Question

1. In paracrine signaling, the signaling molecules affects only: Target cells close to the cell from which it was secreted a. b. Target cells distant from its site of synthesis in cells of an endocrine organ Both a. and b. с. d. None of these 2. Below are listed the events that occur in cell to cell communication. Signal transduction occurs 1. 2. Plasma membrane receptor binds with a ligand A cellular response is effected 3. 4. Ligand is released by signaling cell Which of the following lists these events in the correct order? с. 3,4, 2, 1 2,3, 4, 1 d. 4, 2, 1, 3 b. 4, 3, 2, 1 a. 3. Which organelle is primarily responsible for ATP production in eukaryotic cells? c. lysosomes d. ribosomes a. mitochondria b. chloroplasts 4. lon-linked gated channels are receptor proteins through which ions pass. A cell biologist has blocked these channels in a lab rat's liver tissue by using a chemical that: a. prohibits binding of a signal molecule b. prohibits ions from entering the cell via active transport c. causes ions to move in the opposite direction of the ion d. prohibits second messenger signaling. 5. Most cells are in physical contact with other cells by forming connections called: b. ion channel-linked receptors d. G-protein-linked receptors a. enzymatic receptors c. cell junctions e. cell surface markers 6. The class of cell surface receptors that acts indirectly on plasma membrane-bound enzymes or ion channels is called: a. second messenger receptors c. ion channel-linked receptors b. enzymatic rece ptors d. G-protein-linked receptors

Answer 1

1) paracrine signal molecules are released by cells and it affects the nearby cells only, paracrine signals cannot travel through the blood as the endocrine signals so the answer is a) target cells close to the cells from which it was secreted.

2) first the signal molecules are released by the cell and these signal molecules bind to the receptors in the target cell, causing the receptors to change the conformation so that it can activate the downstream signaling components, signal transduction occurs in the cell such that the transcription factors are activated or repressed to change the gene expression, so a response is induced in the cell so the answer is d) 4,2,1,3

3) in eukaryotic cells the mitochondria produce most of the ATP by oxidizing the reduced coenzymes like NADH and FADH2 via electron transport chain and using the energy of electrons in the reduced coenzymes, H+ from the cell is pumped to inter-membrane space, ATP synthase transports H+ down the concentration gradient and uses the energy released to make ATP so the answer is a) mitochondria ( chloroplast is found in plant cells only it is not found in all eukaryotic cells)