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).
What is the difference between the use of carrier proteins for active transport and facilitated diffusion.
They both use carrier proteins however Active transport requires energy. (The energy is required to make carrier protein change shape, allowing it to transfer the molecules or ions across the cell membrane. The energy required is provided by ATP (adenosine triphosphate) produced during respiration.)
What is an iron pump
This is where certain ions or molecules are pumped from one side of the cell membrane to the other.
Usually different ions need to be present to make the other ion change side.
What are the key points of Diffusion
There are two types of diffusion there is (simple) diffusion and facilitated diffusion.
Simple diffusion does not require energy it is the natural movement of molecules.
Facilitated diffusion requires no energy either. However substances are helped across the membrane via protein channels.
Facilitated diffusion is usually required for larger molecules.
What are the key points of Osmosis
Osmosis is a special kind of diffusion where water molecules move from an area of high concentration to an area of low concentration. Moving down the concentration gradient. Via a semi permeable membrane.
In animal cells the tonicity of the cell means that if it is hypotonic it will gain water and swell or burst. Plant cells gain water and become turgid.
What are the key points of Active transport
Active transport is the movement of molecules through the cell membrane from a lower to a higher concentration (up/against the concentration gradient) which requires energy (ATP) which it gets from cellular respiration.
Active transport requires carrier proteins.
Active transport is important in the reabsorption of useful molecules and ions into the blood after filtration into the kidney tubules, the absorption of some products from the digestive tract. The loading of inorganic ions from the soil into root hair cells and loading of sugars from photosynthesis of leaf cells into the phloem tissue for transportation around the plant.
What is an example of Diffusion
Oxygen molecule get diffused into the lungs.
What is an example of Osmosis
The movement of water into and out of vacuoles in plant cells.
What is an example of Active transport
The reabsorption of useful molecules and ions into the blood after filtration into the kidney tubules requires active transport.
What are the similarities between Diffusion, Osmosis & Active transport?
They are all different forms of transport/movement of molecules into and out of cells.
Osmosis & diffusion don’t require energy.
Osmosis & diffusion are both the movement of molecules from an area of high concentration to one of low concentration.
What are the differences between Diffusion, Osmosis & Active transport?
They all transport different types of molecules.
Some processes don’t require energy and some do.
Active transport is moving molecules from a low to high concentration. Osmosis and diffusion are moving molecules from a high to low concentration.
What is Cytosis
The transport of molecules or ions into or out of cells by the folding of the membrane. This happens when LOTS of molecules or large particles need to move in and out of a cell.
What are the 2 types of Cytosis
- Exocytosis (outward)
- Endocytosis (Inward)
What is Exocytosis
Exocytosis (secretion) often vesicles fuse with the cell membrane, expelling their contents. Common in secretory cells (glands e.t.c)
What is Endocytosis
Endocytosis is the process of a cell’s membrane stretching around a large particle in order to engulf it/take objects into the cell. There are two types: Phagocytosis (ingesting solid particles) and Pinocytosis (ingesting fluid particles)
What are the 2 types of Endocytosis and what do they do?
- Phagocytosis: Ingesting solid particles
- Pinocytosis: Ingesting fluid particles
What is active transport important in?
Reabsorption of useful molecules and ions into the blood after filtration into the kidney tubules.
Absorption of some products of digestion from the digestive tract.
Loading sugar from the photosynthesising cells of leaves in the phloem tissue for transport around the plan.
Loading inorganic ions from the soil into root hairs.
Give an example of diffusion
Oxygen diffusing from alveoli into the red blood cells.
Give an example of Facilitated diffusion
Glucose into cells: too large to pass through the membrane, so will diffuse throughs specific protein channels.
Give an example of Osmosis
Water entering blood from capillary cells.
Give an example of Active transport
To move nutrients from a low concentration to a high concentration (moving against the concentration gradient) in the digestive system.
Why do cells need to be so small?
Small cells are able to transport materials in and out relatively quickly compared to large cells. (SMALLER CELLS ARE MORE EFFICIENT THAN LARGER CELLS)
Cells die all the time so it is useful to have lots of extra cells
The cells in our body are specialised so we need many different types to complete different tasks.
What does SA:V ratio mean?
Surface Area to Volume ratio
What is the relative advantage of small cell size
The bigger the SA:V ratio the more efficient the diffusion for the cell, This is because the smaller the cell size and the larger the surface area the faster and more efficient diffusion will be for the cell.
Why in photosynthetic cells are chloroplasts found close to the cell membrane?
Because it would be the optimum position for the chloroplasts to absorb carbon dioxide & sunlight so it can photosynthesise and convert it to chemical energy.
Simple definition of passive transport
Transport when no energy is needed.
Simple definition of Hypertonic
There is a high concentration of solute, there is not a lot of water.
Simple definition of Osmoregulation
The control of water balance in the cell.
Simple definition of Plasmolysis
Water drains out of a plant cell and the membrane pulls away from the cell wall.
Simple definition of Isotonic
The solutions are equal in concentration
Simple definition of Diffusion
The movement of substances from a high concentration to a low concentration.
Simple definition of Facilitated diffusion
Transport of molecules by diffusion through special channels through the cell membrane (transporter proteins)
Simple definition of Semipermeable
A condition of the membrane where small substances freely pass in and out, but larger molecules cannot fit through the pores.
Simple definition of Turgid
Plant cells are full of water
Simple definition of Hypotonic
There is a low concentration of solute, there is a lot of water.
Simple definition of Osmosis
The movement of water from where there is a high concentration of water to where there is a low concentration of water.
Simple definition of Types of passive transport
Osmosis, diffusion and facilitated diffusion
Simple definition of Flaccid
Cells have lost water and become floppy
Simple definition of Lysis of cells
Cells become so full of water that they burst.
