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Biology 10 > Photosynthesis > Flashcards

Photosynthesis Flashcards

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1
Q

What is the equation for photosynthesis?

A

Water + carbon dioxide -> glucose + oxygen
6H2O + 6CO2 -> C6H12O6 + 6O2

  1. Light energy is absorbed by a green substance called chlorophyll.
  2. This energy is used to convert carbon dioxide and water into sugar (glucose).
  3. Oxygen is released as a by-product.
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2
Q

How is a leaf adapted for photosynthesis?

A

It needs carbon dioxide, light and water so:

  1. Large surface area of leaves to absorb light - wide and flat leaves with waxy cuticle to prevent water loss
  2. Thin surface to allow gases in with short diffusion distance - spongy mesophyll not tightly packed allowing CO2 in with irregular cells
  3. Leaves contain chlorophyll in chloroplasts to absorb light - palisade cells, block shaped and packed into layers
  4. Veins a)carry water through xylem to leaf cells and b)glucose away through phloem and c)to support leaves
  5. Stomata are pores on underside of leaves which allow gases to move in and out
  6. Guard cells that open and close the stomata to regulate gas exchange and on bottom of leaf to limit water loss
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3
Q

What factors affect rate of photosynthesis and why?

A

These are “limiting factors”

  1. Amount of light
  2. Amount of carbon dioxide
  3. Temperature
  4. Chlorophyll levels in the leaf
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4
Q

Why is photosynthesis an endothermic reaction?

A
  1. It is endothermic because it takes energy from its surroundings eg heat, light, carbon dioxide and water.
  2. The energy transferred from the environment when bonds holding carbon dioxide and water are broken is more than that transferred back to the environment with the formation of new bonds in glucose and oxygen
  3. The extra energy is transferred by light
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5
Q

What does photosynthesis do?

A
  1. Plants don’t eat but make their own food by photosynthesis
  2. Photosynthesis takes place in green part of plants esp. leaves
  3. Photosynthesis takes place in the light
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6
Q

Explain the process of photosynthesis?

A
  1. Plant leaves/algae cells are full of chloroplasts
  2. Chloroplasts contain chlorophyll
  3. Energy transferred from environment to chloroplasts by light.
  4. Energy is transferred to convert carbon dioxide from the air and water from soil.
  5. This produces simple sugar called glucose with oxygen as by product
  6. Oxygen released into air
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7
Q

How is the glucose used by the plant?

A
  1. Some is used immediately by cells for respiration.
  2. Most is converted into insoluble starch and stored.
  3. Some is used to build up glucose into cellulose and complex carbohydrates
  4. To make amino acids combining sugars with nitrate ions and mineral ions in the soil
  5. To make fat or oil for storage
  6. To make proteins - plants also use nitrate ions from soil
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8
Q

How do algae photosynthesise?

A
  1. Algae are aquatic so photosynthesise in water.
  2. Large surface area absorbing carbon dioxide from surrounding water.
  3. Oxygen produced dissolves into water when released
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9
Q

How can plants help the environment

A

Plants absorb carbon dioxide so

  1. more photosynthesis will remove more carbon dioxide and help reduce global warming
  2. More photosynthesis will also produce more crops for food.
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10
Q

How does light affect photosynthesis?

A

Light intensity is the most obvious factor affecting rate of photosynthesis
If there is little or no light then photosynthesis will stop
The brighter the light the faster the rate of photosynthesis

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11
Q

How does temperature affect photosynthesis

A

Temperature affects all chemical reactions including photosynthesis.
Rate of photosynthesis with temperature rise as the reaction rate speeds up.
Photosynthesis controlled by enzymes
Most enzymes denature when temperature rises to over 40C
When enzymes denature rate of photosynthesis falls

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12
Q

How does carbon dioxide concentration affect photosynthesis

A

The atmosphere has 0.04% carbon dioxide
This limits rate of photosynthesis
On a sunny day carbon dioxide concentration is the most limiting factor
Increasing carbon dioxide concentration increases rate of photosynthesis
Carbon dioxide levels rise at night because plants respire but don’t photosynthesise in the dark.
So in the morning as light and temperature rise most carbon dioxide around plant gets used up.
In a lab or greenhouse carbon dioxide levels can be increased to speed up photosynthesis but outside light,heat and carbon dioxide are all limiting factors

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13
Q

How do chlorophyll levels in the leaf affect photosynthesis

A

If chlorophyll levels in a leaf are limited less photosynthesis will occur
If the plant has insufficient minerals especially magnesium it cannot make chlorophyll and plant may die.
Variegated leaves grow less vigorously because less chlorophyll

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14
Q

How do plants and algae use glucose

A
  1. Some glucose is used in respiration, providing energy for cells as it is broken down. Respiration is the reverse of photosynthesis
  2. Plants build up glucose into complex carbohydrates eg cellulose to strengthen cell walls
  3. Produce starch for storage. Starch is insoluble but glucose is soluble.
  4. To make amino acids by combining sugars with nitrate ions and other minerals ions like proteins
  5. To make fats and oils-lipids
  6. Mixes with magnesium to make chlorophyll
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15
Q

Why do plants use cellulose

A

Glucose builds up smaller molecules into bigger ones

Makes complex carbohydrates like cellulose to strengthen cell walls

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16
Q

Why do plants make and store starch

A

Glucose converts to starch

  1. Glucose is soluble so could affect how water moves by osmosis and affect water balance of whole plant
  2. Starch is insoluble in water so has no effect on water balance and plants can store lots of it - no osmotic effect
  3. Main energy store for when dark or light levels low- found in cells all over the plant
  4. Also in special storage areas eg bulbs, tubors to help survive winter
  5. Starch has a compact shape
  6. Humans use these eg potato and onions
17
Q

How do amino acids help plants

A
  1. Glucose combines with nitrate and other ions
  2. Build up into proteins eg enzymes
  3. Algae make amino acids using ions from surrounding water
  4. Low mineral areas eg bogs make growth difficult
  5. Some plants survive low mineral soil by taking nutrients from insects eg Venus fly trap using enzymes to digest insects
18
Q

Why do plants need lipids

A
  1. Lipids may be used as an energy store
  2. To make cell walls stronger
  3. Energy store in seeds providing food for new plant as it germinates
  4. Some algae possible biofuels
19
Q

How does a greenhouses affect rate of photosynthesis?

A

Glass or plastic helps control environment
Atmosphere is warmer inside than outside and speeds up photosynthesis
Crops grow better and flower quicker
Can be used to grow fruit that doesn’t grow well outside eg peaches

20
Q

How can you control limiting factors

A

Greenhouses control amount of light, temperature and carbon dioxide to find fastest rate of photosynthesis.
Can also be grown in water with perfect mineral balance - hydroponics.
The crops are soil free and there is no need to plough
The cost and economics are very important

21
Q

Which part of the leaf is involved in photosynthesis

A

Palisade cells

22
Q

How do we test for starch in plants eg potatoes

A

Iodine solution turns blue/black in presence of starch

The plant leaves need to be boiled to remove waxy coating and left in iodine

23
Q

Describe ways to decrease rate of photosynthesis

A 
It is an endothermic reaction needing light energy. 
It needs carbon dioxide 
It needs a warm temperature 
It also needs water
It also needs nutrients
24
Q

In which part of the plant does photosynthesis take place

A

Chloroplasts

25
Q

What does the waxy cuticle do

A

Stops water loss from leaf

26
Q

What does spongy mesophyll do

A

Allows carbon dioxide in
Not tightly packed
Irregular cells

27
Q

What do palisade cells do

A

Specially adapted with lots of chloroplasts
Receive light and catch sunlight for photosynthesis
Block shaped
Packed into layers

28
Q

What do xylem and phloem do

A

Xylem move water and solutes from the root through the plant to leaves
Phloem moves food substances from leaves to rest of plant

29
Q

What do guard cells and stomata do

A

Carbon dioxide cannot diffuse Into the leaf
Stomata are specialised doors
Guard cells on bottom of leaf limit water loss

30
Q

What factors may limit rate of photosynthesis

A

Shortage of light
Low temperature
Shortage of carbon dioxide

Biology 10 (22 decks)

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