photosynthesis & respiration

Question 1

reduction =

(biology version)

Answer 1

gain of electrons & gain of H2

Question 2

which organelle does photosynthesis occur in?

Answer 2

chloroplast

Question 3

thylakoid =

Answer 3

folded membrane containing chlorophyll

Question 4

grana =

Answer 4

stack of thylakoids

Question 5

which part of the chloroplast does the ‘light-dependant’ reaction occur in?

Answer 5

thylakoid membranes

Question 6

summary of ‘light-dependant’ reaction

Answer 6

light energy & H2O used to prod. reduced NADP & ATP

(NADP –> P for photosynthesis)

Question 7

the 4 stages of the ‘light-dependant’ reaction

Answer 7

1. photolysis
2. photoionisation
3. photophosphorylation
4. chemiosmosis

Question 8

‘photolysis’

Answer 8

• the breaking down of H2O molecules, using light energy
• prod H+ & e-
• O2 formed (waste product)

Question 9

‘photoionisation’

Answer 9

• light energy absorbed by chlorophyll
• excites electrons to higher energy level
• electrons emitted from chlorophyll
• leaves +vely charged chorophyll ion

Question 10

‘photophosphorylisation’

Answer 10

• excited electrons passed along electron transfer chain, releasing energy
• electron carriers reduced then oxidised (gain then lose elc)
• excited elc gradually loses energy when passed along chain

Question 11

‘chemiosmosis’

Answer 11

• the energy released by the excited elc moving down the etc. actively transports H+ protons from the stroma –> thylakoid lumen
• electrochemical gradient created
• the H+ protons return to stroma via faciliated diffusion, through ATP synthase
  (process prov. energy needed to prod atp –> Pi added to ADP via ATP synthase)

Question 12

the cycle for the ‘light-independant’ reaction is called…

Answer 12

the calvin cycle

Question 13

which part of the chloroplast does the ‘light-independant’ reaction occur in?

Answer 13

the stroma

Question 14

summary of the ‘light-independant’ reaction

Answer 14

reduced NADP used to prod. simple sugar
(energy prov. by hydrolysis of ATP)

Question 15

describe the calvin cylcle (5)

Answer 15

1. 5C RuBp (ribulose biphophate) **combines **with CO2
2. prod. two 3C glycerate(-3)phosphate (GP), using ATP
3. GP reduced to 3C TP (triose phosphate)
4. using electrons from red. NADP & energy from ATP
5. two molecules of TP = hexose
6. all RuBp regenerated

Question 16

facrors that affect the rate of photosynthesis

Answer 16

• intensity of light
• wavelength of light

Question 17

why might chloroplasts absorb certain wavelengths of light better than others?

Answer 17

chloroplasts contain diff. photosynthetic pigments –> absorb diff. wavelengths
(chlorophyll A, chlorophyll B & carotenoids etc)

Question 18

explain why CO2 is limiting for top leaves of trees

Answer 18

1. light isn’t limiting –> rate of LDR is fast
2. temp isn’t limiting –> fast reactions of enzymes in LDR
3. high use of CO2 –> LDR is limiting

Question 19

explain how O2 production shows photosynthesis

Answer 19

• O2 prod. in LDR
• faster O2 production = faster LDR

Question 20

chromotography

explain why origin marked in pencil (2)

Answer 20

• ink & leaf pigments would mix
• pencil line remains in same position

Question 21

chromatography

name 2 advantage of diff. pigments

Answer 21

1. absorbs more wavelengths of light for photosynthesis
2. more efficient photosynthesis if some wavelengths not present

Question 22

which organelle does aerobic respiration occur in?

Answer 22

mitochondria

Question 23

name the diff. stages of aerobic respiration

Answer 23

1. glycolysis
2. link reaction
3. krebs cycle
4. oxidative phosphorylation

Question 24

which parts of the mitochondria do the diff. stages of aerobic resp. occur in?

Answer 24

1. glycolysis –> cytoplasm
2. link reaction –> matrix
3. krebs cycle –> matrix
4. oxidative phosphorylation –> inner membrane of mitochondrial cristae

Question 25

**'glycolysis'**

Answer 25

* **phosphorylation** of glucose using ATP * **oxidation** of TP to pyruvate * net gain of ATP * NAD **reduced**

Question 26

**'link reaction'**

Answer 26

* pyruvate oxidised into **acetate**, losing H2 & prod. reduced NAD * acetate combines w coenzymeA --> prod **acetylcoenzymeA** --> also **releases** CO2 * thus ***'oxidative decarboxylation'*** occurs (for every glucose molecule in glycolysis, LR occurs 2x as 2 pyruvates prod in glycolysis)

Question 27

**'krebs cycle'**

Answer 27

* a 4C molecule combines with 2C acetylcoA, forming 6C **citrate** which enters cycle & releasing coenzymeA * ***oxidative decarboxylation*** of citrate --> CO2 lost & H2 removed to reduce coenzymes NAD n FAD * ***'subtrate level phosphorylation'*** occurs --> energy from dehydrogenation used to form ATP from ADP + Pi * 4C molecule regenerated

Question 28

**'oxidative phosphorylation'**

Answer 28

* coenzymes donate H2 to one of the proteins * H2 atoms split into **protons & elc** * elc transferred down etc --> prov. **energy** for H+ protons to move into **intermembrane** space * oxygen = final electron acceptor --> H2O formed

Question 29

how is ATP prod in both photosynthesis & resp? | (chemiosmotic theory)

Answer 29

protons diffuse down an **electrochemical gradient** through ATP synthase enzyme, embedded in membranes of cellular organelles

Question 30

explain why plants make ATP in **both** respiration & photosynthesis

Answer 30

1. photosynthesis doesnt prod ATP in darkness 2. ATP **cannot** be moved from cell to cell 3. plant uses **more** ATP than prod. in photosynthesis eg for active transport 4. so ATP must also prod via resp

Question 31

state when NAD reduced in resp

Answer 31

* glycolysis * LR * krebs cycle

Question 32

state when CO2 is made in resp

Answer 32

* LR * krebs cycle

Question 33

describe how acetylcoA formed

Answer 33

1. H2 removed from pyruvate & CO2 released 2. addition of coenzymeA

Question 34

describe how ATP made in mitochondria

Answer 34

1. ***'substrate level phosphorylation'*** 2. krebs cycle & LR prod. coenzymeA, red NAD n FAD --> elc released 3. electrons pass along etc 4. protons move into **intermembrane** space 5. **energy** released to join ADP + Pi --> ATP 6. through ATP synthase

Question 35

anaerobic resp

Answer 35

* no final electron acceptor * no krebs cycle * ATP can still be prod via glycolysis when NAD is oxidised

Question 36

# anaerobic resp ethanol pathway | (used by yeast & microorganisms)

Answer 36

* pyruvate from glycolysis **decarboxylated** to ethanal * **ethanal** reduced to **ethanol** via enzyme alcohol dehydrogenase * ethanal = hydrogen acceptor (frrom oxidation of red NAD) * ethanol **CANNOT** be metabolised

Question 37

# anaerobic resp lactate pathway | (used by mammals)

Answer 37

* red NAD transfers its hydrogens to pyruvate to convert it to lactate * pyruvate also **reduced** to **lactate** by enzyme lactate dehydrogenase * pyruvate = hydrogen acceptor * lactate **CAN** be further metabolised

Question 38

advantage of converting lactate back into pyruvate

Answer 38

1. pyruvate = energy source 2. mucles have increased ATP supply 3. restores pH levels

Question 39

explain why coloured liquid moves into respirometer

Answer 39

1. oxygen taken up in aerobic resp 2. CO2 given out absorbed by KOH sol 3. decrease in volume of gas

Question 40

explain why respirometer is airtight

Answer 40

1. no oxygen can enter 2. no carbon dioxide can escape 3. allows accurate measuring 4. prevents entry of microorganisms 5. prevents competition with yeast

Question 41

suggest why respirometer left for 10 mins

Answer 41

1. equilibrium reached 2. allows resp rate to stabilise

Question 42

how to get reliable results

Answer 42

1. repeat to identify anomalies 2. carry out statistical tests to ensure results are significant