Metabolism

Question 1

What are mitochondria?

Answer 1

Mitochondria are vital organelles specialized in the production of large quantities of ATP and are only found in eukaryotic (animal) cells.

Question 2

What is the structure of mitochondria?

Answer 2

Mitochondria have an outer membrane and an inner matrix where various metabolic processes occur, including glycolysis outside the cell and pyruvate oxidation, Krebs cycle, and oxidative phosphorylation inside the matrix.

Question 3

What is the fluid mosaic model of the cell membrane?

Answer 3

The fluid mosaic model describes the structure of the cell membrane as a phospholipid bilayer with embedded proteins, cholesterol, and carbohydrate chains, allowing selective permeability and cell signaling.

Question 4

What are the functions of the cell membrane?

Answer 4

The cell membrane functions in selective permeability, signal transduction, cell recognition, and providing structural support.

Question 5

What is the difference between polar and non-polar molecules?

Answer 5

Polar molecules have an uneven distribution of charges and are typically hydrophilic, while non-polar molecules have an even distribution of charges and are typically hydrophobic.

Question 6

What is passive transport?

Answer 6

Passive transport is the movement of molecules across the membrane without energy input, moving down their concentration gradient.

Question 7

What is active transport?

Answer 7

Active transport is the movement of molecules across the membrane with energy input (ATP), moving against their concentration gradient.

Question 8

What is glycolysis?

Answer 8

Glycolysis is the first step of cellular respiration occurring in the cytoplasm, converting glucose into 2 pyruvates, 2 ATP, and 2 NADH without requiring oxygen.

Question 9

What are the stages of aerobic cellular respiration?

Answer 9

The four stages of aerobic cellular respiration are glycolysis, pyruvate oxidation, Krebs cycle, and the electron transport chain (ETC).

Question 10

What is the role of NADH and FADH2 in cellular respiration?

Answer 10

NADH and FADH2 act as electron carriers, delivering high-energy electrons to the electron transport chain, contributing to ATP production.

Question 11

What is fermentation?

Answer 11

Fermentation is an anaerobic process that allows organisms to produce energy without oxygen, resulting in products like ethanol or lactic acid.

Question 12

What are the light-dependent reactions of photosynthesis?

Answer 12

Light-dependent reactions occur in the thylakoid membrane of chloroplasts, converting light energy into ATP and NADPH while releasing oxygen.

Question 13

What are the light-independent reactions (Calvin cycle)?

Answer 13

The Calvin cycle takes place in the stroma of chloroplasts, using ATP and NADPH to convert CO2 into glucose.

Question 14

What is the electromagnetic spectrum’s role in photosynthesis?

Answer 14

The electromagnetic spectrum provides light energy for photosynthesis, with chlorophyll absorbing primarily red and blue wavelengths.

Question 15

What is the purpose of the chemiosmotic model in ATP synthesis?

Answer 15

The chemiosmotic model explains ATP synthesis via ATP synthase, where a proton gradient created by the electron transport chain drives the conversion of ADP to ATP.

Question 16

What is the role of electron carriers in the membrane?

Answer 16

Electron carriers cause a negative charge in the membrane.

Question 17

What happens during photolysis?

Answer 17

Water molecules are split to produce electrons and oxygen, replenishing lost electrons in the ETC.

2H2O → 4e- + 4H+ + O2

Question 18

How does water reach the thylakoid lumen?

Answer 18

Water is taken from the roots through the vascular bundles (Xylem) into the thylakoid lumen.

Question 19

What is the significance of water for plants?

Answer 19

Water is essential for replenishing electrons in PSII; without it, the reaction cannot occur.

Question 20

What occurs in the electron transport chain (ETC)?

Answer 20

High-energy electrons travel through the ETC, releasing energy as they move between protein complexes.

Question 21

What is the role of plastoquinone (PQ) in the ETC?

Answer 21

PQ accepts excited electrons from PSII and takes a H+ ion from the stroma to drop it into the thylakoid lumen.

Question 22

What happens to electrons after they are passed to plastocyanin (PC)?

Answer 22

Electrons go from PC to PSI.

Question 23

What is the function of NADP synthase at PSI?

Answer 23

NADP is converted to NADPH using low-energy electrons and a hydrogen from the stroma.

Question 24

How is ATP produced in the light reactions?

Answer 24

H+ ions diffuse through ATP synthase, facilitating the conversion of ADP and Pi into ATP.

Question 25

What are the inputs and outputs of the Calvin Cycle?

Answer 25

Inputs: 6CO2, 18 ATP, 12 NADPH; Outputs: 1 glucose (C6H12O6), 18 ADP, 12 NADP+.

Question 26

What occurs during carbon fixation in the Calvin Cycle?

Answer 26

CO2 binds with RuBP, forming an unstable 6C compound that splits into 2 PGA.

Question 27

What happens in the reduction phase of the Calvin Cycle?

Answer 27

3-PGA is converted into G3P using ATP and NADPH from light-dependent reactions.

Question 28

How is RuBP regenerated in the Calvin Cycle?

Answer 28

5 G3P are recycled to regenerate RuBP using ATP.

Question 29

What are the features of non-cyclic photophosphorylation?

Answer 29

Involves PSII and PSI, linear electron pathway, produces ATP and NADPH, and includes water splitting.

Question 30

What are the features of cyclic photophosphorylation?

Answer 30

Involves PSI only, circular electron pathway, produces ATP but not NADPH, and does not involve water splitting.

Question 31

What is the chemiosmotic model of ATP production?

Answer 31

It explains how the flow of protons across a membrane drives ATP synthesis during light reactions.

Question 32

What is the role and location of NADPH?

Answer 32

NADPH supplies high-energy electrons for reducing 3-PGA to G3P in the Calvin cycle, located in the stroma.

Question 33

What factors affect NADPH?

Answer 33

Light intensity, electron transport efficiency, water availability, and Calvin cycle rate.

Question 34

What is the role and location of RuBP?

Answer 34

RuBP accepts CO₂ in the Calvin cycle and forms 3-PGA with RuBisCO, located in the stroma.

Question 35

What factors affect RuBP?

Answer 35

ATP/NADPH availability, RuBisCO activity, CO₂ levels, and temperature.

Question 36

How do C3 and C4 plants differ?

Answer 36

C3 plants use 3-phosphoglycerate for carbon fixation, while C4 plants use oxaloacetate, enhancing efficiency in hot, arid conditions.

Question 37

What are key characteristics of C3 plants?

Answer 37

Common in cooler climates, directly take CO₂ from the atmosphere, less efficient under stress.

Question 38

What are key characteristics of C4 plants?

Answer 38

More efficient in water use, favored in high temperature and light conditions, use an additional step before the Calvin cycle.

Question 39

What is photorespiration?

Answer 39

Occurs when CO2 levels are low, leading Rubisco to combine O2 with RuBP instead of CO2, producing less PGA and a toxic molecule.