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Biology 130 > Chapter 7 > Flashcards

Chapter 7 Flashcards

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1
Q

Why is photosynthesis important to all living things?

A

during photosynthesis, plants regulate CO2 and produce oxygen which we use to survive.

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2
Q

Where within a leaf does photosynthesis occur? Be very specific!

A

chloroplasts found in the mesophyll layer

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3
Q

What is/are the role(s) of stomata, chloroplasts and mesophyll with regards to photosynthesis?

A

stomata- control the flow of CO2 and oxygen in and out of leaves

chloroplasts- site of photosynthesis, contains grana and stoma

mesophyll- mesophyll cells are large spaces within the leaf that allow carbon dioxide to move freely, carbon-fixation pathway also begins in the mesophyll cells

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4
Q

What is a Chloroplast composed of? List the different parts of a chloroplast and describe the function of each.

A

chloroplasts are composed of an inner , inter membrane, and outer membrane, grana (with a thylakoid space and membrane), and the stroma

grana (stack of thylakoids)- membranous discs, containing photosynthetic pigments, the pigments absorb solar energy, where light-dependent reactions occur

stroma- semifluid interior of chloroplasts, CO2 is enzymatically reduced to a carbohydrate, site of calvin cycle

inner, inter membrane, outer membrane- encloses the stroma, the outer membrane is permeable to small organic molecules, whereas the inner membrane is less permeable and has many transport proteins

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5
Q

Where within a chloroplast is chlorophyll found? Energy absorbed? Reduction of CO2 occur?

A

chlorophyll- thylakoid membrance

energy absorbed- thylakoid membrane, chlorophyll absorbs light energy

reduction of CO2- stroma

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6
Q

Which part of the solar spectrum of light is actually used in photosynthesis?

A

mainly red and blue, rarely green, reflects green

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7
Q

What is a pigment? How do they influence the color of a structure? Why are they important in photosynthesis?

A

pigments absorb wavelengths of light
they reflect the ones they don’t absorb
they influence color by the light they reflect
they help absorb energy from light

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8
Q

Which colors of visible light have the highest energy? Longest wavelength?

A

blue light has the highest energy and smallest wavelength
red light has the lowest energy and largest wavelength

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9
Q

What are the three main pigments found in chloroplasts? Which colors of visible light are each most sensitive to?

A

chlorophyll- sensitive to red-blue light

carotenoids- sensitive to blue light

phycobilin- sensitive to green-red light

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10
Q

How do carotenoids differ from chlorophyll?

A

carotenoids reflect shades of yellow and orange wavelengths while chlorophyll reflects shades of green wavelengths

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11
Q

Give the balanced equation for photosynthesis. Indicate which part is reduction and which part is oxidation.

A

6CO2 + 6H2O -> C6H12O6 + 6O2

6CO2 -> C6H12O6: reduction

6H2O -> 6O2: oxidation

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12
Q

What are the two types of reactions of photosynthesis?

A

light dependent- needs light

light independent or calvin cycle- doesn’t need light

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13
Q

In one sentence explain the function of the light dependent reaction.

A

It utilizes light energy from the sun to create chemical energy (ATP, NADH)

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14
Q

In one sentence explain the function of the light independent reaction known as the Calvin Cycle.

A

enzymatic reactions that occur during photosynthesis and carbon fixation to convert CO2 into glucose in the stroma

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15
Q

Where does the light reaction occur in a cell? Be specific!

A

thylakoid membrane

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16
Q

What are the two types of light reactions? How do they differ?

A

the light reaction and light independent reaction

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17
Q

What is a photosystem? How many different kinds of photosystems are there?

A

a photosystem consists of a pigment complex and electron acceptor molecules within the thylakoid membrane. the pigment complex serves as an “antenna” for gathering solar energy

there are two photosystems, PS II and PS I

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18
Q

Define: Reaction Center

A

they’re complexes of pigment and protein that convert the electromagnetic energy of sunlight into chemical potential energy.

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19
Q

Define: Electron Transport System

A

as electrons move down the chain, which consists of proteins in the cell membrane, energy is released and captured to produce ATP molecules.

energized electrons are taken up by NADP+, which is reduced and becomes NADPH

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20
Q

Define: Photophosphorylation

A

the conversion of ADP to ATP using the energy of sunlight by activation of PSII

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21
Q

In which part of photosynthesis does Photophosphorylation occur?

A

thylakoid membranes

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22
Q

Define the term Chemiosmosis. Be prepared to explain how chemiosmosis works.

A

the process of diffusion of ions (usually H+ ions, also known as protons) across a selectively permeable membrane, synthesizes ATP

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23
Q

What is the function of water in Photosystem II? Why doesn’t Photosystem I require the oxidation of water?

A

a hydrolysis reaction occurs in the thylakoid membrane which oxidizes water and provides the electron that’s used for PS II

PS I doesn’t require that because the electron is transported from PS II to PS I through electron transport

24
Q

Explain how O2 is produced as a product of photosynthesis? Where does the O2 come from?

A

O2 comes from the splitting of water molecules (hydrolysis) by photosystem 2

25
Q

Why will a plant die if it is not watered?

A

water is needed to be broken down in photosystem 2 so that photosynthesis can occur

26
Q

Where in a cell does Photosystem I occur? Where in a cell does Photosystem II occur? Be very specific!

A

thylakoid membrane

27
Q

Why are H+ actively transported into the Thylakoid Space during the light reactions of photosynthesis? Where does the energy come from that is necessary for active transport of H+?

A

H+ is transported for making ATP, energy from electrons pumps hydrogen ions against their concentration gradient from the stroma into the thylakoid space.

28
Q

What are the products produced by Photosystem I and Photosystem II? How will they be used by the cell?

A

products of photosystem 2: O2
products of photosystem 1: ATP, NADPH

ATP and NADPH are used in the calvin cycle and O2 is released in the atmosphere

29
Q

How is ATP produced during the light dependent reactions of photosynthesis?

A

through ATP synthase where an enzyme converts H+ and ADP to ATP

30
Q

Why does the cell produce NADPH during the light dependent reactions of photosynthesis?

A

so it can be used to in the light independent reaction (NADPH transfers electrons to 3PG) the energy they store is used to power the light independent reactions

31
Q

Why is energy captured during the light dependent reactions stored in the form of a H+ gradient?

A

because it is then used for ATP synthase

32
Q

How is a H+ gradient used to manufacture ATP?

A

proton pumping during the electron transport chain is used to synthesize ATP

33
Q

Why are the Light Dependent Reactions needed in order for the Light Independent Reactions to occur?

A

the light independent reaction uses the products (NADPH and ATP) of the light dependent reaction

34
Q

What are the three parts of the Calvin cycle?

A

carbon fixation, carbon reduction, and RuBP regeneration

35
Q

Does the Calvin cycle require light?

A

no

36
Q

Explain: Carbon Fixation

A

the process of attaching an inorganic carbon to an organic compound, It involves the enzyme RuBP ‘‘fixing’’ CO2 to RuBP, producing two molecules of 3PG

37
Q

Explain: Carbon Reduction

A

adds electrons and hydrogens to the cycle (3PG + e- + H+ -> G3P), the electrons come from ATP to ADP + P reaction and the hydrogen ions come from NADPH to NADP+ reaction

the 3PG molecules created through carbon fixation are converted into molecules of simple sugar – glucose (must happen twice)

38
Q

Explain: Generation of RuBP

A

complex process that requires ATP, some of the G3P molecules are used to produce glucose, while others are recycled to regenerate the RuBP acceptor

39
Q

How many carbons are found in RuBP? Why is this significant?

A

5 carbons, it will bond with CO2 to form an unstable six carbon molecule which makes a glucose molecule

40
Q

How does the Calvin cycle manufacture 3PG? How many carbons are found in 3PG? Why is this significant?

A

manufactures 3PG by fixing CO2 to RUBP causing it to become unstable splitting it into 3PG. 3 carbons. significant because they then can be converted into glucose molecules

41
Q

When a cell converts 3PG to G3P is this an example of reduction or oxidation?

A

reduction

42
Q

Which is a higher energy molecule 3PG or G3P? Where does the extra energy come from?

A

G3P is the higher energy molecule, extra energy comes from the electron produced from the NADPH to NADP+ reaction

43
Q

Where within the Calvin cycle is G3P manufactured? How many carbons are found in G3P? Is G3P considered a carbohydrate?

A

made in the reduction part of the cycle, 3 carbon, it is a sugar

44
Q

Why is it necessary for a cell to make RuBP? Where does this occur in a cell?

A

RuBP is used to make 3PG which is necessary for the production of glucose, occurs in the stroma

45
Q

How many G3P does it take to make all of the RuBP used in two turns of the Calvin Cycle? Why is this significant?

A

10 G3P, it is the amount needed to restart the cycle

46
Q

Why do photosynthetic organisms make G3P (What do they use it for?)

A

G3P can be used to make anything, here it is used to make glucose

47
Q

Describe the differences between C3, C4, and CAM plants.

A

C3- most photosynthetic plants, best in cool and moist environments

C4- uses a 4 carbon molecule, photorespiration doesn’t occur

CAM- special variation of C4, capable in extreme desert conditions

48
Q

What is photorespiration? Why is it a problem? Under what conditions does it occur?

A

RuBP combines with O2 instead of CO2, oxygen is taken up and only CO2 is released, occurs when stoma is closed

49
Q

In what kind of plants does photorespiration occur?

A

C3 plants, wheat, rice, oats, cat grass

50
Q

What adaptations do some plants have that solves the photorespiration problem?

A

C4 photosynthesis, even when stoma is closed CO2 is delivered to the calvin cycle

51
Q

Give an example of a C3, C4, and CAM plant.

A

C3- wheat, rice, oats

C4- sugarcane, corn, bermuda grass

CAM- pineapple, cactus

52
Q

How does a C3 and C4 plant differ with regards to the Calvin cycle?

A

the C3 plant produces a 3 carbon compound while a C4 plant produces a 4 carbon compound

53
Q

Why do C4 plants NOT experience photorespiration?

A

C4 plants fix CO2 to PEPCase even when the stoma is closed during hot and dry conditions, while oxygen cannot go through

54
Q

Why are C4 plants called C4? Why are C3 plants called C3?

A

C4 plants aim to produce a 4 carbon compound while C3 plants aim to produce a 3 carbon compound

55
Q

How do CAM plants differ from C3 and C4 plants with regards to photosynthesis? Why is this advantageous?

A

CAM divides with the use of time, during the night, CAM plants use PEPCase to fix some CO2, forming C4 molecules, which are stored in vacuoles in the mesophyll cells

during the day, C4 molecules release CO2 to the calvin cycle when NADPH and ATP are available from the light reactions.

it’s advantageous because they can conserve water

Biology 130 (3 decks)

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