DAT bio Chapter 4. Photosynthesis

Question 1

epidermis

Answer 1

outer layer of cells that provides

protection and prevents water loss.

Question 2

Palisade mesophyll cells

Answer 2

• located right below
  upper epidermis, has many chloroplasts; this is
  where most photosynthesis occurs.

Question 3

Spongy mesophyll cells -

Answer 3

• found at the bottom of
  the leaf, where the leaf has a lot of spaces for gas
  movement; has some chloroplasts for moderate
  amounts of photosynthesis.

Question 4

stomata

Answer 4

• pores on underside of leaf where gas

can enter and exit.

Question 5

guard cells

Answer 5

• surround stomata and control their

opening/closing.

Question 6

chloroplasts

Answer 6

are organelles found in plants and
photosynthetic algae, but not in cyanobacteria.
They are similar to mitochondria and contain the
structures listed below (outermost to innermost).

Question 7

can you find cholorplast in cyanobacteria?

Answer 7

no

Question 8

where does the light dependent reaction take place?

Answer 8

thylakoid membrane

Question 9

What is the function of light dependent reaction?

Answer 9

harness light energy to produce ATP and NADPH

Question 10

ATP generated in the light dependent reaction is not used to power the cell, it is consumed in the Calvin cycle T/F

Answer 10

True

Question 11

What special pigments does photosystems contain?

Answer 11

chlorophyll and carotenoids, that absorb photons.

Question 12

What is the reaction center?

Answer 12

special pair of chlorophyll

molecules in the center of these proteins (photosystems)

Question 13

2 types of photosystems

Answer 13

Photosystem 2 (P680) and photosystem 1 (P700)

Question 14

The first of photosynthesis

Answer 14

Non-cyclic photophosphorylation. carried out by the light dependent reactions.

Question 15

Non-cyclic photophosphorylation (carried out light dependent reaction
STEP 1

Answer 15

Water is split (photolysis), passing electrons
to photosystem II and releasing protons into the
thylakoid lumen.

Question 16

Non-cyclic photophosphorylation (carried out light dependent reaction
STEP 2

Answer 16

Photons excite electrons in the reaction
center of photosystem II, passing the
electrons to a primary electron acceptor.

Question 17

Non-cyclic photophosphorylation (carried out light dependent reaction
STEP 3

Answer 17

The primary electron acceptor sends the
excited electrons to the electron transport
chain (ETC). During the redox reactions within
the ETC, protons are pumped from the stroma
to the thylakoid lumen. The electrons are
then deposited into photosystem I.

Question 18

Non-cyclic photophosphorylation (carried out light dependent reaction
STEP 4

Answer 18

Photons excite pigments in photosystem I,
energizing the electrons in the reaction center
to be passed to another primary electron
acceptor.

Question 19

Non-cyclic photophosphorylation (carried out light dependent reaction
STEP 5

Answer 19

The electrons are sent to a short electron
transport chain that terminates with NADP+
reductase, an enzyme then reduces NADP+
into NADPH using electrons and protons.

Question 20

Non-cyclic photophosphorylation (carried out light dependent reaction
STEP 6

Answer 20

The accumulation of protons in the thylakoid
lumen generates an electrochemical gradient
that is used to produce ATP using an ATP
synthase, as H+ moves from the thylakoid
lumen back into the stroma.

Question 21

when does Cyclic photophosphorylation happen

Answer 21

when
photosystem I passes its electrons back to the
first ETC instead of the second ETC. This causes
more proton pumping and more ATP production,
while no NADPH is generated.

Question 22

Calvin cycle is also known as

Answer 22

light-independent reaction since they do not directly use light energy. But they do rely on light dependent reactions because they need ATP and NADPH made from it/

Question 23

Where does the calvin cycle take place

Answer 23

chloroplast stroma of plant mesophyll cells.

Question 24

What does calvin cycle do?

Answer 24

turns inorganic CO2 (carbon dioxide into organic glucose

Question 25

First step of Calvin cycle

Answer 25

(CARBON FIXATION) carbon dioxide combines with five-carbon ribulose-1,5-bisphosphate (RuBP) to form six-carbon molecules, which quickly break down into three-carbon phosphoglycerates (PGA). This reaction is catalyzed by RuBisCo.

Question 26

What catalyzes the first step of the calvin cycle

Answer 26

catalyzed by RuBisCo.

Question 27

second step of Calvin cycle

Answer 27

(REDUCTION) - PGA is phosphorylated by ATP and subsequently reduced by NADPH to form glyceraldehyde-3-phosphate (G3P).

Question 28

Third step of Calvin cycle

Answer 28

REGENERATION) - Most of the G3P is converted back to RuBP.

Question 29

fourth step of Calvin cycle

Answer 29

Carbohydrate synthesis) | some of the G3P is used to make glucose

Question 30

Another process where RuBisCo causes oxygen to binds to RuBP

Answer 30

photorespiration

Question 31

location of Photorespiration

Answer 31

stroma

Question 32

what does Photorespiration produce?

Answer 32

2 carbon molecule know as phosphoglycerate that is shuttled to peroxisomes and mitochondria for conversion into PGA.

Question 33

Is glucose made in photorespiration

Answer 33

no

Question 34

Another way to think of Photorespiration

Answer 34

wasteful pathway that occurs when the Calvin cycle enzyme rubisco acts on oxygen rather than carbon dioxide. By interfering with photosynthesis in this way, photorespiration may significantly limit the growth rate of some plants.

Question 35

another name for photorespiration

Answer 35

C2 photosynthesis, since two-carbon | phosphoglycolate is produced.

Question 36

What conditions are needed for photorespiration to occur?

Answer 36

hot and dry conditions that closes stomata to minimize water loss. oxygen needs to escape but it cannot so it starts to build up while carbon dioxide is used up. RuBisCo binds oxygen and photorespiration occurs.

Question 37

what is C3 photosynthesis

Answer 37

normal photosynthesis, | where three-carbon PGA is produced.

Question 38

What is C4 photosynthesis

Answer 38

produces four-carbon oxaloacetate; occurs in plants living in hot environments. Carbon dioxide is spatially isolated to prevent photorespiration.

Question 39

Step 1 of C4 photosynthesis

Answer 39

PEP carboxylase fixes CO2 into a three carbon PEP molecule, producing oxaloacetate, which is converted into malate in the mesophyll cell

Question 40

Step 2 of C4 photosynthesis

Answer 40

Malate is transferred to bundle sheath cells, | which have lower concentrations of oxygen.

Question 41

Step 3 of C4 photosynthesis

Answer 41

Malate is decarboxylated to release CO2 , spatially isolating where CO2 is fixed by RuBisCo. The only drawback is that pyruvate is also produced and needs to be shuttled back to mesophyll cells using ATP energy.

Question 42

Step 4 of C4 photosynthesis

Answer 42

Pyruvate is converted back into PEP.

Question 43

What is CAM photosynthesis?

Answer 43

- uses temporal isolation of carbon dioxide to prevent photorespiration in hot environments.

Question 44

CAM photosynthesis Step 1

Answer 44

During the day, stomata are closed to prevent transpiration (evaporation of water from plants).

Question 45

CAM photosynthesis Step 2

Answer 45

During the night, stomata are open to let carbon dioxide in. Just like in C4 photosynthesis, PEP carboxylase fixes CO2 into PEP, producing oxaloacetate and afterwards malate. However, malate is stored in vacuoles instead of being shuttled to bundle sheath cells.

Question 46

CAM photosynthesis Step 3

Answer 46

During the next day, the stomata are closed again and malate is converted back into oxaloacetate, which releases CO2 and PEP. Thus, CO2 accumulates in the leaf for use in the Calvin cycle through temporal isolation.