Paper 1: Topic 1 Cell Biology - Transport in cells (IV form) Flashcards
Give 3 examples of molecules that diffuse
Some of the substances transported in and out of cells by diffusion are:
oxygen and carbon dioxide in gas exchange
urea from cells into the blood plasma for excretion in the kidney
How are the lungs in mammals adapted for exchanging materials?
Alveoli increase the surface area
The alveoli wall is only one cell thick (reduces the diffusion distance)
The lining of the alveoli is moist (to increase the diffusion of oxygen and carbon dioxide across the membrane)
Alveoli are covered in capillaries to ensure gases diffuse in and out of the blood efficiently
Why do plants need a supply of potassium ions?
To produce some enzymes and fruits
What is a hypotonic solution?
A solution with a lower concentration of solutes dissolved in it
Hence it has a higher water potential
Define the term osmosis
The movement (diffusion) of water molecules DOWN a WATER POTENTIAL GRADIENT across a partially permeable membrane from an area of higher** water potential to an area of low_er_** water potential
Why can single-celled organisms obtain their nutrients and remove their wastes by diffusion?
They have a relatively large surface area to volume ratio.
This allows sufficient transport of molecules into and out of the cell to meet the needs of the organism
What happens to plant cells that are placed into a concentrated solution?
Water moves out of the cell
Down the water potential gradient
By osmosis
The cell decreases in size and mass as it loses water
The vacuole shrinks
The cell will eventually become plasmolysed
What happens to plant cells that are placed into a dilute solution?
Water moves into the cell
Down the water potential gradient
By osmosis
The cell increases in size and mass as it gains water
The vacuole enlarges as water enters the vacuole
The cell will eventually become turgid
Give an example of active transport in plants
The absorption of mineral ions from the soil by root hair cells
Mineral ions are in a very dilute solution in the soil and are moved into the concentrated solution of the cell vacuole
What happens to red blood cells (or other animal cells) that are placed into pure water or a dilute solution?
Water moves into the cell
Down the water potential gradient
By osmosis
The cell increases in size and mass as it gains water
The cell will eventually rupture (burst)
They are described as being cytolysed (or if they are a red blood cell they are described as being haemolysed)
What is meant by the term ‘haemolysis’
The rupturing of a red blood cell (erythrocyte) as a result of water moving into the cell by osmosis
Rupturing of an animal cell (which is not a red blood cell) is called cytolysis
How are leaves in plants adapted for exchanging materials?
Leaves are broad, and thin flat (to increase the surface area)
Leaves are have many stomata on the underside of the leaf (to allow gas exchange to occur by diffusion)
How do you calculate the volume of a cube?
volume = height x width x depth
remember to include the units e.g mm3 or cm3
Is active transport an active or passive process? Explain your answer.
Active
It requires an input of ATP which is produced during respiration
ATP is needed to change the shape of the carrier protein to move the molecule against the concentration gradient
Give 2 ways in which diffusion and osmosis are different
- Diffusion applies to gases and small molecules, osmosis ONLY applies to water molecules
- Diffusion uses a concentration gradient, osmosis uses a water potential gradient
- Diffusion occurs until the moelcules are in equilibrium, osmosis occurs until the water potentials are equal
Give 3 ways diffusion and osmosis are different from active transport
Diffusion and osmosis are passive processes, active transport is an active process
Diffusion and osmosis move molecules down a gradient, active transport moves molecules against a gradient
Diffusion and osmosis only use kinetic energy, active transport requires an input of energy (ATP)
Diffusion and osmosis do not require protein carriers in the membrane, active transport does
What happens to red blood cells (or other animal cells) that are placed into pure water or a dilute solution?
Water moves into the cell
Down the water potential gradient
By osmosis
The cytoplasm increases in volume and mass as it gains water
The cytoplasm will push against the cell surface membrane
The cell ruptures and becomes haemolysed
Give 3 examples of molecules that can diffuse across cell membranes
Carbon dioxide
Oxygen
Carbon monoxide
Urea
How are gills in fish adapted for exchanging materials?
Gills have many gill filaments (to increase the surface area)
Gills are thin (to reduce the diffusion distance)
Gills have a good blood supply i.e. many blood vessels in them (to maintain a high concentration gradient)
Water continually runs over the surface of the gills (to maintain a high concentration gradient)
Label the diagram
