Transport across the cell membrane Flashcards
What is the cell membrane made of?
Phospholipids (fats) and proteins
How can the cell membrane be described and why?
Fluid because the double layer of phospholipids is constantly moving
How is the membrane structure referred to?
Fluid Mosaic Model
Where are the proteins located?
Within the phospholipid bilayer
What are the functions of the proteins?
- receptors for chemicals such as hormones or antibodies
- Carrier proteins for active transport
- Create pores in the membrane for passive transport
Why is the membrane selectively permeable?
It allows small molecules like water and oxygen to freely move about, slightly larger ones like amino acids to move slowly through it and large molecules like proteins and starch are unable to pass through
What are examples of passive methods of transport across the cell membrane?
Diffusion and Osmosis
What is diffusion?
Diffusion is the movement of molecules or ions from a region of higher concentration to a region of lower concentration, through a selectively permeable membrane. Down a concentration gradient
What is the purpose of diffusion?
It allows substances to move within a cell from one area to another, as well as allowing molecules to enter and leave a cell
When does diffusion stop?
Diffusion continues until the concentration is even throughout
Why is diffusion important for organism?
Oxygen and Glucose enter cells by diffusion for aerobic respiration
What is osmosis?
Osmosis is the movement of water molecules from a region of high water concentration to a region of lower water concentration through a selectively a permeable membrane. Down a concentration gradient
What is active transport?
The movement of molecules or ions across a cell membrane against a concentration gradient
How are the molecules or ions moved in active transport?
By carrier proteins
What provides the energy needed by active transport?
ATP
If aerobic respiration is limited, how will that affect active transport?
It will limit the rate of active transport
What happens if a plant cell is placed in a solution with a greater concentration than within the cell?
Water passes into the cell causing the vacuole to swell, Because the call wall is fairly frigid and strong enough to resist the pressure, the cell does not burst and is described as turgid
What happens if a plant cell is placed in a solution with equal concentration to the within the cell?
No net gain or lost of water. The cell will remain unchanged
What happens if a plant cell is placed in a solution with a lower concentration than within the cell?
Water passes out the cell to it’s surrounding, causing the vacuole to shrink and pulls the cytoplasm inwards. A gap develops between the membrane and the cell wall. The cell is described as being plasmolysed
Why does osmosis effect plant and animal cells differently?
Plant cells have cell wall and a vacuole. Animal cells do not.
What happens if an animal cell is placed in a solution with equal concentration to the within the cell?
No net gain or lost. The cell will remain unchanged
What happens if an animal cell is placed in a solution with a higher water concentration than within the cell?
Water passes into the cell from it’s surrounding, causing the cell to swell up. As there is no cell wall it will eventually burst
What happens if an animal cell is placed in a solution with a lower water concentration than within the cell?
Water passes out the cell to it’s surroundings, causing the cell to shrink and shrivel up
