Copy of 151_153_Disc14_HW_Fa23

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151-3 Introductory Biology - Discussion Homework 14 Week of Dec 11, 2023 Name: Reminder: Submit your homework on Canvas by the start of your scheduled discussion section! Please use a different font color so that your answers stand out. This week’s in-class activity will involve you playing a game that tests your knowledge of the most recent lecture content. Thus, we are asking you to review the lecture learning objectives (LLOs) and terms for last week’s lectures (12/3, 12/6, & 12/8) as your homework. In addition to helping you prepare for the discussion section this week, it will also help you prepare for the quiz and the final exam. As an added incentive, we will allow you to use your homework during discussion sections next week, but NOT your notes or any outside information . For each LLO we’d like you to do one of the following things: 1. Write out a response to each or a direct answer if you are able to do so. 2. If a particular LLO would require a long response, simply list bullet points to summarize. 3. Utilize the terms (listed below LLOs) in responding to each LLO wherever possible. 4. If you do not yet know the answer, that’s fine! Simply write out the questions you have or bullet point the components you know you need to study still. Writing out, “I don’t know” will not be enough to receive full credit. Mon (12/4): Respiration NOTE! IF you already completed this lecture’s LLOs for last week’s homework, please copy your answers here as well. 1. Understand anatomically, where multicellular organisms utilize diffusion over short distances and bulk flow over long distances. Gas exchange in more complex organisms alternates between bulk flow and diffusion. 1. The Ventilation by bulk flow: Breathing moves air (containing oxygen) into the lungs and air (containing carbon dioxide) out of the lungs. 2. Diffusion across the respiratory surface: Oxygen diffuses from the lung into the blood and carbon dioxide diffuses out of the blood into the lungs. 3. Circulation by bulk flow: Oxygen and carbon dioxide are transported by the circulatory system to and from Cells .

4. Diffusion between blood and cells: Oxygen diffuses from the blood into the cells and carbon dioxide diffuses out of the cells into the blood 2. Know that any organ in the body where gas exchange occurs will maximize surface area and work hard to maintain a gradient to facilitate diffusion. Your lungs and respiratory system automatically perform this vital process, called gas exchange. In addition, your respiratory system performs other roles important to breathing. 3. Describe how differences in partial pressure drive diffusion in/out of alveoli, capillaries, and tissues/cells. The change in partial pressure from the alveoli (high concentration) to the capillaries (low concentration) drives the oxygen into the tissue and the carbon dioxide into the blood (high concentration) from the tissues (low concentration), which is then returned to the lungs and exhaled 4. Know the structure of Hemoglobin and how it facilitates the loading/unloading of O2 via cooperative binding. The high concentration of oxygen that exists in our lungs pushes the reaction to the right, thus favoring loading and the formation of oxyhemoglobin. Conversely, the low concentration of oxygen in the tissue pushes the reaction to the left, thus favoring unloading of oxygen. 5. Understand how Oxygen disassociation curves help illustrate how oxygen is loaded or unloaded and shifts in different environments. - The curve is Sigmoidal due to cooperative binding on oxygen by hemoglobin. In the middle of the curve,

small increases (or decreases) in p O2 result in large increases (or decreases) in hemoglobin saturation. -A shift of the curve to the right indicates decreased affinity of the hemoglobin for oxygen and hence an increased tendency to give up oxygen to the tissues. A shift to the left indicates increased affinity and so an increased tendency for hemoglobin to take up and retain oxygen. Terms: Gas exchange, bulk flow vs diffusion, ventilation, circulation, blood (RBC), tidal ventilation, intercostal muscles and diaphragm, trachea, lungs, Bronchi, bronchiole, alveoli, pulmonary capillaries, Hemoglobin vs Myoglobin, Heme group (Fe), 0 2 dissociation curve, cooperative binding Wed (12/6): Circulation and the Heart 1. Explain how vessels of different sizes facilitate bulk flow and diffusion. Vessels of different sizes facilitate bulk flow and diffusion by providing different types of transport mechanisms. For example, large vessels such as arteries and veins provide bulk flow by using the pressure generated by the heart to move blood through the circulatory system. In contrast, smaller vessels such as arterioles and capillaries facilitate diffusion by allowing for the exchange of oxygen, nutrients, and waste products between the blood and surrounding tissues. 2. Understand how the differences in the structure of veins and arteries underlie their different functions. The differences in the structure of veins and arteries underlie their different functions. Arteries are thicker and more muscular than veins, allowing them to withstand the high pressure generated by the heart and maintain blood flow to different parts of the body. Veins, on the other hand, have thinner walls and less muscle, as they rely on the surrounding muscles to help move blood back to the heart against gravity. 3. Recognize how pressures facilitate things leaving and returning into capillary beds. Pressures facilitate things leaving and returning into capillary beds. In the capillary bed, the pressure inside the capillaries is higher than the pressure in the surrounding tissues, which facilitates the exchange of oxygen, nutrients, and waste products between the blood and tissues. This pressure difference also allows for fluid to move out of the capillaries and into the tissues, which is then returned to the bloodstream via the lymphatic system. 4. Explain the path of blood from the body, through the heart to the lungs, back to the heart, and out to the body again.

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Blood from the body enters the right atrium of the heart via the superior and inferior vena cava. It then passes through the tricuspid valve into the right ventricle, which pumps it through the pulmonary valve into the pulmonary artery and to the lungs. In the lungs, the blood is oxygenated and returns to the left atrium of the heart via the pulmonary veins. From there, it passes through the mitral valve into the left ventricle, which pumps it through the aortic valve into the aorta and out to the body again. 5. Examine the connectivity of the specialized cardiac muscle cells and how they generate action potentials to synchronously pump blood through the chambers. Specialized cardiac muscle cells are connected by gap junctions, which allow for the rapid spread of action potentials throughout the heart muscle. These cells generate action potentials spontaneously, allowing the heart to contract rhythmically and pump blood through the chambers in a coordinated manner. 6. Understand how the nervous and endocrine systems control heart rate as needed and how under different circumstances blood flow to different organs will change. The nervous and endocrine systems control heart rate as needed by altering the rate of depolarization of the specialized cardiac muscle cells. The sympathetic nervous system increases heart rate and contractility in response to stress or exercise, while the parasympathetic nervous system decreases heart rate during rest and relaxation. Blood flow to different organs changes under different circumstances, such as during exercise, when more blood is directed to the muscles, or during digestion, when more blood is directed to the digestive system. Terms: Artery & arteriole vs vein & venule, capillary, pressure vs resistance, blood pressure vs. osmotic pressure, lymph, vasoconstriction vs vasodilation, pulmonary vs systemic circulation, Every term on the heart diagram (I’m sorry there are so many…), systole vs diastole, SA node, AV node, modified muscle fibers, electrocardiogram (EKG) Fri (12/8): Ingestion, Digestion, & Absorption 1. Know the foregut, midgut, and hindgut’s roles in digestion. Gastrointestinal tract divides into the foregut, midgut, and hindgut. Foregut forms esophagus, stomach, pancreas and duodenum up to the ampulla of vater. Midgut forms the distal duodenum, jejunum, ileum, cecum, ascending colon, and proximal two-thirds of the transverse colon. Undigested food and waste products from digestion also pass through the hindgut, which

can recover a number of important substances, leaving a dehydrated fecal pellet for excretion. The hindgut may be differentiated into a pylorus, ileum, and rectum 2. Know where and how the three macromolecules break down (both chemically and mechanically) in the foregut and midgut and how they are absorbed into the body. Mechanical digestion involves physically breaking down food and substances into smaller particles to more efficiently undergo chemical digestion. Role of chemical digestion is to further degrade the molecular structure of the ingested compounds by digestive enzymes into a form that is absorbable into the bloodstream. 3. Understand the necessity of a strongly acidic stomach and how protein digestion occurs within the stomach. Because of the hydrochloric acid in the stomach, it has a very low pH of 1.5 - 3.5. Acidity of the stomach causes food proteins to denature, unfolding the three-dimensional structure to reveal just the polypeptide chain. This is the first step of the chemical digestion of proteins. HCl in the gastric juice has 4 main functions: 1) Activates pepsin for protein digestion Pepsinogen pepsin 2) Breaks down tough fibrous foods 3) Denatures proteins 4) Kills bacteria and other microorganisms 4. Describe how the stomach creates and maintains an acidic stomach. Acid secretion is initiated by food: thought, smell or taste of food effects vagal stimulation of gastrin-secreting G cells located in distal one third (antrum) of stomach. Arrival of protein to the stomach further stimulates gastrin output. 5. Describe how the small Intestine works with the pancreas and liver to finish digestion and start/complete absorption. Your small intestine makes digestive juice, which mixes with bile and pancreatic juice to complete the breakdown of proteins, carbohydrates, and fats. Bacteria in your small intestine make some of the enzymes you need to digest carbohydrates 6. Know that the large intestine retains digesta long enough to absorb water and nutrients before expulsion. This is a statement - no question asked. 7. Compare and contrast hindgut vs. foregut fermentation strategies. Know where fermentation happens for each and what strategies are employed to maximize energy and nutrient acquisition. Hindgut fermentation:

● Definition: Hindgut fermentation refers to the process of microbial fermentation that occurs in the hindgut (large intestine or cecum) of animals. ● Location: The fermentation process takes place in the hindgut, which is the posterior part of the digestive system. ● Strategies: Hindgut fermenters have a relatively simple stomach and rely on microbial fermentation in the hindgut to break down complex carbohydrates. They have a large cecum or colon where microbial fermentation occurs. This fermentation process allows them to extract energy and nutrients from plant material that would otherwise be indigestible. Hindgut fermenters often have a longer digestive tract to allow for more time for fermentation to occur. Foregut fermentation: ● Definition: Foregut fermentation refers to the process of microbial fermentation that occurs in the foregut (stomach or specialized chamber) of animals. ● Location: The fermentation process takes place in the foregut, which is the anterior part of the digestive system. ● Strategies: Foregut fermenters have a specialized chamber, such as a rumen or a complex stomach, where microbial fermentation occurs. This chamber allows for the breakdown of complex carbohydrates before they enter the small intestine. Foregut fermenters have a symbiotic relationship with microorganisms that help them digest plant material. The fermentation process in the foregut enables them to extract energy and nutrients from plant material more efficiently. Terms: Essential amino acids (don’t memorize them), vitamins and minerals (don’t memorize them), foregut vs midgut vs hindgut, mechanical vs chemical digestion, ingestion, digestion, absorption, & expulsion, mouth, saliva, amylase, esophagus, peristalsis, stomach, pepsin, pepsinogen, HCl, lipases, parietal cell, carbonic anhydrase, pyloric sphincter, small intestine, duodenum, pancreas, CCK, gall bladder, bile (or bile salts), secretin, HCO3-, pancreatic duct, ampullae of Vater, villi & microvilli, Na-glucose co-transporter, glucose transport protein, hepatic portal system, liver, large intestine (colon), rectum, appendix, cellulose, cellulase, hind vs foregut fermenters, Short Chain Fatty acids (SCFa’s), Rumen, Cecum, Cecotrope, Coprophagy

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