Exam Review Flashcards
1
Q
How did methanogens form haze?
A
- high temp -> intensified water cycle -> Co2 out of the atmosphere -> enhanced weathering of rocks and reduced CO2 level while methanogen raised the methane level
- The production of methane formed hydrocarbons -> created haze -> limited sunlight reaching the earth -> lower temp -> reduced methane production
1
Q
Describe the composition of early earth’s atmosphere
A
- toxic
- anaerobic
- rich in hydrogen, methane and ammonia
2
Q
Why did CO2 levels drop while CH4 levels rose?
A
Methanogens sing CO2 to produce methane
3
Q
Why didn’t O2 start to accumulate in the atmosphere right after the emergence of Cyanobacteria?
A
Oxygen was bound up with ions in the earth’s crust
4
Q
Why did CH4 levels drop when O2 levels rose?
A
Methanogens are anaerobic and oxygen kills methanogens
5
Q
Why did CO2 levels drop while O2 levels rose?
A
Co2 was photosynthesized to O2
6
Q
What occurred in the atmosphere when O2 rose?
A
There was sufficient oxygen to produce an ozone shield to protect against UV radiation
7
Q
Describe a methanogen:
A
- similar to bacteria
- Archaea
- produce methane from hydrogen and CO2
- anaerobic
8
Q
What type of autotrough is Purple Sulfer Bacteria and what type of photosynthesis does it use?
A
- Photosynthetic autotrough
- uses anaerobic photosynthesis to reduce carbonn to carbohydrate without releasing oxygen
9
Q
Describe Anoxygenic Photosynthesis and its rxn
A
Hydrogen sulfide plays the role of water in photosynthesis
CO2 + 2H2S -> CH2O + S2 + H2O
10
Q
Describe rxn of oxygenic photosynthesis
A
6CO2 + 6H2O -> C6H12O6 + 6O2
11
Q
What type of autotrough is cyanobacteria and what type of photosynthesis does it preform?
A
- Photosynthetic autotrough
- oxygenic photosynthesis
- heterocyts of cyanobacteria are specialized sites for nitrogen fixation
12
Q
What is the endosybiotic theory and what organelles arose by this mechanism?
A
Some organellles in eukaryotic cells were due to engulphed bacteria
- mitochondria and chloroplasts are said to have arose through this mechanism
13
Q
What is photosynthesis?
A
The process by which light energy is converted to chemical energy
14
Q
How is magnesium involved in photosynthesis?
A
It carries electrons involved in photosynthesis. Absorbs light energy.
15
Q
Describe the steps in light rxns
A
- Chlorophylls and cartenoids harvest and transfer light energy to chlorophylls at the rxn center
- Water is split and electrons at P680 of PSII are excited and become reductant
- Excited electron is then transported through the ETC and proton motive force drives ATP production and plastocyanin is transported to P700
- Electrons are excited again and used to produce NADPH
16
Q
Where do light rxns occur?
A
The thylakoid membrane
17
Q
What is chemiosmotic phosporylation?
A
Protons flow through ATP synthase channels which powers phosphorylation of ADP to ATP
18
Q
Non-cyclic electron transport is…
A
water -> NADPH
19
Q
Cyclic Electron Transport is only carried out by…
A
PSI
20
Q
Light dependant rxns of the photosystem occur in the ___ where as light independant rxns occur in the ___
A
Thylakoids/thylakoid membrane, Stroma
21
Q
What are the 3 stage of the Calvin Cycle?
A
- Carboxylation:
Add 3x CO2 to 3x RuBP = 6x 3-[hosphoglycerate
Catalyzed by RuBP carboxylase - Reduction:
6x PGA (3C) reduced to 6x glyceraldehyde 3-phosphate (G3P, 3C) - Regeneration
5x G3P (3C) used to recreate 3x RuBP (5C) so cycle can continue, while 1x G3P (3C) is released
22
Q
Where does the Calvin cycle occur?
A
In the stroma
23
Q
What is the carbon acceptor molecule in the Calvin Cycle?
A
Ribulose Bisphosphate (RuBP)
24
What 2 functions does RuBP carboxylase have?
Carboxylase and oxygenase functions.
25
What is Rubisco activase
- removes bound substrate (RuBP) from inactive enzyme
26
What is photorespiration?
The glycolate is then decarboxylated to release CO2, making photosynthesis less efficient.
27
Describe C3 Plants
- least efficient photosynthesis
- leads to water loss
- leads to photorespiration
Ex. Soybean
28
Describe C4 Plants
- Posses kranz anatomy
- Mesophyll cells around bundle sheath, consisting of large cells contining large chloroplasts
- Carbon fixation occurs in the mesophyll
- Calvin cycle occurs in the bundle sheath cells
Ex. Corn
29
Describe CAM plants
Adapted carbon rxn to separate initial carboxylation rxn from calvin cycle. Stomata open at night
Ex. pinapple and orchid
30
What is the difference between CAM plants and C4 plants
- the C4 pathway is seperated in space
- the CAM pathway is seperated in time
31
What is the end product of photosynthesis?
Sucrose
32
Describe anaerobic respiration (fermentation)
- no oxygen
- pyruvate as an electron acceptor
33
Aerobic respiration
- oxygen is the terminal electron acceptor
34
What are the 5 stages of respiration and where do they occur?
1. Glycolysis - cytoplasm
2. formation of acetyl-CoA - matrix
3. Krebs cycle - matrix
4. ETC - cristae in inner membrane
5. Chemiosmosis and oxidative phosphorylation - cristae in inner membrane
35
For each glucose how much ATP, NADH, and FADH2 are produced?
4 ATP
8 NADH
2 FADH2
36
What is the Pentose Pathway?
Nitrate is produced to amino acids and produces ribose and erthrose sugar as well as NADPH
37
What is thermogenic respiration?
- Cyanode resistant repiration
- Pathway bypasses complex III and IV and dissipates energy as heat
- no ATP formed
38
what is ROSis triggered by
different types of stresses
39
Describe a taproot
contains a main root that grows deep into soil
40
describe fibrous roots
shorter roots that stay close to the surface
41
What is plasmolysis
- loss of turgor leading to the detachment of the protoplast from the cell wall
- driven. by the vacuole
42
Describe Active Transport
Cells regulate the exchange if materials with the environment via the plasma membrane
43
What is a Halophyte?
- a salt tolerant plant
Ex. saltwater cress, sea lavender, salt bush
44
What is Apoplastic Transport
Transport through non-living parts of the cell (cell walls and intracellular spaces)
45
What is symplastic transport?
The movement of water from one cell to another cell by plasmodesmata through living parts of the cell
46
What are aquaporins?
Specialized water channel that facilitates movement of water across biological membranes
- passive transport
47
What is transmembrane transport
cell -> cell
48
How is Aquaporin activity regulated
1. Transcriptional Regulation: blue light, ABA, GA enhance expressoin of aquaporins in various tissues
2. Post-transcriptional Regulation: Aquaporins can be regulated by protein phosphorylation
49
How does the stomata open?
- K+ is taken up into guard cells/ vaccuoles from surrounding cells
- K+ is pumped into guard cells and water follows and guard cells become turgid
50
Stomatal Closing
- K+ leaves the guard cells and water follows
- guard cells become flaccid and cells close
51
What is cohesion tension theory
- cohesion refers to hydrogen bonding of water molecules
- tension is the negative pressure that xylem conducting elements can withstand
52
What is a source tissue?
A tissue or organ that reproduces more photo-assimilates than it uses
53
What is a sink tissue?
A tissue or organ that consumes more photo-assimilates than it produces
54
What is the mass flow hypothesis
- water will flow into high solute concentration long the water potential gradient
- water will flow out of low solute concentration, and sugar will move in from high solute to low
55
What is phloem loading?
Sugars exported from source cells to sieve elements
56
what is Phloem Unloading
sugars are removed from sieve elements at sink
57
Describe the nitrogen cycle
1. Fixation - Bacteria reduce N2 to nitrogenase/ammonia
2. Nitrification - bacteria oxidize ammonia into nitrite and nitrate
3. Assimilation - Plants and microorganisms utilize nitrates and ammonia to produce specific tissues
4. Denitrification - Nitrate is reduced to N2 under anaerobic conditions
58
A nitrogen fixing prokaryote is...
Nitrogenase
59
Photosynthetic, aerobic diazotrophic Cyanobacteria
Segregate their oxygenic, photosynthetic apparatus from nitrogen fixing apparatus in space.
60
Symbiotic, facultatively aerobic diazotrouphs (Rhizobiaceae)
Rely on the microaerophilic environment within plant root nodules and C/energy supplied by the plant (photosynthesis)
61
Rhizobium Symbiosis (rhizobia)
1. Relationship between N fixing bacteria and legume plant
2. Involves metabolic integration between specific bacterial and plant host species
3. Forms nodules on the roots/stems
62
How does the rhizobia symbiotic process occur
1. The plant produces flavinoids that attract rhizobia
2. Most rhizobia produce NOD factors that identify them as appropriate symbionts
3. The plant prepares to form a symbiotic nodule structure
4. Infection thread allows rhizobia tovesicles
5. Bacteria multiply and infect new plant cells
6. Creates vascular connections with the plant: photoassimilates (C in, fixed B out)
63
Give examples of host plants (striga species) and what they do
They steal nitrogen from other plants
- witchweed
- forbesil benth
- Aspera benth
64
How is nitrogen taken up and assimilated?
- NO3 transported to shoot by transportation stream, reduced in cytoplasm or stored in the vacuole
- Converted to NO2 in cytoplasm
- No2 -> NH4 in chloroplasts or root plastids
- NH4 used to synthesise glutamine, glutamate
65
Nitrate Reduction
- Nitrate is reduced to ammonium by a 2-step process catalyzed by
1. Nitrate Reductase
2. Nitrite Reductase
66
Nitrogen Transport
- NO3, NH4, amino acids are transported between tissues
- Principle amino acids: glutamine and asparagine carry 2N compared to other amino acids
67
Describe storage of N
- Storage forms = storage proteins inside organelles (protein storage bodies
- Dicots PSB and mostly in cotyledons
- Monocots = PSBs in endosperm of seed
68
Plant symbiotic associations with fungi =
mutualism both organisms benefit
69
What are mycorrhizae
- Fungi use extensive hyphae to scavenge nutrients
- Provide access to a much greater surface area/volume of soil than the root alone
- Rule
- Increase surface area for uptake of nutrients
70
The fungal wall is made up of...
chitin
71
What are the 2 types of mycorrhizal association
1. Ectomycorrhizae - colonizariton of plant roots often producing a diff morphology
2. Arbuscular (endo) mycorrhizae
- Only grow when being associated with another
- Esicular and arbicular mycorrhizae
- Plants supply lipids to their symbiotic fungi as a robust source of carbon for their metabolic needs
72
what are the 2 enzymes metabolizing sucrose in the sink tissues
invertase, sucrose synthase
73
name the strategies used by halophytes for salt storage
1. the sequestering of salts in the vacuole
2. Osmolytes accumulate in the cytoplasm to balance the osmotic potential of the vacuole.
3. Compatable solutes protect proteins and increase salt tolerence
