Biology Unit 3

The diffusion of water molecules from high to low concentration through a partially permeable membrane.

·         hypertonic= high glucose (solvent) concentration

·         hypotonic= high water (solute) concentration

·         isotonic= equal concentration of solvent and solute

Animal cells-

·         hypertonic= water leaves the cell as there is a low concentration of water in solution, cell becomes shrivelled

·         hypotonic= low concentration of water inside cell/high concentration of water in solution, water enters and cell undergoes lysis (its bursts)

·         isotonic= equal amount of water goes in and out as similar concentrations

Plant cells-

·         hypertonic- water moves outside of cell so it becomes plasmalysed (shrivelled in plant world)

·         hypotonic- water enters cell yet it does not undergo lysis due to support of the cell wall, the plant cell becomes turgid

·         isotonic- loses a small amount of water but mainly remains the same

Active Transport-

Active transport allows particles to move from an area of low concentration to high, against the concentration gradient. The process relies on ATP energy from respiration, carries proteins and partially permeable membranes.

Adaptations allowing AT-

·         Many mitochondria to produce ATP.

·         many ribosomes to make carrier proteins

The solute will enter the V-shaped carrier protein which uses the ATP energy to undergo conformational change (where the V shape flips so its carries solute from the outside of the cells to the inside).

Exchange of materials in plants-

Water moves UP the xylem because...

·         there is a high hydrostatic root pressure

·         water molecules show cohesion with each other

·         there are no breaks in the xylem so the water molecules adhere to the xylem walls

Phloem tubes transport water AND nutrients UP and DOWN the plant.

To measure the rate of transpiration (loss of water) you can use a potometer and measure the distance travelled by the meniscus.

The circulatory system-

It’s a double circulatory system; the pulmonary circuit takes deoxygenated blood the lungs where its picks up oxygen and goes back to the heart, and the systemic circuit which takes oxygenated blood to body cells to return towards the heart low in oxygen (yet higher in carbon dioxide).

The heart is made up of: (red= blood oxygenated-left side, blue= blood deoxygenated-right side)

·         the aorta (artery taking blood to body cells)

·         the pulmonary vein (brings oxygenated blood back to body)

·         the left atrium

·         the left ventricle

·         the left side of apex (the ventricle wall, much thicker on left side to push blood to whole body)

·         the pulmonary artery (takes blood to lungs)

·         superior vena cava (blood coming from brain)

·         inferior vena cava (blood coming from body)

·         right atrium

·         right ventricle

·         right side of apex (thinner as not to burst alveoli in lungs)

·         Both sides are separated by the septum and both have atrio ventricular


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