BIOLOGY3

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3.1 movement of molecules in and out of cells

DIFFUSION - Movement of particles from a high concentration to low . E.g. oxygen diffuses across the alveoli into the capilliaries surrounding it. 

OSMOSIS - Movement of water from a high water concentration to a low water concentration, THROUGH A PARTIALLY PERMEABLE MEMBRANE. E.g water moves from blood stream into cells that have a low water concentration. 

ACTIVE TRANSPORT - Movement of particles AGAINST THE CONCENTRATION GRADIENT (low to high) with the use of a carrier protein. This requires energy. Plant roots use active transport to absorb mineral ions from the soil - even though there are lower concentrations of minerals in the soil than there are within the root hair cell, therefore it goes against the concentration gradient 

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3.2 transport systems in animals and plants

The circulatory system:

the heart - which is the muscular pump that keeps the blood moving around the body

the blood - which carries the substances around the body

the arteries - which carry blood away from the heart

the veins - which return blood to the heart

the capillaries - which are tiny blood vessels that are close to the body’s cells where exchanges can happen

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Transport systems and processes in plants

Plants have two transport systems to move food, water and minerals through their roots, stems and leaves. These systems use tubes called xylem and phloem, and together they are known as vascular bundlesXylem vessels are involved in the movement of water through a plant - from its roots to its leaves via the stem:

Water is absorbed from the soil through root hair cells.

Water moves by osmosis from root cell to root cell until it reaches the xylem.

It is transported through the xylem vessels up the stem to the leaves.

It evaporates from the leaves (transpiration).

The xylem tubes are made from dead xylem cells which have the cell walls removed at the end of the cells, forming tubes through which the water and dissolved mineral ions can flow. The rest of the xylem cell has a thick, reinforced cell wall which provides strength.

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Phloem

Phloem vessels are involved in translocation. Dissolved sugars, produced during photosynthesis, and other soluble food molecules are moved from the leaves to growing tissues (the tips of the roots and shoots) and storage tissues (the roots).

In contrast to xylem, phloem consists of columns of living cells. The cell walls of these cells do not completely break down, but instead form small holes at the ends of the cell. The ends of the cell are referred to as sieve plates. The connection of phloem cells effectively forms a tube which allows dissolved sugars to be transported.

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EXTRA ABOUT PLANTS

Transpiration: how water moves up the plant against gravity in the xylem ---- e.g Water on the surface of palisade cells evaporate and then diffuse out of the leaf.

Factors that effect transpiration:

The more light, the more transpiration, this is because the stomato open more to allow more carbon dioxide in for photosynthesis

Temperature - the hotter, the more evaporation, which in turn means more transpiration.

Wind - water vapour is removed quickly by the wind, which quickens diffusion of water out of the plant leaf

Humidity - the more humid the area is, the less transpiration can occur. As diffusion is from high-low concentration and if the air is full of water vapour it cannot diffuse out as well.

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3.3 Homeostasis

Maintaing a constant internal environment! - Through the nervous system and hormones.

Homeostasis maintains :

Body temperature as enzymes in the body require a temperature of around 37degrees to function correctly and more efficiently.

Blood Sugar Level production of insulin from the pancreas and glucose made in respiration. Insulin controls sugar levels.

Water Content protects cells by ensuring that too much water doesn't enter or leave the cells. Controlled by exhaling water vapour, sweating and urine.

Ions important ions include sodium, potassium, hydrogen and phosphate. These are controlled through our urine and the amount of water we drink. We also lose some, like sodium ions, through our faeces and our sweat. Too many ions can cause cells to burst!

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DIAGRAM

Flow chart showing how the body returns to normal temperature of 37 degrees centigrade. Following an increase in temperature through sweating following a decrease in temperature through shivering.

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