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Biology > Chapter 5 - Photosynthesis > Flashcards

Chapter 5 - Photosynthesis Flashcards

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AP® Biology flashcards Biology 101 flashcards
0
Q

Give a general overview of what chlorophyll does.

A

It converts unusable sunlight into usable chemical energy.

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1
Q

What is photosynthesis?

A

It is the process by which plants use the energy from sunlight to produce sugar, which cellular respiration converts into ATP.

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2
Q

What is the overall reaction of photosynthesis?

A

Water + Carbon Dioxide (+ light energy) -> glucose + oxygen.

6H2O + 6CO2 –> C6H12O6 + 6O2

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3
Q

Does gases exchange occur in plants?

A

Yes, since all living plant cells respire all the time, and chloroplasts photosynthesize, it is needed.

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4
Q

Where does gases exchange occur in plants?

A

Mainly in the spongy mesophyll cells in leaves.

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5
Q

Why are leaves ideal for gases exchange?

A

They have a large surface area due to there irregular shape, loosely packed spongy cells which increase it even further.

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6
Q

Where do gases enter from in a leaf?

A

The stomata, usually in the lower surface if the leaf.

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7
Q

What are stomata’s enclosed by?

A

Guard cells which can swell up in order to control water loss.

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8
Q

During the hours of the day, what happens to plants?

A

In the daylight photosynthesis increases, causing the oxygen concentration inside the leaf to rise, whilst the carbon dioxide concentration decreases.

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9
Q

In a cross section of a leaf, we find various layers within it. Mention all 4 layers.

A

Upper Epidermis, Palisade Mesophyll, Spongy Mesophyll and Lower Epidermis.

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10
Q

What do we find in the palisade mesophyll layer?

A

We find densely packed chloroplasts, since it’s been adapted for photosynthesis.

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11
Q

Chloroplasts in the palisade mesophyll layer tend to move around so that equal exposure to light is ensured. What is this process called?

A

Cyclosis.

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12
Q

What is unique in the spongy mesophyll layer? What has it been adapted for?

A

It’s been adapted for gases exchange, since they are loosely packed with large intercellular air spaces where gases can readily diffuse.
(Have fewer chloroplasts that palisade layer so carry out less photosynthesis)

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13
Q

How does the leaf supply water and minerals to the mesophyll cells and carries sugars to other parts?

A

Through a network of veins.

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14
Q

What’s do we find on the leafs epidermises? What is its function?

A

A waxy cuticle, in order to reduce water loss.

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15
Q

How do close leaves usually place one another?

A

They all have a different angled orientation, as to not shade any neighboring leaves.

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16
Q

What do the mitochondria and the chloroplasts have in common?

A

They both have a double membrane.

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17
Q

Chloroplasts have a 3 membrane. What are the 3 membranes called?

A

Outer membrane, inner membrane and thylakoids membrane.

18
Q

What’s unique about the the thylakoid membrane?

A

It’s folded into thin vesicles called thylakoid lumen. Which are usually stacked into stacks called grana.

19
Q

What can we find in the thylakoid membrane?

A

ATP synthase particles, same as the mitochondria.

20
Q

What do chloroplasts store?

A

DNA, tRNA, ribosomes, and the products of photosynthesis.

21
Q

Chloroplasts contain 2 different kinds of chlorophyll. Name them.

A

Chlorophyll a & Chlorophyll b

22
Q

Along with chlorophyll a and chlorophyll b, there are other light-absorbing pigments. Mention two.

A

2 accessory pigments would be carotenoids and luteins.

23
Q

How are chlorophyll a & b different from one another?

A

They absorb light at different wavelengths. Which is useful since having different pigments allows more of the visible spectrum to be used.

24
Q

What does a low absorption rate indicate?

A

The wavelengths are not absorbed and used, but stead are reflected or transmitted.

25
Q

Different species of plant have different combinations of photosynthetic pigments. This causes what exactly?

A

Differentiation in leaf colour.

26
Q

Plants with higher concentrations of chlorophyll due to shady condition are usually what colour?

A

Dark green.

27
Q

Whereas plants which have been adapted to bright conditions are usually what colour?

A

Pale green.

28
Q

How do we obtain an action spectrum?

A

By measuring the rate of photosynthesis using different wavelengths of light.

29
Q

What is a photosystem?

A

Chlorophyll and other pigments are arranged in complexes with proteins.

30
Q

How many chlorophyll molecules are found in each photosystem?

A

200, along with 50 accessory pigments, proteins and lipids.

31
Q

Where are these photosystems located?

A

In the thylakoid membranes.

32
Q

The chloroplast of green plants have 2 kinds of photosystems. Name them.

A

Photosystems 1 and photosystems 2. They absorb light at different wavelengths and have different jobs in light dependent reactions.

33
Q

2 main reactions occur in chloroplasts. Name them.

A

Light Dependent reactions and Light Independent reactions.

34
Q

What product does light dependent reactions make?

A

Energy.

35
Q

What product does light independent reactions make?

A

Glucose

36
Q

What happens in light-dependent reactions?

A

Light energy is used to split water and make ATP and hydrogen atoms.

37
Q

Where does light-dependent reaction take place?

A

Thylakoid membrane of chloroplasts.

38
Q

What does light-independent reactions need? (Carbon fixing reactions)

A

They don’t need light, however they do need the products of light-dependent stage (ATP and H)

39
Q

Where does light-independent reactions take place?

A

In the stroma of the chloroplasts.

40
Q

What external factors affect the rate of photosynthesis?

A

Light intensity, carbon dioxide concentration and temperature.

41
Q

How does light intensity affect photosynthesis?

A

Very high light intensity may bleach chlorophyll, slowing down photosynthesis.

Plants in this situation usually adapt by having thick cuticles or hairy leaves.

42
Q

How does carbon dioxide concentration affect photosynthesis?

A

This is the major limiting factor, since photosynthesis cannot occur without CO2.

The short term optimum is 0.05% but long term it’s about 0.1%

43
Q

How does temperature affect photosynthesis?

A

Since light independent reactions and to certain extent even light dependent reactions are enzyme controlled and therefore temperature sensitive.

Optimum is about 25C

Biology (10 decks)

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