Unit 3 Aos 2 Flashcards
1
Q
What is photosynthesis?
A
Photosynthesis is the process where photoautotrophs capture light energy from the sun and convert it into chemical energy, producing glucose and oxygen from carbon dioxide and water.
2
Q
What are photoautotrophs?
A
A: Photoautotrophs are organisms that can perform photosynthesis, such as plants, algae, and cyanobacteria.
3
Q
What are the inputs and outputs of photosynthesis?
A:
A
Inputs: Carbon dioxide (CO2) and water (H2O)
Outputs: Glucose (C6H12O6) and oxygen (O2)
4
Q
What is the primary product of photosynthesis?
A
The primary product of photosynthesis is glucose (C6H12O6).
5
Q
What are mesophyll cells in plants?
A
Mesophyll cells are the plant cells in leaves responsible for photosynthesis. They contain many chloroplasts.
6
Q
What is the function of chloroplasts?
A
Chloroplasts are organelles in plant cells where the light-dependent and light-independent stages of photosynthesis occur.
7
Q
What is the role of chlorophyll in photosynthesis?
A
Chlorophyll is a photosynthetic pigment found in the thylakoids of chloroplasts that absorbs light energy to start photosynthesis.
8
Q
What are stomata?
A
Stomata are small pores on the leaf surface that regulate the exchange of gases, allowing carbon dioxide to enter and oxygen to exit.
9
Q
What is the light-dependent stage of photosynthesis?
A
The light-dependent stage occurs in the thylakoid membranes, where light energy splits water molecules into oxygen and hydrogen, generating NADPH and ATP.
10
Q
What is the light-independent stage of photosynthesis (Calvin cycle)?
A
The light-independent stage occurs in the stroma, where carbon dioxide, NADPH, and ATP are used to form glucose.
11
Q
Where do the light-dependent reactions occur in the chloroplast?
A
The light-dependent reactions occur in the thylakoid membranes.
12
Q
What are the inputs of the light-dependent stage?
A
12 water (H2O) molecules, 12 NADP+, and 18 ADP + Pi.
13
Q
What are the outputs of the light-dependent stage?
A
6 oxygen (O2) molecules, 12 NADPH, and 18 ATP.
14
Q
What is photolysis in photosynthesis?
A
Photolysis is the process of splitting water molecules into oxygen, electrons, and hydrogen ions using light energy.
15
Q
What is the Calvin cycle?
A
The Calvin cycle is the light-independent stage of photosynthesis that uses carbon dioxide, NADPH, and ATP to produce glucose.
16
Q
What are the inputs and outputs of the light-independent stage (Calvin cycle)?
A:
A
Inputs: 6 CO2, 12 NADPH, and 18 ATP
Outputs: Glucose (C6H12O6), 6 water (H2O), 12 NADP+, and 18 ADP + Pi.
17
Q
: What is the role of NADPH and ATP in photosynthesis?
A
NADPH and ATP are coenzymes that provide the energy needed for the light-independent stage (Calvin cycle) to produce glucose.
18
Q
What is the function of ATP synthase in photosynthesis?
A
ATP synthase catalyzes the production of ATP from ADP and Pi during the light-dependent reactions.
19
Q
What is the overall chemical equation for photosynthesis?
A
6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂ (in the presence of sunlight)
20
Q
Where do the two stages of photosynthesis occur?
A
Light-dependent stage: Thylakoid membranes (grana)
Light-independent stage: Stroma
21
Q
What are the inputs and outputs of the light-dependent stage?
A
Inputs: 12 H₂O, 12 NADP⁺, 18 ADP + Pi
Outputs: 6 O₂, 12 NADPH, 18 ATP
22
Q
What are the inputs and outputs of the light-independent stage?
A
Inputs: 6 CO₂, 12 NADPH, 18 ATP
Outputs: C₆H₁₂O₆, 12 NADP⁺, 18 ADP + Pi, 6 H20
23
Q
What is photorespiration?
A
A wasteful process where Rubisco binds to O₂ instead of CO₂, reducing photosynthesis efficiency.
24
Q
What type of plants are C3 plants and what is their adaptation to photorespiration?
A
Most plants (trees, wheat, rice)
No adaptations to reduce photorespiration
25
How do C4 plants reduce photorespiration?
By separating carbon fixation and the Calvin cycle across two cells (mesophyll & bundle-sheath cells)
26
What is the enzyme used in initial CO₂ fixation in C4 and CAM plants?
PEP carboxylase (does not bind to O₂)
27
How do CAM plants reduce photorespiration?
By separating carbon fixation and the Calvin cycle over time (CO₂ fixed at night, Calvin cycle during the day).
28
What advantage do CAM plants have in arid climates?
Stomata only open at night → conserves water and minimises photorespiration.
29
What are the main disadvantages of C4 and CAM photosynthesis?
Both require more ATP than C3 photosynthesis.
30
What happens when stomata close due to water loss?
CO₂ can't enter, O₂ can't exit → photorespiration increases → photosynthesis decreases.
31
What is Rubisco and its role in photosynthesis?
Rubisco is an enzyme that catalyzes the fixation of CO₂ during the light-independent stage of photosynthesis.
32
What does "affinity" mean in a biochemical context?
The tendency of a molecule/atom to bind or react with another molecule/atom.
33
Why does low CO₂ concentration promote photorespiration?
Rubisco is more likely to bind O₂ when CO₂ is low, initiating photorespiration instead of photosynthesis.
34
How do C4 and CAM plants reduce photorespiration?
By evolving mechanisms to concentrate CO₂ around Rubisco.
35
Why is water not usually a limiting factor in photosynthesis?
Because most plants have adequate water; it only limits under extreme drought or heat.
36
What happens when plants close their stomata to conserve water?
CO₂ cannot enter, O₂ accumulates, photorespiration increases, and photosynthesis rate drops.
37
How does water loss affect C3 plants compared to C4 and CAM?
3 plants are more affected due to lack of adaptations; C4 and CAM plants are more tolerant.
38
What is an enzyme inhibitor?
A molecule that binds to and prevents an enzyme from functioning.
39
Difference between competitive and non-competitive inhibitors?
Competitive inhibitors block the active site; non-competitive inhibitors change the active site shape.
40
Can the effects of competitive inhibitors be overcome?
Yes, by increasing substrate concentration.
41
Are C3, C4, and CAM plants all affected by enzyme inhibitors?
: Yes, inhibitors impact all types equally depending on the target enzyme.
42
What is CRISPR-Cas9?
A gene-editing tool using guide RNA and the Cas9 enzyme to cut and modify DNA at specific sites.
43
How can CRISPR-Cas9 improve crop photosynthesis?
By editing genes to bypass photorespiration, enhance Rubisco, or improve chloroplast/stomata function.
44
Why is CRISPR important for agriculture’s future?
CRISPR is important for agriculture’s future because it lets scientists precisely edit plant DNA to improve crops. It can boost yield, make plants more resistant to pests and diseases, improve drought and heat tolerance, and even enhance nutrition (like adding vitamins). It’s faster and more accurate than traditional breeding, helping farmers grow more food sustainably and adapt to climate change.
45
What is cellular respiration?
Cellular respiration is a biochemical process in which cells convert glucose into ATP (adenosine triphosphate), the usable form of energy. It involves breaking down glucose through a series of reactions, and in the presence of oxygen (aerobic), it yields high amounts of ATP. The main purpose is to supply energy for cellular functions like growth, repair, and active transport.
46
What are the three main stages of aerobic cellular respiration?
Glycolysis – occurs in the cytosol; breaks glucose into pyruvate.
Krebs Cycle (Citric Acid Cycle) – occurs in the mitochondrial matrix; processes pyruvate into carbon dioxide and transfers electrons to carriers.
Electron Transport Chain (ETC) – occurs in the inner mitochondrial membrane; uses electrons to generate most of the ATP.
47
Where does glycolysis occur and what is its main function?
Location: Cytosol
Function: Breaks down one molecule of glucose (6C) into two molecules of pyruvate (3C), producing small amounts of ATP and NADH, and does not require oxygen.
48
What are the inputs of glycolysis (per glucose molecule)?
1 glucose (C₆H₁₂O₆)
2 NAD⁺ (electron carrier)
2 ADP + 2 Pi (to make ATP)
49
What are the outputs of glycolysis (per glucose molecule)?
2 pyruvate
2 NADH (to ETC)
2 ATP (net gain; 4 made, 2 used)
50
Is oxygen required for glycolysis?
No – glycolysis is anaerobic and can occur with or without oxygen.
51
What happens to pyruvate after glycolysis if oxygen is present?
Pyruvate enters the mitochondria and is converted into acetyl-CoA, releasing 1 CO₂ and producing 1 NADH per pyruvate, before entering the Krebs cycle.
52
Where does the Krebs cycle occur and what is its functio
Location: Mitochondrial matrix
Function: Completes the breakdown of glucose by oxidizing acetyl-CoA to CO₂ and transferring electrons to NAD⁺ and FAD to form NADH and FADH₂ for the ET
53
Inputs of the Krebs cycle (per glucose molecule)?
2 acetyl-CoA (from 2 pyruvate)
6 NAD⁺
2 FAD
2 ADP + 2 Pi
54
Outputs of the Krebs cycle (per glucose molecule)?
6 NADH
2 FADH₂
4 CO₂
2 ATP
55
What is the main purpose of the Krebs cycle?
To generate NADH and FADH₂ by transferring high-energy electrons, which are used in the electron transport chain to drive ATP production.
56
Where does the electron transport chain (ETC) occur?
In the inner mitochondrial membrane (folded into cristae for surface area).
57
What are the inputs of the electron transport chain (ETC)?
10 NADH (from glycolysis, pyruvate processing, and Krebs)
2 FADH₂
6 O₂ (final electron acceptor)
ADP + Pi
58
What are the outputs of the electron transport chain (ETC)?
26-28 ATP
6 H₂O (from oxygen accepting electrons and protons)
59
How does the ETC produce ATP?
Electrons from NADH and FADH₂ move through protein complexes, releasing energy to pump H⁺ ions into the intermembrane space. The H⁺ ions flow back into the matrix through ATP synthase, powering the formation of ATP from ADP + Pi (chemiosmosis).
60
What is the total ATP yield from aerobic respiration (per glucose)?
Glycolysis: 2 ATP
Krebs cycle: 2 ATP
ETC: 32–34 ATP
➡️ Total: 36–38 ATP
61
What happens to pyruvate in anaerobic conditions?
In animals: Pyruvate is converted to lactic acid, allowing NAD⁺ to be recycled for glycolysis.
In yeast/plants: Pyruvate is converted to ethanol + CO₂.
Only 2 ATP are produced (from glycolysis).
62
What role does oxygen play in the electron transport chain (ETC)
Oxygen acts as the terminal electron acceptor, binding with electrons and protons to form water, allowing the ETC to proceed.
63
How many ATP molecules are produced from one glucose in aerobic respiration?
30 - 32ATP (2 from glycolysis, 2 from the Krebs cycle, and 26 -28 from the ETC depending on NADH/FADH₂ shuttling).
63
What is ATP synthase and how does it work?
ATP synthase is an enzyme in the inner mitochondrial membrane that uses the proton (H⁺) gradient to produce ATP from ADP and Pi.
64
What happens when cyanide affects the ETC?
It inhibits a key enzyme, blocking the ETC and drastically reducing ATP production, which can lead to cell or organism death.
65
What is end-product inhibition in enzyme regulation?
The final product of a biochemical pathway inhibits an earlier step, preventing overproduction.
66
Name three coenzymes involved in cellular respiration.
NAD⁺, FAD, and ATP (cycling between loaded and unloaded forms: NADH, FADH₂, and ADP).
67
Why can't the Krebs cycle and ETC continue without oxygen?
NADH and FADH₂ can't unload electrons, so they accumulate, halting both cycles.
68
What is anaerobic fermentation in animals?
Pyruvate is converted to lactic acid, regenerating NAD⁺ for glycolysis.
69
What is anaerobic fermentation in yeasts?
Pyruvate is converted to ethanol and CO₂, also regenerating NAD⁺.
70
Why is lactic acid buildup a problem for cells?
It lowers pH, potentially denaturing enzymes and disrupting cell function.
71
Where does anaerobic fermentation occur in the cell?
In the cytosol.
72
What is the function of pyruvate kinase?
Catalyses the final step of glycolysis, producing pyruvate and ATP.
73
What are facultative anaerobes?
Organisms that can survive without oxygen but grow better with it.
74
What are the stages of aerobic cellular respiration?
Glycolysis (cytosol), Krebs cycle (mitochondrial matrix), and electron transport chain (cristae).
75
What are the stages of anaerobic fermentation?
Glycolysis followed by lactic acid fermentation (in animals) or ethanol fermentation (in yeasts).
76
What are the inputs and outputs of aerobic respiration?
Inputs: glucose and oxygen; Outputs: carbon dioxide, water, and 30–32 ATP.
77
What are the inputs and outputs of anaerobic respiration in animals and yeasts?
Animals: glucose → lactic acid + 2 ATP;
Yeasts: glucose → ethanol + CO₂ + 2 ATP.
78
Where does aerobic vs anaerobic respiration occur in cells?
Aerobic: cytosol (glycolysis) + mitochondria (Krebs and ETC);
Anaerobic: entirely in cytosol.
79
Compare ATP yield and speed of aerobic and anaerobic respiration.
Aerobic: slow but efficient (30–32 ATP);
Anaerobic: fast but inefficient (2 ATP).
80
Why can’t anaerobic respiration continue indefinitely?
Toxic accumulation of lactic acid or ethanol inhibits cell function.
81
What are the advantages of Rubisco in photosynthesis?
Rubisco allows carbon fixation by binding CO₂ to RuBP in the Calvin cycle, enabling the production of glucose and other organic molecules needed for plant growth and energy.
82
What are the disadvantages of Rubisco in photosynthesis?
Rubisco is slow and not very selective—it sometimes binds to O₂ instead of CO₂, causing photorespiration, which wastes energy and reduces photosynthetic efficiency.
83
What are the general factors that affect enzyme function in photosynthesis and cellular respiration?
Temperature, pH, substrate concentration, and the presence of competitive or non-competitive inhibitors. Each enzyme has optimal conditions where activity is highest.
84
What is the general role of enzymes and coenzymes in photosynthesis and cellular respiration?
Enzymes speed up reactions by lowering activation energy. Coenzymes (e.g. NADP+, NAD+, FAD) carry electrons and protons between reactions to enable energy transfer.
85
What is the general structure of biochemical pathways in photosynthesis and cellular respiration?
: Both involve a sequence of enzyme-controlled reactions converting an initial reactant into a final product. Photosynthesis: light-dependent stage → light-independent stage. Cellular respiration: glycolysis → Krebs cycle → electron transport chain.
86
How have C3, C4, and CAM plants adapted to maximise photosynthesis efficiency?
A: C3: Standard Calvin cycle. C4: Fix CO₂ in mesophyll, move it to bundle sheath cells to reduce photorespiration. CAM: Open stomata at night to reduce water loss, store CO₂ for daytime photosynthesis.
87
What are the potential uses of CRISPR-Cas9 in improving photosynthesis and crop yields?
A: CRISPR-Cas9 can modify genes to enhance enzyme efficiency (e.g. Rubisco), improve drought/heat tolerance, or increase CO₂ uptake, leading to better photosynthetic performance and higher yields.
88
What are the uses of anaerobic fermentation of biomass in biofuel production?
Anaerobic microbes break down biomass into ethanol or methane, which can be used as renewable biofuels. Common sources include corn, sugarcane, and agricultural waste.
89
How can CRISPR be beneficial for biofuel production?
CRISPR can boost biofuel production by editing plants or microbes to produce more fermentable sugars or oils, resist stress, and break down biomass more efficiently, leading to higher biofuel yields.
90
can Glycolysis be anerobic and aerobic?
Occurs in the cytosol and is anaerobic (does not require oxygen); it's the first stage in both aerobic and anaerobic respiration.
91
can the krebs cycle be anerobic and aerobic
Occurs in the mitochondrial matrix and is aerobic (requires oxygen indirectly via NAD⁺/FAD regeneration).
92
can the Electron Transport Chain (ETC)be anerobic and aerobic
Occurs on the inner mitochondrial membrane and is strictly aerobic, as it requires oxygen as the final electron acceptor.
93
What role does malate play in C4 and CAM plants?
Malate is a 4-carbon compound used by C4 and CAM plants to capture and store CO₂. It is later transported to the Calvin cycle, where it is broken down to release CO₂ for photosynthesis, improving efficiency in hot or dry environments.
94
How do C4 and CAM plants differ from C3 plants in delivering carbon to the Calvin cycle?
C4 and CAM plants convert CO₂ into malate, which is later broken down to release CO₂ for the Calvin cycle, increasing efficiency in hot, dry conditions. C3 plants directly use CO₂ in the Calvin cycle without using malate.
95
What is the chemical equation for aerobic respiration
C6H12O6 +6 O2 ——>6 CO2+ 6 H2O
96
what are the strengths and weaknesses of biofuel
Strengths - Reduced dependence on fossil fuels:
Biofuels can lower demand for oil, contributing to more stable fuel prices.
Environmental benefits:
Biofuels can have lower carbon dioxide and sulfur emissions compared to fossil fuels, making them more environmentally friendly.
Economic opportunities:
Biofuel production can provide income for farmers, stimulate local economies, and create jobs in rural areas.
Renewable and sustainable:
Biofuels are derived from renewable sources like biomass, making them a more sustainable alternative to fossil fuels.
Energy security:
Domestic biofuel production can increase energy security by reducing reliance on foreign oil imports.
Weaknesses Environmental concerns:
Biofuel production can lead to deforestation, land degradation, and loss of biodiversity, especially if not managed sustainably.
Competition with food production:
Growing crops for biofuels can compete with land and resources needed for food production, potentially raising food prices.
Production costs and efficiency:
Biofuel production can be more expensive and less energy-efficient than traditional fossil fuels, especially for certain types like ethanol.
Infrastructure and market challenges:
Developing the necessary infrastructure for biofuel production and establishing a market for biofuels can be costly and time-consuming.
Equity and gender concerns:
Biofuel production can disproportionately affect certain communities, particularly small-scale farmers and women, who may face land displacement or resource conflicts
