Question

1a. what generates proton gradient? where is it generates and how does that limit amount of gradient possible?

1b. What is oxygen used for during metabolism, and what happens if it is absent?

1c. What molecule increases in the cell when oxygen is absent, and what cellular process related to cell death can this trigger? How is this mechanism an anti-cancer mechanism?

1d. In multicellularity, what problem arises in reproduction by only a subset of the aggregate cells? Does this same problem arise in clonal forms of multicellular organisms?

1e. What enzymes are used in cell signaling in metazoa?

Answer 1

1.a. Proton gradient is generated when the electron transport chain transferes H+ ions in to the outer compartment of the mitochondria. Inside the mitochondrial matrix, NADH and FADH2 are  formed during Krebs cycle which consumes some H+ ions inside the mitochondrial matrix. Formation of water absorbing the electrons and protons with in the matrix. All this will reduce H+ ion concentration inside the matrix and increase H+ ion concentration in outer compartment. That is how a proton gradient is generated in mitochondria. The gradient is generated between the matrix and outer compartment of the mitochondria.

1.b. O2 is the final electron acceptor in the process of cellular respiration. Electrons given away by the reduced co-enzymes pass through the electron transport chain which are ultimately accepted by O2 to form H2O. If O2 is not there, there will not be acceptor molecule for electrons in mitochondria, resulting in ETC stoppage.

1.c. When O2 is absent, lactic acid accumulates with in the cell. Accumulation of lactic acid can trigger cell death. lactic acid is important energy source to cancer cells. By preventing the availability of lactic acid, it becomes a good anti-cancer mechanism.

1.d. If only a subset of aggregate cells are involved in reproduction, embryo can/t be completely formed. This is because all cells are not not totipotent in multicellular organism.

Clonal forms of multicellular organisms include cells that are physically connected.  Each cell can survive independently. In such organisms every cell is totipotent to form a whole organism. So even if some cells are separated they can form whole organism.