Unit 1 Revision: Photosynthesis

​Unit 1. Revision

By Tsatsral Ts

Contents

• Photosynthesis

• Collecting the gas produced in Photosynthesis

• Testing a leaf for starch

• Minerals and plant growth
  

Multiple Choice

What are the reactants for photosynthesis?

• glucose and oxygen

• water, and carbon dioxide

• sunlight and chlorophyll

• Glucose

• Oxygen

​the products

• Water

• Carbon dioxide

​the reactants

Photosynthesis

Open Ended

Why is photosynthesis important?

​Why is photosynthesis important?

• Photosynthesis provide energy, in the form of chemical energy in nutrients, for most other organisms.

• Photosynthesis is so important is that it provides oxygen for the Earth’s atmosphere. Animals and plants, of course, need oxygen for respiration.

Collecting the gas produced in Photosynthesis

Multiple Choice

Which is the independent variable?

• change

• measure

• same

Independent variable ( change)

Dependent variable (measure)

Multiple Choice

In which part of a cell is starch stored?

• Chloroplast

• Chlorophyll

• Cell membrane

• Cytoplasm

​cell parts (organelles)

Plants store carbohydrates as starch. 

They store the starch inside the chloroplasts in their cells.

Testing a leaf for starch

1. Dip a leaf into boiling water from about a minute (to soften it).

2. Turn off the Spirit burner.

3. Put the leaf into a test-tube of ethanol

4. Stand the test-tube in a beaker of hot water for about 10 minutes.

5. Wash the leaf in cold water

6. Spread the leaf out flat on a white tile and cover it with iodine solution (test for starch)

7. If the leaf goes blue-black, starch is present.

​Testing a leaf for starch

Multiple Choice

Explain why it was important to boil the leaf before the starch test could work.

• Boiling breaks down the cell membranes, so the iodine can reach the starch.

  
  

• Boiling breaks down the cell wall, so the iodine can reach the starch.

• This makes it easier to see the colour change when iodine solution is added

• To remove the chlorophyll

Multiple Choice

Why is ethanol used in the experiment?

• To increase the temperature of the water

• To remove the chlorophyll

• To remove the chloroplast

• To make the leaf float

Multiple Choice

What happens to the color of iodine when it reacts with starch?

• It remains orange-brown

• It turns from yellow to purple

• It turns from red to green

• 
  It turns from orange-brown to blue-black

Multiple Choice

What is the main function of the cuticle (waxy layer) on a leaf?

• To allow air to enter and exit the leaf

• To carries water

• protect the cells inside the leaf

• To keep the leaf from drying out

Multiple Choice

The less tightly packed area in this portion of the leaf increases space for gas exchange.

• spongy layer

• palisade layer

• Vein

• epidermis

Nitrate contains nitrogen atoms. 

These are needed so that the plant can convert carbohydrates to proteins.

Nitrate

Magnesium is needed to make the green pigment, chlorophyll.

​Magnesium

Minerals and plant growth

Proteins are essential for making new cells, so that the plant can grow well. Without enough nitrate leaves die and the plant stays small.

​Nitrate

If a plant does not have enough magnesium, its leaves look yellow instead of green. It cannot grow well, because it does not have much chlorophyll to absorb energy from sunlight, and so it cannot photosynthesise as much as it should.

​Magnesium

Minerals and plant growth

Multiple Choice

Why do plants need nitrate ion?

• To make the plant strong and healthy

• To give green color to leaves

• To make amino acid which is then use to make protein for growth

• To make the plant alive

Thank you for your active participation in the lesson.