Cellular and Photosynthesis Respiration

Question 1

Glycolysis

Answer 1

Takes place in cytoplasm (cytosol)
converts c6h12o6 -> 2 pyruvate
Produces 2 ATP and 2 NADH
Occurs in 10 steps: first 5 require ATP (energy‐investing rxns); second 5 yield NADH and ATP (energy‐harvesting rxns)

Question 2

Fermentation

Answer 2

Alcoholic - produces 2 CO2, 2 ethanol, and 2 ATP
electron acceptor - pyruvate
Lactic acid - produces 2 lactate and 2 ATP
electron acceptor - pyruvate

Question 3

Pyruvate oxidation

Answer 3

Takes place in the mitochondrial matrix produces acetate, 4 CO2, and 2 NADH acetate + coenzyme A = 2 acetyl CoA produced, Exergonic; one NAD+ is reduced to NADH per pyruvate

Question 4

Citric acid cycle

Answer 4

The 2 Acetyl CoA enters along with2 ADP + Pi, 6 NAD+, 2 FAD, which ends up producing 4 CO2, 2 ATP, 2 FADH2, and 6 NADH
- Acetyl CoA combines with a 4‐carbon molecule (oxaloacetate), yielding: citrate
- Citrate is then rearranged and oxidized
‐Yield: 3 NADH, 1 FADH2 , and 1 ATP per turn
- The original four‐carbon molecule is re‐created, and the cycle starts anew

Question 5

Electron transport chain

Answer 5

electrons from NADH and FADH2 pass through respiratory chain of membrane‐associated carriers -> donating electrons to ETC, which is used to produce many ATP (28)
- Electron flow results in a proton concentration gradient across the inner mitochondrial membrane

Question 6

Oxidative phosphorylation

Answer 6

ATP is synthesized by reoxidation of
electron carriers in the presence of O2, 2 stages are electron transport and chemiosmosis

Question 7

Chemiosmosis

Answer 7

protons flow back across the membrane through a channel protein, ATP synthase, which couples the diffusion with ATP synthesis, electron carriers gain free energy when they become reduced, release free energy when they’re oxidized

Question 8

PE of the ETC, where do electrons come from, what are the electrons used for, importance of proton/H + gradient

Answer 8

As electrons travel through the transport chain, carrier molecules use the potential energy of the electrons to transport hydrogen ions into the intermembrane
compartment

Question 9

Proton motive force

Answer 9

force generated across a membrane
having two components – a chemical potential (difference in [proton]) plus an electric potential due to the electrostatic charge on the proton

Question 10

Final electron acceptor

Answer 10

At the end of the transport chain, electrons are donated to an oxygen atom, which combines with hydrogens to form water, if oxygen isn’t present, electrons can’t be donated, and everything gets “backed up” NAD+ and FAD can’t be produced

Question 11

Why are pyruvate oxidation and the Krebs Cycle considered aerobic?

Answer 11

NAD+ is needed to convert pyruvate -> acetyl CoA, along with FAD for the CAC, and NAD+ and FAD are formed when they donate electrons to O2 during the ETC

Question 12

3 ways to regulate metabolic pathways

Answer 12

• Change amount of active
  enzyme by regulating gene
  expression
• Change enzyme activity by
  covalent modifications (e.g.,
  phosphorylation)
• Feedback inhibition by allosteric
  enzymes

Question 13

Light

Answer 13

a form of energy

Question 14

Electromagnetic radiation

Answer 14

propagated as waves and as particles

Question 15

Photons

Answer 15

packets of energy, specifically particles of light

Question 16

What does absorbed energy do?

Answer 16

Be absorbed, adding energy to the molecule (excited state), absorbed energy boosts an electron in the molecule into a shell farther from the nucleus, electron is held less firmly, making the molecule more unstable and reactive

Question 17

What do pigments do with the sun’s light?

Answer 17

molecules that absorb specific wavelengths in the visible range, other wavelengths are either scattered or transmitted

Question 18

Absorbed vs. reflected wavelengths

Answer 18

Absorption spectrum: plot of wavelengths
absorbed by a pigment, absorption is when light is “soaked up” by a material, while reflection is when light “bounces back” from a surface

Question 19

Which wavelength is never absorbed

Answer 19

No pigment absorbs green light, so green light is reflected ‐ why we perceive leaves to be green

Question 20

Photosynthesis

Answer 20

energy from sunlight is captured and used to convert CO2 to more complex carbon compounds, important for providing the foundation for almost all life

Question 21

Stomata

Answer 21

pores on leaf surface where CO2 enters and O2 and H2O exit

Question 22

Photosynthesis reaction formula

Answer 22

6CO2 + 6H2O -> C6H12O6 + 6O2

Question 23

Two Pathways of Photosynthesis

Answer 23

the light-dependent reactions (also called light reactions) and the Calvin cycle (also called light-independent reactions)

Question 24

Inputs and outputs of light reactions

Answer 24

The light reactions occur in the thylakoids and require water and light, take place in the thylakoid membranes of the chloroplast
- ATP and NADPH are produced
- Oxygen gas (O2) is a by‐ product

Question 25

Inputs and outputs of the Calvin cycle

Answer 25

This stage utilizes the ATP and NADPH generated in the light reactions to fix carbon dioxide from the atmosphere into glucose, a simple sugar, occurs in the stroma of the chloroplast

Question 26

Photosystems

Answer 26

functional units of photosynthesis, Light energy is captured in light‐harvesting complexes and transferred to reaction centers

Question 27

In which pathway are the photosystems used

Answer 27

light-dependent reactions pathway of photosynthesis, specifically within the thylakoid membranes of chloroplasts where they capture light energy and initiate the electron transport chain to generate ATP and NADPH

Question 28

Explain light‐harvesting complexes and reaction center

Answer 28

Light energy is captured in light‐harvesting complexes and transferred to reaction centers, The chlorophyll molecules of the reaction center participate in redox reactions and convert light energy to chemical energy, Chlorophyll a and accessory pigments are arranged in light‐harvesting complexes, or antenna systems

Question 29

What is light energy converted to and what is the final electron acceptor

Answer 29

In the reaction center, light energy is converted to chemical energy, The final electron acceptor is NADP +, which gets reduced: NADP+ + H+ + 2e -> NADPH

Question 30

What photosystems are used in noncyclic electron transport and what does it produce

Answer 30

uses two photosystems to produce ATP and NADPH:
- Photosystem I
- Photosystem II

Question 31

What photosystems are used in cyclic electron transport and what does it produce

Answer 31

uses photosystem I and electron transport to produce ATP instead of NADPH
- The electron from the excited chlorophyll passes back to the same chlorophyll

Question 32

Photosystem II

Answer 32

when an excited chlorophyll (Chl*) gives up its electron, it is unstable and grabs another electron from water
- The water becomes oxidized
- H+ from H2O and electron transport capture energy for the chemiosmotic synthesis of ATP

Question 33

Photosystem I

Answer 33

an excited electron from Chl* reduces an acceptor, only this step makes ATP
- The oxidized Chl + takes an electron from the last carrier in photosystem II
- The energetic e‐ is passed through several carriers and reduces NADP + to NADPH

Question 34

How is ATP formed during the light‐dependent reactions

Answer 34

In a process called non-cyclic photophosphorylation (the “standard” form of the light-dependent reactions), electrons are removed from water and passed through PSII and PSI before ending up in NADPH. This process requires light to be absorbed twice, once in each photosystem, and it makes ATP

Question 35

Importance of ATP synthase

Answer 35

ATP synthase is important because it produces the majority of the body’s ATP, which is a vital energy source for many cellular functions, its function is to synthesize ATP from ADP and inorganic phosphate (Pi) in the F1 sector

Question 36

Calvin cycle

Answer 36

stimulated by light, CO2 is reduced to carbohydrates, energy in ATP and NADPH
from light rxns is used to reduce CO2, occurs in the stroma, rubisco is the enzyme involved in this reaction

Question 37

For every turn of the Calvin cycle

Answer 37

• One CO2 is fixed
• One RuBP is regenerated

Question 38

Photorespiration

Answer 38

RuBP reacts with O2 (instead of CO2)
- “respiration” because it consumes O2
and releases CO2
- “photo” because it occurs only in the
light

Question 39

How do C4 and CAM plants avoid photorespiration

Answer 39

In CAM plants, they open their stomata at night and incorporate CO2 into organic acids, in C4 photosynthesis, light reactions and carbon reactions

Question 40

Examples of energy losses in photosynthesis

Answer 40

Massive losses in light absorption, transmission, reflection, and scattering, as well as losses of absorbed photon energy as heat