Unit 2.1 : Photosynthesis

Question 1

Chemical equation

Answer 1

CO₂ + 6H₂O + Light energy (chlorophyll / enzymes) → C₆H₁₂O₆ + O₂.

Carbon dioxide + water + sunlight → glucose (sugar) + oxygen

Question 2

Leaf key features : chlorophyll capture

Answer 2

Thin: gases reach cells

Wide & Flat: large S.A to absorb light

Veins: support , H20 to cells, take glucose away

Stomata: pores (movement of gases)

Question 3

Labelling Leaf Structure

Answer 3

1. Cuticle
2. Upper epidermis
3. Palisade cells
4. Mesophyll
5. Vascular bundle (xylem , phloem)
6. Sponge parenchyma
7. Stomata (guard cells, pore, nucleus)
8. Lower epidermis

Question 4

Labelling Chloroplast:

Answer 4

Starch granule
Stroma
Double membrane

Chlorophyll
Lamella(e)
thylakoid
Granum
Grana
Intergranum

Question 5

LIGHT PHASE when & where

Answer 5

LIGHT DEPENDENT (1st)
- thylakoid of granum
(2 lamellae joined @ ends containing chlorophyll)

Question 6

Light phase reactants:

Answer 6

H2O + Radiant Energy

Question 7

Light Phase products:

Answer 7

ATP, O2, H+

Question 8

Light phase processes

Answer 8

1. Photolysis (water split - O2 , H2)
2. Photophosphorylation (ATP made)

O2 : Stomata –> air
ATP + H+ –> Dark phase
H+ taken by “taxi” (NADP)

formed:
NADP.2H (taken to DARK phase)

Question 9

PROCESS LIGHT PHASE

Answer 9

Radiant energy (sun)
Chlorophyll molecule
electron-energised CHEM POT. ENERGY

1. Photolysis
   splitting of H20 using C. P. E
   : NADP.2H (Dark phase)
   : O2 (BY PRODUCT) leaves through stomata
2. Photophosphorylation
   make ATP using C.P.E
   (ADP + P + C. P.E) =
   ATP (Dark phase)
   adenosine triphosphate

Question 10

DARK PHASE /
CALVIN CYCLE /
BIOCHEMICAL PHASE

Answer 10

Light independent
where? STROMA
products: ATP, O2, H+

Question 11

Dark phase process

Answer 11

NADP.2H drops off H+
returns to Light phase (fetch more)

CO2 + H+ –> C6H12O6

Glucose:
complex carbs
proteins
lipids
(cellulose + starch)

Question 12

What is the calvin cycle?

Answer 12

A series of enzyme controlled reactions combining high energy hydrogen ions with CO2 to make glucose.

Question 13

Order of steps in DARK phase

Answer 13

1. CO2 enters (pores of stomata)
2. ADP + P + C.P.E = ATP
3. NADP.2H drops off H+
4. NADP returns to L.P to fetch H+
5. ADP + P ==> light phase
6. CO2 + H+ = Glucose

Question 14

Importance of Photosynthesis:

Answer 14

1. Gives O2 for cell resp.
2. Regulates CO2 in atmosphere
3. FOOD

(During photosynthesis , radiant energy captured + stored as C.P.E in glucose)
- carbs
- oils
- proteins
energy rich compounds = food

Question 15

factors affecting photosynthesis

Answer 15

1. Light intensity
2. CO2 concentration
3. Temp + pH
   (cold + incorrect pH = inactive)
   (hot = denature)

Question 16

enzymes as catalysts

Answer 16

-lowers activation energy
- speed up reactions
- active site = reused

Question 17

Name the source of the energy that organisms use to stay alive

Answer 17

radiant energy

Question 18

Define the term Heterotrophs

Answer 18

Organisms that cannot make their own food and have to retrieve their energy by eating other organism in their environment.

Question 19

Define Autotrophs

Answer 19

Organisms (mainly plants) that get their energy in the form of radiant energy from the sun and use it to make glucose which can be converted to other organic compounds.

Question 20

List and explain 4 ways that leaves are suited to perform photosynthesis:

Answer 20

1. Held in a position that exposes to sunlight
2. Transparent cuticle and epidermal cells allow light to pass through easily
3. Usually flat which increases surface area exposed to radiant energy (more absorbed)
4. Thin which allows radiant energy to reach the mesophyll layer (where chloroplasts are found) easily

Question 21

Reactants of Photosynthesis?

Answer 21

Water and carbon dioxide

Question 22

Products of photosynthesis?

Answer 22

Glucose and oxygen

Question 23

Explain how the two reactants of photosynthesis (H2O + CO2) reach the leaf where photosynthesis will happen?

Answer 23

Water is absorbed by the root and then moved to the xylem. It moves to and up the stem to the leaves. It will then leave the xylem and move to the mesophyll cells and move to the chloroplasts.

Carbon dioxide diffuses into leaves through the stomata and into mesophyll and chloroplasts.

Question 24

Why are sunlight , chlorophyll and enzymes not in the equation but rather placed above arrow?

Answer 24

They are biocatalysts which facilitate the reaction
(they are not used up in the reaction but are essential for the reaction)

Question 25

The light dependent phase takes place in the ........... of the chloroplast The ......... energy is changed to .......... energy by the .................. ........... molecules that trap the light and release energised electrons

Answer 25

1. thylakoids / grana 2. radiant 3. chemical potential 4. energised chlorophyll

Question 26

Chemical energy from the sun is used to split a water molecule into oxygen and hydrogen. The ...... is released as a ............ through the stomata. A carrier molecule in the stroma called NADP , bonds with the ....... and transports it to the dark phase as .......

Answer 26

1. Oxygen 2. by-product 3. hydrogen 4. NADP.H2

Question 27

During phorphorylation energy is stored in ....... , which is going to be used in ........ phase. The energised electrons bond an ADP molecule with a ......... and C.P.E to form ATP

Answer 27

1. ATP 2. Dark 3. Phosphate ion

Question 28

At the end of the light phase ..... is released as a ........ product and Hydrogen and ATP are moved to DARK phase

Answer 28

1. Oxygen 2. by-

Question 29

The dark phase involves a series of chemical reactions referred to as: ....... ....... These reactions are controlled by .......

Answer 29

Calvin Cycle enzymes

Question 30

Carbon dioxide enters leaf through ..... hydrogen atoms from LIGHT PHASE are bonded with carbon dioxide to form ....... The energy for these reactions is supplied by .... molecules from light phase. Glucose is formed and will be used as fuel during ......

Answer 30

1. Stomata 2. glucose 3. ATP 4. Cellular respiration

Question 31

What happens to glucose after photosynthesis?

Answer 31

1. Used for cell resp to release energy for metabolic reactions 2. Stored as starch as it is unreactive and insoluble molecule 3. transported as sucrose as it is soluble in water but reactive 4. Converted to cellulose (polysaccride) to form part of cell walls in plants 5. Made into other organic compounds such as proteins or lipids (fats + oils)

Question 32

How does photosynthesis keep the balance of oxygen and carbon dioxide in the air?

Answer 32

Photosynthesis releases oxygen which is used for cellular respiration to provide energy for metabolic/ life processes. Makes food (glucose / starch) for heterotrophs Takes up CO2 which keep the atmospheric levels constant

Question 33

Describe the trend of light intensity:

Answer 33

As light intensity increases so does the rate of photosynthesis until it reaches an OPTIMUM and stays CONSTANT This is because the Dark phase cannot keep up with the light phase. There is not enough CO2 to enter the light phase or use the H and ATP made in the light phase. (or the temp is too low for the enzymes to allow chemical reactions to go faster)

Question 34

Describe the trend of TEMP

Answer 34

As temp increases, rate of photosynthesis increases up until an OPTIMUM is reached and then photosynthesis decreases rapidly (denature) This is because the increase in temp provides energy for enzyme activity, speeding it up until the optimum is reached. If the temps go too high, it will cause the enzymes to denature not allowing them to function. This will mean that the chem reactions for photosynthesis that are controlled by enzymes will not occur.

Question 35

Describe the trend of CO2 CONCENTRATION

Answer 35

As levels of CO2 increase so does the rate of photosynthesis . Increases up until OPTIMUM and then stays CONSTANT. It increases because carbon dioxide is a raw material for photosynthesis but after a certain point no matter how much CO2 is present, the dark phase's biochemical reactions cannot go any faster.

Question 36

LIGHT

Answer 36

Increases up to optimum then stays constant. Light provides radiant energy which is changed into chemical potential energy used for photolysis and photophosphorylation.

Question 37

CARBON DIOXIDE

Answer 37

Increases up to an optimum and then stays constant CO2 is a raw material. The calvin cycle of Dark phase can only process a limited amount of it, therefore it stays constant once it reached its OPTIMIM

Question 38

TEMPERATURE

Answer 38

Increases up to an optimum, then decreases rapidly. At cold temps photosynthesis happens slowly. As temp increases, rate of photosynthesis increases. After the optimum temp, enzymes denature and the rate rapidly decreases to zero

Question 39

Test for Oxygen:

Answer 39

Glowing splint (bursts into flame)

Question 40

Test for CO2

Answer 40

Clear lime water --> milky

Question 41

test for starch:

Answer 41

iodine solution

Question 42

test for glucose

Answer 42

benedict's solution 1. blue 2. green 3. yellow 4. orange / red 5. brick red

Question 43

time to destarch plant:

Answer 43

48hrs

Question 44

extract chlorophyll:

Answer 44

ethanol

Question 45

absorb Co2

Answer 45

sodium hydroxide potassium hydroxide hydroxide soda lime

Question 46

give off CO2

Answer 46

sodium bicarbonate chalk calcium carbonate carbonate

Question 47

Photosynthesis investigations:

Answer 47

TEST FOR: Starch (iodine solution) aluminium strip on leaf 2 flasks on leaves (co2 vs control) water plant (glowing splinter) weed submerged (boiling water + ethanol)