TRANSPORT – Life function by which organisms ABSORB and DISTRIBUTE
materials needed for life.
Absorption:
The process by which cells move dissolved materials across the cell membrane.
Ex) gases, digestive end products, salts ………..
Plasma (Cell) Membrane - structure found in all cells.
Role in Homeostasis –the cell membrane selectively regulates the passage
of materials into and out of cells.
Structure – Fluid Mosaic Model – The cell membrane is a Bilipid with
Proteins embedded in it. Spaces found between the lipids allow materials
small enough to pass through the membrane. Other materials that are
larger can be moved across by the proteins.
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*materials that are small enough to pass through the bilipid layer are:
oxygen, carbon dioxide, water, amino acids, monosaccharides, fatty acids,
glycerol, salts.
* larger materials must first be “recognized” by the proteins in the cell
membrane and then brought into or out of the cell. REMEMBER – proteins
are able to do this by recognizing the SHAPE of a material.
Passive Transport- the movement of materials across a semi-permeable
membrane from an area of high concentration to an are of low
concentration. This process requires NO ENERGY!
DIFFUSION is an example of passive transport. It can happen anywhere
there is an uneven concentration of molecules, with or without a cell
membrane between them.
This picture shows diffusion of molecules (without a membrane present):
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Below is a representation of diffusion of molecules across a membrane:
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NOTICE that with each case diffusion stops when distribution of
molecules is even! *
OSMOSIS is the other example of passive transport. It is the diffusion of
water across a selectively permeable membrane from an area of high
concentration of WATER molecules to an area of lower concentration of WATER
molecules.
Active Transport – The movement of molecules across the cell membrane
with the USE OF ENERGY. There are three ways this happens:
1.
Movement of molecules against the concentration gradient.
This is like walking up a steep hill; it requires lots of energy.
The proteins embedded in the cell membrane do this work.
2.
Pinocytosis – Molecules that are too large to normally get into
the cell are brought in by the cell membrane forming a vacuole
and “sucking in “ the molecule.
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3.
Phagocytosis - The cell membrane moves and ENGULFS food
particles with pseudopods.
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Circulation :
Movement of materials around the cell – Cyclosis
or the organism. Movement through multicellular organisms is aided by Vascular
Tissue – “tubes” like veins, arteries, xylem, phloem
Intracellular Transport – Also known as CYCLOSIS - Movement of materials
throughout the cytoplasm by streaming of the cytoplasm. The mechanisms by
which this happens are still not explained.
Intercellular Transport – Multicellular organisms must have a way to move
materials from cell to cell over large distances. VASCULAR TISSUE is used to
do this:
PLANTS use vascular tissue called xylem and phloem.
ANIMALS use vascular tissue called arteries and veins.
PLANT TRANSPORT
Xylem and Phloem are Vascular Tissue for plants.
Xylem carries water and minerals in an upward direction – ONLY.
Phloem carries water and glucose (food) upward and downward.
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Xylem and Phloem run through the plant from the roots to the stem/trunk and
become the vein of the leaf.
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Plants use three mechanisms to move water, minerals and food great distances.
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Osmosis of water into the billions of cells that make up the tiny root
hairs in plants create an Osmotic Pressure that “pushes” water up the
xylem and phloem
Water vapor evaporating from the billions of stomates in the leaves of
plants – this is called Transpiration – draws water up the xylem and
phloem (like sipping through a straw).
Capillary Action – movement of water through tiny spaces without
using energy moves water upward.
ANIMAL TRANSPORT –
Arteries and Veins are Vascular Tissue for Animals
Arteries carry blood away from the heart.
Veins carry blood back toward the heart.
*Animal Vascular tissue will be studied in more depth while
learning about Human Transport*