Midterm 2 Study Guide Flashcards
What are the two phases in photosynthesis?
Light dependent reactions
Carbon-linked/light independent reactions
Which pigments participate in photosynthesis?
Chlorophylls and carotenoids
What are carotenoids’ role in photosynthesis?
They transfer light energy to special pigments called reaction center chlorophylls
Light-harvesting complexes
Structures with photosynthetic pigments that make up photosystems
Why are carotenoids useful in photosynthesis?
Because they broaden the usable range of wavelengths a plant can absorb for photosynthesis
Light-dependent reactions
Use light energy to drive the synthesis of ATP and NADPH in an endergonic (energy-requiring) process
Occur in thylakoids
Carbon-linked/light independent reactions
Use chemical energy (ATP, NADPH) to drive the endergonic incorporation of CO2 into carbohydrates
Occur in the stroma (the colorless fluid surrounding the thylakoids inside a chloroplast)
What is the final electron acceptor in photosynthesis?
NADP+, which is reduced to NADPH
What molecule donates an electron to the ETC (electron transport chain) in photosynthesis, and what is this process called?
Water (H2O) is oxidized, also known as photolysis of water
Why did Photosystem II evolve later than Photosystem I?
Because there was a need for an alternative source of electrons
How is ATP synthesized?
ATP synthase couples the movement of H+ protons down their electrochemical gradient (which was created by the ETC) to phosphorylate ADP into ATP
Basically, there is a high concentration of protons in the lumen. These protons want to move to an area of lower concentration, i.e., the stroma. The movement of H+ protons to an area of lower concentration is used by ATP synthase to generate mechanical energy, which it uses to synthesize ATP
What is the first stable product of the Calvin cycle (in photosynthesis)?
3-PGA (3-phosphoglycerate)
What are the 3 important chemicals in the Calvin cycle?
RuBP (ribulose-1,5-bisphosphate)
3-PGA (3-phosphoglycerate)
G3P (glyceraldehyde-3-phosphate)
How does the Calvin cycle work?
RuBP, CO2, and H2O are used to produce 3-PGA, which is then reduced to form G3P.
For every 3 RuBP molecules, one G3P molecule is produced. Multiple G3P molecules are then synthesized into sucrose.
The rest of the G3P molecules are recycled back into RuBP.
How does light intensity affect plant development?
Plants become acclimated to light intensity, producing sun/shade leaves
Shade leaves (as compared to sun leaves)
Thinner, higher leaf area, more thylakoids per chloroplast, and more photosystems
Photorespiration
When the Rubisco enzyme acts on oxygen instead of carbon dioxide, producing one 3PGA molecule instead of two
This is an inefficient use of energy
What is unique about CAM plants?
In CAM plants, CO2 fixation and the Calvin cycle are temporally separated
During the day, their stomata are closed
During night, their stomata open
Why is the CAM mechanism useful?
Plants lose water through open stomata, so in hot climates, plants with closed stomata during the day save water
How does the CAM mechanism work?
At night, CO2 is fixed by PEP carboxylase into malate
During the day, that malate releases CO2, which is then fixed by Rubisco
Difference between C4 and CAM plants
C4 plants have spatial separation, CAM plants have temporal separation
Which carboxylating enzymes do C3, C4, and CAM plants use?
C3 plants only use Rubisco whereas C4 and CAM plants use PEP carboxylase then Rubisco
Compare C3, C4, and CAM plants’ energy requirements
From least to most energy required: C3, C4 and CAM
Compare C3, C4, and CAM plants’ transpiration rates
From lowest to greatest transpiration rate: CAM, C4, C3
CAM plants are most water-efficient
What is aerobic respiration?
The release of chemical energy stored in carbohydrates; cellular respiration in the presence of oxygen
Where does glycolysis (part of respiration) occur and what does it produce?
It occurs in the cytosol and produces 4 ATP, 4 NADH, and 4 pyruvate molecules
What does the TCA/Krebs cycle (part of respiration) produce?
3CO2, 1 ATP, 4 NADH, 1 FADH2
What is the use of NADH and FADH2?
They are used to donate electrons to the ETC (electron transport chain)
What is the final electron acceptor in aerobic respiration?
O2, which is reduced to H2O
What is the most efficient way to determine the rate of respiration?
To measure the amount of CO2 produced
How does respiration occur in the absence of oxygen (anaerobic respiration)?
Instead of transporting pyruvate molecules to the mitochondria, glycolysis converts them into either lactic acid or ethanol.
This process is known as fermentation and produces very little ATP compared to aerobic respiration
What are the four groups of primary metabolites?
Amino acids
Fatty acids
Carbohydrates
Nucleobases
Where are fatty acids synthesized?
In plastids, or within chloroplasts in photosynthetic tissues
What kind of reaction is fatty acid synthesis?
An overall reduction reaction, which requires a significant amount of reducing power in the form of NADH
What are free fatty acids and what does the cell do to them?
They are very reactive molecules. The cell adds them to glycerol to reduce their reactivity (esterifying them)
Esterification reaction
When an acid and alcohol are joined by an ester bond
Triacylglycerols
Used as carbon storage by plants and can mostly be found in seeds
Diacylglycerols
Have a polar (hydrophilic) head & make up membranes (e.g., phospholipids).
Proteins
Long, unbranched chains of amino acids linked together by peptide bonds
How are peptide bonds formed?
Through dehydration reactions
Examples of PNPs
Allelopathic phytoxins, phytoalexins, repellants, toxins, attractants, hormones, and more
(you don’t have to memorize all of these, but you should know one when you see one)
Terpenoids
Derived from isoprene (5-carbon unit). Mostly multicyclic C structures with oxygen-containing functional groups
Examples of terpenes are carotenoids and menthol
Alkaloids
Nitrogen-containing molecules mostly synthesized from amino acids. Usually feeding deterrents and toxic to insects and other animals. Examples include Caffeine, Cocaine, Nicotine, Morphine
Phenolics
Molecules containing phenol groups
What are the 5 traditional plant hormones?
Auxin, abscisic acid, gibberellins, cytokinin, ethylene
What does abscisic acid do?
Cause stomatal closure
What does ethylene do?
Cause ripening in climacteric fruits, accelerate fruit abscission, promote female flower production in cucurbits
What is plasmolysis?
When the cytoplasm loses water and pulls away from the rigid cell wall
What is cation exchange capacity (CEC)?
A soil’s ability to retain and exchange cations
What is the central dogma?
Information flow is from
DNA–>RNA–>protein
What is a nucleotide made up of?
Phosphate group
Pentose sugar
Nitrogenous base
What are the coding and noncoding regions of genes called?
Exons, which are transcribed to mRNA, and introns, which are spliced out of the mature mRNA molecule
mRNA
Messenger RNA. Contains the codon (3 pase pair) information to build a protein
rRNA
Ribosomal RNA. Assembles with ribosomal proteins to form the ribosome, which is where mRNA is read and translated to protein form
tRNA
Transfer RNA. Carries amino acids to ribosomes to make proteins. Has an anticodon, which is the matching base pairs to the codon
An example of an anticodon for AUG is UAC because A matches with U, U matches with A, and G matches with C
What is the process of turning DNA to RNA called?
Transcription
What is the process of turning RNA to protein called?
Translation
Crossing over
In meiosis, when two homologous chromosomes cross over at a chiasma, exchanging genetic information
Linked genes
When two genes are on the same chromosome
How does does crossing over affect linked genes?
Theoretically, one would expect linked genes to be segregate together because they are located on the same chromosome. But they don’t always do this.
For example, crossing a plant with linked genes coding for white flowers and large leaves with a plant with linked genes for purple flowers and small leaves, one would expect their offspring to only possess the phenotypes of their parents. In practice, this is not the case due to CROSSING OVER. Some of the offspring with have purple flowers with large leaves and some will have white flowers with small leaves.
Why does crossing over happen in meiosis but not mitosis?
Because in meiosis, the chromosomes are positioned close together, whereas the homologous chromosomes in mitosis line up individually
Lignin
Cell wall strengthening
