Topic 2 - Transport Across Cell Membranes Flashcards
What makes up the membrane?
Phospholipids and proteins
What is the function of the cell membrane?
Controls the diffusion of substances of substances in and out of a cell
The membrane is selectively permeable, what does this mean?
That only relatively small molecules such as water, oxygen, amino acids and carbon dioxide can diffuse through
What is diffusion?
The movement of substances from a high concentration to a lower concentration
Which way do substances move?
Down a concentration gradient
Does diffusion need energy?
No, it does not therefore it is a passive process
What is the importance of diffusion to organisms?
It provides glucose and oxygen to aerobic respiration, amino acids for protein synthesis and carbon dioxide for photosynthesis in plant leaf cells
What is osmosis?
The diffusion of water from a high concentration to a lower water concentration across a selectively permeable membrane
Which way does water move on a concentration gradient?
It moves down the concentration gradient
What happens to an animal cell when it is put in a strong salt solution?
It will loose water and shrink
Why is it that when an animal cell is put in a strong salt solution it looses water and shrinks?
The salt solution outside the cell has a lower water concentration than the cell contents
What happens to animal cells when put in pure water?
Swell and burst
What happens when a plant cell is placed in pure water?
Water moves into the cell and it swells, becomes firm. It does not burst because it is protected by the cell wall. The plant cell becomes turgid
What happens when a plant cell is put in a strong salt solution?
Water moves out of a plant cell. The membrane and cytoplasm shrink away from the cell wall. The vacuole decreases in size. The plant cell becomes plasmolysed
What is transported in and out of a cell against a concentration gradient?
Molecules or ions
