B4 D-F

  • Created by: Lilly
  • Created on: 03-11-14 20:51

B4 D-F

What is Diffusion?

Diffusion is the spreading of particles of a substance,resulting in a net movement of particles from a region of high concentration to a region of low concentration.

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How do gases move in and out of leaves?

By diffusion

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Which substance moves out of respiring cells?

Carbon dioxide

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What is Osmosis?

Osmosis is the net movement of water accross a partially permeable membrane, from an area of high concentration to an area of low concentration.

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What is a partially permeable membrane?

It is only when only some molecules can pass through a cell membrane. For instance the cell membrane has tiny holes called pores. Larger molecules such as sugars and proteins are too bid to pass through the pores, but very small molecules including water can pass through it.

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Explain the term flaccid:

When the cell loses water by osmosis. The turgor pressure falls and the cell becomes soft (flaccid).

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Explain the term Plasmolysed:

When the cell contents collapse away from the cell wall. 

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How are plants supported by turgor pressure?

 Water pressure acts against an inelastic cell wall.

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In plant cells, what acts as a partially permeable membrane?

Cell membrane

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Plant Structure

What is an organ?

Groups of different tissues work together as an organ.

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Plant Structure

Describe the structure of a Phloem: (site of tranlocation)

  • Phloem are living cells and are stacked on top of each other in tubes
  • They are not continuous.
  • They transport food substance to parts of the plant.
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Plant Structure

Describe the structure of a Xylem:

  • They have dead cells.
  • Contain a hollow cavity called the lumen.
  • Stacked on top one another to form a long hollow tube-like vessel.
  • They are not continuous & are strengthened with cellulose.
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Plant Structure

Roots hairs incraese the ability of roots to take up water by osmosis by increasing the surface area of the roots.

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Transport In Plants

What is transpiration?

The movement of water and dissolved minerals from the roots to the shoots and leaves.

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Transport In Plants

What is Translocation?

Translocation is the the movements of food substances up and down stems to growing and storage tissues.

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Transport In Plants

What are the four factors which affect the rate of Transpiration?

  • Increase in Light intensity.
  • Increase in Temperature.
  • Increase in Air movement.
  • Decrease in Humidity.
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Transport In Plants

Explain how the cellular structure of a leaf is adapted to reduce water loss.

  • Very few stomata on the upper of the leaf.
  • Plants that live in dry areas, often have fewer stomata and they are enclosed on the inner surface of a rolled leaf, protected from the Sun.
  • Each stomata can be opened or closed.

      - When the plant is photosynthesising the stomata are open.

      -The stomata are closed at night.

     - When the stomata are closed water loss is reduced.

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Rates of Transpiration

What does Transpiration provide plants?

It provides plants with water for cooling, photosynthesis, support and movements of minerals.

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Rates of Transpiration

Explain why transpiration is increased by Light intensity:

Stomata closes in the dark and opens in the light. 

- When the light intensity is greater, more stomata will open. This allowsmore water to evaporate, so rate of transpiration will be faster.

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Rates of Transpiration

Explain why transpiration is increased by temperature:

The higher the temperature, the faster the particles in the air will move. This means that watermolecules move faster and evaporate from the leaf quiker. So the rate of transpiration will increase.

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Rates of Transpiration

Explain why transpiration is increased by air movement:

The faster the air movement, the quicker the water will be moved. This increases the diffusion of water out of the leaf, because the water mlecules do not buils in the air outside the leaf.

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Rates of Transpiration

Explain why transpiration is affected by a decrease in humidity:

The less humid air, the less water there is in it. This again make for a greater concentration gradient between the inside and outside of the leaf.

Water molecules will diffuse more quickly,so increasing the rate of transpiration.

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Plant Minerals

Active Transport:

Plants absorb minerals through hairs on the roots. The minerals are absorbed even though they have to move against concentration gradient. 

They are absorbd using a process called active transport. This process requires energy which it gets from respiration. This is why roots need a good supply of oxygen.

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Plant Minerals

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