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Biology Edexcel A Alevel > Topic 7 > Flashcards

Topic 7 Flashcards

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1
Q

How many muscles are required to move a bone to and fro?

A

at least 2

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2
Q

antagonistic muscles

A

muscle pairs arranged to work against each other to move a joint

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3
Q

extensor muscle

A

a muscle that contracts to cause extension of a joint

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4
Q

flexor muscle

A

a muscle that contracts to reverse the movement

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5
Q

Name 3 examples of synovial joints?

A

hip, knee and ankle

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6
Q

How are synovial joints able to move freely?

A

Due to the bones being separated by cavities filled with synovial fluid.

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7
Q

What is the function of tendons?

A

joins muscle to bone

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8
Q

What are the 2 functions of cartilage?

A

absorbs synovial fluid, and acts as a shock absorber

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9
Q

What is the function of a pad of cartilage?

A

gives additional protection

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10
Q

What is the function of fibrous capsule?

A

encloses joints

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11
Q

What is the function of synovial fluid?

A

acts as a lubricant

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12
Q

What is the function of the synovial membrane?

A

secretes synovial fluid

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13
Q

What are the 2 functions of the ligament?

A

joins bone to bone, and strong and flexible

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14
Q

what joins bone to bone?

A

ligaments

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15
Q

what attaches muscle to bone?

A

tendons

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16
Q

What is unusual about muscle cells?

A

they are very long and are multinucleate

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17
Q

Why are muscle cells multinucleated?

A

1- As a single nucleus could not effectively control the metabolism of such a long cell 2- During prenatal development several cells fuse together forming an elongated muscle fibre

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18
Q

Where are tendons found?

A

They connect the muscle to bone

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19
Q

What are muscles made up of?

A

Bundles of muscle fibres bound together by connective tissue.

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20
Q

What makes up a single muscle fibre?

A

A single muscle cell surrounded by a cell surface membrane

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21
Q

What is the length and diameter of a muscle fibre?

A

Several cm long but less than 0.1mm in diameter

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22
Q

What is inside a muscle fibre?

A

Numerous myofibrils and cytoplasm containing mitochondria and other organelles

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23
Q

What makes up myofibrils?

A

Repeated contractile units called sarcomeres

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24
Q

What 2 types of protein molecule make up sarcomeres?

A

Thinner filaments made of protein actin Thicker filaments made of protein myosin

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25
Q

What do the colours on a sarcomere represent

A

Light- Actin Dark- Actin AND Myosin Intermediate- Myosin

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26
Q

Describe the process of sliding filament theory

A

1-Ca+ are released from sarcoplasmic reticulum

2-Ca+ attaches to troponin molecule

3-The tropomyosin molecule shifts as a result exposing myosin binding sites on the actin filaments

4-Myosin head bind with myosin binding sites on the actin filament forming cross bridges

5-When myosin head binds to the actin ADP and Pi on the myosin head are released

6-Myosin changes shape causing myosin head to nod forward and so results in relative movement of filaments.

7-ATP molecule binds to myosin head causing it to detach from the actin.

8-An ATPase on the myosin head hydrolyses the ATP forming ADP and Pi

9-The hydrolysis causes a change in the shape of the myosin head and it returns to its upright position.

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27
Q

What are the 4 stages of respiration?

A

Glycolysis, link reaction, Krebs cycle, electron transport chain

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28
Q

Explain the process of glycolysis

A

1- (6C) glucose is phosphorylated forming phosphorylated glucose using ATP (6C,2Pi)

2- Phosphorylated glucose splits into 2 triose phosphates.

3- Triose phosphate is oxidised (releases H atom) which then joins NAD to form reduced NAD.

4- 2 ATP molecules per triose phosphate is formed

5- 2 Pyruvates are formed

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29
Q

Explain the link reaction

A
  • Pyruvate (3C) is decarboxylated (-CO2) and dehydrogenated (-H).
  • The CO2 is released into the atmosphere and the 2H turn NAD into reduced NAD.
  • Acetyl (2C) CoA is formed.
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30
Q

Explain the Krebs cycle

A
  1. -Acetyl CoA (2C) join with a 4C compound forming a 6C compound.
  2. 6C compound releases a CO2 and 2H (2H forms reduced NAD) 5C compound is formed
  3. -5C compound loses:
    1. *CO2
    2. *ATP
    3. *2H– NAD > Reduced NAD
    4. *2H– NAD > Reduced NAD
    5. *2H– FAD > Reduced FAD
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31
Q

Explain the electron transport chain in respiration

A

1- Reduced coenzyme (eg NAD or FAD) carries 2H+ and electrons to electron transport chain on inner mitochondrial membrane.

2- Electrons pass from one electron carrier to the next in a series of oxidation and reduction reactions.

3- Protons (H+) move across inner mitochondrial membrane creating high H+ concentrations in the intermembrane space.

4- H+ diffuse back into the mitochondrial matrix down the electrochemical gradient.

5- H+ Diffusion allows ATP synthase to catalyse ATP synthesis.

6- Electrons and H+ ions recombine to form H atoms which then combine with oxygen to form water.

*if the supply of oxygen stops the electron transport chain and ATP synthesis will also stop.

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32
Q

What is the overall reaction of aerobic respiration?

A

The splitting of the respiratory substrate, to release carbon dioxide as a waste product and reuniting hydrogen with atmospheric oxygen with the release of large amounts of energy.

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33
Q

Where does glycolysis take place?

A

cytoplasm

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34
Q

Where does the link reaction happen?

A

mitochondrial matrix

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35
Q

Where does the Krebs cycle occur?

A

mitochondrial matrix

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36
Q

Where does chemiosmosis occur?

A

inner mitochondrial membrane

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37
Q

What factors might effect the rate of respiration?

A

enzyme concentration, substrate concentration, temperature and pH

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38
Q

How does ATP control respiration?

A

When ATP is present the enzyme responsible for glucose phosphorylation has a shape that makes it inactive so cannot catalyse the reaction. But when ATP is broken down the enzyme is converted back to its active form and can catalyse the phosphorylation of glucose.

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39
Q

How does anaerobic respiration work

A

The pyruvate produced at the end of glycolysis is reduced to lactate and the oxidised form of of NAD is regenerated. The person can continue as glucose is partially broken down to produce a small amount of ATP.

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40
Q

Why does aerobic respiration stop without oxygen?

A

As without oxygen to accept the hydrogen ions and electrons at the end of the end of the electron transport chain the process ceases. The reduced NADs created cannot therefore be oxidised.

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41
Q

What happens when lactate builds up?

A

It forms lactic acid meaning that the pH of the cell falls inhibiting the enzymes that catalyse the glycolysis reactions.

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42
Q

Why do enzymes stop working when lactate builds up?

A

Hydrogen ions from the lactic acid accumulate in the cytoplasm they neutralise the negatively charged groups in the active site of the enzyme. So the attraction between the charged groups will be affected and the substrate may no longer bind.

43
Q

How do animals get rid of lactate?

A

Lactate is converted back to pyruvate. It is oxidised directly to CO2 and water via the Krebs cycle, thus releasing energy to synthesise ATP. So oxygen uptake is greater than normal in the recovery period.

44
Q

What is oxygen debt or post exercise oxygen consumption?

A

the amount of oxygen needed to oxidise lactic acid to carbon dioxide and water

45
Q

How is the immediate regeneration of ATP achieved?

A

Creatine phosphate which is stored in the muscles and can be hydrolysed to release energy. Creatine phosphate + ADP –> creatine + ATP

46
Q

What are the 3 energy systems

A

ATP-PC, anaerobic, aerobic

47
Q

How is adequate oxygen supply maintained?

A

Increased cardiac output, faster rate of breathing and deeper breathing.

48
Q

how do you calculate cardiac output?

A

stroke volume x heart rate

49
Q

What is stroke volume?

A

the volume of blood pumped out of the left ventricle each time the ventricle contracts

50
Q

What form is stroke volume calculated?

A

cm3

51
Q

venous return

A

The amount of blood returned to the heart by the veins

52
Q

How does the amount of blood ejected change during exercise?

A

When the body is at rest normally 40% of the blood remains in the ventricles but during exercise stronger contractions occur ejecting more of the residual blood from the heart.

53
Q

What are cardiac muscles and what does it mean?

A

Myogenic: means they can contract without external nervous stimulation

54
Q

What initiates the heart to contract?

A

Small changes in the electrical impulses and polarity causes the cells to contract.

55
Q

Where does depolarisation start?

A

sinoatrial node

56
Q

Where is the sinoatrial node (SAN) located?

A

wall of right atrium

57
Q

What is the sinoatrial node (SAN) known as?

A

pacemaker

58
Q

What happens to the impulse generated from the SAN?

A
  1. The impulse spreads across the right and left atria causing them to contract at the same time.
  2. The impulse also spreads to the atrioventricular node
  3. From here the impulse is conducted to the ventricles after about 0.13 second delay.
59
Q

Why is it important that the impulse at the atrioventricular node is delayed?

A

The delay ensures that the atria have finished contracting and the ventricles have filled with blood before they contract.

60
Q

What happens after the signal delay at the atrioventricular node?

A

The signal delay reaches the Purkyne fibres which are specialised muscle fibres. They conduct impulses rapidly to the apex of the ventricles.

61
Q

What are the bundles of fibres around the ventricles called?

A

bundle of His

62
Q

Which are the first ventricular cells to be depolarised and why?

A

The ventricular cells at the apex of the heart so the contractions travel upwards.

63
Q

Explain the route taken by by electrical impulses?

A
  1. Electrical impulses from the SAN spread across the atria walls causing contractions.
  2. Impulses pass to the ventricles via the AVN
  3. Impulses pass down the Purkyne fibres to the heart apex.
  4. The impulses spread upwards through the ventricle walls causing contractions from the apex upwards. Blood is squeezed into the arteries.
64
Q

How do electrocardiograms (ECG) work?

A

Electrodes are attached to a persons chest and limbs to record the electrical current produced during the cardiac cycle.

65
Q

What part of the brain contains the cardiovascular control centre?

A

medulla oblongata

66
Q

What are the two types of nerves in the autonomic nervous system?

A

sympathetic and parasympathetic

67
Q

What are the two nerves connecting the cardiovascular control centre to the heart?

A

sympathetic nerve and vagus nerve.

68
Q

Stimulation the vagus nerve causes heat rate to?

A

slow down

69
Q

Stimulation the sympathetic nerve causes heat rate to?

A

increase

70
Q

What does the cardiovascular control centre detect?

A

Carbon dioxide and lactate accumulation in the blood, reduction of oxygen and increased temperature.

71
Q

What happens when a starting pistol goes off?

A

Skeletal muscles contract, and stretch receptors are stimulated. They send impulses to the cardio vascular control centre which raises the heart rate via the sympathetic nerve.

72
Q

What effect does adrenaline have on heart rate?

A

Similar to stimulation of sympathetic nerve. But directly effects the sinoatrial node increasing the heart rate to prepare the body for physical demands.

73
Q

How does ventilation detect and react to increased levels of CO2?

A

1- CO2 dissolves in the blood plasma making carbonic acid. 2- Carbonic acid dissociates into hydrogen ions and hydrogencarbonate ions thereby lowering the pH of the blood. 3- Chemoreceptors sensitive to hydrogen ions are located in the ventilation centre of the medulla oblongata. They detect the rise in hydrogen ion concentration. 4- Impulses are sent to other parts of the ventilation centre. 5- Impulses are sent from the ventilation centre to stimulate the muscles involved in breathing.

74
Q

ventilation

A

movement of air in and out of the lungs

75
Q

What are 6 features of slow twitch fibres?

A

-A lot of myoglobin (so red) -Many mitochondria -Little sarcoplasmic reticulum (Tubes of cytoplasm, where Ca+ is released from) -Low glycogen content (store of glucose) -Numerous capillaries -Fatigue resistant

76
Q

What are 6 features of fast twitch fibres?

A

NAME?

77
Q

Why might a person be better suited to sprinting than endurance?

A

As they might have a higher proportion of fast twitch fibres than slow twitch fibres.

78
Q

Homeostasis

A

The maintenance of a stable internal environment.

79
Q

What are the homeostatic control mechanisms trying to return to?

A

Norm value or set point

80
Q

Negative feedback

A

A change in a physiological variable that is being monitored triggers a response that counteracts the initial fluctuation.

81
Q

Positive feedback

A

Feedback that tends to magnify a process or increase its output.

82
Q

Principle of negative feedback

A

Maintaining systems within narrow limits

83
Q

What does the heat loss centre in the hypothalamus stimulate and inhibit?

A

Stimulates

  • Sweat glands to secrete sweat.

Inhibits

  • Contraction of arterioles in skin (dilates capillaries in skin)
  • Hair erector muscles (relax- hairs lie flat)
  • Liver (reduces metabolic rate)
  • Skeletal muscles (relax- no shivering)
84
Q

Explain the process of temperature control through negative feedback

A
  1. Set point
  2. Temperature rise/fall is detected by receptors
  3. Sends impulse to heat loss heat gain centre in hypothalamus
  4. Effector reacts
  5. Temperature falls/rises
  6. Set point
85
Q

What does the heat gain centre stimulate or inhibit?

A

Stimulates

  • Arterioles in the skin to constrict
  • Hair erector muscles to contract
  • Liver to raise metabolic rate
  • Skeletal muscles to contract in shivering

Inhibits

  • Sweat glands
86
Q

When we get too hot which centre is activated?

A

The heat loss centre in the hypothalamus

87
Q

What happens to the skin in order to preserve heat?

A

Vasoconstriction

  • The muscles in the arteriole walls contract causing arterioles to constrict.
  • Reducing the blood supply to the surface capillaries.
  • Blood is diverted through the shunt vessel which dilates as more blood flows through it.
  • Blood flows further from the skin so less energy is lost.
88
Q

What happens to the skin when it is warm?

A

Vasodilation

  • The shunt vessel constricts and muscles in the walls of the arterioles relax.
  • Blood flows through the arterioles making them dilate.
  • More blood flows closer to the surface.
  • More energy is lost.
89
Q

Why do we sweat when our body temp is too high?

A
  • Sweat released on the skin evaporates
  • Taking heat energy from the skin.
  • Sweat glands are stimulated by nerves from the hypothalamus.
90
Q

Why are hairs raised when it is cold?

A
  • As hair erector muscles contract
  • In the aim to trap a layer of air that insulates our body.
91
Q

What are the 4 methods of energy transfer?

A
  1. Radiation
  2. Conduction
  3. Convection
  4. Evaporation
92
Q

What are the possible disadvantages of exercising too much?

A

Wear and tear on joints, suppression of the immune system.

93
Q

What are the disadvantages of exercising too little?

A

Increased risk of obesity, cardiovascular disease (CVD) and diabetes

94
Q

Why does vigorous exercise supress the immune system?

A

The specific immune system is temporarily depressed.

95
Q

What ligaments can be very effectively tackled by a key hole surgery?

A

Cruciate ligaments

96
Q

How do surgeons carry out an arthroscopic procedure?

A

They make one or two small incisions, often only 4mm long. A small camera and light source are inserted, allowing the inside of the joint to be seen and a diagnosis can be made or confirmed. Then if surgery is required, miniature instruments are inserted through the incisions.

97
Q

Why are key hole surgeries helpful to those wanting to participate in sport?

A

As only a small incision is made the recovery is faster, and it is not uncommon for top athletes to return to normal athletic activities within a few weeks.

98
Q

How do peptide hormones affect cells?

A
  • Peptide hormones are protein chains which are not able to pass through cell membranes easily as they are charged.
  • So instead they bind to a receptor on the cell membrane.
  • This then activates another molecule within the membrane ‘the second messenger’ which brings about chemical changes in the cell.
99
Q

How do steroid cells affect cells?

A
  • The hormone is formed from lipids and have complex ring structures.
  • They pass through the cell membrane and bind directly to the receptor molecule within the cytoplasm.
  • Once activated the hormone-receptor complex which acts as a transcription factor.
  • A transcription factor turns enzyme synthesis on or off.
100
Q

How are genes switched on by transcription factors?

A
  • RNA polymerase is present and if all required transcription factors are present eg hormones.
  • RNA polymerase and the transcription factors are present and bind to the promoter region which is adjacent to the gene to be transcribed.
  • This forms the transcription initiation complex and transcription will proceed.
101
Q

How can genes be prevented from being transcribed

A
  1. Protein repressor molecules that bind to DNA of the promoter region
  2. Protein repressor molecules can bind to the transcription factors themselves
  3. The repressor molecules could be inactive forms of the transcription factors
102
Q

Argue why performance enhancing drugs should be able to be used

A
  • It is the athletes decision if they choose to take the drugs.
  • That the sport is already unfair due to the inequality of competition due to the differences in time available for training and in resources
103
Q

Argue why performance enhancing drugs should not be used

A
  • Performance enhancing drugs are bad for the athletes health and they might not make a properly informed decision to take the drugs.
  • They may be pressured by coaches, sponsors and general public.

Biology Edexcel A Alevel (15 decks)

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