Module 5 Flashcards
What do sensory receptors act as.
Transducer- convert one form of energy to another.
Describe how pacinian corpuscles work
- They are mechanoreceptors that detect mechanical stimuli. They contain the end of a sensory neurone wrapped in layers of lamellae.
- When stimulated the lamellae become deformed and press on the nerve ending.
- The stretch mediated sodium channels in the cell membrane of the sensory neurone are deformed.
- Sodium ions diffuse into the cell, creating a generator potential.
- If the generator potential exceeds the threshold, an action potential is generated.
Describe sensory neurones and how they look
- short dendrites
- 1 long dendron: carries impulse from dendrites to cell body
- cell body is in the middle of the neurone and nucleus is in the cell body.
- 1 short axon: carries impulse from cell body to CNS
Describe motor neurone and how they look
- many short dendrites that branch of the cell body
- cell body is on one end, dendrites branch off it
- 1 long axon
Describe relay neurones and how they work
- many short dendrites: carry impulse from sensory neurone to motor neurone
- many short axons: carry impulses from cell body to motor neurone.
- cell body is smack bang in the middle with all the axons and dendrons coming off it like a starfish.
Describe how membranes in the human body stay polarised at rest, when no action potential is present.
- Resting potential is around -70mV
- Sodium - potassium pumps in the cell membrane move sodium out of the membrane
- The cell membrane is not permeable to sodium ions so there is greater positive charge outside the membrane
- Sodium - potassium pumps in the cell membrane also move potassium into the cell across the membrane.
- The cell membrane is permeable to potassium ions so the potassium ions that have just been pumped in can diffuse right back out through potassium ion channels
- There is always a more positive charge outside the cell than inside.
Describe the changes in potential difference across a membrane during an action potential
- Stimulus
- sensory neurone excited, sodium ion channels are open in the cell membrane
- sodium ions move in from the outside of the cell making the inside of the cell more positive - Depolarisation
- voltage gated sodium ion channels open when the voltage difference is around -55mV.
- more sodium floods into the cell
- example of positive feedback
- is the big rising part of the graph
- some of the sodium diffuses in sideways to trigger the next part of the neurone membrane. - Repolarisation
- sodium ion channels close at +30mV
- voltage gate potassium ion channels open
- more potassium ions flood out of the cell.
- the outside of the cell is slowly becoming more positive again
- example of negative feedback - Hyperpolarisation
- potassium ion channels are slow to close so there’s some overshoot where too many potassium ions diffuse out
- voltage becomes lower than resting - Resting potential
- ion channels are reset
- sodium potassium pump returns the ions back to their original places.
The refractory period is the period of time where the neurone cannot be excited again due to the ion channels recovering.
Describe the myelin sheath. What is it made of and where can it be found.
It’s an electrical insulator. It is made of a Schwann cell. The myelin sheath is found in the PNS. Between each Schwann cell there is a node of Ranvier which is used in saltatory conduction which is very fast. Depolarisation in myelinated neurones only happen at the nodes of ranvier.
Describe cholinergic synapses
- use the neurotransmitter acetylcholine
- bind to cholinergic receptors
- broken down by an enzyme called acetycholinesterase
How do neurotransmitters transmit nerve impulses between neurones?
- Action potential arrives at presynaptic neurones triggering voltage gated calcium ion channels to open.
- The calcium ions diffuse into the synaptic knob and will be pumped out after.
- Presence of calcium ions cause the presynaptic vesicles containing neurotransmitters to move towards the membrane.
- The vesicles release the neurotransmitter via exocytosis
- When the neurotransmitter binds to the receptors on the postsynaptic neurone, the sodium ion channels also open.
- As sodium ions move into the postsynaptic membrane, depolarisation occurs and the neurotransmitter is removed from the synaptic cleft.
What is synaptic convergence and divergence
Divergence:
- one neurone connects to many
- info is dispersed to different parts of the body
Convergence:
- many neurones connect to one
- impulse is amplified.
What are the 2 types of summation of action potentials and what are they
Spatial:
- neurones converge
- action potentials from many neurones can reach threshold of one neurone
- stimuli arrive from multiple sources
Temporal summation:
- two or more impulses arrive in quick succession from the same presynaptic neurone.
- impulse is likelier to be generated in the postsynaptic because there’s more neurotransmitter.
Describe the way that secondary messengers work using the example of adrenaline and the liver.
- Adrenaline is the first messenger which binds to the receptors on liver cells.
- Upon binding, adrenaline activates an enzyme called andenylyl cyclase which catalyses the production of the secondary messenger: cyclic AMP from ATP
- Cyclic AMP activates a cascade of reactions such as breakdown of glycogen to glucose for negative feedback.
Describe the structure of the adrenal glands and describe what types of hormone each of the structures produce.
It’s made of the cortex (outside) and medulla (inside).
Cortex:
- secretes steroid hormones in response to stress, eg. Cortisol, and aldosterone
- short term and long term effects
- effects of these hormones are: breakdown of proteins and fats to glucose to increase amount of energy available; increase blood volume and pressure by increasing sodium ion and water uptake in kidneys; suppressing immune system.
Medulla:
- secretes catecholamine hormones (modified amino acids) in response to stress. Eg. Adrenaline and noradrenaline
- short term effects
- effects of these hormones are: increasing breathing and heart rate; causing cells to breakdown glycogen and glucose; constricting some blood vessels to allow more blood flow to the vital organs.
Describe the endocrine function of the pancreas (under the stomach)
- contain endocrine tissue called the islets of langerhans which appear as paler patches (like lightening) under a microscope.
- contain alpha cells which secrete the hormone glucagon, usually a pink stained cell
- contains beta cells which secrete the hormone insulin, usually a purple stained cell
- both alpha and beta cells are found in clusters around blood capillaries, differential staining is required to see the difference between the alpha and beta cells.
Which part of the brain is responsible for temperature regulation of the body, give some examples of the way that humans regulate body temperature.
Hypothalamus. Humans regulate by shivering, sweating, vasodilation, piloerection. We are endotherms.
Describe the interaction of alpha cells and beta cells to regulate blood glucose
Alpha cells - produce glucagon:
- glucagon binds to specific receptors that break down glycogen into glucose (glycogenolysis)
- glucagon promotes the breakdown of amino acids and fatty acids to glucose (gluconeogenesis)
Beta cells - produce insulin:
- insulin binds to receptors and activates enzymes that convert glucose to glycogen (glycogenesis)
- cells store glycogen as an energy store
Describe the depolarisation mechanism of beta cells that causes them to release insulin.
- In high blood glucose, more glucose facilitatedly diffuses into the cell which makes the cell respire more and produce more ATP.
- More ATP triggers potassium ion channels to close so they aren’t pumped out of the cell membrane anymore and they build up a positive charge on the inside of the cell which is depolarisation.
- Depolarisation triggers calcium ion channels to open in the membrane so calcium ions flood the cell
- When calcium ions flood the cell, the vesicles containing insulin move towards the membrane, fuse and release the content by exocytosis.
What are the functions of the liver?
Break down excess amino acids:
- nitrogen containing compounds can’t be stored by the body, deamination occurs forming ammonia and organic acids by removing the amino group from amino acids
- ammonia is too toxic to excrete directly, so it’s combined with CO2 in the ornithine cycle to create urea:
1. NH3 + CO2 —> carbamoyl phosphate
2. Carbamoyl phosphate —> citruline
3. Citruline + ATP + aspartate —> argininosuccinate + AMP + water
4. Argininosuccinate —> arginine
5. Arginine + water —> urea + ornithine
- urea is released from the liver to the blood where it’s filtered by the kidneys to make urine.
Breaks down harmful substances like alcohol (leads to liver cirrhosis); paracetamol (kidney/liver failure); insulin (messes with blood sugar concentration)
Stores glycogen as granules in cells.
Describe the functions of the hepatic artery, hepatic vein, hepatic portal vein and bile duct.
Hepatic artery: supplies liver with oxygenated blood
Hepatic vein: takes deoxygenated blood away from the liver
Hepatic Portal Vein: brings blood from the duodenum in the intestine for filtration
Bile duct: takes bile (substance that emulsifies fat made by liver) to the gall bladder for storage.
Describe the structure of the general liver
- Made of liver lobules.
- The liver lobules are made of cells called hepatocytes arranged in rows from the centre, like a starfish.
- Each lobule has a central vein that connects to the hepatic vein.
- Lots of branches of the hepatic artery, hepatic portal vein and bile duct are found in each lobule. They make up the portal triad.
Describe the structure of the sinusoid
- sinusoids are the capillaries that connect the vessels in each lobule
- sinusoid is carries blood to the central vein
- kupffer cells line the walls of the sinusoids to remove bacteria and break down old red blood cells.
- canaliculi connect the bile duct to the central vein
- under a microscope, it looks like stretch marks where the darker parts are the hepatocytes and the white parts are the sinusoids
Where does ultrafiltration occur, what are the names of the arteries that supply it and why are they different to each other.
The glomerulus
The afferent arteriole brings in blood, it has a wider lumen
The efferent arteriole takes away blood, it has a smaller lumen to ensure a high pressure so small molecules and liquids can be squeezed out.
What 3 layers do the small molecules and liquids have to get past to get to the bowman’s capsule?
Capillary wall of glomerulus
Basement membrane
Epithelium of bowman’s capsule
Large molecules like blood cells and proteins cannot pass through.
Name the nephron structures in order of filtration
- Glomerulus
- Bowman’s capsule
- PCT
- Descending loop of Henle
- Ascending loop of Henle
- DCT
- Collecting duct
- Ureter
What is reabsorbed in the PCT and how is the PCT adapted for its function
Glucose; amino acids; vitamins and some salts are reabsorbed.
It’s adapted because it has microvilli on its epithelium surface to maximise area for re absorption
What is reabsorbed in the DCT and collecting duct?
Water
Describe the mechanism of re absorption in the loop of Henle
It’s a countercurrent multiplier mechanism.
- At the top of the ascending limb, sodium and chlorine ions are pumped out of the loop. This part of the loop is impermeable to water so water stays in the loop and there is less water outside the loop.
- At the bottom of the descending limb which is permeable to water, the water moves out because there’s less water outside the loop so the filtrate is more concentrated.
- At the bottom of the ascending limb, sodium and chlorine ions again diffuse out of the loop but at this point, the loop is again not permeable to water so water stays. Then the water will again be reabsorbed in the DCT and collecting duct.
Do animals that live in hotter areas have longer or shorter loops of Henle and why?
Longer loops of Henle to maximise water re absorption.
Describe how water re absorption is controlled by hormones
It’s detected by the hypothalamus which sends impulses to the posterior (backside) pituitary gland to release ADH.
ADH makes the walls of the DCT and collecting duct more permeable to water by increasing the number of aquaporins.
Hydrated = less ADH
Dehydrated = more ADH
Describe how pregnancy tests work
- Stick has an application area where you pee where there are monoclonal antibodies for hCG (hormone only present in pregnant women) bound to a coloured bead (blue).
- Urine applied and hCG binds to the antibodies, urine moves up the strip carrying the antibody with it.
- The strip has antibodies of hCG that are immobilised and when hCG is present, the strip turns blue due to immobilised enzymes binding to the blue beads.
Describe the way that the nervous system is organised.
CNS and PNS
|
/ \
Somatic. Autonomic
|
/ \
Sympathetic Parasympathetic
- somatic: controls conscious activities
- autonomic: controls unconscious activities
- sympathetic: fight or flight
- parasympathetic: rest and digest, uses acetylcholine
What are the 5 main structures of the brain
- Hypothalamus
- found beneath the middle part of the brain
- autonomically maintains body temperature
- produces hormones that control the pituitary gland - Cerebrum
- largest part of the brain
- divided into 2 halves
- thin outer layer called the cerebral cortex which is highly folded
- involved in vision, hearing, learning and thinking - Pituitary gland
- found beneath the hypothalamus
- controlled by the hypothalamus and releases other hormones that stimulate a variety of glands - Medulla Oblongata
- base of the brain
- controls breathing and heart rate - Cerebellum
- underneath the cerebrum
- has a folded cortex
- important for muscle coordination, posture and coordination of balance
Describe the negative feedback for blood pressure
- Baroreceptors in the walls of arteries detect pressure
- Impulses are sent to the medulla oblongata which sends impulses to either vagus nerve (secretes acetylcholine which binds to receptors on SAN to slow down heart rate) or accelerans nerve (secretes noradrenaline which binds to SAN to increase heart rate)
- Adrenaline release can also result in increase of heart rate for fight or flight response
Describe the negative feedback for blood pH regulation
- Chemoreceptors in the walls of artery detect pH of blood
- Impulses are sent to the medulla oblongata which sends impulses across the vagus or accelerans nerve to increase of decrease heart rate to bring levels back to normal.
- High pH means low CO2 levels and high O2 levels and vice versa.
Is skeletal muscle striated?
Yes
Describe the structure of the muscle’s muscle fibres.
- Muscle
- Muscle fibre with membrane called sarcolemma, have many mitochondria, are multinucleate, have many myofibrils made of proteins that are specialised for contraction.
- Transverse T tubules that stick into the sarcoplasm to distribute impulse everywhere
- Sarcoplasmic reticulum which run through the sarcoplasm, they store calcium ions needed for contraction.
Describe the sarcomere
Makes up myofibrils
Made of thin and thick myofilaments: Actin (thin, light, I band) and myosin (thick, dark, a band)
M line is right in the middle of the sarcomere
2 Z lines are at the end of the sarcomere
H zone around the M line only contains myosin filaments
Describe the arrangement of actin and myosin at rest
Myosin filaments have globular, hinged heads that can move back and forth.
Each myosin head has 2 binding sites: one for actin, one for ATP.
Actin filaments have binding sites for myosin heads called actin-myosin binding sites. At rest, this site is blocked by a protein called tropomyosin which is held in place by troponin. This means that myofilaments can’t slide past each other because the myosin heads can’t bind.
Describe how muscle contraction is triggered by action potentials
- Sarcolemma is initially depolarised, the depolarisation spreads down the T tubules to the sarcoplasmic reticulum
- The sarcoplasmic reticulum releases stored calcium ions into the sarcoplasm.
- Calcium ions bind to troponin making it change shape.
- The tropomyosin can no longer bind to the actin myosin binding site. This allows the myosin head to bind, forming an actin-myosin cross bridge
- Calcium ions activate ATPase which breaks down ATP to provide energy needed for muscle contraction
- Energy released by ATP moves the myosin head and pulls the actin filament along.
- ATP provides energy to break the actin myosin cross bridges to allow muscle contraction to happen again.
Describe the ATP-Creatine Phosphate System
ATP is made by phosphorylation of ADP, you add a phosphate group taken from creatine phosphate
CP is stored in cells and the ATP-CP system generates ATP very quickly.
CP runs out after a few seconds so it’s used for short bursts of vigorous exercise.
The ATP-CP system is anaerobic
Describe the 3 types of muscle and their properties
Skeletal (Voluntary)
- controlled consciously
- have many nuclei
- are striated
Smooth (Involuntary)
- controlled unconsciously
- doesn’t have a striated appearance
- contract slowly doesn’t fatigue
Cardiac (heart)
- myogenic: contracts on its own
- rate of contraction is controlled by autonomic nervous system
- muscle fibres are connected by intercalated disks with low electrical resistance
- branched muscle fibres
- don’t fatigue
What device is used to record electrical activity in muscles
Electromyogram
Describe some specific chemical defences that plants may have
Alkaloids: chemicals with bitter taste, bad smell or poison
Tannins: taste bitter
Describe the way that shoots and roots are phototrophic and geotrophic
Shoots: positively phototrophic and negatively geotrophic
Roots: negatively phototrophic and positively geotrophic
Describe some growth hormones of plants
Gibberellin: stimulates seed germination, stem elongation, side shoot formation and flowering.
Auxins: responsible for cell elongation
- indoleacetic acid: moves by diffusion and active transport to other parts of the plant via the phloem to stimulate cell elongation
- stimulate the growth of apical buds and inhibits growth of side shoots
Ethene
- stimulates leaf loss
Abscisic acid
- triggers stomatal closure
Describe how hormones are involved in stomatal closure
- Abscisic acid triggers stomatal closure
- ABA binds to receptors on guard cell membranes
- Ion channels open and calcium ions move into cytosol from the vacuole.
- More calcium ions in the cytosol triggers even more ion channels to open
- More ions leave so water also leaves via osmosis and the cells are flaccid so the stomata is closed.
Describe the cellular organisation of chloroplasts from biggest to smallest
Chloroplast
Outer membrane
Inner membrane
Stroma
Granum
Lamella
Thylakoid
Circular DNA
What kinds of pigments do photosystems have, and what are each of their uses. Give examples of commonly found pigments.
Primary pigments: reaction centres for exciting electrons
Accessory pigments: make up light harvesting systems that surround reaction centres and transfer photons for more excitement.
Some examples are: chlorophyll a, chlorophyll b, carotene. Chlorophyll a is a primary pigment whereas chlorophyll b and carotene are accessory pigments
Describe each of the photosystems in photosynthesis
PS1 - second in the chain, absorbs light best at 700nm
PS2 - first in the chain, absorbs light best at 680nm
Describe non cyclic photophosphorylation
- Light energy excites electrons in chlorophyll of PS2, electrons move to a higher energy level in the reaction centre and are passed onto the electron transport chain. If too much light energy has been absorbed, plants release it by emitting fluorescent light, this is called chlorophyll fluorescence.
- Excited electrons leave from PS2 and move along the electron transport chain, they continue to be replaced. Light energy also makes water go through photolysis to make protons and oxygen.
- The electrons lose energy as they move along the electron transport chain. The energy lost is used to pump H+ from the stoma into the thylakoid via proton pumps to form a proton gradient. Protons move into the stroma again via ATP synthase which catalyses phosphorylation of ADP. This is called chemiosmosis.
- Light energy is absorbed by PS1 and electrons are excited to an even higher energy level. The electrons are transferred to NADP along with a H+ from the stroma to form NADP.
Describe cyclic photophosphorylation
Only uses PS1
Electrons are recycled back to PS1
Process only produces small amounts of ATP
Describe the light independent stage of photosynthesis
It’s also called the Calvin cycle, takes place in the stroma
- Carbon dioxide is combined with ribulose bisphosphate (5C) using Ribulose Bisphosphate Carboxylase (RuBisCO) to give an unstable compound (6C) which immediately breaks down into 2 molecules of glycerate 3-phosphate (3C)
- ATP is used to turn glycerate 3-phosphate to triose phosphate (TP). This reaction uses NADPH’s H+ ion. TP is converted to more useful organic compounds
- 5 of every 6 molecules of TP are used to regenerate RuBP, this process uses the rest of the ATP made by the light dependent reaction
The Calvin cycle must occur 6 times to make one hexose sugar.
What are the 4 stages of aerobic respiration?
- Glycolysis: occurs in cytoplasm of cells and is an anaerobic process
#Stage 1 - phosphorylation
- glucose is phosphorylation by adding 2 inorganic phosphates from ATP producing 2 ADP and one hexose bisphosphate
- hexose bisphosphate is split into 2 triose phosphate
#Stage 2 - Oxidation
- triose phosphate is oxidised forming 2 pyruvate, the pyruvate is actively transported into the matrix of the mitochondria.
- 2 NADH is made which go to the oxidative phosphorylation stage
- net 2 ATP made - Link reaction
- occurs in the mitochondrial matrix
- pyruvate is decarboxylated (one carbon is removed in the form of CO2) and dehydrogenated (It loses a hydrogen to NAD) to form acetate
- acetate is combined with coenzyme A to produce acetyl coenzyme A.
- no ATP made
- occurs twice for each glucose molecule respired - Krebs cycle: occurs in the mitochondrial martix
- acetyl coenzyme A combines with oxaloacetate to form citrate using citrate synthase. CoA goes back to link reaction
- citrate is converted to a 5C molecule via decarboxylation and dehydrogenation
- 5C converted to a 4C called oxaloacetate, this process produces 2 NADH and 1 FADH2.
- occurs twice for each glucose molecule
- 2 ATP made per glucose - Oxidative phosphorylation
- occurs in the inner mitochondrial membrane
- hydrogen released from NADH and FADH2, they split to form H+ and e-.
- e- travel along the inner mitochondrial matrix cristae via electron carrier proteins just like in photosynthesis.
- energy released by the movement of the electrons is used to pump electrons from mitochondria matrix to inter membrane space to form an electrochemical gradient.
- H+ moves back via ATP synthase which is used in the phosphorylation of ADP to make ATP, this is chemiosmosis
- water is made finally and O2 is the final electron acceptor
32 ATP is made overall in aerobic respiration per molecule of glucose:
7 from glycolysis (x1)
5 from link reaction (x2)
20 from Krebs cycle (x6)
What are the two type of anaerobic respiration, describe each
Alcoholic fermentation
- CO2 removed from pyruvate to produce ethanal
- ethanal gains a H+ from NADH to make ethanol
- can occur in plants
Lactate fermentation
- pyruvate converted to lactic acid using H+ from NADH
How many ATP are made from anaerobic respiration
2
The more hydrogen atoms there are per unit of mass, the more ATP is made when respired
What is the RQ and how do you calculate it. State the RQ values and average energy values of carbohydrates, lipids and proteins. State what low or high RQ values mean
Respiratory quotient is the volume of CO2 made when a substrate is respired.
Volume of CO2 released / volume of O2 consumed
Respiratory substrate | average energy value | RQ
————————————————————————
Carbs. | 15.8 kJ/g | 1
——-——————————————————————
Lipids | 39.4 kJ/g | 0.7
————————————————-————————-
Proteins | 17 kJ/g | 0.9
High RQ value = >1 = organism is short of oxygen and is respiring anaerobically and aerobically
Low RQ value in a plant = CO2 released is also being used for photosynthesis.
