a. 1. redox reactions means the transfer of electrons . In a redox reaction, the loss of electrons from one substance is called oxidation, and the addition of electrons to another substance is known as reduction.

In photosynthesis, the reaction is

Water is split, and electrons are transferred along with hydrogen ions from the water to carbon dioxide, reducing it to sugar.
Because the electrons increase in potential energy as they move from water(H-O bond) to sugar(C-H bond), this process requires energy—in other words is endergonic. This energy boost is provided by light.

In cellular respiration, the summary equation is 
Glucose loss electrons and become oxidized, oxygen get electrons and become reduced, so this reaction is redox reaction.
In cellular respiration, C-H bond are broken and release energy as the electrons from hydrogen form H-O bonds in water, so this reaction is endergonic.

according to the second law of thermodynamics------every energy transfer or transformation increases the entropy of the universe, which also can be understood that during every energy transfer or transformation, some energy becomes unavailable to do work, like heat.

we use this equation to show energy transfer or tranformation,ΔG means The change in free energy; ΔH symbolizes the change in the system’s total energy; ΔS is the change in the system’s entropy; and T is the absolute temperature in Kelvin (K) units. When ΔG is negative, mean the reaction can happen spontaneously, release energy; if posivitive, need energy input.

autotrophs capture Light energy by photosynthesis, energy transformed from light energy into chemical energy stored in organic molecules like sugar, some is lost as heat when chlorophyll’s electrons go back to its ground state from exited state. ΔG is positive, andΔS is negative, thus entropy is decreased.
In cellular respiration, chemical energy in sugar is partly transferred to chemical energy in ATP for cell work , and most are lost as heat to maintain the body temperature. So ΔG is negative, ΔS is positive, entropy is increased.