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Biology Term 1 2017 > Unit 6 > Flashcards

Unit 6 Flashcards

1
Q

What is photosynthesis?

A

Photosynthesis is the process by which plants manufacture carbohydrates from raw materials using energy from light.

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2
Q

What does chlorophyll do?

A

It converts light energy into chemical energy. It absorbs light and uses it to split water molecules into hydrogen and oxygen.

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3
Q

What are chloroplasts?

A

Chloroplasts are small, green organelles present in the cytoplasm of leaf cells.

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4
Q

How are hydrogen and oxygen used after being split by chlorophyll?

A

The oxygen escapes from the leaf and the hydrogen is added to carbon dioxide molecules to form carbohydrates.

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5
Q

How many types of chlorophyll are there?

A

There are four types of chlorophyll.

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6
Q

Can a plant that isn’t green still photsynthesise?

A

Yes, the chlorophyll may be masked by other photosynthetic pigments. For example, red and brown seaweeds.

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7
Q

What happens to the glucose produced by photosynthesis?

A

It is quickly converted into starch. It is then added to starch granules in the chloroplast.

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8
Q

What would happen if the glucose concentration rose in the mesophyll cells?

A

The osmotic balance between the cells.

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9
Q

Why is a glucose quickly built up into starch?

A

So that it doesn’t disturb the osmotic balance. Starch is insoluble so doesn’t alter the osmotic potential of cell contents.

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10
Q

How is starch transported out of plant cells?

A

It is broken down into sucrose which is soluble.

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11
Q

Where is sucrose distributed to to plants?

A

Sucrose is transported to all the parts of a plant which don’t photosynthesise. For example, growing buds, ripening fruits, roots and underground storage organs.

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12
Q

What is starch used for in plants?

A
  1. Respiration.

2. Storage.

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13
Q

How is sugar used for respiration?

A

The sugar is oxidised by respiration to carbon dioxide and water, the energy released is used to drive other chemical reactions.

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14
Q

How is sugar used for storage?

A

Sugar that is not needed for respiration is turned into starch and stored. It may be stored as starch grains in plants roots of stems. It can also be stored in the fruits of some plants, ex. Grapes. Also some plants have special storage organs called tubers.

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15
Q

How do plants synthesise things like cellulose, lipids, proteins, and pigments.

A

These substances are synthesised (built up) from the sugar molecules and other molecules.

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16
Q

How do plants make cellulose?

A

By joining hundreds of glucose molecules together.

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17
Q

How to plants make amino acids?

A

By combining nitrogen with sugar molecules or smaller carbohydrate molecules.

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18
Q

What are amino acids used for in plants?

A

To make the proteins that form the enzymes and the cytoplasm of the cell.

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19
Q

Where do plants obtain nitrogen from?

A

Plants absorb nitrates from the soil through their roots to obtain nitrogen.

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20
Q

How do plants obtain sulfur?

A

They absorb it in the form of sulfates (SO4) from the soil.

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21
Q

How do plants obtain phosphorus?

A

They absorb phosphates (PO4).

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22
Q

What do plants need phosphorus for?

A

Plants need phosphorus for DNA and for reactions involving energy release.

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23
Q

What is magnesium needed for in plants?

A

Chlorophyll requires magnesium in order to function properly.

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24
Q

What are elements that plants need in small quantities called?

A

Trace elements.

25
Q

What does an increase in a plant’s temperature usually do?

A

It should increase the rate at which carbon dioxide is combined with hydrogen to make carbohydrates.

26
Q

What is a limiting factor?

A

A limiting factor is something present in the environment in such short supply that it restricts life processes.

27
Q

In what form are all metallic and non-metallic elements taken into plants as?

A

Ions.

28
Q

What is gaseous exchange?

A

The process by which plants and animals take in or give out gases.

29
Q

What is the compensation point?

A

The compensation point is the point at which the rate of photosynthesis and the rate of respiration are the same. Therefore, there is zero net intake or output of carbon dioxide and oxygen.

30
Q

What attaches a leaf to the plant stem?

A

The leaf stalk.

31
Q

What is the midrib in a leaf?

A

The midrib carries on from the leaf stalk. Veins which deliver water and salts to carry away the food made by leaf cells branch of the midrib.

32
Q

What important function do networks of veins perform?

A

They form a skeleton which supports the leaf.

33
Q

What is the lamina?

A

The lamina is the leaf blade of a leaf.

34
Q

What is the epidermis?

A

The epidermis is single layer of cells on the upper and lower surface of a leaf cell.

35
Q

What is the cuticle?

A

The cuticle is a waterproof and waxy layer which protects a leaf and helps to reduce water loss.

36
Q

What are stomata?

A

Stomata (singular = stoma) are openings which consist of a pair of guard cells which allow the gaseous exchange to take place.

37
Q

Where to the stomata typically occur in dicotyledons?

A

Most dicotyledons have stomata on the lower epidermis.

38
Q

Where do stomata typically occur in monocotyledons?

A

The stomata in monocotyledons typically are evenly distributed across both sides of the leaf.

39
Q

What is the mesophyll?

A

The mesophyll is the tissue between the upper and lower epidermis.

40
Q

What does the mesophyll consist of?

A

The mesophyll consists of two zones, the palisade and spongy mesophyll.

41
Q

What are some characteristics of palisade cells?

A
  1. They are usually vertically long.

2. They usually contain many chloroplasts.

42
Q

What are some characteristics of the spongy mesophyll cells?

A
  1. The cells in the spongy mesophyll vary in shape.

2. There are many spaces between cells.

43
Q

What is the main vein of a leaf called?

A

It is called the midrib.

44
Q

What are vascular bundles?

A

Vascular bundles are veins.

45
Q

What two types of tissues do vascular bundles consist of?

A

Xylem and phloem tissues.

46
Q

What do xylem tissues do?

A

Xylem tissues carry water and salts in a leaf.

47
Q

What do phloem tissues do?

A

Phloem tissues transport food substances like sugars away from the leaf to other parts of the plant.

48
Q

What does the epidermis in a leaf do?

A
  1. It protects the leaf
  2. It helps the leaf to keep it’s shape
  3. The tightly fitting cells help prevent water loss
49
Q

What are magnesium ions needed for?

A

To manufacture chlorophyll.

50
Q

What are nitrate ions needed for?

A

To manufacture proteins.

51
Q

How are plant leaves adapted for photosynthesis?

A
  1. They are broad to maximise sunlight and carbon dioxide that is absorbed.
  2. Leaves are thin so carbon dioxide doesn’t have to diffuse far into the leaf.
  3. Spaces between cells allow for carbon dioxide to easily diffuse through the leaf.
  4. Many chloroplasts.
  5. Many stomata.
  6. Network of veins throughout the entire leaf.
52
Q

What can be five limiting factors on photosynthesis?

A
  1. Light intensity/wavelength
  2. Carbon dioxide concentration
  3. Temperature
  4. Chlorophyll concentration
  5. Stomata (whether they are open or closed)
    Note that if any of these increases, they can only increase up to a point, for example, if light intensity increases it might be limited by the supply of carbon dioxide.
53
Q

How do stomata open and close?

A

Changes in turgor and the shape of guard cells can open or close the stomatal pore.

54
Q

What does the closing of stomata do?

A

If stomata close, the carbon dioxide supply to the leaf is cut off, so photosynthesis stops. It also stops the loss of water vapour.

55
Q

When are stomata open and closed?

A

Usually during daylight plant’s stomata are open and during darkness they are closed.

56
Q

What is chlorosis?

A

Where leaves turn yellow usually from the stem upwards.

57
Q

What are the effects on a plant of a lack of nitrates?

A

A fast growing plant that lacks nitrates will typically show:

  1. Stunted growth
  2. A weak stem
  3. The lower leaves turn yellow and the upper ones turn pale green
58
Q

What are the effects on a plant of a lack of magnesium?

A
  1. The leaves will turn yellow from the stem upwards (this is called chlorosis).

Biology Term 1 2017 (10 decks)

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