Gas exchange in plants and photosynthesis

Question 1

In photosynthesis, what do plants use the simple molecules of carbon dioxide and water to make?

Answer 1

Glucose and oxygen

Question 2

What is the name for the process that occurs in plants as well as some bacteria and protoctista? It is where the simple molecules of carbon dioxide and water make glucose and oxygen.

Answer 2

Photosynthesis

Question 3

What is the word and balanced chemical equation for photosynthesis?

Answer 3

Carbon dioxide + water —> glucose + oxygen

6CO₂ + 6H₂O —> C₆ H₁₂O₆ + 6O₂

Question 4

Photosynthesis converts light energy into what type of energy?

What can this new type of energy be used for by the organism?

Answer 4

Photosynthesis convert light energy into stored chemical energy, which can be used by the organism for respiration and for making other biological molecules.

Question 5

What is glucose used for by plants when they are making other molecules?

Answer 5

1) Chlorophyl
2) Lipids
3) Amino acids, joined together to make proteins
4) DNA
5) Carbohydrates
6) sucrouse for transport
7) starch for storage
8) Cellulose

Question 6

What does the plants need the mineral ion nitrates (NO₃) for, and what are the symptoms of a deficiency of nitrate ions?

Answer 6

The mineral ion nitrate is used by plants to make amino acids, proteins, DNA and RNA.

A symptom of a deficiency of nitrate ions is stunted growth.

Question 7

What do plants need the mineral ion magnesium (Mg) for, and what are the symptoms of a deficiency of magnesium?

Answer 7

The mineral ion magnesium is used by a plant to make chlorophyll.

A symptom of the deficiency of magnesium is yellowed leaves.

Question 8

What do plants need the mineral ion phosphate (PO) for, and what are the symptoms of a deficiency of phosphate?

Answer 8

The mineral ion phosphate is required to make RNA and DNA, and is part of the cell membrane.

Symptoms of a deficiency of phosphate are poor root growth and purple younger leaves.

Question 9

What are the factors affecting the rate of photosynthesis?

Answer 9

Light, carbon dioxide concentration and temperature

Question 10

The factors affecting photosynthesis are light, carbon dioxide concentration and temperature. What do we call a factor which is in shortest supply?

Answer 10

The limiting factor

Question 11

What would happen to the enzymes if the temperature during photosynthesis increased well beyond the optimum temperature?

Answer 11

With extreme temperatures the enzymes become denatured, and no longer work.

Question 12

How would we measure the rate of photosynthesis in pond weed? What would we measure, and how?

Answer 12

We would measure the rate of photosynthesis in pondweed by measuring the volume of oxygen produced per minute.

This can be measured by counting the number of bubbles, or collecting the gas in an inverted test tube and measuring the volume.

Question 13

What is the chemical equation for plants when they photosynthesise?

Answer 13

6CO₂ + 6H₂O —> C₆H₁₂O₆ + 6O₂

Question 14

The leaf stores some of the glucose made in photosynthesis in the form of starch. How can we test leaves for starch?

Answer 14

We can test leaves for starch using iodine solution. This turns from orange to blue black when starch is present.

Question 15

Label the diagram of the leaf

Answer 15

Question 16

For photosynthesis a leaf has a large surface area and is thin, why?

Answer 16

A leaf has a larger surface area and is thin, to maximise absorption of sunlight by the photosynthetic cells. It also increases the number of stomata, so that carbon dioxide can diffuse quicker.

Question 17

For photosynthesis, the upper epidermis of the leaf is transparent, why?

Answer 17

The upper epidermis is transparent to allow light to penetrate to the mesophyll.

Question 18

Label this diagram of a leaf structure

Answer 18