Transport Flashcards
what are the factors that affect the rate of movement of substances?
- Surface area to volume ratio
- temperature
- concentration gradient
- distance
How does the SURFACE AREA TO VOLUME RATIO affect the rate of movement of substances?
- as SA:V increases = rate of movement of substances INTO + OUT OF CELLS also increases
Because: there is a larger surface area where substances can move through (therefore increasing the rate of movement of the substance).
How does the TEMPERATURE affect the rate of movement of substances?
- as temperature increases = rate of movement of substances INTO + OUT OF CELLS also increases.
Because particles gain more KINETIC energy (therefore move faster) + increasing the rate of movement of the substance.
How does the DISTANCE affect the rate of movement of substances?
- as distance increases = the rate of movement of the particles decreases
Because larger distance substance has to travel = slower rate of movement of particles into + out of cell.
(makes rate of diffusion slower as particles have to travel a larger distance).
What are UNICELLULAR ORGANISMS?
Organisms composed of a single cell
Why can simple, unicellular organisms rely on diffusion for movement of substances in and out of the cell?
As they are composed of a single cell, they have a larger surface area in relation to their VOLUME therefore have a LARGER SA:V
With a large SA:V, unicellular organisms hava efficient rate of diffusion, allowing cell to RELY OF DIFFUSION TO TRANSPORT NECESSARY SUBSTANCES IN + OUT OF CELL.
What is a TRANSPORT SYSTEM?
means by which materials are carried to a medium to constantly supply cells through an exchange surface. (e.g; transport system in humans is blood)
Why do multicellular organisms need a transport system?
most multicellular organisms have small SA:V because they are large so as SIZE INCREASES, SA:V DECREASES.
- this is because they have more than one cell so have inefficient rate of diffusion.
- therefore rely on transport system to provide constant flow of substances that it needs such as OXYGEN + GLUCOSE.
What is the the role of PHLOEM?
Tube system that transports organic compounds (sucrose + amino acids) from sources to sinks via translocation.
What is a source?
where organic compounds are SYNTHESISED (photosynthetic tissue-leaves)
What are sinks?
where organic compunds are deliverd to for USE or STORAGE (fruits, roots + seeds)
In what direction is the transport in phloem?
both UP + DOWN via translocation
What is translocation?
movement of substances (food) from stems to growing tissues + storage tissues.
- active process (requires energy)
What are the cells that make up the phloem?
SIEVE TUBES + COMPANION CELLS
What are sieve tubes?
specialised for transport + have NO NUCLEUS.
- each tube has perforated end so its cytoplasm connects one cell to the next.
SUCROSE + AMINO ACIDS ARE TRANSLOCATED WITHIN LIVING CYTOPLASM OF THE TUBES.
