Nutrients and Metabolism

Nutrients

• Nutrients consist of essential elements and molecules required by the body

Metabolic Activity

• Involves breaking down organic molecules to obtain energy
• Energy released is stored as ATP
• ATP then fuels the construction of new organic molecules

Energetics

• It describes how the body balances heat gains and losses

Requirements for Cellular Reactions

• Cells need oxygen and various nutrients, including water, vitamins, mineral ions, and organic substrates, to carry out reactions

Metabolism

• It is the sum of all chemical and physical changes occurring in body tissues
• It includes catabolism and anabolism

The Nutrient Pool

• The nutrient pool consists of all nutrient molecules available and distributed in the blood

Catabolism

• It is the process of breaking down large molecules into smaller ones
• This breakdown releases energy, which is then used to synthesize ATP

Anabolism

• It involves converting small molecules into larger ones
• The synthesis of new organic compounds forms new chemical bonds

Functions of Anabolism

• Anabolism functions to perform structural maintenance, support growth, produce secretions, and store nutrient reserves

Nutrient Reserves

• Triglycerides are the most abundant storage lipids, primarily consisting of fatty acids
• Glycogen: The most abundant storage carbohydrate, is a branched chain of glucose molecules
• Proteins: Proteins are the most abundant organic components in the body and perform vital functions

Energetics Definition

• Energetics studies the flow of energy and its change from one form to another

Oxidation and Reduction Reactions

• Oxidation and reduction reactions always occur together
• Oxidation involves the loss of hydrogen or electrons
• The electron donor in oxidationis oxidized
• Reduction involves the gain of hydrogen or electrons
• The electron recipient in reduction is reduced

Role of Electrons

• Electrons carry chemical energy

Redox Reactions

• In a redox reaction, a reduced atom or molecule gains energy
• An oxidized atom or molecule loses energy
• Some energy releases in redox reactions is in the form of heat
• Remaining energy can be used for physical or chemical work, such as forming ATP

The Electron Transport Chain

• The electron transport chain (ETC) is a sequence of protein complexes located in the mitochondria
• Electrons pass through the ETC via a series of oxidation-reduction reactions
• Electrons ultimately are transferred to oxygen
• As electrons combine with oxygen and hydrogen ions, water is formed

Coenzymes

• Coenzymes play a key role in the flow of energy within a cell and act as intermediaries
• They accept electrons from one molecule and transfer them to another
• NAD and FAD are examples of coenzymes
• They remove hydrogen atoms from organic molecules
• Each hydrogen atom has one electron and one proton
• Coenzymes are reduced when they accept a hydrogen atom

Coenzyme FAD

• Specifically, coenzyme FAD accepts two hydrogen atoms, gaining two electrons, and forming FADH2

Coenzyme NAD

• NAD+ is the oxidized form and has a positive charge
• It accepts two hydrogen atoms, gaining two electrons, and releases one proton, forming NADH

Carbohydrate Catabolism

• This process generates ATP and other high-energy compounds

Cellular Respiration

• In cellular respiration, glucose plus oxygen yields carbon dioxide plus water
• It involves glycolysis, citric acid cycle, and the electron transport chain
• Complete cellular respiration of one glucose nets 30-32 ATP molecules

Glycolysis Definition

• Glycolysis breaks down glucose in the cytosol into smaller molecules that mitochondria can use
• It is an anaerobic reaction, not requiring oxygen
• Glycolysis breaks 6-carbon glucose into two 3-carbon molecules of pyruvic acid (pyruvate)
• It begins when an enzyme phosphorylates a glucose molecule, creating glucose-6-phosphate

Glycolysis Requirements

• For glycolysis to take place, glucose molecules, appropriate enzymes, ATP, ADP, inorganic phosphate groups, and NAD as a coenzyme are needed

Aerobic Metabolism Location

• Aerobic metabolism occurs inside mitochondria and requires oxygen
• It produces lots of ATP from pyruvate breakdown, involving citric acid cycle and electron transport chain

Mitochondrial Membranes

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

Citric Acid Cycle

• During citric acid cycle, removal of hydrogen atoms from pyruvate by coenzymes becomes primary source of energy gain
• Carbon and Oxygen atoms are removed and released as CO2

Decarboxylation

• In the Mitochondrion, Pyruvate interacts with NAD and coenzyme A (CoA).
• The result is producing 1 CO2, 1 NADH and 1 acetyl-CoA (acetyl group bound to CoA).

Citric Acid Cycle

• Acetyl group transfers from acetyl-CoA to a 4-carbon oxaloacetate molecule.
• This produces a 6-carbon citric acid
• CoA is released to bind to another acetyl group
• Citric acid cycle removes two carbon atoms and regenerates a 4-carbon chain
• Several steps involve more than one reaction or enzyme
• H2O molecules are tied up in two steps
• One citric acid cycle produces one molecule of GTP (guanosine triphosphate) through substrate-level phosphorylation

Citric Acid Cycle Summary

CH3CO  CoA + 3NAD + FAD + GDP + Pi + 2H2O →
CoA + 2CO2 + 3NADH + FADH2 + 2H+ + GTP

Oxidative Phosphorylation

• Oxidative phosphorylation generates ATP through the transfer of electrons from NADH and FADH2 to oxygen and by a sequence of electron carriers within mitochondria
• Over 90% of ATP the body uses is produced by this process
• The basis of oxidative phosphorylation is the formation of water

2H2 + O2 → 2H2O

Electron Transport Chain (ETC)

• ETC protein complexes are located in the inner mitochondrial membrane, where the reactions of oxidative phosphorylation takes place
• Cytochrome molecules (4 respiratory protein complexes, coenzyme Q, and electron carriers) make up each cytochrome
• Each cytochrome has pigment (contains metal ion) and protein (surrounds pigment)

Oxidative phosphorylation

• Oxidative phosphorylation provides 95% of the ATP, requires oxygen and electrons and availability limits the rate of ATP generation
• Cells obtain oxygen by diffusion from extracellular fluid

Energy Yield of Glycolysis and Aerobic Metabolism

• Energy yield of glycolysis and aerobic metabolism begins with glucose and ends with carbon dioxide and water

Glycolysis

• Glycolysis breaks down 1 glucose into 2 pyruvate molecules
• The cell gains a net 2 molecules of ATP

NADH Passing Electrons

• 2 NADH molecules pass electrons to FAD
• The pass by an intermediate electron carrier in the intermembrane space, then to ETC

Citric Acid Cycle

• The citric acid cycle require two revolutions to break down 2 pyruvate molecules
• Each revolution yields 1 ATP by way of GTP
• An additional 2 ATP are gained
• In this process, H atoms are transferred to NADH and FADH2
• Coenzymes provide electrons to ETC

Electron Transport Chain

• For every 1 glucose, a total of 10 NADH and 2 FADH2 deliver electrons to ETC
• Each NADH yields 2.5 ATP
• Each of the 8 NADH from the citric acid cycle yields 2.5 ATP and 1 water molecule
• Each FADH2 yields 1.5 ATP
• Each of the 2 FADH2 from glycolysis yields 3 ATP and 2 water molecules
• 23 ATP is the total yield from ETC

ATP Production Summary

• For each molecule of glucose processed, a cell gains 30–32 molecules of ATP
• 2 from Glycolysis
• 3-5 from NADH generated from Glycolysis
• 2 from the Citric acid cycle (by means of GTP)
• 23 from the ETC
• All but 2 ATP are produced in mitochondria

Gluconeogenesis

• is the Process of Synthesis of glucose from noncarbohydrate molecules
• 3-carbon molecules other than pyruvate are included

Liver and Skeletal Muscles

• Glucose is stored as glycogen in liver and skeletal muscle

Glycogenesis

• Glycogenesis is the formation of glycogen from excess glucose
• It Involves several steps
• Requires high-energy compound uridine triphosphate (UTP)

Glycogenolysis

• Glycogenolysis is the breakdown of glycogen to glucose monomers
• This process occurs quickly
• Involves a single enzymatic step

Lipids

• Lipids contain carbon, hydrogen, and oxygen in different proportions than in carbohydrates
• Triglycerides are the most abundant lipid in the body

Lipid Catabolism (Lipolysis)

• Lipid catabolism breaks lipids down into pieces that can be converted to pyruvate or channeled directly into citric acid cycle

Hydrolysis of Triglycerides

• Hydrolysis splits triglyceride into 1 molecule of glycerol and 3 fatty acid molecules
• Cytosol enzymes convert glycerol to pyruvate, which is then converted to acetyl-CoA to partake in citric acid cycle

Lipids and Energy Production

• A cell can gain 120 ATP from the breakdown of one 18-carbon fatty acid molecule, which is almost 1.3 times the energy gained from the breakdown of three 6-carbon glucose molecules

Lipid Synthesis (Lipogenesis)

• Lipogenesis uses almost any organic substrate, because lipids, amino acids, and carbohydrates can be converted to acetyl-CoA, which can then be converted to glycerol synthesized from dihydroxyacetone phosphate, an intermediate product of glycolysis and gluconeogenesis

Lipid Synthesis

• Nonessential fatty acids and steroids are synthesized from acetyl-CoA

Essential Fatty Acids

• Essential fatty acids cannot be synthesized in the body and must be consumed
• Linoleic acid and linolenic acid, which are 18-carbon unsaturated fatty acids in plants, are examples of essential fatty acids

Lipid Storage

• Lipid storage provides important energy reserves
• It also can provide large amounts of ATP, but slowly
• Water-soluble enzymes may have difficulty in reaching lipid storage

Lipid Transport and Distribution

• Lipid transport is important because cells require lipids to maintain plasma membranes, and steroid hormones must reach their target cells

Soluble Lipids

• Special transport mechanisms carry lipids because most lipids are not soluble in water
• Most lipids circulate through the bloodstream as lipoproteins

Free Fatty Acids

• Free fatty acids make up a small percentage of total circulating lipids
• Free fatty acids can diffuse easily across plasma membranes
• in the blood, they are generally bound to albumin

Sources of Free Fatty Acids in Blood

• Sources of FFAs in blood include those not used in synthesis of triglycerides that diffuse from the intestinal epithelium
• Also consists of those that diffuse out of lipid reserves when triglycerides are broken down

Important Energy Source

• Free fatty acids serve as an important energy source during periods of starvation, when glucose supplies are limited
• Cells in the liver, cardiac muscle, and skeletal muscle can metabolize free fatty acids

Lipoproteins

• Lipoproteins are lipid-protein complexes
• Lipoproteins contain large insoluble glycerides and cholesterol
• Lipoproteins have four groups
  • Chylomicrons
  • Very low-density lipoproteins (VLDLs)
  • Low-density lipoproteins (LDLs)—“bad cholesterol”
  • High-density lipoproteins (HDLs)—“good cholesterol”

Chylomicrons

• Chyloicrons as the largest lipoproteins
• They are produced by intestinal epithelial cells from fats in food
• They Carry absorbed lipids into lymph and then into the bloodstream

Protein Metabolism

• The body synthesizes 100,000 to 140,000 different proteins, each with a different structures and functions from only 20 amino acids
• Proteins function as enzymes, hormones, structural elements, and neurotransmitters
• Very little protein is used as an energy source

Amino Acid Catabolism

• In order for proteins to be used as energy, they must be converted into substances that can enter the citric acid cycle
• This process involves transamination, deamination, and the urea cycle
• Removal of amino group requires a coenzyme derivative of vitamin B6

Transamination Definition

• Attaches amino group of amino acid to keto acid
• Converts keto acid into amino acid
• Leaves mitochondrion and enters cytosol
• Available for protein synthesis

Deamination Definition

• Prepares amino acid for breakdown in the citric acid cycle by removing the amino group and hydrogen atom by generating a toxic ammonium ion

Deamination

• Generates ammonium ions in liver cells
• Liver cells have enzymes that remove toxic ammonium ions by synthesizing urea in the cycle

Urea

• Urea is a harmless water-soluble compound excreted in urine

Amino Acids and ATP Production

• Liver cells initiate protein catabolism to provide increased atp supply
• When glucose and lipid reserves are inadequate, liver cells that break down internal proteins will absorb additional amino acids from the blood

Amino Acids deaminated

• After being absorbed, the Amino acids are deaminated, meaning their carbon chains are sent to mitochondria
• Not all Amino acids enter cycle at same point
• ATP benefits vary

Protein Catabolism Complications

• Complex structural proteins are more difficult to break apart than are complex Carbohydrates or lipids
• One by-product (ammonium ions) is toxic to cells
• Proteins form the important structural and functional components

Protein Synthesis

• The body synthesizes half of the amino acids needed to build proteins
• Ten essential amino acids, Eight are essential and two are insufficiently synthesized
• The others are Nonessential, with amino acids are made by the body on demand given sufficient amination

Nutrient Requirements

• Each tissue has needs corresponding to the type and quantities of enzymes in cells

Metabolic Tissues

• Five: Liver; Adipose Tissue; Skeletal muscle; Nervous tissue; Other peripheral tissues

Liver

• It is the focal point of metabolic regulation and control with a Great diversity of enzymes that break down or synthesize carbohydrates, lipids, and amino acids

Hepatocytes

• Have an extensive blood supply
• It can Monitor and adjust nutrient composition of circulating blood
• It can accumulate significant energy reserves (glycogen deposits)

Adipose Tissue

• It Stores lipids, primarily as triglycerides
• Adipocytes are located areolar tissue, mesenteries, red or yellow bone marrows, the epicardium, and around eyes

Skeletal Muscles

• Maintain substantial glycogen reserves
• When other nutrients are unavailable
• Contractile proteins can be broken down
• Amino acids can be used as an energy source

Nervous Tissue

• Do not maintain reserves of carbohydrates, lipids, or proteins
• Requires reliable supply of glucose to function

Non-functional CNS cells

• CNS cannot function in low-glucose conditions
• The individual becomes unconscious if blood glucose levels are too low

Peripheral tissues

• Are not metabolically reliable
• they Can metabolize depending on the glucose, fatty acids, and many other substrates
• Have a varying, preferred energy source
• This may be is according to instructions from the endocrine system

Daily Metabolic Activities

• There are Two Patterns of daily metabolic activity

Absorptive State

• The period following the meal
• Nutrient absorption that under way
• Approximately 4 hours

Postabsorptive State

• Normal blood glucose levels are maintained
• The body relies on Internal energy reserves
• Most cells break down lipids or amino acids
• Preserving glucose for use by nervous tissue

Lipid and Amino Acids

• Lipid and Amino acid products Generate acetyl-CoA
• An increased concentration of acetyl-CoA
• Causes ketone bodies to form
• Ketone bodies result in an Organic compound produced by fatty acid metabolism
• Ketone bodies Dissociates in solution, releasing a hydrogen ion

Three Types of Ketone Bodies

• Acetoacetate
• Acetone
• Betahydroxybutyrate

Non-liver Catabolism

• These products are Not catabolized by liver cells
• In addition, peripheral cells absorb them from blood
• Reconvert them to acetyl-CoA for citric acid cycle

Ketosis

• Fasting produces ketosis-A High concentration of ketone bodies results in body fluids
• It Lowers the blood pH, which must be controlled by buffers

Prolonged Starvation

• Prolonged starvation leads to ketoacidosis- a Dangerous acidification of blood by ketone bodies
• This process May cause coma, cardiac arrhythmias, and death

Nutrition

• To maintain indefinitely homeostasis
• The digestive tract must absorb fluids, organic nutrients, and minerals
• Add vitamins

Poor Nutrition

• Poor Nutrition results from theAbsorption of nutrients from food
• The body's requirement for the particular nutrient varies.
• Leads to an Unhealthy state resulting from nutrient imbalance

Optimal Nutrition

• A balanced Diet, contains all ingredients needed for homeostasis
• Also includes Complete proteins, an ingredient that Provides all essential amino acids in sufficient quantities
• Can be obtained from Beef, fish, poultry, , and milk
• In order to be a healthy diet, there needs to be a mix of Incomplete proteinsDeficient containing one or more essential amino acids
• Obtained from plants

Minerals

• Minerals are Inorganic ions released through dissociation of electrolytes
• Important to controlling osmotic Concentrations , acting as cofactors, participating in physiological processes

Bulk Minerals

• Sodium, potassium, chloride, calcium, phosphorus, and magnesium

Trace Minerals

• Iron, zinc, copper, manganese, cobalt, selenium, and chromium

Vitamin types

• Body contains various crucial minerals
• Vitamins that are essential function as coenzymes supporting the Reactions
• Two classifications Based on the chemical structures as Either fat or water-soluble

Fat soluble Vitamins

• Consist of Vitamins A, D, E, and K
• Absorbed primarily from the digestive tract along with lipids of micelles
• While the Skin synthesizes small amounts of vitamin D when exposed to sunlight
• And Intestinal bacteria produce some vitamin K

Vitamin A

• Functions to Maintain epithelia
• and is Required for synthesis of visual pigments

Vitamin D

• Converted to calcitriol
• and is Required for normal bone growth

Vitamin E

• Prevents the breakdown of vitamin A and fatty acids

Vitamin K

• Essential for synthesis of clotting factors

Vitamin Reserves

• The Human body contains notable reserves of fat-soluble vitamins that help maintain normal metabolism for months without dietary sources
• In Contrast, Hypovitaminosis—vitamin deficiency
• Rare in fat-soluble vitamins
• Too much of the right thing will Lead to Hypervitaminosis
• When dietary intake exceeds ability to use, store, or excrete vitamin
• And a Vitamin store increase is more detrimental to fat based vitamins

Water-Soluble Vitamins

• Are components of coenzymes, these Vitamins support the body through Rapid exchange between fluid in digestive tract and circulating blood
• Excesses are readily excreted
• Which makes Hypervitaminosis is relatively rare for water-based vitamins

Bacteria

• Bacteria is located in the intestines
• and Bacteria provide Five of the nine water-soluble vitamins
• and Fat-soluble vitamin K

Intestinal Epithelium and Vitamin B-12

• The intestinal epithelium easily absorbs all water-soluble vitamins exceptB12
• The B12 molecule is large
• And Molecule 12, Must bind to the complex before passing out

Metabolic Rate and Thermoregulation

• Metabolic rate - Is the Average caloric expenditure of a human
• Daily energy use varies

Average human energetics

• Energy gains = Energy released
• Energy is released from broken chemical bonds
• This energy release is used to synthesize ATP in cells
• Some energy is lost as heat

Measurement

• It takes a certain amout of energy to change water 1kg by 1C
• One Calorie = Energy to raise 1kg H20 by 1C
• One calorie = Energy to raise 1g H20 by 1C

Energy content of Food

• is measured using calorimetry
• This method Measures total energy released when bonds of organic molecules are broken
• It is Determined by burning food with oxygen and water in a calorimeter
• Lipids release approximately 9.46 kcal/g when burned
• Carbohydrates: 4.18 kcal/g is the amount they release when burned
• Proteins will release an energy value of 4.32 kcal/g, on average

Metabolic Rate

• It is Evaluated according to a patient-by-patient basis to Determine an individual’s typical energy use
• Results are as Expressed as Calories per hour / Calories per day
• Exercise, age, gender, hormones all play a role
• Calories per unit body weight per day
• Are all relevant, compounding, metrics

Base Metabolic Rate

• Base Metabolic Rate (metabolic standard) is the resting level a body will expend energy to maintain vital health
• the Minimum energy expended to maintain life for a sentient person

Base measuring

• Measuring this is measured by observing the human O2 levels