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BGS GCSE Biology Unit 1 > Photosynthesis > Flashcards

Photosynthesis Flashcards

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1
Q

Where does photosynthesis happen in the leaf?

A

chloroplast

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2
Q

Photosynthesis is an endothermic reaction. What does this mean?

A

absorbs light energy from the sun

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3
Q

What is the word equation for photosynthesis?

A

carbon dioxide + water -> glucose + oxygen

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4
Q

What is the chemical equation for photosynthesis?

A
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5
Q

How do you destartch a leaf?

A

Placing them in the dark for 48 hours

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6
Q

What are the 5 steps to test a leaf for starch?

A
  1. Destarch the plant
  2. Boil the leaf in water
  3. Leaf placed in ethanol
  4. Lead placed in warm water
  5. Iodine dropped in leaf
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7
Q

Why do you destarch a leaf?

A

To enusre any starch made was created during the experiment

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8
Q

Why do you boil the leaf in water when testing for starch?

A

Killing the leave and stops further reactions

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9
Q

Why do you place the leaf in ethanol when testing for starch?

A

Removes the chlorophyll (green colour) so decolourises the leaf

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10
Q

What is one safety precaution when placing the leaf in ethanol?

A

Bunsen burner must be turned off as ethanol is HIGHLY flammable

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11
Q

Why do you place the leaf back in warm water when testing for starch?

A

Softens the leaf (less brittle) so it can be spread out

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12
Q

What is the colour change for iodine if the leaf tests positive for starch?

A

yellow/brown to blue/black

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13
Q

Some leaves are green where chlorplast are present and white where they are not. What are these leaves called?

A

Variegated

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14
Q

How would you test if carbon dioxide is needed for photosynthesis?

A

Use two conical flasks with similar photosynthesising plants in each. This ensures that no carbon dioxide enters the atmosphere surrounding the plants. Place soda lime (sodium hydroxide) in one flask to absorb carbon dioxide but not in the other (acts as a control flask to which the other can be compared).

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15
Q

What is the function of the waxy cuticle?

A

Thin and transparent physical defence- allows light through. Waterproof layer that reduces water loss by evaporation.

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16
Q

What is the function of the upper epidermis?

A

Lacks chloroplasts and so allows light to reach the mesophyll cells

17
Q

What is the function of the pallisade mesophyll?

A

-Regular structured cells that are closely packed together which increase the surface area for light absorption.
-They contain a high concentration of chloroplasts and hence chlorophyll for maximum light absorption for photosynthesis.

18
Q

What is the function of the spongy mesophyll?

A

-Contain inter-cellular air spaces for gaseous exchange (allows carbon dioxide to enter and oxygen to leave the photosynthesising cells in the palisade mesophyll)
-Cells have a large surface area and moist walls which enhance diffusion of gases

19
Q

What is the function of the guard cells?

A

Control the opening and closing of stomata and therefore regulate gaseous exchange.

20
Q

What is the function of the stomata?

A

Pores on the underside of the leaf which allow gases to diffuse. Stomata are open during the day and close at night –to control the evaporation of water

21
Q

Define limiting factor

A

If any of the raw materials needed for photosynthesis are in short supply then the rate of photosynthesis will slow down – this is the limiting factor

22
Q

What are the three limiting factors?

A

Light, carbon dioxide and tmeperature

23
Q

What chemical can be used to determine the amount of carbon dioxide in the air?

A

hydrogen carbonate indicator

24
Q

What conditions would hydrogen carbonate indicator be purple?

A

decrease in carbon dioxide
(photosynthesis is greater then respiration)

25
Q

What conditions would hydrogen carbonate indicator be red?

A

rate of photosynthesis is equal to the rate of respiration. There is no net gas exchange. This is the compensation point
(dawn and dusk)

26
Q

What conditions would hydrogen carbonate indicator be yellow?

A

Respiration greater than photosynthesis
increases carbon dioxide levels

BGS GCSE Biology Unit 1 (7 decks)

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