Answer:
A. donation of excited electrons by chlorophyll a to a primary electron acceptor
Explanation:
Photosystems are structures located at the thylakoid membrane that act to harvest energy light in order to convert it into chemical energy. Each photosystem is composed of a light-harvesting complex and a core complex, which in turn is composed of a reaction center. The photosynthetic reaction centers are multi-protein complexes that use light energy to catalyze the electron transfer across the chloroplast thylakoid membrane against a thermodynamic gradient. Moreover, antenna pigments are pigments that capture the energy from photons in order to transfer energy to other pigments in the photosystem (e.g., chlorophyll B and carotenes are antenna pigments, whereas chlorophyll A is the core pigment). Light energy absorbed by antenna pigments in the photosystems is transferred to the reaction center chlorophyll A molecules, thereby exiting electrons in the reaction center. A reaction center consists of two chlorophyll A molecules, which donate electrons to the primary electron acceptor.
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Below are the choices:
homogenous mixture
<span>heterogeneous mixture </span>
<span>semi mixture
</span>
You want to decorate the bottom of an aquarium with brightly colored rocks of different shapes and sizes. this describes a homogenous mixture<span>
</span>
<span>The word hetero means different. Since the rocks are varied i assume it would be a heterogeneous mixture.</span>
Answer:
It decreases the levels of cAMP in the cell, repressing transcription from the lac operon.
Explanation:
When glucose is absent, cAMP serves as coactivator binds to CRP, the catabolite gene activator protein. The CRP-cAMP complex binds to the site near the lac promoter and stimulates the expression of the operon by RNA polymerase many folds.
Catabolite repression refers to inhibition of the synthesis of enzymes of lactose catabolism when glucose is present as an energy source. In the presence of glucose, synthesis of cAMP is inhibited resulting in its lower cellular concentration. The lower cAMP levels do not allow the binding of cAMP and CRP. The result is reduced expressed of lac operon.
Answer: option B) Sympatric speciation is best described as a random event that disrupts the allele frequencies in a population
Explanation:
Sympatric speciation is an event/situation whereby organisms of the same species:
- live in the same territory or nearby territories ( i.e do not live in geographical isolation)
- DO NOT interbreed, but select a sexual mate from a much diverse territory to yield new species or offsprings.
This sexual selection then results in generations of offsprings that are genetically different from the rest of the same species due to uneven gene flow or disruption of alleles among the population of same species.
Thus, only option B is true.
