Nutrients, Energetics, and Metabolism

Nutrients and Energetics

• Nutrients are essential elements and molecules the body needs
• Metabolic activity involves breaking down organic molecules to obtain energy, stored as ATP
• Energetics describes how the body balances heat gains and losses
• Cells require oxygen and nutrients, including water, vitamins, minerals, and organic substrates, to function

Metabolism

• Metabolism sums all chemical and physical changes in body tissues
• Catabolism breaks down large molecules into smaller ones, releasing energy to synthesize ATP
• Anabolism converts small molecules into larger ones, requiring energy to form new chemical bonds
• Anabolism functions include structural maintenance, growth support, secretion production, and nutrient reserve storage

Nutrient Reserves

• Triglycerides, most abundant storage lipids, consist primarily of fatty acids
• Glycogen, most abundant storage carbohydrate, is a branched chain of glucose molecules
• Proteins are the most abundant organic components in the body and perform vital cellular functions
• Energetics studies energy flow and its change from one form to another

Oxidation and Reduction Reactions

• Oxidation involves the loss of hydrogen or electrons; the electron donor is oxidized
• Reduction involves the gain of hydrogen or electrons; the electron recipient is reduced
• Electrons carry chemical energy
• In a redox reaction, the reduced atom or molecule gains energy, while the oxidized one loses energy
• Some energy is released as heat, and the remaining energy can perform physical or chemical work, like forming ATP

Electron Transport Chain

• The electron transport chain involves a series of protein complexes in mitochondria
• Electrons pass through a series of oxidation-reduction reactions and are ultimately transferred to oxygen, forming water
• Coenzymes, like NAD and FAD, play a key role in the flow of energy within a cell and act as intermediaries
• Coenzymes accept electrons from one molecule and transfer them to another

Coenzymes

• NAD and FAD remove hydrogen atoms from organic molecules, where each hydrogen atom contains an electron and a proton
• Accepting a hydrogen atom reduces the coenzyme
• Coenzyme FAD accepts two hydrogen atoms, gaining two electrons and forming FADH2
• Coenzyme NAD+ (oxidized form with a positive charge) accepts two hydrogen atoms, gains two electrons, releases one proton, and forms NADH

Carbohydrate Metabolism

• Carbohydrate catabolism generates ATP and other high-energy compounds through cellular respiration
• Cellular respiration involves glucose + oxygen becoming carbon dioxide + water
• Glycolysis, citric acid cycle, and the electron transport chain are all essential to carbohydrate metabolism
• One molecule of glucose yields a net gain of 30-32 ATP molecules

Glycolysis Specifics

• Glycolysis involves breaking glucose in the cytosol into smaller molecules.
• Glycolysis does not require oxygen
• Glycolysis breaks 6-carbon glucose into two 3-carbon molecules of pyruvic acid, also known as pyruvate
• Glycolysis begins when an enzyme phosphorylates a glucose molecule creating glucose-6-phosphate

Glycolysis requirements

• Glycolysis requires glucose molecules, appropriate cytosolic enzymes, ATP, ADP, inorganic phosphate groups, and NAD+ (a coenzyme)
• Aerobic metabolism happens within mitochondria, requiring oxygen
• Released energy from pyruvate breakdown produces a large amount of ATP
• The citric acid cycle and electron transport chain are both parts of aerobic metabolism

Mitochondrial specifics

• The outer mitochondrial membrane contains large pores and is permeable to ions and small organic molecules like pyruvate
• An inner membrane has a carrier protein that moves pyruvate into the mitochondrial matrix
• An intermembrane space separates the outer and inner membranes

Citric Acid Cycle

• During the citric acid cycle, hydrogen (H) atoms of pyruvate are removed by coenzymes, serving as the primary source of energy gain
• Carbon (C) and oxygen (O) atoms are removed and released in decarboxylation, producing CO2
• Pyruvate utilizes NAD and coenzyme A (CoA): 1 CO2, 1 NADH, and 1 acetyl-CoA are produced
• An acetyl group transfers from acetyl-CoA to a 4-carbon oxaloacetate molecule, creating 6-carbon citric acid

Outcomes of the Citric Acid Cycle

• CoA is released, enabling binding to another acetyl group
• One citric acid cycle removes two carbon atoms as it regenerates a 4-carbon chain
• Multiple steps require more than one reaction or enzyme that tie up H2O molecules in two steps
• Through substrate-level phosphorylation, one citric acid cycle produces one molecule of GTP (guanosine triphosphate)

Citric Acid Cycle Summary

• CH3CO-CoA + 3NAD + FAD + GDP + P[i] + 2H2O yields CoA + 2CO2 + 3NADH + FADH2 + 2H+ + GTP
• Oxidative phosphorylation produces ATP
• Through the transfer of electrons from NADH and FADH2 to oxygen, oxidative phosphorylation occurs
• A sequence of electron carriers within mitochondria are required for oxidative phosphorylation
• Over 90% of the body's ATP is generated by oxidative phosphorylation

Electron Transport Chain

• ETC protein complexes are located in the inner mitochondrial membrane, where key oxidative phosphorylation reactions occur
• The four respiratory protein complexes, coenzyme Q, and electron carriers (cytochrome molecules) are required
• Each cytochrome contains a pigment (containing metal ion) and a protein (surrounding pigment)
• Oxygen and electrons are needed for oxidative phosphorylation
• Oxygen availability limits ATP generation rate

ATP and Aerobic Metabolism

• Cells get oxygen from extracellular fluid diffusion
• Most cells primarily use the reaction pathway to create ATP.
• The ATP generating pathway begins with glucose and ends with carbon dioxide and water.
• One glucose molecule breaks down anaerobically into 2 pyruvate molecules during glycolysis, where the cell gains a net 2 ATP molecules

Glycolysis and ETC

• Two molecules of NADH pass electrons to FAD with an intermediate electron carrier in the intermembrane space, then to ETC
• Two revolutions of the citric acid cycle are required to break down 2 pyruvate molecules, where each turn yields 1 ATP via GTP
• Transferring H atoms to NADH and FADH2 results in an additional gain of 2 ATP molecules
• Coenzymes provide electrons to ETC

Summary of ATP production

• Total of 10 NADH and 2 FADH2 deliver electrons to ETC for each glucose molecule.
• Each NADH yields 2.5 ATP, where the 8 NADH from the citric acid cycle yields 2.5 ATP and 1 water molecule
• Each FADH2 yields 1.5 ATP; therefore, 2 FADH2 from glycolysis yield 3 ATP and 2 water molecules, resulting in the ETC creating 23 ATP
• 2 ATP are from glycolysis, 3-5 are from NADH generated in glycolysis, 2 are from the citric acid cycle (by means of GTP), 23 are from the ETC
• Produced ATP are produced in the mitochondria except 2 ATP
• Gluconeogenesis synthesizes glucose from noncarbohydrate molecules, specifically 3-carbon molecules that are not pyruvate

Glucose Management and Usage

• Glucose is stored as glycogen in the liver and skeletal muscle
• excess glucose creates excess glycogen through glycogenesis
• Glycogenesis requires several steps and the high-energy compound uridine triphosphate (UTP)
• Glycogenolysis involves the breakdown of glycogen to glucose monomers, occurring quickly via a single enzymatic step

Lipid Metabolism Breakdown

• Lipids consists of carbon, hydrogen, and oxygen in different proportions than carbohydrates
• Triglycerides are the most abundant lipid in the body
• Lipid catabolism (lipolysis) breaks lipids into pieces that are either converted to pyruvate or channeled directly into the citric acid cycle
• Hydrolysis splits triglyceride, producing 1 glycerol molecule and 3 fatty acid molecules

Glycerol and Lipids Conversion to Energy

• Liver converts glycerol to pyruvate in the cytosol
• Pyruvate is converted to acetyl-CoA to begin the Citric Acid Cycle
• Cells gain 120 ATP from the breakdown of one 18-carbon fatty acid molecule
• Lipid breakdown yields 1.3 times the energy compared to glucose from three 6-carbon glucose molecules

Lipid Synthesis

• Lipid synthesis (lipogenesis) uses almost any organic substrate
• Since lipids, amino acids, and carbohydrates can be converted to acetyl-CoA
• Glycerol is synthesized from dihydroxyacetone phosphate, which is an intermediate product of glycolysis and gluconeogenesis
• Nonessential fatty acids and steroids can be synthesized from acetyl-CoA

Essential Lipids

• Essential fatty acids cannot be synthesized in the body and must be consumed
• An example is the 18-carbon unsaturated fatty acids in plants, linoleic and linolenic acid
• Lipid storage gives the body important energy reserves and large amounts of ATP slowly, but water-soluble enzymes struggle to reach them

Lipids and the Body

• Lipid transport and distribution are important because cells need lipids to maintain plasma membranes, and steroid hormones must reach target cells in different tissues
• Because they are not generally soluble in water, the body uses special transport mechanisms for lipids to move from one region to another
• Most lipids circulate through the bloodstream as lipoproteins

Fatty Acids

• Free fatty acids make up a small portion of the bodies total circulating lipids
• Free fatty acids can diffuse easily across plasma membranes
• In blood, free fatty acids are generally bound to albumin, the most abundant plasma protein
• The main sources of free fatty acids are from triglycerides that diffuse from the intestinal epithelium, or those that have diffused out of lipid reserves when triglycerides are broken down

Free Fatty Acids as a Fuel Source

• Free fatty acids become an important energy source when glucose is scarce
• Cells metabolize free fatty acids in the liver, cardiac muscle, and skeletal muscle
• Lipoproteins are lipid-protein complexes that contain large insoluble glycerides and cholesterol
• Chylomicrons, Very low-density lipoproteins (VLDLs), Low-density lipoproteins (LDLs)—“bad cholesterol”, and High-density lipoproteins (HDLs)—“good cholesterol” are all lipoproteins

Chylmoicrons

• Chylomicrons are the largest lipoproteins
• Intestinal epithelial cells produces chylomicrons from dietary fats
• Chylomicrons transport absorbed lipids into lymph and then into the bloodstream

Protein Metabolism

• Protein metabolism synthesizes 100,000 to 140,000 different proteins, each with different structures and functions, but all are built from the same 20 amino acids
• Proteins function as enzymes, hormones, structural elements, and neurotransmitters
• Very little protein is used as an energy source
• Amino acid catabolism only occurs to use proteins for energy
• First, they must be converted into substances to enter the citric acid cycle

Protein Conversion specifics

• To convert proteins, they undergo transamination, deamination, and the urea cycle
• Removal of an amino group requires a coenzyme derivative of vitamin B6
• Transamination attaches the amino acid's amino group it to a keto acid
• Conversion of keto acid into an amino acid then: leaves the mitochondrion and enters cytosol and is available for protein synthesis

Deamination and Ammonia

• Deamination prepares amino acids for breakdown in the citric acid cycle
• The process removes an amino group and hydrogen atom, generating a toxic ammonium ion
• Specifically, generating ammonium ions primarily in liver cells
• Liver cells then use enzymes to remove toxic ammonium ions by synthesizing urea, through the urea cycle

Amino Acids and Usage

• Urea is a fairly harmless water-soluble compound excreted in urine
• When glucose and lipid reserves are inadequate, liver cells break down internal proteins and absorb additional amino acids from the blood
• Amino acids are deaminated; therefore, carbon chains are then sent to mitochondria
• Not all amino acids enter cycle at the same point, because ATP benefits vary
• Three factors make protein catabolism impractical, being that proteins are more difficult to break apart than complex carbohydrates or lipids, its by-product (ammonium ions) is toxic to cells, and proteins form most structural/functional components

Absorptive States (Proteins)

• In protein synthesis, the body sythesizes needed amino acids to buidl proteins
• Because of this, there are ten essential amino acids that must be consumed
• Eight essential amino acids are not synthesized at all, and two are insufficiently synthesized
• Nonessential amino acids are made by the body on demand
• Amination, or the addition of an amino acid group, is required

Absorptive and Postabsorptive States

• Nutrient needs of each tissue vary with types of enzymes
• Five metabolic tissues to consider are the liver, adipose tissue, skeletal muscle, nervous tissue, and other peripheral tissues
• The liver is the focal point of metabolic regulation and control
• Hepatocytes possess a great diversity of enzymes that break down or synthesize carbohydrates, lipids, and amino acids
• Having an extensive blood supply, the liver monitors and adjusts nutrient composition in circulating blood while holding significant energy reserves from glycogen deposits

Fatty Tissues

• Adipose tissue stores lipids, primarily triglycerides
• Adipocytes are located in many areas, primarily areolar tissue
• Mesenteries, red and yellow bone marrows, epicardium, and around eyes and kidneys also house fatty tissue
• Skeletel muslce maintains substantial glycogen reserves
• If other nutrients are unavailable, contractile proteins will be broken down and amino acids can be used as an energy source

Nervous Tissue

• Nervous tissue does not maintain reserves of carbohydrates, lipids, or proteins, requiring reliable supply of glucose
• Because of its metabolic requirements, nervous tissues cannot function in low-glucose conditions and the individual becomes unconscious
• Other peripheral tissues do not maintain large metabolic reserves, but can metabolize glucose, fatty acids, and other substrates where the energy source varies according to the endocrine system

Metabolic States

• Two patterns of daily metabolic activity to consider are the absorptive state and post absorptive state
• In the absorptive state, the period is follwoing a meal where nutrient absorption is underway for about four horus
• Normal blood glucose levels are maintained during during postabsorptive states where the body then relies on internal energy reserves
• Most cells break down lipids or amino acids during this postabsorbtive state
• Preserving glucose for use by nervous tissue

Catabolism and Ketones

• Lipid and amino acid catabolism release acetyl-CoA
• An increased concentration of acetyl-CoA causes ketone bodies to form
• A ketone body is an organic compound produced by fatty acid metabolism that then dissociates in solution, releasing a hydrogen ion

Ketones

• Acetoacetate, Acetone, and Betahydroxybutyrate are the three main types of ketone bodies
• Ketone bodies are not catabolized by liver cells, but peripheral cells absorb them from the blood, reconverting them to acetyl-CoA for the citric acid cycle
• Fasting produces ketosis, characterized by a high concentration of ketone bodies in body fluids
• Ketonemia involves the appearance of ketone bodies in the bloodstream
• Ketones lower blood pH, a process which must be controlled by buffers
• Prolonged starvation leads to ketoacidosis, marked by dangerous acidification of blood by ketone bodies due to accumulation; may cause coma, cardiac arrhythmias, and death

Nutrition

• The digestive tract must absorb fluids, organic nutrients, minerals, and vitamins to indefinitly maintain homeostasis
• Nutrition is based on the abosrbtion of nutrients from food where the body's requirement for each nutrient varies
• A balanced diet contains all the ingredients one needs for homeostasis
• An unhealthy state resulting from nutrient imbalance indicates malnutrition
• Complete proteins found in beef, fish, poultry, eggs, and milk, provides all essential amino acids in sufficient quantities

Food Groups

• Incomplete proteins are deficient in one or more essential amino acids and are found in plants
• Minerals are nonorganic ions released through dissociation of electrolytes
• Minerals are important because ions such as sodium and chloride determine osmotic concentrations of body fluids, play physiological roles, and are integral as enzymatic cofactors
• Bulk minerals like sodium, potassium, chloride, calcium, phosphorus, and magnesium are required
• Trace minerals such as iron, zinc, copper, manganese, cobalt, selenium, and chromium are also needed
• The body contains reserves of important minerals

Vitamins and Enzymes

• Vitamins are essential organic nutrients that are used as coenzymes in vital enzymatic reactions.
• The two groups of vitamins are based on chemical structure and characteristics that are either fat-soluble or water-soluble
• Vitamins A, D, E, & K are the fat-soluble vitamins must absorb with lipids, synthesize in sunlight through skin, or intestinal bacteria
• Vitamin A maintains epithelia and is required in synthesizing visual pigments
• Vitamin D must convert to calcitriol and is required for normal bone growth
• Vitamin E prevents the breakdown of vitamin A and fatty acids

Vitamin K and B-12

• Vitamin K is essential for the synthesis of clotting factors
• Because the body contains significant amounts of fat-soluble vitamins, normal metabolism can continue several months without dietary nutrients

Negative Conditions

• Vitamin dificiency, called Hypovitaminosis, is rare with fat-soluble vitamins
• Excess vitamin intake, called Hypervitaminosis, occurs when dietary intake exceeds the body's ability to use, store, or excrete a particular vitamin
• Water-soluble vitamins consist of the various components of coenzymes that are quickly exchanged between fluid in the digestive tract and circulation
• Typically, excesses are readily excreted in urine so, hypervitaminosis is relatively uncommon

Vitamines and Bacteria

• Bacteria in intestines produce five of the nine water-soluble vitamins as well as the fat-soluble vitamin K
• Intestinal epithelium only easily absorbs all water-soluble vitamins except B12, which must bind to an intrinsic factor before absorption due to its large molecule
• Metabolic rate is the average caloric expenditure that varies widely with activity
• Energy gains and losses occur when the body releases energy when chemical bonds are broken down, where the energy is then used to synthesize ATP in cells, and additional energy is lost as heat

Energy Management and Consumption

• Measuring energy requires heating: the amount of energy required to raise the temperature of 1 gram of water 1 degree Celsius is a calorie (cal) and the amount of energy required to raise the temperature of 1 kilogram of water 1 degree Celsius is a kilocalorie (kcal)
• Energy content of foods is tested by calorimetry using the measurment of total energy from the organic molecule breakdown with oxygen and water
• For every gram in the calorimetry test; lipids release 9.46 kcal/g, carbohydrates release 4.18 kcal/g, and proteins release 4.32 kcal/g

Metabolic Rate and Consumption

• Clinicians examine metabolic states when calories affect caloric needs
• Calories per hour, Calories per day, and Calories per unit body weight per day are affected yby exercise, age, sex, hormones, and climate
• Basal metabolic rate (BMR) is the rate at which the body expends energy while at rest to maintain vital functions
• You monitor your respiratory activity for to determine your Resting Metabolic Rate

Regulation

• Because energy use is proportional to oxygen consumption in resting individuals, the regulation of what you intake is essential for maintaining your needs
• Thyroxine controls overall metabolism
• Cholecystokinin (CCK) and adrenocorticotropic hormone (ACTH) suppress appetite
• Leptin is released by adipose tissues during absorptive state, which will communicate to your neurons to signal an appetite
• Ghrelin is released by a empty stomach and will stimulate your appetite

Obesity

• Having more than 20% of you body weight more than your ideal weight means you are obese
• Obesity is considered an epidemic
• Obesiity is primarily linked as an associated disease in cases of heart diseases, cancer, and diabetes

Urinary System Overview

• The urinary system removes most of body's cells metabolic wastes, specifically, the Kidneys remove it from circulation
• The kidneys produce urine

Urinary System Organs and Functions

• The urinary system contains paired kidneys that produce urine, and ureters that transport
• A urinary bladder is a muscular sac that holds and provides Urethra, or an exit tube
• Micturition is the process of expelling urine
• Because the muscles from teh bladder forces the urine out, homeostasis is met

Urinary System Functions

• The Three functions of the system: Excretion, Elimination, and Homeostatic regulations
• Exrection: Filtering wastes inside bodily fluids
• Elimination: Discharging bodily wastes
• Homeostatic regulations: Of volume and solute

Homeostatic functions withi the Urinary System

• Blood volume and blood pressure can regulate themselves by way of urine, and by realising erthropoeitin and renin
• Regulating levels of ions, such as sodium, potassium, sodium which are lost in urine with sodium ion levels are controlled through calcitriol
• Urinary System also conserves valuable nutrients, like urea to ensure we can safely keep removing bad sustances
• It assists the Liver in detoxication of poisons

Kidneys

• The Kidneys are located on elither side of a certable point
• the left kidney is slightly higher than the right kidney and the surface is capped by An adrenal gland
• The positing is supported by the peritoenum

Kidneys and their Layers

• The Kidneys are supportd by three layers: Fibrous capsule, Perinephric and Renal Fascia
• a fibrous capsule creates collagen fibers: It can protect the outer surfaces of many systems
• the Perinephric Fat tissue supports and wraps around a capsule
• Renal Fascia: Supports other structures and gives kidneys dense outer support and support from aditional systems

Kidney Composition

• The size can dictate the support of a system. (roughly 10 cm long, 5.5 cms whide, and 3 cms thick
• Hilium Supports many systems like " prominent medial indentation point: It supports the points for the renal arter, nerves, support from ureter, and renal veins

Sinus

• The Renal Sninus, Internal cavity within a kidney, that also helps stabalize the vessel positons
• The cortex protects superficial regions in contact with the capsule
• Renal pyramids: It makes 6-18 sections with a base and cortical adbods to support textures

Calyces

• They produce urine in the kidney lobe made of adrenal pyramids, cortex linings and tissue support
• With a discharge in a minor calyx, the ducts drain urine
• A Major calyces is formed by the minor variation
• The Pelvis is filled and connected via ureter

Blood

• To get sufficent protection for the body, 20/25% of outputs come from this process
• The average flow in kidney is about 1200 of fluid per minute
• the artery system requires the kidney blood vessels and veins that receive blood from such processes such as; the renal vessels

Arteries

• The vessel structure has Radiate outward, inter artery supply, and cortex support points to transfer to the Medulla to anchor arteries

Nerves and Nerves

Innvert systems to support flow through the Kidney/Ureter at Hilium points, allowing it to function in normal conditions for what's needed adjust Urine Formation based on blood amount

Kidneys

Composed of nephrons, Renal tubules and Renal Colosols for collection purposes

Renal

the composition supports vessels that give shape and protection

• The glomerular wall is also supported as the wall in the Renals are covered for maximum support