Transport Accross Cell Membranes Flashcards
What are cell membranes made of?
Phospholipids and protein
What is the function if a cell membrane ?
Controls the diffusion of substances in and out of the cell
Describe a cell membrane.
Selectively permeable which means that only relatively small molecules such as water, oxygen, amino acids and carbon dioxide can diffuse through
What is diffusion ?
Movement of substances from a high concentration to a low concentration
How do substances move ?
Down the concentration gradient
What kind of process of diffusion and why?
Passive as it doesn’t require energy and moves with the concentration gradient
What is diffusion important ?
To organisms it provides glucose and oxygen for aerobic respiration, amino acids for protein synthesis and carbon dioxide for photosynthesis in plant leaf cell
What is osmosis?
Diffusion of water for a high concentration to a low concentration
How does water move?
Down the concentration gradient
What would happen to an animal cell in these scenarios ?
Pure water
A small salt solution
Strong salt solution
Pure water : cell bursts
Small slat solution : normal
String salt solution : loses water and shrinks
Describe a plant cell in these scenarios
Pure water
Small salt solution
Strong salt solution
Pure water: water moves in and causes it to be turgid. It swells but does not burst as the cell wall is protecting it.
Small salt solution: normal
Strong salt solution: water moves out of the plant cell . The membrane and cytoplasm shrink away from the cell wall. Vacuole shrinks and the cell becomes plasmolysed and flaccid
How do ions and molecules move?
Against the concentration gradient. Move from a low to a high concentration, this is done by proteins within the membrane and the process is called active transport as it requires energy
What does the term hypotonic mean?
A solution will always loose water
What does the term hypertonic mean?
A solution will always gain water
What does the term isotonic mean?
A solution will neither gain nor loose water
