Movement of Substances Into & Out of Cells Flashcards

All 17 cards in this deck

What is diffusion?

The net movement of particles from an area of high concentration to an area of low concentration, down a concentration gradient.
It is passive — no energy is needed.

Name two gases that move into or out of cells by diffusion.

Oxygen and carbon dioxide.
e.g. carbon dioxide diffuses from the blood into an alveolus.

True or false? Oxygen moves into and out of cells by osmosis.

False. Oxygen moves by diffusion — osmosis is the movement of water only.

What is osmosis?

The movement of water from a dilute solution (high water concentration) to a concentrated solution (low water concentration) through a partially permeable membrane.

What happens to a plant cell placed in a concentrated salt solution?

Water moves out of the cell by osmosis, so the cytoplasm shrinks away from the cell wall (the cell becomes plasmolysed).

True or false? A red blood cell placed in a concentrated sugar solution will swell.

False. Water moves out of the cell by osmosis, so the cell shrinks.

How do guard cells make the stomata open?

The guard cells take in water by osmosis, become turgid and swell, changing shape so the stoma opens.

What is active transport?

The movement of a substance against a concentration gradient (from low to high concentration), using energy.

Where does the energy used in active transport come from?

Respiration, which takes place in the mitochondria.

Give one example of a substance taken into a plant by active transport.

Mineral ions, absorbed from the soil into root hair cells.

What is measured in the potato osmosis core practical?

The mass of each potato chip before and after it is left in the solution (blotted dry each time), so the percentage change in mass can be worked out.

Name three variables that must be controlled in the potato osmosis investigation.

Same temperature; same volume of solution; same size/mass of potato chip.
(Also same time left and same method of blotting dry.)

In an osmosis investigation, what does the solution concentration at which there is no change in mass tell you?

The concentration inside the cells is the same as outside — the isotonic point.

What is the equation for the percentage change in mass in an osmosis investigation?

percentage change in mass = (final mass − initial mass) ÷ initial mass × 100
A negative answer means mass was lost.

True or false? Diffusion can only take place across a cell membrane.

False. Diffusion happens in any gas or liquid where particles are free to move; it is osmosis that must take place through a partially permeable membrane.

What is a partially permeable membrane?

A membrane that lets small molecules such as water pass through, but stops larger molecules such as starch or proteins.

In the potato osmosis core practical, why is the percentage change in mass worked out instead of just the change in mass?

The potato pieces may not start with the same mass, so a percentage lets their results be compared fairly.