Pack 16 - Photosynthesis and Respiration Flashcards
1
Q
Where does photosynthesis take place? (Organ and organelle)
A
The chloroplasts in the leaf (mostly.)
2
Q
What adaptations does the leaf have to bring together the raw component of photosynthesis and take away its products? Explain each one. (9)
A
- Large surface are of leaf to absorb light.
- Arrangement of leaves on the plant that avoids overlapping.
- Thin - short diffusion distance and most light is absorbed in the first few micrometers of the leaf.
- Transparent cuticle and epidermis - let light through to mesophyll.
- Long narrow upper mesophyll packed with chloroplasts.
- Numerous stomata - gas exchange, short diffusion distance to all mesophyll cells.
- Stomata open and close in response to light intensity.
- Air spaces in lower mesophyll - rapid diffusion of CO2 and O2
- Network of xylem that brings water to leaf and phloem that carry away sugars.
3
Q
Overall equation of photosynthesis.
A
Carbon dioxide + water +(light)—-> glucose + oxygen
4
Q
What are the three main stages of photosynthesis?
A
- Capturing of light energy by chlorophyll.
- Light dependent reaction.
- Light independent reaction.
5
Q
What are the products of the light dependent reaction? (3)
A
Reduced NADP, ATP, oxygen.
6
Q
What components are needed for the light dependent reaction? (4)
A
Water, photons from light, NADP, ADP (Pi)
7
Q
What is the size of a chloroplast?
A
2-10μm
8
Q
What kind of membrane do chloroplasts have?
A
Double
9
Q
Where does the light dependent reaction take place?
A
The membrane of the thylakoids.
10
Q
What is the inside of the thylakoid called?
A
lumen
11
Q
Where does the light independent reaction take place?
A
The stroma of the chloroplast.
12
Q
What is a grana?
A
A stack of thylakoids.
13
Q
What are the three purposes of the light independent reaction?
A
- To phosphorylate ATD into ATP
- To photolysis water into H+ and electrons.
- To reduce NADP
14
Q
Give three definitions of oxidation?
A
- Loss of Hydrogen
- gain of oxygen
- loss of electrons.
15
Q
Give three definitions of reduction?
A
- gain of Hydrogen
- loss of oxygen
- gain of electrons.
16
Q
Which gives out energy and which takes energy in? Oxidation and reduction.
A
Oxidation gives out energy. Reduction takes it in. (They always take place together)
17
Q
What happens when a chlorophyll molecules absorbs light energy?
A
It increases the energy levels of a pair of electrons. Excites them.
18
Q
What happens to electrons in chlorophyll when they are excited?
A
They leave the molecule.
19
Q
What is the process of electrons leaving chlorophyll called?
A
Photoionisation
20
Q
What molecule takes up electrons that leave chlorophyll? What state are these molecules now in?
A
Electron carrier. Reduced.
21
Q
Where is the electron carrier transfer chain located?
A
Thylakoid membrane.
22
Q
What is different about each new electron carrier in the chain? What does this mean for the electrons?
A
- It is at a slightly lower energy level.
* They lose energy at each stage.
23
Q
What is chemiosmosis?
A
The movement of ions across a selectively permeable membrane bound structure, down their electrochemical gradient.
24
Q
How is ATP produced during the light dependent reaction? (only briefly/name of mechanism) (3)
A
- Chemiosmotic theory
- High H+ con inside lumen of thylakoid.
- Move down concentration gradient through ATP synthase channel into stroma.
25
How is the H+ ion concentration increased in the lumen of the thylakoid? (3)
* H+ ions produced by photolysis of water.
* H+ ions are pumped into the thylakoid lumen
* Using energy from electrons travelling through electron carriers.
26
Where does the energy used to move H+ ions into the lumen come from?
Electrons from photolysis of water - electrons released from chlorophyll by light energy.
27
In the chloroplast, where is the H+ ion concentration greatest?
inside the lumen of the thylakoids.
28
Why do H+ ions move out of the lumen of the thylakoid? Where is the the only place H+ can leave the lumen?
* Down a concentration gradient of protons.
| * ATP synthase channel.
29
What happens when H+ ions pass through the ATP synthase channel?
• Phosphorylation of ADP to form ATP.
30
Give the equation for the photolysis of water. What happens to each of the products of this reaction?
* 2H₂O --> 4H⁺ + 4e⁻ + O₂
* Protons increase the concentration inside the lumen (powering ATP synthase)
* electrons replace the lost from chlorophyll
* Oxygen used in respiration or diffuses out.
31
How are electrons replaced in the chlorophyll?
Photolysis of water
32
What is photolysis of water?
Splitting of water using light energy.
33
What molecule takes up H+ ions that have left the lumen of the thylakoid and are in the storm?
NADP
34
What happens to NADP as a result of the light dependent reaction?
Reduced - takes up electrons and H+
35
Give 4 ways the chloroplasts are adapted to their function.
* Thylakoid membrane - large SA for chlorophyll and electron carriers.
* Network of proteins in the grana hold chlorophyll in a precise manner to allow maximum light absorption.
* Granal membranes have ATP synthase channels and are selectively permeable to allow concentration gradient of H+
* Contain DNA and ribosomes for rapid manufacture of proteins involved in light dependent reaction.
36
What is the light independent reaction also known as?
Calvin cycle
37
Why does the light independent indirectly require light still?
It requires the products of the light dependent reaction.
38
Give the 6 steps of the Calvin cycle.
1. In the stroma, CO₂ reacts with ribulose bisphosphate (RuBP) catalysed by rubisco (ribulose bisphosphate carboxylase).
2. Produces 2x glycerate 3-phosphate (GP)
3. Reduced NADP reduces GP to triose phosphate (TP) using energy from ATP
4. NADP is reformed and returns to light dependent reaction.
5. Some triose phosphate is converted to useful organic substances e.g. starch, cellulose, glucose
6. Most TP used to regenerate RuBP using ATP.
39
How does CO₂ needed in the Calvin cycle get into the chloroplasts? (4)
* diffuses into the leaf through stomata
* dissolves in water around the mesophyll cells.
* Diffuses across CSM
* Into chloroplasts.
40
What are reduced NADP and ATP from the light dependent reaction used to do in the Calvin cycle?
* NADP reduces GP to TP
| * ATP provides energy for this and for reformation of RuBP
41
How many carbons does each molecules in the carbon cycle have?
* Triose phosphate - 3 (SUGAR)
* Glycerate 3-phosphate - 3 (ACID)
* RuBP - 5
42
What enzyme is used to form Glycerate 3 phosphate?
• Rubisco
43
Give three ways the chloroplast is adapted for the light independent reaction.
* Fluid of storm contains all necessary enzymes. Stoma has high concentration of enzymes and substrates.
* Stroma surrounds grana so products of light depended reaction can easily diffuse.
* DNA and ribosomes - easily manufacture proteins needed.
44
What are the two types of respiration? Give the simplified word equations (3) for each. What differs in terms of energy supplied to the cell?
Aerobic: Oxygen + Glucose --> Carbon dioxide + water
Much ATP phosphorylated
Aerobic: Glucose --> Lactate (animals)
Glucose --> Ethanol + Carbon dioxide (plants and yeast)
Little ATP produced
45
Give the 4 stages of aerobic respiration.
1. Glycolysis
2. Link Reaction
3. Krebs cycle
4. oxidative phosphorylation
46
Where does glycolysis take place?
Cytoplasm of the cell
47
Describe glycolysis in 4 steps. Name all molecules involved and the amount of carbons in each molecule.
1. Phosphorylation of glucose to glucose phosphate making it more reactive. The energy and 2 phosphsate ions come from hydrolysis of two ATP molecules (producing 2ADP).
2. Each glucose phosphate is split into two 3-carbon triose phosphate molecules.
3. Oxidation of triose phosphate - hydrogen is removed from each of the two triose phosphates and transferred to NAD to produce reduced NAD.
4. Production of ATP - each triose phosphate --> pyruvate (3C). Two ATP are formed from EACH TP.
48
What happens to glucose when it is phosphorylated? ie. what is the purpose of adding phosphate?
To make it more reactive - lowers activation energy for the following enzyme controlled reactions.
49
What is the OVERALL yield from the glycolysis of one glucose molecule?
* 2 pyruvate
* 2 ATP (4 produced -two used in phosphorylation of glucose)
* 2 reduced NAD
50
Why is glycolysis an indirect evidence for evolution?
All living organisms use it.
51
Where does the link reaction and Krebs cycle take place in eukaryotes?
Inside the mitochondrial matrix
52
What happens to pyruvate after glycolysis?
Actively transported into mitochondrial matrix
53
Describe the link reaction in 2 steps. Name all molecules involved and amounts of carbon
* Pyruvate is oxidised to acetate (2C). - CO₂ reduced and 1 NAD reduced (per pyruvate).
* Acetate combines with coenzyme A to produce acetylcoenzyme A
54
Give an overall word equation for the link reaction.
pyruvate + NAD + CoA --> acetyl CoA + reduced NAD + CO₂
55
What types of reaction take place during the Krebs cycle?
Reduction and Oxidation.
56
Describe the Krebs Cycle in 3 steps. Give the numbers of carbons.
* Acetylecoenzyme A (2C) joins with a 4C molecule to form a 6C molecule.
* 6C loses 2 carbons as 2CO₂ to form the 4C molecule.
* During this process 3 NADs are reduced 1 FAD is reduced and one ATP produced.
57
what is substrate level phosphorylation?
ATP is produced by direct transfer of phosphate from an intermediate. ie. not by ATP synthase and ETC
58
For each molecule of pyruvate how many CO₂, reduced NAD, reduced FAD and ATP are produced? Hence how many for each glucose molecule? (During the link reaction and Krebs cycle)
Link reaction - 1 CO₂, 1 reduced NAD
Krebs - 3 reduced NAD, 1 reduced FAD, 1 ATP, CO₂
x2 since 1 glucose makes 2 pyruvate
59
What is a coenzyme?
* NOT enzymes.
| * Molecules that some enzymes require to function.
60
What do the coenzymes in respiration and photosynthesis carry? Give three examples
Hydrogen
• NAD
• NADP
• FAD
61
Give 4 reasons why the Krebs Cycle is important?
* Breaks down macromolecules into smaller ones - pyruvate into carbon dioxide.
* Produces hydrogen atoms carried by NAD to the ETC to provide energy for oxidative phosphorylation and hence production of ATP
* Regenerates 4-carbon molecule that combines with acetyl coenzyme A, which would otherwise accumulate.
* Source of intermediate compounds used by cells to manufacture substances such as fatty acids, chlorophyll and amino acids.
62
Describe the structure of mitochondrion. What does the matrix contain?
Outer membrane
inner membrane forming folded to from Cristae
Matrix - proteins lipids and traces of DNA
63
Where is there a high concentration of mitochondria?
Metabolically active cells e.g. epithelial, liver and muscles.
64
What is oxidative phosphorylation? (brief)
Synthesis of ATP using electron carries and ATP synthase channel.
65
Describe oxidative phosphorylation in 5 steps.
* reduced NAD and FAD donate electrons of the H atoms they're carrying to the first molecule in the electron transfer chain.
* Electrons pass along a series of electron transfer carriers in a series of oxidation-reduction reactions.
* Electrons release energy causing active transport of protons into the inter membrane space.
* Protons accumulate in the inter membrane space before diffusing back into the matrix through ATP synthase.
* At the end of the chain electrons join with H+ ions and oxygen to form water.
66
What is the electron transfer chain?
A series of electron carriers along which electrons flow in the inner membrane of the mitochondria.
67
Why is oxygen essential for respiration?
The final electron acceptor. They join oxygen to form water. Oxygen is needed or electrons won't flow chain will 'back up'.
68
What is the importance of the inter-membrane space in mitochondria?
• Allows a high proton gradient creating a electrochemical gradient powering ATP synthase.
69
How does the flow of protons through ATP synthase produce ATP?
Changes the shape in the enzyme
70
What is oxidative phosphorylation an example of?
Chemiosmotic theory
71
Why is it useful for energy to be released more gradually? How is this achieved during respiration?
* Less energy is lost as heat.
| * Series of electron carriers - each at a slightly lower energy level. Electrons move down an energy gradient.
72
Other than sugars what molecules may be used in respiration without being first converted to carbohydrates?
• Lipids and protein
73
Describe the respiration of lipids. (3)
* Hydrolysed into glycerol and fatty acids.
* glycerol is converted to triose phosphate (enters here - glycolysis)
* Fatty acid is broken into 2 carbon fragments converted to acetyl coenzyme A (enters here- Krebs)
74
Why do lipids produce more than double the energy of the same mass of carbohydrates?
Many hydrogen atoms released during hydrolysis of lipids that are used in oxidative phosphorylation to produce ATP.
75
Describe respiration of proteins.
* hydrolysed to amino acids.
* deamination of amino acids (amine group removed)
* Enteres respiration at different points depending on the number of carbons.
76
How do electrons move down the ETC?
Down an energy gradient. Energy is lost gradually.
77
What is a similar process to oxidative phosphorylation in photosynthesis? (ATP production)
Photophosphorylation - in the light dependent stage
78
Which part of aerobic respiration can continue without oxygen? Why would it not be able to continue however without anaerobic respiration?
* glycolysis
* There would be no NAD to become reduced as it is all already reduced and can't be oxidised beach ETC is backed up due to lack of oxygen.
79
Why can't the Krebs cycle or oxidative phosphorylation continue without oxygen?
* ETC is backed up
* All FAD and NAD is reduced.
* No FAD or NAD available for Krebs.
80
In eukaryotes what two types of anaerobic respiration happen?
* Plants and yeast - pyruvate is converted to ethanol and CO₂
* Animals - pyruvate is converted to lactate.
81
Where might anaerobic respiration take place in plants?
In water logged roots.
82
Give the word equation of anaerobic respiration in yeast and plants. (include NAD)
pyruvate + reduced NAD --> ethanol + CO₂ + oxidised NAD
83
In anaerobic respiration why is it important that NAD is oxidised during the production of lactate/ethanol?
To provide more oxidised NAD for glycolysis.
84
When might animals used anaerobic respiration? (3)
* Strenuous exercise
* New born mammal
* Underwater
85
What is the electron acceptor from reduced NAD in anaerobic respiration?
pyruvate takes up two H atoms from NAD to oxidise it
86
Give the word equation of anaerobic respiration in animals. (include NAD)
pyruvate + reduced NAD --> lactate + oxidised NAD
87
What needs to happen to lactate after it has been produced? (2)
oxidised when oxygen is available again
| taken to liver to be converted to glycogen
88
What does the accumulation of lactate cause? (2)
Muscle cramps/fatigue, changes pH affecting enzymes
89
Give the two ways ATP is produced during cellular respiration and when they occur.
* oxidative phosphorylation - ETC
| * substrate level phosphorylation - Krebs and glycolysis
90
How much ATP is produced from anaerobic and aerobic respiration?
* 2 from anaerobic
| * about 36-38 from aerobic
