Topic 5 - Photosynthesis and Respiration

Question 1

What is the equation for photosynthesis ?

Answer 1

6CO2 + 6H2O = C6H12O6 + 6O2

Question 2

What is photosynthesis ?

Answer 2

The process where energy from light is used to make glucose.

Question 3

What is the equation for respiration ?

Answer 3

C6H12O6 + 6O2 = 6CO2 + 6H2O

Question 4

What is respiration ?

Answer 4

The release of energy

Question 5

What does anaerobic respiration in plants and yeast produce ?

Answer 5

ethanol and carbon dioxide

Question 6

Why is ATP needed ?

Answer 6

cells cant get energy directly from glucose, so in respiration the energy released from glucose is used to make ATP which carries energy in cells to where it is needed.

Question 7

What is a photosystem ?

Answer 7

A light absorbing pigment attached to a protein. it contains chlorophyll in the middle

Question 8

where are the products of photosynthesis stored ?

Answer 8

starch grains in the stroma

Question 9

What is the thick fluid in chloroplast called ?

Answer 9

stroma

Question 10

Where does the light dependent reaction of photosynthesis take place ?

Answer 10

The thylakoid membrane of the chloroplast

Question 11

What is the light dependent reaction of photosynthesis also called ?

Answer 11

Photophosphorylation

Question 12

What occurs during photophosphorylation (LDR) ?

Answer 12

1. Photoionisation: light energy is absorbed by the chlorophyll. The light energy excites electrons and they move to a higher energy level. They move down an electron transport chain and a series of redox reactions occur.
2. Photolysis: These electrons must be replaced so light energy is used to split water into oxygen, protons and electrons
3. Chemiosmosis: The electrons loose energy as they move down the electron transfer chain and this energy is used to transport the protons across the membrane into the thylakoid. This forms a proton gradient. Protons move down the concentration gradient by ATP synthase.
4. The energy from this movement combines ADP and Pi to form ATP.
5. The electrons and protons are transferred to NADP to form reduced NADP.

Question 13

What is the light independent reaction also called ?

Answer 13

The calvin cycle

Question 14

Where does the calvin cycle take place ?

Answer 14

The stroma of the chloroplast

Question 15

What is the function of the calvin cycle ?

Answer 15

It makes triose phosphate which can be used to make useful compounds such as carbohydrates, lipids and proteins.

Question 16

What happens during the light independent reaction

Answer 16

1. Carbon dioxide enters the leaf through the stomata and diffuses into the stroma of the chloroplast. It is combined with RuBP ( a five carbon compound), this reaction is catalysed by rubisco. This produces an unstable 6 carbon compound which quickly breaks down into 2 molecules of a 3 carbon compound called GP
2. GP is reduced into triose phosphate by reduced NADP.
3. Some triose phosphate is converted into useful compounds, e.g. glucose. Some continue into the calvin cycle to regenerate RuBP which uses ATP from the LDR.

Question 17

What useful organic substances are triose phosphate converted into ?

Answer 17

Carbohydrates
lipids
amino acids.

Question 18

How many turns of the calvin cycle produces 1 hexose sugar?

Answer 18

6 turns.
3 turns makes 6 triose phosphate molecules.
5 out of 6 molecules are used to regenerare RuBP.
1 molecule of triose phosphate is left however it only contains 3 carbon atoms, so 3 more turns are needed to result in another triose phosphate molecule. resulting in a hexose sugar.

Question 19

what are the products of the LDR ?

Answer 19

ATP
reduced NADP

Question 20

Why do plants look green ?

Answer 20

only certain wavelengths of light are used for photosynthesis.
The photosynthetic pigments only absorb red and blue light in sunlight, green light is reflected which is why they look green.

Question 21

What are limiting factors for photosynthesis ?

Answer 21

light intensity
temperature
carbon dioxide levels

Question 22

What are the similarities and differences of aerobic and anaerobic respiration ?

Answer 22

aerobic requires oxygen, however anaerobic does not
they both produce ATP, although anaerobic produces less
Both start with glycolysis but the stage after differ.
Both take place in the cytoplasm of cells

Question 23

What is glycolysis ?

Answer 23

splitting one molecule of glucose into two molecules of pyruvate. it does not require oxygen

Question 24

where does glycolysis happen ?

Answer 24

cytoplasm of cells

Question 25

What happens during glycolysis in anaerobic respiration and aerobic respiration ?

Answer 25

phosphorylation: in the cytoplasm of a cell, glucose is phosphorylated using a phosphate from atp. This creates once molecule of glucose phosphate and 1 molecule of adp. Glucose phosphate is split into 2 molecules of triose phosphate
Oxidation: Triose phosphate is oxidised by 2NAD to form 2NADH. This results in 2 molecules of pyruvate (3C) . 4 ATP molecules are produced but 2 are used up, so there is a net gain of 2.

Question 26

What happens at the end of glycolysis in anaerobic respiration ?

Answer 26

Pyruvate is converted into ethanal then ethanol (in plants and yeast) or lactate ( in animals and bacteria), using the oxidation of NADH.
The production of ethanol or lactate regenerates NAD so that glycolysis can continue.

Question 27

What happens during the link reaction of aerobic respiration ?

Answer 27

in the mitochondrial MATRIX, 2 molecules of Pyruvate is decarboxylated as one carbon atom is removed from each pyruvate in the form of (2) carbon dioxide molecules.
Pyruvate is oxidised to form 2 molecules of acetate and NAD is reduced into NADH.
Acetate is combined with co enzyme A to form 2 molecules of acetyl coenzyme A.
No ATP is produced.

Question 28

Where does the link reaction and the krebs cycle take place ?

Answer 28

mitochondrial matrix.

Question 29

what happens during the krebs cycle ?

Answer 29

Acetyl coenzyme A combines with a 4 carbon molecule to form citrate a 6 carbon molecule. Coenzyme A returns to the link reaction.
Citrate is converted into a 5C molecule and a carbon dioxide molecule is removed. NAD is reduced into NADH
The 5C molecule is converted into a 4c molecule (oxaloacetate) by removing carbon dioxide.
NAD is reduced into NADH and 2 FAD is reduced into 2 FADH.
ATP is produced by the transfer of pi to adp. this is called substrate level phosphorylation.
Citrate is converted into oxaloacetate

Question 30

What happens during oxidative phosphorylation ?

Answer 30

Energy carried by electrons from NADH AND FADH is used to make ATP.
Hydrogen atoms released by NADH and FADH dissociate into protons and electrons. electrons move down the electron transport chain loosing energy.
The energy pumps protons from the mitochondrial matrix to the intermembrane space. the concentration of protons is now higher in the intermembrane space forming an electrochemical gradient.
Protons move down the gradient into the matrix by atp synthase. This drives the synthesis of ATP from ADP and Pi. This is called chemiosmosis.
In the matrix, protons, electrons and oxygen form water. Oxygen is the final electron acceptor.

Question 31

Where does oxidative phosphorylation occur ?

Answer 31

intermembrane of the mitochondria

Question 32

what are the stages of aerobic respiration ?

Answer 32

glycolysis
link reaction
krebs cycle
oxidative phosphorylation

Question 33

how many molecules of ATP are made by NADH

Answer 33

2.5 per molecule of NADH

Question 34

How many molecules of ATP are made by FADH

Answer 34

1.5 molecules of ATP per FADH

Question 35

how many ATP molecules are made during aerobic respiration

Answer 35

32

Question 36

how can mitochondrial disease affect ATP production

Answer 36

it affects how proteins function in the krebs cycle or oxidative phosphorylation, reducing ATP production.
This may cause anaerobic respiration to occur more to make up for ATP shortage
This results in lots of lactate production which can cause muscle fatigue and weakness.
Some lactate will diffuse into the bloodstream leading to high lactate concentration in the blood

Question 37

What is the net gain of ATP during oxidative phosphorylation ?

Answer 37

28

Question 38

why is the theoretical yield of atp rarely achieved ?

Answer 38

some ATP is used up transporting pyruvate into the mitochondria
Not all H+ ions will move through ATP synthase
Some energy released in the electron transport chain is lost as heat.

Question 39

why is glucose not the only respiratory substrate ?

Answer 39

other respiratory substrates include the breakdown products of lipids and amino acids, which enter the krebs cycle.