Membranes Flashcards
What is the structure of a phospholipid?
Glycerol, two fatty acids and a phosphate group
What is the width of the cell membrane?
7nm
What’s the difference between intrinsic and extrinsic proteins?
Intrinsic proteins pass right through the membrane such as carrier and channel proteins, extrinsic do not pass the entire way through, or are peripheral (only on the outside)
What is the glycocalyx?
The layer above the membrane consisting of carbohydrate chains from glycoproteins
What does ?fluid mosaic? model mean?
The model is called fluid because the phospholipid and protein molecules move around each other. The model is called a mosaic because proteins embedded between the phospholipids vary in shape, size and patter
What is the function of glycoproteins and glycolipids in the cell membrane?
Cell to cell communication and recognition
What is the function of cholesterol in the cell membrane?
To maintain fluidity
How do lipid soluble substances pass through the cell membrane?
They can dissolve in the fatty acid tails and move through the membrane by simple diffusion
How do ions pass throught the cell membrane?
They must pass through a channel protein by facilitated diffusion
What is active transport?
Movement from an area of low to high concentration, against a concentration gradient. This is done through a carrier protein and requires ATP
Which transport protein is used for active transport?
A carrier protein
What is a channel protein for water called?
An aquaporin
What is the specific term for bulk transport of a solid into a cell?
Phagocytosis
What is the term for bulk transport of a liquid into a cell?
Pinocytosis
What is the term for bulk transport out of a cell?
Exocytosis
Why do endocytosis and exocytosis require ATP?
ATP is required to provide energy to move the cell membrane
What is osmosis?
Water molecules move down a water potential gradient through a selectively permeable membrane.
What is the water potential of pure water?
0 Kpa, the highest water potential can be
In a plant cell the water potential=
The solute potential (?s) which is the effect of solutes lowering the water potential of the cell sap (negative value) and ?p which is the opposite pressure provided by the cell wall and is usually positive (?cell = ?s+ ?p).
Hypotonic means
A solution with a higher water potential than a cell
Hypertonic means
A solution with a lower water potential than a cell
Isotonic means
A solution with the same water potential as a cell
When in hypertonic solution, what will happen to a plant and animal cell and why?
Water will move out of the cell, down a water potential gradient by osmosis. The plant cell is plasmolysed or flaccid, the animal cell is crenated
When in hypotonic solution, what will happen to a plant and animal cell and why?
Water will move into the cell, down a water potential gradient by osmosis. The plant cell is turgid, the animal cell will swell and lyse (burst)
When a plant cell is in incipient plasmolysis, what is happening to water movement?
There is no net water movement into or out of the cell
How would you recognise a plant tissue in incipient plasmolysis?
50% of cells are plasmolysed, 50% are turgid
How would you recognise a plant cell in incipient plasmolysis?
The cell membrane is just beginning to move away from the cell wall
Why would cyanide stop active transport?
Because it is a non competitive respiratory inhibitor, which would prevent production of ATP. ATP is required to provide energy for active transport
What does increasing temperature do to the cell membrane?
As temperature increases the membrane becomes more fluid, and slightly more permeable. When the temperature increases too much proteins will denature and lost their shape, creating pores that make the membrane even more permeable.
