated diffusion. Insulin activates the transport proteins, if insulin is not there- can’t absorb glucose).
EXTRA INFO:
The cell membrane is impermeable to most electrically charged molecules and large water soluble substances such as glucose and amino aids. Proteins embedded in the membrane contain channels that the large molecules diffuse through.
What are the differences between diffusion and facilitated diffusion
Facilitated diffusion is the movement of larger molecules with the aid of protein channels. Diffusion is the movement of molecules from an area of high concentration to one of lower concentration without protein channels.
What are the similarities between diffusion and facilitated diffusion
They both don’t require energy. (Passive) diffusion occurs along/down a concentration gradient.
What is Osmosis
Osmosis is the movement of water from an area of high concentration to one of low concentration down the concentration gradient via a semi permeable membrane.
When the concentration of water is the same on both sides of the membrane, the rate of movement of water will be the same in both directions. At this point, the net exchange of water will be zero and the system is in equilibrium.
For the concentration of water to be lower means that it must have something else in it (sugar, salt, ions etc).
What is Osmoregulation
The balancing of water inside an organism. Cells have to keep their water content balanced or else they either get too full or too empty of water.
In animals, too much water makes the cell pop and too little makes them shrivel.
What are the 3 ‘conditions’ a cell can be in
- Hypertonic
- Isotonic
- Hypotonic
What is Isotonic
Isotonic means balanced, Outside the cell and inside the cell have the same amount of water and solute as each other.
Equal amount going in and out, end result = NORMAL HEALTHY CELL
What is Hypertonic
The fluid outside the cell has HIGH SOLUTE (less WATER). The fluid inside the cell has LOWER SOLUTE (MORE WATER).
Water comes out and tries to balance the water outside the cell, end result = SHRIVELED CELL
What is Hypotonic
The fluid outside the cell has LOW SOLUTE (higher WATER). The fluid inside the cell has HIGHER SOLUTE (LESS WATER)
Water goes in and tries to balance the water in the cell, end result = CELL either POPS or gets OVER FULL of WATER
What are the main points of Tonicity
In Isotonic solutions cells have no net loss or gain of water.
Net loss of water due to osmosis in hypertonic solutions
Net gain of water due to osmosis in hypotonic solutions
Animal cells will shrivel or shrink in hypertonic solutions and expand or burst in hypotonic solutions
Plant cells become plasmolysed in hypertonic solutions-the cell membrane pulls away from the cell wall. Plant cells become firm in hypotonic solutions-hold their shape and are rigid or turgid.
What is Tonicity
Tonicity is a measure of the water potential gradient of two solutions (i.e solutions on either side of semi-permeable membrane).
What is water potential
Water potential is a measure of the tendency of water molecules to move from one place to another. Water always moves from a region of higher water potential (lower solute concentration) to one of lower water potential (high solute concentration) down the concentration gradient.
What is the process of lysis in animal cells?
If an animal cell is placed in a hypotonic solution (low solute, high water) it will gain water, swell and eventually burst. Once this happens the cell is said to be lysed.
If the cell is placed into a hypertonic solution (high solute, low water) it will lose water and shrivel up.
What happens to a plant cell if it is placed in a hypotonic solution?
It will gain water, however the cell wall is rigid and so pressure builds up inside the cell. This prevents an excessive amount of water entering the cell and also stops the cell from bursting. When a plant cell is completely fill with water it is said to be TURGID. The pressure on the cell wall is called TURGOR PRESSURE and this helps keep on woody plants upright.
What happens to a plant cell if it is placed in a hypertonic solution?
The plant cell loses water, and hence turgor pressure, making the plant cell FLACCID. Plants with cells in this condition wilt, but can recover if water is made available. Further water loss causes plasmolysis which is when the pressure decreases to the point where the cell membrane peels away from the cell wall, leaving gaps between the cell wall and the membrane. After PLASMOLYSIS the cell is said to be PLAMSOLYSED.
Active transport definition
Active transport is the movement of molecules and ions through a cell membrane from a region of lower concentration to a region of higher concentration using energy from respiration.
What does active transport require
Carrier proteins (each carrier protein being specific for a particular type of molecule or ion).