BIOL 1115 Chapter 5 Notes PDF

F24 BIOL 1115 Ch. 5 The Working Cell The Working Cell Learning Outcomes Upon completion of this chapter, you will be able to: 1. Explain why the plasma membrane is considered a “fluid mosaic”. 2. Describe the roles of...

F24 BIOL 1115 Ch. 5 The Working Cell The Working Cell Learning Outcomes Upon completion of this chapter, you will be able to: 1. Explain why the plasma membrane is considered a “fluid mosaic”. 2. Describe the roles of different types of phospholipids, proteins, and carbohydrates in the plasma membrane. 3. Recognize the three types of membrane proteins based on location within the plasma membrane. 4. Explain why plasma membranes are selectively permeable, and compare and contrast the processes of diffusion, osmosis, passive transport, and active transport. 5. Explain the difference between potential and kinetic energy, and describe how this relates to cells and the laws of thermodynamics. 6. Identify a reaction as endergonic/exergonic or catabolic/anabolic, when given information about the energy transfer and molecules involved. Explain how and why the cell uses ATP, and how ATP connects the two types of chemical reactions that occur in cellular metabolism. 7. Describe how enzymes lower the activation energy of chemical reactions, and why energy barriers are critical for chemical reactions that occur within biological organisms. Macromolecules of the Plasma Membrane: Lipids The Plasma Membrane The plasma membrane serves many functions: The boundary between the ___________________________ of the cell and the ___________________________ environment Controls what enters and exits the cell Houses enzymes involved in many _________________________ of the cell The plasma membrane is a fluid mosaic of lipids and proteins Lipid molecules form a ___________________________ Protein molecules are embedded in the plasma membrane ___________________________ on the surface of the plasma membrane act as cell identification tags 1 F24 BIOL 1115 Ch. 5 The Working Cell The Lipid Bilayer Recall: phospholipids are amphipathic Amphipathic = molecules that have ___________________________ and ___________________________ properties In water, phospholipids form a stable bilayer Hydrophilic _____________________ face outward (towards the water) Hydrophobic ____________________ face inward (away from water) Membrane Fluidity Cell membranes have the consistency of ________________________ at room temperature! Membranes must be fluid to function properly, but not TOO fluid Lipids have rapid lateral movement, but they rarely flip-flop Why would you expect flip-flops to be rare events? Lipid composition affects membrane fluidity Saturated fatty acids have ___________________________ resulting in straight chains that allow for maximum interaction between the fatty acid tails This makes membranes more viscous (thicker) Solid at room temperature, e.g., animal fats Unsaturated fatty acids have ___________________________, resulting in bent chains that space tails apart This makes membranes more fluid Liquid at room temperature, e.g., vegetable fats Cholesterol act as a fluidity buffer Has different effects on membrane fluidity at ___________________________ At warm temperatures (e.g., 37°C), cholesterol restrains the _________________ of phospholipids ▪ What is the effect on membrane fluidity? At cool temperatures, it maintains fluidity by __________________________________of phospholipids 2 F24 BIOL 1115 Ch. 5 The Working Cell Macromolecules of the Plasma Membrane: Proteins and Carbohydrates Membrane Proteins Peripheral membrane proteins Touch the membrane or another protein superficially ___________________________ interactions with hydrophilic lipid and protein groups Integral membrane proteins Anchored into membrane by interactions of hydrophobic amino acids with hydrophobic fatty acid tails of membrane lipids One type of integral membrane protein is transmembrane proteins ▪ Have hydrophilic portions on both sides of the membrane and at least one hydrophobic portion that spans membrane The plasma membrane is a mosaic of ___________________________ proteins __________________________ in the lipid bilayer The ___________________________ determine most of the membrane’s specific functions Membrane Carbohydrates Carbohydrates are found on the ___________________________ of the cell membrane They provide specificity for ___________________________ or ___________________________ interactions Glycolipids: sugars attached to a lipid (e.g., blood antigens that determine blood type) Glycoproteins: sugars attached to a protein (e.g., receptors) 3 F24 BIOL 1115 Ch. 5 The Working Cell ABO blood group antigens are glycolipids What kind of antibodies would be found in the plasma of… 1. Type A blood: 2. Type B blood: 3. Type AB blood: 4. Type O blood: Selective Permeability and Membrane Transport: Passive Transport Membranes are selectively permeable The cell membrane controls traffic into and out of the cell by being selectively permeable It allows some substances to cross but not others What makes the membrane selectively permeable? 1. Permeability of the lipid bilayer o ___________________________ pass through the membrane rapidly (e.g., CO2, O2, steroid hormones) o ___________________________ and ___________________________ do not cross the membrane easily 2. Transport proteins (Transmembrane) o Each transport protein is ___________________________ to the solutes it can transport o Molecules pass through the membrane via passive transport or active transport Passive Transport In passive transport, substances _________________________ through membranes without work by the cell No energy (ATP) is required Diffusion = tendency for particles to spread out spontaneously from where they are ___________________________ to where they are ___________________________ 4 F24 BIOL 1115 Ch. 5 The Working Cell Dynamic equilibrium is present when molecules move in opposite directions at equal rates Each solute in solution follows their own independent concentration gradient Passive Transport: Facilitated Diffusion Molecules that are not able to cross the lipid bilayer can still be passively transported across the plasma membrane via facilitated diffusion Does not require energy Facilitated diffusion = substances moving down a concentration gradient through transport proteins E.g., _______________ substances: water, ions Selective Permeability and Membrane Transport: Osmosis Osmosis Solutions are solute(s) dissolved in a solvent Water is the solvent for most of life’s solutions Osmosis is the diffusion of ___________________________ across a ___________________________ membrane Water diffuses across a membrane from the region of lower solute concentration (i.e., high water concentration) to the region of higher solute concentration (i.e., low water concentration) 5 F24 BIOL 1115 Ch. 5 The Working Cell Water and Facilitated Transport Water is a polar molecule that CAN diffuse across the lipid bilayer, because it is very small, but, it can only do so _______________ Aqua Some cell types (e.g., kidney cells, root cells in plants) require ________________________ of water either in or out of the cell Aquaporins are ____________________________ that facilitate the passive transport of water across the cell membrane Tonicity Tonicity = the ability of a solution to cause a cell to gain or lose water Hypertonic = environment has ________________________ solute concentration than inside of the cell Hypotonic = environment has _________________________ solute concentration than inside of the cell Isotonic = equal concentration of solutes inside and outside the cell ▪ Many marine organisms have cells that are isotonic to sea water, but organisms that live in ___________________________ or ___________________________ environments need a mechanism to prevent excessive uptake or loss of water Osmoregulation = the control of water balance, a necessary adaption for life outside of the marine environment Osmosis in Organisms Without Cell Walls Osmosis causes cells to ______________________ in a hypertonic solution, and _______________________ in a hypotonic solution How does the protist, Paramecium, osmoregulate? 6 F24 BIOL 1115 Ch. 5 The Working Cell Osmosis in Organisms with Cell Walls Plant cells do best in ___________________________ solutions: the rigid cell wall prevents membranes from rupturing, making them turgid In ___________________________ environments, plant cells become flaccid In ___________________________ environments they shrivel Selective Permeability and Membrane Transport: Active Transport Active Transport: Transport Proteins Some transport proteins can move solutes across the membrane __________________________________________________ Active transport requires energy in the form of ATP E.g., Na+/K+ pump Active Transport: Bulk Transport Large molecules/large quantities of smaller molecules can be actively transported across the membrane via ___________________________ or ___________________________ Exocytosis = membrane-bound vesicle from ___________________________ the cell fuses with the cell membrane and expels its contents ___________________________ Endocytosis = membrane folds inward, trapping material from _________________________ for use ___________________________ the cell In both exo- and endocytosis, ___________________________for vesicle fusion/creation and transport Cellular Reactions: Energy Transformations and Thermodynamics Energy and the Cell Plasma membrane is the site of many chemical reactions Cells transform energy through ___________________________ chemical reactions Two forms of energy 1. Kinetic Energy: the energy an object possesses due to its motion - the energy that is doing work, e.g., heat, light 2. Potential Energy: the energy stored in an object due to its position, e.g., chemical energy (the potential energy of molecules), the most important energy to the cell. 7 F24 BIOL 1115 Ch. 5 The Working Cell Organisms transform energy to stay alive Chemical energy is used when a chemical reaction releases the ___________________________ stored in ___________________________, which is then transformed into ___________________________ Organisms release chemical potential energy in food by breaking bonds Potential energy stored in the original molecules is released and may be transformed into kinetic energy Thermodynamics Thermodynamics is the study of _________________________________ Two “Laws of Thermodynamics” govern energy transformations: 1. First Law of Thermodynamics ▪ energy can be changed from one form to another, but it cannot be ___________________________ or ___________________________ ▪ E.g., a light bulb converts electrical energy into light energy, a plant converts light energy to chemical energy 2. Second Law of Thermodynamics ▪ Energy changes are not ___________________________, and every energy conversion increases the total ___________________________ of the universe ▪ Entropy = amount of disorder in a system, related to the number of possible ___________________________ that molecules in a system can take on ▪ In cells, some energy is always “lost” to heat, a type of kinetic energy that increases ___________________________ and therefore entropy Chemical reactions either release or store energy Two general types of reactions 1. Exergonic reactions are those in which energy is released 2. Endergonic reactions are those in which energy is consumed The amount of energy that is ___________________________ or ___________________________ is equal to the difference between the potential energy of the reactants and ___________________________ 8 F24 BIOL 1115 Ch. 5 The Working Cell Cellular Reactions: Cellular Metabolism and ATP Cellular Metabolism Cellular metabolism refers to all the reactions that occur within a cell Two types of metabolic reactions 1. Catabolic reactions: when complex molecules are broken down into simpler compounds (they are exergonic) 2. Anabolic reactions: complex molecules are built from simpler ones (they are endergonic) Is photosynthesis catabolic or anabolic? Anabolic and catabolic reactions are coupled by ATP The hydrolysis and synthesis of ATP links catabolic and anabolic reactions in the cell When ATP is hydrolyzed, potential energy is released ATP → ADP + Pi + free energy Energy used by anabolic reactions to build organic molecule When catabolic reactions release energy, that energy is stored as ATP The ATP is used to power cellular anabolic reactions ∴ energy released by exergonic reactions is used to power endergonic reactions = energy coupling Only possible because ATP is a renewable cellular resource ATP powers cellular work through phosphorylation When ATP is hydrolyzed, it transfers a phosphate group to the reactant (this process is called phosphorylation) The addition of the phosphate group makes the reactant ___________________________ and therefore more reactive, increasing its ___________________________ That energy is then used to drive chemical, transport, or mechanical work 9 F24 BIOL 1115 Ch. 5 The Working Cell Cellular Reactions: Enzymes Cellular reactions require enzymes Enzymes are proteins that act as ___________________________ Catalyst = a chemical that speeds up the rate of reactions without itself being ___________________________, can be used over and over Without enzymes, life’s reactions would take too long! Enzymes speed up reactions by lowering the activation energy for the reaction Activation Energy (AE) = the amount of energy reactants must absorb to ___________________________ (energy barrier) AE is often supplied as ___________________________ - instead of heat, organisms use enzymes. Enzymes speed up the chemical reactions by ___________________________ - they do not add energy Why do organisms use enzymes to lower activation energy, rather than supplying the activation energy via heat? A specific enzyme catalyzes each cellular reaction Enzymes are selective, and this selectivity determines _________________________________ occur in a cell Specificity is due to enzyme shape, much like a lock and key! Substrate = the ___________________________ on which the enzyme acts Active site = the ___________________________ to which the substrate binds Each cell has thousands of different enzymes, each performing a specific chemical reaction Each enzyme functions optimally at a specific temperature and pH 10 BIOL 1111 Ch. 20 Unifying Concepts of Animal Structure and Function Unifying Concepts of Animal Structure and Function Learning Outcomes Upon completion of this chapter, you will be able to: 1. Differentiate between anatomy and physiology. Explain how structure and function are linked, using real examples from multiple levels of organization in the human body. 2. Define phenotype and explain how phenotypes are a product of natural selection. 3. Compare and contrast the structure and functions of the four major tissue types in the human body. Recall and identify the different categories of epithelial tissue and understand their structure and function. Describe the structure and function of the different types of connective tissue. Recognize the different types of muscle tissue and describe their function. Recall and recognize the structure and function of a neuron. 4. Explain how different tissues make up organs. 5. Describe the general functions of each of the 12 organ systems in humans. 6. Describe the structural adaptations of animal organ systems that result in increased exchange with the external environment. 7. Explain the importance of homeostasis, and how negative feedback loops function to maintain it. Describe the steps and structures involved in the negative feedback loops that regulate body temperature and blood-glucose levels in humans. The Connection Between Anatomy and Physiology Human Development Humans are animals - as with all animals, we start as zygotes Between the zygote and newborn stages, human cells undergo 41 mitotic divisions = 241 = _____________________________ These cells differentiate, resulting in a newborn with over _____________________________ that interact to form tissues, organs, and organ systems An Introduction to the Human Body Anatomy: the study of structures and the relationships among structures Physiology: the study of how body structures function Animal structure has a hierarchy Two recurring themes in biology: 1. Life is organized at many hierarchical levels 2. There is a close relationship between structure and function 1 BIOL 1111 Ch. 20 Unifying Concepts of Animal Structure and Function Question: List and describe the levels of organization that are found in an individual human: The structure of a body part is related to its function For example, adaptations for flight: Forelimbs modified as wings with lightweight keratin ______________ Strong pectoral muscles, anchored to a keel (sternum) ________________________ of some organs Lungs with air-sacs Four-chambered heart Extended vision and coordination An animal’s phenotype reflects natural selection Phenotype = observable traits An organism’s phenotype reflects the relationship between _____________________________ Natural selection only acts upon _____________________________, and an organism’s phenotype is the result of natural selection It does not imply a process of conscious intervention, nor is it a response to a need Question: What can we infer from this image? (Note: infer means deduce or conclude from evidence) 2 BIOL 1111 Ch. 20 Unifying Concepts of Animal Structure and Function Tissues (Epithelial Tissue) Tissues Tissue: an integrated group of _____________________________ that share a common structure and perform a specific function Tissues are made of cells, junctions, and extracellular material Each of these components is specialized so the tissue can perform its specific function Animals have four major categories of tissue: 1. Epithelial tissue 2. Connective tissue 3. Muscle tissue 4. Nervous tissue Structure of Epithelial Tissue Occurs as sheet(s) of tightly packed cells joined by ______________________________ Little extracellular substances between them Has a free surface exposed to air or fluid Contains nerves but no _________________________ Location: cover body surfaces, line internal organs and cavities E.g., epidermis, stomach lining Functions of Epithelial Tissue Protection of internal organs or from external environment, e.g., skin Secretion - mucus, sweat, enzymes, e.g., sweat glands (all glands) Absorption – digested food (nutrients), e.g., small intestine Filtration – dirt particles, blood, e.g., respiratory tract, kidney Excretion – removal of waste products, e.g., kidney tubules 3 BIOL 1111 Ch. 20 Unifying Concepts of Animal Structure and Function Types of Epithelial Tissue Categorized by the _____________________ of surface cells, and the ________________________ of cell layers Number of layers: Simple: one layer Stratified: multiple layers Shape: Squamous: flat Cuboidal: cube-like Columnar: column-shaped Simple squamous epithelium Function: specialized for ________________________ Location: air sacs of the lungs, blood vessels o Has a specific name in some organs ▪ Endothelium lines the inside of blood vessels ▪ Endocardium lines the chambers of the heart Simple cuboidal epithelium Function: secretion or absorption of substances Location: kidney tubules, ducts of pancreas, thyroid glands Simple columnar epithelium Ciliated o Function: moving mucus, moving oocytes o Location: bronchioles, uterine tubes Nonciliated o Function: secretion and absorption o Location: stomach, small intestine, large intestine, gall bladder 4 BIOL 1111 Ch. 20 Unifying Concepts of Animal Structure and Function Stratified squamous epithelium Function: protects against abrasion, foreign invasion, water loss and UV radiation (skin only) Location: epidermis, lining the vagina and mouth Stratified cuboidal epithelium Function: protection, limited secretion and absorption Location: many glands including ducts of mammary glands, salivary glands, sweat gland ducts Stratified columnar epithelium Function: protection and secretion Location: pharynx, male urethra, salivary glands Tissues (Connective Tissue) General Characteristics of Connective Tissue Structure: sparse number of cells in a specialized extracellular matrix Cells _____________________________ an extensive extracellular matrix (ECM) ECM is composed of ____________________________ embedded in a liquid, solid, or gel Function: makes up the basic support structures of the body Connects the other _____________________________ into a manageable framework Holds organs in place, attaches _____________________________ to underlying tissues Major Types of Connective Tissue 1. Loose connective tissue o Structure: Loose weave of fibres o Function: _______________ body tissues together and _____________ body cavities ▪ Holds organs in place and connects other tissues together o Location: Surrounding organs in abdominal cavity 5 BIOL 1111 Ch. 20 Unifying Concepts of Animal Structure and Function 2. Fibrous connective tissue o Structure: Dense, due to the arrangement of many ________________________ in parallel bundles o Function: Supports body tissues and provides tensile strength (collagen) o Location: tendons (connect muscle to bone) and ligaments (connect bones to other bones) 3. Adipose tissue o Structure: Round cells packed with triglycerides ▪ Each fat cell contains __________________________ of fat stored for possible future use o Function: Specialized to store fat in adipose cells distributed throughout its matrix ▪ Insulates and stores energy o Location: Surrounds vital organs, under skin 4. Cartilage tissue o Structure: Collagen fibers embedded in a rubbery matrix plus cells ▪ No ____________________________; heals poorly o Function: Absorbs shock during movement o Location: Makes the skeleton of all vertebrate embryos; in most vertebrates it is replaced with ________________________ o Retained in nose, ears, trachea, intervertebral disks, and the ends of some bones 5. Bone tissue o Structure: Collagen fibers embedded in a solid matrix of calcium salts ▪ Collagen and calcium salts make bone hard, but not ___________________________ ▪ Contains blood vessels (vascularized); heals relatively rapidly o Function: Provides support and protection for the vertebrate body and its organs o Location: Bones that make up your skeleton 6. Blood: o Structure: Cells in a liquid extracellular matrix of ______________________, which contains water, salts, and proteins o Cellular component contains: ▪ Leukocytes (white blood cells) = immune system ▪ Erythrocytes (red blood cells) = oxygen transport ▪ Platelets = cell fragments functioning in clotting o Blood cells are made in red marrow of long bones (hard dense bones with a shaft and two ends) 6 BIOL 1111 Ch. 20 Unifying Concepts of Animal Structure and Function Tissues (Muscle Tissue) Muscle Tissue The _____________________________ tissue in animals Structure: long, excitable cells capable of contraction Functions: Body movement, posture, respiration, constriction of organs and blood vessels, heartbeat, body heat production Properties of muscle tissue: 1. Contractility: ability to _____________________________ with force 2. Excitability: capacity to respond to _____________________________ 3. Extensibility: can be _____________________________ beyond normal resting length 4. Elasticity: recoils t o original _____________________________ if stretched Types of Muscle Tissue 1. Skeletal muscle contracts to move bones for body movements (voluntary) 2. Cardiac muscle contracts to move blood through the heart (involuntary) 3. Smooth muscle contracts to moves the walls of internal organs, such as the stomach (involuntary) Muscle Tissue: Histology 7 BIOL 1111 Ch. 20 Unifying Concepts of Animal Structure and Function Tissues (Nervous Tissue) Nervous Tissue Forms a communication network Function: senses stimuli and rapidly _____________________________ from one part of the body to another _____________________________ and controls body activities Structure: the major cell of nervous tissue is the neuron Neurons carry signals by conducting _____________________________ Neurons consist of: Cell body Dendrites Axon Organ Systems Organs Consist of several tissues that are organized together In an organ, different tissues _____________________________ to perform specific functions Most organs have tissues that are ________________________ in arrangement Organs: Multiple Tissues That Work Together For example, the heart has: Cardiac muscle that generates contractions Epithelial tissues that line the heart chambers Connective tissues that make the heart elastic Neurons that regulate contractions Organs may be organized into organ systems Organ systems consist of several organs with ________________________, that act in a _______________________________ Organ systems are interdependent They work together to perform life’s functions An organism is a living whole that is greater than the sum of its parts 8 BIOL 1111 Ch. 20 Unifying Concepts of Animal Structure and Function There are 12 major organ systems in animals: Nervous, endocrine, circulatory, lymphatic, immune, respiratory, digestive, urinary, reproductive, muscular, skeletal and integumentary Summary of the Major Organ Systems The nervous and endocrine systems control and coordinate body functions The endocrine system produces chemical signals called hormones The nervous system produces and organizes electrical signals called nerve impulses 9 BIOL 1111 Ch. 20 Unifying Concepts of Animal Structure and Function The respiratory system gathers oxygen The respiratory system exchanges gases with the environment It supplies the body with oxygen, and disposes of carbon dioxide The circulatory system transports nutrients and oxygen The circulatory system is a composed of the ________________________ and a network of ________________________ The heart pumps blood throughout the body Blood travels through vessels and supplies ________________________, and carries ________________________ from various organs to the appropriate disposal sites The lymphatic and immune systems protect the body from infection The immune system defends the body against infection The lymphatic system (part of the immune system) carries lymph around the body, filters, ________________________ to the circulatory system The digestive system gathers food The digestive system is involved in ingestion and digestion of food Nutrients are eventually absorbed into the ________________________ Indigestible materials leave the body as ________________________ The ________________________ is the largest organ located INSIDE the body, and it is key to digestion 10 BIOL 1111 Ch. 20 Unifying Concepts of Animal Structure and Function The urinary system disposes of certain wastes The kidneys are organs within the urinary system that remove ________________________ produced by ________________________ Kidneys also regulate the ________________________ of the blood The reproductive system produces offspring The reproductive system produces gametes and sex hormones The female system supports the developing embryo The skeletal and muscular systems move and support the body The skeletal system provides the body with structural support Skeletal muscles in the muscular system move parts of the body because they are attached to ________________________ The integumentary system covers the body The integumentary system includes skin, hair and nails Protects the body from: Mechanical injury Infection Excessive heat or cold Drying out 11 BIOL 1111 Ch. 20 Unifying Concepts of Animal Structure and Function Skin is the human body’s largest organ Skin is made of layers: Epidermis = ____________________________ that protects against abrasion, dehydration, infection, extreme temperatures, replenished continuously Dermis = mostly ____________________________, contains resilient elastin fibres and strong collagen fibres Skin also includes muscles, nerves, blood vessels Hypodermis contains ________________________ Sweat glands and oil glands are embedded within the skin’s dermis Hair: Keratinized dead cells arising out of hair follicles located in the dermis Oil glands at the base of the follicle keep hair ________________________, muscles ________________________ hairs in response to cold, nerves sense hair________________________ Provides insulation (limited in humans) Nails: Protective coverings composed of keratin, facilitate ________________________ Exchange Mechanisms and Homeostasis Structural adaptations that help animals exchange material with their environments Animals are open systems They must exchange ___________________ and ____________________ with the environment; this exchange must extend to the __________________________ Various structural adaptations enhance exchange between animals and their environment Cells in __________________________________ can exchange materials directly with the environment 12 BIOL 1111 Ch. 20 Unifying Concepts of Animal Structure and Function Specializations for Enhancing Exchange Larger, complex animals have: Internal structures that increase surface area to service the exchange of materials to each and every cell of the body (e.g., respiratory system, digestive system) Organ systems that act together to provide the functional organism with ________________________ The internal environment must have a large enough surface area to function The respiratory system has an enormous internal surface area associated with a vast number of capillaries In complex animals, the exchange of materials between blood and body takes place through the interstitial fluid Homeostasis The internal environment of animals must be maintained within a narrow range of conditions, even if the external environment changes The active process of keeping the internal environment within that range is called homeostasis (maintenance of a steady state) Every organ system in the body _____________________________________ of some aspect of homeostasis Control of homeostasis depends on the nervous and endocrine systems Acting together or ________________________ ________________________ external and internal stimuli, and ________________________ actions that counteract changes E.g., Sudden large temperature change → sweating to cool off The nervous system detects changes and sends nerve impulses to counteract the disruption The endocrine system regulates homeostasis by secreting hormones. Nerve impulses cause ________________________; hormones usually ________________________ 13 BIOL 1111 Ch. 20 Unifying Concepts of Animal Structure and Function Feedback loops maintain homeostasis To maintain homeostasis, a system needs: Sensor: detects when a change has occurred, e.g., receptors, hypothalamus Control center: receives signals from the sensor and coordinates a response Effector: exerts a response based on information from the control center, e.g., cell, tissue Homeostasis depends on negative feedback Negative feedback: A mechanism to deal with stress to regain homeostasis Response opposes the initial stimulus Brings internal conditions back to tolerable range The body’s status is monitored and reported back to a control centre which causes an action that changes the status The control center Determines the set point, Compares the input with the normal range, Activates the effector, if needed Question: List five examples of things that are regulated in our bodies: 1. 2. 3. 4. 5. 14 BIOL 1111 Ch. 20 Unifying Concepts of Animal Structure and Function Homeostasis: Regulation of Temperature Regulation of Blood Glucose Blood glucose levels are tightly regulated by two pancreatic hormones: Glucagon: increases blood glucose by stimulating cells to release glucose into the blood ∴ ___________________________ blood glucose Insulin: stimulates cells to take glucose out of the blood and store it in cells ∴ _________________________ blood glucose 15 BIOL 1111 Ch. 20 Unifying Concepts of Animal Structure and Function Question: What happens if blood glucose regulatory mechanisms fail? A) Too little insulin/insulin resistance or too much glucagon: B) Too much insulin or too little glucagon: Questions for discussion What would a positive feedback loop look like? When might the body need such a loop to maintain homeostasis? Can you think of a biological example of positive feedback? Positive Feedback Draw and example of a positive feedback loop in the body. Identify the control center, sensors, and effector, stressor, and response. Our bodies are constantly maintaining homeostasis Think about everything that is regulated in our bodies: E.g., Blood pressure, Blood vessel diameter, Breathing rate, Carbon dioxide, Cell division, Collagen, Elastin, Heart rate, Hormones, Neurotransmitters, Oxygen, pH, Platelets, Red blood cells, Vitamins, Water, Ions (salt), White blood cells 16 BIOL 1111 Ch. 21 Nutrition and Digestion Nutrition and Digestion Learning Outcomes 1. Identify the three main reasons why animals eat. 2. List the main steps of cellular respiration, and the number of ATP molecules created at each step. 3. List the main steps of fermentation, and differentiate between lactic acid and alcohol fermentation. 4. Compare and contrast cellular respiration and fermentation in terms of efficiency, oxygen requirement, and by-products. 5. Differentiate between absorptive feeders and the four main types of ingestive feeder, and give examples of animals that fit into each category. 6. Describe the four stages of food processing. 7. Describe how a gastrovascular cavity works. 8. Describe the function of the crop and the gizzard, and provide examples of animals that have these organs. 9. Describe the organs of the human alimentary canal, the accessory glands, and the role of each in digestion. Explain how the movement of food through the alimentary canal is controlled. 10. Differentiate between chemical and mechanical digestion, and identify the sites at which they occur within the human digestive system. Describe the chemical digestion and absorption of proteins, carbohydrates, and lipids. 11. Explain how the structure of the small intestine increases absorption. 12. Describe the cause of digestive system disorders of heartburn, gastric ulcers, and constipation. 13. Define and explain the role of calories, macronutrients, and essential nutrients. 14. Explain the two ways in which dietary fibre can be categorized. 15. Explain the Glycemic Index, and what type of information it tells you. 16. Define the terms “essential amino acid” and “complete protein”. 17. Differentiate between omega-3 and omega-6 fatty acids. 18. Differentiate between vitamins and minerals. Explain the need for specific vitamins and minerals in our bodies, as well as the effects of deficiencies in those vitamins and minerals. Differentiate between water soluble and fat soluble vitamins. Cellular Respiration and Fermentation Why do animals eat? Animals eat to gain: 1. Organic molecules ▪ Need the building blocks to synthesize new _________________________ 2. Essential nutrients ▪ Nutrients that the organism cannot make themselves (e.g., essential vitamins and minerals) 3. Fuel for ______________________ ▪ Need to produce energy through cellular respiration 1 BIOL 1111 Ch. 21 Nutrition and Digestion Cellular Respiration Cellular respiration is summarised with the following: Three main stages to the overall process: 1. Glycolysis occurs in the cytoplasm of all cells 2. Citric acid cycle occurs in the cytoplasm of prokaryotes, and the matrix of mitochondria in eukaryotes 3. Oxidative phosphorylation occurs in the plasma membrane of prokaryotes, and the inner mitochondria membrane of eukaryotes Glycolysis produces ____________ ATP molecules Citric acid cycle produces ____________ ATP molecules ______________________________ produces ___________ ATP molecules Without oxygen, only glycolysis can occur Glycolysis and Fermentation Fermentation occurs in eukaryotic cells under low-oxygen conditions (e.g., _____________________________), and in prokaryotes that live in low-oxygen environments The only ATP producing step is ______________________________, which requires the ______________________________ NAD+ (nicotinamide adenine dinucleotide) Additional steps in fermentation ______________________________ NAD+ so that glycolysis can continue (in respiration, this occurs during oxidative phosphorylation) Lactic Acid Fermentation In lactic acid fermentation, NAD+ is regenerated when _________________ is converted to _______________________ o Used by muscle cells when the need for ATP is greater than the oxygen available (e.g., during intense physical activity) o Occurs in the same bacteria used to make cheese, yoghurt, soy sauce… Alcohol Fermentation In alcohol fermentation, NAD+ is regenerated when _______________________ is broken down into CO2 and ethanol o Used by yeast and bacteria o W use alcohol fermentation to make bread, beer, wine… 2 BIOL 1111 Ch. 21 Nutrition and Digestion Feeding Methods and Food Processing in Animals Animals eat to obtain molecules Animals ingest their food in one of two ways: 1. Absorptive feeders lack a mouth or ______________________________, and absorb nutrients through the body surface (e.g., tapeworms) 2. Ingestive feeders (most animals) eat other organisms through ______________________________ Food processing occurs in 4 stages 1. Ingestion: the act of eating 2. Digestion: ______________________________ food into molecules small enough for the body to absorb 3. Absorption: taking-up of the ______________________________ by cells lining the digestive tract 4. Elimination: removal of _____________________________ materials out of the digestive tract Four feeding mechanisms Suspension Feeders Extract and consume food particles suspended in water Question: What is one example of a suspension feeder? Fluid Feeders Suck nutrient-rich liquids from a living host (plant or animal) with hollow, needle-like mouth parts Question: What is one example of a fluid feeder? Bulk Feeders Ingest large pieces of food Have specialized structures for capturing and ingesting food (tentacles, pincers, fangs, teeth, etc.) Question: What is one example of a bulk feeder? Substrate Feeders Live in or on their food source Question: What is one example of a substrate feeder? 3 BIOL 1111 Ch. 21 Nutrition and Digestion Digestion occurs in specialized compartments Most animals have a specialized digestive tract Food is digested in organ compartments which house hydrolytic enzymes Some animals have a sac with a single opening called a gastrovascular cavity (the mouth), e.g., hydra Most animals have an alimentary canal Alimentary canal: a tube running between 2 openings (mouth to anus, more efficient) This tube is divided into ________________________ that process food sequentially: 1. Pharynx (= throat) 2. Esophagus 3. Crop (pouch that ________________________________ food pre- digestion) 4. Stomach 5. Gizzard (for _____________________________) 6. Intestine 7. Anus Humans DO NOT have crops or gizzards Crops are found in some _____________________________ Some animals (e.g., vultures) gorge themselves, and store extra food in their crop Gizzards are found in all birds, some reptiles, some fish, and some invertebrates Usually contain particles of _____________________________ that help mechanically break up large pieces of food 4 BIOL 1111 Ch. 21 Nutrition and Digestion Structure and Function of the Human Digestive System The Human Digestive System Consists of alimentary canal and accessory glands: What are the organs of the human alimentary canal? Digestive glands secrete digestive enzymes to __________________________: Include: Salivary glands, liver (gall bladder), pancreas List the structures that make up the human alimentary canal in the order that food passes through them: Functions of the Digestive System The digestive system has 4 key traits: 1. Motility: moves materials through the GI tract by ingestion → chewing → pushing into _____________________________ by tongue (swallowing) → peristalsis 2. Secretion: includes exocrine (digestive enzymes, bicarbonate, HCl) and endocrine (_____________________________ that regulate digestion) 3. Digestion: mechanical and chemical digestion 4. Absorption: passage of digested food molecules into _____________________________ or _____________________________ Digestion begins in the oral cavity Teeth break up food (mechanical digestion): Incisors bite Canines tear Premolars and molars grind and crush Salivary glands produce saliva Moistens and lubricates food for passage Contains buffers that _____________________________ Antimicrobial agents _____________________________ Salivary amylase begins the _______________________ of starch (chemical digestion) 5 BIOL 1111 Ch. 21 Nutrition and Digestion Swallowing The _____________________ pushes the chewed food (bolus) into the ______________________ Swallowing pushes the bolus into the ______________________ The swallowing reflex responds to food in the pharynx The epiglottis covers the opening of the _____________________________ during swallowing to prevent entry of food The esophageal sphincter ________________________________ to allow the bolus to enter the esophagus What is a sphincter? The esophagus squeezes food along to the stomach Peristalsis (_____________________________ in the walls of the alimentary canal) in the esophagus moves food boluses into the stomach Cardiac sphincter (__________________________________) regulates passage of food through the esophagus and into the stomach 6 BIOL 1111 Ch. 21 Nutrition and Digestion The stomach stores food and breaks down food The stomach is located just under the _________________________; can stretch up to 2 L Functions: _____________________________, _____________________________ and _____________________________ Secretes gastric juices containing: Pepsin = Enzyme that breaks down protein Strong acid (pH = 2) ▪ Kills ingested bacteria ▪ Breaks apart cells in food ▪ Denatures proteins Mucus Muscles in the stomach churn food The stomach churns food with _____________________________ every 20 seconds → form a mixture called gastric chyme Stomach has two openings: Cardiac sphincter Pyloric sphincter opens to allow the passage of chyme into the _____________________________ Heartburn = the occasional _____________________________ of chyme into the esophagus via the cardiac sphincter Bacterial infections can cause ulcers Gastric ulcers are open sores in the stomach lining Evidence suggests that a spiral-shaped prokaryote causes gastric ulcers: Helicobacter pylori growth erodes protective mucus and damages the stomach lining The Small Intestine The major organ of _____________________________ and _____________________________ Two accessory glands empty into the small intestine and aid in digestion: 1. Pancreas: produces _____________________________ (bicarbonate) to neutralize chyme, and _________________________________ 7 BIOL 1111 Ch. 21 Nutrition and Digestion 2. Liver: produces bile, which is then stored in the gallbladder. Bile _____________________________ fat droplets for attack by pancreatic enzymes Summary of chemical digestion in the small intestine Maltase, sucrase, lactase are made in the cells of nonciliated simple columnar epithelium lining the duodenum and secreted into the lumen Three Regions of the Small Intestine 1. Duodenum: o Shortest segment of small intestine (~25 cm) o Begins at the _____________________________ and merges with _____________________________ o Function = mixing of contents and secretions from _____________________________ and _____________________________ 2. Jejunum: o ~1 m long o Function = chemical digestion and absorption 3. Ileum: o ~2 m long o Joins to the _____________________________ at the _____________________________ o Function = absorption 8 BIOL 1111 Ch. 21 Nutrition and Digestion Structure of the small intestine Large surface area is for absorption. Folds of the intestinal lining, villi, and microvilli all contribute to the large surface area Absorptive surface area of the small intestine is ~250 m2 (size of a tennis court!) The small intestine is specialized for absorption Nutrients pass into epithelial cells of villi ____________________________ and _____________________________ are recombined into fats and transported in lymph Other absorbed nutrients such as ____________________________ and _____________________________ pass into the blood Liver processes nutrient-rich blood from the intestines Blood travels from the intestines to the liver via the hepatic portal vein The liver: stores nutrients (i.e., as glycogen) _____________________________ toxic substances _____________________________ nutrients to other substances the body can use Makes bile The large intestine reclaims water Undigested material passes to the large intestine or colon (1.5 m long, and 5 cm in diameter) Water is absorbed Feces are _____________________________ and _____________________________ Consists mainly of undigested material (fibre), bile salts, and bacteria Some _____________________________ in the large intestine are essential for vitamin production: Vitamin K Folic acid and other B vitamins 9 BIOL 1111 Ch. 21 Nutrition and Digestion Question: Why is it important in humans for water to be reabsorbed? The rectum stores feces The rectum is a muscular organ at the end of the large intestine Stores _____________________________ until they are eliminated Two sphincters: An involuntary sphincter A voluntary sphincter Calories and Macronutrients What is a “healthy diet”? An animal’s diet must provide: Fuel for the animal’s activities Raw materials for making the _______________________________________ Essential nutrients that the body ____________________________________ A healthy, nutritious diet provides all the nutrients our body needs in appropriate amounts Where does the energy from food go? We need energy for our cells to do work. Basal metabolic rate = the energy a _____________________________ needs to stay alive each day (~75% heating, cooling, digestion, etc.) Energy is also needed to perform “extra” activity (~25% standing, thinking, sleeping, sports) 10 BIOL 1111 Ch. 21 Nutrition and Digestion Energy needs are expressed in calories Calorie = a unit that describes the potential energy content of food Tells us how much cellular work can be powered by the energy released from the breakdown of that food Energy content is typically measured in kilocalories (1 kcal = 1000 cal), and dietary calories are actually kcal but written as “Calories” Many factors affect caloric needs, including a person’s: Age, sex, height, and physical activity levels Essential nutrients must be supplied by the diet Undernourished = deficiency in _____________________________________ Malnourished = deficiency in one or more _____________________________ Essential nutrients = materials that must be supplied through diet because the animal _____________________________ 4 classes of essential nutrients: 1. Essential fatty acids, e.g., linoleic acid 2. Essential amino acids (8 in total) 3. Minerals 4. Vitamins Macronutrients Nutrients that our body requires in _____________________________ Provide us with most of our energy! There are 3 macronutrients: 1. Carbohydrates 2. Proteins 3. Lipids Let’s review: Carbohydrates Practice: List the 3 elements carbohydrates are composed of: Practice: List 3 sizes of carbohydrates and give a specific example of each: 11 BIOL 1111 Ch. 21 Nutrition and Digestion Monosaccharides Recall: monosaccharides are simple sugars, e.g., glucose, fructose, galactose Glucose is the most easily used by the body: Circulates in the _____________________________ Main source of energy for the ___________________________ and _____________________________ Fibre Fibre consists of carbohydrates that cannot be _____________________________ Two types: Soluble fiber Insoluble fiber The Benefits of Fibre Soluble fibre lowers ______________________________ Binds cholesterol in small intestine and slows/prevents absorption ↓ risk of heart disease Insoluble fibre normalizes __________________________ and maintains bowel health ↓ risk of constipation, diverticular disease A high fibre diet: Helps control sugar levels by ________________________ of sugar ↓ risk of Type II diabetes Glycemic Index Measures how fast and how far blood sugar levels will rise after _____________________________ High GI foods: _____________________________ and converted to blood sugar immediately, causing blood sugar levels to _____________________________ Low GI foods: digested more slowly, causing a _____________________________ in blood sugar 12 BIOL 1111 Ch. 21 Nutrition and Digestion Let’s review: Proteins List the 4 main elements proteins are composed of: Proteins are relatively large molecules made up of _____________________________ joined together by _____________________________ Functions of proteins include: Forming hormones, enzymes, and antibodies Help the body regulate fluids Buffer pH Transport nutrients Amino Acids 20 amino acids used by cells in making proteins We can synthesize _______________ from other starting materials Our bodies cannot make _______________________ (=essential amino acids), so we must get them from our diets: A “complete” or “whole” protein (i.e., animal protein) contains an _____________________________ of all 8 the essential amino acids necessary for the dietary needs of humans Essential amino acids can also be obtained from the _____________________________ of plant foods Let’s review: Lipids List the 3 elements lipids are composed of: Functions of lipids include: Stored energy (adipose tissue) Organ protection Temperature regulation Lipid membrane around cells Derivatives of vitamins and hormones Emulsifiers to keep fats dispersed in body fluids 13 BIOL 1111 Ch. 21 Nutrition and Digestion Types of Fatty Acids 3 fatty acids and one glycerol molecule make a _____________________________ Dietary fats are defined by the structure of the fatty acid attached to glycerol 1. Saturated fatty acid: Carbon chains fully saturated with hydrogen 2. Monounsaturated fatty acid: Carbon chain with one unsaturated double bond 3. Polyunsaturated fatty acid: Carbon chain with two or more double bonds Essential Fatty Acids Required for good health but humans __________________________________ to synthesize them Only _____________________________ must be consumed 1. Alpha-linolenic acid (an omega-3 fatty acid) 2. Linoleic acid (an omega-6 fatty acid) ▪ Both are used to make phospholipids of cell membranes ▪ Both can be converted into other important molecules (i.e., anti-inflammatory molecules) ▪ Both are found in vegetable/plant oils, nut, grains What do “omega-3” and “omega-6” mean? Polyunsaturated fatty acids (PUFAs) have _____________________________ bonds There are two types of PUFAs in dietary oils: omega-3 and omega-6 Distinguished by the position of the double bond closest to omega Omega-3 fatty acids have their first double bond at the _____________________________ from the methyl end of the carbon chain, while omega-6 fatty acids have their first double bond at the _________________________ from the methyl end 14 BIOL 1111 Ch. 21 Nutrition and Digestion Vitamins and Minerals A healthful diet includes 13 vitamins Recall: A healthful diet must provide enough food for energy, building blocks to make new molecules, and vitamins and minerals Vitamins = _____________________________ compounds that are essential for our body function Required in _____________________________ Humans do not have the enzymes to make most vitamins Function as coenzymes = assist metabolic reactions Two types of vitamins: Water-soluble vitamins Fat-soluble vitamins Water Soluble Vitamins 15 BIOL 1111 Ch. 21 Nutrition and Digestion Folic acid decreases risk of birth defects Folic acid is required in the first __________________________________ for proper development of the __________________________, __________________________, and __________________________ Prevents spina bifida (type of neural tube defect) The current recommended intake for folic acid is 400 micrograms/day Sources of folic acid: Dark green vegetables, e.g., broccoli and spinach Dried legumes, e.g., chickpeas, beans, lentils In Canada, folic acid is added to all white flour, enriched pasta, and cornmeal products Fat Soluble Vitamins Includes vitamins A, D, E, and K You need to have fat in your diet to absorb these vitamins Dietary fat → bile secretion → enzymatic digestion → absorption of vitamins Stored in “fatty organs”: _____________________________, _____________________________, and _____________________________ Excess can accumulate and result in _____________________________ Rarely results from excessive dietary intake More likely from improper use of _____________________________ Why do water soluble vitamins not build up to toxic levels? 16 BIOL 1111 Ch. 21 Nutrition and Digestion What are minerals? Dietary elements, aka minerals, are Inorganic elements that are essential for body processes Major dietary minerals are required at > 200 mg/day Humans need seven major dietary minerals: calcium, phosphorus, potassium, sulfur, sodium, chlorine, and magnesium Micronutrients: Other dietary nutrients, such as vitamins and trace elements, are needed by the human body in _____________________________, < 100 mg/day Include iron, cobalt, chromium, copper, iodine, manganese, selenium, zinc, and molybdenum 9 of the essential minerals in the body account for < 0.01% of your body weight Functions of Dietary Elements Minerals represent much of the chemical composition of bones (e.g., _____________________________ and _____________________________) Contribute to nerve and muscle activity (e.g., _____________________________, _____________________________, _____________________________) Many minerals (e.g., magnesium) can be parts of proteins and enzymes and support their function = cofactors Iron is the oxygen-binding component of heme in hemoglobin Mineral Requirements 17 BIOL 1111 Ch. 21 Nutrition and Digestion Making Informed Dietary Choices Water Water is the main component of your body! Makes up 60% of your weight What purpose does water serve? Carries nutrients to cells Required for cell _____________________________ Allows kidneys to expel _____________________________ Prevents _____________________________ and constipation Provides a moist environment for ear, nose, throat tissues How much water should you drink? Depends on: Body mass Activity level Where you live (environmental conditions) Rule of thumb → 33 mL/kg of body mass If you are 70 kg, 33 mL x 70 kg = 2310 mL water/day = 2.31 L water/day How can you tell if you are dehydrated? Urine colour/odour: urine should be pale yellow and not strong smelling Reading Food Labels Food labels provide important nutritional information Ingredients are listed from __________________________ amounts Nutrition facts include: Serving size Calories per serving Amounts of selected nutrients per serving, and as a % of daily value (based on 2000 kcal/day diet) Recommendations for daily minimums of selected nutrients (determined by scientific panel) How can we make healthy dietary choices? Understand that no single diet is suitable for everyone Even our best evidence can be flawed or new conditions will lead to new recommendations You can use the Canada Food Guide as a start o Use _______________________ 18 BIOL 1111 Ch. 22 Gas Exchange Gas Exchange Learning Outcomes Upon completion of this chapter, you will be able to: 1. List the three main phases of gas exchange in animals that possess lungs. 2. Explain why the key features required for all respiratory surfaces are critical to the function of gas exchange. 3. Describe the advantages and disadvantages of breathing in air and water. 4. Describe the anatomical and physiological adaptations found in fish that allow them to perform gas exchange in water. 5. List the parts of the human respiratory system in order from where air enters the respiratory system to where oxygen is picked up by the blood. 6. Explain how the structure of the human lung is well suited for efficient gas exchange in air, particularly with respect to the alveoli. 7. Describe how inhalation and exhalation occur in humans. 8. Describe the cause and treatment of respiratory distress syndrome in prematurely born infants. 9. Explain why air pollutants, e.g., tobacco smoke, can destroy the human respiratory system. 10. Describe the negative feedback loop that controls breathing, including the specific anatomical structures involved. 11. Explain how O2 enters the blood and gets to the tissues, and how CO2 leaves. 12. Describe the structure of hemoglobin, and explain why hemoglobin is required to transport oxygen in the blood. 13. Explain the role of the placenta in fetal gas exchange. Comparing Respiratory Surfaces in Animals Why do we need to exchange gases? Cells continually use O2 and make CO2 as a result of _____________________________________ 2 organ systems work together to bring oxygen TO cells and take carbon dioxide AWAY 1. Respiratory system: for gas exchange between an organism and its environment 2. Cardiovascular system: transports gases in blood Failure of either system leads to rapid cell death from _____________________________________ How are gases exchanged? Three phases of gas exchange occur in organisms with lungs: 1. Breathing (aka ventilation, flow of air over a respiratory surface) 2. Transport of oxygen and carbon dioxide in the blood 3. Exchange of gases with body cells 1 BIOL 1111 Ch. 22 Gas Exchange Animals exchange O2 and CO2 across moist body surfaces A respiratory surface is where oxygen diffuses _______________, and carbon dioxide diffuses _____________. o Must be moist, as gases must be dissolved in water to diffuse o Must be thin for efficient diffusion o Must have high surface area relative to animal’s volume What about animals that do not have lungs? In some animals, e.g., flat worms and hydra, the skin may be used for gas exchange In earthworms, gas exchange occurs at capillaries below skin Animals must be _________________ and restructured to ____________________ environment Respiratory surface of animals In most animals, body surface is not large enough for gas exchange Evolution of _______________________________________ respiratory organs to increase surface area for gas exchange o Gills in fish and aquatic amphibians o Lungs in amphibians, reptiles, birds, mammals Gills are adapted for gas exchange in water Gills are feather-like out-foldings of the body surface o Distribution of gills over the body can vary o Commonality: _________________________ for gas exchange Gas exchange with water has limitations: o Water holds only ___________________ of the oxygen that air does o Water is denser than air, requires more energy to ventilate In a fish, gas exchange is enhanced by: o High surface area of gills o Ventilation of the gills (moving water past the gills) o Use of a countercurrent exchange system ▪ Blood flows in opposite direction to H2O passing over the gills o Enable fishes to remove >80% of O2 dissolved in H2O 2 BIOL 1111 Ch. 22 Gas Exchange In your own words, describe how countercurrent flow maintains a concentration gradient of oxygen and carbon dioxide that maximises gas exchange. Air as a respiratory medium Using air to breathe has two big advantages: 1. Air contains _____________________________________ concentrations of O2 than water does 2. Air is ________________________________ and __________________________________ than water But, air-breathing animals still _____________________________________ through their respiratory surfaces (REMEMBER: they need to be damp!) o This problem is reduced by respiratory surfaces that are folded into the body, and open through narrow tubes to the outside Lungs are internal sacs lined with moist epithelium Tetrapods can be split into 4 major groups when it comes to respiratory systems: 1. Amphibians use _______________________________ lungs and their body surfaces 2. Most reptiles have lower metabolic rates and _____________________________________ lungs 3. Birds have higher metabolic rates and more _____________________________________ lungs 4. Mammals also have higher metabolic rates and more _____________________________ lungs 3 BIOL 1111 Ch. 22 Gas Exchange Structure of the Human Respiratory System The human respiratory system Air is inhaled _______________________________________ into the nasal cavity o Air is filtered by hairs and mucus surfaces, warmed and humidified, and sampled for odours From the nasal cavity, air next passes through: 1. The pharynx 2. The larynx (past the ___________________________) 3. Into the trachea (held open by _____________________________________) 4. Into the paired bronchi 5. Into bronchioles 6. To the alveoli: __________________________________ of air sacs where gas exchange occurs Epithelial cells of the respiratory tract (except smallest bronchioles and alveoli) are covered by cilia and a thin layer of mucus What are alveoli? Alveoli are clusters or air sacs located at the end of small bronchioles o 300 million per lung! Well-adapted for gas exchange, with _____________________________________ of capillaries Here: o O2 diffuses ____________________________ the blood o CO2 diffuses ____________________________ of the blood Surfactants keep alveoli lubricated and open Surfactants are specialized secretions that keep the walls of the alveoli from ____________________________ Babies born 6 weeks or more before they are due may struggle with respiratory distress syndrome o Due to an inadequate amount of lung surfactant o Treatment: administration of artificial surfactants to preterm infants 4 BIOL 1111 Ch. 22 Gas Exchange Function of the Human Respiratory System Mechanics of breathing Breathing is the result of changes in pressure in the chest cavity Boyle’s law: volume and pressure are inversely related Gases fill a container completely, unlike liquids If the volume of a container ↑, the pressure of the gases inside will ↓, and vice versa How does air move into and out of the lungs? Inhalation o __________________________ and __________________________ contract o Volume inside thoracic cavity ↑ ∴ pressure inside the cavity ↓ o Air flows into the lungs down its pressure gradient Negative pressure: air pulled into lungs Exhalation o Muscles ________________________ o Elastic recoil and surface tension in alveoli pulls inward o Volume inside thoracic cavity ↓ ∴ ↑pressure in the lungs o Air is pushed out 5 BIOL 1111 Ch. 22 Gas Exchange Breathing is an involuntary action Breathing is usually controlled by the autonomic nervous system o CAN also be under voluntary control. Breathing control centres in the brain (pons and medulla oblongata) sense and respond to CO2 levels in the blood ___________________________ signals an increased dissolved CO2 o Increases the rate and depth of breathing. Low blood pH initiates a feedback loop Sensor: receptors inside of blood vessels Control center: medulla oblongata Effectors? Physiological effect: increased rate and depth of breathing → less CO2 in blood o Increases blood pH 6 BIOL 1111 Ch. 22 Gas Exchange How do air pollutants affect the function of the respiratory system Elasticity of alveoli is important for exhalation Air pollutants can cause damage to alveoli and ____________________________ (e.g., can paralyze cilia!) o The worst air pollutant for this is tobacco smoke o Smoking causes emphysema, a breakdown of the ____________________________ in alveolar walls, which results in air not being exhaled properly o Alveoli lose _______________________, making it difficult to exhale Smoking Kills Smoking can also cause: o Lung cancer o Heart attacks and strokes o Increased blood pressure o Heart failure Smoking accounts for 90% of all lung cancer cases, and increases the risk of other types of cancer o Adults who smoke die on average 13-15 years earlier than non-smokers Smoking causes 125 Canadians to die per day: more than deaths due to alcohol, opioids, suicide, murders, and traffic collisions combined Question: In your own words, explain how smoking can lead to the following: 1. Lung cancer: 2. Heart attack/stroke: 3. Increased blood pressure: 4. Heart failure: 7 BIOL 1111 Ch. 22 Gas Exchange Gas Diffusion Between the Respiratory System and Circulatory System Blood transports respiratory gases The cardiovascular system is responsible for ___________________________ in humans The heart pumps blood to two regions: 1. The ___________________________ pumps oxygen-poor blood to the lungs ▪ In the lungs, blood picks up O2 and drops of CO2. 2. The ___________________________ pumps oxygen-rich blood to the body ▪ In the body tissues, blood drops off O2 and picks up CO2. What causes gases to move from one area to another? Atmosphere made up of mixture of gases (e.g., O2, CO2, N2) o Their total pressure = atmospheric pressure Partial pressure = pressure of 1 type of gas in the mixture (e.g., O2) Dalton’s Law: total pressure = sum of all partial pressures Gas moves from high → low partial pressure 8 BIOL 1111 Ch. 22 Gas Exchange Diffusion of gases Gases move from areas of ______________________________ to areas of ______________________________: Notation: PO2 = partial pressure of oxygen; PCO2 = partial pressure of carbon dioxide In the lungs o Higher PO2 inside alveoli than in blood surrounding them ∴ O2 diffuses from alveolus → blood o Higher PCO2 in blood than in alveoli ∴ CO2 diffuses from blood → alveolus In the tissues o Higher PO2 in capillaries than in body cells ∴ O2 diffuses from blood → cells o Higher PCO2 in body cells than in blood ∴ CO2 diffuses from cells → blood Hemoglobin transports oxygen in the blood Oxygen is ___________________________ in water (and therefore, blood) O2 diffuses from alveoli into the blood and then into RBCs, where it binds to hemoglobin Hemoglobin is a protein found in very high levels in RBCs: o Has __________________________ and iron-containing heme group that are responsible for O2 binding Is all blood red? Red, iron-containing hemoglobin is used by almost all vertebrates and many invertebrates Blue, copper-containing pigments are used instead by molluscs and arthropods The human fetus exchanges gases with the mother’s blood A human fetus ___________________________ with its lungs o It exchanges gases with maternal blood in the placenta In the placenta, maternal blood and fetal blood ___________________________ to each other o No mixing between maternal and fetal blood At birth, an ___________________________ in fetal blood triggers anatomical changes to the fetal circulatory system and causes the newborn to ___________________________ 9