M5 CH17 Energy for Biological Processes

Question 1

What are the two stages of photosynthesis?

Answer 1

The two stages of photosynthesis are:
-The light-independant reaction
-The light-dependant reaction

Question 2

What is the light-dependant reaction in photosynthesis?

Answer 2

The light-dependant reaction in photosynthesis:
-Occur within the thykaloid membranes in chloroplasts
-Requires light as it produced ATP + NADP

Question 3

What is the light-independant reaction in photosynthesis?

Answer 3

The light-independant reaction in photosynthesis
-Uses the products from the light-dependant reaction
-Occurs within the stroma - fast diffusion from thykaloid to stroma
-Involves the Calvin Cycle

Question 4

What are autotrophs?

Answer 4

Autotrophs are oganisms that synthesis complex organic molecules from simple inorganic ones

Question 5

Chemoautotrophs, Photoautotrophs, Heterotrophs

Answer 5

Chemoautotrophs - uses chemical energy (nitrifying bactera)
Photoautotrophs - uses light energy (plants, algae)
Heterotrophs = doesn’t make own food (humans)

Question 6

What is the endosymbiant theory?

Answer 6

Endosymbiant theory = cells have developed from prokaryotes

Question 7

What is photolysis?

Answer 7

Photolysis = enzyme-catalysed reaction -> water molecules split using light energy

Question 8

What is phosphorylation?

Answer 8

Phosphorylation = formation of ATP

Question 9

What is NADP?

Answer 9

NADP = co-enzyme that reduces GP molecules within the calvin cycle

Question 10

What is chemiosmosis?

Answer 10

Chemiosmosis = flow of H ions through ATP synthase = the force of the flow produced ATP

Question 11

What are co-enzymes?

Answer 11

Co-enzymes carries out oxidation/reduction, carrying molecules between reactions

Question 12

What are the steps involved in non-cyclic phosphorylation (LIR)

Answer 12

Non-cyclic phosphorylation:
Light energy is absorbed by the pigments in PSII, exciting electrons. These electrons are then passed through an electron transport chain (ETC) to PSI, releasing energy that is used to generate a proton gradient across the thylakoid membrane.

Water molecules are split by PSII, releasing electrons, protons (H+), and oxygen gas. The electrons from water replace the electrons lost by PSII and are passed through the ETC to PSI.

The high-energy electrons from PSI are used to reduce NADP+ to NADPH, which is used as a reducing agent in the light-independent reactions of photosynthesis.

The proton gradient generated by the ETC is used by ATP synthase to generate ATP from ADP and inorganic phosphate.

Question 13

What is non-cyclic phosphorylation

Answer 13

Non-cyclic phosphorylation is the process of generating ATP through the transfer of electrons from NADH and FADH2 to oxygen in the mitochondria. This process also generates a proton gradient which drives ATP production.

Question 14

Why is non-cyclic phosphorylation known as non-cyclic?

Answer 14

It is non-cyclic because electrons that return to the chlorphyll molecules are not the same as the electrons that left the chlorophyll

Question 15

What is cyclic phosphorylation?

Answer 15

Cyclic phosphorylation happens when NADP produced fits the needs of the plant, and so the light energy can be used elsewhere
-Only makes ATP
-Only happens using PS1
-Electrons return to original position rather than being given to NADP

Question 16

Outline the process of the Calvin Cycle (light-dependant stage of photosynthesis)

Answer 16

CO2 (1carbon) -> Rubisco (enzyme) -> 2x GP (6carbon) -> ATP used and phosphorylised, reduced NADP oxidised -> 2xTP (6 carbons) -> 1 carbon given off to produce 1 glucose -> ATP added and RuBP used up (5 carbons) -> returns to rubisco

Question 17

What is the calvin cycle?

Answer 17

The Calvin Cycle:
-Is the light-dependant stage of photosynthesis
-Occurs in the chloroplast stroma
-Repeats 6 times to make 1 molecule of glucose
-5 out of 6 molecules of TP used to regenerate RuBP -> the leftover carbon makes hexose sugar (glucose)

Question 18

Outline the role of carbon dioxide in photosynthesis

Answer 18

Role of carbon dioxide in photosynthesis:
-Source of cabron
-Once fixed, used to build more complex molecules
-All molecules are organic/carbon based -> eg glucose + amino acids -> proteins

Question 19

Why are there only small amounts of RuBP in the stroma of chloroplasts?

Answer 19

There are only small amounts of RuBP because it is being continuously regenerated in the cycle

Question 20

Why does the chloroplast fluid contain enzymes?

Answer 20

Chloroplast fluid contain enzymes for metabolic reactions such as calvin cycle -> ie rubisco

Question 21

Why does the stroma fluid surround the grana of chloroplasts?

Answer 21

Stroma fluid surrounding grana means products from the LIR are quickly passed onto the LDR for the calvin cycle/photosynthesis

Question 22

Identifying the thykaloids in a microscopic image

Answer 22

Thykaloids appear as black bands under microscopes

Question 23

What are found between thykaloids?

Answer 23

Integranal lamallae are found between thykaloids

Question 24

Photosynthetic pigments

Answer 24

Photosynthetic pigments are found in thykaloid membranes, and absorb certain wavelengths of light, reflecting others (green)

Question 25

Which ion is found within chlorophyll?

Answer 25

A magnesium ion is found wtihin the centre of chloroplast

Question 26

What is the primary pigment of chloroplasts?

Answer 26

Primary pigment = chlorphyll a -> as it has mg -> two types: P680 and P700

Question 27

What are the acessory pigments and their colours within chloroplasts?

Answer 27

Acessory pigments in chloroplasts:
-Chlorophyll b -> bluey-green
-Carotene -> orange
-Xanthophyll -> yellow

Question 28

What is the light harvesting system in chloroplasts

Answer 28

Light harvesting system:
-Aborbs/harvests light of energy of different wavelengths and transfer this energy to the reaction centre, where chlorophyll a is located and where mg electrons become exited

Question 29

What are photosystems?

Answer 29

Photosystems are clusters where photosynthesis pigments are found

Question 30

Where is P680 of chlorophyll a located?

Answer 30

P680 of chlorophyll a is located in photosystems 2 - peak absorption is 680nm

Question 31

Where is P700 of chlorophyll a located?

Answer 31

P700 of chlorophyll a is located in photosystem 1 -> peak absorption is 700nm`

Question 32

Chloroplast adaptations

Answer 32

Chloroplast adaptations:
-Inner membrane contains transporter proteins
-Lots of grana -> more pigments
-Proteins embdedded in grana -> holds photosystems in place
-Enzymes within stroma
-Grana surrounds strama for ease of product acess between stages
-DNA and ribosomes for proteins

Question 33

How to calculate rf value?

Answer 33

Rf value = (distance moved by solute) / (distance moved by solvent)

Question 34

What is the photolysis of water in the LDR in photosynthesis?

Answer 34

The photolysis of water - light energy causes a water molecule to split apart and release hydrogen ions, electrons and oxygen. The electrons from water replace the electrons lost from PSII. As the electrons move along the electron transport chain, they move from high to low energy

Question 35

What are the limiting factors of photosynthesis?

Answer 35

Limiting factors of photosynthesis:
-Temperature (enzyme-controlled LIR affected)
-Light intensity (LDR-> photolysis needs light to occur, blue and red light must be in balance, GP accumulates due to reduced ATP and NADH, leading to low TP and RuBP)
-Carbon dioxide
-Water

Question 36

Why is light intensity a limiting factor of photosythesis?

Answer 36

Light intensity - limiting factor of photosynthesis - LDR-> photolysis needs light to occur, blue and red light must be in balance, GP accumulates due to reduced ATP and NADH, leading to low TP and RuBP

Question 37

Why is measuring O2 only an approximate prediction of photosynthetic rate/why is it not entirely accurate?

Answer 37

O2 is a waste product of photosynthesis and so is used as an approximate prediction. However, O2 could be used in respirational processes as well as O2 only being present in the LDR due to the photolysis of water.