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Biology 4•5•6 > B4 > Flashcards

B4 Flashcards

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0
Q

Photosynthesis produces glucose for biomass and energy. Oxygen is released as a by product. What is the word and symbol equation for photosynthesis?

A

Light
Carbon dioxide + water ——-> glucose + oxygen
Chlorophyll
6CO2 + 6H2O —> C6H12O6 + 6O2

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1
Q

Define: photosynthesis

A

• The process in which green plants make their own food (glucose and starch) using sunlight

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2
Q

How was the theory of photosynthesis gradually accepted?

A
  • Greeks - plants gained mass by taking in minerals though soil
  • Van Helmont - plant growth cannot be solely due to nutrients in soil
  • Joseph Priestly - put a plant in a jar if air, and a plant in a jar with a mouse inside. He changed combinations of plants and mouse and concluded that oxygen is produced by plants
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3
Q

Glucose can either be…

A
  • Used straight away to produce energy through respiration

* Converted in substances that the plant needs

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4
Q

What are the properties of glucose?

A
  • Soluble
  • Transported around the plant as soluble sugar
  • But must be converted into starch, which is insoluble, in order to be stored
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5
Q

Glucose and starch can be converted into:

A
  • Energy (respiration)
  • Proteins for growth + repair
  • Starch, days or oils that can be stored in seeds
  • Cellulose which is needed for plant cell wall
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6
Q

Why is starch such a useful storage molecule?

A

• Insoluble so it doesn’t affect the water concentration inside cells
• It does not move away in solution from storage areas
- If the cells stored soluble glucose, the inside if the cells would become very concentrated and water would constantly move in through osmosis, which would make the cell swell

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7
Q

Photosynthesis can be increased by increasing:

A
  • the temperature - using heaters in a greenhouse
  • the light intensity - using lamps in greenhouse
  • the carbon dioxide - CO2 concentration is increased by chemicals
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8
Q

Describe the effect of temperature of photosynthesis.

A
  • As temperature rises, so does the rate pd photosynthesis
  • This means temperature is the limiting factor in rate of photosynthesis
  • As the temperature reaches 45°C, the enzymes controlling photosynthesis start to become denatured
  • Once denatured the rate declines to zero
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9
Q

Describe the effect of carbon dioxide concentration on the rate of photosynthesis.

A
  • As the concentration rises, so does the rate of photosynthesis
  • Carbon dioxide is limiting the rate of photosynthesis, up until a certain point
  • After this point, a rise in carbon dioxide levels makes no difference
  • So, carbon dioxide is no longer a limiting factor; light or temperature must be
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10
Q

Describe the effect of flight intensity on the rate of photosynthesis.

A
  • As light intensity rises so does the rate of photosynthesis
  • This means light is a limiting factor up to a certain point
  • After a certain point, a rise in the light intensity has no effect
  • Light intensity is no longer the limiting factor; carbon dioxide or temperature must be
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11
Q

Explain respiration through night and day.

A

• During the day light is readily available from the sun so plants photosynthesise; taking in carbon dioxide to make glucose and releasing oxygen as a by-product

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12
Q

What is the chlorophyll in a leaf?

A
  • Contains a pigment called chlorophyll (which absorbs light) in millions of chloroplasts
  • Plus other pigments to absorb light from different parts of the spectrum
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13
Q

Describe the surface area of a leaf?

A
  • Broad and flat

* Provides huge surface area to absorb sunlight

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14
Q

What do vascular bundles in a leaf do?

A
  • Needed for support and to transport water to the cells

* Removes the products of photosynthesis such as glucose

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15
Q

Why does a leaf have such a thin structure?

A

• So that gases (carbon dioxide and oxygen) only have a short distance to travel to and from the cells

16
Q

What does the stomata do?

A
  • Stomata are essentially tiny pores
  • On the underside of the leaf to allow the exchange of gases
  • They are opened and closed by guard cells
17
Q

What happens in a plant during photosynthesis?

A
  • Carbon dioxide diffuses in through the stomata (leaf pores)
  • Oxygen diffuses out the stomata
  • Water is absorbed by the roots
18
Q

What are the four distinct layers in a leaf?

What are the properties of each layer?

A

• Upper epidermis - transparent to allow sunlight to the later below
• Palisade layer - where the cells are near to the top of the leaf and are packed with chloroplasts so they can absorb the maximum amount of light
• Spongy mesophyll - contains lots of air spaces connected to the stomata to allow the optimum exchange of gases
• Lower epidermis
* This internal structure provides a high surface area to volume ratio for efficient gas exchange*

19
Q

What is specialised about the shape of a chloroplast in appellant cell and why aren’t they in all plant cells?

A
  • They are long to absorb lots of light
  • Not found in all cells
  • Such as root cells as they don’t receive any light
20
Q

Define: diffusion

A
  • Substances move in and out of cell membranes by diffusion.
  • It’s the movement of a substance from a region of high concentration to a region of low concentration
21
Q

Describe the particle movement in diffusion?

A
  • Particles move about in lots of different directions
  • Random movement
  • Net (overall) movement of of particles from an area of high concentration to an area of low concentration
22
Q

What increases the rate of diffusion?

A
  • There’s a greater surface area of the cell membrane
  • There’s a steeper concentration gradient
  • The particles have a shorter distance to travel
23
Q

What do oxygen and carbon dioxide do during the day?

A
  • Carbon dioxide is used up in photosynthesis (The concentration inside the leaves is lower than outside them
  • Carbon dioxide diffuses into the plant through the stomata on the underside of the leaf
  • Oxygen diffuses from the plant into the atmosphere
24
Q

What happen to carbon dioxide and oxygen in the night?

A

• Photosynthesis stops
• Oxygen diffuses into leaf cells
• Carbon dioxide diffuses out of leaf cells
• The stomata on the underside of the leaves are specially adapted to:
- open to help increase the rate of diffusion of carbon dioxide and oxygen
- close to prevent excessive water loss in drought conditions

25
Q

What are the purposes of the four main mineral essential for healthy plant growth?

A
  • Nitrates - to make amino acids that form proteins
  • Potassium - is used to help enzymes in respiration and photosynthesis
  • Phosphates - are used to make DNA and cell membranes
  • Magnesium - is used to make chlorophyll for photosynthesis
26
Q

What are the visible results of lack of the four main minerals in plants?

A
  • Lack of nitrates - poor growth, yellow leaves
  • Lack of potassium - poor flower + fruit growth, discoloured leaves
  • Lack of phosphates - poor root growth, discoloured leaves
  • Lack of magnesium - yellow leaves
27
Q

Define: biological control

A

• Where a farmer introduces a predator, instead of using pesticide, to reduce the number of pests

28
Q

Advantages of biological control

A
  • The predator selected only usually attacks the pest (specie specific)
  • Once introduced, the predator can have an impact over many years, so repeating treatment isn’t required
  • The pest can’t become resistant to the predator (unlike pesticides)
  • No need for chemical pesticides
29
Q

Disadvantages of biological control

A
  • The pest reduces but isn’t completely removed
  • The predator may not eat the pest or it may even eat useful species
  • The predator may reproduce uncontrollably
  • The predator may leave the area
30
Q

Advantages of hydroponics

A
  • The mineral levels added to the solution can be carefully controlled and adjusted to the type of plant
  • The risk if the plants becoming diseased is reduced
31
Q

Disadvantages of hydroponics

A
  • Plants must be supported as they have no anchorage for their roots
  • Expensive fertilisers are needed to supply the plant with minerals
32
Q

Define: organic farming

A

• Organic farming methods aims to produce food without the use of chemicals, so minimising the impact on the environment (no pesticides or artificial fertilisers)

33
Q

List some organic farming methods.

A
  • Using natural fertilisers such as animal manure or compost
  • Growing nitrogen-fixing crops such as peas or clover
  • Rotating crops to maintain soil fertility
  • Avoiding chemical pesticides by weeding
  • Varying seed planting times to discourage pests
34
Q

Advantages of organic farming.

A
  • Food crops and environment aren’t damaged by artificial fertilisers and pesticides
  • Soil erosion is limited, and fertility is maintained through the use of organic fertilisers
  • Biodiversity is promoted because hedgerow and other habitats are conserves
  • Livestock have space to roam
35
Q

Disadvantages of organic farming

A
  • It’s less efficient because some crops are lost to pests and diseases
  • Organic fertilisers take time to rot and they don’t supply a specific balance of materials
  • It is expensive
  • More space is needed
36
Q

What are vascular bundles?

A

• The xylem and phloem form a continuous system of tubes from roots to leaves

37
Q

What does the xylem do? How are they adapted to do this?

A
  • Transports water and soluble mineral salts from the roots to the leaves (transpiration)
  • Xylem vessels are made from dead plant cells. They have a hollow lumen.
  • The cellulose cell walls are thickened with a waterproof substances

Biology 4•5•6 (3 decks)

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