Biology Part 2A

Describe and explain all the features of an animal cell. 

Animal Cells: 

Nucleus - Controls all activities of the cell. Cell membrane - Controls what enters/leaves the cell. Hold the cell together. Cytoplasm - Jelly-like substance, where chemical reactions take place. It contains enzymes. Mitochondria - Where respiration takes place and energy is created for the cell to function. Ribosomes - Where proteins are made. 

Describe and explain all the features of a plant cell. 

Plant Cells: 

Nucleus - Controls all activities of the cell. Cell membrane - Controls what enters/leaves the cell. Hold the cell together. Cytoplasm - Jelly-like substance, where chemical reactions take place. It contains enzymes. Mitochondria - Where respiration takes place and energy is created for the cell to function. Ribosomes - Where proteins are made. Cell wall - made of cellulose. It supports and strengthens the cell. Permanent vacuole - Contains cell sap, a weak solution of sugars and salts. Chloroplasts - Where photosynthesis occurs which makes food for the plant. Contain chlorophyll. 

Describe a yeast cell: 

A yeast cell is a microorganism. 

It has: 

A nucleus, cell membrane, cell wall and cytoplasm. 

Describe a bacteria cell: 

A bacteria cell is a microorganism. 

It has: 

A cell membrane, cell wall and cytoplasm which contains genetic material as there's no nucleus. 

Carbon dioxide + Water                      Glucose + Oxygen 

CO2 + H2O                          C6H12O6 + O2

6CO2 + 6H2O                      C6H12O6 + 6O2

Explain what the limiting factors are:

Light Intensity -Without enough light, a plant cannot photosynthesise very quickly, even if there is plenty of water and carbon dioxide. Increasing the light intensity will boost the speed of photosynthesis. 

Carbon Dioxide Concentration - Sometimes photosynthesis is limited by the concentration of carbon dioxide in the air. Even if there is plenty of light, a plant cannot photosynthesise if there is insufficient carbon dioxide.

Temperature - If it gets too cold, the rate of photosynthesis will decrease. Plants cannot photosynthesise if it gets too hot.

Describe the uses of glucose in a plant: 

1. Respiration - Releases energy which enables them to convert the rest of the glucose into other substances which can build new cells so the plant grows. To produce these substances they need minerals from soil. 

2. Making Cell Walls - Glucose is converted into cellulose which makes cell walls strong. 

3. Making Proteins - Glucose is combined with nitrate ions (from the soil) to make amino acids which are then made into proteins. 

4. Stored in Seeds - Glucose is turned into lipids (fats and oils) for storing in seeds. 

5. Stored as Starch - Glucose is turned into starch and stored in the roots, stems and leaves ready for when photosynthesis isn't happening. Starch is insoluble so doesn't draw in water and swell. 

Explain how farmers/gardeners can control photosynthesis to produce higher yield. Evaluate the advantages and disadvantages. 

1. Greenhouses help to trap the sun's heat so temperature isn't limited. Heaters in winter may help the temperature to stay at an ideal level as will shades and ventilations in summer. 

2. Artificial light is often supplied once the sun has gone down to give plants more quality photosynthesis time. 

3. By using a paraffin heater, CO2 levels are increased.

4. Keeping plants enclosed protects them from pests and diseases. Fertilisers are often added to the soil to provide minerals for healthy growth. 

However, the additional cost of providing extra lighting, heat and carbon dioxide has to be weighed against the increased crop yield and the extra income it will provide. The cost of should not exceed the additional income it generates for the farmer.