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.
What are companion cells?
- transport of substances in phloem requires energy.
- ONE or MORE companion cells ATTACHED to each sieve tube.
- provides the energy.
A sieve tube is completely dependent on companion cell.
What is the role of XYLEM?
- one of the transport systems in plants
Xylem tubes transport water + mineral salts from roots up the shoots to the leaves in transpiration stream (more water drawn up the roots) - Water is then lost from leaves via transpiration
Of what are the Xylem walls made of?
They have thick walls stiffened with lignin
In what direction is the transport in Xylem?
One way only (up)
What is transpiration?
Loss of water vapour from plan leaves by evaporation of water at the surfaces of the mesophyll cells followed by diffusion of water vapour through the stomata.
Give three examples of unicellular organisms
bacteria
fungi
yeast
How does the CONCENTRATION GRADIENT affect the rate of movement of substances?
as concentration gradient increases = rate of movement of particles increases.
Because: stronger concentration gradient is present therefore increasing rate of movement of substances.
