Transport In and Out Of Cells Flashcards
What is diffusion?
How come this happens?
Diffusion is the net novement of particles from an area of high concentration to an area of low concentration until they are evenly spread out
This is because particles move randomly and are spread out
What are 3 examples of diffusion in living organisms?
Oxygen and carbon dioxide diffuse during gas exchange in lungs, gills and plant leaves
Urea diffuses from cells into the blood plasma for excretion by the kidney
Digested food molecules from the small intestine diffuse into the blood
Name 3 factors that affect the rate of diffusion
a. The difference in concentration e.g. the concentration gradient
b. The temperature
c. The surface area of the membrane
Explain the difference between single-celled organisms, multicellular organisms and their surface area to volume ratio.
Single-celled organisms - large surface area to volume ratio
Multicellular organisms - smaller surface area to volume ratio
Why do single-celled organisms have large surface are to volume ratioes?
This allows enough molecules to diffuse into and out of the cell to meet the needs of the organisms
Why is it okay that multicelled organisms have smaller surface area to volume ratioes?
Because the surfaces and organ systems are specialized for exchanging materials
How are the small intestine and lungs in mammals; gills in fish; roots and leaves in plants adapted to exchange materials?
- large surface area
- thin surface so molecules only have to diffuse a short distance
- moist surfaces so substances can dissolve and diffuse across cell membranes faster
In animals - rich blood supply maintains the concentration gradient
- ventilation ocurrs to speed up the gaseous exchange
Name some organisms adapted to exchange materials?
Mammals - small intestine - lungs Fish - gills Plants - roots - leaves
Water may move across cell membranes by …
Water may move across cell membranes by …
osmosis
Many substances move into and out of cells, across the cell membranes, by …
Many substances move into and out of cells, across the cell membranes, by …
diffusion
What is osmosis?
It is the diffusion of water from a dilute solution to a concentrated solution through a partially permeable membrane
What does active transport do?
It moves substances against a concentration gradient, from an area of low concentration to high concentration
It requires energy from respiration
What does active transport require?
It requires energy from respiration
What does active transport allow?
It allows …
- mineral ions to be absorbed into plant root hairs from very dilute solutions in the soil
- sugar molecules to be absorbed (from lower concentrations) in the gut, into the blood (has a higher concentration)
If the potato cylinders don’t gain or lose weight, what does this mean?
That the sugar or salt solution must be the same concentration as the potato tissue
