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Biology
Transport and Storage Notes
The main transport system of mammals is its blood system called the circulatory system comprised of blood vessels and
the heart. Double circulatory system is when the blood travels through the heart twice on one complete journey around
the body.
The blood in the left-hand side of the heart has come from the lungs. It contains oxygen, which was picked up by the
capillaries surroundings the alveoli. It is called oxygenated blood. This oxygenated blood is then sent around the body.
Some of the oxygen taken up by the body cells, which need oxygen for respiration. When this happens the blood
becomes deoxygenated. The deoxygenated blood is brought back to the right-hand side of the heart, before going back
to the lungs again.
The Heart
(Draw in Notebook)
There are blood vessels on the outside of the heart which supplies oxygen and nutrients to it. These vessels are called
the coronary arteries. When the heart beats, the cardiac muscles contract and relax. When they contract, the heart
becomes smaller, squeezing blood out and this is called systole. When they relax, the heart becomes large, allowing the
blood to flow into the atria and ventricles, and this is called the diastole. A group of specialized muscle cells begins and
maintains the heart beat which is known as the sinoatrial node or pacemaker.
Blood Vessels
Function
Carry blood from the
Heart to the body
Wall Structure
Thick and strong;
Muscle and elastic
tissue
Lumen
Relatively narrow but
stretch and recoil with
heart beat
Purpose
Strength and elasticity
needed to withstand
pulsing of blood
Capillaries
Supply cells with O2/nutrients
And remove waste product
Very thin; only one
cell thick
Very narrow, small enough
for a red blood cell to pass
Thin walls needed to
exchange materials for
body tissue and cells
Veins
Return blood to the heart
From the body
Quite thin; far less
Muscle and elastic
Tissue to arteries
Wide and contains valves
Increase blood flow with
Wide lumen and valves
Prevent backflow
Arteries
Blood
Blood consists of cells floating in plasma. The liquid part of blood is called plasma. Floating in the plasma are cells. Most
of these are red blood cells. A much smaller number are white blood cells. There are also small fragments formed from
special cells in the bone marrow called platelets.
Lymph and Tissue Fluid
Capillaries leak because there are small gaps between the cells in the walls. Plasma and White Blood Cells can therefore
leak out from the blood. Red blood cells can’t leak out because they are too large and have a fixed biconcave shape (not
able to squeeze through small spaces). So plasma and white blood cells are continually leaking out of the blood
capillaries. The fluid formed in this way is called tissue fluid.
Tissue fluid is very important because it supplies cells with all their requirements such as oxygen, glucose, which diffuse
from the blood, through the tissue fluid into the cells. Waste products, such as a carbon dioxide, diffuse in the opposite
direction.
The tissue fluid is the immediate environment of every cell in your body. The plasma and white blood cells that leak out
of the blood capillaries must eventually be returned to the blood. There are lymphatic capillaries allow the fluid or
lymph to slowly drains back into them.
Storage in Mammals
Sometimes the food available for use in the cells are not immediately needed. Food is often stored as polysaccharides
(carbohydrates). In mammals, the polysaccharide is glycogen and in plants its starch.
Mammals store glycogen in the liver, and in muscle where both are centres of high metabolic activity. Glycogen is built
up of glucose, which is released for respiration as needed.
Transport in Plants
Plants have 2 transport systems- phloem and xylem. The xylem vessels carry water and minerals, while the phloem
tubes carry organic nutrients which the plant has made.
The Xylem
Xylem helps to support plants. A xylem vessel is like a long drainpipe, made of many hollow, dead cells, joined end to
end. The end walls of the cells have disappeared, so a long open tube is formed. The xylem vessels run from the roots of
the plant, right up through the stem and branch out into every leaf.
Xylem vessels contain no cytoplasm or nuclei. Their walls are made of cellulose and lignin.
The Phloem
The phloem tubes are made of many cells joined. However, their end walls have not completely broken down but
formed seive plates which have small holes in them. The cells are called seive tube elemets and they contain cytoplasm,
but no nucleus. They do not have lignin in their cell walls. Each seive tube has a companion cells which supply the seive
tube with some of their requirements.
Xylem vessels and phloem tubes are usually found close together. A group of xylem vessels and phloem tubes is called
the vascular bundle.
Transport of Water
Plants take in water from the soil, through their root hairs. The water is carried in the xylem vessels to all parts of the
plant. There are several different types of root system. Plants such as grasses have fibrous root systems (lateral or side
roots branching from them). A tap root is a single main root, again with smaller lateral roots growing for it. However, if
roots grow straight out of a stem, they are called adventitious roots.
Transpiration
The function of root hairs is to absorb water and minerals from the soil. Water goes into a root hair by osmosis and
mineral by active transport. The root hairs are on the edge of the root. The xylem vessels are in the centre and the water
must travel to it from the root hairs.
Water moves up the xylem vessel the same way that it moves up a straw. When you suck a on straw, you are reducing
the pressure at the top of the straw. The liquid at the bottom of the straw is at a higher pressure so it moves upwards.
This same difference in pressure causes water to move from the roots up the stem to the leaves.
Transpiration is the evaporation of water from a plant. Most of this evaporation takes place from the leave through
openings on the underside surface of the leaf called stomata. Water is constantly flowing through the xylem vessels
from the roots to the leaves where it evaporates. This process is known as transpiration stream.
Factors affecting Transpiration

Temperature: Hot days, water will evaporate more quickly from the
leaves.

Humidity: Humid days, water will evaporate more slowly .

Wind Speed: Windy days, water will evaporate more quickly.

Light Intensity: In bright sunlight, wall will evaporate more quickly because the plant opens its stomata for more
CO2 for photosynthesis.

Water Supply: drought- slows transpiration rate & rainy days- increases transpiration rate.
Transport of Food
Leaves make carbohydrates from photosynthesis. These sugars are transported in the phloem tubes. It is carried from
the leaves to whatever part of the plant that needs it. This is called translocation. The sap inside the phloem tubes
therefore contain a lot of sugar, particularly glucose.
Storage Organs in Plants
Some plants have modified underground stems such as rhizomes, stem tubers and corms.
Rhizomes are horizontal underground stems.
Stem Tubers are the swollen ends of slender rhizomes.
Corm is a short, swollen underground stem.
Roots can be modified as storage organs too. The specialised storage structures are root tubes and swollen tap roots.
Root tubers are swollen ends of roots. They can be distinguished from stem tubers since they do not have leaf scars,
scale leaves or buds. Tap roots are swollen roots for storage.
The products of photosynthesis are often stored temporarily in leaves before translocation to other parts of the plant.
Leaves are sometimes modified as food or water storage organs. Bulbs are condensed underground shoots and look like
a large bulb.