3.5.1 photosynthesis

Question 1

how is the palisade cell having lots of chloroplasts an adaptation?

Answer 1

large concentration of chlorophyll, absorbs as much light for photosynthesis as

Question 2

how is the palisade cells having chloroplasts that are able to move with the cytoplasm an adaptation?

Answer 2

absorb light from any direction

Question 3

how is the palisade cells being long and narrow an adaptation?

Answer 3

many cells can be packed into the surface layers of the leaf

Question 4

how is the palisade cells having many leucoplasts an adaptation?

Answer 4

to store starch , the insoluble polymer produced in photosynthesis will not alter the water potential

Question 5

how is palisade cells having many mitochondria and RER an adaptation?

Answer 5

to provide energy for synthesis of proteins such as enzymes and carrier proteins

Question 6

how do palisade cells having a large permanent vacuole be an adaptation?

Answer 6

to store cell sap which is a sugary solution that maintains cell turgor supports the cells holding the plant upright to absorb as much light as possible

Question 7

what are the features of the chloroplast?

Answer 7

inner membrane
inter membrane space
outer membrane
ribosomes
stroma
starch grain
lipid droplet
granum
inter granar membrane
thylakoids

Question 8

why does the chloroplast have its own circular DNA and ribosomes?

Answer 8

in order to able to synthesise its own proteins

Question 9

what are the three meanings of oxidation?

Answer 9

loss of electrons
loss of hydrogen
gain of oxygen

Question 10

what are the three meanings of reduction?

Answer 10

gain of electrons
gain of hydrogen
loss of oxygen

Question 11

what are the 2 stages of photosynthesis?

Answer 11

light dependent reaction
Calvin cycle (light dependent reaction)

Question 12

where do light dependent reactions take place?

Answer 12

thylakoid membranes

Question 13

outline what happens in a light dependent reaction

Answer 13

light energy is absorbed by chlorophyll
electrons in chlorophyll become excited and are released from the chlorophyll (photoionisation)

Question 14

what is the energy from the light dependent reaction used for?

Answer 14

to make ATP from ADP and Pi (phosphorylation)
make reduced NADP
splitting of water into protons, electrons and oxygen (photolysis)

Question 15

what is a coenzyme?

Answer 15

a molecule that aids the function of an enzyme

Question 16

what is the coenzyme used in photosynthesis?

Answer 16

NADP

Question 17

what are the 2 types of phosphorylation?

Answer 17

non cyclic
cyclic

Question 18

what is non-cyclic phosphorylation?

Answer 18

• produces ATP, NADPH and oxygen
• uses both photo systems
• electrons are passed to NADP

Question 19

what is cyclic phosphorylation?

Answer 19

-produces ATP only
- only uses photo system 1
- electrons are not passed onto NADP instead are passed back to photo system 1
- only produces small amount of ATP

Question 20

explain what happens during the photoionisation of chlorophyll

Answer 20

light energy is absorbed by chlorophyll in photosystem 2
light energy excites electrons in chlorophyll
electrons move to higher energy level and released from chlorophyll

Question 21

explain what happens in photolysis of water

Answer 21

excited electrons that have left the chlorophyll have to be replaced
light energy splits water into protons, electrons and oxygen

Question 22

explain what happens during photophosphorylation

Answer 22

electrons moving down electron transport chain lose energy that is used to transport more protons into the thylakoid
thylakoid has higher proton concentration than stroma
proton gradient across membrane
protons move down gradient via ATP synthase complex back into stroma

Question 23

explain what happens during reduction of NADP

Answer 23

light energy is absorbed by photosystem 1
this excites electrons to an even higher energy level
these electrons are transferred to NADP in the stroma along with protons to form NADPH

Question 24

what is chemiosomotic theory?

Answer 24

movement of electrons down electron transfer chain
coupled to the transfer of protons into the thylakoid to build an electrochemical gradient
movement of protons back across a membrane down electrochemical through ATP synthase complex

Question 25

outline what happens in the Calvin cycle

Answer 25

CO2 is fixed to RUBP catalysed by the enzyme Rubisco
thus produces 1 highly unstable 6C molecule which immediately breaks down to 2 molecules of GP
GP is reduced to TP (gains hydrogen)
using the hydrogen transferred from reduced NADP
using energy transferred from hydrolysis of ATP
1/6 of TP is converted to useful organic substances
5/6 is used to regenerate RUBP so the cycle can continue

Question 26

what is a compensation point?

Answer 26

rate of photosynthesis = rate of respiration