Human Physiology and Biochemistry PDF

J GONZALEZ HUMAN PHYSIOLOGY AND BIOCHEMISTRY Nutrition is of primary importance to the physiologic development and maintenance of the human body, a complex multicellular entity consisting of organ systems and tissues working together to support growth, maturation, defense, an...

J GONZALEZ HUMAN PHYSIOLOGY AND BIOCHEMISTRY Nutrition is of primary importance to the physiologic development and maintenance of the human body, a complex multicellular entity consisting of organ systems and tissues working together to support growth, maturation, defense, and reproduction (Medeiros and Wildman, 2012). In turn, the human body is composed of some 60 – 100 trillion cells. Each of these cells need to be nourished in order to grow, ingest “food”, excrete wastes, react to their environment, and reproduce (Gropper, Smith, and Carr, 2018).. nc I. The Cell , IIc  the average size of human cells is 5-10 micrometers  it is the basic, living, structural, and functional unit of the human body nn,  cells vary greatly in size, chemical composition, and function io  cells have specialized functions, but have basic similarities in terms of their common components  a typical cell usually has a plasma membrane, a nucleus, an endoplasmic reticulum, Golgi apparatus, and rit mitochondria uut II. Cellular Components (Gropper, Smith, and Carr, 2018) N N 1. Plasma membrane – a sheet-like structure surrounding and enveloping the cell  composed of proteins, cholesterol, and phospholipids dd phospholipids: have a hydrophobic and a hydrophilic portion/side, enabling them to form lipid ann bilayers - the fatty acid portion forms the hydrophobic part which prevents water-soluble compounds ha from entering the cell, and retains them within the cell - the glycerol and phosphate-containing portion are hydrophilic maintaining the cell’s aqueous tlht environments both outside the cell and the cell cytosol/cytoplasm aela cholesterol: it influences the fluidity and permeability of cell membranes, affecting substances that may pass into and out of the cell He proteins: integral and peripheral proteins are interspersed with the plasma membrane’s lipid nH bilayer and are responsible for the following functions: a. they mediate information transfer (as receptors) sini b. they transport ions and molecules (as channels, carriers, gates, and pumps) c. they act as cell adhesion molecules tnst d. they speed up metabolic activities (as enzymes) lnta 2. Cytoplasmic/Cytosolic Matrix- consists of a system of filaments/fibers (cytoskeleton) found within the tua cytosol the cytoskeleton provides cells with: unls a. structural support, defining the cell’s shape and helps maintain its function. b. a framework for positioning the various organelles (such as microvilli, which are extensions nso of intestinal cells). oC c. a network to direct the movement of materials and organelles within the cells. d. a means of independent locomotion for specialized cells (such as sperm, white blood cells) e. a pathway for intercellular communication among cellular components needed for cell C activation and survival; and f. possible transfer of RNA and DNA. the cytoskeleton is composed of 3 groups of fibers—microtubules, intermediate filaments, and microfilaments 6  J GONZALEZ 3. Mitochondrion – the primary site of oxygen use in cells, responsible for metabolic energy production in all cells, except the erythrocyte (Gropper, Smith, and Carr, 2018) the site of aerobic adenosine triphosphate (ATP) generation (Medeiros and Wildman, 2012) located within cells in areas near organelles with high energy demands such as the nucleus and ribosomes (site of protein synthesis) or near contractile myofibril in muscle cells it contains 2 lipid/protein bilayer membranes, comprising the outer and inner membranes the enzymes monoamine oxidase, acyl coenzyme A synthetase, glycerophosphate acyltransferase and phospholipase A are found in the outer membrane while adenylyl kinase and creatine kinase are found in the intermembrane space ZIc the inner membrane of the mitochondria is the site of oxidative phosphorylation and contains enzymes and cytochrome complexes of the electron transport chain n, LuEtritio 4. The Nucleus – it initiates and regulates most cellular activities due to its DNA content (Gropper, Smith, and Carr, 2018) the largest of the organelles within the cell a nuclear envelope surrounds the nucleus, composed of an inner and outer membrane, enabling communication between the nucleus and the cytoplasmic matrix and allows a continuous channel between the nucleus and endoplasmic reticulum N it contains substances such as minerals needed for nuclear function and DNA molecules; DNA encodes the cell’s genetic information together with all the enzymes needed for its duplication ZhAand inside the nucleus is the nucleolus which contains ribosomal RNA (rRNA), proteins, and DNA; the nucleolus is the site of rRNA transcription and processing as well as ribosome synthesis  encoded within the nuclear DNA are thousands of genes that direct protein synthesis, with each gene coding for a specific protein while the cell genome contains the entire set of genetic information (all Nealt the DNA in the cell) DNA replication enables the DNA to be copied entirely during mitosis  processes of protein synthesis: Os in H The cell receives a signal that protein synthesis is needed and protein biosynthesis occurs in 3 phases: 1. transcription – the process by which the genetic information (base sequence) in a single strand of DNA is used to specify a complementary sequence of bases in an mRNA chain 2. translation – the process by which genetic information in an mRNA molecule specifies the Gltant sequence of amino acids in the protein product - the genetic code specifying the amino acid sequence of a protein resides in the mRNA in the form of three-base sequences (codons) 3. elongation – the extension of the polypeptide chain of the protein product during protein J onsu synthesis a. new amino acids are incorporated until all the codons (corresponding to one completed protein) of the mRNA have been translated b. the process stops when signaled by a “nonsense” codon that does not code for any C amino acid c. the completed protein dissociates from the mRNA 5. Endoplasmic Reticulum (ER) and Golgi Apparatus – a structural mechanism for communication from the innermost part of the cell to its exterior (Gropper, Smith, and Carr, 2018)  ER – a network of membranous channels pervading the cytosol and providing continuity between the nuclear envelope, the Golgi apparatus, and the plasma membrane.  Golgi apparatus (network) – the part of the cell responsible for modifying macromolecules synthesized in the endoplasmic reticulum and packaging them to be transported to the cell surface or cytosol. 7  J GONZALEZ Classification of ER: a. rough (granular) endoplasmic reticulum (RER) – ribosomes are present - present in cells where protein synthesis is the main function (e.g., ribosomal RNA, structural protein) b. smooth (agranular) endoplasmic reticulum (SER) – ribosomes are absent - found in most cells but more abundant in cells that synthesize steroid hormones (e.g., adrenal. nc cortex and gonads) and in liver cells which synthesize lipoproteins , IIc Golgi apparatus – it functions together with the ER in trafficking and sorting proteins synthesized in the cell; a series of membrane sacks that process and package proteins after they leave the RER io nn, 2 tubular networks present: 1. cis-Golgi network – a compartment that accepts newly synthesized proteins coming from the ER rit 2. trans-Golgi network – the exit site of the Golgi apparatus; it sorts proteins for delivery to their next destination uut 6. Lysosomes and Peroxisomes – cell organelles filled with enzymes (Gropper, Smith, and Carr, N N 2018)  Lysosomes – cell organelles that contain digestive enzymes dd - found in all cells except red blood cells - about 36 enzymes are present in lysosomal membrane that can degrade proteins, ann polysaccharides, nucleic acids, and phospholipids ha  Peroxisomes – cell organelles containing enzymes that perform oxidative catabolic reactions tlht aela III. Cellular Proteins He 3 Functions of Cellular Proteins: (Medeiros and Wildman, 2012) nH 3. required for organelle and cell membrane structure, components of cell receptors, and have a critical role in cell signaling sini - organelles and cell membrane consist of a biphospholipid layer where proteins are embedded and may be ion channels or transport proteins tnst - cell receptor: a protein on the surface of a cell membrane to which other proteins can bind to initiate a specific cell reaction lnta - cell signaling consists of a series of biochemical reactions from the cell surface receptor to convey the message to a DNA promoter to exert the desired effect tua 2. can bind and react with other compounds or minerals toother parts of the cell unls Example: sodium-potassium ATPase pump uses ATP to force out sodium from inside to the outside of the cell and pump potassium into the cell nso 3. can act as components of ion channels and make up enzymes to facilitate biochemical reactions oC in the cell; all enzymes are made up of proteins Enzymes: Catalytic Proteins (Gropper, Smith, and Carr, 2018) C Enzymes are protein catalysts that increase the rate of a chemical reaction in the body. They are found in all cellular compartments acting as catalysts that take part in a reaction but are not part of the final product of the reaction (Gropper, Smith, and Carr, 2018). Characteristics of enzymes: 2. they have an “active site” where they bind with a substrate 8  J GONZALEZ - enzyme’s functional ability depends not only on its protein portion but also on a nonprotein prosthetic group or coenzyme/cofactor - the coenzyme may be B vitamins or minerals (e.g., Mg, Zn, Cu, Mn, Fe) acting as cofactor 3. an enzyme’s active site has high specificity - a substrate must “fit” perfectly into the specific shapes of the enzyme’s active site (the reacting parts of the substrate must be in close proximity to the reacting parts of the enzyme) 4. the velocity of an enzyme-catalyzed reaction (the number of substrate molecules reacted on in a specified time) increases if all the active sites on the enzyme are “filled” with substrate - as the substrate’s concentration increases, the number of substrate molecules available to the enzyme increases ZIc Classification of Enzymes based on the type of reaction catalyzed: n, 1. Oxidoreductases (dehydrogenases, reductases, oxidases, peroxidase, hydroxylases) - enzymes that catalyze reactions where one compound is oxidized and another is reduced LuEtritio Examples: enzymes found in the electron transport chain located on the inner membrane of the mitochondria cytochrome P450 enzymes located on the ER of liver cells 2. Transferases - enzymes where a functional group is transferred from one substrate to another Examples: transketolase, transaldolase, transmethylase, and transaminases N 3. Hydrolases (esterases, amidases, peptidases, phophatases, g glycosidases) - enzymes that catalyze cleavage of bonds between carbon atoms and another kind of atom by 4. ZhAand adding water Examples: digestive enzymes; enzymes contained within lysosomes Lyases (decarboxylases, aldolases, synthetases, cleavage enzymes, deaminases, nucleotide cyclases, hydrases or hydratases, dehydratases) - enzymes that catalyze cleavage of carbon-carbon, carbon-sulfur, and carbon-nitrogen bonds Nealt (excluding peptide bonds) without hydrolysis or oxidation-reduction Example: citrate lyase frees acetyl-CoA for fatty acid synthesis in the cytosol 5. Isomerases (racemases, epimerases, mutases) - enzymes that catalyze the interconversion of optical or geometric isomers Os in H Example: phosphohexose isomerase converts glucose-6-phosphate to fructose-6-phosphate in glycolysis which occurs in the cytosol 6. Ligases - enzymes that catalyze the formation of bonds between carbon and a number of other atoms, including oxygen, sulfur, and nitrogen Gltant Example: acetyl-CoA carboxylase, which starts fatty acid synthesis in the cytosol - acetyl-CoA carboxylase is attached to acetyl-CoA to form malonyl-CoA, the initial compound formed in fatty acid synthesis J onsu Hormones One region of the human body can communicate with another in two ways: (1) via nerve impulses and (2) via hormones (Medeiras and Wildman, 2012). Hormones are chemical messengers C synthesized and secreted by endocrine tissue (glands) and transported in the blood to target tissues or organs (Gropper, Smith, and Carr, 2018). - hormones are large protein and protein-based (i.e., glycoproteins), amino-acid based, or cholesterol-derived steroid molecules Examples: protein hormones – insulin, growth hormone, glucagon, antidiuretic hormone amino-acid hormones – epinephrine (from tyrosine), thyroid hormones (triiodo-thyronine and thyroxine steroid hormones (made from cholesterol) – testosterone, estrogens, cortisol, progesterone, aldosterone 9  J GONZALEZ - hormones are released in the blood and interact with specific receptor complexes on one or more tissues; only cells with a specific receptor for a given hormone will respond to a particular hormone Table 1. Select hormones related to nutrition and metabolism and their general function (Medeiros and Wildman, 2012) Source Hormone Principal Activity Pituitary gland Growth hormone Increases growth of most tissue by increasing protein synthesis and increasing fat utilization for energy. Prolactin Increases mammary milk formation during lactation nc Decreases water loss by kidneys by increasing water Antidiuretic reabsorption in nephrons , IIc hormone nn, Thyroid gland Thyroid hormone Increases rate of metabolism io Calcitonin Decreases Ca levels by increasing kidney loss and decreasing digestive absorption of Ca rit Parathyroid gland Parathyroid Increases blood Ca levels by increasing bone resorption Adrenal glands Aldosterone Increases Na reabsorption in kidneys uut Cortisol Increases glucose release in blood from liver by increasing gluconeogenesis N N Increases protein catabolism, which increases amino acid availability for gluconeogenesis dd Epinephrine Increases heart rate and stroke volume, increasing glucose (adrenalin) ann release into blood from liver Increases glycogen breakdown in liver & muscle ha Increases fat mobilization from fat cells Pancreas Insulin Increases glucose uptake by fat cells and skeletal muscle tlht Increases processing of fat and glycogen production and aela storage Increases amino acid uptake and protein production He Glucagon Increases fat release from fat cells Increases liver glycogen breakdown nH Increases glucose production in liver sini tnst Tissue - composed of similar cells performing similar or supportive tasks lnta 4 Kinds of Tissue: tua 1. Epithelial tissue unls - its lines surface such as blood vessels; the reproductive, digestive, and urinary tracts; ducts; and skin nso - there are 4 types of epithelial cells: simple squamous, stratified squamous, columnar, and cuboidal oC 2. Muscle tissue - composed of contractile muscle cells; it includes skeletal, cardiac, and smooth muscle cell types 3. Nervous tissue C - it allows for communication and sensory perception; includes the central and autonomic nervous systems and other nerves 4. Connective tissue: the most abundant, widely distributed, and varied type of tissue - it is a thin mesh or webbing that helps hold tissue and organs together; it also provides strong fibers for bones, cartilage, and tendons 10  J GONZALEZ Organ Systems - composed of two or more kinds of tissue - groups of organs arranged in a manner so that they can perform a function more complex than any of the organs independently. The human body’s 11 organ systems are shown in Table 2. Table 2. Organ Systems (Medeiros and Wildman, 2012) Organ System Tissue or Organs Involved ZIc Integumentary Skin, hair, nails, sense receptors, oil glands Skeletal Bones and joints n, Muscular Muscles LuEtritio Nervous Brain, spinal cord, nerves Circulatory Heart, blood vessels Lymphatic Lymph nodes, lymph vessels, thymus, spleen, tonsils Respiratory Nose, pharynx, larynx, trachea, bronchi, lungs Digestive Mouth, teeth, salivary glands, tongue, pharynx, esophagus, stomach, small intestine, large intestine, rectum, anal canal, liver, gallbladder, pancreas N Urinary Kidneys, ureters, urinary bladder, urethra Reproductive (male) Testes, ductus deferens, urethra, prostate, penis, scrotum ZhAand Reproductive (female) Ovaries, uterus, uterine (fallopian) tubes, vagina, vulva, breasts Nealt Os in H Gltant J onsu C 11