Module 19: Metabolism and Nutrition

Lesson 6: Energy and Heat Balance

Cân Bằng Năng Lượng Và Nhiệt

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Mỗi bài học (lesson) bao gồm 4 phần chính: Thuật ngữ, Luyện Đọc, Luyện Nghe, và Bàn Luận.
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Dưới đây là danh sách những thuật ngữ Y khoa của module Metabolism and Nutrition.
Khái quát được số lượng thuật ngữ sẽ xuất hiện trong bài đọc và nghe sẽ giúp bạn thoải mái tiêu thụ nội dung hơn. Sau khi hoàn thành nội dung đọc và nghe, bạn hãy quay lại đây và luyện tập (practice) để quen dần các thuật ngữ này. Đừng ép bản thân phải nhớ các thuật ngữ này vội vì bạn sẽ gặp và ôn lại danh sách này trong những bài học (lesson) khác của cùng một module.

Medical Terminology: Metabolism and Nutrition

absorptive state
also called the fed state; the metabolic state occurring during the first few hours after ingesting food in which the body is digesting food and absorbing the nutrients
acetyl coenzyme A (acetyl CoA)
starting molecule of the Krebs cycle
anabolic hormones
hormones that stimulate the synthesis of new, larger molecules
anabolic reactions
reactions that build smaller molecules into larger molecules
ATP synthase
protein pore complex that creates ATP
basal metabolic rate (BMR)
amount of energy expended by the body at rest
beta (β)-hydroxybutyrate
primary ketone body produced in the body
beta (β)-oxidation
fatty acid oxidation
bile salts
salts that are released from the liver in response to lipid ingestion and surround the insoluble triglycerides to aid in their conversion to monoglycerides and free fatty acids
biosynthesis reactions
reactions that create new molecules, also called anabolic reactions
body mass index (BMI)
relative amount of body weight compared to the overall height; a BMI ranging from 18–24.9 is considered normal weight, 25–29.9 is considered overweight, and greater than 30 is considered obese
calorie
amount of heat it takes to raise 1 kg (1000 g) of water by 1 °C
catabolic hormones
hormones that stimulate the breakdown of larger molecules
catabolic reactions
reactions that break down larger molecules into their constituent parts
cellular respiration
production of ATP from glucose oxidation via glycolysis, the Krebs cycle, and oxidative phosphorylation
cholecystokinin (CCK)
hormone that stimulates the release of pancreatic lipase and the contraction of the gallbladder to release bile salts
chylomicrons
vesicles containing cholesterol and triglycerides that transport lipids out of the intestinal cells and into the lymphatic and circulatory systems
chymotrypsin
pancreatic enzyme that digests protein
chymotrypsinogen
proenzyme that is activated by trypsin into chymotrypsin
citric acid cycle
also called the Krebs cycle or the tricarboxylic acid cycle; converts pyruvate into CO2 and high-energy FADH2, NADH, and ATP molecules
conduction
transfer of heat through physical contact
convection
transfer of heat between the skin and air or water
elastase
pancreatic enzyme that digests protein
electron transport chain (ETC)
ATP production pathway in which electrons are passed through a series of oxidation-reduction reactions that forms water and produces a proton gradient
energy-consuming phase
first phase of glycolysis, in which two molecules of ATP are necessary to start the reaction
energy-yielding phase
second phase of glycolysis, during which energy is produced
enterokinase
enzyme located in the wall of the small intestine that activates trypsin
evaporation
transfer of heat that occurs when water changes from a liquid to a gas
FADH2
high-energy molecule needed for glycolysis
fatty acid oxidation
breakdown of fatty acids into smaller chain fatty acids and acetyl CoA
flavin adenine dinucleotide (FAD)
coenzyme used to produce FADH2
glucokinase
cellular enzyme, found in the liver, which converts glucose into glucose-6-phosphate upon uptake into the cell
gluconeogenesis
process of glucose synthesis from pyruvate or other molecules
glucose-6-phosphate
phosphorylated glucose produced in the first step of glycolysis
glycogen
form that glucose assumes when it is stored
glycolysis
series of metabolic reactions that breaks down glucose into pyruvate and produces ATP
hexokinase
cellular enzyme, found in most tissues, that converts glucose into glucose-6-phosphate upon uptake into the cell
hydroxymethylglutaryl CoA (HMG CoA)
molecule created in the first step of the creation of ketone bodies from acetyl CoA
inactive proenzymes
forms in which proteases are stored and released to prevent the inappropriate digestion of the native proteins of the stomach, pancreas, and small intestine
insulin
hormone secreted by the pancreas that stimulates the uptake of glucose into the cells
ketone bodies
alternative source of energy when glucose is limited, created when too much acetyl CoA is created during fatty acid oxidation
Krebs cycle
also called the citric acid cycle or the tricarboxylic acid cycle, converts pyruvate into CO2 and high-energy FADH2, NADH, and ATP molecules
lipogenesis
synthesis of lipids that occurs in the liver or adipose tissues
lipolysis
breakdown of triglycerides into glycerol and fatty acids
metabolic rate
amount of energy consumed minus the amount of energy expended by the body
metabolism
sum of all catabolic and anabolic reactions that take place in the body
minerals
inorganic compounds required by the body to ensure proper function of the body
monoglyceride molecules
lipid consisting of a single fatty acid chain attached to a glycerol backbone
monosaccharide
smallest, monomeric sugar molecule
NADH
high-energy molecule needed for glycolysis
nicotinamide adenine dinucleotide (NAD)
coenzyme used to produce NADH
oxidation
loss of an electron
oxidation-reduction reaction
(also, redox reaction) pair of reactions in which an electron is passed from one molecule to another, oxidizing one and reducing the other
oxidative phosphorylation
process that converts high-energy NADH and FADH2 into ATP
pancreatic lipases
enzymes released from the pancreas that digest lipids in the diet
pepsin
enzyme that begins to break down proteins in the stomach
polysaccharides
complex carbohydrates made up of many monosaccharides
postabsorptive state
also called the fasting state; the metabolic state occurring after digestion when food is no longer the body’s source of energy and it must rely on stored glycogen
proteolysis
process of breaking proteins into smaller peptides
pyruvate
three-carbon end product of glycolysis and starting material that is converted into acetyl CoA that enters the Krebs cycle
radiation
transfer of heat via infrared waves
reduction
gaining of an electron
salivary amylase
digestive enzyme that is found in the saliva and begins the digestion of carbohydrates in the mouth
secretin
hormone released in the small intestine to aid in digestion
sodium bicarbonate
anion released into the small intestine to neutralize the pH of the food from the stomach
terminal electron acceptor
oxygen, the recipient of the free hydrogen at the end of the electron transport chain
thermoneutral
external temperature at which the body does not expend any energy for thermoregulation, about 84 °F
thermoregulation
process of regulating the temperature of the body
transamination
transfer of an amine group from one molecule to another as a way to turn nitrogen waste into ammonia so that it can enter the urea cycle
tricarboxylic acid cycle (TCA)
also called the Krebs cycle or the citric acid cycle; converts pyruvate into CO2 and high-energy FADH2, NADH, and ATP molecules
triglycerides
lipids, or fats, consisting of three fatty acid chains attached to a glycerol backbone
trypsin
pancreatic enzyme that activates chymotrypsin and digests protein
trypsinogen
proenzyme form of trypsin
urea cycle
process that converts potentially toxic nitrogen waste into urea that can be eliminated through the kidneys
vitamins
organic compounds required by the body to perform biochemical reactions like metabolism and bone, cell, and tissue growth
Nội dung này đang được cập nhật.
Dưới đây là các bài văn nằm ở bên trái. Ở bên phải là các bài luyện tập (practice) để đánh giá khả năng đọc hiểu của bạn. Sẽ khó khăn trong thời gian đầu nếu vốn từ vựng của bạn còn hạn chế, đặc biệt là từ vựng Y khoa. Hãy kiên nhẫn và đọc nhiều nhất có kể, lượng kiến thức tích tụ dần sẽ giúp bạn đọc thoải mái hơn.
The body tightly regulates the body temperature through a process called thermoregulation, in which the body can maintain its temperature within certain boundaries, even when the surrounding temperature is very different. The core temperature of the body remains steady at around 36.5–37.5 °C (or 97.7–99.5 °F). In the process of ATP production by cells throughout the body, approximately 60 percent of the energy produced is in the form of heat used to maintain body temperature. Thermoregulation is an example of negative feedback.

The hypothalamus in the brain is the master switch that works as a thermostat to regulate the body’s core temperature (Figure 1). If the temperature is too high, the hypothalamus can initiate several processes to lower it. These include increasing the circulation of the blood to the surface of the body to allow for the dissipation of heat through the skin and initiation of sweating to allow evaporation of water on the skin to cool its surface. Conversely, if the temperature falls below the set core temperature, the hypothalamus can initiate shivering to generate heat. The body uses more energy and generates more heat. In addition, thyroid hormone will stimulate more energy use and heat production by cells throughout the body. An environment is said to be thermoneutral when the body does not expend or release energy to maintain its core temperature. For a naked human, this is an ambient air temperature of around 84 °F. If the temperature is higher, for example, when wearing clothes, the body compensates with cooling mechanisms. The body loses heat through the mechanisms of heat exchange.
When the environment is not thermoneutral, the body uses four mechanisms of heat exchange to maintain homeostasis: conduction, convection, radiation, and evaporation. Each of these mechanisms relies on the property of heat to flow from a higher concentration to a lower concentration; therefore, each of the mechanisms of heat exchange varies in rate according to the temperature and conditions of the environment.

Conduction is the transfer of heat by two objects that are in direct contact with one another. It occurs when the skin comes in contact with a cold or warm object. For example, when holding a glass of ice water, the heat from your skin will warm the glass and in turn melt the ice. Alternatively, on a cold day, you might warm up by wrapping your cold hands around a hot mug of coffee. Only about 3 percent of the body’s heat is lost through conduction.

Convection is the transfer of heat to the air surrounding the skin. The warmed air rises away from the body and is replaced by cooler air that is subsequently heated. Convection can also occur in water. When the water temperature is lower than the body’s temperature, the body loses heat by warming the water closest to the skin, which moves away to be replaced by cooler water. The convection currents created by the temperature changes continue to draw heat away from the body more quickly than the body can replace it, resulting in hypothermia. About 15 percent of the body’s heat is lost through convection.

Radiation is the transfer of heat via infrared waves. This occurs between any two objects when their temperatures differ. A radiator can warm a room via radiant heat. On a sunny day, the radiation from the sun warms the skin. The same principle works from the body to the environment. About 60 percent of the heat lost by the body is lost through radiation.

Evaporation is the transfer of heat by the evaporation of water. Because it takes a great deal of energy for a water molecule to change from a liquid to a gas, evaporating water (in the form of sweat) takes with it a great deal of energy from the skin. However, the rate at which evaporation occurs depends on relative humidity—more sweat evaporates in lower humidity environments. Sweating is the primary means of cooling the body during exercise, whereas at rest, about 20 percent of the heat lost by the body occurs through evaporation.
The metabolic rate is the amount of energy consumed minus the amount of energy expended by the body. The basal metabolic rate (BMR) describes the amount of daily energy expended by humans at rest, in a neutrally temperate environment, while in the postabsorptive state. It measures how much energy the body needs for normal, basic, daily activity. About 70 percent of all daily energy expenditure comes from the basic functions of the organs in the body. Another 20 percent comes from physical activity, and the remaining 10 percent is necessary for body thermoregulation or temperature control. This rate will be higher if a person is more active or has more lean body mass. As you age, the BMR generally decreases as the percentage of muscle mass decreases.

OpenStax. (2022). Anatomy and Physiology 2e. Rice University. Retrieved June 15, 2023. ISBN-13: 978-1-711494-06-7 (Hardcover) ISBN-13: 978-1-711494-05-0 (Paperback) ISBN-13: 978-1-951693-42-8 (Digital). License: Attribution 4.0 International (CC BY 4.0). Access for free at openstax.org.

The hypothalamus controls thermoregulation.

Nội dung này đang được cập nhật.
Dưới đây là video và các luyện tập (practice) của bài này. Nghe là một kĩ năng khó, đặc biệt là khi chúng ta chưa quen nội dung và chưa có nhạy cảm ngôn ngữ. Nhưng cứ đi thật chậm và đừng bỏ cuộc.
Xem video và cảm nhận nội dung bài. Bạn có thể thả trôi, cảm nhận dòng chảy ngôn ngữ và không nhất thiết phải hiểu toàn bộ bài. Bên dưới là script để bạn khái quát nội dụng và tra từ mới.
Script:
  1. Some of the energy from the food that is ingested is used to maintain the core temperature of the body.
  2. Most of the energy derived from the food is released as heat.
  3. The core temperature is kept around 36.5 to 37.5 celsius.
  4. This is tightly regulated by the hypothalamus in the brain.
  5. The hypothalamus senses changes in the core temperature and operates like a thermostat to increase sweating or shivering, or inducing other mechanisms to return the temperature to its normal range.
  6. The body can also gain or lose heat through mechanisms of heat exchange.
  7. Conduction transfers heat from one object to another through physical contact.
  8. Convection transfers heat to air or water.
  9. Radiation transfers heat via infrared radiation.
  10. Evaporation transfers heat as water changes state from a liquid to a gas.
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