B4 Cell Transport Mechanisms Flashcards
What 4 things does the cell membrane consist of?
Proteins, glycoproteins, phospholipids, carbohydrates.
Explain why the model for membrane structure is known as the fluid mosaic model.
(Fluid) The phospholipds move freely. (Mosaic) The proteins are distributed unevenly throughout the membrane. (Model) The agreed structure is based on experimental/chemical evidence.
Which part of a phospholipid is hydrophobic?
The fatty acid chains that make up the tail.
What does cholesterol do in the cell membrane?
Decreases permeability and increases the stability of the membrane.
Which part of a phospholipid is hydrophilic?
The head.
What are glycoproteins made up of?
Carbohydrate and protein.
What is the name of the special types of channel proteins that are specific to water?
Aquaporins
Name part A
Intrinsic protein (eg channel protein)
Name part B
Phospholipid
Name part C
Glycoprotein
Name part D
(Hydrophilic) Polar head
Name part E
Extrinsic protein
Name part F
Phospholipid bilayer
Name part G
Glycolipid
Name part H
Carbohydrate chain
Name part I
Cholesterol
Define “Diffusion”
The net movement of molecules from an area of higher concentration to a lower concentration.
How does increasing the temperature affect the rate of diffusion?
A higher temperature gives the molecules more kinetic energy, therefore a faster rate of diffusion.
How does increasing the surface area affect the rate of diffusion?
A larger surface area provides more “space” for the molecules to pass through, therefore it is faster.
How does increasing the concentration gradient affect the rate of diffusion?
As the concentration gradient increases, the rate of diffusion increases.
Define “Osmosis”
Osmosis is the net movement of water molecules from a region of low solute (higher water concentration) to a region of high solute (lower water concentration) across a partially permeable membrane.
Define “Active transport”
Movement of molecules from an area of lower concentration to an area of higher concentration. This requires energy/ATP.
Name the cell transport mechanisms that are “active”
Active transport. Bulk transport (exocyctosis and endocytosis)
Name the cell transport mechanisms that are “passive”
Simple diffusion, facilitated diffusion, osmosis.
How does glucose move into cells? Why is it this mechanism?
Facilitated diffusion. Glucose is a large, polar molecule.
How does oxygen move into cells? Why is it this mechanism?
Simple diffusion. Oxygen is a small, non-polar molecule that can dissolve in the bilayer.
How do lipid soluble molecules move into cells? Why is it this mechanism?
Simple diffusion. The molecule dissolves in the fatty acid tails.
How do potassium ions move into cells? Why is it this mechanism?
Facilitated diffusion. It’s a small, charged ion.
As an organism increases in size, what happens to the surface area to volume ratio?
The surface area to volume ratio decreases.
Calculate the surface area to volume ratio of a cube that has a side length of 5cm.
1.2:1
Explain why the cell membrane is selectively/partially permeable.
The carrier proteins are specific to a substance.
Define “Facilitated diffusion”.
Facilitated diffusion is a passive process where molecules move down a concentration gradient (from a higher to lower concentration) using a carrier/channel protein.
What happens to an animal cell if it is placed in a solution with a lower solute concentration?
Water moves into the animal cell, causing it to swell. The cell could burst (lysis) and its contents would be lost.
What happens to an animal cell if it is placed in a solution with a higher solute concentration?
Water moves out of the cell, resulting in the cell shrivelling. Mass would be lost.
What happens to an animal cell if it is placed in an isotonic solution?
The is no net movement of water into or out of the cell. There would be no change in mass.
What happens to a plant cell if it is placed in a solution with a lower solute concentration?
Water will move into the cell, and it would swell. The cellulose cell wall prevents lysis.
What happens to a plant cell if it is placed in a solution with a higher solute concentration?
Water would move out of the cell. The plant cell membrane would pull away from the cell wall (plasmolysed)
How are exchange surfaces in animal adapted to maximise effectiveness?
Thin membrane - so a short diffusion distance. Large surface area - so a lot of a substance can diffuse at once. Good blood supply - to maintain the concentration gradient (by moving materials in and out of the blood quickly)
During exocytosis a cell moves large quantities of molecules ………. the cell.
out of
During endocytosis a cell moves large quantities of molecules ………. the cell.
into
