B3.1 Movement of Molecules into and Out of Cells NOT FINISHED Flashcards
What is osmosis?
The movement of water molecules across a partially permeable membrane from a region of high water concentration to a region of low water concentration
What is a partially permeable membrane?
A membrane with very small holes in it
What is osmosis a form of?
Diffusion
What is tissue fluid?
A solution mixed with water, oxygen and glucose dissolved in it - Tissue fluid surrounds the cells in the body
What happens when there is a difference in concentration of water in the tissue fluid and the cell?
If the water concentration in the tissue fluid is greater than the water in the cell, then water will move from the dilute tissue fluid to the concentrated cell via osmosis (and vice versa)
What is osmosis trying to achieve?
Equilibrium
When you exercise what do you lose in your sweat?
Ions and water
What happens if the balance between water and ions in the body is wrong?
It could result in the cells having too much or too little water in them - having the wrong amount of water can damage cells or mean they don’t work as well
Why do sports drink contain water, sugar and ions?
Because they replenish the water and ions you lose in sweat and replace the sugar used up by the muscles during exercise
How do you evaluate claims made about sports drinks? (4)
Ask yourself:
Is the claim from a scientific study, published in a reputable journal?
Was it written by a qualified person who is not connected with the sellers?
Was the sample of people asked/tested large enough?
Have there been other studies which found similar results?
What is active transport?
The movement of particles against a concentration gradient (low concentration to high concentration) using energy released from respiration
Give an example of where active transport occurs
In the digestive - when there is a low concentration of nutrients in the gut and a high concentration of nutrients in the blood, this is essential to stop us from starving
What does active transport need to work?
Energy from respiration
What does active transport allow cells to do?
Absorb ions from very dilute solutions
Why is there a constant movement of substances in the body?
Because cells need substances to work and also need waste substances removed
In life processes, what do substances have to move through?
An exchange surface
How are exchange surfaces adapted to maximise efficiency?
They are thin, so substances only have a short distance to diffuse, they have larges surface areas so lots of substances can diffuse at once, ES in animals have lots of blood vessels to get stuff in and out of the blood quickly and gas exchange surfaces in animals are usually ventilated - air moves in and out
How does the exchange of substances work in single-celled organisms?
Substances are directly exchanged with the environment across their outer surface
Why are specialised organ systems needed for exchanging materials in bigger, complex organisms?
Because where the substance is needed ends up being far away from exchange surfaces
What is the job of the lungs?
To transfer oxygen to the blood and remove carbon dioxide from the blood
Where does gas exchange take place in the lungs?
In little air sacs called alveoli
Why does oxygen diffuse into the alveoli and into the capillaries?
Because there is a greater concentration of oxygen in the air than in the alveoli, and from there, there is a greater concentration of oxygen in the alveoli than in the blood so oxygen diffuses into capillaries
Why does carbon dioxide diffuse into alveoli from the blood?
Because there is a greater concentration of carbon dioxide in the blood than in the alveoli
How does air enter and leave the alveoli?
Through small tubes called bronchioles
How are the alveoli adapted to maximise the diffusion of oxygen and carbon dioxide? (4)
They have a large surface area, a moist lining for dissolving gases, very thin walls and a good blood supply
Where and how are glucose and amino acids absorbed into the bloodstream?
The small intestine - either by diffusion or active transport
How is the absorption of nutrients assisted in the small intestine?
The inside of the small intestine is covered in millions of tiny little projections called villi
How do the villi aid absorption in the small intestine? (3)
They increase the surface area of the small intestine (so food is absorbed quicker), they have a very good blood supply to assist quick absorption and have a single layer of surface cells
