BIOCHAP6 2

Question 1

photoautotrophs:

mesophyll cells:

chlorophyll:

Answer 1

creates own energy via photosynthesis

plant cell type found in leaves,containing large amounts of chloroplasts

chemical found in thylakoids of chlorplasts, resp for absorbing light energy

Question 2

overview of photosynthesis

Answer 2

-plants r photoautotroph, create own energy via photosynthesis

• photosynth is when light energy is harnessed to produce glucose

-carbon water inputs to prod glucose,oxy and water, sunlight to catalyse reaction,glucose primary product

Question 3

photsynthesis equation

Answer 3

6CO2 carbon dioxide+ 12H20 water+ SUNLIGHT C6H12O6 glucose+ 6O2 oxy+ 6H2O water

Question 4

Structures involved in photosynthesis

Answer 4

leaves: plants maximise surface area to increase amount of light hitting its surface
- main leaves that photsynth are called mesophyll cells, chloroplasts r the main organelle where photosynth occurs, contain chlorophyll

stomata: on leave’s surface open and close to allow for gas exchange and to prevent water loss in dry env

xylem: transports water from roots to photosyhtesising cells in leaves

Question 5

The light-dependent stage and purpose

Answer 5

-occurs when light is present in the thylakoid membranes that make up the grana inside a chloroplast

purpose: to generate the high energy coenzymes NADPH and ATP to power te 2nd stage of photsynthesis

Question 6

steps in light dependent stage

Answer 6

1. light energy energises chlorophyll which pumps H+ and splits water

2.oxy is released from chloroplast and diffuse out of the stomata

3. H+ and e- generate NADPH and ATP

4.ATP and NADPH COENZYME MOVE TO LIGHT INDEPENDENT STAGE

Question 7

light independent stage
2nd stage of PHOTSYNTHESIS calvn cycle

Answer 7

glucose is formed from carbon dioxide,NADPH and ATP thRu cycles of reactions occur in stroma of cholorplasts
- does not require light, energsed by nadph and atp

Question 8

steps in light independent stage

Answer 8

1.CO2 enters calvin cycle n changes. it combines with a 5 carbon mole then splits into two 3 carbon mol

Nadph and atp provide enedery for further changes to carb mol
carbon mol cont to rearrange in cycle until a 3 carb mol is formed to create glucose
leftover oxy combines with hydrogen ions to form water as output

Question 9

factors affecting photsynthesis

Amount/Intensity of light

Answer 9

Amount of light available determines the rate of photosynthesis

rate increases until point X, then stays at a high constant rate.

reasons:

Maximum possible rate of photosynthesis reached

Question 10

ligt colour and photsynthesis:

Answer 10

wavelength and colour impacts process, plants r green bc tey absorb all other wavelenghts of light except green. they reflect green light

Question 11

temp and pH:

Answer 11

rate of photosynthesis is greatest when temp and pH matches optimal temp and pH of enzyme

Question 12

carbon dioxide:

Answer 12

CO2 is an imput in light independent stage of photsynthesis, which affects rate of it

Question 13

enzyme inhibition:

Answer 13

comp and non comp inhibitors can act on enzymes to reduce rate of photsynthesis - herbicide chem r inhibitors in photos

Question 14

water

Answer 14

when plants lack water, they close stomata to prevent water loss,limiting intake of carbon dioxide for photsnytsis

Question 15

Photorespiration:

Answer 15

RUBISCO is oxygenated and wastes energy produced.

Question 16

Carbon fixation:

Answer 16

inorganic carbon, is converted into organic compounds such as glucose. central part of the light-independent stage of photosynthesis.

Question 17

rubisco

Answer 17

• key enzyme of the light-independent

binds to carbon dioxide and facilitates further reactions in the photosynthesis process,

whilst other times it binds to oxygen and initiates a wasteful process called photorespiration.

Question 18

The role of Rubisco in photosynthesis

fixation
reduction
regeneration

Answer 18

uses 3 CO2 molecules and 3 RubP molecules to create 6 molecules of 3-PGA. these 6 3-PGA molecules are then transformed into G3P with the help of ATP and NADPH. one G3p molecule leaves to form glucose. remaining 5 × G3P are recycled with ATP to regenerate the 3 × RuBP

Question 19

Rubisco & Photorespiration

Answer 19

• High Substrate Concentration- here O₂
• High temperature
• Causes changes to the structure of the Rubisco

Question 20

Photorespiration

Answer 20

• Photosynthesis is disrupted
• CO₂ has less opportunity to bind and be fixed
• Less glucose produced
• Energy is wasted, impacts growth, reproduction and survival.

Question 21

photorepsiration hot and dry conditions

Answer 21

increased water loss - stomata close - O2 from light dependent reactions trapped in leaf - O2 concentration increases around Rubisco

rubiscos affinity changes as temp increases - more O2 is bound rather than CO2

= more photorespiration

Question 22

C4 Photosynthesis
steps

Answer 22

1. carbon diox enters mesophyll cells and is fixed by the enzyme PEP carboxalyse to form oxaloacetet
2. oxaloavetate is converted into malate and transported to bundle sheath cells

3.malate breaks down into pyruvate and CO2. CO2 enters the CC to produce glucose

4. Pyruvate returns to mesphyll cells to be converted back into PEP, restarting the cycle

Question 23

CAM Photosynthesis

Answer 23

Crassulacean Acid Metabolism

• Light-dependent stage the same in C3 and C4
• CAM plants open their stomata at night to prevent water loss via evaporation in the daytime.
• Requires more ATM than C3 photosynthesis.

Question 24

CAM cycle

Answer 24

1. CO2 is fixed into oxaloacetate by PEP carboxylase
2. oxaloacetate is converted into 4 diff carbon molecule
3. the molecule is stored in the vacuole until daytime
4. during day time, the molecule is broken down into CO2 for CC

Question 25

Arable land:

Answer 25

land that is suitable for growing crops

Question 26

Improving photosynthetic efficiencies and crop yields

Answer 26

• rubisco in absence of high CO2 levels can initiate photorespiration which decreases efficiency of photsynthesis

-agricultral productivity will need to double to cope with demands of rising global pop

-climate chnage can reduce crop yeilds globally

Answer 27

helps make plants effiecient at photsynth by editing genes to bypass photorepisration, enhance rubisco function, improve chlorplast effiency and reduce water stress by targeting stomata