B3.1 Movement of molecules in and out of cells Flashcards
How do dissolved substances move?
By diffusion and active transport
How does water move across boundaries?
Osmosis
What is osmosis?
The diffusion of water from a dilute to a more concentrated solution through a partially permeable membrane that allows passage of water molecules
What causes water to move into or out of a cell?
The different concentrations of the solutions inside and outside a cell
What do most soft drinks contain?
Water, sugar and ions
What do sports drinks contain?
Sugars to replace the sugar used in energy release during the activity. They also contain water and ions to replace what is lost in sweat
What happens if the water and ions are not replaced?
The balance of the body is disturbed and the cells do not work as efficiently
How are some substances sometimes absorbed?
Against a concentration gradient
What is the name for the method of absorption which moves against the concentration gradient?
Active transport
What does active transport require?
Energy from repsiration
What does active transport allow cells to do?
Absorb ions from very dilute solutions
How are many organ systems specialised?
For exchanging materials
How is the effectiveness of exchange area increased?
Having a large surface area, being thin (short diffusion path), (in animals) having an efficient blood supply and (in animals) being gaseous
What are gas and solute exchange surfaces adapted to do?
Maximise effectiveness
What does the size and complexity of an organism increase?
The difficulty of exchanging materials
How is the surface area of the lungs increased in humans?
By the alveoli
How is the surface area of the small intestine increased in humans?
By the villi
What do the villi provide?
A large surface area with an extensive network of capillaries to absorb the products of digestion by diffusion and active transport
Where are the lungs?
In the upper part of the body (thorax)
What are the lungs protected by?
The ribcage
What separates the lungs from the lower part of the body (abdomen)?
The diaphragm
The breathing system takes air into and out of the body so that…
Oxygen from the air can diffuse into the bloodstream and carbon dioxide can diffuse out of the bloodstream into the air
To make air move into the lungs the ribcage moves…
Out and up and the diaphragm becomes flatter
To make air move out of the lungs the ribcage moves…
Inwards and down and the diaphragm contracts
What is the movement of air in and out of the lungs called?
Ventilation
In plants, carbon dioxide enters leaves by…
Diffusion
In plants, most of the water and mineral ions are…
Absorbed by roots
How is the surface area of roots increased?
By root hairs
How is the surface area of leaves increased?
By the flattened shape and internal air spaces
What do stomata do?
Obtain carbon dioxide from the atmosphere and remove oxygen produced in photosynthesis
How do plants mainly lose water vapour?
From their leaves, most water loss takes place in the stomata
Evaporation is more rapid in…
Hot, dry and windy conditions
If plants lose water faster than it is replaced by the roots…
The stomata can close to prevent wilting
What is the size of stomata controlled by?
Guard cells which surrounds them
