Lab 2 Homeostasis and Biomolecules

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Dec 6, 2023

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Name: Shaquea McCutchen Date: 8/21/23 Lab 2 : Homeostasis & Biomolecules Part I: Homeostasis/Feedback mechanisms The heating system of a house works to keep the temperature constant. If the house gets too cold, then the heat automatically turns on to warm the house. The heat stops when the preset temperature is reached. This is an example of a feedback mechanism . Organisms use many feedback mechanisms to either maintain or amplify important chemical systems. This could happen at a molecular level to coor-dinate the function of a single enzyme or it could happen throughout the body to regulate the organism’s internal temperature. Model 1: Positive and Negative Feedback 1. What two types of feedback mechanisms are illustrated in Model 1? negative and positive feedback 2. Define the words below as they are used in everyday language. a. Stimulus- thing that rouses activity or energy in someone or something b. Signal- conveys information and instruction c. Response- a reaction to something 3. Identify at least three similarities in the two types of feedback mechanisms in Model 1. They both work through stimulus, signal response, both are cyclical, and both are feedback mechanisms 4. Imagine that you have just gotten a puppy. In the course of playing with the puppy you throw a ball and the puppy chases after it. You then say “Good job!” and rub the puppy’s head to show him he did what you wanted him to do. a. Is the puppy likely to chase the ball the next time you throw it? Justify your reasoning- Yes, the puppy is likely to chase the ball the next time you throw it because he enjoyed being praised and having his head rubbed. b. Identify the portions of the scenario as stimulus or response. i. Puppy chases the ball. STIMULUS ii. “Good Job” and head rub. RESPONSE c. Is this scenario an example of positive or negative feedback? Justify your reasoning using the words “stimulus” and “response.” BIO 163 Page 1 Homeostasis and Biomolecules

Name: Shaquea McCutchen Date: 8/21/23 This is an example of positive feedback because the stimulus is reinforced to continue in the same direction until an event occurs. The result is to increase the activity. As long as the puppy continues to get the same response, more than likely he will continue doing what he's doing. 5. Later that day your puppy urinates on the couch. You then say “No, bad dog!” and place the puppy outside. a. Is the puppy likely to urinate on the couch again? Justify your reasoning- The puppy would not be likely to urinate on the couch again because he didn't enjoy being placed outside. b. Identify the portions of the scenario as stimulus or response. i. Puppy urinates on the couch. STIMULUS ii. “No, bad dog!” RESPONSE c. Is this scenario an example of positive or negative feedback? Justify your reasoning using the words “stimulus” and “response.” This would be negative feedback because response decreased or stopped the stimulus. 6. Which of the feedback mechanisms in Model 1 would be most useful for amplifying a condition that is advantageous for the organism? Positive feedback because the response increases the stimulus. 7. Which of the feedback mechanisms in Model 1 would be most useful for stopping a condition that is detrimental or limiting a condition to specified levels? Negative feedback because the response decreases the stimulus. Model 2- Thermoregulation in Humans 8. Examine Model 2. Based on what you see in the model, propose a definition for “thermoregulation.” How the body regulates to its internal temperature 9. According to Model 2, what portion of the brain contains sensors that monitor body temperature? Hypothalmus 10. According to Model 2: a. What are two mechanisms the body uses to cool itself? Increase sweat production and dilates blood vessels to the skin so that blood moves towards the skin and loses heat to outside the body b. What are two mechanisms the body uses to heat itself? The body shivers (which generates heat BIO 163 Page 2 Homeostasis and Biomolecules

Name: Shaquea McCutchen Date: 8/21/23 through muscle contraction) and it also diverts blood away from the skin and holds it deeper in the body so that less heat is radiated from the surface of the body 11. Consider the feedback loop that cools the body when it is too warm. a. Identify the “stimulus” and “response” in the feedback loop. stimulus (rising temperature) and response (sweating, blood diversion to the skin) b. Is this feedback loop positive or negative feedback? Justify your reasoning.- Negative Feedback loop; the rising temperature is stopped by the response 12. Consider the feedback loop that heats the body when it is too cold. a. Identify the “stimulus” and “response” in the feedback loop. stimulus (decreasing temperature) and response (shivering and blood diversion from the skin) b. Is this feedback loop positive or negative feedback? Justify your reasoning.- Negative feedback loop, the cold temperature is stopped by the response Many of the systems in the body are delicate. They function only under a specific range of parameters. Enzymes will denature if they get too hot or cold or if the pH of the solution they are in is too high or too low. Cells will not be able to process glucose for energy if the concentrations of oxygen in the blood are not high enough. Feedback mechanisms are used to keep the body in homeostasis. That is, many systems are in place that monitor and regulate important parameters of the body and keep them within normal levels. 13. Consider the state of homeostasis—maintaining conditions within certain limits. The body needs multiple mechanisms to keep all types of systems in check. a. Would a positive feedback loop ever be helpful in maintaining homeostasis? Justify your reasoning. Because positive feedback loops do not negate the stimulus (*they amplify it) they would not be able to keep internal conditions in the body the same over time. If positive feedback regulated the body temperature, an increase in body temperature would lead to further increase in body temperature. A decrease in body temperature would lead to further decreases in body temperature would lead to further decreases in body temperature until you died of hypothermia. Positive feedback* (because it amplifies the stimulus rather than negating it) does not help you maintain a stable environment in your body. b. Would a single negative feedback loop ever be helpful in maintaining homeostasis? Justify your BIO 163 Page 3 Homeostasis and Biomolecules

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Name: Shaquea McCutchen Date: 8/21/23 reasoning. Negative feedback loops are used to maintain homeostasis and achieve the set point within a system. Negative feedback loops are characterized by their ability to either increase or decrease a stimulus Model 3- Childbirth and Contractions 14. According to Model 3, what is the stimulus and what is the response during childbirth? The *stimulus is the baby's head against the cervix, which stretches the cervix. The response* is release of oxytocin (leading to uterine contractions) 15. What hormone, released from the hypothalamus, increases the intensity of contractions? Oxytocin 16. When the intensity of contractions increases, will the stimulus increase or decrease? As the intensity of contractions increases, the push of the baby's head against the cervix (stimulus) *increases.* 17. Is childbirth an example of a positive or negative feedback system? Justify your answer. childbirth is a *positive feedback* loop because the response amplifies or encourages the stimulus. 18. What will eventually stop the stimulus and thus stop the childbirth feedback loop? The *response will continue to increase* the stimulus (and vice versa) until the baby is pushed so hard against the cervix that it exits the body. At that point, there is no more response (release of oxytocin and ensuing contractions). 19. Below are several descriptions of processes that occur in the human body. For each one identify the stimulus and the response and state whether the process is positive or negative feedback. a. When human tissue, such as skin or a blood vessel, is torn or cut, the cells near the damage send out a signal that activates platelets in the vicinity. As the platelets begin to form a plug, they release more chemical signals to attract more platelets and other clotting factors until the bleeding is stopped. *Stimulus chemical signal; response platelets adhere to form a plug; Positive feedback* b. When a person has not taken in sufficient water they become dehydrated. This may cause a loss of blood pressure, which will trigger the release of antidiuretic hormone (ADH) from the hypothalamus and pituitary glands. This hormone signals the kidney to allow reabsorption of water by the blood vessels to bring the blood pressure back to normal conditions. BIO 163 Page 4 Homeostasis and Biomolecules

Name: Shaquea McCutchen Date: 8/21/23 *Stimulus decrease pH; Response releases of ADH and decrease in urine production; Negative feedback* c. When a human increases physical activity, the amount of fuel burned in its cells also increases, which in turn increases the concentration of dissolved CO2 in the blood. The CO2 reacts with water in the blood to make a weak acid, which lowers the pH of the blood. Sensory cells in the medulla of the brain register this drop in pH and send signals to the diaphragm and heart to increase respiration. This will clear the CO2 from the bloodstream. *Stimulus decrease in pH; Response increased respiration/heart rate; Negative Feedback* 20. Draw a diagram similar to Models 2 and 3 for one of the feedback mechanisms in Question 19 and insert the picture here. It must be hand drawned. BIO 163 Page 5 Homeostasis and Biomolecules

Name: Shaquea McCutchen Date: 8/21/23 BIO 163 Page 6 Homeostasis and Biomolecules

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Name: Shaquea McCutchen Date: 8/21/23 Part II: Biomolecules Graphic Organizer- Complete the following graphic organizer on biomolecules. Macromolecule What organisms/foods are they found in? Structure: What are they made of? Functions and Examples: How are they used? Carbohydrates found in all organisms Elements carbon, hydrogen, oxygen provide much of energy that cells require supply materials to build certain cell structures stored as reserved energy supply Monomers/ Subunits simple: monosaccaride (one sugar- fructose,glucose, galactose) and disaccaride (two sugars-maltose, sucrose, lactose) complex: polysaccharide (multiple sugar units-starch, glycogen, fiber) Bond glycosidic Location of Synthesis begins in the endoplasmic reticulum, but it is in the Golgi apparatus Lipids oils and fats Elements carbon, hydrogen, oxygen saturated unsaturated phospolipids Monomers/ Subunits triglycerides, phospholipids, and steroids Bond polar and non polar covalent bonds BIO 163 Page 7 Homeostasis and Biomolecules

Name: Shaquea McCutchen Date: 8/21/23 Location of Synthesis The endoplasmic reticulum Macromolecule What organisms/foods are they found in? Structure: What are they made of? Functions and Examples: How are they used? Proteins amino acids Elements carbon, hydrogen, oxygen structural materials, energy sources, and hormones combine with carbs and function as receptors antibodies-detect and destroy foreign substances enzymes-catalyze specific chemical reactions Monomers/ Subunits glycoproteins Bond peptide Location of Synthesis cytoplasm on ribonucleoprotein particles, the ribosomes Nucleic Acids All organisms contain these Not technically a “nutrient” Elements C, H, O, N , P Main types: DNA - stores genetic information RNA - copies of genetic information Also an example: Monomers/ Subunits Nucleotides (phosphate group + Deoxyribose sugar + Nitrogen base) Bond Phosphodiester bond BIO 163 Page 8 Homeostasis and Biomolecules

Name: Shaquea McCutchen Date: 8/21/23 ATP - energy currency molecule Location of Synthesis Nucleus (in eukaryotic cells) Lab Submission Please submit this document to the submission link on Blackboard. ☺ BIO 163 Page 9 Homeostasis and Biomolecules

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