BSCI 201 (Anatomy & Physiology I) Study Guide for Exam 1
BSCI 201 (Anatomy & Physiology I) Study Guide for Exam 1 BSCI201
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BSCI 201- Exam 1 Study Guide by Mehrnaz Ighani . Anatomy: study of the structure of the body parts and their relationships to one another. . . .Physiology: study of the function of the body parts . Subdivisions of Anatomy: 1. Gross/ Macroscopic Anatomy: study of large, visible structures Regional Anatomy: All structures in a particular area of the human body System Anatomy: Analyzes one organ system Surface Anatomy: Looks at internal structures and how they relate to the skin 2. Microscopic Anatomy: Study of small structures that can’t be seen with the naked eye Cytology: the study of cells Histology: the study of tissues 3. Developmental Anatomy: Study of the anatomical and physiological throughout life Embryology: study of developments before birth When studying anatomy one must be able to observe, manipulate, examine, and know anatomical terminology . Subdivisions of Physiology: o Based on organ systems o Based on cellular and molecular levels of the human body When studying physiology you have to understand physical and chemical principles . Principle of Complementarity of Structure and Function: Function ALWAYS reflects structure . Structural Organization: (Fig. 1.1) Chemical > Cellular > Tissue > Organ > Organ system > Organismal Chemical level: atoms, molecules, and organelles Cellular level: single cell Tissue level: a group of similar and specific cells Organ level: contains at least 2 or more tissue types Organ system level: organs that work closely together Organismal level: all organs work together to maintain homeostasis . Requirements for life: Maintaining boundaries Movement Responsiveness Digestion Metabolism Excretion Growth Reproduction . Maintaining boundaries: separation between internal and external environments must exist (Ex. Plasma membrane and skin) Movement: movement of body parts via skeletal muscles and movement of substances via cardiac and smooth muscles Contractility: movement at the cellular level . Responsiveness: ability to sense and respond to stimuli (Ex. reflex) . Digestion: breakdown of food and absorption of nutrients . Metabolism: chemical reactions that occur in the cells (Ex. catabolism & anabolism) . Excretion: removal of waste from metabolism and digestion (Ex. CO2 and urea) . Growth: increase in size of a body part/ organism . Reproduction: at the cellular level, reproduction means division of cells and at the organismal level, reproduction means production of offspring . Humans are multicellular and all cells depend on organ systems to meet their survival needs. . There are 10 organ systems: (Fig. 1.2) Integumentary system Nervous system Endocrine system Digestive system Respiratory system Urinary system Skeletal system Muscular system Cardiovascular system Lymphatic system NOTE: The reproductive system is an organ system but it is not required to maintain homeostasis . Integumentary system: o Synthesizes vitamin D o Houses sensory receptors o Contains the largest organ of the body: Skin o Protects internal tissues . Skeletal system: o Stores minerals o Forms red blood cells o Supports body organs . Muscular system: o Contractibility o Heat production o Movement o Stability o Maintain balance and posture . Nervous system: o Gathers sensory input and forms motor output . Endocrine system: o Glands produce hormones that regulate the activity of cells and organs o Regulates growth, metabolism, and sexual function . Cardiovascular system: o Provides nutrients through the blood o Dispose of metabolic wastes o Hormone delivery o Transports O2 and CO2 . Lymphatic system: o Removes interstitial fluid from tissues o Transports white blood cells o Body’s defense mechanism against infection and disease . Respiratory system: o Take in O2 and expel CO2 o Smelling o Air vibrating the vocal cords creates sound . Digestive system: o Digestion of food and absorption of macromolecules, vitamins, and minerals o Eliminate undigested food through the anus . Urinary system: o Balances the pH of the blood o Regulates electrolytes and water o Eliminates nitrogenous waste through the urinary bladder . Reproductive system: o Male reproductive system: Produces male sex hormone and sperm o Female reproductive system: Ovaries produce eggs and female sex hormones and mammary glands produce milk to nourish the newborn . Survival needs: Nutrients O2 Water Normal body temperature Appropriate atmospheric pressure Homeostasis: Maintenance of stable internal conditions despite continuous change in environment o Nervous and endocrine systems are the main controllers o A dynamic state of equilibrium, always readjusting as needed o Variables: Factors that can change (Ex. Blood sugar) Homeostatic control of variables: 1. Receptor 2. Control center 3. Effector o Receptor (sensor): monitors the environment and responds to stimuli o Control center: receives input from receptor and determines appropriate response. It also determines set point at which variable is maintained o Effector: receives output from the control center and provides the means to respond. Respond increases stimulus + feedback) or decreases stimulus ( feedback). + feedback: Increases the original stimulus Controls infrequent events that don’t need continuous readjustment Ex: Blood clotting feedback: Most used feedback in the body Decreases or shuts off original stimulus Ex: Regulation of body temperature . Homeostatic Imbalance: Increased risk of disease Contributes aging Control systems become less efficient If feedback mechanisms become overwhelmed, destructive + feedback mechanisms take over . Anatomical terms: Anatomical position: Feet slightly apart, palms facing forward with the thumbs pointing away from the body Directional terms: Describe one body structure in relation to another body structure. It’s ALWAYS based on standard anatomical position . Directional terms: (Table 1.1) Superior (cranial): toward the head, upper Inferior (caudal): toward the feet, lower Anterior: front (same as ventral) Posterior: back (same as dorsal) Medial: toward the midline of a structure Intermediate: between a more medial and a more lateral structure Lateral: away from the midline of a structure Proximal: toward the trunk Distal: away from the trunk Superficial: nearer the body surface Deep: farther away from the body surface Examples: The neck is superior to the abdomen The stomach is medial to the arm The heart is intermediate to the lungs The ankle is distal to the knee The knee is inferior to the abdomen . Regional terms: label specific areas within the body divisions 2 major divisions: 1. Axial (head, neck, and trunk) 2. Appendicular (upper and lower extremities) . Body planes: surfaces along which body or structures may be cut for anatomical study 3 most common planes: Sagittal plane Frontal (coronal) plane Transversal (horizontal) plane . Sections: cuts made along a body plane Ex. A transversal cut results in a transversal section Sagittal plane: lengthwise plane that divides a structure into right and left sections Parasagittal plane: sagittal plane that divide the body into 2 unequal halves Midsagittal plane: sagittal plane that divide the body into 2 equal halves Frontal plane: lengthwise plane that divides a structure into superior and inferior sections Oblique section: results of cuts at an angle other than 90 degrees (Fig. 1.8) Body cavities: contain wellordered arrangements of internal organs that protect the organs within them and prevent the spread of infection .2 sets of cavities: 1. Dorsal body cavity 2. Ventral body cavity Dorsal body cavity: (Fig. 1.9) 1. Cranial cavity (brain) 2. Vertebral body cavity (spinal cord) Ventral body cavity: 1. Thoracic cavity 2. Abdominopelvic cavity Houses the internal organs called the Viscerae NOTE: The 2 subdivisions are separated by the diaphragm Thoracic cavity: 1. 2 pleural cavities (houses the lungs) 2. Mediastinum: contains pericardial cavity and surrounds other thoracic organs 3. Pericardial cavity (houses the heart) Abdominopelvic cavity: 1. Abdominal cavity (contains stomach, liver, pancreas, and etc.) 2. Pelvic cavity (contains kidneys, urinary bladder, and etc.) . Membranes of the ventral body cavity: Serosa aka serous membrane: double membraned layer that covers the surface of the ventral body cavity Parietal serosa: lines the walls of the ventral body cavity Visceral serosa: covers the organs within the ventral body cavity NOTE: 2 membranes are separated with serous fluid that’s secreted by both membranes . Abdominopelvic has 4 quadrants and 9 regions: 4 quadrants: (Fig. 1.11) Left upper quadrant Right upper quadrant Left lower quadrant Right lower quadrant 9 regions: (Fig. 1.12) Right hypochondriac region Epigastric region Left hypochondriac region Right lumbar region Umbilical region Left lumbar region Right iliac (inguinal) region Hypogastric region Left iliac (inguinal) region In addition to 2 main body cavities, there are other smaller cavities: Oral and digestive cavities Nasal cavity Orbital cavities (eye sockets) Middle ear cavities Synovial cavities (joints) . Chemistry: the basis of all physiological reactions such as movement, digestion, metabolism, and etc. . Chemistry has 2 subdivisions: 1. Basic chemistry 2. Biochemistry . Matter: any object that has mass and occupies space Weight is mass+ the force of gravity . 3 states of matter: 1. Solid: defined shape and volume 2. Liquid: changeable shape but defined volume 3. Gas: changeable shape and volume . Energy: the capacity to do work or put matter into motion Doesn’t have mass, nor does it take up space The greater the work done, the more energy needed . Energy exists in 2 forms: 1. Kinetic energy (energy in action) 2. Potential energy (stored energy) Energy can be transformed from potential energy to kinetic energy and stored energy can be released, resulting in action . Forms of energy: 1. Chemical energy: stored in bonds of chemical substances 2. Electrical energy: results from movement of charged particles 3. Mechanical energy: directly involved in moving matter 4. Radiant/ electromagnetic energy: travels in waves such as x- rays . Energy form conversions: 1. Energy can be converted from one form to another Ex: turning on a lamp converts electrical energy to light energy 2. Energy conversion is inefficient . Some energy is lost as heat . Atoms and elements: All matter is composed of elements . Elements: substances that cannot be broken down into simpler substances by ordinary chemical methods 4 elements makeup 96% of the human body: . C, H, O, and N . 9 elements makeup 3.9% of body . 11 elements makeup <.01% of body All elements are made up of atoms . Atoms give each element its particular physical and chemical properties Atomic symbol: one or two letter chemical shorthand for each element . Common elements composing the body: Oxygen: component of both organic and inorganic molecules. Needed for the production of ATP Carbon: component of all organic compounds such as carbs, lipids, proteins, and nucleic acids Hydrogen: component of all organic compounds. As an ion it influences the pH Nitrogen: component of proteins and nucleic acids . Atoms are composed of 3 particles: Protons: + charged and weighs 1 atomic mass units (amu) Neutrons: no charge ad weighs 1 amu Electrons: - charged and have virtually no weight . Structure of atoms: (Fig. 2.1) o In a neutral atom # of protons= # of electrons o Protons and neutrons are located in the nucleus o Chemists devise models of how atomic particles are put together: . Planetary model . Orbital model . Identifying elements: (Fig. 2.2) Identifying facts about an element include its atomic number, mass #, isotopes. And atomic weight Atomic #: number of protons (subscript of atomic symbol) Mass #: number of protons plus neutrons (superscript of atomic symbol) Isotopes: atoms that contain same # of protons but differ in the number of neutrons Atomic weight: average of mass numbers of all isotopes forms of an atom . Radioisotopes: isotopes that decompose to more stable forms Atom loses various subatomic particles As isotope decays, subatomic particles that are being given off release a little energy known as radioactivity All radioactivity can damage living tissue and cancer, but some types can be used to destroy localized tissue cancers . Molecules and compounds: Atoms chemically combine with other atoms to form molecules and compounds Molecule: two or more atoms bonded together Compound: specific molecule that has two or more different kinds of atoms bonded together such as glucose . Mixtures: (Fig. 2.4) Two or more components that are physically intermixed 3 types of mixtures: 1. Solutions: solute particles are very tiny 2. Colloids: solute particles are larger than the ones in a solution 3. Suspensions: solute particles are very large and might scatter light Solutions: Homogenous mixtures Solvent: substance present in greatest amount Solute: substance dissolved in solvent True solutions are usually transparent such as air and most solutions in body Concentration of true solutions: o 3 common ways to express concentrations: 1. % of solute in total solution 2. Mg/dl (milligrams per deciliter) . Ex. Normal blood fasting glucose levels are 80 mg/dl 3. Molarity (M): . The # of moles of solute/ liter of solvent . 1 mole of a compound= molecular weight in g . 1 mole of any substance contains 6.02x10^23 molecules of that substance called the Avogadro’s # Colloids: Aka Emulsions are heterogeneous mixtures Can see large solute particles in solution that do not settle out Some undergo solution to gel (sol-gel) transformations such as Jell-O Suspensions: Heterogeneous mixtures that contain large solutes that settle out Blood is a suspension because if left in a tube, the blood cell will settle out . Chemical bonds: Energy relationships between electrons of reacting atoms, they are not actual physical structures Electrons are involved in all chemical reactions and they determine whether a chemical rxn will take place and if so what type of chemical bond is formed . Role of electrons in chemical bonding: Electrons occupy in electron shells Each electron shell contains electrons that have a certain amount of kinetic energy and potential energy so shells are referred to as energy levels Shells can hold only a specific # of electrons and the first shell is filled first 1 shell: 2 electrons 2ndshell: 8 electrons rd 3 shell: 18 electrons Octet rule: atoms desire 8 electrons in their valence shell ( Fig. 2.5) This desire is the driving force behind chemical reactions Most atoms do not have full valence shells . Types of chemical bonds: 1. Ionic 2. Covalent 3. Hydrogen Ionic bonds: (Fig. 2.6 ab) Ions: atoms that have gained or lost electrons and become charged # of electrons do not equal # of protons Attraction of opposite charges results in an ionic bond Ionic bonds involve the transfer of valence shell electrons from one atom to another one One atom becomes an anion and the other one becomes a cation Most ionic compounds are salts Covalent bonds: ( Fig. 2.7a, b, and c) Formed by sharing two or more valence shell electrons between two atoms . Sharing 2 electrons single bond . Sharing 4 electrons double bond . Sharing 6 electrons triple bond 2 types of covalent bonds: 1. Polar 2. Nonpolar . Polar covalent bonds: unequal sharing of electrons between two atoms because atoms have different electron attracting abilities leading to unequal sharing such as water (Fig. 2.8a) . Nonpolar covalent bonds: equal sharing of electrons between atoms, electrically balanced such as carbon dioxide (Fig. 2.8b) .Note: atoms with higher electron attracting ability are electronegative and those with less are electropositive Hydrogen bonds: (Fig. 2.10a, and b) Attractive forces between electropositive hydrogens of one molecule and an electronegative atom of another molecule Common between dipoles (compounds/ molecules with two different charges) such as water Acts as intramolecular bonds, holding a large molecule in a 3D shape The high surface tension of water is a result of the combined strength of its H bonds . Chemical equations: Chemical reactions occur when chemical bonds are broken, formed, and rearranged Chemical reactions can be written in symbolic forms called chemical equations Chemical equations contain: 1. Reactants/ reagents 2. Products Compounds are represented as molecular formulas In chemical reactions, subscripts indicate how many atoms are joined by bonds, whereas prefix means # of not joined atoms .3 main types of chemical reactions: 1. Synthesis reactions: atoms/ molecules combining to form larger molecules (Fig. 2.11a) Used in anabolic processes A+ B AB 2. Decomposition reactions: breakdown of a molecule into smaller molecules (Fig. 2.11b) Used in catabolic processes such as the conversion of glycogen to glucose ABA+B 3. Exchange reactions: (Aka displacement reactions) involve both synthesis and decomposition reactions (Fig. 2.11c) Bonds are broken and formed AB+CDAD+CB Example: acid+ base water +salt . In living systems, reduction-oxidation or redox reactions are critical, atoms are reduced when they gain an electron and oxidized when they lose an electron Ex. Glucose+ oxygen carbon dioxide+ water+ ATP Oxygen is reduced and glucose is oxidized . All chemical rxns are either exergonic or endergonic: 1. Exergonic: net release of energy, products have less potential energy than reactants Example: catabolic and oxidative rxns 2. Endergonic: net absorption of energy, products have more potential energy than reactants Example: anabolic rxns . All chemical rxns are reversible: A+ B ↔AB Chemical equilibrium occurs if neither a forward nor a reverse rxn is dominant . Many biological rxns are not very reversible because energy requirements to go backward are too high or products have been removed . The rate of chemical rxns can be affected by: 1. Temperature: ↑ temperature means ↑ rate of rxns ↑ 2. Concentration of rxns: concentration means ↑ rate rxns 3. Particle size: smaller particles, ↑ rate of rxns 4. Catalysts/ enzymes: increase the rate of rxns without being consumed or altered . Biochemistry: the study of chemical composition and reactions of living matter . All chemicals are either organic or inorganic: 1. Inorganic compounds: water, salts, acids, and bases (don’t contain chains of C) 2. Organic compounds: carbs, proteins, fats, and nucleic acids (contain chains of C, covalently bonded) . Inorganic compounds: Water is the most abundance inorganic compound composing 60- 80% of the volume of living cells Water is important due to its properties: 1. High heat capacity 2. High heat of vaporization 3. Polar solvent properties: dissolves and disassociates ionic substances and it’s body’s major transport medium 4. Reactivity: needed for hydrolysis and dehydration 5. Cushioning: protects organs from physical trauma Salts: ionic compounds that disassociate into separate ions in water Acids and bases are electrolytes that disassociate and ionize in water Acids: proton donors o Release H ions o Important acids: HCl, carbonic acid, and acetic acid Bases: proton acceptors o Pick up H ions o When a bases dissolves it releases a hydroxyl ion (OH) o Important bases: bicarbonate ion and ammonia pH scale: measurement of concentration of H ions in a solution (Fig. 2.13) high H ions results in low pH pH is – log of H ions in moles/liter that ranges from 0-14 pH scale is logarithmic, so each pH unit represents a 10 fold difference Acidic (0-6.99), basic (7.01-14) . Neutralization rxn: acids and bases are mixed ttogether NOTE: Acidity involves only free H ions in a solution, not H ions bound to anions . Buffers: resist abrupt and large swings in pH Release H ions if pH increases (becomes basic) Bind H ions if pH decreases (becomes acidic) Convert strong acids or bases into weak ones . Organic compounds: Contain chains of C except CO2 and CO which are inorganic Carbon is electroneutral : o Shares electrons o Forms 4 covalent bonds Major organic compounds: 1. Carbohydrates 2. Lipids 3. Proteins 4. Nucleic acids Synthesized by dehydration synthesis and broken down by hydrolysis rxns (Fig. 2.14) Carbs: o Sugars and starches that contain C, H, and O o 3 classes: 1. Monosaccharides: single sugars (monomers: smallest unit of carb) 2. Disaccharides: 2 sugars 3. Polysaccharides: 3 sugars o Monosaccharides: (Fig. 2.15a) Simple sugars containing 3-7 C atoms General formula (CH2O) Important monosaccharides: Pentose sugars: Ribose and deoxyribose Hexose sugars: Glucose, fructose, and galactose o Disaccharides: (Fig. 2.15b) Double sugars that are too large to pass the cell membrane Formed by dehydration synthesis of 2 monosaccharides Important disaccharides: Sucrose: glucose+ fructose (table sugar) Lactose: glucose+ galactose (milk sugar) Maltose: glucose+ glucose (grain sugar) o Polysaccharides: (Fig. 2.15c) Polymers of monosaccharides that are not very soluble Important polysaccharides: Starch (in plants) Glycogen (in animals) Lipids: Contain C,H,O, and sometimes P Hydrophobic Main types: 1. Triglycerides/ neutral fats 2. Phospholipids 3. Steroids 4. Eicosanoids o Triglycerides: Called fats when solid and oils when liquid Composed of 3 fatty acids bonded to a glycerol molecule Used for energy storage, protection, and insulation Can be constructed of: Saturated fats: Solid at room temp. All Carbons linked via single covalent bonds Molecules with the highest # of H atoms Ex. Animal fats, butter Unsaturated fats: Liquid at room temp One or more carbons are linked via double bonds resulting in low # of H atoms Ex. Olive oil Trans fat: modified oils (unhealthy) Omega-3 fats: heart healthy o Phospholipids: (Fig. 2.16b) Modified triglycerides Glycerol and 2 fatty acids+ a phosphorous containing group Heads are polar and tails are nonpolar Important in cell membrane structures o Steroids: (Fig. 2.16c) 4 interlocking ring structures Common steroids are cholesterol, vitamin D, bile salts, and steroid hormones Cholesterol is the most important: Steroid synthesis Bile salts synthesis Building block of vitamin D Hormones such as estrogen and testosterone Required for cell plasma membrane structure o Eicosanoids: Derived from a fatty acid (arachidonic acid) Most important eicosanoids are Prostaglandins because they play a role in blood clotting, inflammation, labor contractions, and control of blood pressure Prostaglandins have 2 derivatives: Prostacyclins Thromboxanes Proteins: Comprise 20-30% of cell mass Contain C, H, O, N, and sometimes S and P Polymers of amino acid monomers are held together by peptide bonds Have most varied functions of any molecules (structural, chemical, contraction) Shape and function due to four structural levels All proteins made up of 20 types of amino acids Proteins contain an amine group and acid group (Fig. 2.2) Can act as either base or acid . 4 structural levels of proteins: (Fig. 2.18a, b, c, d) 1. Primary: linear sequence of amino acids 2. Secondary: how primary amino acids interact with each other Alpha helix coils resemble a spring Beta pleated sheets resemble accordion ribbons 3. Tertiary : how secondary structures interact 4. Quaternary: how 2 or more different polypeptides interact with each other . Shapes of proteins fall into 2 categories: 1. Fibrous (structural) proteins: Strand like, water insoluble, and stable Most have tertiary or quaternary structure Provide mechanical support Ex. Keratin. Elastin. Collagen, and certain contractile fibers 2. Globular (functional) proteins: Water soluble, compact, spherical, and sensitive Specific functional regions such as active sites Tertiary or quaternary structure Ex. Antibodies, hormones, molecular chaperones, and enzymes . Denaturation: globular proteins unfold and lose their functional 3D shape Active sites become deactivated Can be caused by low pH or high temp. Reversible if normal conditions restored Irreversible if changes are extreme . Enzymes: globular proteins that act as biological catalysts Speed up reactions and decrease activation energy needed to start a reaction Act on specific substrates Name usually ends in –ase . 3 steps in enzyme action: (Fig. 2.20) 1. Substrate binds to enzyme’s active site. Forming enzyme-substrate complex 2. Complex undergoes rearrangement of substrate resulting in final product 3. Product is released from enzyme Nucleic acids: Composed of C, H, O, N, and P Largest molecules in the body Made of monomers called nucleotides (composed of a nitrogenous bases, a pentose sugar, and a phosphate group) 2 major groups: 1. Deoxyribonucleic acid (DNA) 2. Ribonucleic acid (RNA) DNA holds the genetic info for the synthesis of all proteins (Fig. 2.21) Nitrogenous bases: 1. Purines: Guanine (G) and Adenine (A) 2. Pyrimidines: Thymine (T) and Cytosine (C) Complementary base pairing rules: A-T G-C RNA: links DNA to protein synthesis and is single stranded Contains a ribose sugar Active mostly outside the nucleus Thymine (T) is replaced with Uracil (U) 3 types of RNA: 1. mRNA 2. tRNA 3. rRNA They all carry out the DNA orders for protein synthesis ATP: chemical energy released when glucose is broken down that directly powers chemical rxns in cells (Fig. 2.22) Adenine containing RNA nucleotide with 22 additional phosphate groups transports proteins, phosphorylates contractile proteins, and drives chemical rxns (Fig. 2.23) loss of one phosphate group ADP loss of 2 phosphate groups AMP . Cell theory: Cell: the structural and functional unit of life How well the entire organism functions depends on individual and combined activities of all of its cells Biochemical functions of cells are directed by shape of cell and specific subcellular structures Continuity of life has cellular basis Cells differ in shape, size, and subcellular components which lead to different functions (Fig. 3.1) Erythrocytes (RBCs), epithelial, and fibroblasts connect body parts or transport gases Macrophages fight disease and skeletal muscle cells and smooth muscle cells move organs All cells have some common structures and functions . Human cells have 3 basic parts: 1. Plasma membrane: flexible outer boundary 2. Nucleus: contains DNA 3. Cytoplasm: intracellular fluid containing organelles . Extracellular materials: substances found outside cells 1. Extracellular fluids: Interstitial fluid: cells are bathed in this fluid Blood plasma: fluid of the blood Cerebrospinal fluid: fluid surrounding nervous system organs 2. Cellular secretions such as mucus and saliva 3. Extracellular matrix: substance that acts as a glue to hold cells together in tissues . Plasma membrane (cell membrane): (Fig. 3.3) Acts as an active barrier separating intracellular fluid (ICF) from extracellular fluid (ECF) Controls what enters and what leaves the cell Consists of a flexible lipid bilayer that have membrane proteins which results in changing patterns referred to as fluid mosaic pattern Surface sugars form Glycocalyx Membrane structures help to hold cells together through cell junctions Lipid bilayer is made of: 75% phospholipids, which consist of 2 parts: 1. Phosphate heads (hydrophilic and polar) 2. Fatty acid tails (hydrophobic and nonpolar) 5% glycolipids . Lipids with sugar groups on outer membrane surface 20% cholesterol . Increases viscosity and stability of the membrane Membrane proteins: . Allow cell communication with environment . Makeup about half the mass of plasma membrane . Most have specialized membrane functions . Some float freely and some are connected to intracellular structures . 2 types of proteins: (Fig. 3.4) 1. Integral 2. Peripheral . Integral proteins: o Inserted into membrane o Most are transmembrane proteins (span membrane) o Have hydrophobic and hydrophilic regions o Function as transport proteins (channels), enzymes, or receptors . Peripheral proteins: o Not embedded in the lipid bilayer o Loosely attached to integral proteins o Function as enzymes, cell to cell connections, and motor proteins for shape change during cell division and muscle contraction Glycocalyx: Consists of sugars sticking out of cell surface Every cell has different patterns of this sugar coating Some sugars attached to lipids glycolipids Some sugars attached to proteins glycoproteins Functions as specific markers for cell to cell recognition Allow the immune system to recognize itself vs. non-self cells Glycocalyx of some cancer cells change rapidly that the immune system can’t recognize the cell as being damaged . Cell junctions: Some cells such as sperm and erythrocytes (RBCs) are not bound to any other cells Most cells are bound to form tissues and organs 3 types of junctions: 1. Tight junctions 2. Desmosomes 3. Gap junctions Tight junctions: (Fig. 3.5a) o Prevent fluids and most molecules from moving in between cells o Integral proteins on adjacent cells fuse to form an impermeable junction that encircles the whole cell o Useful to prevent leakage such as the digestive track and the urinary bladder Desmosomes: (Fig. 3.5b) o Linker proteins of neighboring cells interlock like the teeth of a zipper o Linker protein is anchored to its cell through thickened areas on inside of plasma membrane called plaques o Keratin filaments connect plaques intracellularly for added anchoring strength o Useful to counteract mechanical stress such as skeletal muscles and the cardiac muscle Gap junctions: (Fig. 3.5c) o Transmembrane proteins form tunnels that allow small molecules to pass from cell to cell o Used to spread ions, sugars, or other molecules o Allow electrical signals to be passed quickly from one cell to the next cell o Used in cardiac and smooth muscle cells . Plasma membranes are selectively permeable: 2 ways which substances can cross membrane: 1. Passive processes (no ATP required) 2. Active processes (ATP required) Passive transport: 2 types: 1. Diffusion: 1. Simple diffusion 2. Osmosis 3. Carrier and channel mediated facilitated diffusion 2. Filtration: usually occurs across capillary walls . Diffusion: going from high concentration to low concentration (Fig. 3.6) Difference is called concentration gradient Rate of diffusion is influenced by size of molecule and temp. Molecules have natural drive to diffuse down concentration gradients that exist between extracellular and intracellular areas Plasma membranes stop diffusion and create concentration gradients by acting as permeable membranes If plasma membrane is damaged, substances diffuse freely into and out of cells, compromising concentration gradients Molecules that passively diffuse through membrane include: 1. Lipid soluble and nonpolar substances 2. Very small molecules 3. Large molecules assisted by carrier molecules Facilitated diffusion: certain hydrophobic molecules are transported down their concentration gradient by: 1. Carrier mediated facilitated diffusion: substances bind to proteins 2. Channel mediated facilitated diffusion: substances move through water filled channels Carrier mediated facilitated diffusion: (Fig. 3.7b) Carriers are transmembrane integral proteins Carriers transport specific polar molecules such as sugars and amino acids that are too large for membrane channels . Ex. Glucose molecules by glucose carriers Binding of molecule causes carrier to change shape, moving molecules in process Binding is limited by the number of carriers present Carriers are saturated when all are bound to molecules and are busy transporting Channel mediated facilitated diffusion: (Fig. 3.7c) Channels with aqueous filled cores are formed by transmembrane proteins Channels transport molecules such as ions or water (osmosis) down their concentration gradient . Specificity based on pore size or charge . Water channels are called aquaporins 2 types: 1. Leakage channels: always open 2. Gated channels: controlled by chemical/ electrical signals . Osmosis: movement of solvent across a selectively permeable membrane (Fig. 3.7d) Water diffuses through plasma membranes: 1. Though the lipid bilayer 2. Through specific water channels called aquaporins (AQPs) . Osmolarity: measure of total concentration of solute particles . Water concentration varies with the number of solute particles because solute particles displace water molecules When solute concentration increases, water concentration decreases and vice versa . Water moves from low solute concentration (high water conc.) to high solute concentration (low water conc.) . Equilibrium: same concentration of solutes and water on both sides with equal volume on both sides When solutions of different osmolarity are separated by a membrane permeable to all molecules, both solutes and water cross membrane until equilibrium is reached. (Fig. 3.8a) When solutions of different osmolarity are separated by a membrane that’s permeable only to water, osmosis will occur (Fig. 3.8b) Same concentration of solutes and water on both sides with unequal volume . Movement of water causes pressures: 1. Hydrostatic pressure: pressure of water inside cell pushing on membrane 2. Osmotic pressure: tendency of water to move into cell by osmosis o High conc. of solutes in the cell leads to high osmotic pressure . Tonicity: ability of a solution to change the shape or tone of cells by altering the cells’ internal water volume (Fig. 3.9) 1. Isotonic solution: same osmolarity on both sides, volume remains unchanged . used to increase blood volume 2. Hypertonic solution: high osmolarity than inside of cell so water flows out of cell resulting in cell shrinking (crenation) . given to ed ematous (swollen) patients to pull water back into the blood 3. Hypotonic solution: low osmolarity than inside of cell so water flows into cell resulting in cell swelling which can lead to lysing (bursting) . given to patients who are experience dehydration such as diabetic ketoacidosis and hyperosmolar hyperglycemic state . Active processes: 1. Active transport 2. Vesicular transport . Both require ATP to move solutes across a plasma membrane because: 1. Solute is too large for channels 2. Solute is not lipid soluble 3. Solute is moving across its concentration gradient . Active transport: Requires carrier proteins (solute pumps) . Bind specifically and reversibly with substance being moved . Some carriers transport more than one substance: 1. Antiporters: one substance into cell while transporting one substance out of cell 2. Symporters: 2 different substances moved in the same direction Moves solutes against their concentration gradient (low to high) 2 types: 1. Primary active transport: requires energy directly from ATP hydrolysis 2. Secondary active transport: required energy is obtained indirectly form ionic gradients created by primary active transport o Primary active transport: (Fig. 3.1) . energy from the hydrolysis of ATP causes change in shape of transport protein . shape change causes solutes (ions) bound to protein to be pumped across membrane . Ex. of pumps: Ca, H (proton). Na-K pumps . Na-K pump is the an antiporter pump that pumps Na out of cell and K back into cell using the Na-K ATPase enzyme . Present in all plasma membranes especially active in nerve and muscle cells . Na and K move down their concentration gradient . Maintains electrochemical gradients which involve both concentration and electrical charge of ions o Secondary active transport: (Fig. 3.10) . depends on ion gradient that was created by primary active transport system Energy stored in gradients is used indirectly to drive transport of other solutes Low Na concentration is maintained inside of cell by Na-K pump which strengthens Na’s inward movement through diffusion Na can drag other molecules with it as it flows into cell through carrier proteins (usually symporters) in the membrane Some sugars, amino acids, and ions are transported into cell via secondary active transport . Vesicular transport: Involves transport of large particles, macromolecules, and fluids across membrane in membranous sacs called vesicles Requires ATP and includes endocytosis and exocytosis: 1. Endocytosis: transport into cell . 3 types of endocytosis: 1. Phagocytosis (cell eating) 2. Pinocytosis (cell drinking) 3. Cell-mediated endocytosis 2. Exocytosis: transport out of cell Transcytosis: transport into, across, and then out of cell Vesicular trafficking: transport from one area or organelle in cell to another Endocytosis: (Fig. 3.11) . involves formation of protein coated vesicles . it is a very selective process b/c substances being pulled in must be able to bind to its unique receptor . some pathogens are capable of hijacking receptors in order to enter the cell . once vesicle is pulled inside cell, it may: 1. Fuse with lysosome 2. Undergo transcytosis o Phagocytosis: . membrane projections called pseudopods form and flow around solid particles that are being engulfed . formed vesicle is called a phagosome . used by macrophages and WBCs . phagocytic cells move by amoeboid motion where cytoplasm flows into temporarily extensions that allow cell to creep (Fig. 3.12a) o Pinocytosis: (Fig. 3.12b) . plasma membrane enfolds, bringing extracellular fluid and dissolved solutes inside cell (fuses with endosome) . routine and nonselective . main way of nutrient absorption . membrane components are recycled back to the membrane o Cell-mediated endocytosis: (Fig. 3.12c) . involves endocytosis ns transcytosis of specific molecules . many cells have receptors embedded in clathrin-coated pits which will be internalized along with the specific molecule bound Ex. enzymes, LDLs, iron, and insulin . Toxins may be taken into a cell this way . Caveolae: similar pits and different protein coat from clathrin, but still capture s specific molecules and use transcytosis (Ex. folic acid) Exocytosis: (Fig. 3.13a) . material ejected from the cell . activated by cell surface signals or changes in membrane voltage . substances are ejected in enclosed secretory vesicles . Protein on vesicle called v-SNARE finds and hooks up to target t- SNARE proteins on the membrane . some subs. exocytosed: hormones, neurotransmitters, mucus, cellular waste . Resting membrane potential (RMP): Electrical potential energy produced by separation of oppositely charged particles across plasma membrane in all cells . difference in electrical charge between 2 points is called voltage Voltage occurs only at membrane surfaces . rest of cell and extracellular fluid are neutral . membrane voltages range from -50 to -100 mV (inside of cell is more – relative to outside of cell) . NOTE: potassium ion is the key player in RMP (Fig. 3.14) . K diffuses out of cell through K leakage channels down its conc. gradient . negatively charged proteins can’t leave as a result so cytoplasmic side of cell membrane becomes more negative . K is then pulled back by the more – interior b/c of its electrical gradient . when the drive for K to leave the cell is balanced by its drive to stay, RMP is established . most cells have an RMP around -90 mV . electrochemical gradient of K sets RMP . Na also affects RMP b/c Na is attracted to inside of the cell due to negative charge . if Na enters the cell. It can bring up RMP to -70 mV . membrane is more permeable to K than Na so K is the primary influence on RMP . Cl doesn’t influence RMP b/c its conc. and electrical gradients are balanced . RMP is maintained through action of the Na-K pump which ejects 3 Na out of the cell and brings 2 K back inside . rate of active pumping of Na out of the cell = the rate of Na diffusion into the cell And that’s how steady state is maintained . neuron and muscle cells upset this steady state RMP by intentionally opening gated Na and K channels . Cells interact with their environment by responding directly to other cells or indirectly to extracellular chemicals . Cell interactions always involve glycocalyx Cell adhesion molecules (CAMs) Plasma membrane receptors Works Cited Lindsey, Jerri K., Katja Hoehn, and Elaine Nicpon Marieb. Human Anatomy & Physiology, 9th Edition Elaine N. Marieb, Katja Hoehn. Boston, MA: Pearson, 2013. Print.
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