Photosynthesis

Question 1

What is photosynthesis?

Answer 1

A complex series of reactions that can be summarized as the following equation:

6 CO2 + 12 H2O + Light energy → C6H12O6 + 6 O2 + 6 H2O

Question 2

Photosynthesis ____ the direction of electron flow compared to ____

Answer 2

reverses ; respiration

Question 3

What type of process is photosynthesis?

Answer 3

A redox process in which H2O is oxidized and CO2 is reduced

Question 4

Is photosynthesis an endergonic process?

Answer 4

Yes, meaning the energy boost is provided by light

Question 5

What is a wavelength?

Answer 5

A measure of the distance between crests of the waves, ranging from less than a nanometer to more than a kilometer

Question 6

Light is what type of energy?

Answer 6

Electromagnetic energy, also called electromagnetic radiation

Question 7

What are pigments?

Answer 7

Substances that absorb visible light

Question 8

What happens to the wavelengths that are absorbed?

Answer 8

They disappear

Question 9

What happens to the wavelengths that are not absorbed?

Answer 9

They are reflected or transmitted

Question 10

The absorption spectrum of chlorophyll a indicated that what colors will work best for photosynthesis and what color is the least effective?

Answer 10

violet-blue and red will work best while green is the least effective

Question 11

What is the action spectrum?

Answer 11

A profile of the relative effectiveness of different wavelengths that confirms the effectiveness of violent-blue and red light

Question 12

How do chlorophyll a and b differ?

Answer 12

CH3: chlorophyll a
CHO: chlorophyll b

Question 13

What happens when a pigment molecule absorbs light?

Answer 13

One of its electrons goes from a ground state to an excited state, which is unstable

Question 14

How do electrons fall back to the ground state?

Answer 14

In isolation, releasing excess energy as heat or light, an afterglow called fluorescence

Question 15

What does a photosystem consist of?

Answer 15

A reaction-center complex surrounded by light-harvesting complexes

Question 16

What is the reaction-center complex?

Answer 16

An association of proteins holding a special pair of chlorophyll a molecules and a primary electron acceptor

Question 17

What is the light-harvesting complex?

Answer 17

Pigment molecules bound to proteins ; transfer energy of photons to the chlorophyll a molecules in the reaction-center complex

Question 18

What are the two types of photosystems in the thylakoid membrane, numbered in order of their discovery

Answer 18

Photosystem II (PS II)
Photosystem I (PS I)

Question 19

In mitochondria, protons are pumped to the ____ and drive ATP synthesis as they diffuse back into ______ ____

Answer 19

Intermembrane space ; mitochondrial matrix

Question 20

In chloroplasts, protons are pumped into the ___ ___ and drive ATP synthesis on the ____ ____ of the membrane as they diffuse back into the ___

Answer 20

Thylakoid space ; stroma side ; stroma

Question 21

Is the Calvin cycle anabolic or catablic?

Answer 21

Anabolic ; it builds sugar from smaller molecules using ATP and the electrons carried by NADPH

Question 22

Where have alternative mechanisms of carbon fixation evolved?

Answer 22

In hot, arid climates

Question 23

Most plants are what?

Answer 23

C3 plants, in which the initial fixation of CO2, via rubisco, forms a three-carbon compound

Question 24

What is photorespiration?

Answer 24

When rubisco binds with O2 instead of CO2, producing a two-carbon compound

Question 25

Why is photorespiration costly?

Answer 25

Because it consumes O2 and organic fuel without producing any ATP or sugar

Question 26

In many plants, photorespiration drains away as much as ___ of the carbon fixed by the Calvin cycle

Answer 26

50%

Question 27

What minimizes the cost of photorespiration?

Answer 27

C4 plants

Question 28

What are some examples of C4 plants?

Answer 28

Sugarcane and corn

Question 29

What do C4 plants do in hot, dry weather?

Answer 29

Partially close their stomata to conserve water but reduce CO2

Question 30

Photosynthesis begins in ___ ___, but is completed in _____ ____

Answer 30

mesophyll cells ; bundle-sheath cells

Question 31

What are bundle-sheath cells?

Answer 31

Cells arranged in tightly packed sheaths around the leaf veins

Question 32

Which photosynthesis uses less water and resources: C4 or C3?

Answer 32

C4 photosynthesis

Question 33

How did scientists genetically modify rice?

Answer 33

Scientists genetically modified rice, a C3 plant, to carry out C4 photosynthesis for an estimated 30-50% increase in yield

Question 34

How is the CAM pathway similiar to the C4 pathway?

Answer 34

They both incorporate CO2 into organic intermediated before it enters the Calvin cycle