3.3 Photosynthesis

Question 1

Where does photosynthesis take place?

Answer 1

• In the leaves of plants, in chloroplasts

Question 2

What is the word equation for photosynthesis?

Answer 2

carbon dioxide + water —> glucose + oxygen

Question 3

Is photosynthesis an exothermic or endothermic reason? why?

Answer 3

Endothermic - Endothermic reactions are chemical reactions in which the reactants absorb heat energy from the surroundings to form products.

Question 4

How does the leaf get the carbon dioxide?

Answer 4

The carbon dioxide diffuses into the leaves through the stomata

Question 5

How does the leaf get the water for photosynthesis?

Answer 5

It diffuses from the soil into the root hair cells by osmosis then transported to the leaves by the xylem

Question 6

What 6 things is glucose used for in a plant?

Answer 6

• Cellular respiration: breaks the glucose apart to release energy.
• Photosynthesis: traps the suns light energy in glucose molecules and then other cells around the plant can break the glucose apart again to release the energy when they need it
• Lots of glucose molecules can be combined to make cellulose (complex carbohydrate that plants use to strengthen their cell walls)
• Glucose molecules can combine to make starch, another complex carbohydrate but it doesn’t have a particular function. Form of glucose for long term storage: compact and insoluble (wont draw water into cell via osmosis)
• Making amino acids by combining the glucose molecules with nitrate ions which they get from the soil. They can combine these amino acids to make proteins
• Making oils + fats, this can be stored as future energy source (seeds)

Question 7

Often, what is a plants growth rate determined by?

Answer 7

How fast they can photosynthesise

Question 8

What is the first stage of photosynthesis?

Answer 8

Energy transferred by light to the chlorophyll is used to split water into oxygen gas and hydrogen ions - the oxygen is released as a waste product

Question 9

What is the second stage of photosynthesis?

Answer 9

Carbon dioxide gas then combines with the hydrogen ions to make glucose

Question 10

What is the molecular formula for glucose?

Answer 10

C^6H^12O^6

Question 11

What makes starch a useful long term storage molecule? (3)

Answer 11

• It is insoluble in water
• It can easily be broken down when needed
• It is compact

Question 12

Which useful energy transfer or conversion happens overall in photosynthesis?

Answer 12

light —> chemical