Biology - How Plants Produce Food

What is the equation for photosynthesis?

Carbon Dioxide + Water (+ light energy)   Glucose + Oxygen

What in the cell contains the chlorophyll?

The choloplasts.

What is absorbed by the chorophyll?

Light energy.

What happens to the glucose that is produced through the proccess of photosynthesis?

Some of it is used immediately in the plant for food. However, most of it is converted into starch for storage.

What can you test for starch with?

You can test for starch using iodine which turns from a yellow/brown colour to dark blue when reacted with starch.

What adaptations do plants have that help with photosynthesis?

• Most have broad leaves - big surface area for light to get too.
• Chloroplasts with chlorophyll to absorb light energy.
• Air spaces to let in carbon dioxide and let out oxygen.
• Veins - To transport water from the soil to all over the plant.

Label.

1. Waxy Cuticle - Forms a waterproof layer to stop any loss of water.

2. Upper Epidermis - Consisting of epidermal cells. These have no chloroplasts.

3. Palisade cells - These contain lots of chloroplasts, which contain lot of chlorophyll. This is where photosynthesis is carried out.

4. Spongy Mesophyll Layer

5. Air Spaces - allow for diffusion of water vapour etc...

6. Guard Cells - These form stomata (pores) which allow for the diffusion of gases in and out of the plant.

7. Leaf Vein - containing xylem and phloem tubes

What three main factors affect the rate of photosynthesis, and why?

• Light - Vital for photoynthesis. Without it = no photosynthesis.
• Temperature - Affects all chemical reactions - photosynthesis is controlled by enzymes - temp too high = denatured enzymes, temp too low = enzymes work very slowly
• Carbon Dioxide Levels - Most limiting factor - often not enough in the air.

Plants respire all the time. True or false?

True, like all in living things plant cells respire all the time.

What do plants use the energy from respiration for?

• To build up smaller molecules into bigger molecules - glucose into starch, glucose into cellulose (used to make new plant cell walls)
• To combine sugars with other nutrients to make amino acids that become protiens.
• To build up fats and oils to make up a food store in seeds.

How is the food made via photosynthesis transported to the other parts of the plant?

Through two transport systems

1. The Phloem - made up of living tissue - Transports sugars everywhere including the growing regions of the plant and storage organs to provide food store for winter.

2. The Xylem - Carries water and mineral ions from the soil all around the plant.

What are xylem and phloem contained in, and what cells are there between them?

They are contained in a vascular bundle and between them are cabium cells which will grow into new xylem an phloem cells.

What are the differences between the characteristics of xylem and phloem tubes?

• Phloem - Have thin walls + are living
• Xylem - Have thick strong walls + are not living

Is either glucose or starch soluble?

Glucose is soluble, but starch is insoluble.

Why is starch better than glucose for the plant to store in large amounts?

Starch is not soluble, whereas glucose is. If glucose was stored in large amounts in the plant cells it would affect the water balance of the whole plant. Because starch is insoluble, it doesn't affect the water balance of the plant at all.

What do plant tubers and bulbs contain a lot of?

Starch, to help them last through the winter.

Why do plants need nitrates, where do they get them from and what are the symptoms of a deficiancy?

Plants need nitrates because they produce proteins are vital for the plants growth. They are found in the soil, but if the soil isn't nitrate rich, the plants growth will be stunted.

Why do plants need magnesium, where do they get it from and what are the symptoms of a deficiancy?

Plants need magnisium to make chlorophyll which is vital for photosynthesis. It comes from the soil and plants only need a tiny amount but if there is not enough then the plant gets pale yellow leaves where it has no chlorophyll.