NATS1610 PDF - Human Biology

Humans are dependent on their external environment to OBTAIN the requirements of life Bodies are designed to OBTAIN & USE nutrients and energy from their environment (and the organisms living there) The body;s Design EMERGES during Embryonic & Fetal Development BODIES are a COLLECTION OF ATOMS that...

Humans are dependent on their external environment to OBTAIN the requirements of life Bodies are designed to OBTAIN & USE nutrients and energy from their environment (and the organisms living there) The body;s Design EMERGES during Embryonic & Fetal Development BODIES are a COLLECTION OF ATOMS that are HELD TOGETHER by chemical bonds? BODIES ARE HIGHLY ORGANIZED - Because they are constructed from ATOMS - Atoms interact to FORM MOLECULES - Very precise interactions - Thus, molecules have very precise structures - The PRECISE MOLECULAR STRUCTURE is the “foundation” for organizing a 3-Dimensional body Atoms are HELD TOGETHER by CHEMICAL BONDS For example: Atoms form MOLECULES Molecules interact to form CELLULAR STRUCTURES AND CELLS Cells interact to form BODY PARTS Novel properties EMERGE when molecules and structures interact - Emergent Properties - Arise due to the arrangement and interactions of parts - The ‘power’ of organization - Example - Capillaries transport blood - Property NOT exhibited by individual endothelial cells that form capillaries The body's structures and functions ‘emerge’ DURING EMBRYONIC DEVELOPMENT WHY Do Bodies Need FOOD? 1. Food provides RAW MATERIALS - The ATOMS & MOLECULES During embryonic development - To FORM cells (and body) After birth - ADDED to new cells and body during GROWTH - REPLENISH previously existing molecules that were lost, used up, or destroyed 2. Food also provides ENERGY (to maintain chemical bonds) - Within CHEMICAL BONDS (holding atoms together) To MAINTAIN the molecular structures of cells - To prevent chemical bonds from the breaking apart To DRIVE cellular metabolism Digestive system is breaking food down into smallest components and transferring them into our blood system then body removes from circulatory and builds our body The human body is HIGHLY ORGANIZED and is DESIGNED to ACQUIRE & USE energy and raw materials Energy is needed to maintain the body’s hierarchy of organization Energy & Raw Materials come from The ENVIRONMENT The MAIN SOURCE of Energy on Earth is SUNLIGHT ENERGY - Energy FLOWS through an ecosystem - In ONE direction - Nutrients CYCLE (parts that make up the producers body) - From environment - to organisms - Eventually back to environment Organisms OBTAIN energy by extracting it from the environment - Producers: get energy from nonliving sources - perform photosynthesis - plants, some bacteria, algae - make their own food - Consumers: get nutrients made by other organisms - must eat other life forms - Decomposers: (are consumers) “absorbs” nutrients from dead organisms - fungi and bacteria (brings back nutrients into the soil) In all energy transformations - Some energy is LOST to the surroundings as heat - thus energy flows in ONE direction How do Bodies RECEIVe Oxygen & energy & Nutrients? The adult is FULLY FORMED, with functioning structures that really obtain these materials But the developing body IS INCOMPLETE and relies on the placenta and diffusion across cell membranes IN ADULTS: DELIVERY of Oxygen, Nutrients, Energy (etc) - NUTRIENTS AND ENERGY obtained from food - via DIGESTIVE system - WATER by drinking - via the DIGESTIVE system - OXYGEN by breathing - via the RESPIRATORY system - Nutrients (etc) and water DELIVERED throughout body via the CIRCULATORY system Respiratory System The Trachea extends from the throat area (larynx & pharynx) towards the lungs - and splits into the two main Bronchi. One of these extends into right lung & the other into left lung The Alveoli are air sacs (atrium) formed by the branching bronchi. The inner alveolar space contains inhaled & exhaled air. The surface of each alveolus is covered with tiny blood vessels. Oxygens from the atrium of each alveolus diffuses into the blood. Carbon Dioxide diffuses from the blood into each alveolus. A Digestive “Tube” Salivary glands -> esophagus -> stomach -> liver & gallbladder or pancreas -> small intestine -> large intestine -> colon Circulatory System Blood picks up Oxygen as it flows through the Lungs. As the blood flows through the body, it releases the Oxygen and picks up Carbon Dioxide on it’s way back to the lungs The Heart pumps the blood to the lungs & through the body What happens in the “UNFORMED” body during early embryonic development when body structures haven’t yet formed?? DURING DEVELOPMENT: The Body is INCOMPLETE. So, HOW are Oxygen and Nutrients DELIVERED? 1. VERY EARLY EMBRYOS are just ‘clumps’ of cells - therefore, these cells: - Obtain nutrients, water, and oxygen FROM the maternal (female) reproductive tract - Through DIFFUSION across cell membranes 2. BUT OLDER EMBRYOS have PARTIALLY DEVELOPED BODIES - they have the: - Fetal portion of the PLACENTA, a HEART, and a CIRCULATORY SYSTEM (blood and blood vessels) - Therefore, nutrients and oxygen - DIFFUSE FROM the maternal side of placenta INTO the FETAL CIRCULATORY SYSTEM - The fetal circulatory system THEN DELIVERS these materials throughout the developing body Developing digestive and respiratory systems begin to fully function AFTER BIRTH Two Mechanisms of Diffusion Across ALL Cell Membranes (able to pass from one side of the membrane to another) Simple Diffusion - pass directly across the membrane Facilitated Diffusion - proteins amino acids (not soluble) food bits that are too big to get across the membrane so they need help Diffusion from maternal portion of placenta INTO the FETAL CIRCULATORY SYSTEM (blood cells do NOT cross) Summary - To live, our bodies need a variety of substances with which they can build and maintain themselves - the Requirements of Life (to keep the body from falling apart) - These substances (raw material etc) are brought into the body from the external environment - The body is designed to acquire and utilize these materials - This body design EMERGES during embryonic development Lecture 3 - The Organization of the Human Body Structural & Functional Organization Definitions - Anatomy - The science of STRUCTURE and the RELATIONSHIPS among structures - Physiology - The science of BODY FUNCTIONS - How structures enable function - Individual structures or structures interacting with other structures - Histology - The science of the MICROSCOPIC STRUCTURE of biological material - Looking at cellular organizations - See the ways in which individual cellular components are structurally and functionally related LEVELS of Body Organization 1. Chemical Level - Subatomic particles - electrons, protons, neutrons - Atoms - hydrogen atom, oxygen atom, carbon atom, etc - Molecules - water molecule, glucose molecule, etc - Macromolecules - protein molecule, DNA, glycogen, etc Energy is required to maintain chemical bonds between atoms 2. Cellular Level - CELLS - are the basic STRUCTURAL & FUNCTIONAL UNITS of an organism - SMALLEST UNITS OF LIFE - muscle cells, cardiac cells, nerve cells, etc - Organelles - are structural components with specific functions WITHIN cells - I.e mitochondria (energy production), ribosomes (protein synthesis), etc Why are Cells the “smallest units of life”? - Because they perform the SAME FUNCTIONS that whole living organisms do Cells… - OBTAIN nutrients & oxygen from surrounding environment - PERFORM chemical reaction that provide energy for the cell (metabolism) - ELIMINATE carbon dioxide & other wastes to surrounding environment - SYNTHESIZE needed cellular components - CONTROL EXCHANGE of materials between cell & its surrounding environment - SENSE & RESPOND to changes in surrounding environment - REPRODUCE - create new cells to enable body development - and would healing Parts of a Typical Human Cell - Nucleus - houses and protects DNA, the cell’s genetic material - Ribosomes - sites of protein synthesis - Endoplasmic Reticulum - modifies newly made proteins - Golgi Body - processes proteins and lipids - Lysosome - breaks down and recycles materials - Plasma Membrane - controls substances moving into and out of cell - Centrioles - centers that produce microtubules - Mitochondria - produce high energy molecules for metabolism - Cytoskeleton - support and cell movement (microtubules, microfilaments, intermediate filaments) Cells Interact to Form Tissues Epithelial Tissue Connective Tissue Muscle Tissue Nervous Tissue 3. Tissue Level - Groups of cells & the material surrounding them = TISSUES - Work TOGETHER to perform a particular function - 4 TYPES of TISSUE - epithelial, connective, muscular, nervous  - EPITHELIAL TISSUES - Cells TIGHTLY ATTACHED to one another - Little room for other structures - No blood vessels - e.g. skin, inner lining of intestines and blood vessels etc. - Outer surface EXPOSED to body cavity or external environment (lumen) - Inner surface ATTACHED to basement membrane - Whole epithelium is SUPPORTED by connective tissue - Two Forms: - Simple - single layers of cells - Stratified - multiple layers of cells - CONNECTIVE TISSUES - connect , support and anchor various body parts - TWO structural components - Cells - that are dispersed WITHIN an “extracellular” matrix - Matrix Contains - Three Types of Protein Fibers - collagen, elastin, reticular - Ground Substance SUPPORTS the fibers (often jelly-like) - Two Categories of Connective Tissues - Fibrous Connective Tissues - lots of collagen fibres - Loose fibrous (areolar), dense regular, dense irregular fibrous - Specializes Connective Tissues - five types, with unique appearances - Adipose, reticular, cartilage, bone, blood - MUSCLE TISSUES - Specialized for contraction and generating force - Three Types - SKELETAL muscle - moves the skeleton, striated (striped) - CARDIAC muscle - pumps blood out of the heart, striated (striped) - SMOOTH muscle - encloses and controls movement of contents through hollow tubes and organs - i.e. blood vessels, intestines etc. not striated (not striped) - NERVOUS TISSUES - Found in brain, spinal cord and nerves - Consists of NEURONS - cells specialized for initiating & transmitting nerve impulses - EXCITABLE CELLS that form communication lines in nervous system - Neuron = consists of: (1) cell body, (2) dendrites (shorter), (3) axon (long) - Also consists of NEUROGLIA - a VARIETY OF CELLS that PROTECT & SUPPORT neurons structurally & metabolically 4. Organ Level - 2 or more kinds of TISSUES JOINED TOGETHER to form body structures (organs) - Work cooperatively - Have specific functions 5. Organ System Level  - Consists of RELATED ORGANS that have a COMMON FUNCTION - Work cooperatively 6. Organismal Level - Highest level of organization - ALL SYSTEMS OF BODY combine to make up an organism, that is, one human being - Work cooperatively Summary - Where do you see EMERGENT PROPERTIES in this figure? Lecture 4 - The Physiology of the Human Body Survival & homeostasis The Human Body Depends on a STABLE Internal Environment When ALL LIFE’S REQUIREMENTS are AVAILABLE (nutrients, energy, water, oxygen, right temperatures etc) - The body is LIVING (it’s growing, functioning - and it's healthy) - But what happens when a component stops being available? For example - What does the body do when it doesn’t have enough to eat? - The body adjusts by SLOWING DOWN its metabolism - Therefore, it uses fewer calories - Which CONSERVES the limited amount of energy that’s available in the inadequate diet - The RESULT of this metabolic slowdown? - The body SURVIVES - without needing to tap into its stored energy reserves - I.e. slowing the metabolism uses fewer resource - and thus DOES NOT deplete its energy reserves - THEN - when food AGAIN becomes available  - The body adjusts by INCREASING its metabolism BOTTOM LINE - THE BODY WANTS TO STAY ALIVE - and it has EVOLVED a variety of mechanisms that HELPS IT TO SURVIVE - Collectively, these are referred to as - HOMEOSTASIS HOMEOSTASIS - REGULATES the body’s internal environment to REMAIN AT STEADY STATE (stable) - DESPITE changes occurring inside/outside the body - HOMEOSTATIC MECHANISMS - Monitor aspects of the internal environment - Like temperature, or blood pressure - Correct/Adjust fluctuations in the internal environment (to maintain steady state) - CONTROLLED mainly by the nervous & endocrine systems - Nerve impulses, hormones - DISRUPTED by stressors - Disturbance in homeostasis results in disease (and, if severe, may lead to death) Changes over time of a body’s core temperature The Body’s “INTERNAL ENVIRONMENT” consists of CELLS bathed in a pool of EXTRACELLULAR FLUID - EXTRACELLULAR FLUID (ECF) - Fluid OUTSIDE of cells - This is the environment in which the cells live - 2 components - Plasma & Interstitial Fluid - INTRACELLULAR FLUID (ICF) - Fluid INSIDE of cells - During ‘living’ - EXCHANGES occur between ECF and ICF (the foundation of cell metabolism and metabolic reactions) - From cells to interstitial fluid - From interstitial fluid to cells - From interstitial fluid to plasm - From cells to interstitial fluid to plasma - From plasma to interstitial fluid to cells Homeostasis, Cells and Body Systems are INTERCONNECTED - CELLS MAKE UP body systems - BODY SYSTEMS MAINTAIN homeostasis (this is where cellular metabolism is occurring) - HOMEOSTASIS ENABLES cells to survive - RESULT: Healthy Cells = Healthy Body = Healthy Cells = Healthy Body, and So on… The Body & its Cells - FUNCTION PROPERLY ONLY WITHIN NARROW RANGES of temperature & chemistry - Homeostasis MAINTAINS the narrow ranges of these conditions - Some Conditions that are Homeostatically Regulated Include: - Concentration of nutrient molecules, such as glucose - Concentration of O2 and CO2  - Concentration of waste products - pH (acid levels) - Concentration of water, salt and other electrolytes - Volume and pressure, such as blood pressure - Temperature HOMEOSTATIC CONTROL MECHANISMS Consists of 3 PARTS 1. SENSOR or RECEPTOR - Monitors/Detects changes in a controlled condition - Responds to change in system - Sends INPUT information - nerve impulses, chemical signals (hormones) 2. CONTROL CENTRE (REGULATORY CENTRE, INTEGRATOR) - Receives information from the sensor - Evaluates input signal from receptors AGAINST a set point - Determines appropriate response - if any - Generates OUTPUT signal to initiate a response to maintain homeostasis 3. EFFECTOR - Body structure that receives OUTPUT signal from the control centre - Produces a response (EFFECT) that changes the controlled condition TWO TYPES of homeostatic control mechanisms 1. NEGATIVE FEEDBACK LOOP - Prevents sudden, severe changes in the body - Reverses a change - most systems in body are negative - SHUTS OFF original stimulus - or REDUCES its intensity - Works like household thermostat - Examples: body temperature, blood pressure & glucose regulation 2. POSITIVE FEEDBACK LOOP - Short-lived - Reinforces a change - INCREASES (accelerates, amplifies) the original stimulus to push the variable farther - Examples: blood clotting, contractions during childbirth NEGATIVE FEEDBACK - Maintenance of Body Temperature NEGATIVE FEEDBACK - TESTOSTERONE and SPERM PRODUCTION - LOW TESTOSTERONE & SPERM COUNT - TRIGGER the hypothalamus (in brain) to release gonadotropin-releasing hormone (GnRH) - GnRH stimulates the anterior pituitary gland to secrete 2 hormones - Luteinizing hormone (LH) - Follicle stimulating hormone (FSH) - LH stimulates production of testosterone - By the interstitial cells of the testes - FSH (with testosterone) stimulate - Sperm formation by testes - RISING testosterone & sperm levels INHIBIT the production of GnRH, LH, FSH - Testosterone & sperm production STOP POSITIVE FEEDBACK Feedforward Regulation  - Primes the system for challenges “TO COME” (anticipatory situations - in future) - I.e. Smell food – stomach churns, salivate, digestive enzymes start increasing Lecture 5 - The Organization of the Human Body Body Systems and Anatomy The Organ System: Groups of organs that perform related functions & interact - to accomplish a common activity - That’s essential to survival of the whole body - Circulatory: rapidly transports many materials to and from interstitial fluid and cells; helps stabilize internal pH and temperature - Digestive: ingests food and water; mechanically, chemically breaks down food and absorbs small molecules into internal environment; eliminates food residues - Respiratory: rapidly delivers oxygen to the tissue fluid that bathes all living cells; removes carbon dioxide wastes of cells; helps regulate pH - Urinary; maintains the volume and composition of internal environment; excretes excess fluid and bloodborne wastes - Skeletal: supports and protects body parts; provides muscle attachment sites; produces red blood cells; stores calcium, phosphorus - Muscular: moves body and its internal parts; maintains posture; generates heat by increases in metabolic activity - Integumentary: protects body from injury, dehydration, and pathogens; controls its temperature; excretes certain wastes; receives some external stimuli - Immune: collects and returns some tissue fluid to the bloodstream; defends the body against infection and tissue damage - Nervous: detects external and internal stimuli; controls and coordinates the responses to stimuli; integrates all organ system activities - Endocrine: hormonally controls body functioning; with nervous system integrates short - and long-term activities - Reproductive: female - produces eggs; provides a protected, nutritive environment for the development of new individuals… male - produces and transfers sperm to the female; hormones of both systems also influence other organ system The organ system COOPERATE with each other Organ Systems WORK TOGETHER to maintain health, protect from disease, & for reproduction Often, if an organ system fails - one or more other systems “kicks in” to help out… - An example of organ system “Co-operation” Abnormality in the Immune (Lymphatic) System causes Autoimmune Hemolytic Anemia - an AUTOIMMUNE DISORDER - Where body makes antibodies to destroy its OWN red blood cells - Causes life-threatening severe anemia - Due to SEVERE cellular oxygen depletion Other body systems “STEP UP” to help save body by attempting to deliver more oxygen to cell & brain - for example: - Respiratory system increases breathing rate  - Bringing oxygen into body more rapidly - Cardiovascular system increases heart rate - Moving oxygen faster through body - Muscular system constricts muscles in blood vessels of extremities (hands/arms, feet/legs) - Localizing blood to internal organs - heart, liver, kidneys, etc Summary of Functions - Circulatory - carries materials from one part of the body to another - Muscular - moves the bones, temperature regulation - Digestive - breaks down food into smaller molecules that can be distributed to body cells; transfers water and electrolytes from external to internal environment; eliminates undigested food to external environment in feces - Respiratory - gets O2 from and eliminates CO2 to the external environment; important in maintaining proper pH in internal environment - Urinary - remove excess water, salt, acid, and other electrolytes from plasma - eliminates them in urine - Skeletal - provides support & protection for soft tissues & organs; serves as storage reservoir for calcium; along with muscular system enables movement of body & its parts; bone marrow is source of all blood cells - Integumentary - outer body protective barrier; helps regulate body temperature - Immune (and Lymphatic) - defends against foreign microorganisms & against cancerous body cells; prepares for cell repair and/or replacement (Lymphatic system regulates fluid volumes) - Nervous - controls & coordinates bodily activities that require rapid responses; detects & initiates reactions to changes in the external environment - Endocrine - secreting endocrine glands regulate activities that require duration rather than speed; controls nutrient concentration; adjust kidney function; controls volume & electrolyte composition in the internal environment - Reproductive - not essential for homeostasis; essential for perpetuating the species ANATOMICAL TERMS - Used to provide PRECISE and UNAMBIGUOUS COMMUNICATION about body structure and parts - Provide CONSISTENCY when referencing anatomical positions - Provide PRECISE DESCRIPTIONS of a structure’s location Standard Anatomical Position - The STANDARD ANATOMICAL POSITION - ALWAYS - The Body is standing erect & facing forward - Upper limbs at sides with palms facing forward - Feet flat on floor - THIS BODY ORIENTATION is used when describing the body’s anatomy - STANDARDIZATION IS REQUIRED TO AVOID CONFUSION because - The body can take many different positions - That may change the relative placement of organs - All descriptions refer to the body in its standard anatomical position - Even when the body is lying down. on its stomach, or upside down DIRECTIONAL TERMS: used to indicate the precise relationship of one body part to another (relative position) - superior/cranial - towards the head, or the upper part of a structure - inferior/caudal - towards the feet, or the lower part of a structure - anterior/ventral - nearer to or at the front of the body - posterior/dorsal - nearer to or at the back of the body - Superficial - toward or on the body surface - Deep - away from surface of body - Internal - inside body of structure - External - outside body of structure - Medial - nearer to the midline - Lateral - farther from body midline - Intermediate - between 2 structures - Proximal - nearer to the attachment of a limb to the trunk - Ipsi-lateral - same side - Contra-lateral - other side BODY PLANES & SECTIONS are imaginary flat surfaces that pass through the body parts - Sagittal (median) - vertical plane dividing body into R&L sides - Midsagittal - when R&L sides are equal in size - Parasagittal - when R&L sides are unequal in size - Frontal (coronal) - divides body or organ into anterior & posterior portions - Transverse (horizontal) - divides the body into superior & inferior portions - Oblique - on an angle Ventral & dorsal is different in 2-legged & 4-legged animals The BODY CAVITIES Fluid-filled space that contains ORGANS The human body is divided into 2 major BODY CAVITIEs 1. The dorsal cavity (aka posterior cavity) - Divided into 2 parts - Cranial cavity - Vertebral canal (spinal cavity) 2. The ventral cavity (aka anterior cavity) - Divided into 2 parts - Thoracic cavity - Abdominopelvic cavity - Abdominal - Pelvic Abdominopelvic cavity - Abdominal cavity - Contains stomach, spleen, liver, gallbladder, small intestine, and most of large intestine - Pelvic cavity  - Contains urinary bladder, portions of large intestine, and female & male reproductive organs The BODY MEMBRANES FOUR major BODY MEMBRANES line body cavities & internal spaces of organs & tubes opening to the outer environment 1. Mucous membranes - Line tissues that open to the exterior of the body - most have glands - Respiratory, digestive, reproductive, urinary - line tubes and cavities - Varied functions - i.e. designed to secrete and/or absorb substances 2. Serous membranes - Line the thoracic and abdominal cavities and the organs within them - Enclose heart and lungs etc - Secrete serous fluid - lubrication 3. Cutaneous membrane (skin) - Forms the protective covering of the body 4. Synovial membranes - Line the cavities of moveable joints - Secretes synovial fluid - lubrication Lecture 6 - The Human Body at the Molecular Level Chemistry Basics: Atoms, Molecules, and Why It’s All about the Electrons Chemistry Underlies the Mechanisms of Physiology (and just about everything else) The Human Body is HIGHLY ORGANIZED because it’s constructed from ATOMS - and atoms INTERACT with each other - Atoms interact to form MOLECULES - Molecules interact to form all the BODY’S STRUCTURE - Atoms interact in very PRECISE ways - Because of their atomic structure EVERYTHING in our world is made of ELEMENTS - including living organisms - Over 90% of human body is composed of FOUR elements - Carbon ~ 18% - Nitrogen ~ 3% - Oxygen ~ 65% - Hydrogen ~ 10% - Each element has its own symbol derived from its name - C for carbon, N for nitrogen, O for oxygen, H for hydrogen - Na for sodium (natrium, Latin) ATOMS are the SMALLEST UNITS that retain all of the properties of a given element ATOMS consist of 2 areas & 3 types of subatomic particles 1. CENTRAL NUCLEUS, containing - Positively-charged protons  - Neutral neutrons 2. ELECTRON “CLOUD” (electron shell), containing - Negatively-charged electrons - Move rapidly around the nucleus - Their precise location can’t be determined - I.e. cloud, rings, orbitals, shells ATOMIC NUMBER of an atom - Number of protons in nucleus (identifies the element) - All atoms of an element have the SAME atomic number - Usually written as a subscript to lower left of atomic symbol ATOMIC MASS of an atom (AM) - Mass of protons plus neutrons (*plus electrons) - Protons & neutrons each = 1 atomic mass unit (amu) - (*Electrons are light & have almost no mass = “0”) - Thus, AM = the NUMBER of protons plus neutrons - Usually written as a subscript to upper left of atomic symbol Atoms are ELECTRICALLY NEUTRAL - Have the SAME number of PROTONS and ELECTRONS - Positive protons must balance negatively charged electrons Electrons & Their Shells (Orbitals, Rings) ELECTRONS ORBIT RAPIDLY around the atom’s nucleus inside various “SHELLS” - Electrons fill the atom’s shells from the inside out - Like water fills a glass, from the bottom up - First shell, closest to nucleus, lowest energy shell - Holds up to 2 electrons - Second shell - holds up to 8 electrons - Third shell - tends to hold up to 8 electrons - OUTERMOST shell is the VALENCE shell - Containing valence electrons - Atoms are MOST STABLE when their OUTER shell is FILLED - Atoms tend to lose, gain or share electrons until they are surrounded by 8 valence electrons The Carbon Atom - Atomic number 6 - Has 6 protons + 6 electrons (#protons = #electrons) - Atomic mass 12 - Subtract 6 protons from 12 to determine number of neutrons - I.e. 12 - 6 = 6 neutrons - 6 protons + 6 neutrons = 12 - The 6 electrons - which shells do they orbit in? - 2 in first shell - 4 in second shell - Second shell can house up to 8 electrons - HAVING ONLY 4 valence electrons makes the carbon atom UNSTABLE - BECOMES STABLE when 4 more electrons ENTER second shell (during chemical bond formation)  - They may come from up to 4 OTHER atoms Not all Atoms of an Element are exactly the same Many elements have ISOTOPES, with the same number of protons but with different number of neutrons Therefore isotopes have a DIFFERENT ATOMIC MASS Some isotopes are UNSTABLE - “radioactive isotopes” - The UNSTABLE nucleus spontaneously DECAYS, giving off rays of different energy & subatomic particles - to return it to a stable state - Used as a tracer - carbon 14 dating, medical imaging… - Radiation kills healthy cells & cancerous cells Atoms INTERACT with other atoms to FORM molecules and compounds Molecules - Groups of 2 or more atoms held together in a stable association - Some molecules are made up of ONLY ONE ELEMENT - i.e oxygen gas has 2 oxygen atoms - Other molecules are made up of MORE THAN ONE TYPE OF ELEMENT - These are COMPOUNDS - Bound in proportions that never vary - I.e water always has one oxygen and two hydrogen atoms Chemical Bonds (the attraction between atoms) - Hold atoms together in molecules or compounds What Determines Whether Atoms Will Interact? The NUMBER OF ELECTRONS in their VALENCE SHELL UNFILLED VALENCE SHELLS make an atom “reactive” - Wants to FILL its valence shell - to become stable - These atoms WILL participate in chemical reactions The VALENCE SHELL - where atoms BOND together with other atoms An atom with eight electrons in the valence shell will usually NOT BOND - ‘Noble gases’ (not “reactive”) - Helium, neon, for example Chemical Bonds FORM in attempts to STABILIZE the Valence Shells of the interacting atoms to “fill” their outer shells The UNION between the electrons of neighbouring atoms is called a CHEMICAL BOND - THREE TYPES OF CHEMICAL BONDS that are found in biological molecules 1. Ionic bond 2. Covalent bond 3. Hydrogen bond - (discussed in a later lecture) Ionic Bonds One atom gains, one atom loses electron(s) AND both are attracted to each other as a result “Opposites Attract” Losing or gaining electron(s) CHANGES a neutral atom TO A CHARGED ION A charges ion has an electrical charge (ions are atoms that don’t have the ‘right’ number of electrons) An IONIC BOND is formed by the ATTRACTION of oppositely charged ions Example: the formation of SODIUM CHLORIDE - NaCl - table salt 1. Sodium atom LOSES an electron & BECOMES A POSITIVELY CHARGED ION 2. Chlorine atoms GAINS this electron & BECOMES A NEGATIVELY CHARGED ION 3. THE OPPOSITE CHARGES ATTRACT the 2 ions to each other Covalent Bonds Sometimes electrons are not taken but are SHARED instead Covalent Bonds are VERY Stable A COVALENT BOND forms when two atoms SHARE a pair of VALENCE electrons (one valence electron from each atom) Examples - Hydrogen Gas H2 - One pair of shared electrons (e-) - Single covalent bond - Oxygen Gas O2 - 2 pairs of shared e- - Double covalent bond, with 2 lines - Water H2O - 2 single covalent bonds Even 3 PAIRS OF ELECTRONS can be shared, forming a “triple” covalent bond Lecture 7 - The Human Body at the Molecular Level Hydrogen Bonds and Water WATER Why is it so Important to Life?? All Organisms CONTAIN Water (50-70% total body weight) LIFE ORIGINATED IN LIQUID WATER - Through the INTERACTIONs between atoms & molecules that were suspended in primordial seas - “chemical evolution” - This is called ABIOGENESIS Basically, Water was the VEHICLE that ENABLED those early molecular INTERACTIONS - SUSPENDING AND DISSOLVING the molecules - Allowing chemical reactions to occur - a primitive metabolism Therefore - this primitive metabolism NEEDED liquid water in order to operate - And WHEN Organisms MOVED TO LAND - They CARRIED WATER with them - INSIDE THEIR CELLS!! Knelt all of the major systems in your body depend on water - Water is STORED in blood and our organs, in - Intracellular fluids - Extracellular fluids  - Water is LOST through - Seat, urine, bowel movements, digestion, breathing - Need to REPLENISH the lost water Many of water’s roles in supporting life are due to its Molecular Structure AND a few Special Properties Water molecule - STRUCTURE One water molecules consists of ONE Oxygen atom and TWO Hydrogen atoms - Each Hydrogen atom is covalently bonded to the Oxygen atom - BUT the atoms do NOT EQUALLY SHARE the electrons in each electron pair - Therefore, they form POLAR Covalent Bonds “POLAR COVALENT BONDS” Make Water an ASYMMETRICAL molecule with positive charge on one side and negative charge on the other side This charge differential is called POLARITY and dictates how water INTERACTS with other molecules Water’s POLAR NATURE accounts for it’s amazing properties that are perfect for life “POLAR COVALENT BONDS” form when atoms DON’T SHARE electrons EQUALLY - which is what happens in a water molecule - The OXYGEN atom’s nucleus has MORE PROTONS (8) - this it MORE STRONGLY ATTRACTS electrons (than do the Hydrogen atoms’ protons) - ALL the electrons in the molecule spend MORE TIME NEAR the atom with the MOST PROTONS - Oxygen is MORE ELECTRONEGATIVE - It has GREATER ABILITY to attract electrons - A water molecule has NO NET CHARGE because the (+) and (-) charges balance each other A polar molecule, A water molecule is an example of a polar molecule, in which the distribution of shared electrons is not uniform. Because the oxygen atom pulls the shared electrons more strongly than the hydrogen atoms do, the oxygen side of the molecule is slightly negatively charged, and the hydrogen sides are slightly positively charged. INTERACTING Polar Water Molecules for “HYDROGEN BONDS” HYDROGEN BONDS form by the ATTRACTION BETWEEN (1) a hydrogen atom of a positively charged end of one polar molecule AND (2) the negatively charged end of ANOTHER polar molecule - Water Molecules are POLAR molecules - H-bonds can occur BETWEEN DIFFERENT molecules - or, WITHIN THE SAME molecule - H-bonds are relatively WEAK chemical bonds The HYDROGEN BONDS in Water molecules cause water molecules to “CLING” to other water molecules - It’s the POLARITY of water molecules - Enables HYDROGEN BONDING - Between molecules - Thus, water FLOWS AS A UNIT - Because the water molecules ‘CLING’ to each other… Hydrogen Bonding in Liquid Water - Molecules held loosely – bonds keep changing (in flux) – distance between molecules keeps changing – water “flows” (leaving no “spaces”) Hydrogen Bonding in Ice - Molecules held tightly at a set distance – water is “solid” (with “spaces” between molecules) Water’s Polarity & Hydrogen Bonding accounts for its amazing properties That are PERFECT FOR Life 1. Water is in a LIQUID STATE over a wide range of temperature – from 0C to 100C - This temperature range allows water molecules to exist as a liquid in most places on our planet - Other materials are gaseous at these temperatures - LIQUID WATER is PERFECT FOR LIFE on our planet – BECAUSE it can travel & carry materials – inside the body – and in the environment 2. Water is a SOLVENT for other molecules - Forms “spheres of hydration” - NOTE which part of the water molecule is attracted to each ion – i.e. opposite charges attract - Hydrophilic - Water loving - Binds with water - Hydrophobic - Water hating - Repels water 3. Water is COHESIVE and ADHESIVE DUE TO HYDROGEN BONDS… 1. Water molecules “cling” to EACH OTHER - COHESION makes water molecules PULL on each other as they CLING to each other 2. Water molecules “adhere” to OTHER MATERIALS - ADHESION makes water molecules ADHERE to other surfaces - Result - Adhesion and Cohesion make water FLOW and FILL spaces - Always IN FLUX - transporting materials (always moving) - As it “flows & fills” Water rolling on waxed paper - Water is VERY cohesive, and strongly stickers to itself forming droplets - Water has LOW adhesion to wax paper and forms “beads” of droplets that roll along the surface of the waxed paper. Water doesn’t stick well to waxed paper and “beads up” Blood “FILLS” & “FLOWS” through blood vessels BOTH are happening at the SAME TIME Water MOVES UP in Plants & Trees Water “FILLS” & “FLOWS” through all spaces BECAUSE of water's properties of COHESION & ADHESION COHESION also creates SURFACE TENSION at a WATER-AIR INTERFACE - Water molecules AT THE AIR-SURFACE INTERFACE  - “CLING” TIGHTLY to each other (cohesion, due to H-bonds) - Creating SURFACE TENSION – i.e. allowing the surface to resist external forces 4. Water TEMPERATURE rises and falls SLOWLY - High heat capacity – i.e. a great deal of heat is required to raise its temperature - Thus, WATER HOLDS HEAT, causing its temperature to drop or rise slowly - Water’s TEMPERATURE-STABILIZING EFFECTS PROTECT organisms from RAPID temperature changes - High percentage of ‘body water’ in organisms RESIST changes in body temperature - Keeping a relatively STABLE internal environment - WATER IN BLOOD HELPS TO DISTRIBUTE HEAT THROUGHOUT BODY - Body withstands cold EXTERNAL temperatures - As WARMED BLOOD circulates through the body - WATER EVAPORATING FROM A BODY’S SURFACE CARRIES AWAY HEAT, cooling the body - Sweat 5. FROZEN water is LESS DENSE than liquid water - A FIXED VOLUME OF ICE has FEWER water molecules than does the same fixed volume of liquid water - Because in ice – the water molecules are FURTHER APART - So, FEWER water molecules in the fixed volume of ice - And the fixed volume of ice weighs LESS than the same fixed volume of liquid water - FROZEN WATER ALSO EXPANDS – creating ‘SPACES’ between molecules - Causing ice to FLOAT - If ice sank, eventually all ponds, lakes, and even the ocean would freeze solid - Surface ice layers insulate liquid water below it – prevents it from freezing – allows life to exist under the frozen surface - Surface ice layers also provide a ‘walking’ surface for other animals Lecture 8 - The Human Body at the Molecular Level Organic Chemistry, Macromolecules, and Metabolism Although The Human Body is about 70% WATER, the rest consists mostly of CARBON BASED compounds Proteins, Fats, Carbohydrates, & Other Molecules in the body are composed of CARBON ATOMS that are BONDED TO EACH OTHER & TO OTHER KINDS OF ATOMS The study of Carbon Based Molecules is ORGANIC CHEMISTRY ALL CELLS have CARBON BASED compounds Carbon’s importance to life arises from its VERSATILE bonding behaviour ONE CARBON ATOM CAN BIND UP TO 4 OTHER ATOMS - Most readily to: H atoms, O atoms, other C atoms **ALWAYS 4 COVALENT BONDS with EACH C atom*** Carbon atoms – TOGETHER with other atoms - FORM many biological molecules of various sizes MOST organic molecules include “CARBON CHAINS” - That form a “CARBON SKELETON” specific for each type of molecules Variations in the CARBON SKELETONS contribute to the DIVERSITY of organic molecules The Methyl Group is the simplest building block that is used to build carbon compounds CARBON SKELETONS - May be STRAIGHT, BRANCHED, or arranged in CLOSED RINGS - The carbons are numbered to identify them - Also may include double bonds Hydrocarbons & FUNCTIONAL GROUPS HYDROCARBONS: - Hydrogen atoms attached to a carbon backbone - Non-polar & do not dissolve in water (hydrophobic) FUNCTIONAL GROUPS: - Single or cluster of atoms, covalently bonded to the carbon backbone - REPLACE one or more hydrogen atoms of skeleton of hydrocarbons - The number & arrangement of functional groups give each molecule its UNIQUE PROPERTIES - INCREASE solubility in water - And OTHER ADD NEW PROPERTIES There are seven functional groups that are important to the chemistry of life - Hydroxyl - Carbonyl - Carboxyl - Amino - Phosphate - Sulfhydryl (structural roles) - Methyl (non-polar) Functional groups provide NEW PROPERTIES to hydrocarbon molecules - Polarity (so it dissolves in water), acidity, basic quality, etc… Linear Hydrocarbons can EASILY take on Ring Shapes Carbon compounds may be in straight chains or in rings - The carbons are NUMBERED to IDENTIFY THEM - E.g. glucose (C8H12O6) THE BASIS OF METABOLISM IS THE “BREAKING” AND “MAKING” MOLECULES Cells join SMALLER organic molecules (building blocks) together to form LARGER molecules called MACROMOLECULES Macromolecules may be composed of Thousands Of Atoms Cells Also Can BREAK DOWN Macromolecules into SMALLER Molecules FOOD and METABOLISM Using Biologically Important Macromolecules The FOUR MAJOR CLASSES of biologically important macromolecules are FOOD!  1. Carbohydrates 2. Lipids 3. Proteins 4. Nucleic Acids - When we eat – food is BROKEN DOWN – and the smaller parts (BUILDING BLOCKS, MONOMERS) are ABSORBED by our bodies and cells - Our CELLS THEN USE these smaller parts TO MAKE (BUILD) out body parts The CHEMICAL (metabolic) MECHANISMS that cells use to MAKE & BREAK macromolecules are SIMILAR BUILDING (MAKING) - Monomers are JOINED by covalent bonds through a CONDENSATION REACTION (aka dehydration reaction) - One monomer provides a “hydroxyl group” (OH) - The other monomer provides a “hydrogen” (H) - Together these FORM a “water” molecules (H2O) - The remaining parts JOIN to form a “covalent” bond - This process is aided by “enzymes” - Synthetases - ENZYMES are proteins that speed up chemical reactions BREAKING DOWN – Macromolecules are DEGRADED when the covalent bonds connecting the BUILDING BLOCKS (monomers) are broken by a HYDROLYSIS REACTION During HYDROLYSIS, a water molecule is BROKEN (SPLIT) to H and OH - The “hydrogen” (H) atom & the “hydroxyl group” (OH) - Attach to where the covalent bond used to be - SEPARATING the monomers - Hydrolysis reaction dominate the DIGESTIVE process - Added by specific enzymes - Hydrolases Summary - Dehydration (Condensation) - Smaller Molecules COMBINE - A hydroxyl from one monomer end comes off… - And a hydrogen from the end of another monomer comes off - They combine to form water as a by-product - Hydrolysis - Larger Molecule SPLITS into smaller ones - Water ALSO is split… - Its parts are added… - To the ends where the polymer will “split” METABOLISM Is The WHOLE SET OF CHEMICAL REACTIONS Within A Living Body Metabolism – Cell Metabolism TWO CATEGORIES OF METABOLISM - Catabolism – the BREAKING DOWN of organic molecules i.e. proteins, carbohydrates, etc… - Usually involves RELEASING ENERGY from breaking chemical bonds - Hydrolysis Reactions - Anabolism – the BUILDING of organic molecules i.e. proteins, carbohydrates, etc… - Usually involves CONSUMING ENERGY – need to add energy when creating a chemical bond - Condensation/Dehydration Reactions