Photosynthesis vs. Cellular Respiration

Photosynthesis is the process of making glucose that will end up being used by all organisms on earth, and cellular respiration is the process of converting glucose into ATP. The chemical reaction of photosynthesis is 6H2O+ 6CO2 --[light and chlorophyll]--> C6H12O6 + 6O2 and the chemical reaction of cellular respiration is the reverse of that, only, it does not need light or chlorophyll to happen.

The two processes are similar in that they have the same substances in the beginning and end. As well, both processes are needed to ensure that cells in an organism get the ATP they need. In both processes, ATP is produced. In the light dependent reaction of photosynthesis, ATP is made during the chemiosmosis of hydrogen ions through ATP synthase. In glycolysis, Krebs cycle, and the electron transport chain of cellular respiration, ATP is produced. 

In glycolysis, ATP is produced when BPG is converted into PGA (two molecules of ATP are produced, as glycolysis yields two BPGs). In the Krebs cycle, ATP is made when succinyl CoA becomes succinate (again, two ATPs are made). Finally, in the ECT, ATP is made when electrons pass through NADH dehydrogenase, coenzyme Q and cytochrome b-c1 complex, and cytochrome oxidase complex (COC).

Both cellular respiration and photosynthesis need the proton gradient across membranes to power ATP synthase, which in turn, makes ATP. As protons move through ATP synthase, it attaches another phosphate unto ADP to make 3 phosphates.

Finally, both these processes happen inside organelles with double membranes. Photosynthesis happens in chloroplasts (in plants and bacteria), and cellular respiration happens in mitochondria (all other organisms). 

Photosynthesis and cellular respiration have many differences as well as similarities, but in the end, they are both very important processes living things need to obtain energy.

The Light Dependent Reaction vs The Light Independent Reaction

PHOTOSYNTHESIS (LIGHT DEPENDENT)
Photosynthesis is a process that happens in plants and bacteria that allows them to make their own energy. This process also provides energy for every other organism on earth. More specifically, it happens in the chloroplasts of plants. Chloroplasts are special cells in plants that have 2 membranes, and are made up of stacks of thylakoids (granum). The thylakoid contains chlorophyll, which is a catalyst. It is in the thylakoid where light is used to produce ATP and NADPH (energy carrying molecules).

Photosystem II absorbs light with wavelengths of 680nm, in doing that, it splits a water molecule and takes its electrons in a process called hydrolysis(leaving 2 protons and an oxygen ion). The electrons make it down the electron transport chain, leaving redox reactions in its wake.

The electrons are passed to PQ (plastoquinone), PSII oxidizes and PQ reduces. Then, from PQ, the electrons travel to B6F, and a portal is created for hydrogen ions to flow out of the thylakoid membrane. Then they are passed to PC, but before they can be passed to Photosystem I, PSI must be struck by light of 700mn.

From PSI, the electrons are passed to FD and FNR. FNR then passes them to NADP+ to make NADPH. This entire process continues as long as there is an abundant amount of both water and sunlight.

(PSII > PQ > B6F > PC > PSI > FD > FNR > NADP+ > NADPH)

The hydrogen that were transferred through PQ and B6F cause an imbalance of pH on either side of the membrane. This causes the H+ ions to go back into the chloroplast stroma through the ATP synthase, in a process called chemiosmosis. This allows ADP to be converted into ATP (by adding a third phosphate). This entire process is known as the non-cyclic light dependent reaction and it happens in eukaryotic cells.

Prokaryotes use the cyclic light dependent reaction which only consists of B6F, PSI, FD, and FNR, and electrons are returned to B6F again, and again (creating the electron portal). In this process, however, NADPH is not made, and ATP is used directly, instead of making glucose.

CALVIN CYCLE (LIGHT INDEPENDENT)
The light independent does not use energy from the light, but rather the energy from ATP (which is made from the light dependent reaction).

The Calvin Cycle begins with carbon fixation, a process where carbon dioxide reacts with RuBP (ribulose biphosphate) and produces 2 strands of PGA, each with 3 carbons, since carbon chains with more than 6 carbons are unstable. This reaction is catalyzed with rubisco.

A phosphate from ATP is added to each PGA, changing it into BPG, and the two ADPs go back to the light dependent reaction to be reconverted into ATP. Then, a phosphate group is removed from BPG by NADPH, in that process, a hydrogen from NADPH is lost, and NADP+ also goes back to the thylakoid to be reconverted into NADPH. The compounds that are formed from the loss of phosphate are G3P. The two G3Ps formed can combine (with the help of a reshaping enzyme) to make one molecule of glucose.

The results from one cycle of the Calvin cycle are as follows: 3 RuBPs catalyzed > 6 PGAs made > 6 BPGs > 6 G3Ps

5 of the 6 G3Ps are recycled through a series of reactions and becomes RuBP to go through the cycle again, and 1 of them makes it out of the cycle. Therefore, it takes two Calvin cycles to make one molecule of glucose.

OVERALL REACTION
6CO2 + 6H2O -[light and chlorophyll]-> C6H12O6 + 6O2

Pig Dissection!

On the 27th and 28th of April, a pig dissection was done in SBI 4U1-03. Each lab group received a pig.

The "before" of the pig.

After cutting open the pig, we first isolated the liver. The liver produces bile (a substance that breaks down fats), stores glucose as glycogen, cleanse drugs of toxins, and stores iron.

The liver is the largest organ in the pig.

The next isolation was the stomach. It looked like a little sac, and inside contained dark particles that looked like pellets. This is likely to be a substance called meconium, which is made up of the things the infant ingested while in the uterus (eg. epithelial cells, bile, amniotic fluid). The stomach is the organ that holds the bolus (food) that an organism eats. In the stomach, the food is churned with acid to break it down.

Stomach

Contents of the stomach : meconium

 The pancreas is a lumpy, leafy-looking organ that produces insulin and glucagon. As well, it secretes digestive juices that help further break down food in the small intestines.

Pancreas

 Below are a pair of kidneys. Kidneys are bean-shaped organs that filters out toxins from blood, absorbs nutrients for blood, and make urine.

Kidneys

Another organ that comes in pairs. Our pig was female, therefore, it was necessary to isolate the ovaries. The ovaries are what contain the eggs of a female. These eggs have half the DNA of a regular cell and, with a sperm cell, can form a zygote.

Ovaries

The spleen is a long, thin, organ that filters blood, which helps the immune system recognize dangerous antibodies.

Spleen

After the kidneys make urine, it is stored inside the bladder. The bladder is a sac that leads to the urethra, where the urine is excreted.

Bladder (looks like it has feet!)

The heart is made of strong cardiac muscle that circulates blood throughout the body. This organ is what makes sure that all parts of the body can get what it needs (eg. oxygen, glucose) as well as can get rid of what it doesn't need (eg. carbon dioxide, waste)

Heart

Lungs bring in what every mammal needs to survive, oxygen. Not only that, it also gets rid of what could be toxic to our bodies if its concentration gets too high, carbon dioxide. This is also a body part that comes in pairs. Lungs are filled with tiny little sacs that increase surface area to get maximum oxygen.

Lungs

Eyes are sensory organs that allow us to see. Light rays enter the eye lens and the information is interpreted in the brain.

Eyeball

Eye lens (left), gallbladder (right)

The gallbladder is a small organ that holds the bile (produced by the liver) until it is needed.

Lastly, the arguably most important organ, the brain. The brain was hard to isolate, due to its delicateness, and therefore took the most time. The brain is the control centre for the entire body. It processes information, and relays an appropriate response to it. The brain controls all our conscious thoughts and all our unconscious thoughts.

Brain (there wasn't enough time for an isolation)

After two days of dissection, our pig looked like this:

Aftermass of dissection