Module 5

The maintenance of a stable equilibrium in the conditions inside the body

• Cell Body:
• nucleus
• cytoplasm with large amounts of endoplasmic raticulum and mitochondria ~ for production of neurotransmitters
• Dendrons:
• Transmit toward cell body
• Split into dendrites
• Axons:
• Transmit away from cell body

• Sensory: impulse from sensory receptor to relay or motor neurone, or brain
• Relay: transmit impulses between neurones.
• Motor: impulse from relay or sensory neurone to an effector ~ muscle or gland

• Myelin sheath
• Made of Schwann cells
• Nodes of Ranvier in between

• Specific yo certain type of stimulus
• Act as a transducer ~ convert stimulus to nerve impulse

• Pacinian Corpuscles 
• 

• 1. In resting state it has a resting potential since stretch-mediated sodium ion channels don't let Na⁺ through
• 2. Pressure applied changing shape of pacinian corpuscle, stretching membrane around neurone
• 3. Sodium ion channels widen and Na⁺ diffuses into neurone
• 4. Influx changes membrane potential ~ depolarised. Results in generator potential. 
• 5. Generator potential creates action potential, passing along neurone.

• Resting potential
• -70mV
• Outside is more positive than inside of axon

• Sodium-potassium pump
• 3 sodium ions pumped out
• 2 potassium ions pumped in
• Result: more Na⁺ outside and more K⁺ inside
• Potassium ions able to diffuse back out via potassium ion channels (down electrochemical gradient)
• Sodium ions (mainly) can't diffuse back in since gated sodium ion channels are shut
• Result: More positive ions outside cell, resting potential across membrane of -70mV

• Stimulus detected by sensory receptor
• Potential difference across membrane reversed
• +40mV

• 1. Polarised/Resting potenital: Most sodium ions kept out, sodium (Na⁺) voltage gated ion channels shut.
• 2. Depolarisation: Stimulus triggers some Na+ voltage gated ion channels to open, allowing Na+ ions in down electrochemical gradient. Inside becomes less negative.
• 3. Depolarisation: change in charge triggers more Na+ gated channels to open ~ positive feedback
• 4. Depolarised/Action Potential: Potential difference reaches +40mV voltage gated sodium ion channels close, potassium voltage gated ion channels open. 
• 5. Repolarisation: Potassium ions move out, reducing charge, resulting in inside becoming more negative than outside
• 6. Hyperpolarisation & Repolarised: Initially lots of potassium ions move out resulting in more negative than resting state. Voltage gated potassium channels now close. Sodium potassium pump then caused sodium to move out, potassium to move in, and it to return to resting potential

• Initial stimulus causes triggered action potential
• First region of axon depolarised
• Once sodium ions are inside the axon, they are attracted by negative charge ahead and concentration gradient ~ diffuse further along 
• Depolarisation triggered in next section

• Refractory period
• Voltage gated sodium ion channels remain closed ~ preventing movement of sodium ions into axon
• Prevents propagation of another action potential either backwards or forwards
• Ensures action potentials are unidirectional
• And occur as discrete impulses (don't overlap)

• Depolarisation can only occur at nodes of Ranvier where sodium ions can pass through channels
• Action potential can jump from node to node ~ Saltatory conduction
• More energy efficient since repolarisation requires ATP

• Axon diameter: bigger axon = faster
• - less resistance to flow of ions in cytoplasm
• Temperature: higher temp = faster
• - ions diffuse faster
• - up to 40°C

• Threshold value must be achieved in order to trigger action potential (which are always the same)
• Stimulus must be large enough to reach this value, or no action potential will occur
• A strong stimulus will produce more frequent action potentials

• Synaptic cleft - space between 
• Presynaptic neurone
• Postsynaptic neurone
• Synaptic knob - contains many mitochondria and endoplasmic reticulum for neurotransmitter production
• Synaptic vessicles - contain neurotransmitter released by exocytosis
• Neurotransmitter receptors on postsynaptic membrane

• Excitatory:
• Result in depolarisation in postsynaptic neurone
• If threshold is reached an action potential generated
• Acetylcholine
• Inhibitory
• Result in hyperpolarisation of postsynaptic neurone
• Prevents action potential
• GABA ~ gamma-aminobutyric acid

• 1. Action potential reaches end of presynaptic neurone
• 2. Depolarisation causes calcium ion channels to open
• 3. Calcium ions diffuse into knob
• 4. Causing vesicles to fuse with presynaptic membrane, releasing neurotransmitter into cleft
• 5. Neurotransmitter diffuses across cleft
• 6. Binds with receptors on postsynaptic membrane
• 7. Results in sodium ion channels opening
• 8. Sodium ions diffuse in
• 9. Action potential triggered & impulse propagated along axon
• 10. Any neurotransmitter left in cleft is removed

• Neurotransmitter: acetylcholine
• Hydrolysed by acetylcholinesterase, found also on postsynaptic membrane
• Forms choline & ethanoic acid
• Products take back to presynaptic knob to reform neurotransmitter using ATP

• Ensure unidirectional impulses~ neurotransmitter receptors only on one side
• Allow one impulse to go to multiple neurones via multiple synapses to create number of simultaneous responses
• Number of neurones can feed to one postsynaptic neurone to create one single result

• Released neurotransmiiter must build up in order to reach threshold in some synapses
• Spatial summation:
• -number of presynaptic neurones connect to one postsynaptic neurone
• -each release neurotransmitter which builds up
• Temporal summaton: 
• -single presynaptic neurone
• -releases neurotransmitter a number of times over short period before it builds up enough

• Central Nervous System (CNS) ~ brain & spinal cord
• Peripheral Nervous System (PNS) ~ neurones connecting CNS and rest of body

• Somatic ~ conscious control
• -input: sense organs
• -output: skeletal muscles
• Autonomic ~ subconscious 
• -works constantly
• -input: internal receptors
• -output: smooth muscles, glands, cardiac muscle
• -divided into sympathetic & parasympathetic nervous system

• Sympathetic:
• -generally speeds things up
• -'fight or flight'
• -noradrenaline
• -eg. increase in heart rate
• Parasympathetic:
• -generally slows things down
• -relaxing responses
• -acetycholine
• -eg. decrease in heart rate after activity

• Cerebrum
• Cerebellum
• Medulla oblongata
• Hypothalamus
• Pituitary gland

• Interprets sensory info wrt info stored from previous experiences
• Coordinates all voluntary responses ~ learning, memory, personality, conscious thought
• Some involuntary responses
• Highly convoluted ~ increased SA
• Split into left and right hemispheres
• Outer layer called cerebral cortex
• Sizes of sensory and motor areas proportional to function

• Controls unconscious functions such as posture, balance, and non-voluntary movement
• Does not initiate movement, but coordinates it
• Relays info to cerebral cortex for motor control
• Damaged ~ jerky movement

• Contains many important regulatory centres
• Control reflex activities such as ventilation and heart rate ~ (Autonomic control)
• Controls swallowing, peristalsis, coughing

• Main control region for autonomic nervous system
• Two centres - sympathetic and parasympathetic
• Controls behaviour patterns ~ feeding, sleeping, aggression
• Monitors blood plasma composition ~ water, glucose (has rich blood supply)
• Produces hormones
• Regulatory centre for temperature

• At base of hypothalamus
• Two sections:
• -Anterior pituitary (front) ~ six hormones including FSH
• -Posterior pituitary (back) ~ stores & releases hormones produced by hypothalamus, e.g. ADH

• Receptor
• Sensory Neurone
• CNS - Relay Neurone
• Motor Neurone
• Effector
• Response

• Tap below kneecap
• Leg normally extends once
• Tested by doctors
• Absence of reflex indicates nervous problems
• Multiple oscillation can indicate cerebellar disease

• Involuntary blinking of eyelids
• ~ Corneal reflex
• Cornea is stimulated
• Purpose- keep cornea safe
• ~Optical reflex
• Loud sounds and bright light
• Purpose - protect retina and lens
• Doctors test for blink reflex in unconscious patients
• -if present, lower brain stem is functioning so cannot be diagnosed as brain-dead

• Purpose: prevent or minimise harm to the body
• Prevents brain being overloaded since they are involuntary and brain is not involved
• Don't need to be learned 
• Fast reflex arc is short with only two synapses
• Everyday actions eg not falling over

• Skeletal: movement
• Cardiac: heart
• Smooth: involuntary, found in walls of hollow organs such as stomach, and blood vessels, digestive tract etc.

• Fibre appearance: striated
• Control: conscious
• Arrangement: regular so muscle contracts in one direction
• Contraction speed: fast
• Length of contraction: short
• Structure of fibres: tubular and multinucleated

• Fibre appearance: specialised striated
• Control: involuntary 
• Arrangement: cells branch & interconnect for simultaneous contraction
• Contraction speed: medium
• Length of contraction: medium
• Structure of fibres: fainter striations, branched, uninucleated

• Fibre appearance: non-striated
• Control: involuntary
• Arrangement: irregular, cells contract in different directions
• Contraction speed: slow
• Length of contraction: relatively long time
• Structure of fibres: spindle shaped, uninucleated

• Bundles of muscle fibres enclosed within plasma membrane ~ sarcolemma
• Longer than normal cells
• Many individual embryonic muscle cells fuse together:
• -makes them stronger
• Shared cytoplasm ~ sarcoplasm
• Sarcolemma folds inwards - to spread electrical impulses
• Many mitochondria
• Sarcoplasmic reticulum contains calcium ions throughout fibre

• Within muscle fibres
• Long cylindrical organelles
• Lie parallel
• Made of actin (thinner, two strands twisted together) and myosin (thicker filament, long rod shaped fibres with heads to one side)

• Alternating light and dark bands
• Light: region where actin & myosin filaments don't overlap (I-band)
• Dark: presence of thick myosin filaments, edges particularly dark where actin & myosin overlap (A-band)
• Z-line: centre of light band
• -distance between 2 Z-lines is one sarcomere 
• -shortens on contraction
• H-Zone: lighter region at centre of dark band
• -only myosin 
• -decreases on contraction

• Actin and Myosin filaments slide past eachother
• Sliding filament model

• Light band ~ narrower
• Z-lines ~ closer together
• H-zone ~ narrower
• 

• Globular heads, hinged allowing backward/forward movement
• Head has binding sites for actin & ATP
• Tails form the filament

• Binding sites for myosin heads ~ actin-myosin binding sites
• Resting State: blocked by tropomyosin held in place by protein troponin, cannot slide
• Contraction: actin-myosin cross bridges form
• -myosin heads flex
• -pulling actin filament along myosin filament
• -myosin detaches, head returns to original angle using ATP
• -myosin reattaches further along

• Many neurotransmitter junctions ~ ensure simultaneous contraction
• Motor unit ~ all muscle fibers supplied by one neurone, if strong force is needed many units are stimulated
• Action potential arrives
• Calcium ion channels open and ions move into knob
• Vesicles fuse to presynaptic membrane and release acetylcholine
• Diffuses across cleft & binds to receptors on postsynaptic membrane (sarcolemma) 
• Sodium ion channels open causing depolarisation
• Neurotransmitter broken down and recycled

• Depolarisation of sarcolemma travels into muscle via T-tubules in contact with sarcoplasmic reticulum
• Action potential stimulates release of calcium ions from sarcoplasmic reticulum (channels open)
• Calcium ions bind to troponin causing change in shape
• Pulls tropomyosin away leaving actin-myosin binding sites free
• Actin-myosin bridges form
• Myosin head flexes pulling actin filament along
• ADP bound to myosin head is released
• ATP molecule can now bind to myosin head
• -Causes head to detach from filament
• Calcium ions activate ATPase activity of myosin, hydrolysing ATP to ADP & phosphate
• -releases energy for myosin head to return to original position
• Cycle repeated for as long as muscle is stimulated

• Hydrolysis of ATP to ADP and phosphate
• Required for:
• -movement of myosin head
• -enable sarcoplasmic reticulum to actively reabsorb calcium ions from sarcoplasm

• Aerobic respiration:
• -regenerated from ADP by oxidative phosphorylation 
• -takes place inside mitochondria
• -requires oxygen
• -long periods of low intensity exercise
• Anaerobic respiration:
• -no oxygen
• -ATP made by glycolysis but pyruvate (also produced) is turned to lactate (lactic acid)
• -builds up resulting in muscle fatigue
• -short periods of high intensity exercise
• Creatine phosphate:
• -stored in muscle
• -acts as reserve supply of phosphate
• -available immediately to combine with ADP to form ATP
• -generates ATP rapidly
• -but store of phosphate quickly depleated
• -short bursts of vigorous exercise (e.g. tennis serve)
• -creatine phosphate stores replenished while relaxed

• Group of specialised cells
• Secrete chemicals ~ hormones
• Directly into bloodstream

• Secrete chemicals through ducts into organs or to surface of body
• e.g digestive

• Gland stimulated: change in blood concentration of a substance, or as the result of another hormone or nerve impulse
• Hormone secreted
• Diffuses out of blood
• Binds to specific receptors on/in target cells

• Steroid hormones: 
• -lipid soluble
• -bind to receptors inside target cell (cytoplasm or nucleus)
• -hormone-receptor complex acts as a transcription factor
• -facilitates or inhibits transcription of specific genes
• -e.g oestrogen 
• Non-steroid hormones:
• -hydrophilic
• -bind to receptors on target cell surface membrane
• -triggers cascade reaction mediated by second messengers
• -e.g adrenaline

• Located: top of each kidney
• Surrounded by caspule
• Adrenal cortex: outer region, hormones vital to life ~ e.g cortisol, adolsterone 
• Adrenal medulla: inner region, non-essential hormones ~ e.g adrenaline

• Glucocortinoids: including cortisol and corticosterone
• - cortisol regulates metabolism, regulated blood pressure and cardiovascular function in response to stress
• - corticosterone works with cortisol to regulate immune response, suppress inflammatory reactions
• - release controlled by hypothalamus
• Mineralocortinoids: aldolsterone 
• - helps control blood pressure by maintaining salt/water balance
• - release controlled by signals from kidney
• Androgens: small amounts of male & female sex hormones
• - important especially after menopause

• Released when sympathetic nervous system is stimulated ~ during stress
• Adrenaline: increases heart rate ~ blood to muscles & brain
• -raises blood glucose
• Noradrenaline: works with adrenaline
• -increased heart rate
• -widening pupils and airways
• -narrowing of blood vessels to non-essential organs ~ higher blood pressure

• Exocrine gland:
• -produces pancreatic juice
• -produces digestive enzymes ~ amylases, proteases (eg trypsin), lipases
• Endocrine gland:
• -produces insulin and glucagon
• -made by islets of Langerhans

• α cells (alpha) ~ produce and secrete glucagon
• -larger & more numerous
• β cells (beta) ~ produce and secrete insulin

Glycogenolysis

Glucogenesis

Glycogenesis 

• Released when blood glucose is too high
• Binds to receptors on cell surface membrane (on virtually all body cells)
• Opens glucose transport proteins ~ more glucose enters cells
• Activates enzymes in certain cells to convert glucose to glycogen
• Broken down by enzymes in liver ~ must be secreted constantly when needed
• Lowers blood glucose conc by:
• -inc rate of absorbtion
• -inc respiratory rate of cells
• -inc rate of glycogenesis 
• -inc rate of glucose to fat conversion
• -inhibiting release of glucagon

• Negative feedback
• -insulin drops below point
• -β cells reduce their secretion of insulin

• Released when blood glucose is too low
• Binds to receptors found only on liver and fat cells
• Raises blood glucose by:
• -glycogenolysis ~ liver breaks down glygocen into glucose and releases into blood
• -reduces amount of glucose absorbed by liver cells
• -gluconeogenesis ~ increasing conversion of amino acids and glycerol into glucose in the liver

• antagonistic
• ~ work against each other

The level of blood glucose is what determines the quantity of insulin and glucagon released.

• 1. Normal blood glucose levels: ATP-sensitive potassium channels open on plasma membrane of β cells.
• -potassium ions diffuse out
• -inside of cell -70mV potential (wrt outside of cell)
• 2. Blood glucose concentration rises: glucose enters β cell by glucose transporters
• 3. Glucose metabolised inside mitochondria ⇒ production of ATP
• 4. ATP binds to ATP-sensitive potassium channels causing them to close
• 5. Potential difference reduced to -30mV, depolarisation occurs
• 6. Depolarisation causes voltage gated calcium ion channels to open
• 7. Calcium ions enter cell and cause secretory vesicles to release insulin by exocytosis

• Type 1:
• -unable to produce insulin
• -β cells of Langerhans don't make it
• -cause unknown ~ no cure
• -possibly autoimmune attack on β cells
• -symptoms develop quickly
• Type 2:
• -β cells do not produce enough insulin
• -OR body does not respond to insulin as it should
• -caused by excess body weight, physical inactivity, excessive overeating of carbs.
• -symptoms develop slowly

• Type 1:
• -regular insulin injections ~ insulin dependent
• -regularly test body glucose
• -too much insulin can result in hypoglycaemia (very low blood glucose)
• -too little insulin can result in hyperglycaemia (very high BG) 
• -both can result in unconsciousness and death
• Type 2:
• -regulate carbs intake through diet
• -match to exercise levels
• -increase exercise
• -weight loss
• -drugs to stimulate insulin production
• -drugs to slow down glucose absorption  
• -insulin injections

• Originally from pancreas of cows and pigs
• -difficult & expensive
• -could cause allergic reactions
• Now from GM bacteria
• -pure human insulin
• -less likely to cause allergic reaction
• -produced in higher quantities
• -cheaper
• -overcomes religious and ethical concerns of using animal products

• Stem cell therapy
• -likely from embryos
• -alternatively using preserved umbilical cord stem cells
• Advantages to the treatment:
• -donor availablility wouldn't be an issue ~ stem cells would produce unlimited source of β cells
• -reduced likelihood of rejection
• -no longer need to inject insulin

• Body's response to potential danger, preparing it to run or fight
• Threat detected by autonomic nervous system
• Hypothalamus communicates with sympathetic nervous system and adrenal-cortical system
• Sympathetic NS sends impulses to glands and smooth muscle & tells adrenal medulla to release adrenaline & noradrenaline
• Adrenal cortex stimulated by hormone from pituitary gland to produce other hormones to help deal with threat

• Triggers liver cells to undergo glycogenolysis 
• -release glucose
• Second messenger model
• Binds to receptors on liver cell surface membrane
• Triggers chain of reactions inside cell:
• -activates adenyl cyclase (enzyme) 
• -which converts ATP to cyclic AMP (on inner surface membrane)
• -cAMP acts as second messenger
• -which activates other enzymes (protein kinases which phosphorylate, hence activating other enzymes) in order to convert glycogen to glucose

• Medulla oblongata
• -2 centres linked to SAN: (sino-atrial node)
• -one increases HR via impulses through sympathetic NS (accelerator nerve)
• -one decreases HR via impulses through parasympathetic NS (vagus nerve)
• -Receptors:
• baroreceptors:
• -blood pressure 
• -present in aorta, vena cava, carotid arteries
• chemoreceptors:
• -detect levels of particular chemicals in blood e.g. CO₂
• -present in aorta, carotid artery and medulla

• If CO₂ levels increase, pH decreases (becaue carbonic acid is formed when CO₂ and H₂O interact)
• When pH is low, response is triggered to increase HR and remove CO₂ via exhalation
• When pH rises, frequency of impulses to medulla oblongata is reduced, reducing frequency of impulses sent to SAN, thus reducing HR

• Detect pressure changes
• High blood pressue → impulses sent to medulla oblongata to reduce HR→ decreases HR by sending impulses along parasympathetic NS to SAN
• Low blood pressure → impulses sent to medulla oblongata centre to increase HR → impulses sent to SAN via sympathetic neurones

• Adrenaline and noradrenaline affect pacemaker region of heart
• Increase frequency of impulses produced by SAN

• Effectors work to restore a change in conditions back to original, reversing initial stimulus 
• E.g. temperature control and water balance in body

• Change in internal environment detected, and effectors stimulated to reinforce the change.
• E.g blood clotting cascade, childbirth

Thermoregulation

• Exothermic chemical reactions
• Latent heat evaporation ~ with water
• Radiation ~ to and from organism and surroundings
• Convection ~ heating and cooling by currents of air
• Conduction ~ heating as a result of collision of molecules. Water and ground are good conductors

• Ectotherms:
• -use surroundings to warm body
• -core body temperature heavily dependent on surroundings
• -invertebrates, fish, amphibians and reptiles
• Endotherms:
• -Rely on metabolic processes to warm up
• -stable body temperature regardless of surroundings
• -mammals and birds

• Behavioral: 
• Basking in the sun
• Orientate body to expose high SA
• Press against warm ground
• Cool down ~ eg find shade
• Physiological: 
• Colour

• Peripheral temperature receptors in skin
• Temperature receptors in hypothalamus

• Vasodilation ~ arterioles near skin surface dilate. Vessels directly connecting arterioles and venules constrict. Blood forced through surface capillaries.
• Sweating 
• Reducing insulation from hair/feathers
• ~ erector pili muscles relax, avoids trapping air

• Vasoconstriction 
• Decreased sweating
• Raising body hair/feathers ~ trap a layer of insulating air
• Shivering ~ rapid, involuntary contraction of muscles to produce metabolic heat

The removal of waste products of metabolism from the body

• CO₂
• Bile pigments ~ formed from breakdown of old red blood cells in liver, excreted in bile, and colour the faeces 
• Nitrogenous waste ~ formed from breakdown of excess amino acids by liver
• (urea for mammals, ammonia for fish, and uric acid for birds)

• Hepatic artery: oxygenated blood
• Hepatic portal vein: from the intestines, loaded with products of digestion
• Hepatic vein: removes deoxygenated blood

• Hepatocytes
• -Large nuclei
• -Prominent Golgi apparatus 
• -Lots of mitochondria

Sinusoids

• Kupffer cells
• -resident macrophages 
• -ingest foreign particles to protect liver form disease

• Carbohydrate metabolism: the store and release of glucose
• Deamination of excess amino acids: the removal of an amine group
• -body cannot store proteins
• -amine group removed → ammonia → urea
• -rest of amino acid fed into cellular respiration or converted into lipids for storage
• Detoxification: liver is the site where many toxins are detoxified & made harmless
• -eg. catalase turns hydrogen peroxide into oxygen and water
• -eg. alcohol dehydrogenase breaks down ethanol into ethanal which is then converted to ethanoate → used to build up fatty acids or cellular respiration

The set of enzyme controlled reactions converting ammonia into urea

• Hepatocytes secrete bile from the breakdown of blood
• -into spaces called canaliculi
• -drains into bile ductules 
• -taken to gall bladder

• Excretion
• Osmoregulation

• Blood enters via renal artery
• Blood exits via renal vein → inferior vena cava
• The pelvis ~ central chamber where urine collects before passing out down ureter 
• The medulla ~ contains tubules of nephrons that form the pyramids of the kidney and the collecting ducts
• The cortex ~ outer layer where blood filtering occurs

• Bowman's capsule: contains glomerulus
• Proximal convoluted tubule: first coiled region of tubule
• -found in cortex
• -many substances reabsorbed into the blood
• Loop of Henle: long loop of tubule that creates region of high solute concentration in medulla tissue fluid
• -descending loop travels into medulla
• -ascending loop travels back up to cortex
• Distal convoluted tubule: second coiled/twisted tubule
• -fine tuning of water balance
• -permeability of walls varies dependent on ADH
• -further ion and pH regulation
• Collecting duct: urine passes down it
• -through medulla to pelvis
• -more find tuning of water balance ~ walls sensitive to ADH
• Capillary network: ~ lead into a venule → renal vein

• Ultrafiltration
• High pressure in glomerulus since blood enters via wide arteriole and exits through narrower arteriole
• Forces blood out through capillary walls
• Fluid passes through basement membrane ~ made of collagen fibres to act as sieve
• Podocytes act as additional filter ~ wrap around capillaries

Reabsorption

• Proximal convoluted tubule
• Moves glucose, amino acids, vitamins and hormones back into blood
• 85% sodium chloride and water (Na+ by active transport, Cl- and water passively) and moved back to blood
• Cells lining tubule covered in microvilli ~ increase SA
• Many mitochondria for active transport

• The ascending limb of the loop of Henle:
• -impermeable to water
• -very permeable to Na and Cl ions
• -they move out by diffusion in the first part
• -& are actively pumped out in the second part
• -produces high concentration of Na and Cl ions in medulla tissue fluid
• The descending limb of the loop of Henle:
• -lower section permeable to water
• -water diffuses out
• -impermeable to Na and Cl ions
• -no active transport

• -permeability of walls vary depending on ADH
• -cells have many mitochondria ~ adapted for active transport
• -if body lacks salt ~ Na & Cl ions actively pumped out
• -water may leave to concentrate the urine
• -balances the pH of blood

• Concentration and volume of urine determined
• -water moves out by osmosis as levels of Na ions increase in surrounding fluid
• -permeability of collecting duct to water altered by ADH

• Produced in hypothalamus & stored in posterior pituitary gland
• Increases permeability of distal convoluted tubule and collecting duct to water
• ~ negative feedback
• Osmoreceptors in hypothalamus linked to its release, and detect concentration of inorganic ions
• -short supply of water → high conc of ions
• -excess of water → blood is more dilute → low conc of ions

• binds to receptors on tubule cells
• triggers formation of cAMP
• cAMP causes:
• -vesicles in the lining of the collecting duct fuse to cell surface membrane by medulla
• -vesicle membranes contain aquaporins (protein water channels), making the cell surface membrane more water permeable.
• -water moves out of tubule cells into tissue fluid
• The more ADH → more water channels inserted into membrane → more easy for water to leave by diffusion → resulting in small amount of concentrated urine

• Antibodies from a single clone of cells produced to target particular cells/chemicals in the body
• 1. Mouse injected with hCG (eg) so it makes appropriate antibody
• 2. B-cells removed from spleen of mouse & fused with myeloma (cancer cell) that divides rapidly
• 3. New cell "hybridoma" reproduces rapidly and makes the antibody which is collected and purified

• 1. Wick soaked in urine from the mother in the morning (highest levels of hCG)
• 2. Test contains mobile monoclonal antibodies attached to small coloured bead, and only bind to hCG.
• 3. If woman is pregnant hCG (from urine) binds forming hCG-antibody complex
• 4. Urine moves up test strip
• 5. 1st window: Immobilised monoclonal antibodies (arranges in line or + shape) bind to hCG-antibody complex, and a colour appears
• 6. Urine continues up test strip to 2nd window
• 7. Line of immobilised antibodies that bind to mobile antibodies regardless of hCG, if colour appears the test is shown to be working

• Used in sport
• Mimic testosterone ~ stimulate growth of muscles
• Excreted in urine ~ gas chromatography and mass spectroscopy

• Infections that damage podocytes and tubules
• High blood pressure ~ damages structure of epithelial cells and basement membreane of Bowman's capsule
• Genetic conditions

• Protein in urine ~ if basement membrane of Bowman's capsule, or podocytes are damaged
• Blood in urine ~ filtering process no longer works

• Loss of electrolyte balance ~ body unable to excrete sodium, potassium, and chloride ions
• Build up of urea ~ can poison cells
• High blood pressure ~ since kidneys help control blood pressure
• Weakened bones ~ calcium/phosphorus balance in blood is lost
• Pain & stiffness in joints ~ abonormal proteins build up in blood
• Anaemia ~ kidneys stimulate formation of red blood cells

• Glomerular filtration rate (GFR)
• Sample of blood measures level of creatinine in blood (breakdown product of muscle)
• Used to give an estimated GFR (eGFR ~ cm³/min)
• If levels increase, kidneys are likely not working properly
• Take into account:
• -age ~ GRF decreases steadily with age
• -gender ~ men usually have more than women due to more muscle mass

• Dialysis:
• -Haemodialysis
• -Peritoneal dialysis
• Transplant

• Dialysis machine
• Blood leaves body into machine
• Flows between partially permeable dialysis membranes
• -mimic basement membranes of Bowman's capsule
• Dialysis fluid
• -normal plasma levels of glucose → no net movement
• -normal plasma levels of mineral ions → excess leaves restoring electrolyte balance
• -no urea → high conc gradient and urea diffuses out
• Blood and dialysis fluid flow in opposite directions → maintain concentration gradients
• Takes 8 hours
• Repeated regularly
• Diet must be managed carefully

• Inside the body ~ making use of natural dialysis membranes found in lining of abdomen (peritoneum)
• At home, normal life while it takes place
• Dialysis fluid introduced using a catheter
• Left several hours
• Fluid drained & discarded

• Single, healthy donor kidney placed within body
• Blood vessels joined and ureter inserted into bladder
• Risk of rejection
• -best match found
• -immunosuppressant drugs
• Transplanted organs don't last forever

• Dialysis:
• +readily available
• -monitor diet carefully
• -expensive long-term
• -eventually damages body
• Transplant:
• +free from restrictions
• -shortage of donor organs
• -immunosuppressant drugs

• Seed absorbs water 
• → embryo activated 
• → produces gibberellins ~ evidence suggests gibberellins switch on genes that code for amylases and proteases
• → stimulate production of enzymes that break down food stores in seed
• → embryo plant uses these to produce ATP for building materials 

Evidence suggests ABA acts as an antagonistic to gibberellins, and it is the relative levels of both that determine germination

• Mutant varieties that lack the gene to produce gibberellins do not germinate, unless gibberellins are applied to them.
• If gibberellin biosynthesis inhibitors are applied, the seed won't germinate until they are removed

• Stimulate growth of main apical shoot:
• -affect plasticity of cell wall ~ auxins make it stretch more
• -auxins bind to receptors on the cell membrane → fall in pH to about 5
• -optimum pH for enzymes needed to keep cell walls flexible
• -cells expand as they absorb water & vacuoles get bigger
• -auxins are destroyed as the cell matures
• -cell walls return to normal pH & go rigid
• Suppress growth of lateral shoots:
• -"apical dominance" 
• -growth in main shoot is stimulated by auxins produced in the tip
• -lateral shoots' growth inhibited as the hormone moves back down the stem
• -further down stem, auxin conc is lower so lateral shoots can grow more strongly
• Promote root growth:
• -low concentrations
• -up to a point, the more auxin, the more the root grows
• -produced in the root tips, and arrives from growing shoots
• -if apical shoot is removed, root growth slows/stops since the amount of auxin reaching the roots is greatly reduced

• If apical shoot is removed, there is no source of auxin from the shoot, and lateral shoots grow faster, freed from the apical dominance
• If auxin is artificially applied to the cut apical shoot, apical dominance returns

• Elongation of plant stems
• -affect the length of the internodes ~ regions between leaves on a stem
• Discovered from a fungus that produced them and affected rice crops making them spindly

• Synergism ~ complementing each other to give a greater response
• Antagonism ~ have opposite effects → their balance controls the response. E.g chemicals that promote and inhibit growth

• A point comes during some seasons when the amount of glucose needed for respiration to maintain the leaves, and produce antifreeze products, is greater than the amount of glucose made by photosynthesis
• -more efficient to lose their leaves and remain dormant

• Sensitive to a lack of light ~ photoperiodism
• Results from a light sensitive pigment phytochrome
• -exists in two forms ~ P_r & P_ft
• -each absorbs different type of light, and their ratio changes depending on levels of light

• Lengthening of darker periods triggers it
• Less light → auxin levels fall
• Leaves respond by producing ethene (gaseous hormone)
• Base of leaf is abcission zone ~ two layers of ethene sensitive cells
• Ethene causes gene switching in them → causing production of enzymes
• These digest cell walls in outer layer of abcission zone ~ forming separation layer
• Vascular bundles sealed off
• Fatty material deposited in cells on stem side of separation layer
• Forms protective, waterproof scar → keeps pathogens out
• Cells deep in separation zone respond to hormonal cues → retaining water → swelling → putting pressure on to cause leaf to fall off (along with other abiotic facors)

• Low temperatures may cause cells to freeze and disrupt their membranes → so they die
• Sustained cold spells and less light suppresses and activates different genes
• Cytoplasm of plant and sap in vacuoles contain solutes that lower freezing point
• Some plants produces molecules that act as antifreeze or ones which protect cells from damage should freezing occur

• Largely controlled by hormone ABA
• Leaf cells release ABA under abiotic stress → stomata close
• Roots provide early warning system:
• -detect fall in soil water / transpiration
• -produce ABA → transported up plant to leaves
• -binds to stomatal guard cells → causing changes in ionic concentrations of cell, reducing water potential and therefore turgor → stomata close

Thorns, barbs, spikes, fibrous inedible tissue, hairy leaves

• Tannins: 
• -bitter taste
• -toxic to insects
• -e.g. found in tea and red wine
• Alkaloids:
• -bitter tasts
• -many act as drugs affecting metabolism and sometimes poisoning
• -e.g caffeine, nicotine, morphine
• -Caffeine toxic to fungi and insects, spreads into the soil preventing germination of other plants
• Terpenoids:
• -often form essential oils
• -act as toxins to insects and fungi
• -some act as repellents
• Pheromones:
• -chemicals which affect social behaviors of another organism of the same species
• -e.g if a maple tree is attacked by insects it releases a pheromone which is absorbed by other leaves to make them produce chemicals such as callose
• VOCs ~ volatile organic compounds:
• -similar to pheromones but between two different species
• -eg. cabbages, caterpillar, wasp

• Folding in response to touch 
• Mimosa pudica 
• -if leaves are touched they fold and collapse ~ scares larger herbivores and dislodges smaller insects
• -leaf takes 10-12 minutes to recover through movement of potassium ion movement and osmotic movement into particular cells

• Photo ~ light
• Chemo ~ chemicals
• Geo (or gravi) ~ gravity
• Thigmo ~ touch

• Germinate and grow seedlings in different conditions. Observe and measure patterns of growth.
• Germinate and grow seedlings under unilateral light with different colour filters to see which wavelengths of light they respond to
• Cover tips of coleoptiles in foil, remove tips, place auxin impregnated agar jelly blocks on decapitated coleoptiles, place auxin impregnated agar blocks on one side only of decapitated coleoptiles

• Light causes the auxin to move to the other side of shoot
• Concentration is higher on the dark side
• Stimulates growth on shady side
• Shoot grows towards the light

• Grow shoots in slowly rotating drum (gives equal gravitational stimulus to all sides) and observe that shoot and roots will grow straight
• 
• Grow seeds in vertical petri dishes and observe their directions of growth
• 

• Control of ripening:
• -fruit harvested when fully formed but not yet ripe
• -cooled, stored and transported
• -ethene applied when needed to ripen batch
• -fruit put on sale to public
• ~ reduces waste and increases window of sale
• Hormone rooting powders and micropropagation:
• -application of auxin to cut stem causes roots to develop
• ~ easier to take successful cuttings (propagation) or perform micropropagation
• Hormonal weedkillers:
• -synthetic auxins can act as weedkillers
• -aimed at type of weed, affect its metabolism and cause it to die
• ~ cheap, low toxicity to mammals, selective

• Photosynthesis: 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂
• Resiration: C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O

• Process by which organic molecules (such as glucose) are broken down into smaller inorganic molecules (like CO₂ and H₂O)
• Energy stored in the bonds is used to synthesise ATP

• Lots of (relatively weak, non-polar) C-H bonds in large molecules such as glucose or lipids
• Broken during respiration to form H₂O and CO₂ (with relatively strong bonds)
• Releases large amounts of energy

• Chemiosmosis 
• Diffusion of protons from high concentration to low through partially permeable membrane
• Their movement releases energy used in attachment of an inorganic phosphate (Pi) to ADP to form ATP
• Conc gradient created with energy from excited electrons

• Electrons raised to a higher energy level by:
• - absorbing light from Sun in the pigment molecules (eg chlorophyll)
• - released when chemical bonds are broken in respiratory substrate molecules

• Made up of series of electron carriers
• -each with progressively lower energy levels
• -energy released as high energy electrons move down chain
• Energy used to pump protons across membrane
• -producing proton gradient
• -maintained as a result of impermeability of the membrane to H⁺ ions
• Protons can move back down gradient through hydrophilic membrane channels linked to ATP synthase 
• -flow of protons through channel provides energy used to synthesise ATP

• Outer and inner membranes
• Membranes form flattened sacs ~ thylakoids
• Thylakoids are stacked to form grana (singular granum)
• Grana joined by membranous channels ~ lamellae 
• Light absorbed by pigments embedded within thylakoid membranes
• Fluid enclosed is called stroma & is site of many chemical reactions forming complex organic molecules

• Made up of light harvesting system and reaction centre
• Chlorophyll b, xanthophylls and carotenoids are embedded in thylakoid membranes along with other proteins, together forming the light harvesting system (or antennae complex)
• -absorbs/harvests light energy of different wavelengths and transfers it to the reaction centre
• Chlorophyll a is located in reaction centre
• -where reactions involved in photosynthesis take place

• Light dependent stage: 
• ~light from sun absorbed & used to make ATP
• ~Hydrogen from water used to reduce coenzyme NADP to NADPH (reduced NADP)
• Light independent stage: 
• ~Hydrogen from NADPH and CO₂ used to build organic molecules 
• ~ATP supplies the energy

• Photosystem II (PSII) absprbs light of wavelength 680nm 
• Excited electrons released into electron transport chain (ETC)
• ATP produced by chemiosmosis
• Electrons lost from PSII replaced from water molecules broken down using energy from Sun
• Photosystem I (PSI) absorbs light at 700nm
• Releases excited electrons to another ETC again producing ATP by chemiosmosis
• Electrons lost from PSI replaced by those from first ETC
• Electrons from PSI released & accepted with a H⁺ ion by coenxyme NADP to form NADPH

• Water molecules split into H⁺ ions, electrons and Oxygen molecules using energy from Sun
• H₂O → 2H⁺ + 2e^- + O₂
• Electrons released from photolysis replace those lost in PSII
• Oxygen is released as a biproduct
• Protons released into lumen of thylakoid ~ increasing concentration gradient ~ when they move back through they drive production of more ATP
• Once they return to stroma they combine with an e^- from PSI and NADP to form NADPH
• - this removes H⁺ from stroma, maintaining concentration gradient

• Electrons leaving PSI return to PSI (instead of being used to form reduced NADP)
• -PSI can therefore still lead to ATP production without e^- from PSII
• -NO reduced NADP is formed

Stroma of chloroplasts

• CO₂ enters intercellular spaces within spong mesophyll of leaves by diffusion through stomata
• -diffuses into cells and into stroma of chloroplasts
• Combined with 5-carbon compound ribulose bisphosphate (RuBP):
• -carbon in CO₂ is therefore fixed ~ incorporated into an organic molecule
• -Enzyme ribulose bisphosphate carboxylase (RuBisCO) catalyses the reaction
• -unstable 6-carbon intermediate produced
• 6-carbon compound immediately breaks down to form two 3-carbon compounds ~ glycerate 3-phosphate (GP)
• Each GP converted to triose phosphate (TP) using hydrogen atom from NADPH and energy from ATP
• TP (a carbohydrate, 3 carbon sugar) is recycled to regenerate RuBP & is the starting point for synthesis of other biological molecules such as carbohydrates, lipids, proteins and nucleic acids

• Fixation ~ CO2 fixed (incorporated into organic molecule)
• Reduction ~ GP reduced to TP by addition of Hydrogen from NADPH using energy from ATP
• Regeneration ~ RuBP regenerated from recycled TP

• It is completely inhibited by oxygen 
• - a lot of it is needed to carry out photosynthesis successfully

• 6 turns of calvin cycle per glucose molecule produced
• -production of 12 TP:
• -10 recycled to make 5 more RuBP using energy supplied from ATP
• -2 used to make glucose

When a factor needed for photosynthesis is in short supply, it reduces the rate of photosynthesis and becomes a limiting factor

• Measure rate of oxygen production, carbon dioxide used, or increase in dry mass of plant
• Sodium hydrogen carbonate used to provide CO₂
• Leave to equilibrate before taking readings
• Calibrate oxygen sensor to conc of air at 21%

• Reduces the rate of light dependent stage
• - reduce quantity of ATP and NADPH produced
• - ATP & NADPH needed to convert GP to TP
• ⇒ concentration of GP increases
• ⇒ concentration of TP decreases
• - Since less TP, concentration of RuBP decreases as it is not regenerated
• (Reverse happens if light intensity is increased)

• Little CO₂
• ⇒ reduced concentrations of GP and TP since less CO₂ to be fixed
• ⇒ RuBP concentration increases since it is still being formed from TP but not being used

• Glycolysis 
• -in cell cytoplasm
• -anaerobic 
• -Glucose is split into two pyruvate molecules

• Phosphorylation:
• -2 ATP provide 2 phosphates 
• -which attach to glucose
• -form hexose bisphosphate
• Lysis:
• -destabilises molecule splitting it into 2 TP (triose phosphate) molecules
• Phosphorylation:
• -phosphate group added to each TP
• -from free Pi ions in cytoplasm
• -forms 2 triose bisphosphate
• Dehydrogenation & formation of ATP:
• -removal of hydrogen (oxidising) from each
• -H from each combines with 2NAD to form 2 NADH
• -phosphates from each used to produce 4 ATP molecules (2 for each triose bisphosphate)
• -results in 2 pyruvate molecules

• Formation of ATP without electron transport chain
• -transfer of phosphate group from a phosphorylated intermediate (eg triose bisphosphate in glycolysis) to ADP

• 2 ATP
• -since 2 are used at the start
• -4 are produced at the end

• Link Reaction (Oxidative decarboxylation)
• -mitochondrial matrix ~ pyruvate actively pumped in
• -decarboxylation ~ CO₂ removed (& diffuses away/used for photosynthesis in autotrophs)
• -oxidation ~ H removed which combines with NAD to form NADH
• -results in 2-carbon acetyl group which is bound by coenzyme A to form acetylcoenzyme A (acetyl CoA)
• -acetyl CoA delivers acetyl group to Krebs cycle

• Krebs Cycle
• -mitochondrial matrix
• -each cycle results in breakdown of an acetyl group

• Acetyl group delivered from acetyl CoA
• Acetyl group combines with 4-carbon oxaloacetate to form 6-carbon citrate
• Citrate undergoes decarboxylation and dehydrogenation to form 5-carbon compound (1CO₂ and NAD→NADH)
• 5-carbon compound undergoes decarboxylation and dehydrogenation to form 4-carbon compound (1CO₂ and NAD→NADH)
• 1 ATP produced by substrate level phosphorylation 
• FAD reduced to FADH₂
• Another NAD reduced to NADH
• Oxaloacetate regenerated

• Both coenzymes that accept protons and electrons released from breakdown of glucose
• ☆NAD takes part in all stages of respiration, FAD only in Krebs
• ☆NAD accepts 1 H (NADH), FAD accepts 2 H (FADH₂)
• ☆NADH oxidised at start of ETC, FADH₂ oxidised further along (to release protons & electrons)
• ☆NADH results in synthesis of 3 ATP, FADH₂ results in 2 ATP

• Oxidative Phosphorylation 
• -membranes of cristae in mitochondria
• -hydrogen atoms in NADH and FADH₂ delivered to ETC ~ oxidation
• -hydrogen atoms dissociate into hydrogen ions and electrons
• -the high energy electrons used to synthesise ATP by chemiosmosis down ETC
• -at end of ETC electrons combine with H⁺ and oxygen to form water ~ aerobic process

• A form of anaerobic respiration
• The process by which complex organic compounds are broken down into simpler inorganic compounds without oxygen or an ETC  
• -substrate level phosphorylation onl
• -not fully broken down so much less ATP produced

• Alcoholic fermentation
• -yeast 
• -end products: ethanol + CO₂
• Lactate fermentation
• -animal cells
• -produces lactate (lactic acid)

• Pyruvate acts as a hydrogen acceptor from NADH
• -forms lactate and NAD
• -catalysed by enzyme lactate dehydrogenase
• NAD used to keep glycolysis going
• -so ATP is still produced by chemiosmosis
• Lactic acid converted back to glucose in liver using oxygen (reason for oxygen debt)

• Cannot occur indefinitely because: 
• -amount of ATP produced not enough to maintain vital processes for long time
• -accumulation of lactic acid changes pH, denaturing proteins such as respiratory enzymes and muscles

• Pyruvate converted to ethanal
• -removal of CO₂
• -catalysed by pyruvate decarboxylase
• Ethanal accepts hydrogen atom from NADH 
• -forms ethanol
• -NADH → NAD
• NAD able to act as coenzyme allowing glycolysis to continue

• Measure rate of CO2 production
• Yeast + respiratory substrate solution (e.g glucose)
• Sealed flask
• Production of CO₂ caused coloured liquid in capillary tube to move
• Volume of CO₂ calculated based on distance and diameter of tube

RQ = 

Measured using respirometer

• 1
• -6 molecules of oxygen in
• -6 molecules of carbon dioxide produced

• Lipids have highest energy content and low RQ
• Proteins
• Carbohydrates have lower energy content and RQ of 1

• Normal activity: 0.8-0.9
• -since carbohydrates, lipids and some proteins are being used as respiratory substrates
• Anaerobic respiration: above 1.0

• Respirometer:
• -potassium hydroxide solution at bottom absorbs CO₂ produced
• -so any change in volume will be due to oxygen uptake
• -left to calibrate
• -coloured fluid added to capillary tube ~ see how far it moves