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Biology Model Answers > Topic 7 > Flashcards

Topic 7 Flashcards

1
Q

Describe how the concentration of calcium ions around the myofibrils is controlled

A

-calcium ions released from the sarcoplasmic reticulum
- in response to {nerve impulses/ action potential/ depolarisation { at the neuromuscular junction
- calcium channels open to allow calcium ions to cross the membrane
- calcium ions taken back up into the sarcoplasmic reticulum by active transport

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2
Q

Calcium ions are required for muscle contraction. Describe the role of calcium ions in the contraction of muscle fibres

A

calcium ions { bind } to the troponin
- tropomyosin is { displaced / shape altered }
- exposing myosin binding sites on actin

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3
Q

The thick filament in a myofibril contains myosin. The myosin head contains the enzyme ATPase. Explain the importance of the primary structure for the functioning of this enzyme

A

-primary structure determines interaction between amino acids and r groups
-determines folding of tertiary structure
-therefore affects shape of active site
- active site is complements to atp

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4
Q

Explain how the extensor and flexor muscles bring about movement of the lower leg.

A
  • tendons attach muscles to bones
  • flexor and extensor muscles act as an antagonistic pair
  • when the { extensor muscle contracts it pulls on the tibia to extend the leg/ flexor muscle contracts, it pulls on the fibula flexing the leg
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5
Q

Describe two structural differences between fast twitch muscle fibres and slow twitch muscle fibres

A

fast twitch fibres have { no/few } mitochondria, slow twitch fibres have many mitochondria
- fast twitch fibres have { no/few } capillaries present, slow twitch fibres have many capillaries present

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6
Q

Explain how the structure of a muscle fibre is related to its specialised function.

A

-cell surface membrane contains voltage gated channel to allow depolarising of muscle fibres
- many mitochondria for aerobic respiration to supply ATP
-presence of myosin and actin
-allow contraction of muscles

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7
Q

Explain the effect of increasing calcium ion concentration on the mean force produced by muscle fibres

A

-As calcium ion concrentraion increase force produced increase
-because more actin and myosin interact
-myosin bindin sites are exposed

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8
Q

Explain why it is necessary for the cardiac output of marathon runners to increase during a race

A
  • increase supply of oxygenated blood to muscles
  • to allow aerobic respiration
  • to provide more energy to meet the increased energy demands
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9
Q

Deduce how adrenaline can cause a change in heart rate

A

-Adrealine carried in the blood
-acts on SAN node
-increases the frequency of impulses produced by SAN
- increases the rate at which heart contracts

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10
Q

Deduce the effect of beta-blockers on the supply of blood to muscle during exercise

A

-larger the dose the greater the decrease in heart
-reducing the heart rate reducing the cardiac output
-therefore reducing the supply of blood to muscle

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11
Q

Explain how starting to exercise causes an increase in breathing rate

A

exercise initiates impulses from the { motor cortex/stretch receptors in muscle }
- impulses sent to or from the { ventilation centre/respiratory control centre/medulla oblongata }
- leading to increased impulses to the { intercostal muscles/diaphragm

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12
Q

The demand for oxygen changes during exercise.
The change in demand affects the breathing rate.
Explain the effect of exercise on the changes in oxygen consumption

A

exercise will increase oxygen consumption
- because there is increased aerobic respiration
- because more { energy/ATP } needed by the muscles
- oxygen is required to convert { lactic acid } into { glucose/pyruvate}
- oxygen consumption begins to decrease after exercise

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13
Q

Describe how a spirometer trace can be used to calculate the respiratory minute ventilation

A

-find the difference in peak trough volume to give tidal volume
- find ventilation rate
-multiply tidal volume by ventilation rate

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14
Q

Describe how a spirometer trace can be used to calculate oxygen consumption per minute

A

-difference in volume of one peak compared to subsequent one
-description of time calculation to produce a value per min

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15
Q

Describe how thermoregulatory mechanisms are controlled to help marathon runners avoid heat stress

A

-thermoreceptors in hypothalamus/skin detect increase in temp
-theremoregulatory centre in hypthluamus stimulated
-sends impulse to sweat glands
-increase blood flow to surface of skin by vasodilation

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16
Q

Explain the role of the brain in reducing the heart rate after exercise

A

-chemoreceptors detect a change in ph
- cardiovascular control centre receives impulse from chemorecptors therefore impulses are transmitter along the pns
-to SAN reducing heart rate

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17
Q

Describe how the brain reduces the activity of the sweat glands after the exercise.

A

-theremocreptors detect a decrease in temperature
-hypothalamus send fewer impulses to swear glands

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18
Q

Explain why too much exercise could be harmful to the human body

A

-increased excerise results in wear and tear of join/tendons/ligaments
-therefore leading to joint damage
-suppression off immune system lead to risk of infection

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19
Q

Name two molecules needed for aerobic respiration that can move into the mitochondria

A

Pyruvate
Oxygen
Reduced NAD/ADP

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20
Q

The outer mitochondrial membrane is not permeable to hydrogen ions (H+ ).
Explain the importance of this feature of the membrane

A

-to stop h+ diffusing out mitochondria into cytoplasm
-therefore maintaining a high concatenation oh H+ in the inter membrane space
-so H ions can move down concentration gradient
- by chemiomosis to sythisies atp

21
Q

Explain why some ATP is broken down during glycolysis

A

-the breakdown of atp donates phosphates to glucose
-ATP supplies energy to breaks down the glucose
-produces phosphorlayted 3 carbon compounds

22
Q

Explain the role of the carrier molecules in the electron transport chain

A
  • receive hydrogen from reduced NAD to allow reduced FAD to be oxidised
  • break hydrogen into protons/ hydrogen/ electron
    -electrons transfers by a series of redox reaction
    -energy relased is used to pump h ions into inter membrane space
23
Q

Explain the need for reduced NAD to be oxidised in a mitochondrion

A

-so that H can be delivered to the electron transport chain
-to allow ATP sythsies
- to regenerate NAD

24
Q

Explain how a single gene can give rise to protein molecules with different primary structures

A

-pre mRNA splicing removed exons
-produces different amino acid seqaunces

25
Q

Explain genes can be expressed in some tissues but not others

A

-Hormones bind to receptors found only in some cells
-regulating a transcription factor
-transcription factor binds to promoter region of acetylcholine gene
-therefore switching on/off transcription

26
Q

Transcription factors are involved in the activation of the insulin gene. Explain how transcription factors could activate insulin gene expression in beta cells

A

-interaction between transcription factors and promoter
- rna polymerase binds to promoter region
-transcriptio/mRNA pro dude for insulin gene

27
Q

Extracellular enzymes are produced by specialised cells. Explain how groups of cells can produce the same enzyme

A

-genes can be activated or deactivated
-these cells receive the same stimulus
- all of these cells have the gene for the enzyme switched on
- resulting in the production of mRNA for the enzyme

28
Q

Explain why stem cells from the heart cannot be used to grow cells to repair the cornea

A

-cell are not totipotent
-therefore some genes have already been activated and deactived
-therefore will not be able to speaclise into Cornea

29
Q

Equation for aerobic respiration

A

glucose + oxygen → carbon dioxide + water + energy

30
Q

What are the 4 stages of respiration

A

Glycolysis - cytoplasm
The Link reaction - mitochondria
The Krebs cycle - mitochondria
Oxidative phosphorylation - mitochondria

31
Q

What are the products of glycolysis

A

2 Pyruvate (3C) molecules which moves into the matrix of mitochondria to be used during the link reaction
Net gain 2 ATP
2 reduced NAD, which will be used during a later stage called oxidative phosphorylation

32
Q

Brief summary of glycolysis

A

Phosphorylation and splitting of glucose

33
Q

Brief summary of link reaction

A

Decarboxylation and dehydrogenation of pryuvate

34
Q

Brief summary of krebs

A

Cyclical pathway with enzyme controlled reaction

35
Q

Brief summary of oxidative
phosphorylation

A

Production of ARP through oxidation of hydrogen atoms

36
Q

Describe cardiac conduction

A

-SAN in top wall of right atrium conducts nerve impulse
- goes to AVN which delays impulse by a little
- then impulse goes to bundle of hiss which is where the impulse is split
- punkiji fibres at the bottom of the heart spread the impulse across the wall of the heart so it can contract

37
Q

How does a reflex arc work

A

-receptor detects a stimulus and a nerve impulse is activated
-sensory neurone carries nerve impulse to CNS along a pathway
-sensory neurone enters spinal cord
-sensory neurone forms a synapse with relay nerune
-relay neuron forms synapse with mother
-motor carried impulse to an electron which produces a response

38
Q

How are mitochondria adapted to their function

A

-Mitochondria have a double membrane structure, with an inner layer with many folds to create a high surface area.
-This provides more space for more metabolising proteins and therefore they are able to create more energy at one time.
-Synthesis of ATP in the mitochondria occurs during the last stage of respiration called oxidative phosphorylation.
-This relies on membrane proteins that make up the ‘electron transport chain’ and the ATP synthase enzyme – the details of this are covered later in the notes.
-Inner folded membrane (cristae) holds enzymes for respiration.

39
Q

Describe the structure of a muscle

A

Muscle is made up of muscle fibres.
Muscle fibres are surrounded by a plasma membrane called the sarcolemma (sarco means to do with muscle)
The plasma membrane has deep infoldings called T tubules.
T tubules run close to the ER called the sarcoplasmic reticulum
The cytoplasm (sarcoplasm) contains many mitochondria – why? To carry out aerobic respiration, generating ATP
Muscle is striped because of the arrangement of myofibrils.
Myofibrils are made up of filaments called thick and thin which are made up of myosin and actin.

40
Q

How is heart rate controlled by ns

A

2 nerves go from the cardiovascular control centre to the heart :Sympathetic nerve (accelerator) or Vagus nerve (Parasympathetic) nerve (decelerator)
If the SAN is stimulated by the sympathetic nerve then heart rate increases
If stimulated by parasympathetic nerve it slows down

41
Q

How is the brain involved with control of heart rate

A

Medulla controls cardiovascular/ Heart
Changes in the rate and force of heart contraction alter the cardiac output
Cardiac output increase to meet demand for gas exchange and prepare for physical excretion
Neurons and endocrine controls are involved

42
Q

Heat loss centre in hypothalamus(Stimulates: sweat glands to secrete sweat)
Inhibits:

A

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)

43
Q

Heat gain centre in hypothalamus:
Stimulates

A

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

44
Q

Where is the ventilation centre

A

Medulla

45
Q

How is inhalation controlled

A

-Ventilation centre (VC) sends impulses to external intercostal muscles and diaphragms so they contract.
-Lungs inflate stimulating stretch receptors in bronchioles.
-These receptors send inhibitory impulses to VC and stops impulses to the muscles and so they relax - can exhale again

46
Q

Controlling breathing with increase of co2

A

-Increased CO2 leads to increased breathing rate and depth of breathing
-This maintains concentration gradient between alveoli and blood which leads to efficient removal of CO2 and uptake of O2
-The opposite occurs with low CO2
-Control of CO2 in blood is therefore an example of negative feedback

47
Q

How does negative feedback control hormone levels

A

-If testosterone concentration changes, this is detected by the hypothalamus.
-A decrease in testosterone causes gonadotropin-releasing hormone to be produced in the hypothalamus.
-This stimulates the pituitary gland to release hormones that stimulate the testes to synthesise testosterone.

48
Q

Compare fast and slow twitch fibres

A

Fast- High intensity, anaerobic (without oxygen) as it doesn’t have time to take in oxygen, little mitochondria as its not using oxygen, little myoglobin so light colour, fatigues fast (fast action/get tired fast), high glycogen content as it uses glucose instead of making it EG SPRINT
Slow - aerobic (with oxygen) , low intensity but long duration, lots of mitochondria as uses lots of oxygen, lots of myoglobin makes fibre red, low glycogen content )produces doesn’t use) EG MARATHON

Biology Model Answers (8 decks)

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