Topic 7: Run For Your Life

Question 1

Describe how a muscle contracts

Answer 1

A nerve impulse causes the release of acetylcholine. Ca ions are released into the sarcoplasm. Ca2+ attaches to the troponin molecule, causing troponin and tropomyosin to move, exposing myosin binding sites on the actin filaments.

The myosin head binds w the myosin binding sites to form cross bridges. As this occurs ATP and Pi are released, allowing the myosin head to change shape, nodding forward. This makes actin move over the myosin towards the centre of the sarcomere. The sarcomere shortens.

ATP binds to the myosin head, detaching it from the actin. ATPase on the myosin head hydrolyses ATP to ADP and Pi. This reverts the myosin head to OG shape, ready for the next power stoke.

The collective bending of many myosin heads moves the actin filaments relative to the myosin filament resulting in muscle contraction

Question 2

Why do muscles work in pairs?

Answer 2

Muscles can only contract, so pull not push. Therefore they work in antagonistic pairs to bring about movement.

Question 3

What is the endosymbiotic theory?

Answer 3

Millions of yrs ago ancestors of mitochondria existed as aerobically respiring bacteria.

The 1st eukaryotic cells evolved when these aerobic bacteria invaded anaerobic bacteria.

The fact that mitochondria have their own DNA supports this theory.

Question 4

where does aerobic respiration and glycolysis take place?

Answer 4

Respiration occurs in mitochondria Glycolysis occurs in the cytoplasm

Question 5

What happens from anaerobic to aerobic respiration?

Answer 5

In anaerobic resp, pyruvate produced by glycolysis is converted to lactate. This allows glycolysis to continue, releasing some energy. Lactic acid dissociates into H+ and lactate ions, slowing enzymes involved in glycolysis.

The muscle proteins can change shape which interferes with muscle contraction- muscles feel painful.

Then 2 things can happen: pyruvate is oxidised, releasing energy to produce ATP. This is aerobic resp. OR Pyruvate is converted back into glucose and glycogen in the muscles and liver this needs energy.

Question 6

Describe and explain glycolysis

Answer 6

Glycolysis: a series of anaerobic enzyme catalysed reactions in the cytoplasm. Glucose is made more reactive by adding 2 phosphates in phosphorylation. The 2 phosphates come from the hydrolysis of 2ATP molecules to ADP which has an input of energy. Fructose bisphosphate forms.

Fructose bisphosphate splits into 2 3C molecules which each have 1 phosphate. These 3C molecules are oxidised: hydrogen is removed and added to NAD, forming NADH. (Each NADH molecule will enter the ETC to form more ATP). This is dehydrogenation and forms a 3C sugar w 2 attached phosphates.

Then hay 2 rounds of dephosphorylation. The phosphates are added to ADP to form ATP to form a 3C pyruvate. So the overall products are: 2 ATP, 2 NADH and 2 pyruvates

Question 7

What happens in the link reaction?

Answer 7

In aerobic resp, the pyruvate produced by glycolysis enters the mitochondrial matrix. Here the link reaction occurs. Pyruvate first is converted to acetate.

Then: Acetate + NAD+ + CoA —> acetylCoA + NADH + C02.

Acetyl-CoA, a 2C molecule, then enters the Krebs cycle.

Question 8

Describe the Krebs cycle

Answer 8

In the Krebs cycle, acetyl-CoA combines with oxaloacetate to form citrate. A sequence of enzyme catalysed reactions take place, where citrate is converted back to oxaloacetate.

The cycle produces 3 NADH molecules, 1 FADH2 molecule and directly produces 1 ATP molecule. Each NADH molecule can give rise to 3ATP molecules, 1 FADH2 molecule can give rise to 2 ATPs by oxidative phosphorylation in the ETC.

So 9 + 2 +1 = 12 ATPs produced from the Krebs cycle from 1 acetyl-CoA. As glucose can give rise to 2 acetyl-CoAs, 24 ATPs can be produced from the Krebs cycle from 1 glucose.

Question 9

What is oxidative phosphorylation and the ETC?

Answer 9

NADH gives its e- to complex I, getting oxidised back to NAD+. FADH2 gives its e- to Complex II. E-s from the complexes flow down a chain of e- carriers in the mitochondrial membrane.

Energy is released as electrons pass along the ETC. This energy is used to move H+ ions from the mitochondrial matrix into the intermembrane space, creating a steep electrochem gradient across the inner membrane.

H+ diffuse down this gradient via protein channels joined to ATP synthase. H+ ions change the enzyme a.s shape, allowing ADP and phosphate ions to bind. ADP is phosphorylated to ATP, catalysed by ATPsynthase

W/in the matrix, the H+ and e-s recombine to form H2. These combine with 02 to form 2H20. 02= final e acceptor.

Question 10

What happens in the absence of oxygen?

Answer 10

Some cells anaerobically respire. Sin 02, the ETC cannot function, hydrogen acceptors accumulate in the cell.

All of the NAD would be converted to NADH and all of the FAD to FADH2. Metabolism would stop.

Question 11

What is the effect of lactate buildup?

Answer 11

H+ ions from lactate which accumulates in the cytoplasm neutralise negatively charged aa groups in the a.s of the enzyme.

This affects attraction between charged groups on the substrate and active site. Substrate ya no puede bind.

Question 12

How is lactate removed?

Answer 12

After anaerobic resp most lactate is converted back to pyruvate. It is oxidised to C02 + H20 via the Krebs cycle, releasing energy to make ATP. 02 is needed in oxidation of lactate.

Therefore O2 uptake is greater than normal in the recovery period after exercise to repay O2 debt (or post exercise O2 consumption).

Some lactate may also be converted to glycogen to store.

Question 13

State the products formed during anaerobic respiration of yeast

Answer 13

During anaerobic respiration, yeast produces ethanol and carbon dioxide instead of lactate.

Question 14

How does ATP control respiration?

Answer 14

ATP inhibits the first step of glycolysis. In the presence of ATP, the enzyme for glucose phosphorylation has an inactive shape.

As ATP is broken down the enzyme is converted back to the active form and catalyses phosphorylation of glucose again.

This is end point inhibition: end product inhibits an early step, so controlling the whole pathway.

Question 15

Describe fatty acid oxidation

Answer 15

Fatty acids can also be respired to release much more ATP than glucose.

The fatty acids are broken down in a series of reactions to form several 2C compounds which enter the Krebs cycle.

Bc fatty acids can only be respired via Krebs, fatty acids are only used for aerobic respiration.

Question 16

What energy systems generate ATP?

Answer 16

Aerobic respiration, anaerobic respiration, ATP/PC system. Sometimes oxygen is not delivered to respiring cells fast enough so other energy systems are needed.

Question 17

Describe the ATP/PC system

Answer 17

Muscle cells store small quantities of ATP in the form of creatine phosphate (PC). PC is hydrolysed to provide energy to regenerate ATP.

creatine phosphate —> creatine + Pi

ADP + Pi —> ATP

Overall: PC + ADP —> Creatine + ATP

Reactions don’t need 02 and provide energy for 6-10s of intense exercise, eg sprinting

Question 18

Describe a practical to measure the rate of respiration

Answer 18

Assemble the respirometer. Add 5g of one organism to the boiling tube and replace the bung.

W a dropping pipette, drop coloured fluid in the open end of the respirometer. Open the 3- way tap to the syringe to draw the fluid far from the respirometer. Record its starting position w a pen.

Close the tap to isolate the respirometer. Start stop clock, mark the position of the fluid every min for 5 mins.

Open the tap. Record the end position of the coloured fluid. Calculate the mean rate of 02 uptake during the 5 mins.

Question 19

What is V02 and V02 max?

Answer 19

V02: volume of oxygen breathed per minute at rest.

V02 max: volume of oxygen produced in during maximal aerobic exercise (ml min^-1 Kg^-1)

Question 20

How is adequate oxygen supply maintained during exercise?

Answer 20

It is maintained by: increased cardiac output, increased breathing rate, deeper breathing, redistribution of blood away from some organs to striated muscles.

Cardiac output= HR (bpm) x stroke volume

Question 21

What is stroke volume?

Answer 21

The volume of blood pumped out the left ventricle each time the ventricle contracts in cm^3.

For most adults at rest this is 50 to 90 cm^3

Question 22

Describe stroke volume and venous return.

Answer 22

During exercise increased muscle contraction means more blood returns to the heart in venous return.

In diastole during exercise the heart fills with a larger volume of blood.

Heart muscle is stretched to a greater extent, so it contracts more forcefully, so more blood is expelled. This increases stroke volume and cardiac output.

Question 23

Differences in resting heart rate are caused by…

Answer 23

…heart size due to body mass and genetics.

Larger heart = lower bpm bc it expels more blood with each beat, so doesn’t need to beat as frequently.

Endurance training thickens heart muscle walls and therefore heart size.

Question 24

Describe the SAN

Answer 24

SAN- Sino atrial node. Consists of specialised muscle fibres. Located in right atrium wall beneath the opening to the superior vena cava. The SAN initiates the heartbeat.

Depolarisation starts at the SAN, generating an impulse. The impulse spreads across the right and left atria. L and R atria contract al mismo tiempo. Impulse reaches AVN. Rate of contraction varies by hormonal or nervous simulation.

Question 25

Describe the AVN

Answer 25

Specialised muscle fibres. AVN transmits signals to the base of the heart via a His-Purkinje system.

0.13 second delay so that atria can contract and empty blood prior to ventricles. This prevents pooling of blood in atria which would form clots. The delay also allows ventricles to fill, increasing SV and COpt

From the AV node in the right atrium, the depolarisation wave travels through the bundle of His, and then to the Purkinje fibres. Purkinje fibers spread the depolarisation wave to the rest of the heart.

This makes the ventricles contract in a coordinated way and expel blood to the pulmonary artery and aorta.

Question 26

What is an ECG?

Answer 26

An ECG measures electrical current on the skin when there is a change in polarisation of cardiac muscle. Electrodes are attached to a persons chest and limbs.

During a heart attack the rhythm of contractions changes, called arrhythmias. ECGs detect and diagnose these.

Question 27

Describe the peaks you would see on an ECG

Answer 27

P-wave: electrical charge spreading across the atria. Depolarisation of SAN and other tissue in the atrium.

QRS complex: charge spreading upwards through ventricles (spread of excitation through the ventricles)

T-wave: period when the ventricles relaxing and returning to their resting state. Rapid repolarisation of Purkinje tissue in ventricles.

Question 28

Explain the following terms:

Ischaemic, bradycardia, tachycardia.

Answer 28

Ischaemic: part of the heart is starved of oxygen during a heart attack due to atherosclerosis.

Bradycardia: heart rate of less than 60 BPM. Causes may be hypothermia, heart disease, use of medicines/drugs. Common in fit athletes at rest.

Tachycardia: heart rate greater than 100bpm. Causes may be anxiety, fear, fever, exercise, coronary heart disease, heart failure, fluid loss, anaemia, using medicines/drugs.

(I use affechfam to remember this)

Question 29

Explain the link between the nervous system and heart rate

Answer 29

Autonomic nervous system controls involuntary actions from the cvcc. It’s divided into sympathetic and parasympathetic (vagus nerve) systems. Motor nerve endings from each system connect to the SAN (natural pacemaker.)

Sympathetic: accelerator, increases strength and rate of heartbeat. Noradrenaline used as a transmitter substance. Activated by activity and stress. Stimulation of the sympathetic nervous system increases venous return, stroke volume and COpt. 02 also transported faster to muscles.

Parasympathetic: decelerator, lowers strength + rate of heartbeat. ACh used as a transmitter substance. Controls routine activities at rest.

Question 30

Describe the role of the cardiovascular control centre and controlling heart rate.

Answer 30

The cardiovascular control centre (cvcc) detects: C02, lactate, reduced 02, increased temp. Sensory receptors in muscles detect mechanical activity and send impulses to the cardiovascular centre, resulting in increased heart rate.

BP increases w increased cardiac output. In response Pa receptors in the aorta and carotid artery send impulses back to the cvcc. Inhibitory impulses are sent from here to the SAN. This avoids excessive increase in BP through negative feedback, which prevents further rise in heart rate.

Question 31

What is adrenaline?

Answer 31

Adrenaline is released during fear/shock/excitement from adrenal glands located above the kidneys.

Adrenaline directly affects the SAN, increasing heart rate to prep for likely physical demands.

Adrenaline causes dilation of arterioles supplying skeletal muscles and constriction of arterioles for non-essential organs/digestive system. This maximises bloodflow to active muscles.

Question 32

Describe tidal volumes, vital capacity and spirometers

Answer 32

During exercise, we increase our tidal volumes and breathing rate. The maximum volume of air we can inhale amd echale is our vital capacity

Tidal volume, vital capacity and rate of 02 consumption can be measured w a spirometer.

To find rate of 02 consumption, work out the decrease in volume between the two points on the trace- this is volume of 02 used. Divide this by time for the fall in seconds.

Question 33

At rest, a person takes 12 breaths per min. Assuming a tidal vilume of 0.5dm3, calculate the minute ventilation

Answer 33

Miniute ventilation is the volume of aie taken into the lungs in 1 mon. Calculate this as breathing rate x tidal volume:

12 x 0.5 = 6 dm^3 min-1

Question 34

Descibe how air is inhaled and exhaled in the lungs

Answer 34

The ventilation centre sends impulses every 2-3s to external intercostal and diaphragm muscles which contract to cause inhalation. Neck and upper chest muscles also contract in deep inhalation.

As lungs inflate, it stimulates stretch receptors in the bronchioles which send inhibitory impulses back to the ventilation centre. Impulses to the muscles stop and muscles relax, stopping inhalation.

Exhalation is caused by the elastic recoil of the lungs and by gravity helping lower the ribs. Not all of the air in the lungs is exhaled w each breath; residual air mixes w air inhaled.

Internal intercostal muscles only contract during deep exhalation, leaving less residual air in the lungs.

Question 35

A small increase in blood carbon dioxide concentration causes a large increase in ventilation.

How does this happen?

Answer 35

CO2 dissolves in the blood plasma, making Carbonic acid. Carbonic acid dissociates into H+ and HCO3- ions, lowering pH of blood.

Chemoreceptors sensitive to H+ ions are located in the ventilation centre of the medulla oblongata, detecting rise in H+. Impulses are sent from the ventilation centre to stimulate muscles involved in breathing. Ventilation increases.

Also hay chemo receptors in the walls of the carotid artery and aorta. These monitor the blood before it reaches the brain and send impulses to the ventilation centre.

Question 36

Why does increased concentration of carbon dioxide in the blood lead to increased breathing rate and depth?

Answer 36

Lower pH increases rate and depth of breathing through mas frequent and stronger contraction of muscles.

Mas frequent y deeper breaths maintain a steep conc gradient of CO2 between the alveolar air and the blood. This ensures efficient removal of CO2 from the blood and uptake of oxygen in the blood.

The opposite response occurs with a decrease in carbon dioxide. This is an example of negative feedback.

Question 37

How is breathing controlled during exercise?

Answer 37

The motor cortex in the brain controls movement. Upon exercise, impulses from the motor cortex directly affect the ventilation centre in the medulla oblongata, sharply increasing ventilation. Ventilation is also increased in response to impulses from stretch receptors in tendons/muscles involved in movement.

The various chemoreceptors sensitive to CO2 levels and changes in blood temperature increase the depth and rate of breathing via the ventilation centre.

Also hay receptors sensitive to changing oxygen concentrations in the blood but they are rarely stimulated under normal circumstances.

Question 38

What are slow twitch muscle fibres?

Answer 38

Slow twitch fibres are specialised for slower, usustained contraction. To do this they carry out mucho aerobic resp. Tienen mucho mitochondria and myoglobin

Myoglobin has a high 02 affinity and only releases it hay v low 02 conc in the cell, thus acting as an oxygen store dentro muscle cells.

Slow twitch fibres are associated with numerous capillaries to ensure good oxygen supply.

Question 39

What are fast twitch muscle fibres?

Answer 39

Fast twitch muscle fibres produce rapid, intense contractions. The ATP used in these contractions is produced almost entirely from glycolysis. Fast twitch fibres have few mitochondria and myoglobin. This means hay rapid lactate buildup so the fibres fatigue easily.

Question 40

How is glycolysis controlled?

Answer 40

Enzymes controlled by endpoint inhibition exist in an active or inactive form. In the active form, the substrate can fit into the a.s.

When ATP levels in the cell rises, it binds to phosphofructokinase, changing the shape of the enzyme which changes the a.s shape. Further glycolysis is inhibited.

Binding of an activator changes enzyme shape- for phosphofructokinase the activator is ADP (produced when ATP is broken down in the cell). Enzymes controlled in this way w 2 diff shapes are allosteric

Question 41

describe thermoregulation

Answer 41

Receptors in the hypothalamus detect changes in blood temp. Heat loss/gain centre in the hypothalamus sends impulses turning on effectors to return temperature to normal.

Heat loss centre stimulates sweat glands to secrete sweat. It inhibits: contraction of arterioles in skin, hair errector muscles, liver (reduces metabolic rate), skeletal muscles (so no shivering).

Vice versa for heat gain centre

Question 42

draw and label a diagram of the skin

Answer 42

insert image

Question 43

What is vasoconstriction?

Answer 43

In the cold, muscles in the arteriole walls contract, causing arterioles to constrict, reducing blood supply to the surface capillaries.

Blood is diverted through the shunt vessel which dilates (widens) as more blood flows through it. Blood flows further from the skin surface so less energy is lost. This is vasoconstriction.

Question 44

What is vasodilation?

Answer 44

In warm conditions the shunt vessel constricts and arteriole muscle walls relax. Blood flows through the arterioles, making them dilate. More blood flows closer to the surface so more energy is lost. This is vasodilation.

Question 45

What are NK cells?

Answer 45

Moderate exercise increases the number and activity of NK cells, which are found in the blood and lymph. Unlike B and T cells these provide non-specific immunity against cells invaded by viruses and cancers.

NK cells target cells that don’t display self markers. They release the protein perfornin, which makes pores in the cell membrane to allow proteases to enter and cause apoptosis.

Question 46

How do you treat damaged joints?

Answer 46

RICE

Rest, ice compression and elevation.

Anti inflammatiory painkillers and surgical repair

Question 47

Describe keyhole surgery and the cruciate ligaments in the knee

Answer 47

Keyhole surgery on jounts is known as arthroscopy. Keyhole surgery is effective on damaged cruciate ligaments in the knee.

Remember that ligaments attach bone to bone and control joint movement, preventing overstretching. 2 of the 4 knee ligaments (cruciate ligaments) are found deep inside the joint attached to the end of the femur.

The posterior cruciate ligament ptevents the knee from being bent too far back. The anterior cruciate ligament prevents the knee being bent too far forwards.

Question 48

How do knee replacements work?

Answer 48

A small incision is made, the patella is moved out of the way. The ends of the femur and tibia are trimmed to fit the prosthesis. The underneath of the patella is also trimmed so that an artificial piece fits.

Metals like titanium is used on the end of the femur; metal, ceramic or polyethylene is attached to the tibia and patella. These materials attach the new pieces

Question 49

State the advantages of physical activity

Answer 49

Increasing arterial vasodilation lowers BP

It increases HDL blood levels

Increased sensitivity of muscle cells to insulin improves blood glucose regulation and reduces chance of type II diabetes

Physical activity increases bone density and delays onset of osteoporosis

Question 50

What is type II diabetes?

Answer 50

High blood glucose levels reduce sensitivity of cells to insulin. The body does not produce enough insulin and somatic cells dont respond to insulin that is produced, so blood sugar levels can’t be controlled.

Hay menos absorption of glucose from the blood; cells break down fatty acids and protiens instead, leading to weight loss

Question 51

How are most hormones produced?

Answer 51

Cells in the endocrine gland that make hormones must not be affected by their products.

Therefore, most hormones are produced either in an inactive form or packaged dentro secretory vesicles by the G.app, which are released by exocytosis.

Question 52

Draw a table w the gland, the hormones they produce and the function of each hormone

Answer 52

insert

Question 53

Describe peptide hormones

Answer 53

10 to 300 a.a in length. Peptide hormones cant pass thru the cell membrane bc they’re charged.

Instead they bind to a receptor on the cell membrane; this then activates a second messenger molecule. This second messenger activates enzymes or transcription factors.

Question 54

What are steroid hormones?

Answer 54

Steroid hormones are formed from lipids and have complex ring structures.

They pass thru the cell membrane and bind directly to a receptor molecule dentro the cytoplasm.

Once activated, the hormone receptor complex acts as a transcription factor, switching enzyme synthesis on or off

Question 55

How do transcription factors work?

Answer 55

RNA polymerase and other protein transcription factors bind to the promoter region on DNA to form a transcription initiation complex.

Most TFctrs are created in an inactive form and then are converted to the active form by hormones, growth factors or other regulatory molecules. The transcription initiation complex can thus form and attach to the promoter region.

Genes remain switched off by failure of the transcription initiation complex to form and attach to the promoter region. This is due to the absence of protein transcription factors or the action of repressor molecules.

Question 56

describe and explain erythropoietin

Answer 56

insert image