Question

Which pair of compounds are both products of photosynthesis?

oxygen and glucose
glucose and carbon dioxide
oxygen and carbon dioxide
water and glucose
3. Both photosynthesis and cellular respiration require all of the following EXCEPT:

chlorophyll
water
oxygen
glucose
4. In the absence of oxygen, a reactant for cellular respiration, the body can still produce ATP. Which of the following is a byproduct of anaerobic respiration?

water
citric acid
lactic acid
glucose

Answer 1

1 Oxygen and glucose.

In the light-dependent reactions, solar energy is absorbed in photosystem 2 which is a cluster of proteins and chlorophyll (the green pigment responsible for absorbing sunlight). This produces high-energy electrons that'll be passed down the electron transport chain. So, water molecules (the reactants in light-dependent reactions) are split to replace those high-energy electrons that are getting passed down back into the photosystem, and in the process generate 4 hydrogen ions and 2 oxygen. The oxygen formed is released into the atmosphere therefore being a product.

Cellular respiration involves the breakdown of a glucose molecule to produce 2 molecules of pyruvic acid in a stage called glycolysis (this also generates NADH+ and ATP although it needs 2 ATP) that's anaerobic (does not need oxygen). Cellular respiration can't happen unless there is a presence of oxygen in which glycolysis will then enter the next stage called citric acid cycle and finally the last stage called the electron transport chain. (To avid confusion let me specify that without oxygen anaerobic respiration takes place which involved glycolysis+fermentation and does NOT involve oxygen which is needed for cellular respiration. In the last stage--the electron transport chain--water is required to be formed when oxygen accepts the electrons (that were passed down the electron transport chain by NADH and FADH produced in glycolysis and the Krebs cycle or citric acid cycle) with hydrogen ions. If it wasn't for this step, the electrons wouldn't be able to be disposed of, and that would form a problem.
Water is needed as a reactant in light-dependent reactions in photosynthesis and oxygen needs to be produced and removed when the water molecules are split in light-dependent reactions or else it would cause a build up. In cellular respiration, oxygen is the electron acceptor in cellular respiration. Glucose needs to be broken down in cellular respiration and in photosynthesis it's needed to produce sugars in which energy is stored for the autotroph.

Where does that leave us? They both don't need chlorophyll. Why? Chlorophyll is the green pigment in thylakoids within the organelles called chloroplasts in which it's used to absorb sunlight in its photosystems that are embedded within their membranes. Since cellular respiration does not require sunlight for its processes, it does not need chlorophyll.

Answer 2

3. Glucose

Answer 3

4. Lactic acid

Answer 4

For 4, without oxygen, anaerobic respiration takes place. There are two types of fermentation that can take place: alcoholic fermentation and lactic acid fermentation. Remember, glycolysis happens within both fermentation and cellular respiration. So, pyruvic acid will be produced. However, since the electrons aren't going to be accepted by the electron acceptor oxygen in cellular respiration the electrons need to be passed back to pyruvic acid to be disposed of. The only thing is, in alcoholic fermentation, the products are ethyl, NAD, and carbon dioxide. In lactic acid fermentation, it's NAD and lactic acid. So, your answer would be lactic acid.

Answer 5

3 is not glucose. Glucose is needed for both cellular respiration (to be broken down) and for photosynthesis (to store energy).