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Biology A2 by Mind Map: Biology A2
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Biology A2



Chemiosmosis, Flow of protons across a partially permeable membrane - coupled to generation of ATP., Eukaryotes: Inner Mitochondrial Membrane, Prokaryotes: Cell surface membrane (may be invaginated to increase S.A., Early Studies (1940s), Thought energy associated with NAD - first stored in a high-energy interm. chemical before being used to make ATP (no investigations found interm.), Peter Mitchell's Chemiosmosis Theory (1961), Realised build up of protons on 1 side of membrane = source of potential energy. AND that their movement down electrochemical gradient could provide energy needed to power formation of ATP from ADP and P., Therefore, IMM = an energy-transducing membrane., Energy released from ETC - pumps H+ to IMS & that they flow back through protein channels attached to enzymes. Kinetic energy of flow (proton motive force) drove ATP formation., Radical theory from idea of high-energy interm. compound, but by 1978, lots of evidence to support theory., Other Studies, ATP not made if mushroom-shaped parts of stalked particles (ie ATP synthase enzymes) removed., ATP not made in presence of antibiotic Digomycin - blocks flow of protons through ion channel., In intact mitochondria, pH of IMS is lower than matrix and p.d. is -200mV


Why Anaerobic, No oxygen, Note, The need for re-oxidation, Note

Lactate Fermentation, Process, Note, Equation, Pyruvate-----(Red NAD - NAD)------>Lactate, Info, When oxygen is available the lactate produced is changed back to Pyruvate making it less wasteful than alcoholic fermentation., The muscles can cope with a build up of lactate however it is the lowered pH that occurs as a result that causes cramp, Lactate fermentation occurs in mammals only

Alcoholic Fermentation, Equation, Pyruvate--(Red NAD - NAD)-->Ethanal--(Red NAD - NAD)-->Ethanol, Process, Note, Info, This process cannot occur for too long as mopre than 18% ethanol in the yeast cell and it dies., It produces very little ATP so makers of alcoholic beverages first grow the bacteria under aerobic conditions so the yeast cells grow and then switch them to alcoholic fermentation

Basic Info

Co-enzymes, NAD, Structure, Function, Note, Co-enzyme A, Function, It's fuction is to bind to the substrate Acetate (Ethanoate) and transport it to the Krebs cycle. This may be from the beta oxidation or it could be from amino acids or the link reaction., Structure, Why Co-enzymes, Enzymes are in general poor at oxidation/reduction reactions yet a large number are needed for respiration thus co-enzymes are needed to facilitate the reactions.

ATP Info, ATP structure, Def: A phosphorylated nucleotide, the universal energy currency, Adenine - nitrogenous base, Ribose - Pentose sugar, Phosphate groups, Image, ATP Uses, Used in Active transport to resist concentration grapdients., Used in the movement of flagella in bacteria or cilla in the lining of the lungs., Protein synthesis in the endoplasmic reticulum, Activation of hormones and the secretion of said hormones (exo/endocytosis), ATP Source, From a variety of sources including Glycolysis, Krebs cycle and Oxidative phosphorylation., Releasing energy from ATP, Note

Substrates, Testing for substrates, Respirometers, Process, Stage 1: The apparatus is set up like below. No measurements are taken for a few minutes to allow the organism to acclimatise to the new environment, Stage 2: Oxygen consumption per unit time can be measured by reading the level on the manometer fluid against the scale. As oxygen is taken in for respiration it changes the pressure in the air causing the manometer fluid to rise., Stage 3:The experiment is repeated without potassium hydroxide. The amount of CO2 is measured by reading the manometer level whilst taking into account the changes in pressure caused by oxygen uptake., A respirometer is a device suitable for measuring the rate of respiration for small terrestrial invertebrates., Key components, Potassium Hydroxide solution, Absorbs CO2, Syringe, Maintains pressure and allows adjustment of the manometer fluid, Manometer, Allows changes in volume to be seen and thus the amount of O2 taken in recorded., Glass beads, Often used as a control to make sure the organism is changing the manometer fluiid, RQ Values, Volume of O2 produced/ Amount of CO2 produced, Image, Different Substrates, Carbohydrates, ATP Yield, Note, RQ Value - 1.0, Definition: A respiratory substrate is an organic substance that can be used for respiration., Protein, RQ Value: 0.9, Protein is respired when the body is going through fasting, starvation or prolonged exercise., Amino Acids, Some proteins are broken down into amino acids and then further deaminated. The resulting substrate can then be converted into glucagon or fat and then be respired normally, Some Amino acids enter the Krebs cycle directly, All amino acids produce slightly more reduced NAD during respiratory reactions and so produce more ATP through Oxidative Phosphorylation per the equivalent mass of glucose., Lipids, RQ Value: 0.7, Fatty Acids, These chains contain huge amounts of carbon and hydrogen atoms and so are a large source of reduced NAD and thus produce the most ATP per equivalent mass of each substrate., Process, Stage 1: Each fatty acid is combined to a CoA molecule. This requires an ATP molecule to be dephosphorylated twice to form AMP +2x Pi., Stage 2: The fatty acid CoA complexes are transported to the Matrix, Stage 3: Beta oxidation causes the complex to break down into acetyl groups which binds to CoA. Beta oxidation also produced reduced FAD and NAD in the process, Stage 4: The Hydrogen carries are taken to the inner membrane for oxidative phosphorylation and the acetate groups take part in the Krebs cycle., Glycerol, This can be converted to Glucose and take place in normal respiratory reactions., Glycerol and Fatty acids are broken part in a hydrolysis reaction which requires 3 H2O molecules (One for each hydrocarbon chain)

Definition, Def: The process by which energy stored in complex organic molecules is used to make ATP, Used in Maintaining temperature through the production

Mitochondria Structure

Size Shape and Distribution, Size, Very small shape between 0.5-1.0 micrometers in length and this allows a large number to be fitted inside a cell, up to 2500., Shape, They are long sausage shaped cylinders to increase surface area and thus overall ATP yield., Distribution, Distributed in cells towards an area which requires most ATP such as the ends of synaptic knobs, they are moved there through microtubles

Outer Membrane, A normal phospholipid bi-layer that contains channel proteins in it. These channels are important for letting the molecule pyruvate in from the cytoplasm to the Matrix to take part in the Krebs cycle.

Inner Membrane, Highly folded, Increased surface area increases the maximum ATP yield from oxidative phosphorylation, Electron transport Chain, Note, ATP Synthase, Allows diffusion of H+ ions across the membrane through this enzyme, also is used for binding ADP and a phosphate group to produce ATP. These enzymes exist in the membrane with the stalk towards the matrix end., Impermeable to ions, This allows a build up of H+ ions in the intermembrane space as a potential source of energy.

Matrix, Contains Krebs Cycle reagents such as Oxaloacetate needed for Krebs, It contains Mitochondrial DNA for specific enzymes such as ATP synthase which means that Mitochondria can exist without a nucleus and cut down time on DNA transport, Contains coenzymes needed for Krebs cycle.


Glycolysis, Stage 1: Phosphorylation, Note, Stage 2: Splitting, Note, Stage 3: Oxidation of TP, Note, Stage 4: Conversion, Note, Overall, 2x Molecules of ATP, 2x molecules of Pyruvate, 2x Reduced NAD

Link Reaction, 2 Reactions, Decarboxylation, using a decarboxylase enzyme, Dehydrogenation, using a dehydrogenase enzyme, End Products per molecule of Glucose, 2x Reduced NAD, 2x CO2, 2x Acetate, transported to the Krebs cycle using CoA to form Acetyl CoA, Occurs in the Matrix and occurs twice for every molecule of Glucose

Krebs Cycle, Stage 1: Acetate + Oxaloacetate --> Citrate, Stage 2 --> Various intermediates, End Products per molecule of Glucose, 6x Reduced NAD, 4x CO2, 2x Reduced FAD, 2x ATP, Occurs in the matrix and occurs twice for every molecule of Glucose

Oxidative Phosphorylation, Stage 1: Red NAD, Note, Stage 2: Cytochromes, Note, Stage 3: Oxidative Phosphroylation, Note, Stage 4: Final electron acceptor, Note


Photosynthesis Experiments

Investigating the factors that affect the Rate of Photosynthesis (1), Photosynthometer (light intensity on oxygen produced) Experiment, Fill photosynthometer (aka Audus microburette) with tap water, Well-illuminated 7cm piece of Elodea - make sure bubbles of gas from stem., Place cut-end upwards into test tube with same water that Elodea was kept in & add 2 drops sodiumhydrogencarbonate soln., Beaker at 20degreesC, Light source as close as possible (1/d^2), Acclimatisation: 5-10 mins, Position capillary tube over cut end for known period of time (5-10mins), gently pull syringe so air bubble near scale - measure its length x pi r^2 = volume gas collected, Gently push plunger so bubble expelled + repeat with different distances, Carbon dioxide on O2 produced, vary no. of drops of sodium hydrogencarbonate soln, Temperature on O2 produced, Alter temp of water bath (though not v accurate as warmer water reduces solubility of O2)

Investigating the factors that affect..... (2), Changes in Density of Leaf Discs, Drinking straw cut leaf discs from cress cotyledons, 5-6 discs in 10cm3 syringe - half-fill syringe with dilute sodium hydrogencarbonate soln, Hold syringe upright, finger over end, gently pull out plunger --> pulls air out of air spaces in spongy mesophyll --> increases density therefore sink to bottom of syringe, Once all discs sunk, transfer syringe contents to small beaker & using bright light, time how long it takes for 1 disc to float to top (Rate: 1/t), O2 produced, Repeat readings at different light intensities

Light Dependant Reactions

Non-cyclic Photophosphorylation, Thylakoid, First photon absorbed by PSII (loss of 2e-), Excited 2e- --> electron acceptor --> electron carrier proteins ---> PSI (p700), Energy loss - pumps protons from stroma into thylakoid space => chemiosmosis, proton motive force, ATP formation, Photolysis occurs: H20 -> 2H+ + 2e- + 1/2O2, 2H+ used reduce NADP, 2e- replaces PSII's loss, Second photon absorbed by PSI, Excited 2e- pass down ETC to final acceptor NADP reductase, 2NADP + 2e- + 2H+ = 2NADPH, Z-scheme

Cyclic Photophosphorylation, Thylakoid, Photon strikes PSI, ETC, Never reaches NADP... passed to cytochrome b6f then back to PSI, Energy loss - pumps protons etc... some ATP made

Light Independent Reactions

Calvin Cycle, CO2 in combines Ribulose Biphosphate (RuBP) catalysed by Ribulose Biphosphate Carboxylase (Rubisco) = Glycerate-3-Phosphate (GP), GP reduced by NADPH using energy from ATP hydrolysis, Converted to TP, Hexose sugars, E.g. glucose, fructose, glycerol, Fatty acids, (+glycerol) = lipids, Amino Acids, Most converted back to RuBP (5 out of 6 TP), Stroma

Where carbon dioxide is fixed & used to build complex organic molecules

Structure of Chloroplasts

Double membrane ie envelope, Inner membrane - transport proteins - control entry/exit substances between cytoplasm & stroma, Intermembrane space, Outer membrane - permeable to many small ions

Photosystems, Primary Pigment Reaction Centre, Chlorophyll 'a', Absorbs 450nm (blue), Absorbs 680/700nm (red), Porphyrin group (similar to 'haem' - contains Mg instead of Fe), Long Phytol (hydrocarbon) chain, Reflects yellow-green, Accessory Pigments, Chlorophyll 'b', Absorbs 500nm & 640nm (yellow/green), Reflects blue-green, Carotenoids, Absorbs light wavelengths not well absorbed by chlorophylls & passes energy associated with that light to chlorophyll 'a' at base of photosystem, Absorbs blue, Carotene: reflects orange, Xanthophyll: reflects yellow, Photosynthetic Pigments: Molecules that absorb light energy. Each pigment absorbs a range of wavelengths in the visible region & has its own distinct peak of absorption. Other wavelengths reflected., Allow maximum absorption light energy

Many grana (each up to 100 thylk membranes), Large S.A., Photosynthetic pigments, Electron carriers, ATP synthase enzymes, Proteins embedded in grana hold photosystems in place

Fluid-filled stroma, enzymes catalyse reactions of L.I. stage, Surrounds the grana so that the products of the L.D. stage can readily pass into it

Chloroplast DNA & ribosomes, Code for & assemble proteins

Limiting Factors

The factor in a metabolic process that is present at the lowest/least favourable value, Carbon dioxide, No other limiting factor, rate of photosynthesis increase as CO2 increases, More molecules GP therefore TP, High number of stomata open - increased transpiration - plant wilting - stress response - stomata close, Low, RuBP increases, GP decreases, TP decreases, Light Intensity, Rate of Photosynthesis directly proportional, Causes stomata to open, Trapped by chlorophyll & excites e-, More ATP & NADPH produced, Splits H20 = H+, 1/d^2 (distance halved, light intensity quartered), Low, Less ATP & NADPH, RuBP decreases, GP increases, TP decreases, Temperature, Rate of photosynthesis increases, 0-25degreesC : q10, Enzyme-catalysed reactions of Calvin cycle work @ optimum, Above 25 degrees, plateaus, Enzymes work less efficiently, O2 successfully competes for Rubisco's active site, Photorespiration exceeds photosynthesis, ATP & NADPH and wasted, Cause more water loss from stomata - close - limits availability of CO2, Too high - enzymes denature

Communication and Homeostasis

The Neuronal System

Sensory Receptors, Energy Transducers, Rod and cone cells in retina, Light intensity and range of wavelengths, Olfactory cells lining inner surface nasal cavity, Presence of volatile chemicals, Pacinian corpuslces in skin, Pressure on skin, Sound receptors in inner ear (cochlea), Vibrations in air, Taste buds in tongue, hard palate, epiglottis & first part oesophagus, Presence of soluble chemicals, Propriocepters, Length of muscle fibres

Features of Neurones, Very long - A.P. transmitted over long distance, Plasma membrane - many gated ion channels - control entry/exit of Na+, K+ and Ca2+, Na+/K+ pumps that use ATP to actively transport 3Na+ OUT of cell and 2K+ INTO, Maintain pd across plasma membrane, Surrounded myelin sheath - insulates neurone. Nodes of Ranvier - saltatory conduction, Cell body - nucleus, many mitochondria & ribosomes, Motor neurones - cell body in CNS & long axon carries A.P to effector, Sensory neurones - long dendron carrying A.P to cell body (just outside CNS). Short axon to CNS, Numerous dendrites connected to other neurones

Resting Potential: Pd across neurone plasma membrane when neurone is at rest (-60mV), Generator Potential: Stimulus causes some Na+ channels open therefore depolarisation, Threshold Potential reached (-50mV): Voltage-gated Na+ channels open - large influx, Action Potential created (+40mV)

Action Potential transmitted by Local Currents (diffusion of Na+ along neurone), Myelinated: has noR (2-3microm) = saltatory conduction, Schwann cell enshrouds neurone, :) Faster transmission, longer distances, rapid responses, Non-myelinated: a long wave, Several neurones enshrouded in one loosely wrapped Schwann cell, :( Shorter length, shorter distances, used in coordinating body functions (e.g. breathing, digestive system) ie. increased speed not important

Synapses, AP reaches Synaptic Knob (swelling at end of neurone - mitochondria, Smooth ER, neurotransmitter vesicles, VG Ca2+ ion channels in membrane), AP reaches Synaptic Knob = depolarisation, VG Ca2+ channels open - diffusion, Neurotransmitter vesicles, fuse, cell surface membrane, exocytosis, Diffuse, synaptic cleft, postsynaptic membrane, Receptor sites, Na+ channels, open, diffusion, postsynaptic neurone, Generator potential/Excitatory Postsynaptic Potential (EPSP) created - sufficient amount combine = AP, Acetylcholinesterase enzyme, Acetylcholine = Ethanoic Acid + Choline. Diffuse back & recombined using ATP, Roles, Ensure AP transmitted only 1 direction, Several presynaptic neurones can converge to one postsynaptic neurone, One presynaptic neurone can diverge to several postsynaptic neurones, Can filter out unwanted low-level signals (not enough vesicles will be released), Summation: Several small potential changes can combine to produce 1 larger change in pd - amplifying low-level signals, Temporal: Series of AP, Spatial: Several Presynaptic neurones, Acclimatisation (running out of vesicles) - prevents overstimulation

Need for Communication

Multicellular Organisms, Complex - range of tissues & organs, many not exposed to ext environment as they are protected by epithelial tissues and organs. E.g. skin and bark, Stimulus: Any change in the environment that causes a response., Build up of waste products - toxic., Enzymes require set of conditions to work efficiently - pH, temp, aq, freedom from toxins & excess inhibitors, Homeostasis: maintenance internal environment, constant, despite changes., Negative Feedback: A process that brings about a reversal of any change in conditions. It ensures that an optimum state of conditions can be maintained, as any internal environment is returned to its original conditions after the change. It is essential for Homeostasis, Positive Feedback: Increasing change detected by receptors (uncommon and usually harmful)., However, e.g. Pregnancy - cervix stretches, anterior pituitary gland, oxytocin, inc uterine contractions, stretches cervix more, more oxytocin etc until fully dilated & baby can be born., A system under negative feedback is never truly constant as there is always some variation about the mean. However this variation is always controlled within reasonable limits, Response: A change in behaviour or physiology as a result of the change in environment., Coordination to ensure different parts body work together effectively, Covers whole body, rapid, specific, allows cells to communicate with each other, long-term & short-term responses, Cell Signalling: One cell releases a chemical that is detected by another cell, which responds., Cell signalling pathway, Stimulus---->Receptor---->Coordinator--->Effector--->Response, Receptors, Skin cells to detect temperature. Osmoreceptors., Communication systems, Hormonal System, Neuronal System, Effectors, Muscle cells, liver cells, Maintaining Body Temperature, Ectotherm: Organism that relies on ext sources of heat to regulate body temp., Cold, Expose body to sun, Basking - more heat absorbed, more activity, E.g. Snakes, Orientate body to sun, Larger S.A., E.g. Locusts, Hot, Orientate body away, Smaller S.A., E.g. Locusts, Hide in burrow, Reduce heat absorption, E.g. Lizards, Increasing breathing movements, Evaporates more water, E.g. Locusts, Advantages, :) Use less food in respiration, :) Need less food, may be able to survive weeks without eating, :) Greater proportion of energy obtained from food can be used for growth, Disadvantages, :( Less active in cooler temps - may need to warm up in morning - risk of predation, :( May not be capable of activity during winter, never warm up sufficiently therefore NEED sufficient stores of energy to survive over winter without eating, Examples, Snakes: Snakes lounge in the sun for long periods of time to heat up., Locusts: These insects vary between lying in the sun or hiding from it to increase surface area abosrobtion. They can also alter breathing movements change its evaporating cooling effects., Ectotherms tend to be amphibians, insects and lizards, Endotherm: Organism that can use internal sources of heat to maintain its body temp., Cold, Less sweat, No panting, Hairs erect, Vasoconstriction, Liver: Rate of metabolism increased (adrenaline), Spontaneous contractions (shivering) - muscle cells respire more = more heat, Hot, Sweaty sweaty, Panting, Hairs lie flat, Vasodilation, Liver: Rate metabolism reduced - less heat from exergonic reactions e.g. respiration, No spontaneous contractions, Advantages, :) Fairly constant body temp all the time, :) Activity possible in cold temp, :) Ability to inhabit colder parts of planet, Disadvantages, :( Energy intake needed from food, :( More food required (god forbid), :( Less energy from food used for growth, Thermoregulatory centre in Hypothalamus detects change - responds by Negative Feedback, Peripheral Temperature Receptors detect if the environment starts to cool down/heat up - warns brain to initiate behavioural mechanisms e.g. moving into shade.

The Endocrine System

Regulation of Blood Glucose, The Pancreas, The Pancreas has two main functions associated with digestion., Exocrine function, This function involves the release of digestive enzymes (e.g. Amylase) into a variety of different ducts which all eventually drain into the pancreatic duct. This duct then delivers enzymes directly into the duodenum, Endocrine function, Islets of Langerhans, Alpha Cells, These cells produce glucagon and less of these are contained in the islets., Beta Cells, These cells are more common in the islets and mass produce the hormone insulin, The Pancreas also has an important function in control of blood glucose levels. Around 2% of the pancreas contains Islets of Langerhans which are around 0.2 mm in diameter., Image, _, Monitoring blood glucose, Too High, Stage 1: Blood glucose change is detected by Beta cells which immediately release insulin directly into the blood stream., Stage 2: They are picked up by target receptors on Hepatocytes. This then starts the secondary messenger adenyl cyclase which begins production of cAMP., Stage 3: This produces a variety of effects:, Glucose channels are placed inside the cell which increases the amount of glucose entering the cell., Glucose is then sotred by turning into glycogen for storage in a process called glycogenesis., More glucose is used up in its functions such as respiration or fat conversion, Too Low, Stage 1: Low blood glucose levels detected by Alpha cells releasing glucagon, Stage 2: The release of Glucagon is picked up by target Hepatocyte cells and secondary messenger adenyl cyclase activates, Stage 3: This produces a variety of effects, Fatty acids used in respiration to conserve glucose levels., Glucose prodyuced by conversion from amino acids and fats, gluconeogenesis., Breakdown of glycogon to glucose (glycogenolysis, Processing Blood Glucose, Image, _, Stage 1: Beta Cell Structure, Beta cells contain ATP sensitive Potassium ion gates in the membrane of the cell, This ensures that at all times K+ ions are pumped out of the cell creating a negative potential inside the cell of -70 mV. The membrane also contains Ca+ ion channels but these remain closed., Stage 2: Glucose breakdown, During times of high glucose concentrations, glucose will diffuse into the cell., The glucose molecule is then broken down to produce ATP inside the cell, Stage 3: Voltage change, This ATP is detected by the ATP sensitive K+ ion channels causing them to close., This lowers the potential inside the cell making it less negative, Stage 4: Insulin release, This change in voltage causes the opening of the Ca+ ion channels causing the Ca+ ions to flood into the cell., Vesicles containing insulin move to bind with the membrane in response to the Ca+ ions in the cell, Insulin is released from the vesicles by exocytosis, Diabetes, Diabetes Mellitus is a disease that means the body cannot enforce the blood glucose negative feedback loop. This can lead to very high concentrations of blood glucose (Hyperglycaemia) or extremely low levels (Hypoglycaemia), Type I, Called insulin dependant Diabetes or juvenile onset diabetes due to its appearance in early childhood., Thought to be a result of an auto-immune disease., The body cannot store excess glucose as it cannot produce sufficient insulin thus becomes dependant on insulin from another source, Treatments include insulin injections and monitoring levels, Type II, Called non-insulin-dependant diabetes, Possibly caused by target cell receptors deteriorating in condition over time., Factors that increase the chance of this disease are: Obesity, high sugar diet, an Asian or Afro-Caribbean origin or family history., Treatments include careful diet control possibly supplemented with insulin injections or drugs., Insulin Source, Genetically engineered insulin made by bacteria, Advantages of this type of Insulin production are:, Less chance to build up a tolerance, Exact human insulin copy, Lower risk of infection, Adaptable to demand, Less controvertial, Cheaper, Stem Cells, A possible treatment for type I diabetes includes inducing stem cells to differentiate into Beta cells which can then be applied to the pancreas, However Stem Cell use is controversial with research being illegal in some areas of the world.

Regulation of Human Heart Rate, The Heart provides substrates and takes away waste fro cell metabolism to occur. The heart has to adapt to different levels of cell metabolism so has to change its behavior accordingly, Control of the heart rate occurs in the cardiovascular centre in the medulla oblongata this can change heart rate according to signals centre by various receptors and by transmitting those signals to the heart., The heart can change 3 factors to adapt to change, Heart Rate, The heart can change this through nerves supplied from the medulla oblongata. Increased action potentials in the accelerator nerves increase the frequency of the beats. Increased action potentials in the vagus nerve reduce heart rate., The heart also changes to the presence of adrenaline increasing heart rate when present., Stroke Volume (Amount of blood per contraction), Strength of contraction, Factors that increase Heart Rate, Stretching of Carotid Sinus, The carotid sinus monitors blood pressure in the arteries by using stretch receptors. During times of high blood pressure the stretch receptors send signals to the cardiovascular centre to reduce heart rate., Stretching of muscles, During times of exercise, stretch receptors in the muscles send impulses to the cardiovascular centre in order to increase heart rate., Lowered pH, During times of increased exercise the pH is lowered due to the increased carbon dioxide in the blood. pH receptors called chemoreceptors in the carotid arteris, aorta and brain detect these changes and increase heart rate accordingly., Adrenalin secretion, When Adrenalin is secreted in response to stress or excitement the heart rate increases to prepare the body for activity.

Endocrine Basics, An example of hormone use: Adrenalin, Functions of the Adrenal Glands, Medulla, This part of the gland mass produces and releases Adrenalin in response to shock or pain., Adrenalin can increase heart rate., Dilate pupils, Inhibit gut action, Stimulate glycogen/glucose conversion, Adrenalin cause Vasodilation to increase heart pressure, Cortex, This part of the Adrenal glands mass produces other hormones which are steroid., Mineralcorticoids control sodium and potassium in the blood which is important for nerve action, Glucocorticoids control carbohydrate and protein metabolism important in respiration., How Adrenaline works., Adrenaline is a hormone released by the adrenal glands which binds to a specific receptor on the surface membrane of a cell which is complimentary in size, The receptor is associated with an enzyme called Adenyl cyclase which is activated when the receptor detects a molecule of adrenalin, The adenyl cyclase then starts to convert molecules of ATP to cyclicAMP (cAMP), All this is an example of how hormones work as two messages. The adrenaline molecule is the first messenger when it binds to the receptor site. The adenyl cyclase is the second messenger when it begins to convert ATP. The cAMP can then begin to cause the desired effect. First messengers can be grouped together as extracellular and second messengers can be grouped as being intracellular, Glands, Endocrine, This gland secretes the hormone into the bloodstream and is ductless, Exocrine, This gland uses various ducts to secrete the molecule directly to where it is used., Hormones, These are molecular signals released by the endocrine system directly into the blood stream. They act as messengers delivering signals to specific target tissues., There are roughly two types of hormone. Protein hormones which cannot pass through the phospholipid bilayer and steroid hormones which can. Steroid hormones act on the DNA of a cell itself., Hormones work by binding to a specific complimentary receptor found on the surface of a cells membrane. Cells that contain the specific receptor are called the hormones 'target cells' and are target tissues in large quantities.


Excretion Basic Info

Definition, Excretion is the removal of metabolic waste from the body. This encompasses any substances that are toxic or produced in excess.

Why Excretion is importnant, CO2, Respiratory Acidosis, This is a response to the body producing too many hydrogen ions in the blood thus lowering the pH. The increase is caused by CO2 in the blood, They are formed two ways. CO2 in the blood forming carbonic acid and then disassociating. Or the disassociation of hydrogen carbonate ions., The lowered pH intially causes increased breathing to try and remove the CO2 but if the blood pH falls below 7.35 it can result in drowsiness, headaches or difficult breathing. A condition known as respiratory acidosis, Haemoglobin competition, H+ competition, CO2 is transported in the blood as hydrogen carbonate ions in the Bohr effect. However this can also produce H+ ions as they disassociate under the influence of carbonic anhydrase. These ions compete with O2 for space in the Haemoglobin molecule reducing blood oxygen levels., CO2 competition, CO2 can combine directly with haemoglobin to form carboxyhaemoglobin. This molecule does not pick up O2 as readily reducing blood oxygen levels, Nitrogenous Compounds, The body cannot store excess amino acids or proteins but instead of wasting them alters them so they can take part in respiration, However this altering (deamination) produces the very toxic Ammonia which is also highly soluble., To get rid of this compound it is first altered to form Urea in the ornithine cycle and is then passed out through the kidneys.


Structure, Blood flow and the liver, Image of the liver connected to the circulatory system., _, Hepatic Artery, Large artery delivering oxygenated blood to the live, It's large structure allows it to supply a large amount of oxygen needed for the energy intensive metabolic processes occuring inside the live, Hepatic Vein, Deoxygenated blood leaves the liver to return to the Vena Cava in normal circulation, Hepatic Portal Vein, Deoxygenated blood from the digestive system is collected in a large vessel, It contains large amounts of digested substrates that may have uncontrolled concentrations or may be toxic. These substances are then properly treated by the liver in order to keep the body healthy, Bile Duct, Not a blood vessel but is connected directly to the liver. Carriers bile from the liver to the Gall bladder., Gall Bladder, Stores bile produced by Hepatocytes in the liver, Functions of Bile, It emulsifies fats for easy digestion, It neutralises stomach acid, Arrangement of cells in the liver, Imgae of a liver Lobule, _, Cells in the liver are arranged into Lobes to ensure the best contact between blood and hepatocytes. These lobes and then further split into lobules., Hepatocytes, Specialised Liver cells that carry out a number of functions on molecules that pass through the hepatic portal vein. Their secondary function is to provide bile., Kupffer cells, Specialised Liver Macrophages. They are involved in the breakdown of RBD's into bilurubin, a chemical excreted through bile., Sinusoid, The hepatic portal vein and artery split into smaller vessels much like the lungs until they enter a lobule. They the mix in the sinosoid, this is where the majority of hepatocytes conduct their function. Afterwards the blood passes from here to the Hepatic Vein., Bile Cannilicus, Separate to all blood vessels, transports bile made by hepatocytes to the bile duct.

Functions, Control of blood glucose levels, amino acid levels, Synthesis or destruction of Red blood cells, Storage of vitamins, Detoxification, The liver uses a variety of enzymes in order to detoxify chemicals that can crop up in our every day diet. Toxins can be rendered harmless by oxidation; reduction; methylation or combination., Detoxification of Alcohol, The body breaks up alcohol for two reasons. One being that it depresses nerve cell activity slowing reaction times. Secondly it contains potential chemical energy which can be released in respiration., Process/Equation, Ethanol--(NAD-RedNAD)-->Ethanal--(NAD-RedNAD)-->Ethanoic Acid, This ethanoic acid (acetate) automatically binds to CoA where it is transported to the matrix to directly take part in the Krebs cycle, Enzymes used in this reaction are ethanol dehydrogenase and ethanal dehydrogenase, Apart from producing Acetate which produces ATP in the Krebs cycle, detoxification also forms 2x Red NAD which produces lots of energy in Oxidative Phosphorylation, Cirrosis, Detoxification of alcohol takes precedence of beta oxidation in the liver for two reasons. The limited number of reduced NAD means only certain reactions can happen at one time. The second being that ethanol is toxic to the body and needs to be dealt with quickly., This becomes a problem over long periods of time when fats are stored in hepatocytes as lipids because the liver is using the majority of reduced NAD to detoxify ethanol, This leads to fatty liver or cirrosis a common ailment in alcohol abusers, Formation of Urea, Deamination, The Amine group in Amino acids makes it toxic to the body therefore any excess amino acids need to be broken down in the liver. They are eventually borken down to Urea. However first an intermediate (ammonia) needs to be formed), Equation/Process, Amino Acid + O2 ---> Keto Acid + Ammonia, Ammonia however is incredibly toxic to the body and highly soluble so immedietly needs to be converted into a less toxic substance (Urea), The Keto acid which is a by product of deamination and can directly take part in respiration., The Ornithine Cycle, Def: The Ornithine cycle is the process in which ammonia is converted to urea. It occurs partly in the cytosol and partly in the mitochondria., Image, _, Overall Equation, 2NH3+CO2--->CO(NH3)2 + H2O


Water Reabsorbtion, Image, _, Process, Stage 1: Addition of Ions, This occurs in the DESCENDING LIMB of the Loop of Henle which is in the medulla., As the filtrate passes down into the loop of Henle water starts to osmose out. This is due to it's relatively high water potential when compared to the capillary outside the tubule. (Due to the removal of all salts and glucose), This is changed through the diffusion of Na+ and Cl- ions from the medulla into the loop of Henle. This decreases the water potential throughout the descending limb. So at the bottom of the tubule there is very little osmosis occurring., Stage 2: Removal of Ions, This occurs in the ASCENDING LIMB of the Loop of Henle which is in the medulla., As the filtrate passes back up into the ascending limb, sodium and chloride ions begin to pass out of the loop., When in the ascending limb, Na+ and Cl- ions are actively transported out of the membrane into the medulla. This only leaves the ions to pass back into the descending limb in a cycle. The membrane is impermeable to water meaning that as ions are transported out the water potential suddenly becomes very high in the ascending limb, This system is known as the hairpin countercurrent multiplier. It is in place so there is efficient transport of ions between the two limbs so water potential can easily be changed., The net effect of these processes means that as the filtrate enteres the Distal convuluted tube in the cortex the urine is very dilute, Stage 3: Altering Concentrations, In the distal convoluted tubule the concentrations of various ions are changed depending on how much water the body wants to absorb. (see Osmoregulation), Stage 4: Mass Water Reabsorbtion, Here, due to the very high water potential in the collecting duct water osmoses out of the duct., This stage takes place in the collecting duct which is in the medulla, How much water is reabosrbed depends on the concentrations of substances added in the DCT and the permability of the walls of the collecting duct.

Osmoregulation, Definition, The control of water levels and salt levels in the body., This is important because water is gained and lost through a variety of sources(food, drink, urine or sweating), If water potentials in cells vary too wildly they cannot conduct their functions and die, Osmoregulation works as a negative feedback loop which is constantly responding to changes in the normal water potential of blood., Process, Stage 1: Detecting WP fluxations, This happens in the hyperthalamus in the brain which conatins a number of cells called Osmoreceptors, These cells cause stimulation by changing in size according to the water potential in the blood. If blood water potential is too high they swell and if too low they shrink., Stage 2: Changing ADH levels, When a change is detected the osmoreceptors stimulate neurosecretary cells in the brain to produce more or less of the hormone ADH, This hormone travels down the axon to the posterior pituitary gland where it is secreted into the blood stream., Stage 3: Altering the permeability of the Collecting Duct, When blood containing ADH reaches the capillary running alongside the collecting duct it binds to a receptor on the surface of the collecting duct., This binding begins a process of enzyme controlled reactions which stimulate vesicles containing specific water permeable channels called aquaporins to bind with the membrane., With more aquaporins in the membrane more water is reabsorbed through the collecting duct causing an increase in the water potential in the blood stream, If less ADH had been stimulated the urine would become more dilute as aquaporins would be converted back to vesicles, Stage 4: Return to normal WP, When the necessary change in water potential has occurred the neurosecretary cells revert back to the normal amounts of ADH in the blood stream., ADH only has a half life of around 20 minutes meaning changes in collecting duct diameter can be quite rapid.

Kidney Failure, Why Kidney Failure occurs, Diabetes Mellitus (Both types), Hypertension, Infection, Dialysis, Haemodialysis, The most common form of dialysis treatment, Blood is passed through a dialysis machine that contains a partially permeable membrane that contains various concentrations of substances., They contain precise concentrations of salts sugars and water for a healthy diet. They also contain no urea so urea in the blood passes out into this membrane along with excess water., Heparin is used to thin the blood to prevent clotting and any air bubbles that could be harmful are removed from the blood to the body., This process takes place for several hours, 3x a week, Peritoneal, This uses the body's own abdominal membrane to filter out unwanted substances., A tube is permanently placed into the abdomen to dialysis fluid is poured into it to filter out unwanted substances. The blood is pumped past the fluid at a higher pressure than the dialysis fluid to induce fluid exchange., The fluid then has to be drained every few hours, Risk of infection is high with a permanant tube attatched, Transplant, Major surgery which requires a new kidney to be placed into the body and attached to a blood supply. This treatment needs to be used in conjuncture with immunosuppressant drugs., Peritoneal Dialysis Vs Haemodialysis Vs Transplant, Immunospressants, None are needed for either forms of dialysis but are required to stop rejection in a transplant, Diet, Both dialysis options need a carefully controlled diet. A transplant doesn't although it is encouraged some dietary control, Time consumed, Haemodialysis requries hospital trips for hours 3x a week. Peritoneal requires dialysis fluid changes every 3 hours. A transplant has no such restrictions other than surgery, Manoeuvrability, With Haemodialysis constant trips to the hospital are needed to get access to the dialysis machine unless one is purchased privately for the home, Peritoneal dialysis permits greater manoeuvrability but a supply of dialysis fluid always needs to be near by, Transplant allows air travel with no restrictions, Quality of Life, With both forms of dialysis there is a feeling of being chronically ill however with peritoneal there is greater manovrability. The transplant offers greatest quality of life however, Surgery, No surgery needed for dialysis however for a transplant heavy surgery is needed risking infection to other vital organs

Testing Urine samples, Pregnancy testing, This processes uses a MONOCLONAL ANTIBODY to bind to a hormone called human chorionic gonadotrophin (hCG) which is produced up to 6 days after pregnancy., The Monoclonal antibody means it will only bind to this protein. Once attached the antibody is tagged to a blue bead which moves up the test., One line is always used as a control, another indicates pregnancy., Anabolic steroid testing, Anabolic steroids increase protein synthesis which results in the build up of muscle tissue, These steroids always remain in the blood for several days and can easily enter the nephron. They are tested for using gas chromatography, Gas chromatography involves the vaporisation of a sample in a gas solvent. As the sample passes down the the apparatus different substances are absorbed at different times. If the steroid is present it will be absorbed at a specific place. The resulting chromatogram is compared with other standards to indicate the presence of a drug

Ultrafiltration, Definition, Ultrafiltration is filtration at a molecular level where molecules in the glomerulus pass into the Bowman's capsulre, Process, Stage 1: Endothelium of Capillary, Contains tiny holes in the capillary wall to allow tissue fluid to pass out of the molecule, Stage 2: Basement membrane, This is a mesh of collegen and glycoprotein fibres which prevent molecules of an area greater than 69000 RMM to enter the proximal convuluted tubule, Stage 3: Podocytes, Also known as the epitherial cells of the bowman's capsule. These have villi like shapes which increase the surface area of the podocyte so more tissue fluid can flow into the proximal convulted tubule, Image, _, Ultrafiltration occurs due to different pressures in the afferent and efferent arterioles. As the efferent arteriole is smaller in diameter than the afferent arteriole, this creates pressure forcing blood plasma in the glomerulus into the Bowman's capsule, What is filtered, Left in blood, Some key proteins that keep the water potential in the blood low so that water reabsorbtion can occur later on and so that the blood doesn't run too thick., Red Blood Cells, Molecules with RMM>69000, Taken out of blood, Amino acids, Water, Urea, Inorganic ions, Salts and Sugars

Selective Reabsorbtion, Process, Stage 1: Na+ ions are actively transported out of the outer PCT lining into the capillary creating a concentrations gradient in the wall, Stage 2: Na+ then flow in through the glomerular filtrate in association with the cotransporters. These cotransporters also bring glucose and other amino acids in with them, Stage 3: The amino acids and glucose then diffuses into the capillary as per normal., Image, _, Proximal Convuluted Tubule adaptations, The lining contains microvilli which helps increase the surface area of the wall and thus the amount of substances that can be reabsorbed at any one time, Contransporters in the lining of the wall help transport glucose and other salts across the membrane in facilitated diffusion, The outer lining of the tubule contains sodium-potassium pumps that help move ions in order to help facilitated diffusion, The cells in the wall contain many mitochondria in order to process the vast amounts of active transport in removing sodium ions from the lining of the PCT

Structure, Kidney, Capsule, Covers the kidney and resists pressure and volume fluctuation. Maintains shape., Renal Artery/Vein, Brings oxygenated blood to the kidney/ takes away deoxygenated blood from the kidney, Medulla, Inner part of the kidney and contains the collecting ducts and the loop of henle of the nephron. It has a vast capillary network, Cortex, Consists of renal capsules and the majority of the nephron, it has an extensive blood supply and is the outer part of the kidney, Ureter, Transports urine from the kidney to the bladder., Image, _, Nephron, Bowman's Capsule, Afferent arteriole supplies blood here, it is the site of ultrafiltration and comprises of three membranes. The area inside the capsule is called the glomerulus. This is in the cortex, Proximal Convoluted Tubule, This is the site of selective reabsorbtion and in all about 85% of reabsorbtion occurs here. This is in the cortex, Loop of Henle, This is where ion concentrations are altered for water reabsorbtion, it is a hairpin countercurrent multiplier. This is in the medulla., Distal Convoluted Tubule, This is where salt concentrationsa re altered in accordance with ADH levels. This is in the cortex, Collecting Duct, This is where the majority of reabsorbtion occurs it is always the site of the majority of osmoregulation. This is in the medulla., Image, _