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TRANSPORT SYSTEMS IN ORGANISMS, HUMANS, PLANTS, Why do we need transport…
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HUMANS
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Circulatory system
consists of the heart, blood and blood vessels
BLOOD VESSELS
Veins > carries blood to the heart
Arteries > carries blood away from heart
Capillaries > very thin (1 cell thick), connects arteries to veins > also quick diffusion of nutrients (glucose) and O2 from blood to tissue cells > waste substance (CO2) move from tissue cells to blood
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Blood is continuously circulating around the body. Nutrients and oxygen are quickly transported to all parts of the body so the body produce the energy needed in a short period of time. Blood is an essential medium of the human transport system. Blood is a fluid tissue or fluid tissue with cells, consisting of platelets, plasma (mainly water), red blood cell (RBC) and white blood cell (WBC) Blood also protects us from disease-causing germs. When we go to low oxygen places, our body produce more RBC to transport more oxygen.
Plasma is solvent for many substances that it carries along in the bloodstream which are transported from one part of the body to another. Plasma transports digested food from small intestine to other parts of the body, removes CO2 and waste substances produced in body cells and transports other substances such as hormones.
RBC are in biconcave shape so there is a larger surface area which allows RBC to take in/release O2 at a quicker rate. RBC transports O2 to the lungs to other parts of the body. Lack of RBC weakes a person causing the person to faint.
PLANTS
Transport tissues
Strands in plants are vascular bundles which are arranged in a ring withing the stem consists of two tissues, xylem and phloem. (long tubes/vessels that pass from roots to leaves)
Xylem - transport water/mineral salts from roots to leaves
Phloem - transport food (sugar) produced by leaves to all parts of plant.
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Diffusion
Diffusion is the movement of molecules from a region of higher concentration to lower concentration across a partially permeable membrane.
For example:
Solution A have more sucrose molecules so more sucrose molecules move from solution A to B compared to solution B to A.
Solution B have a higher water potential so more water molecules moves from solution B to A compared to solution A to B.
There is a net (overall) in movement of molecules.
In the end, both solutions will have equal amount of sucrose and water molecules.
Osmosis
Osmosis is the movement of water molecules from a region of higher water potential to a lower water potential through a partially permeable membrane.
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Another example of diffusion is the exchange of gases in a leaf during photosynthesis
Concentration of CO2 is lower than the outside of the leaf so CO2 diffuses in. The concentration of O2 is higher than outside of the leaf so O2 diffuses out. **Cells surrounding the stomata controls the size of the stoma so the cells are able to control the amount of O2 and CO2 in the leaf.