chapters 7 and 8

Question 1

cellular respiration (summary)

Answer 1

catabolic pathway that yields energy,potential energy of a molecule is according to its structure
. anaerobic- no oxygen-(fermentation, and anearobic respiration)
aerobic respiration- oxygen is used, regular cellular respiration, usually uses glucose but other energy sources like lipids, proteins,and carbohydrates also are used
C6H12O6+ 6O2 -> 6H2O + 6CO2
O2 is used and bonds with hydrogen and electrons to produce water (this is in the etc). carbon dioxide is given off by the krebs cycle pyruvate is broken down, which is from glycolysis.
glucose and the citric acid use substrate level phosphorylation , the etc and chemiosmosis use oxidative phosphorylation.
each step of the reaction produces energy

Question 2

redox reactions and electron carriers

Answer 2

oxidation and reduction reactions, are when a electron is passed through a series of molecule, the molecule that accepts the electron is reduced and the previous is oxidized. (not all redox rx are exactly like this some don’t have a complete transfer of electrons some just change the sharing of electrons in covalent bonds)
redox reactions are electron transfer- electron transport chain is a string of redox reactions which is used to synthesize atp
-energy must be added to pull and electron from a molecule, the more electronegative the molecule the more energy required to remove it.
-electrons lose potential energy as they are transferred along an electron transport chain which allows sustainable energy to be gained from this, rather than one large release of energy that a cell could not harness, this is why electrons are stripped from glucose in steps.

electron carries include; nad+ and fad, which are oxidizing agents as they accept electrons and become reduced.
dehydrogenase- removes hydrogen and an electron and delivers then to an electron carrier
nadh- most versatile electron carrier, electron loses very little energy when transferred to nadh

Question 3

electron transport chain

Answer 3

proteins build into inner membrane of the mitochondria, nadh drops off electrons at the top of the chain , oxygen accepts electrons at the bottom.
exergonic, electrons move down- carrier molecules become more electronegative because they must be able to oxidize carrier molecule molecule before that, electrons fall down gradient oxygen. (oxygen pulls electrons down gradient)
*the electron transport chain is composed of multi protein complexes- proteins i to iv. there are also prosthetic groups which are non proteins bound to the proteins and help enzymes.
electrons move from protein i to iv losing energy
NADH-step 1- electron removed from nadh to complex i, then transferred to complex ii then moved to ubiquinone(small hydrophobic molecule), electron carriers after ubiquinone are called cytochrome and the prosthetic groups are known as heme groups( similar to hemoglobin, they have iron in them) the last protein complex iv passes electrons to oxygen (final electron acceptor)
FADH- donates electrons to protein complex ii at a lower energy state, then the same happens as NADH
ETC does not make atp it uses the energy from the descent of electrons to a lower energy state to pump hydrogen out into the inter membrane space where chemiosmosis harnesses the proton motive force to synthesize atp

Question 4

glycolysis

Answer 4

anaerobic- initial investment is 2atp in order to put glucose into a reactive state ( each side is phosphorylated).
glucose split into two 3 carbon compounds which are rearranged to form pyruvate.
two phases- energy investment and energy pay off.
atp invested when glucose is phosphorylized on both sides making fructose 1-6 biphosphate (glucoses structure changes)
this molecule then breaks into G3P(product of calvin cycle too) and DHAP. these two molecules produce 4 ATP and supply electrons when they are converted to pyruvate.
this all occurs in the cytoplasm

Question 5

citric acid cycle

Answer 5

this occurs in the matrix and is aerobic. pyruvate does not enter matrix, instead it is converted into acetyl coA by losing a CO2 molecule ( and reducing nadh). acetyl coA enters the citric acid cycle by binding to OXALOACETATE forming citrate(ionized form of citric acid)
the regeneration of oxaloacetate is the cycle, two carbons are stripped from citrate and reduce fadh and nadh
8 STEPS
steps 3,4,8- 3 NADH produced
step 6- 1 FADH produced
step 5- GTP generated
step 3 and 4- CO2 molecules given off (notice correlation between NAD being reduced

Question 6

chemiosmosis

Answer 6

chemiosmosis is the process in which hydrogen ion gradient across membrane is used to do work. definition**-energy coupling mechanism that uses stored protons to drive cellular work
atp synthase- a membrane protein that uses the proton motive force to phosphorylate atp. atp synthase is a multisubunit complex that has four parts, rotor stator internal rod and catalytic knob. one proton is moved into the binding site of the rotor, causing it to spin, the spinning of the rotor spins the internal rod, which activates the catalytic knob. stator is where the proton molecule enters and leaves, it also anchors the protein in the membrane.
* remember; etc establishes gradient using electron energy to pump protons across the membrane, energy in hydrogen ion gradient couples chemiosmosis with redox reactions of ETC
proton motive force- electrochemical gradient created from etc can perform work

Question 7

energy production (how many e produces how many atp)

Answer 7

each electron transported from nadh creates enough proton motive force to create 3 atp molecules, but this is not exact this is due to 3 reasons

1. phosphorylation(chemiosmosis) and redox reaction of etc not directly coupled so the ratio of redox reaction to atp production is not a whole number (how is it not directly coupled)NADH drives 10 protons across membrane and it takes 4 atp molecules to make atp 10/4= 2.5atp produces (or 3)
2. ATP yield depends on the type of electron carrier used (fadh carries less energy because it is not as efficient as nadh)
3. 34% of energy produced from electrons is proton motive force or chemical potential energy, its inevitable that some energy is lost as heat and other factors. so 34% of the energy created is used to synthesize atp (which is actually really good) this also varies under different cellular conditions.

Question 8

hibernating animals

Answer 8

reduction of energy is necessary for animals to hibernate. animals in winter that hibernate must have a lower metabolism.
brown fat-tissue cells that are packed with mitochondrion, their membranes contain channel proteins called uncoupling proteins which allow protons to fall down gradient without making atp
this is so important because stored fats are a source of heat but they don’t generate atp. atp cannot be generated because it would not be used and eventually stop cellular respiration therefore stopping heat.

Question 9

fermentation

Answer 9

glycolysis still occurs because it is anaerobic and in fermentation no oxygen is present.
Lactic acid- glycolysis produces two pyruvate molecules 4ATP and 2NADH in order to continue NADH must be freed up, so NADH donates its electrons to pyruvate turning it into lactic acid. this happens in human muscle cells when sugar catabolism outpaces oxygen consumeption. excess lactate is taken to the liver, and is oxidized back into pyruvate which can enter cellular respiration when more oxygen is present.
lactic acid does not cause muscle pain, it enhances muscle ability, the build up of k ions actually causes the pain.
alcohol fermentation-pyruvate created from glycolysis, must free up NADH to continue, so pyruvate gives off CO2 molecule making 2 acetaldehyde which is reduced by NADH making ethanol, yeast cells use this

Question 10

anaerobic respiration, obligate anaerobe, facultative anaerobe

Answer 10

anaerobic respiration-prokaryotes have etc but O2 is not the final electron acceptor, some use sulphate instead (so4-2) they are called sulphur reducing organisms
obligate anaerobe- uses fermentation or anaerobic respiration- can’t live in the presence of oxygen
facultative anaerobe- use fermentation when there is no oxygen present but use cellular respiration when there is oxygen present.
when there is no oxygen they must consume large amounts of sugar to produce the same amount of atp

Question 11

evolution and glucose

Answer 11

ancient prokaryotes used glycolysis to make atp (before oxygen was in the atmosphere), glycolysis is the most wide spread metabolic pathway today because it evolved so early. its cytosolic locations suggests that it evolved before eukaryotes

Question 12

other compounds used for cellular respiration

Answer 12

glucose and citric acid cycle can accept other molecules and oxidize them to produce electron carriers.
glycolysis- accepts carbohydrates ( such as glycogen the storage form of glucose in animals) - fatty acids and glycerol are converted to G3P which lose carbon dioxide to produce acetyl coA.-this is called BETAOXIDATION- fatty acids being converted into two carbon molecules
* fats produce the most energy, they produce two times the amount of atp as carbohydrates.

Question 13

biosynthesis

Answer 13

anabolic process that uses cellular respiration partially. food molecules are broken into simpler molecules that can be used by the cell to make its own macromolecules (amino acids can be used directly), compounds formed in glycolysis and the citric acid cycle can leave the mitochondria and be used to make other molecules. glycolysis and citric acid cycle function as metabolic interchanges that go back and forth

Question 14

photosynthesis, chloroplast parts, water

Answer 14

autotrophic organisms use photosynthesis to sustain themselves ( make their own food)
heterotrophic organisms eat other living things.
CHOLOPLASTS- found in mesophyll cells, CO2 enters through stomata and O2 also exits through them. water is absorbed by roots and is pulled up veins.
thylakoid- circular membrane sac
granum- stack of thylakoids
grana- all granum in chloroplast
thylakoid space- inside thylakoid
stroma- outside thylakoids
* photosynthesis does not produce sugar it produces G3P.
6CO2+ 6H2O+ LIGHT-> C6H12O6+ O2
12 molecules of water actual used and six produced this is just the net overall gain equation
water- water produces the hydrogen ions and electrons, oxygen is given off from water not CO2, CO2 is used directly for sugar synthesis. O2 given off right after water is split. proof; other organisms that use photosynthesis use CO2 ( and another molecule to supply the hydrogens and electrons), in this instance, water is not a waste product, leaving us to conclude that the oxygen produced is not from co2

Question 15

light

Answer 15

visible light is electromagnetic radiation and a part of the electromagnetic spectrum, with wavelengths between 380nm and 750nm.
photons- light behaves as particles (particles of photons) they have a fixed quantity of energy related to the wavelength-> shorter wavelength= higher energy.
pigments-(when light meets matter it is absorbed, reflected, or transmitted) pigments absorb visible light, different pigments absorb different wavelengths. wavelengths absorbed by pigments disappear. the colour of the pigment is the one wavelength that it reflects. black pigments absorb all light, white pigments reflect all light.
spectrophotometer measures the ability of a pigment to absorb various wavelengths of light- a beam of a certain wavelength is shone through object and the spectrophotometer measures the amount of light reflected or transmitted
absorption spectrum-graph plotting a pigments light absorption vs wavelength
light can only perform work if energy is absorbed

Question 16

pigments in chloroplasts

Answer 16

chlorophyll a- directly a part of photosynthesis (blue green) absorbs violet blue and red light and reflects green functional group is a methyl group (CH3)
chlorophyll b- accessory pigments called carotenoids (olive green colour)
the functional group is CHO for b
the functional groups for chlorophyll a and b are the only difference - these structural differences cause the pigments to absorb different wavelengths.
carotenoids- yellow/orange shades are not absorbed - they broaden the spectrum in chloroplasts, they also aid in photo protection- they absorb and dissipate excess light that could damage the other pigments

excitation of chlorophyll- 1 proton absorbed raises 1 electron to a higher energy shell.
ground state-pigment with electrons in normal shell
excited state-pigment has absorbed photon and the election is in a higher energy shell.

Question 17

weird phrase. i don’t know what its saying so i will memorize it and figure it out

Answer 17

the only photons absorbed are those whose energy are exactly equal to the energy difference between the ground state and the excited state.
this varies from molecule to molecule, particular molecule absorbs only photons corresponding to a specific wavelength- each pigment is unique

Question 18

Light reaction (info)

Answer 18

photosystem is made of reaction centre complex surrounded by light harvesting complexes(made of pigment molecules bound to proteins)

• photon is absorbed and electron is excited, energy is transferred from pigment to pigment (in the light harvesting complex), the energy is transferred to two chlorophyll a molecules which actually reduce the primary electron acceptor. the two chlorophyll a molecules in photosystem one and two differ.
• in photosystem 2 chlorophyll a molecules are known as p680 (strongest oxidizing agent known)
• in photosystem 1- chlorophyll a molecules are p700

Question 19

linear electron flow 8 steps

Answer 19

1.photon of light strikes pigment molecule in ps 2 in the light harvesting complex, electron is boosted to high energy and is transferred through pigment molecules until it reaches p680 where these electrons are excited
2. electron transferred from p680to primary electron acceptor
3. enzyme splits water into two electrons and two hydrogen ions, the electrons are transferred to p680 to replace the ones giving to the primary electron acceptor, h ions released in thylakoid space and O bonds with O and O2 is given off
4. photo excited electron passes from ps ii to ps i via electron transport chain - made of Pq, cytochrome, and pc.
5. exergonic fall of electrons to lower level of energy creates energy to produce a hydrogen gradient- when an electron passes through cytochrome,complex, and h ion is pumped INOT THE THYLAKOID SPACE
6. light energy transferred in light harvesting complexes reaches reaction centre complex exciting electrons in p700, this electron is transmitted to primary electron acceptor. ( electrons replaced from etc from psii)
7 photo excited electrons passed through redox reactions from primary electron acceptor of ps i down to another etc (hydrogen not pumped into thylakoid space- as there is no splitting of water)
8.enzyme called reductase transfers electrons from fd to NADP making NADPH - these hydrogen ions come from stroma

Question 20

chemiosmosis chloroplast vs mitochondria

Answer 20

chloroplast-
electrons come from water
uses light as energy
thylakoid membrane pumps h from stoma into thylakoid space

mitochondria- high energy electron supplied from organic molecules
uses organic molecule as oxidization energy
inner membrane pumps H out of matrix to inter membrane space

both-chemisomosis
-etc in membrane pumps protons across membrane as electrons are passed to increasingly electronegative electron carrier molecules in the etc
-redox reactions create proton motive force
-potential energy stored in H gradient used to synthesize atp. atp synthase in membrane couples H diffusing down gradient with atp production.
atp synthase alike
cytochromes alike
proton gradient can also be considered pH gradient because hydrogen ions increase acidity

Question 21

three things that contribute to the hydrogen gradient

Answer 21

hydrogen gradient- thylakoid space must be positive and the stroma is negative

1. water split in ps ii and produces hydrogen ions in the thylakoid membrane (which stay there they don’t need to be pumped in
2. as Pq transfers electrons to cytochrome, four protons are pumped into the thylakoid space.
3. hydrogen ions are removed from stoma and joined to NADPH

Question 22

calvin cycle

Answer 22

builds G3P (carbohydrate) using energy molecules created in the light reaction. its an anabolic process and it happens in the stroma. the starting molecule is regenerated when reactants enter and products leave. 3co2 enter and 1g3p molecule leaves.
-for one molecule of g3p, the cycle must happen three times.
carbon fiction- initial incorporation of CO2 into organic molecules
THREE PHASES
1. carbon fixation- rubisco attaches CO2 to RuBP (five carbon compound), the 6 carbon compound is unstable and quickly breaks into two three carbon molecules.
2.reduction- 3 carbon compound get phosphorylated by atp and reduced nadph and becomes G3P potential energy stored in this molecule. 3 CO2 molecules produce 6 G3P molecules, one G3P molecule is released and the others are used for the regeneration of RuBP.
3.reneneration of RuBP- 5 G3P molecules are rearranged into 3 molecules of RuBP (this uses atp)

Question 23

C3 plants

Answer 23

(use calvin cycle we just looked at)-once carbon is fixed the first organic compound is a three carbon compound. the stomatas of this plant close on hot days to prevent water loss, but this also prevents the uptake of CO2. because of this photorespiration occurs- which is when O2 a waste product of the light reaction, starts being used in the calvin cycle to replace co2- o2 binds with RuBP (with the help of rubisco) these form two carbon compound which leaves the chloroplast and is made into co2 (which then enters the calvin cycle as usual)
does not produce sugar
uses atp
this is considered evolutionary baggage because it decreases sugar synthesis
however photorespiration may provide protection against high energy products (atp nadph) of the light reaction that could be damaging if aloud to accumulate.
rice wheat soybeans

Question 24

C4 plants

Answer 24

corn sugarcane grass
modified sugar synthesis where CO2 is first converted into a four carbon compound.
instating of closing its stomata it partially opens it to allow co2 intake but also to avoid water loss.
sugar is made through two types of photosynthetic cells- mesophyll cells (the usual) and bundle sheath cells.
enzyme in mesophyll has high affinity for carbon dioxide and can fix it even when in low concentrations, 4 carbon compound created acts as a shuttle and moves into bundle sheath cells, which are packed around the veins, they release co2 to a level that allows the calvin cycle to continue and photorespiration is avoided ( photorespiration isn’t needed if the calvin cycle continues, so yes it does protect the plants, but photorespiration wouldn’t be needed in the first place if the calvin cycle, or a variation was functioning and these dangerous products wouldn’t accumulate.

Question 25

CAM plants

Answer 25

succulent plants, pineapple and cacti
carbon fixation called crassulacean acid metabolism ( in the plant family crassulacean)
open stomata at night and close it during the day(reverse of c3 plants or regular plants). when stomata are open, they take in CO2 and incorporate it into acids which are stored in vacuoles within the mesophyll cells
in the morning stomata closes and atp and nadph begin being produced - the organic acids release the co2 molecules and they are used for the calvin cycle.
unlike cam plants C4plants use two types of cells. cam plants like c3 plants use one type of cell; palisade mesophyll.

Question 26

importance of photosynthesis

Answer 26

50% of organic material made by photosynthesis, which is consumed for cellular respiration , the autotrophic part of the plant is green,the rest of the plant relies on this part for sustenance, for example sucrose produced from photosynthesis is transported through veins out of leaves and b glucose is used to make cellulose
photosynthesis is responsible for the oxygen in the atmosphere.