Cell bio- Photosynthesis

Question 1

what is the ultimate source of metabolic energy in plants and some bacteria?

Answer 1

photosynthesis

Question 2

how many stages are in photosynthesis?

Answer 2

2: 1. light reactions
2. dark reactions

Question 3

light reaction

Answer 3

energy
absorbed from sunlight drives the synthesis of ATP &
NADPH (a coenzyme similar to NADH)

Question 4

dark reactions

Answer 4

ATP
& NADPH drives the synthesis of carbohydrates from
CO2 & H2O

Question 5

T/F: Sunlight is absorbed by photosynthetic pigments, the
most abundant of which are the chlorophylls, in which
electrons are excited to a higher energy state

Answer 5

true

Question 6

what is the arrangment of pigments in chloroplast

Answer 6

photocentric , each contains hundred of pigment molecules.

Question 7

what is the role of each pigment molecules?

Answer 7

acting as antennae to absorb light and transfer energy of excited e to chlorophyl molecules that serves as a reaction center

Question 8

chlorophyll

Answer 8

a reaction center

Question 9

pheophytin

Answer 9

membrane carrier

Question 10

what does pheophytin do ?

Answer 10

High-energy electrons are then transferred to an electron transport chain through a
membrane carrier called Pheophytin, which couples their energy to the synthesis of
ATP & NADPH.

Question 11

what are the proteins involved in photosynthesis?

Answer 11

4 multi-protein complexes in thylakoid membrane of chloroplast:
Photosystem I & II: absorb light and transfer energy to reaction center chlorophylls

Question 12

photosystems I & II

Answer 12

absorb light & transfer energy

Question 13

T/F: in mitochondria electron transfers are coupled to the transfer of protons
into the thylakoid lumen, establishing a proton gradient across the membrane

Answer 13

true

Question 14

what is the most important differences between e transport in chloroplast and mitochondria?

Answer 14

the energy derived from sunlight during photosynthesis is
converted into both ATP & NADPH, the latter of which is required for the conversion
of CO2 into glucose.

Question 15

how does electron transfer through photosystems?

Answer 15

Electrons are transferred sequentially between the 2 photosystems, with
photosystem I (PS I) acting to generate NADPH & photosystem II (PS II) acting to
generate the proton gradient that drives the synthesis of ATP

Question 16

T/F: The pathway of electron flow starts at PS II, where the energy derived from
absorption of photons is used to split H2O molecules to molecular oxygen (O2) &
protons in the thylakoid lumen that starts to establish a proton gradient

Answer 16

true

Question 17

what happens in PSII?

Answer 17

the energy derived from
absorption of photons is used to split H2O molecules to molecular oxygen (O2) &
protons in the thylakoid lumen that starts to establish a proton gradient

Question 18

what are the carriers that high energy electrons can go through?

Answer 18

Plastiquinone (PQ)( lipid soluble)

Question 19

Plastiquinone

Answer 19

carries electrons from photosystem II to the Cytochrome bf complex,
within which electrons are transferred to the peripheral membrane protein
Plastocyanin (PC) & 4 additional protons are pumped into the thylakoid lumen

Question 20

what happens in cytochrome of complex during photosynthesis?

Answer 20

electrons are transferred to the peripheral membrane protein
Plastocyanin (PC) & 4 additional protons are pumped into the thylakoid lumen

Question 21

Plastocyanin

Answer 21

peripheral membrane protein, carries the electrons to PS I, where the absorption of additional photons
raises their energy level

Question 22

PSI

Answer 22

the absorption of additional photons
raises their energy level in this system.
uses these high-energy electrons to reduce NADP+ to NADPH, in which the
electrons are carried through a series to Ferredoxin (Fd)

Question 23

Ferredoxin (Fd)

Answer 23

a small protein on the
outside of the thylakoid membrane that complexes with the enzyme NADP
reductase, which transfers electrons to NADP+ to reduce it into NADPH

Question 24

T/F: The ATP & NADPH generated by PS I & PS II are used in the Calvin cycle to convert
CO2 into glucose

Answer 24

true

Question 25

cyclic electron flow

Answer 25

1. second electron transport pathway 2. the light energy harvested at PS I is used for ATP synthesis rather than generating NADPH. 3. e is transfered to cytochrome bf complex

Question 26

what happens to electrons in cytochrome bf complex?

Answer 26

they are coupled with the establishment of a proton gradient across the thylakoid membrane.

Question 27

T/F: electrons after losing energy with lower energy are returned to PSI by Plastocyanin after establishing H gradient

Answer 27

true

Question 28

T/F: Electron transfer from PS I can thus generate either ATP or NADPH, depending on the metabolic needs of the cell.

Answer 28

true

Question 29

for each pair of electron transported how many protons and atp are yielded?

Answer 29

2 Protons at PS II, 4 are trasferred at Cytochrome bf complex, making 1.5 atp

Question 30

T/F: Cyclic electron flow has a lower yield, corresponding to 1 ATP per pair of electrons from the 4 protons transferred across the membrane at the Cytochrome bf complex

Answer 30

true

Question 31

where does the dark reaction occur?

Answer 31

stroma of chloroplst

Question 32

what happens druing dark reactions?

Answer 32

utilize the ATP & NADPH produced from the light reactions to drive the synthesis of glucose in a series of reactions known as the Calvin cycle

Question 33

how many ATPs are needed for calvin ? how many NADPH ?

Answer 33

18 ATP, & 12 NADPH for each molecule of glucose synthesized

Question 34

T/F: 2 electrons are needed to convert each molecule of NADP+ to NADPH, thus 24 electrons must pass through the electron transport chain, which also generates the 18 ATPs that are required.

Answer 34

true

Question 35

how does each can be obtained? amino acid , glycerol, glucose

Answer 35

amino acid: derived from the breakdown of proteins glycerol: produced from the breakdown of lipids glucose: (gluconeogenesis) usually starts with lactate (produced from anaerobic glycolysis

Question 36

glucogenesis

Answer 36

involves the conversion of pyruvate to glucose (essentially the reverse of glycolysis).

Question 37

T/F: Glucose is synthesized from 2 molecules of pyruvate at a cost of 4 ATP, 2 GTP & 2 NADH.

Answer 37

True

Question 38

how does glucose stored in animals & plants?

Answer 38

glycogen & starch, in the form of polysaccharides

Question 39

T/F: synthesis of polysaccharides requires energy.

Answer 39

true

Question 40

why does the formation of a glycosidic bond must be coupled to an energy-yielding reaction?

Answer 40

the condensation reaction linking 2 sugars together is energetically unfavorable,

Question 41

how to fix the unfavorably energetic condensation reaction?

Answer 41

use of nucleotide sugars as intermediates in the synthesis of polysaccharides

Question 42

what is the nucleotide sugar process?

Answer 42

1. Glucose is first phosphorylated in an ATP-driven reaction to form Glucose-6-Phosphate, which is then converted to Glucose-1- Phosphate. 2. Glucose-1-Phosphate reacts with Uridine Triphosphate (UTP), yielding UDP-Glucose, which is an activated intermediate that donates its glucose residue to a growing polysaccharide chain in an energetically favorable reaction 3. chemical energy in the form of ATP & UTP drives the synthesis of polysaccharides from simple sugars

Question 43

how does lipids made?

Answer 43

series of reactions during which coupled to the expenditure of energy (in the form of ATP) & reducing power (in the form of NADPH)

Question 44

How does fatty acids are synthesized?

Answer 44

by the stepwise addition of 2-C units derived from Acetyl-CoA to a growing chain, with each addition requiring the expenditure of 1 ATP & 2 NADPH

Question 45

where does fattty acid biosynthesis occurs?

Answer 45

in the cytosol of eukaryotic cells, the major product of which is the 16-C fatty acid palmitate

Question 46

T/F: The principal components of cell membranes are then synthesized from fatty acids in the endoplasmic reticulum

Answer 46

True

Question 47

how does organisms perform nitrogen fixation?

Answer 47

Some bacteria can use atmospheric N2 by a process call Nitrogen fixation, in whch N2 is reduced to ammonia (NH3) at the expense of energy in the form of ATP.

Question 48

how does most bacteria, fungi, & plants can use nitrate to perform nitrogen fixation?

Answer 48

most bacteria, fungi & plants can use nitrate (NO3-), which is a common constituent of soil, by reducing it to NH3 via electrons derived from NADH or NADPH

Question 49

how to make organic compound from NH3?

Answer 49

synthesis of the amino acids Glutamate (Glu) & Glutamine (Gln), which are derived from the citric acid cycle intermediate α- Ketoglutarate.

Question 50

how Gln & Glu help with synthesis?

Answer 50

serve as donors of amino groups during the synthesis of the other amino acids, which are also derived from central metabolic pathways including glycolysis & the citric acid cycle

Question 51

where can we get raw material for amino acid synthesis?

Answer 51

raw material for amino acid synthesis is thus obtained from glucose, with the amino acids being synthesized at the cost of both energy (ATP) & reducing power (NDAPH)

Question 52

protein biosynthesis

Answer 52

- Protein polymerization requires energy because peptide bond formation is energetically unfavorable. - Amino acids undergo activation before being utilized in protein synthesis, similar to polysaccharide synthesis. - A gene specifies the unique sequence in which amino acids are assembled into proteins. - The nucleotide sequence of a gene dictates the protein's amino acid sequence through the process of translation with messenger RNA as a template. - Amino acids are first bonded to specific tRNA molecules in an ATP-dependent reaction. - The amino acid is then added to the growing peptide chain's C terminus, expending 2 GTP for each addition.