Biology 1 Exam 3Chapter 111. Distinguish between local and long-distance cell signaling - How do cells communicate with one another? How does your heart know when to speed up, your eyes to dilate, and for your muscles to contract? Our cells can be likened to people and they communicate in a specific way with each other. Cells can communicate by direct contact with each other and signaling substances can pass freely from one cell to the next. This local signaling is termed local regulators, and messenger molecules can travel short distances from one cell to the next. A common one that we all will learn as the major progress is in the nervous system. Long distance signaling is through the endocrine system and this deals with the hormones. These effects are slow and long lasting. Whereas the local signaling usually effects a small area of cells, the long distance signaling is usually systemic (full body) effects. 2. Describe the three stages of cell signaling. There are three stages to cell signaling: First, there is reception. This means the target cell “detects” that an outside signal is acting on it. This is like if someone knocks on your door, you are “receptive” to someone trying to communicate with you. Next comes transduction. The signal molecule that was trying to act on the target cell binds to a receptor on the target cell and this brings about a certain cellular response. So now the person that knocked on your door punches you in the nose and you feel intense pain. The signal “transduced” your body to feel pain. Cells aren’t that violent though. Finally, comes the response. In our example, your nose breaks. In a relevant example, insulin binds to a receptor on the cell and cause glucose to enter the cell. So the target cell first detects the outside signal of insulin, then insulin attached to a receptor on the cell, and the effect was tolet glucose into the cell. 3. Describe the three types of plasma membrane receptors.Cells can only take effect from outside molecule through receptors on their surface. A cell is not smart enough to know what a molecule is, until the molecule binds to a receptor on the cell. One type is the G-protein coupled receptor. First, the hormone will bind to the receptor. This binding will then initiate a chain inside the cell called the second messenger system. A moleculecalled a G-protein will be activated via a GTP, which is activated when the hormone binds. The G-protein will then in turn activate something called adenylate cyclase. This enzyme will then use an ATP molecule and convert it to cAMP, and this will go to activate a protein kinase. Everything in the body is really done through phosphyorlation and dephospyorlation, and the protein kinase is the enzyme that does that. So it is a pathway for certain molecules The next one is the receptor tyrosine kinase and this involves two receptors. The molecule (or ligand as it is called) binds to one receptor and this causes both of them to fuse together. Now the receptors, which have 6 tyrosines on them, donate 6 phosphates via ATP’s to an adjacent receptor, activating it. And then whatever the effect the ligand was supposed to have in the cellhappens. Ion channel receptors are the easiest one to understand. The channel is normally closed, like a closed door. A ligand attaches to the receptor on the channel, opening it, just like a key opens adoor. This allows certain molecules to enter as long as it is open. Sodium is an example of a molecule that enters a cell this way.4. Understand the specificity of interaction between a ligand and a receptor - The receptor is specific to the ligand. This is how the body recognizes other cells and molecules. 5. In general terms, explain the role of second messenger in signal transduction - This is that multi-step process that we covered with the G-protein, but why would our cell do this; it’s so many steps? One instance it is used is with hormones. The steroid hormones are a class of hormones that candiffuse across the plasma membrane (this is like the wall of the cell, or the fence of a house; it keeps bad things out). The peptide hormones, on the other hand can’t cross the plasma membrane. They are water soluble and can’t cross, so they have to do this long chain to get effect the cell. What he stresses is the epinephrine pathway. It’s the same thing The second messenger is Camp and this activates protein kinases, which cause the effect in the cell.6. What are the advantages to this multi-step process?- So the one hormone attached to the receptor, went through many steps to finally activate a protein kinase. The second messenger system is effective as there is a huge amplification effect. For example, it only takes one molecule of the hormone to start the cascade, but many G-proteins can be activated, which can activate many adenylate cycles, which activate many more cAMP etc. Chapter 12 1. Understand specific events associated with different stages of the cell cycle.Chapter 16 goes over everything about DNA replication, but how does that process start? How do cells multiply? That is all explained in the cell cycle. The cells life has different cycles and depending what cycle it is in, depends what it is doing. So we have to go from one cell to two identical cells. The chromosomes are the packages that contain the thousands and thousands of strands of DNA and we have to multiply these. A few things that you might need to know: Somatic cells contain 46 chromosomes and gamete cell contain only 23; somatic have 23 from the mom and23 from the dad, and the gamete cells just have 23. The gamete are the sex cells, so sperm or eggs. When a cell multiplies, it doubles the number of chromosomes and splits. So say there’s 46 chromosomes, it will double to 96 and split into two cells with 46 each. The process when itdouble is called mitosis and is touched on chapter 16. The stages to know our interphase, G1, S, G2 and mitosis. During interphase, G1, S, and G2, thecell is getting ready to divide. It doubles all of its organelles, chromosomes, and DNA (in the S phase only; gone over on chapter 16). 2. Know the different stages of mitosis.- Mitosis itself is divided into certain stages: prophase, prometaphase, metaphase, anaphase, and telophase. All of mitosis depends on the formation of the mitotic spindle; the structure that the chromosomes will separate into two cells on. This spindle is made from
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