Topic 5.1 - Photosynthesis and Respiration Flashcards
1
Q
Define ATP
A
Immediate source of energy in a cell to fuel biological processes
2
Q
What is an ATP molecule made of?
A
- Ribose sugar
- Adenine base
- Phosphate group
3
Q
Define ATP synthase
A
The enzyme which catalyses the condensation reaction (synthesis) of ATP from ADP and Pi
4
Q
Define ATP hydrolase
A
The enzyme which catalyses the hydrolysis reaction of ATP into ADP and Pi
5
Q
Define phosphorylation
A
The process of adding a phosphate group to a molecule
6
Q
What are ATPs six properties?
A
1) ATP stores and releases small, manageable amounts of energy so none is wasted (e.g. as heat)
2) Easily transported around the cell as it small and soluble
3) Energy released instantaneously as it is easily broken down
4) Quickly remade
5) Pi is used to phosphorylate other compounds to make them more reactive
6) Immediate supply of energy as ATP is unable to pass out of the cell
7
Q
What is the reaction for photosynthesis?
A
Carbon dioxide + water > glucose + oxygen
6CO2 + 6H2O > C6H1206 + 6O2
8
Q
Define photoautroph
A
- Organisms that carry out photosynthesis
- Synthesise their own glucose from inorganic substances by transferring light energy
- e.g. green plants (chlorophyll)
photosynthetic bacteria
algae
9
Q
Define photosynthesis
A
A metabolic pathway whereby a series of small enzyme controlled reactions produce glucose and oxygen from carbon dioxide and water by transferring energy from light
10
Q
What is the function of a chloroplast?
Name components of the chloroplast and state their functions
A
- Chloroplast = where photosynthesis takes place
- Thylakoid = fluid filled sacs
= membrane contains chlorophyll
= whereby light-dependent reactions to occur - Granum = stacks of thylakoid
= linked together by lamellae - Lamellae = Extensions of the thylakoid membrane
= joins grana together
Stroma = thick gel-like fluid containing enzymes, organic acids and sugars
= whereby light-independent reaction takes place
Starch grain = where carbohydrates produced by photosynthesis are stored
Double membrane = controls movement of substances in and out of the chloroplast
11
Q
What do chloroplasts contain?
A
Photosynthetic pigments (colours substances absorb light energy for photosynthesis)
12
Q
What are the three photosynthetic pigments?
Where are they found?
How do they make photsystems?
A
- Chlorophyll a
- Chlorophyll b
- Carotene
All found in thylakoid membrane
Pigments + proteins = photosystems
13
Q
What is the function of chlorophyll a?
A
Converts light energy into chemical energy
14
Q
What is the function of chlorophyll b?
A
Absorbs light energy and conveyed to chlorophyll a
15
Q
What is the function of carotene?
A
Absorbs light energy and transports it to chlorophyll a
16
Q
What light colours do all the photosynthetic pigments absorb?
A
Chlorophyll a/b = blue and red regions of spectrum
Carotene = all other regions on spectrum
17
Q
Define oxidation
A
- Loss of electrons
- Loss of hydrogen
- Gain of oxygen
18
Q
Define reduction
A
- Gain of electrons
- Gain of hydrogen
- Loss of oxygen
19
Q
Define dehydrogenation
A
Removal of hydrogen from a molecule
20
Q
Define photolysis
A
Splitting of a molecule using light energy
21
Q
Define co-enzymes
A
- Molecules that aid the function of an enzyme
- Transfer a chemical group from one molecule to another
22
Q
What is the electron transfer chain (ETC)?
A
- Where excited electrons flow via electron carriers (proteins) that transfer electrons from PSII to PSI
- As electrons move down ETC, they lose energy
23
Q
Define electron carriers
A
Proteins that transfer electrons
24
Q
What is the cytochrome?
A
Where redox reactions occur in the electron transfer chain
25
Define photoionisation
The process of turning an atom/molecule into an ion (by losing or gaining electrons) using light energy
26
Define photophosphorylation
The process of adding a phosphate group to a molecule using light energy
27
Describe the process of non cyclic phosphorylation
1) Light energy (photons) are absorbed by the chlorophyll in PSII.
The light excites the electrons to move to a higher energy level in the chlorophyll PSIl.
2) These high energy electrons are released from the chlorophyll in PSII and move down the electron transport chain to PSI
As excited electrons have been lost from chlorophyll in PSII , there is the oxidation of chlorophyll in PSII.
Chlorophyll in PSII becomes positively charged.
These excited electrons must be replaced.
3) Photolysis of water produces protons (H+), electrons and oxygen
H20 → 2H+ + 1/2 02
4) The excited electrons lose energy as they move down the electron transport chain: The energy is used to transport
protons (H+ ions) into the thylakoid. This makes a higher concentration of H+ in
the thylakoid, then the stroma.
This creates a proton gradient across the thylakoid membrane.
5) Protons (H+) move down concentration gradient via ATP synthase embedded in the thylakoid membrane, into the stroma. 6) The energy from this movement forms ATP (chemiosmotic theory) by combining ADP and Pi.
7) Light energy is absorbed by PSI, which: excites the electrons to an even higher energy level in PSI
8) Electrons and protons are transferred to NADP so it is reduced to NADPH
28
Define chemiosmosis
The movement of electrons across a partially permeable membrane down the electron transport chain (electrochemical gradient) to ATP synthesis
29
Describe the process of the Calvin cycle/light independent reaction
1) Carboxylation
- CO2 enters the leaf through the stomata (from atmosphere) and diffuses into the stroma
- Combines with ribulose biphosphate, RuBP, (5C)
- Catalysed by enzyme, Rubisco
- Creates an unstable 6 carbon molecule
- Quickly splits into 2x glycerate 3-phosphate (GP) molecules (3C)
2) Reduction
- Hydrolysis of ATP into ADP and Pi
- Provides energy to reduce GP (3C) into TP (triose phosphate) (3C)
- NADPH loses a hydrogen to form NADP and H+
3) Regeneration
- NADP is recycled
- I out of 6 TP is converted into useful organic compounds (eg glucose)
- 5 out of 6 TP molecules are used regenerate the RuBP
30
What are GP and TP used to make?
- Larger carbohydrates > Sucrose
> Starch
> Cellulose
= made by joining hexose sugars in different ways
- Lipids > Synthesis of TP and fatty acids to make glycerol
- Amino acids > Made from GP
- Glucose > Respiration
31
What are the optimum conditions for photosynthesis?
1) High light intensity
- Of certain wavelengths (red and blue light)
- Higher light intensity = more ATP provided by the light - dependent reaction
2) Temperature (around 25°C)
- Optimum for enzyme action
- High = enzymes will denature
= stomata will close to conserve water and less CO2 enters
- Low = enzymes will become inactive
3) Carbon dioxide concentration (0.4%)
- Carbon dioxide available to combine with RuBP during Calvin cycle
- High = causes stomata to close
4) Water
- Plants need a constant supply of water
- High = soil becones waterlogged
= Reduces uptake of minerals needed to make chlorophyll a
= Less oxygen in waterlogged soil
= less aerobic respiration
= Less ATP for active transport
- Low = Little photosynthesis
= photolysis of water is limited
32
Define limiting factor
A variable that can slow down the rate of reaction
33
Define saturation point
- Where a factor is no longer limiting the reaction
- Where the graph plateaus
34
Why do farmers use greenhouses?
To increase growth/yield of crops
35
What do farmers do to maintain carbon dioxide concentration in greenhouse?
CO2 added to air by burning a small amount of propane in a carbon dioxide generator
36
What do farmers do to maintain light intensity in greenhouse?
- Light can get through glass
- Artificial lights / lamps (red and blue) to provide light even at night
37
What do farmers do to maintain temperature in greenhouse?
- Traps heat energy from sunlight, which warms air
- Heating / cooling systems
- Air circulation systems make sure the temperature is even throughout the glasshouse
38
Define respiration
The process whereby energy stores in complex organic molecules (carbohydrates, fats and proteins), is used to make ATP in living cells
39
What are the two types of respiration?
- Aerobic respiration = requires oxygen
= slow (produces more ATP)
- Anaerobic respiration = does not require oxygen
= fast (produces less ATP)
40
What so the equation for aerobic respiration?
Glucose + oxygen > carbon dioxide + water
C6H12O6 + 6O2 > 6CO2 + 6H2O
41
What is the formula for anaerobic respiration in animals?
Glucose > lactic acid/ lactate
42
What is the formula for anaerobic respiration in plants / yeast?
Glucose > ethanol + carbon dioxide
43
What are seven examples of metabolic processes that require ATP?
- Synthesis of organelles (G1 phase)
- Activation of chemicals (GP and TP)
- DNA replication
- Movement (muscles and flagella)
- Active transport
- Endocytosis
- Secretion
44
What is the structure of the mitochondria?
What are the functions of each of the structures?
- Cristae (folds) > Provides a large surface area
> Maximises respiration
- Matrix > Contains digestive enzymes involved in respiration
45
What do special about glycolysis stage?
- First stage of aerobic and anaerobic respiration
46
Where does glycolysis take place?
- Occurs in cells cytoplasm
- Glucose is too large to cross outer mitochondrial membrane
47
Describe the process is glycolysis
1) Phosphorylation
- ATP is hydrolysed
- Glucose is phosphorylated to make glucose biphosphate
- The energy from ATP is now in the new molecule.
The new molecule is high in energy and highly reactive
- Splits into 2x molecules of triose phosphate (TP) (3c)
2) Oxidation
- Both molecules of triose phosphate become oxidised
- Forms two molecules of pyrurate (3C)
- Hydrogen is added to NAD forming two NADH (reduced NAD)
48
What are the equations to show how NAD is constantly produced from pyruvate?
Why is a continuous production of NAD important?
Animals:
Pyruvate > lactate
Plants and yeast:
Pyruvate > ethanal + carbon dioxide > ethanol
NAD is recycled back to react with pyruvate a continuous cycle of glycolysis. This is because lactate / ethanol regenerates oxidised NAD
49
Where does the link reaction take place?
- Mitochondrial matrix
- occurs twice per glucose molecule (for each private molecule)
50
Describe the process of the link reaction
1) The pyruvate (3C) enters mitochondria by active transport from glycolysis.
It is oxidised to acetate (2C) by pyruvate dehydrogenase (enzyme)
2) The hydrogen is used to reduce NAD to NADH
3) Pyruvate is decarboxylated to remove l carbon to make carbon dioxide
4) Acetate (2C) is combined with coenzyme A (CoA) to make acetyl coenzyme A (used to get the acetate into the next stage)
51
Where does the krebs cycle take place?
- Mitochondrial matrix
- Happens twice per glucose molecule (for each pyruvate)
52
Describe the process of the krebs cycle
1) Acetyl-coenzyme A (2C) combines with oxaloacetate (4C) to form a citrate (6C).
Coenzyme A goes back to the link reaction
2) The citrate (6C) undergoes decarboxylation and dehydrogenation
NAD reduced to NADH
CO2 (1C) produced
Formation of a 5 carbon molecule.
3) Another dehydrogenation reaction (NAD reduced to NADH and FAD reduced to FADH2).
Another decarboxylation reaction producing CO2 (1C).
4) Substrate level phosphorylation: Pi directly transferred to ADP to make ATP.
5) Citrate has now been converted into oxaloacetate through a series of redox reactions
53
What can fatty acids be converted to enter Krebs cycle?
Fatty acids > acetylcoenzyme A
54
What can amino acids be converted to enter Krebs cycle?
Amino acids are deaminated and rest can enter Krebs cycle
Amino acids > pyruvate or acetate
55
Where does oxidative phosphorylation take place?
Cristae in mitochondria
56
Why is the cristae folded?
To increase surface area for oxidative phosphorylation
57
Describe the process of oxidative phosphorylation
1) Reduced coenzymes (NADH and FADH2) release their hydrogen atoms as they are oxidised to NAD and FAD
2) Hydrogen atoms split to produce protons (H+) and electrons
3) Electron carriers accept electrons from reduced NADH and FADH2
4) The electrons move from each electron carrier protein, in a series of redox reactions, down the electron transport chain, releasing energy
5) The energy released is used to pump protons from the mitochondrial matrix across the inner mitochondrial membrane, into inner membrane space.
This is called chemiosmosis
6) The concentration of protons in the inner membrane space becomes higher than in the mitochondrial matrix.
This forms an electrochemical gradient
7) Protons move down the electrochemical gradient, back across
the inner mitochondrial membrane via ATP synthase that spans the membrane.
8) Embedded in the inner mitochondrial membrane, there are ADP and Pi.
The flow of protons down the gradient, drives the synthesis of ATP.
ADP + Pi join in a phosphorylation reaction, forming ATP.
9) At the end of the transfer chain, the protons join up with electrons and the final electron acceptor, oxygen (from blood), to form waterz
58
Define mitochondrial disease
Affects the functioning of the mitochondria by affecting proteins involved in oxidative phosphorylation, reducing ATP production
59
Why do mitochondrial diseases cause anaerobic respiration?
What are the affects of this?
Mitochondrial diseases may cause anaerobic respiration to try to make up for ATP shortage. This results in a lot of lactate being produced, which can cause muscle fatigue and weakness.
Some lactate will also diffuse into the bloodstream, leading to a high lactate concentration in the blood
60
How experiments can you use to measure oxygen consumption?
- Monometer
- Respirometer
61
Define compensation point
The point at which the rate of photosynthesis in a plant, matches its rate of respiration
