OCR Biology F214 Communication, Homeostasis and Energy Friday 22 June 2012

My last hope

Got 39/60 last time.

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Reply 181

147madz

Original post by YB101

My last hope

Got 39/60 last time.

This was posted from The Student Room's iPhone/iPad App

Not as bad as me I had 34. LoL!! I need to get a B!! . I mean it is do able I first had an E in one of my biology exams I resat it and got a couple of marks off an A. I'm sure you'll be fine :smile:

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Reply 182

im so fresh

12

ehh.
now that F215 is out of the way.
hello F214!

Reply 183

This thread seems dead. :frown:

Reply 184

Communication and Homoeostasis:
-as the external environment changes, it may place stress on the living organism. If the organism is to remain active and survive, the changes in the environment must be monitored and the organism must change its behaviour or physiology to reduce the stress.
-environmental change is the stimulus and the way in which the organism changes its behaviour or physiology is its response.

internal environment:
-as the cells undergo metabolic activities they might produce waste products, some of which may be toxic. To prevent an accumulation it has to be removed,
-it is important that the concentrations of wastes and all substances in the blood are monitored closely. it ensures that the body doesn't excrete too much of any useful substances, but removes enough of the wastes to maintain good health. it also ensures that all the cells of the body are supplied with needed substances,

-multicellular organisms are more efficient than single celled ones, which means that cells can be specialised to perform particular functions.
-the cells that monitor the blood may be be in a different place in the body and well away from the cells that release a substance into the blood or well away from the organ that removes the substance from the blood,

cell signalling:
-one cell releases a chemical that is detected by another cell, the second cell will respond to the signal released by the first cell,

neuronal system:
-interconnected network of neurones that signal to each other across synapse junctions, the neurones can conduct a signal very quickly and enable rapid responding to stimuli,

hormonal system:
-secretes hormones into blood, recognized by specific target cells, enables longer-term responses to be coordinated.

Homoestasis:
negative feedback:
-is a process that brings about a reversal of any change in conditions. It ensures that optimal steady state can be maintained.

positive feedback:
-is a process that increases any change detected by the receptors,

Homoestasis:
-is the maintenance of the internal environment in a constant state despite external changes,

Reply 185

Sparkzz

4

I hope this is ok. Need to look at photosynthesis abit more!

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Reply 186

user977153

Anyone resitting this beastie?

Reply 187

Original post by DoctorVertigo

Anyone resitting this beastie?

i am doing this paper for the first time and this time i am going to check all the legacy papers so in case they will put the exact same thing up

Reply 188

Benilyn

Original post by DoctorVertigo

Anyone resitting this beastie?

Yeah I'm resitting :/ Thought I knew it in January but apparently not :/

Reply 189

Lomas

Original post by DoctorVertigo

Anyone resitting this beastie?

yeah and i honestly dont have a clue where to even start! f215 has taken it out of me!! haha

Reply 190

Original post by Lomas

yeah and i honestly dont have a clue where to even start! f215 has taken it out of me!! haha

want to ask each other questions from chapters 1 and 2 ?

Reply 191

Lomas

Original post by otrivine

want to ask each other questions from chapters 1 and 2 ?

will do it later in the week because i havent even look at it yet, going to start today

Reply 192

AlexandraRose

Hopefully i'll get higher than an E this time. :tongue:

Silly respiration questions in Jan.

Reply 193

Homoeostasis:
-is the maintenance of internal environment in a constant state despite external changes,

-change away from optimum->receptor detects change->communication system informs effector->effector reacts to reverse change->return to optimum conditions

positive feedback:
-change away from optimum->receptor detects change->communication system informs effector->effector reacts to increase change->change away from optimum

sensory receptors:
-has dendrites, cell body, axon hillock, myelin sheath, node of ranvier, axon,
-convert energy into nerve impulses,
-neurones have specialised protein channels that are specific to either potassium or sodium ions,
-sodium potassium ion pumps, more na ions are actively transported out of the cell than potassium ions transported inside. the cell is negatively charged compared to outside-polarised,
-by altering the permeability to sodium ions, more come into cell, which creates a change in potential difference across the membrane-inside the cell is less negative than usual->DEPOLARISATION,

Resting and action Potentials:
-at rest, three sodium ions are pumped out for every two potassium ions coming in,
-plasma membrane is more permeable to potassium ions so many diffuse out again, hence it is of a negative potential compound to the outside,
-if some of the sodium ion channels are opened they will diffuse down their concentration gradient into the cell causing depolarisation,
-the gates further along the neurone are opened by changes in the potential difference across the membrane,

cholinergic synapse:
-gap called synaptic cleft,
-uses acetylcholine as neurotransmitter,
-specialised sodium ion channels can respond to the transmitter substance,
-these channels consist of five polypeptide molecules, two of which have a special receptor site specific to acetylcholine, they are complimentary, when it binds to receptors (two of them) the sodium ion channel open,

transmission across the synapse:
-action potential arrives at the synaptic knob,
-voltage gated calcium ion channels open,
-calcium ions diffuse into the synaptic knob,
-the calcium ions cause the synaptic vesicles to move to and use with presynaptic membrane,
-acetylcholine is released by exocytosis,
-acetylcholine molecules diffuse across the cleft,
-acetylcholine molecules bind to receptor sites on the sodium ion channels in the postsynaptic membrane, na channels open,
-na ions diffuse across membrane to postsynaptic neurone, generator potential created, if enough gp is created they combine and action potential is created,

-when an action potential occurs, the na channels open at a particular point along the neurone, which allows na ions to diffuse across membrane down the concentration gradient into neurone,
-this upsets the balance of ionic concentrations created by ionic pumps,
-the concentration of sodium ions rises, which causes them to diffuse sideways,
-voltage gated channels found further along the membrane are opened by voltage changes,

-the movement of sodium ion along the neurone alters the potential difference across the membrane, when the potential difference across the membrane is reduced, the gates open, which allows sodium ions to enter the neurone at a point further along the membrane. The action potential has moved along the neurone.

Ionic movement:
-membrane starts in its resting state-polarised with the inside of the cell being -60mV compared to the outside,
-sodium ion channels open and some diffuse into the cell,
-it depolarises-it becomes less negative with respect to the outside and reaches the threshold value of -50mV,
-voltage gated channels open and many na+ ions come in,
-it reaches +40mV,
-potassium channels open, sodium closes,
-potassium ions diffuses out of cell, making it negative-re-polarisation,
-it's hyper-polarised,
-original resting state returned,

the myelin sheath:
-insulating layer of fatty material,
-ions can't diffuse through,
-makes it saltatory,
-speeds up transmission of action potentials,

-when a stimulus is at a higher intensity the sensory receptor will produce more generator potentials-more fragment action potential,

-myelinated neurones can transmit impulses much more quickly, because of saltation caused by
nodes --> a more rapid response to stimulus,

acetylcholinesterase:
-it's an enzyme found in the synaptic cleft,
-it hydrolyses the acetylcholine to ethanoic acid and choline, which stops the transmission of signals so that the synapse doesn't continue to produce action potentials,
-ethanoic acid and choline recycled,
-they re-enter the synaptic knob by diffusion and are recombined to acetylcholine using ATP from respiration in the mitochondria,

signals and messages:
-several pre-synaptic neurones might converge into one post-synaptic neurone,
-one pre-synaptic neurone might converge/diverge to several post-synaptic neurones,
-synapses ensure that signals are transmitted in the correct direction,
-synapses filter out unwanted signals,
-acclimatisation-alter several stimulus, it might run out of vesicles, no longer responds,
-summation: low level, signals can be amplified, combine generator potentials to produce an action potential,

(edited 11 years ago)

Reply 194

Lomas

what are the general grade boundaries for this exam?

Reply 195

Sensory receptors:
-very long neurones
-cell surface membrane has many gated ion channels,
-sodium/potassium ion pumps that use ATP to actively transport ions,
-fatty myelin sheath,
-long dendrons,

ATP:
-adenosine (adenine + ribose)
-three phosphate groups,
-0..6kJmol released when ATP is hydrolysed and Pi leaves,
-immediate source of energy,
-max yield is rarely achieved,
-some protons leak across the membrane,
-some ATP used to transport pyruvate,
-some is sued to transport hydrogen from reduced NAD,

adrenaline:
pit binds to specific receptor on the cell surface membrane,
-adrenaline is the first messenger,
-activates enzyme adenyl cyclase,
-it converts ATP to cyclic AMP,
-The cAMP is the second messenger,
-it causes an effect by activating enzyme action,
-prepares body for activity,
-increases heart rate/mental awareness,
-dilate pupils, makes body hair erect,
-glycogen -> glucose,

Endocrine System:
endocrine gland:
-secretes hormones directly into the blood,
exocrine gland:
-secretes molecules into a duct that carries the molecules to where they are used,
hormone:
-released by endocrine glands, they act as messengers carrying a signal from one gland to a specific target organ or tissue,

Ectotherms:
-body temperature fluctuates with external temperature,
-expose/orientate body to sun,
-increase respiration,
-alter body shape,
-less food used in respiration, so can be used for growth,
-less active in cooler temperatures,

Endotherms:
-move into sunlight,
-orientate to increase surface area exposed to sun,
-move about to generate heat in muscles,
-thermo-regulatory centre in the hypothalamus monitors blood temperature,
-peripheral temperature receptors in the sun monitor the temperature in the extremities, if too cold or hot it will notify the brain,
-increase the rate if respiration - to release heat (liver),
-fairly constant body temperatures,
-more food required,
-sweat glands-heat released to evaporate the water in sweat,
-hairs lie flat-little insulation-more heat lost,
-vasodilation -> more heat lost,
-liver cells - less heat generated,
-skeletal muscles - no spontaneous contractions,

Respiration:
Why do we need to respire?:
-active transport,
-secretion,
-synthesis of molecules,
-replication of DNA,
-movement,
-activation of chemicals,

mitochondria:
-consists of outer membrane, inner membrane, matrix (link reaction + krebs cycle),
-cristae,
-inner membrane, impermeable to small ions including protons,
-electron carriers and ATP synthase enzymes,
-cristae-large surface area,
-has many electron carriers and ATP synthase,
-coenzyme FAD is tightly bound to an enzymes dehydrogenase, which is embedded in inner membrane,
-proton accepted by FAD pass into mitochondria matrix,

glycolysis:
-2 ATPs are hydrolysed, they attach to glucose -> activated fructose 1,6 biphosphate,
-energy from ATP activates hexose sugar and prevents it from being transported, hexose 1, 6 biphosphate,
-split into two triose phosphates,
-two hydrogen atoms are removed and accepted by NAD -> reduced NAD, two NAD- made 2 * ATP made,
-four enzyme catalysed reactions convert each triose phosphate into pyruvate,
-2 ATP,

Link reaction:
-acetate accepted by co-enzyme A, acetyl CoA forms,

Krebs cycle:
-acetate offloaded from CoA(2c), joins with oxaloate(4c) to form citrate,
-citrate is decarboxylated and dehydrogenated, rNAD + CO2,
-5C compound forms-> 4C compound->, rNAD + CO2,
-4C compound -> 4c compound, ADP +P-> ATP,
-4c COMPOUND-> 4C compound, rFAD,
-4C COMPOUND -> oxaloate, rNAD,

Oxidative Phosphorylation:
-O2 final e- acceptor,
-involves e- carriers found in cristae,
-complex/NADH-coenzyme Q reductase,
-protons go into solution in the matrix,
-as e- how along electron-transport chain, enery is released and used by coenzymes to pump protons across to the innermembrane space,
-which builds up a proton and pH gradient,
-potential energy build up,
-H ions can't diffuse through lipid part,
-as protons flow through ATP synthase enzyme, ATP is made,
-4h+ + 4e- +O2->2H2O,

chemiosmosis: the evidence:
-when isolated mitochondria is placed in solution of very low water potential, outer membrane is ruptured, releasing content of the intermembrane space,
-by further treating the resulting mitoblasts with strong detergents, they could rupture the inner membrane and release contents on matrix,
-electron transfer in mitoblasts didn't produce ATP, so they concluded that the intermembrane space was also involved,
-if the mushroom shaped parts of the stalked particles were taken away ATP wasn't made,

Anaerobic respiration:
lactate pathway:
pyruvate ---------------> lactate
rNAD---->NAD, 2H added to pyruvate, lactate dehydrogenase,

alcohol fermentation:
-pyruvate--------------->ethanal--------->ethanol
-co2 removed, (pyruvate decarboxylate), 2H added (ethanol dehydrogenase), rNAD->NAD,

-no ATP made, but glycolysis can continue,
-yeast is killed when the concentration of ethanol build up to around 15%,

Respiratory Substrate:
-is an organic substance that can be used for respiration,
-carbohydrate: respires very well, changes to glucose to respire,
-protein: de-animated, excess amino acid,
-the rest of it is changed to fat or glycogen, releases more energy than carbohydrates as the number of Hydrogen atoms per mole accepted by NAD,
-lipids: lots of carbon atoms and hydrogen atoms so lots of energy produced,

Reply 196

Original post by darkxangel

Sensory receptors:
-very long neurones
-cell surface membrane has many gated ion channels,
-sodium/potassium ion pumps that use ATP to actively transport ions,
-fatty myelin sheath,
-long dendrons,

ATP:
-adenosine (adenine + ribose)
-three phosphate groups,
-0..6kJmol released when ATP is hydrolysed and Pi leaves,
-immediate source of energy,
-max yield is rarely achieved,
-some protons leak across the membrane,
-some ATP used to transport pyruvate,
-some is sued to transport hydrogen from reduced NAD,

adrenaline:
pit binds to specific receptor on the cell surface membrane,
-adrenaline is the first messenger,
-activates enzyme adenyl cyclase,
-it converts ATP to cyclic AMP,
-The cAMP is the second messenger,
-it causes an effect by activating enzyme action,
-prepares body for activity,
-increases heart rate/mental awareness,
-dilate pupils, makes body hair erect,
-glycogen -> glucose,

Endocrine System:
endocrine gland:
-secretes hormones directly into the blood,
exocrine gland:
-secretes molecules into a duct that carries the molecules to where they are used,
hormone:
-released by endocrine glands, they act as messengers carrying a signal from one gland to a specific target organ or tissue,

Ectotherms:
-body temperature fluctuates with external temperature,
-expose/orientate body to sun,
-increase respiration,
-alter body shape,
-less food used in respiration, so can be used for growth,
-less active in cooler temperatures,

Endotherms:
-move into sunlight,
-orientate to increase surface area exposed to sun,
-move about to generate heat in muscles,
-thermo-regulatory centre in the hypothalamus monitors blood temperature,
-peripheral temperature receptors in the sun monitor the temperature in the extremities, if too cold or hot it will notify the brain,
-increase the rate if respiration - to release heat (liver),
-fairly constant body temperatures,
-more food required,
-sweat glands-heat released to evaporate the water in sweat,
-hairs lie flat-little insulation-more heat lost,
-vasodilation -> more heat lost,
-liver cells - less heat generated,
-skeletal muscles - no spontaneous contractions,

Respiration:
Why do we need to respire?:
-active transport,
-secretion,
-synthesis of molecules,
-replication of DNA,
-movement,
-activation of chemicals,

mitochondria:
-consists of outer membrane, inner membrane, matrix (link reaction + krebs cycle),
-cristae,
-inner membrane, impermeable to small ions including protons,
-electron carriers and ATP synthase enzymes,
-cristae-large surface area,
-has many electron carriers and ATP synthase,
-coenzyme FAD is tightly bound to an enzymes dehydrogenase, which is embedded in inner membrane,
-proton accepted by FAD pass into mitochondria matrix,

glycolysis:
-2 ATPs are hydrolysed, they attach to glucose -> activated fructose 1,6 biphosphate,
-energy from ATP activates hexose sugar and prevents it from being transported, hexose 1, 6 biphosphate,
-split into two triose phosphates,
-two hydrogen atoms are removed and accepted by NAD -> reduced NAD, two NAD- made 2 * ATP made,
-four enzyme catalysed reactions convert each triose phosphate into pyruvate,
-2 ATP,

Link reaction:
-acetate accepted by co-enzyme A, acetyl CoA forms,

Krebs cycle:
-acetate offloaded from CoA(2c), joins with oxaloate(4c) to form citrate,
-citrate is decarboxylated and dehydrogenated, rNAD + CO2,
-5C compound forms-> 4C compound->, rNAD + CO2,
-4C compound -> 4c compound, ADP +P-> ATP,
-4c COMPOUND-> 4C compound, rFAD,
-4C COMPOUND -> oxaloate, rNAD,

Oxidative Phosphorylation:
-O2 final e- acceptor,
-involves e- carriers found in cristae,
-complex/NADH-coenzyme Q reductase,
-protons go into solution in the matrix,
-as e- how along electron-transport chain, enery is released and used by coenzymes to pump protons across to the innermembrane space,
-which builds up a proton and pH gradient,
-potential energy build up,
-H ions can't diffuse through lipid part,
-as protons flow through ATP synthase enzyme, ATP is made,
-4h+ + 4e- +O2->2H2O,

chemiosmosis: the evidence:
-when isolated mitochondria is placed in solution of very low water potential, outer membrane is ruptured, releasing content of the intermembrane space,
-by further treating the resulting mitoblasts with strong detergents, they could rupture the inner membrane and release contents on matrix,
-electron transfer in mitoblasts didn't produce ATP, so they concluded that the intermembrane space was also involved,
-if the mushroom shaped parts of the stalked particles were taken away ATP wasn't made,

Anaerobic respiration:
lactate pathway:
pyruvate ---------------> lactate
rNAD---->NAD, 2H added to pyruvate, lactate dehydrogenase,

alcohol fermentation:
-pyruvate--------------->ethanal--------->ethanol
-co2 removed, (pyruvate decarboxylate), 2H added (ethanol dehydrogenase), rNAD->NAD,

-no ATP made, but glycolysis can continue,
-yeast is killed when the concentration of ethanol build up to around 15%,

Respiratory Substrate:
-is an organic substance that can be used for respiration,
-carbohydrate: respires very well, changes to glucose to respire,
-protein: de-animated, excess amino acid,
-the rest of it is changed to fat or glycogen, releases more energy than carbohydrates as the number of Hydrogen atoms per mole accepted by NAD,
-lipids: lots of carbon atoms and hydrogen atoms so lots of energy produced,

hi how are you :smile:

thanks for the notes really good ++reps can u ask me questions from chapter 1 to photosythesis

Reply 197

Original post by otrivine

hi how are you :smile:

thanks for the notes really good ++reps can u ask me questions from chapter 1 to photosythesis

if you are still here sure.

describe the light dependent and independent stage (10)

i'll mark it when i'm done doing my chem notes. :wink:

Reply 198