Physiology of Plants and Animals PDF

Defensive Stratgies: -​ Everything must defend themselves in order to complete their lives and produce young Gaboon Viper -​ Sit and wait strategy (camouflage and ambush) -​ parasite:lives on/in another organism of another species -​ micropathogens: Covid/spanish flu...

Defensive Stratgies: -​ Everything must defend themselves in order to complete their lives and produce young Gaboon Viper -​ Sit and wait strategy (camouflage and ambush) -​ parasite:lives on/in another organism of another species -​ micropathogens: Covid/spanish flu -​ Very small in size -​ Replicate very quickly -​ Undergo direct replication in host -​ Easily transmitted directly -​ Benefits of attack/defense must outweigh costs -​ Basic defense (Bacteria) -​ Have “immune” defenses -​ CRISPR-cas9 -​ Clustered regularly inter-spaced short palindromic repeats -​ Acts by snipping out parts of viral nucleic acid -​ Basic Defense (animals) -​ Structural -​ Spines, thorns, etc -​ Foul smell -​ Fulmar petral -​ Foul, oily projectile regurgitate -​ Poison -​ Plants -​ Constitutive and inductive -​ Constitutive:preformed, permanently present -​ ex: compounds all have a negative impact on insect grazers -​ Inductive:induced by attack -​ Ex: summon natural enemies of insect herbivores and exert effect on nearby plants -​ Camouflage is also called cryptic coloration -​ Poisons -​ Compounds that are either produced or sequestered by animals -​ sequestered=consumed and stored -​ Poisons have to be consumed or sprayed/squirted onto exposed skin/eyes, etc -​ Venom -​ Introduced by a bite/sting -​ Result is often fatal -​ Can be purely defensive, or both offensive and defensive -​ Snake Venom -​ Only 200 of 2000 snakes are venomous -​ Primarily used for attack -​ Snakebite antidote is running out  -​ Aposematic Coloration -​ Warning coloration -​ Indicated unpalitabilty -​ Mimicry -​ Mullerian: imitative similarity, honest signal, actually venomous, two or more venomous species develop similar characteristics -​ Batesian: dishonest signal, not actually venomous, a palatable species imitates an unpalatable species Defensive Strategies-Immune System: 1.​ Recognize invader 2.​ Mount reaction to it -​ Infecting Agents -​ Mostly microbes -​ Viruses and bacteria -​ Can also be protozoa and worms -​ All viruses and many bacteria and protozoa only replicate inside cells -​ Some bacteria, protozoa, and larger parasites live in extracellular spaces -​ External Defenses -​ Skin -​ Very tight gap junctions between cells -​ Inflammatory Response -​ 1. Increased blood supply -​ 2. Increased permeability of capillaries -​ 3. Migration of leukocytes -​ Pathogens cause inflammation -​ Innate Immunity -​ Natural or native immunity -​ Poised and ready for rapid response -​ Non-specific and doesn’t have memory -​ Myeloid line -​ Cells that originate in bone marrow and are a key part of the bodys innate immune system -​ Soluble Factors -​ Proteins and peptides -​ Complement 30 proteins -​ Protect cells against invasion by viruses -​ Made up of lytic, opsonins, chemotactic and interferons -​ Opsonization: macromolecule that becomes attached to the surface of a microbe and can be recognized by surface receptors of neurtropils and macrophages and increases the efficiency of phagocytes -​ Phagocytosis: a cellular process where a cell, called a phagocyte, engulfs and destroys large particles like bacteria, dead cells, or foreign substances by surrounding them with its cell membrane and bringing them inside to be digested -​ Adaptive Immune Response -​ Highly specific and has memory -​ potency /strength increases with repeated exposure to pathogen -​ Triggered into action by antigen presentation -​ T-cell: matures in thymus gland and organized adaptive immune response -​ Two basic types -​ Helper T-cells -​ these cells "help" other immune cells by sending signals to activate them against specific pathogens. -​ Cytotoxic cells -​ Destroy infected cells by killing htem -​ B-cell: matures in bone marrow and produce humoral response -​ Plasma cells produce antibodies -​ Made up of plasma cells and memory cells -​ Memory cells survive for a long time as part of a clone -​ Epitope: the portion of the antigen that combines with the antibody -​ Major Histocompatibility Complex -​ MHC1: associated with cellular response (intrinsic antigen) -​ MHC2: associated with humoral response (extrinsic antigen) -​ Antigen is presented with either MHC1 or MHC2 -​ Soluble Factors (antibody) -​ Flexible adaptor -​ Y-shaped -​ Two inner heavy chains and two outer light chains -​ FAB receptor binds to antigen -​ Antibody Types -​ IgG Monomer: classic y shape, main antibody in secondary immune response -​ IgM Pentamer: primary immune response against blood inhibiting extrinsic microbes -​ IgA Dimer: secondary immune response, oposiner -​ IgD Monomer: function poorly understood -​ IgE Monomer: associated with allergic response -​ Snake Antivenoms -​ Snake venom is 95% protein -​ Antivenom is antibodies (immunoglobullins raised in horses) agatine the antigenic venom -​ This is a type of passive immunity…it is injected -​ An be monovalent (neutralize venom of one species) or polyvalent (neutralize venom of multiple species) -​ Vaccine -​ First developed in 1798 by Edward Jenner -​ Epidemic: sudden increase in prevalence (% of population infected) -​ Pandemic: epidemic over a wide area  -​ Endemic: constant presence of a disease within a specified geographical area (low prevelance) -​ Hyperendemic: constant disease presence at a very high prevalence in all age groups -​ Novel Pathogen -​ Pathogen that enters a community with no herd immunity -​ May arise through accidental importaiton -​ Mutations produce new strains -​ R0: the reproductive rate of the pathogen -​ Basically it is the number of new hosts infected by an infectious host in a population that is 100% susceptible -​ Epidemics -​ The basic theory is–susceptible to infected to recovered -​ Lethality -​ Mortality rather than morbidity -​ Percent of infected cases that die -​ Zoonoses -​ Transmissible from vertebrate animal to man -​ Mosquito transmitted diseases are sometimes zoonoses -​ Ex: malaria isn’t and yellow fever is Reproduction: -​ Asexual: requires one parent organism -​ Sexual: requires two parents, and sperm and egg gametes must fuse to from zygote -​ Many invertebrates produce by fission -​ Seperation of parent into 2+ individuals of approximately the same size -​ Also common in invertebrates is.. -​ Budding -​ Fragmentation -​ Pathogenesis: egg develops without being fertilized -​ Semelparity: single reproductive episode before death -​ Heloparity: multiple reproductive episodes over lifespan -​ external fertilization: eggs shed by female are fertilized in external environment -​ internal fertilization: eggs are fertilized internally (within female reproductive tract) -​ Most animals exhibit cycles in reproductive activity -​ Are controlled by hormones and environmental cues -​ Simultaneous Hermaphroditism: self fertilization-both gametes present -​ Sequential hermaphroditism: being able to change sexes -​ Protandry: male to female -​ Protogyny: female to male -​ Oliparity: eggs laid outside of body -​ Ovoriliparity: eggs hatch in mothers uterus -​ Viviparity: the eggs/embryos develop inside mother (most mammals) -​ Insects -​ Have separate sexes with complex reproductive systems -​ Mammals -​ Male: -​ the male testes have highly coiled tubes -​ Sperm forms in seminiferous tubules where it then passes into coiled tubules of the epidermis -​ During ejaculation sperm are propelled through the muscular vas deferns, ejaculatory duct and exit through the urethra -​ They have three accessory glands all of which produce some amount of sperm, the seminal vesicles, prostate gland and the bulbourethral gland -​ Semen is made up of sperm cells, fructose (energy source for sperm), and acid-based buffers (create suitable environment for sperm) -​ Female: -​ Has two ovaries -​ Each ovary is enclosed in a tough protective capsule and contains many follicles -​ Follicles consist of one egg cell surrounded by one or more layers of follicle cells -​ The process of ovulation expells an egg cell from the follicle -​ The egg cell sis released near the opening of the oviduct or fallopian tube -​ The cilia in the fallopian tube move the egg to the uterus -​ Ovulation marks the end of the follicular phase and the start of the luteal phase -​ Luteal Phase: -​ The cells of the ruptured mature follicle form a structure called the copus luteum -​ LH after ovulation initiates transformation of the corpus luteum -​ If the oocyte in the oviduct is not fertilized the corpus luteum degenerates -​ If fertilization occurs the corpus luteum grows and continues to secrete hormones -​ The hormones are mainly progesterone and estrogen -​ Estrogen stimulates the growth of the endometrin of the uterus and the production of progesterone receptors in the endometrium -​ Fertilization -​ Is an acrosome reaction -​ This is where the membrane fusion activates the egg -​ When the sperm makes contact with the eggs plasma membrane it triggers a release of calcium from internal organnells, this starts at the point of sperm entry -​ The release of calcium causes a change in membrane potentional which prevents other sperm from binding -​ Oogenesis: This is the process by which a females ovaries create eggs and it starts in the embryonic stage. in foetal ovaries, diplooid oogania divide by mitosis to produce many more oogonia.  -​ All oogenia undergo the first stage of meiosis during foetal life and then are primary oocytes -​ Primary oocytes remain as such until they are ovulated, the first meiotic division occurs on ovulation -​ Second meiotic division occurs only if the egg is fertilized Osmoregulation and Excretion: -​ These processes require energy -​ Osmoregulation: regulates solute concentrations and balances the gain and loss of water -​ Requires a balance between osmotic gain and loss of water -​ Freshwater animals: show adaptations that reduce water uptake and conserve solutes -​ desert/marine: face environments that can quickly deplete body water -​ Excretion: getting rid of nitrogenous metabolites and other waste products -​ Osmosis: movement of water across a selectively permeable membrane -​ Osmolarity: solute concentration of a solution determines the movement of water across a selectively permeable membrane -​ Isoosmotic: flow of water is equal in both directions -​ Hypoosmotic: less solute -​ Hyperosmotic: more solute -​ Water flows hyperosmotic to hypoosmotic -​ Osmoconformers: isometric with their surroundings -​ Most marine invertebrates -​ Sterioaline: narrow salinity range -​ Eriryhaline: wide range -​ Marine bony fish lose water through osmosis and gain salt through food/diffusion -​ Freshwater fish: gain water through osmosis and loss solute through diffusion -​ Arihydrobiosis: can lose almost all body water and survive in a dormant state -​ Desert: have nocturnal lifestyle and other adaptations that help prevent water loss -​ Adaptations -​ Kidneys adapt to minimize water loss -​ Concentrated urine -​ Dry feces -​ Production of uric acid instead of urea -​ Water can be stored by animals in fatty deposits in their tails and other tissues -​ Transport epithelia: specialized epithelial cells that regulate solute movement -​ Essential components of osmotic regulation and metabolic waste disposal -​ Seabirds: have a nasal salt gland that helps excrete slat -​ Ammonia: common in aquatic animals -​ Urea: liver of mammals and most adult amphibians convert ammonia to urea -​ Energetically expensive, less water is required to excrete -​ Uric acid: in insects, land snails, many reptiles, birds -​ It is insoluble in water -​ Secreted as paste  -​ More energetically expensive then urea -​ Excretory systems: regulate solute movement between internal fluids and external environment -​ Key function of excretory system: -​ 1. Filtration -​ 2. Reabsorption -​ 3. Secretion (adding toxins and other solutes) -​ 4. Excretion (removing filtrates from system) -​ Systems -​ Protonephridia: -​ Network of dead-end tubules connected to external openings -​ Smallest branches of the network are capped by a cellular unit called a flame bulb -​ Tubules excrete a dilute fluid and function in osmoregulation -​ Metanephridia: ​ -​ Each segment of an earthworm has a pair of open-ended metanephirdia -​ Both excretory and osmoregulatory functions -​ Consists of tubules that collect coelomic fluid and produce dilute urine for excretion -​ Malpighian Tubules: -​ In insects and other terrestrial arthropods -​ Remove nitrogenoud waste from hemolymph and function in osmoregulation -​ Open into digestive tract -​ Highly efficient in water conservation -​ Insects produce dry waste -​ Kidneys -​ Excretory organ of vertebrates -​ Used in osmoregulation -​ Paired kidneys -​ Principle sight of waterbalance and salt regulation -​ They are supplied blood form the renal artery which is drained by the renal vein -​ Ureter: urine exites the kindry through this duct -​ Urethra: both ureters drain into the bladder and then urine is expelled through the urethra -​ Nephlon: functional unit of the vertebrate kidney -​ Made up of lung tubules and and a ball of capillaries called the glomerulus -​ Bowmans Capsule: surorunds and receives filtrate from the glomerulus capillaries -​ Filtration: occurs as blood pressure forces fluid from the blood in teh gomerulus to the lumen of the Bowmans capsule  -​ Filtration is non-selective (allows most small molecules to pass), including salt, glucose, amino acids, vitamens and nitrogenous waste -​ Pathway of Filtrate -​ Bowmans capsule to proximal tubules to loop of Henle to distal tubule -​ Fluid from several nephrons flows to the collecting duct to the renal pelvis to the ureter -​ Vasa recta: capillaries that serve the loop of henle -​ The vasca recta and loop of henle function as a countercurrent system -​ The mammalian kidney conserves water by producing urine that is much more concentrated than body fluids -​ Proximal Tubule: -​ Reabsorpton of ions, water and nutrients -​ Molecules are transported actively and passively from filtrate into intestinal fluid and then capillaries -​ Some toxic materials are secreted into the filtrate -​ Filtrate volume decreases -​ Descending Loop of Henle -​ Reabsorption of water continues through channels formed by aquaporin proteins -​ Movement is driven by high osmolarity of interstitial fluid which is hyperosmotic to the filtrate -​ Filtrate becomes increasingly concentrated -​ Ascending Loop of Henle -​ Salt but not water diffuses from tubule into the interstitial fluid -​ Filtrate becomes increasingly dilute -​ Distal Tubule: -​ Regulates K+ and NaCl concentratios of body fluids -​ Collecting Duct: -​ Carries filtrate through medulla to renal pelvis -​ Water is lost as well as some salt and urea -​ Filtrate becomes more concentrated -​ Urine is hypoosmotic to body fluids -​ Human kidneys process around 170 liters of filta​ -​ 99% of water, sugar, amino acids and vitamins are reabsorbed -​ Juxtamedullary nephron: -​ Contributes to water concentration in terrestrial animals -​ Mamalas that live in dry environments have long loops of henle -​ Birds have shorter loops of henle -​ They excrete uric acid instead of urea -​ Reptiles have only cortical nephrons but excrete nitrogneous waste as uric acid Nervous System -​ The nervous system is the command and control center -​ It has three functions -​ 1. Sensory input -​ 2. Integration -​ 3. Motor output -​ Sensory information is sent to the brain where it is processed -​ Motor output leaves the brain or ganglia via motor neurons -​ Neurons: nerve cells that transfer information within the body -​ Most neurons have dendrites which are highly branched extensions that receive signals from other neurons -​ Most of neurons cells are in the cell body -​ Most neurons are nourished or insulated by cells called glia -​ Ganglia: a simple cluster of neurons -​ Axon: a longer extension that transmits signals from its terminal branches to other cells at synapses -​ Messages are transmitted as changes in membrane potential -​ Resting potential: membrane potential of a neuron when not sending signals -​ Ion pumps and ion channels maintain the resting potential of a neuron -​ At resting potential K+ is greater inside the cell and Na+ is greater outside the cell -​ At resting potential many K+ channels are open, fewer Na+ channels are open -​ The opening of ion channels in the plasma membrane converts chemical potential to electrical potential -​ Resting neuron: the currents of K+ and Na+ are equal and opposite and the resting potential is steady -​ Formation of Action Potential: -​ Resting state to depolarization to rising phase of action potential to falling phase of action potential to undershoot -​ refractory period: temporary inactivation of Na+ channels -​ During the refractory period after an action potential a second action potential can’t be initiated -​ This ensures that an impulse moves along the axon in one direction only -​ They travel towards synaptic terminals -​ Action potentials can travel long distances by regenerating itself along the axon -​ Myelin sheath: -​ Insulation in vertebrate axons -​ Increase speed -​ The insulation increases diameter which means that there is a greater action potential speed -​ The myelin sheath is made by glia -​ Oligendrocytes in the CNS -​ Scwann cells in the PNS  -​ Nodes of Ranvier: gaps between scwann cells in myelin sheath where voltage gated Na+ channels are found and where action potentials are formed -​ Salatory conduction: when an action potential jumps between nodes of ranvier -​ Synapse: -​ A junction between cells controlling communication -​ Where neurons communicate -​ Electrical synapse -​ Electrical current flow from one neuron to another -​ Chemical synapse -​ A chemical neurotransmitter carries info -​ Majority of synapses -​ In chemical synapses the presynaptic neuron synthesizes and packages the neurotransmitter in synaptic vesicles located in the synaptic terminal -​ Action potential causes the release of the neurotransmitter -​ Neurotransmitter diffuses across the synaptic cleft and is received by the postsynaptic cell -​ Neurotransmitter binding causes ion channels to open generating a postsynaptic potential -​ After release the neurotransmitter may… -​ Diffuse out of the synaptic cleft -​ Be taken up by surrounding cells -​ Or be degraded with enzymes -​ Direct synaptic transmission: binding of neurotransmitters to ligand-gated ion channels in the postsynaptic cell -​ Information is transferred from a presynaptic cell (neuron) to a postsynaptic cell (neruon, muscle or gland cell) -​ Cnidarians -​ Simplest animals with nervous system -​ Have a nerve net -​ Nerve set: series of interconnected nerve cells, no central pathway or directional organization -​ Starfish -​ Have a nerve net in each arm connected by radial nerves to a central nerve ring -​ Nervous system: consists of neurons and supporting cells -​ Cepharlizatoin: the clustering of sensory organs at the front end of the body -​ Bilaterally symmetrical animas have cephalization -​ Relatively simple cephalized animals ex. Flat worms, have a central nervous system -​ The central nervous system consists of a brain and longitudinal nerve cords -​ Vertebrates -​ The CNS is a brain and spinal cord​ -​ The CNS integrates information -​ The brain and spinal cord have…  -​ Gray matter: consists of neuron cell bodies, dendrites, and unmyelated axons -​ White matter: consists of bundles of myelinated axons -​ The peripheral nervous system is composed fo nerves and ganglia -​ It brings information into and out of the central nervous system -​ Regulates movement and internal environment -​ The PNS has two functional components -​ Motor system: carries signals to skeletal muscles (this is voluntary) -​ Autonomic nervous system: regulates internal environment in an involuntary manor -​ Made up of enteric divisions, parasympathetic and sympathetic -​ Parasympathetic and sympathetic have an antagonistic effect on organs -​ Afferent neurons: transfer info to the CNS -​ Efferent neurons: transmit information away from CNS -​ Reflex: bodies automatic response to a stimulus -​ Cranial nerves: orgiginate in brain and moslty terminate in organs of head and upper body -​ Spinal nerves: originate in spinal cord adn extend to parts of body below the head -​ Brain -​ Vertebrate brain is regionally specialized -​ Brainstem coordinates and conducts info between brain centers -​ Midbrain: contains centers for receipt adn integration of sensory information -​ Pons: regulates breathing centers in the medulla -​ Medulla oblongata: controls breathing, cardiovascular activity, swallowing, vomiting and digestion -​ Cerebellum: important for coordination and error checking during motor, perceptual and cognitive functions also important in learning and remembering motor skills -​ Embryonic dencephalon has 3 regions -​ 1. Epitahlamus: includes pineal glad and generates cerebrospinal fluid from blood -​ 2. Thalamus: main input cetner for sensory information to the cerebrum and main output center for motor information leaved the cerebrum -​ 3. Hypothalamus: regulates homeostasis and basic survival behaviors such as flight vs fight -​ Cerebrum: has righ and left cerebral hemispheres -​ Consists of cerebral cortex (gray matter overlying white matter and basal nuclei)  -​ The cerebral cortex is the largest and most complex part of the brain -​ It controls voluntary movement and cognitive function -​ Each side has four lobes: frontal, temporal, occipital and parietal -​ Each lobe contains primary sensory areas and association areas where information is integrated -​ A thick band of axons called the corpus callosum provided communication between right and left cerebral cortices -​ Right controls left side and vice versa -​ Limbic system: where emotions are generated and experienced -​ It is a ring of structures around the brainstem and includes the amygldala, hippocampus and thalamus -​ The amygdala is located in the temporal lobe and helps store an emotional experience as an emotional memory -​ Memory and learning -​ Occurs when neurons make new connections or the strength of existing neural connections change -​ Short term memory is accessed through the hippocampus -​ The hippocampus also ahs a role in long term memory which is stored in the cerebral cortex Endocrine System: -​ Animals respond to environmental, behavioral, and physiological cues -​ The function of the endocrine system is the production and regulation of chemical substances called hormones -​ Pheromones: external signalling molecules: -​ Three Major classes of Hormones -​ 1. Polypeptides (includes insulin, they are water soluble) -​ 2. Amines (includes thyroxine and epinephrine, they are water soluble) -​ 3. Steroids (includes cortisol, they are lipid soluble) -​ Water soluble hormones cannot diffuse through the plasma membranes of target cells. They bind to cell-surface receptors and induce changes in cytoplasmic molecules and sometimes alter gene-transcription -​ Lipid soluble hormones: diffused out across the membranes of endocrine cells, they bind to transport porteins in the blood then diffused into the target cells adn bind to receptors in the cytoplasm or nucleus, they trigger gene transcription -​ Some hormones can induce multiple effects -​ Endocrine cells are grouped in ductless organs called endocrine glands and they secrete hormones directly into the surrounding fluid -​ Exocrine glands: have ducts -​ Hormones can also be made in organs  -​ Neuroendocrine: endocrine and nervous system work together to maintain homeostasis -​ Hypothalamus: collection of specialized cells located in the brain and is the primary link between the nervous and endocrine system. It stimulates or suppresses hormone secretions of pituitary gland -​ Hormone secretion is controlled through feedback -​ Negative: endocrine cells respond to an internal or environmental stimulus by secreting a hormone. The hormone travels to the target cell where it interacts with the specific recepotro to bring about a physiological response -​ negative feedback helps restore a pre-existing state -​ Positive: feedback where continued stimulation causes an increase in the secretion of the hormone. It amplifies both the stimulus and the response -​ Vertebrates -​ Have a hypothalamus -​ pituitary gland -​ Posterior pituitary -​ Anterior pituitary (releasing and inhibiting hormones) -​ Antidiuretic hormone -​ Hormone cascade pathway -​ Hypothalamus to anterior pituitary to largest endocrine gland to target tissue -​ What stimulates endocrine glands to secrete hormones? -​ Blood concentrations of non-hormone chemicals -​ Another hormone -​ Neural stimuli -​ Evolution of hormone function -​ Mammals: growth of mamary glands and milk production -​ Birds: regulate fat metabolism and reproduction -​ Amphibians: delay metamorphisis -​ Freshwater Fish: regulates salt and water balance Digestion: -​ Nutritional needs -​ Fuel for all animals requirements -​ Biosynthesis: making new molecules -​ Essential nutrients CANT be synthesized -​ Stages of food Processing -​ 1. Ingestion (mechanical digestion) -​ 2. Digestion (chemical digestion - enzymatic hydrolysis) -​ 3. Absorption (nutrient molecules enter body cells) -​ 4. Elimination (undigested material) -​ Digestion can be intracellular or extracellular -​ Extracellular digestion occurs in a specific compartment to avoid self-digestion -​ Intracellular digestion is called endocytosis -​ Animals with a simple body plan -​ Have a gastrovascular cavity  -​ The cavity digests food and distributes nutrients -​ Digestion begins in the cavity (gastrodermis secretes enzymes) -​ Porifera/Cnidaria -​ Minaly have intracellular digestion -​ Have one hole for mouth and anus -​ Most animals have a digestive tube with two openings and a complete digestive tract or alimentary canal -​ A digestive tract is a type of extracellular digestion -​ Having two openings allows for one directional movement of food, this allows for specialized compartments -​ Alimentary canal: also known as the GI tract is a long tube of organs that run from the mouth to the anus -​ Humans -​ Oral cavity, pharynx esophagus digestes carbohydrates -​ Stomach digests proteins -​ Lumen of small intestine, carbohydrate, nucleic acids and fat digestion -​ Epithelium of small intesting, digests carbohydrates, proteins and nuceic acids -​ Movement of Food -​ Oral cavity to esophogus to stomach -​ Bolus: salivary amylase + mucin + food -​ Peristalisis: involuntary contractions that move food from esophagus to stomach -​ When you’re eating the epiglottis convers the glottis which prevents food from entering the trachea -​ Stomach -​ The interior surface is highly folded and dotted with pites leading into the tubular gastric glands -​ Gastric glands: have three types of cells that secrete different components of gastric juice -​ 1. Mucus cells which lubricates and protects cells lining the stomach -​ 2. Chief cells secrete pepsinogen which is an inactive form of the digestive enzyme pepsin -​ 3. parietal cells secrete hydrochloric acid (HCL) -​ If there isn’t sufficient mucus you can get an ulcer -​ Chyme: gasric juices and partially digested food -​ Heartburn: backflow of acid chyme through cardiac orifice -​ Pyloric sphincter: regulates passage of chyme to small intestine -​ Duodenum: first part of intestines, enzymes secreted from pancreas -​ Accessory glands -​ Salivary glands -​ Gallbladder -​ Liver -​ Produces bile that is stored in the gallbladder  -​ Bile: made up of bile salts (act as emulsifies) and pigments (from destruction of red blood cells) -​ Pancreas -​ Produces proteases, amylases, lipases, nucleases, bicarbonate -​ Activated by trypsin -​ Both endocrine and exocrine functions -​ Endocrine: acts on distant cells via the circulatory system ex. Secretion of insulin -​ Exocrine: acts via ducts or channels rather than blood -​ Hormonal Control of Digestion -​ Cholecysokinin: stimulates release of digestive enzymes -​ Enterogastrone: inhibits peristasis and acid secretion by stomach -​ Gasterin: stimulates production of gastric juices -​ Secretin: stimulates the pancreas to rlease sodium bicarbonate -​ Small intestine: where nutrients are absorbed -​ Large intestine (colon) -​ Runs from small intestine to the rectum -​ 1.5 m long -​ Appendix has a defense role -​ Reabsorption of water -​ Has a rich microflora that produce vitamins reabsorbed by the large intestine -​ Production of feces -​ Salivary amylase hydrolyzes starch and glycogen -​ Pepsiongen is the inactive form of pepsin -​ Cecum -​ Most mammal herbivores have a cecum -​ Cecum hostess a large number of bacteria that aid in the enzymatic breakdown of plant materials like cellulose -​ In carnivores there is a reduced cecum that is partially or wholly replaced by the appendix -​ Microbiome -​ 500-1000 microbial species in the human gut -​ Commensal bacteria: convert dietary fiber to short chain fatty acids -​ Microbial composition affects anxiety level, obesity and memory in mice -​ Gut Microflora affected by… -​ Antibiotics -​ Fermented food -​ Feacal transplants Respiration: -​ Cellular respiration is a set of metabolic reactions and processes that take place in the cells of an organism to convert biochemical energy from nutrients into ATP and then release waste -​ Gas exchange: supplies oxygen for cellular respiration and disposes fo CO2 -​ Respiratory Organs -​ Flatwrom (body wall) -​ Fish (gills) -​ Terrestrial arthropod (trachea) -​ Mammal (lung) -​ Protozoa/Single-celled organisms -​ Gas transfer occurs across plasma membrane by diffusion -​ This process also happens in small invertebrates -​ In specialized organs there are normally extensive patterns of invagination and evaginated structures to increase membrane surface area -​ Lungs are invaginated -​ Gills are evaginated -​ Starfish: breathe with tube feet as gills (called branchail papulae) -​ Fish: used gills. In the gills gas is exchanged through countercurrent flow of blood and water. This allows for high intake, up to 80% -​ Insects: have a tracheal system -​ Tracheal system: tiny branching tubes that penetrate the body, air sacs are resevoirs for organs -​ Spiralces: small openings on insects body surface that air enters through then passes into smaller tubes called tracheoles -​ Tracheoles are closed and contain fluid -​ Gas-exchange surface is close to all cells -​ Circulatory system plays little to no role -​ Amphibians -​ Larval: use gill and skins -​ Some just breathe through their skin -​ Adults: lungs and skin -​ Some adults retain their gills -​ Birds: have rigid lungs that undergo little change in volume -​ Air flows uni-directionally -​ Gas exchange system is cross current -​ Have air sacs that expand and contract -​ Mammals: have lungs -​ Lungs are densely filled with branching airways made up of 23 levels and 300 million aveoli -​ Surface area of a lung in humans is equivalent to a tennis court -​ Thickness of barrier between blood and cells is only two layers -​ The layers are blood vessels and aveoli(air sacs) -​ Movement of Air -​ Buccal pressure: in air breathing fish and amphibians  -​ Suction or aspiration: nonavian reptiles, mammals and birds -​ Uses thoracic and abdominal muscles -​ Exchange of Respiratory Gases -​ Gas diffuses from high to low partial pressure -​ Respiratory Pigments -​ Needed to bind and transport gases because O2 has low solubility in water -​ Haemoglobin: is a protein that is a respiratory pigment in almost all vertebrates, contained in red blood cells -​ Reversibly binds O2 loading O2 in the lungs and unloading it to other parts of the body with lower partial pressure -​ The O2 binds to the iron atom in the heme group -​ Haemocyanin: the pigment in arthropods and molluscs -​ Humans -​ Before inhalation air pressure in lungs is equal to the air pressure outside the lungs -​ During inhalation volume of chest cavity and lungs expand, which reduces the air pressure in lungs allowing air to flow in -​ During exhalation the volume of the chest cavity decreases causing partial pressure to increase which forces air out -​ Tidal volume: amount of air that moves in and out of lungs in a single breath, 500 mL -​ Vital Capacity: maximum amount of air that a person can forcefully exhale from their lungs after taking the biggest breath possible, 3.4-4.8 L -​ Residual Volume: amount of air that remains in the lungs after a maximum exhalation, around 1.5 L Circulation: -​ Allows for exchange with the environment -​ Provides an internal transport system for O2, CO2, nutrients and waste -​ We need circulation because diffusion is inefficient -​ Three Basic Components -​ 1. A transport system (blood) -​ 2. A set of tubes (blood vessels) -​ 3. A muscular pump (heart -​ Open System -​ Blood may be only partially, or not at all confined to blood vessels -​ Insects most molluscs and arthropods -​ Closed system -​ More efficient in larger more active animals -​ Blood is confinded to blood vessels -​ Earthworms, squid, octopus and all vertebrates -​ Insects -​ As heart relaxes it draws haemoglymph into circulatory system through valved pores called ostia  -​ Vertebrate Cardiovascular system -​ Blood vessels: -​ Arteries: from heart to arterioles to capillaries -​ Veins: from venules to capillaries to heart -​ Capillaries: where exchange of gases and nutrients occur -​ Have a two to four chambered heart -​ Atria (singular atrium)/ auncles and ventricles -​ Fish -​ Singular circulation -​ A fish heart has two main chambers made up of one ventricle and one atrium -​ Blood pressure drops as it flows through the two capillary beds this limits the aerobic metabolic rate of fishes -​ Double Circulation -​ Blood flows through the heart twice per circuit -​ Cardiac Cycle -​ Systole: contraction phase -​ Diastole: relaxation phase -​ Cardiac output depends on… -​ Heart rate -​ Stroke volume (amount pumped by left ventricle per contraction) -​ The beat is maintained by sinoatrial (pacemaker) and atrioventricular nodes working in synchrony -​ Arteries: have thicker more elastic walls than veins to help maintain blood pressure between heart contractions -​ Capillaries: slow blood flow which allows exchange of gases and nutrients -​ 15% of blood fluid and proteins leak in lymphatic system and are returned near the right atrium -​ Muscle movement squeezes blood through veins -​ Medical conditions -​ Atherosclerosis: caused by buildup of low density lipoproteins within arteries -​ Hypertension: high blood pressure, promotes atherosclerosis and increases the risk of heart attack and stroke -​ Heart attack: death of cardiac muscle tissue, resulting from blockage of one or more coronary artieries often caused by a blood clot -​ Stroke: seath of nervous tissue in the brain visually resulting from rupture or lockage of arteries in the head -​ Blood: connective tissue that consists of cells (45% by volume) and plasma (90% water and solutes) -​ Haemogloblin in red blood cells brings oxygen from lungs into tissues Plant Physiology: -​ Plants biomass is 450 Gt out of approximately 550 Gt -​ Historically -​ Plants used for medicine…still used for medicine  -​ Phytochemicals (chemicals found in plants that can act as antioxidants, protect nutrients and protect the formation of carcinogens) -​ University of Padua: founded in 1545, oldest academic botanical garden -​ Dioscorides (50-70 AD) -​ Wrote a detailed pharmacological uses of plants -​ Most important reference until the late 1600s -​ Culpeper (1616-1654) -​ Wrote complete detailed pharmacological uses of plants -​ Still sued today -​ Modern -​ Increase food quantity/quality -​ To accommodate population growth and increased demands for food, production needs to double by 2050 -​ Materials (fibers/polymers) -​ Energy (oil, sugar, wood) -​ Biomimicry ex. Burrs inspire velcro -​ Bioremediation (fish waste is a resource for the growth of duckweed) -​ In the UK alone 1900 deaths were averted through absorption of air pollution in vegetation -​ Plants are important for dealing with issues like obesity, social isolation and mental health issues -​ They’re crucial components of ecosystems -​ Plant structure -​ Have a cell wall -​ DNA, proteins and lipids -​ Chlorplast (enable photosynthesis) -​ Amyloplast (produces, stores and breaks down starch) -​ Vacuole -​ Cell wall -​ Plsmodesmatea -​ Tissue structure (hisotoloy) -​ Tissues are groups of cells with same structure/function -​ Leaf -​ Cut section of a leaf: Cuticle to upper epidermis to palisade layer to spongy mesophyll to lower epidermis back to cuticle -​ Organs -​ Collection of tissues that together carry out a particular function -​ Organs in plants are roots, stems and leaves -​ Anatomy: organization of tissues and organs inside organism -​ Morphology: outward appearance ex. Shape and structure -​ Close interactions between structure and function -​ Nucleus (protect DNA) -​ Peroxisomes (oxidative metabolism) -​ Glyoxisomes (lipid metabolism)  -​ Leafs (large area to capture light) -​ Other than taxonomy and medicine we really only study plants to understand function -​ Theophrastus (300 BC) -​ Father of botany -​ Carl von Linne (1707-1778) -​ Start of binomial nomenclature “genus and species” -​ Plants that share an ancestor will share morphological features -​ Homology: when traits in different species exist as a result of an inherited (ancestral) genetic feature -​ Selective pressure: plants that have been exposed to the same selective pressures will share morphological features -​ Also called convergent evolution -​ Analogous traits: similarities between organisms not present in a common ancestor ex. Spikes on plants -​ Plasticity: the ability of an individual plant to adjust structure to local environment -​ More common in plants than animals because they are sessile and can’t move -​ There are more mosses than ferns than gymnosperms than angiosperms -​ Three types of plant tissue -​ Dermal tissue -​ Single layer -​ Epidermis -​ Vascular tissue -​ Xylem -​ Phloem -​ Ground tissue -​ Parenchyma -​ Totipotent: all cells can de-differentiate, divide and develop into completely new organisms -​ Plants cells can do this but not animal cells -​ This is a part of plant plasticity, nucleus from an adult cell can be transferred into an unfertilized occyte -​ Pluripotent: can develop into new tissues but not a whole new organism -​ A plant stem is pluripotent -​ Petals and sepals are leaves -​ Male stamen and female carpel are basically rolled up leaves -​ Leaves are used for photosynthesis and reproduction -​ Spines are types of leaves -​ Leaf structure -​ Guard cells, xylem, phloem, stoma, vein -​ Epidermis -​ The epidermis has a waxy cuticle, stomata and trichomes (hair) -​ Mesophyll -​ Palisade mesophyll -​ Spongy mesophyll  -​ Vascular system -​ Phloem (transport sugars) -​ Xylem (transfer water) -​ These are surrounded by a protective circle of cells called a bundle sheath -​ Stems -​ Carries leaves and positions them in the light -​ Controlling the stem length is a strategy -​ Plants have an evolutionary adaption to reach for light -​ Tubers, ginger and cactus all have modified stems -​ Phylloclade: photosynthetic stem -​ Stem structure -​ Apex bud with meristem (inhibits growth of axillary buds) -​ Node and internode -​ Axillary buds (mostly dormant, apical dominance) -​ axillary buds: sprouting axillary buds yield lateral shoots -​ Lateral shoots: carry secondary apex and dormant secondary axillary buds -​ If there is no apical dominance you get witches broom -​ Structure of Stem -​ The outside is the epidermis, then the cortex, then the vascular tissue (phloem outside and xylem inside), then the pirth -​ Fibers -​ Collenchyma: in young tissue, it is living and flexible -​ Sclerenchyma: in mature tissue, it is dead and righid -​ Sclerenchyma is used in linen and hemp -​ Roots: uptake of water, minerals, storage and photosynthesis -​ Roots can have nitrogen fixing nodules -​ Mycorrhiza: mutually beneficial network of plants and fungi -​ Tap root: one long thick root -​ Fibrous root: root with lots of extensions -​ Advnetitious: aerial roots (from stem) -​ Lateral roots: underground (from main root) often multicellular roots -​ Root Structure (listed from top to bottom of root) -​ Root hair zone (maturation…extension of epidermal cells-increase surface uptake) -​ Root elongation zone -​ Meristem (division zone) -​ Root cap (protection) -​ Endodermis (controls nutrient uptake) -​ Pericycle (can become meristematic, forms lateral root) -​ Photosynthesis can take place in leaves, stems (phylloclade) and roots -​ Leaves are the most common -​ Lateral shoots -​ These are pre-formed  -​ Branch that grows from the side of a plants stem (also known as axillary buds) -​ Located near surface stem (near vascular system) -​ Dormancy axillary buds -​ Later roots -​ These aren’t pre-formed -​ Located deep inside (near vascular system) -​ Growth -​ Primary growth (elongation from tip of roots and shoots) -​ Primarily driven by cell division -​ Cell division (mitosis) -​ Mitosis in meristems in root and stem apex and in axillary buds -​ Cell division in meristems yield initials (remain in meristem) and derivatives (will differentiate) -​ Meristems have embryonic cells -​ Cell enlargement -​ Indeterminate growth (stems and roots) -​ Determinate growth (leaves) -​ Determinate growth stops when an organism reaches a specific size -​ Annual: from germination to seed production within one year -​ Biennials: from germination to seed production in two years -​ Perennials: long lived species -​ Secondary growth (increasing thickness by adding vascular tissue) -​ Thickening of roots and shoots in woody plants -​ Development of secondary meristems -​ Vascular cambium (develops between xylem and phloem and is a cylinder of meristematic cells) -​ Vascular cambium produces new xylem and phloem. It is dormant during the winter and active during the summer -​ Spring formation large diameter xylem -​ Summer and autumn small diameter xylem -​ Cork cambium -​ Peridium: cork cambium and cork -​ Bark: phloem and peridem -​ Tree will survive removal of cork but removal of bark will kill it -​ This is because you are removing phloem, so you are lacking sugar transport -​ Tree Rings -​ Unique pattern depending on weather conditions -​ Old phloem disintegrates (don’t see it in rings) -​ Old xylem is non-functional (heartwood) -​ Because cells that make up xylem eventually die and can’t transport water  -​ Young xylem (sapwood) -​ Due to secondary growth the epidermis ruptures -​ Cork cambium produces cork cells -​ Cork cells are covered by waxy suberin Photosynthesis: -​ Autotrophs (primary producers): use inorganic forms of carbon require and external energy source to reduce carbon dioxide into organic carbon -​ Can convert abiotic sources of energy into energy stored in organic compounds -​ Heterotrophs (consumers): require a supply of organic carbon (sugar) and depend on dead or living biological matter -​ Cannot produce their own food -​ Plants are normally autotrophs but can be heterotrophs if they are parasitic plants -​ Animals can sometimes be autotrophs -​ Kleptoplasty: an animal takes chloroplasts from a food source and incorporates these into tissues of their own digestive tracts -​ This is also considered partial endosymbiosis -​ Photo-autotrophs: use light energy -​ Chemo-autotrophs: use chemical energy -​ Photosynthesis: light energy into chemical energy -​ Requires the use of chloroplasts -​ Chloroplasts have an outer and inner membrane, stroma (aqueous space), thylakoid, and granum (stack of thylakoids) -​ The origin of chloroplasts is though to have come from a heterotrophic host cell absorbing a unicellular organism that could photosynthesize -​ That is why chloroplasts have a double membrane -​ Chloroplast -​ Have a double membrane -​ Have their own DNA (ctDNA) -​ Internal lumen -​ Chlorophyll -​ Chlorophyll are located on thylakoid membranes -​ People used to think soils was the source of biomass -​ Van Helmont questioned and disproved this -​ Joseph Priestly: realized plants need oxygen -​ Chlorophyll -​ Absorbs photon, chlorophyll becomes excited, then chlorophyll falls back to ground state, energy is released as heat or fluorescence -​ This light energy is captured and converted to chemical energy (PHOTOSYNTHESIS!) -​ Light energy + 6CO2 + 6H2O = C6H12O6 + 6O2 -​ Photosynthesis -​ Light reactions: conversion of light energy into chemical energy (ATP and NADPH)  -​ Dark reactions: incorporation of CO2 into sugars with energy produced in light reactions -​ Light Reactions -​ Redox process (reduction oxidation) -​ Transfer of electron from donor (water) to an acceptor molecule with a lower redox potential -​ This process is driven by energy from absorbed photons of light -​ Photosystem I and photosystem II are the pumps that drive photosynthesis -​ They function sequentially -​ The photosystems have a reaction center of chlorophyll that catalyzes a charge separation, chlorophyll is organized as light harvesting complexes (called antennae) that capture photons. There is also a primary electron acceptor -​ PSII -​ 1. Charge seperation -​ 2. Transfer electron to primary electron acceptor and onwards to PSI -​ 3. Re-reduction of PSII by electron from water -​ PSI -​ 1. Charge separation -​ 2. Transfer electron to primary electron acceptor and on to NADP+ -​ 3. Re-reduction of PSI by electron from PSII -​ Product 1: NADPH (reducting energy…energy+electrons) -​ Water splitting: 2H2O = 4H+ + O2 + 4e- -​ ATP synthesis -​ Energy stores as an H+ gradient -​ Gradient is used to drive ATP synthesis by ATP synthase -​ Chemiosmosis: movement of protons across a selectively permeable membrane and against an electrochemical gradient -​ Chemiosmosis drive photophosphorylation -​ Product 2: ADP+ P =ATP -​ Used along with NADPH to produce sugars -​ Speed of the calvin cycle depends on light reactions -​ Dark Reactions (Calvin Cycle) -​ Incorporation of CO2 into sugar from energy in light reactions (ATP and NADPH) -​ Phase 1: carbon fixation -​ CO2 linked to ribulose biphosphate (enzyme for this is ribulose biphosphate carboxylase) -​ C5 + C = unstable C6 = 2C3 -​ Phase 2: phosphorylation and reduction -​ C3 are phosphorylated used ATP -​ C3 reduced by NADPH -​ Production of C3 sugar can be converted into glucose (C6H12O6) and other sugars -​ Phase 3: regeneration of acceptor molecule ribulose biphosphate -​ 5C3s are combined to give 3C5s  -​ Results in recycling of carbon skeleton that can incorporate CO2 -​ Lower levels of CO2 in atmosphere than 600 million years ago -​ Still lots of issues with climate change -​ C4 -​ Adaptations that increase CO2 leaf concentrations without increases transpiration -​ Adaptations gather all available CO2 in a small group of cells -​ Calvin cycle is prefaced with the C4-cycle -​ There are bundle sheaths that fixate Co2 through the calvin cycle -​ Rest of mesophyll collects CO2 and transports it as C4 to bundle sheath -​ Co2 bound to phosphoeholpyruvate-carboxylase -​ PEP and PEPC (can operate at a very low CO2 and has a large attachment) -​ 1. C3 + CO2 = C4 -​ 2. C4 is transported to bundle sheath -​ 3. CO2 is released in bundle sheath -​ 4. C3 is returned to mesophyll cycle -​ Most C4 plants are in hot dry areas ex.. maize , sugarcane and millet -​ CAM -​ Crassuleceae-family acid metabolism -​ C4 acids accumulate during night in vacuoles -​ CO2 is taken in during the day -​ Decreases water loss during hot/dry day -​ Temporal rather than spatial separation of C3 and C4 cycles -​ Are adapted to low CO2 levels -​ Are heat and drought adapted -​ Mitochondrial respiration: photosynthesis is reverse, cellular respiration converts the chemical energy contained in complex molecules -​ Mitochondrial respiration is shared in plants and animals -​ SUGAR INTO ATP -​ aerobic respiration in mitochondria requires O2 -​ Sugar + O2 = CO2 + ATP +H2O -​ Fermentation: a form of anaerobic respiration -​ Not in mitochondria and less efficient -​ Stages in Respiration -​ 1. Glycolysis (sugar splitting) -​ Breakdown of C6 sugar into 2C3 pyruvate molecules -​ Produces net 2ATP and 2NADH per glucose -​ 2. Citric Acid Cycle (krebs cycle) -​ Releases CO2 -​ Breakdown of pyruvate into CO2 -​ Produces net 2 ATP, 6 NADH and 2 FADH2 per glucose -​ 3. Oxidative Phosphorylation and Electron Transport -​ Use of electron transport to oxidize NADH and FADH2 to form H2O from O2  -​ Produces net 26-28 ATP per glucose -​ Aerobic Respiration -​ Takes place in mitochondria (except glycolysis) -​ Present in most eukaryotes as well as many prokaryotes -​ Conserved mechanism across widely different groups of organisms Plant Nutriton and Transport: -​ Photoautotrophs need… -​ Light energy -​ Water -​ Mineral nutrients -​ CO2 -​ Stomata connect atmosphere with intracellular space -​ Stomata are in the epidermis allow for gas exchange -​ Stomata -​ About 90% plant water loss through stomata -​ Only make up 1-2% of leaf surface -​ Turgor: full of water -​ Wilting: empty of water -​ Transpiration -​ Transpiration keeps plant cool -​ Cooling prevents cellular damage to proteins, lipid, DNA -​ Transport route is from shoot to shoot -​ It is important to balance transpiration vs. CO2 uptake -​ Things that help that… -​ Environmental plasticity -​ high stomatal density of plants grown in high light -​ Genetic adaptations -​ C4 photosynthesis -​ CAM photosynthesis -​ Stomatal Regulation -​ Swelling guard cells = opening stoma -​ Shrinking guard cells = closing stoma -​ Swelling and shrinking is due to water uptake/loss -​ Proton pumps create change in membrane potential -​ Potential drives K+ uptake/release -​ Passive uptake through aquaporins (channels) in membranes -​ Stoma mostly closed in dark -​ Regulated by circadian clock -​ Stoma open when internal CO2 is low -​ “Need” more CO2 -​ Stoma close when turgor leaf decrease -​ Because of too much water loss -​ Don’t know much about stoma response to climate change -​ Chemiosmostics: leaf movements -​ Plants can have memory: in a venus fly trap, sensory hairs need to be triggered twice in twenty seconds for the trap to close -​ Mineral Nutrients -​ Chemical elements absorbed from soil as inorganic ions -​ These are necessary to complete life cycle if “essential elements” -​ Many minerals present in plants both essential and and non-essential -​ 80-90% of plants fresh weight is water -​ 96% of dry weight is organic material -​ 4% is inorganic material -​ Essential Nutrients -​ Micronutrients: carbon, oxygen, hydrogen, nitrogen, phosphorus, and sulfur -​ Macronutrients: chlorine, iron, manganese, boron, zinc, copper, and nickel -​ Too little: deficiency -​ Too much: toxicity -​ Food Fortificaton -​ ⅓ of the rold at risk for zinc deficiency -​ 800,000 people die annually -​ Controlling mineral uptake is important for everyone -​ Nutrient Uptake by Roots -​ Absorption of Nutrients in Root Hair ZOne -​ Extensions of epidermal cells -​ Have a large surface area and a permeable epidermis -​ Mycorrhizae -​ Symbiotic structure made of plant roots and fungal hyphae -​ Have a large surface area -​ Fungi can be used to improve the quality of degraded soils -​ Apoplast: continuum formed by extracellular spaces in matrix of cells -​ Chemical composition of apoplastic fluids reflects soil -​ Apoplastic route blocked at endodermis -​ Symplast: continuum of cytoplasm connected by plasmdesmata -​ Selective absorption of nutrients through membrane -​ Root hair and cortex cells all absorb nutrients from apoplastic fluid (large absorption area) -​ Selective Uptake into Symplast -​ Channels selectively enable ions to cross membranes into cells -​ Membrane potential is the driving force (uses ATP) -​ The inside of the cell is more negative than the outside -​ Uptake cations driven by membrane potential -​ Uptake is enabled by channels -​ Cotransport: driven by membrane potential -​ Channels: create a hydrophilic channel through the cell membrane facilitationg the transport of moleculeds down and electrochemical gradient -​ Rate of nutrient uptake through channels matter -​ Endodermis: has a selective passage called the casparian strip -​ This is a belt of waxy material -​ It is in the cell walls of endodermal cells -​ Blocks the apoplastic route -​ Forces water and nutrients through symplast -​ All of this results in selective uptake -​ Stele: tissue inwards from endodermis -​ It is crucial for supporting plant and transporting water adn nutrients from roots to leaves -​ There are high levels of salt in the stele and low levels in the cortex -​ Root pressure accumulates salt (active process, costs ATP) -​ Flow of water is passive -​ Xylem: transports water -​ Root pressure (upward push) and transpirational pull bring water up -​ Root pressure is created by osmotic forces -​ Xylem forms the continuum and is dead when functional -​ Guttation: root pressure pushes excess water out through leaves -​ Transpirational pull -​ Creates negative pressure (negative water potential) -​ Cohesion of water molecules transmits pull from leaves to root -​ Hydrogen bond -​ Requires uninterrupted chain of water -​ Phloem: sugar, amino acids and protein transport -​ The main sugar is sucrose -​ Direction of phloem transport is variable -​ Flows from source to sink -​ Source: where sugar is produced (photosynthesis, conservation of starch) -​ Sink: where sugar is consumed (respiration, starch) -​ Phloem Structure -​ Has a sieve tube member (for transport, aligned, connected by sieve plate, are alive, no nucleus in sieve tube member/ribosomes) -​ A nucleus -​ A companion cell (where the nucleus is) -​ Linked through the plasmodesmata -​ Sieve plate -​ Transport in phloem is chemiosmotic cotransport of sugars and proteins -​ Mechanism -​ At source: sugar accumulates in sieve tube -​ High concentrations against sucrose gradient -​ Active costs ATP -​ Passive uptake of water (osmotic) -​ Generates positive pressure -​ At sink: sugar removed from sieve tube  -​ Sugar metabolized (ATP/NADPH) -​ Sugar converted to starch -​ Sugar can be used to synthesize cellulose -​ Passive loss water (osmotic) -​ Decrease in pressure -​ Crop yields limited by photosynthesis and capacity to transport sugars out of leaf Plant Hormones: -​ Hormones control plant growth and development -​ Growth: increase in size or weight -​ Development: progression in life cycle -​ Hormones are essential for all multicellular organisms -​ Sessile organisms must adapt to their environment, plants paly a huge role in this -​ Hormones… -​ Produced by multicellular organisms -​ Internal chemical signals -​ Present in minute amounts -​ Travel through organism -​ Coordinate metabolic activities and environment responses -​ HORMONES IN PLANTS ARENT PRODUCED IN GLANDS -​ Steps -​ 1. Reception -​ 2. Transduction -​ 3. Response (activation of cellular responses) -​ Reception -​ Specific receptor for each specific type of hormone -​ Located in cell membrane -​ Present in very low concentrations -​ Identifying receptors can be hard -​ It is easier to identify using genetic approaches -​ Transduction -​ Secondary messengers connect recept with response system -​ Transduce and amplify hormone signals -​ Ex. ca-fluxes, cGMP, phosphorylation -​ Cell Response -​ Altered transcription of specific genes -​ Transcriptional regulation -​ Altered activity enzymes -​ Post translational regulation -​ Environmental factors can alter hormone biosynthesis, transport, perception, conjugation to sugars and degradation -​ Five Main Classes of Hormones -​ Auxin (stimulate cell expansion) -​ Gibberellin (stimulate cell expansion)  -​ Cytokinin (stimulate cell division) -​ ALL ARE GROWTH PROMOTERS -​ Abscisic acid (slows growth) -​ Ethylene (controls ripening and cell death) -​ ALL GROWTH INHIBITORS -​ Many responses are controlled by multiple hormones -​ Life Cycle - Apical Dominance -​ Apex blocks growth axillary buds -​ Important aspect for competition of light -​ Auxin (generic name for chemicals with auxin-like activity) -​ Produced in apex and young leaves and embryos -​ Blocks growth axillary buds lower on stem -​ Responsible for apical dominance -​ Indole Acetic Acid (IAA) main natural auxin -​ Used in weed killer -​ Travels down to roots -​ Promotes formation of lateral roots -​ Commercially used as rooting powder -​ Cytokinin -​ Mostly produced in root tip and embryos -​ Zeatin: most common type -​ Travels from root to shoots -​ Anti-ageing -​ Promotes cell division -​ Enhances sprouting axillary buds (branching) -​ An extensive shoot system will produce lots of auxin encouragin root growth -​ An extensive root system will produce lots of cytokinin encouraging shoot growth -​ Together they control balance between root and shoot -​ Auxin and gibberellin produced in embryo stimulate growth of fruti -​ flower/young fruit will be shed if there is no viable, hormone producing embryo -​ Seedless fruits: either treated with synthetic auxin/gibberellin or a genetic mutant -​ Seed Development -​ 1. High levels of gibberellic acid promotes embryo growth -​ 2. High level of absisic acid facilitate embryo dormancy -​ Cotyledon: embryonic leaves -​ Plume: first ture leaves -​ Hypocotyl: stem below attachment point of cotyledons -​ Radicle: embryonic root -​ In initial stage of development theres high levels of giberellic acid (stimulates growth) and low levels of abscisic acid (don’t affect growth) -​ In the second stage (seed dormancy) ther are low levels of giberllic acid and high levels of abscisic acid (slows down metabolism) -​ Dormancy facilitates transport/survival  -​ In the third stage (germination) ther are low levels of abscisic acid and high levels of gibberellic acid (facilitate metabolism) -​ Balance between two hormones facilitates growth/dormancy -​ Fruit Ripening -​ Ethylene -​ Fruit switches from repelling to attracting (carefully timed) -​ Change in scent/color/softness -​ It is a positive cycle -​ Ethylene stimulates the fruit to ripen and the fruit ripening stimulates the production of ethylene -​ This is how fruits can make others ripen -​ Ethylene is a gas -​ Trade of fruit worldwide is possible by removing ethylene gas -​ Ethylene controls fruit ripening and flower aging -​ Keep fruits and flowers separate, can trigger ripening/aging -​ Ethylene also causes cell death -​ Apoptosis: programmed cell death -​ Ex.. xylem cells are dead when functional surrounding cells are alive -​ Leaf abscission (shedding leaf): involves local increase in ethylene and decrease in auxin -​ Not all plants display seasonal variation in hormone levels so not all shed their leaves​