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bio aqa a-level > Topic 3 > Flashcards

Topic 3 Flashcards

1
Q

Where are Bile salts produced and what do they do?

A

-Produced in liver
-they emulsify lipids to form small droplets
-the droplets increase surface area for lipase

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2
Q

Describe the role of lipase in the digestion of lipids

A
  • Pancreatic lipase hydrolyses lipids in the duodenum
  • In the ileum, membrane bound lipase continues hydrolysing lipids
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3
Q

Describe and explain the digestion of lipids

A
  • Bile salts are produced in liver and emulsify lipids to form small droplets
  • these increase the surface area for lipase
  • pancreatic lipase hydrolyses lipids in the duodenum
  • in the ileum, membrane bound lipase continues hydrolysing lipids
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4
Q

Describe and explain the structural adaptations of the Ileum

A
  • wall of ileum is folded and villi on its surface - increases surface area
  • villi contain many branching blood vessels (capillaries) and a long lymph vessel ( lacteals)
  • villi are lined with a single layer of epithelial cells, so short diffusion pathway
  • continual blood follow maintains concentration gradient
  • microvilli increases surface area so more transport proteins are present
  • more mitochondria, more respiration, so more ATP for active transport
  • many lacteals for fat absorption
  • contains more muscle to move, helps maintain concentration gradient
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5
Q

Describe where bile is produced, stored and released

A
  • produced in liver
  • stored in gall bladder
  • released in the duodenum
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6
Q

What is bile?

A

An alkaline fluid containing sodium hydrogencarbonate and bile salts

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7
Q

Describe carbohydrate digestion

A
  • saliva contains amylase which hydrolyses starch to maltose
  • only a small amount is broken down as it remains in the mouth for a short time
  • amylase is denatured in acidic stomach conditions
  • pancreatic amylase is released from the pancreas into the duodenum where starch digestion continues
  • bile is released into the duodenum
  • enters via bile duct - neutralises acidic chyme and provides optimum pH, alkaline salts also produced by intestine walls
  • epithelial lining in ileum produces membrane bound Maltase which hydrolyses maltose to glucose
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8
Q

Describe and explain protein digestion

A
  • endopeptidases (e.g. pepsin) hydrolyses internal peptide bonds in the stomach
  • enzymes in the stomach are created by stomach lining
  • in the duodenum another endopeptidase (trypsin) hydrolyses protein
  • this provides are larger surface area for exopeptidase activity
  • exopeptidase form amino acids
  • in the ileum, membrane bound dipeptidase hydrolyses dipeptides
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9
Q

Describe and explain the absorption of glucose

A
  • sodium ions actively transported out of the cell base into the blood
  • via sodium/potassium ions via active transport
  • this lowers the sodium ion concentration in cell so maintains gradient between lumen and epithelial celll
  • glucose and social ions from the lumen bind to co-transport protein in the membrane of the epithelial cell
  • move into epithelial cell down a concentration gradient
  • glucose is in high concentration inside the cell so it moves into the blood via facilitated diffusion using a channel protein
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10
Q

Describe and explain the absorption of amino acids

A
  • sodium ions actively transported out of the cell base into the blood via Na+/K+ pump via active transport
  • lowers the sodium ion concentration in the cell so it maintains a gradient between lumen and epithelial cell
  • amino acid and sodium ion from the lumen bind to co-transport protein in the membrane of the epithelial cell
  • move into the epithelial cell down a concentration gradient
  • amino acids are in high concentration on inside of the cell so they move into the blood via facilitated diffusion using a channel protein
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11
Q

Describe and explain the absorption of monoglycerides and fatty acids

A
  • micelles containing glycerol and fatty acids break up releasing them
  • they move into the epithelial cell by simple diffusion
  • glycerol and fatty acids are joined to make fats in the smooth endoplasmic reticulum (SER)
  • continues through the Golgi body to form chylomicrons - particles adapted for the transport of lipids
  • diffuse out of the epithelial cells by exocytosis and enter lacteals
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12
Q

Describe inspiration

A
  • diaphragm contracts and flattens
  • external intercostal muscles contract to pull ribs up and out
  • increases volume of the thorax and lungs - elastic walled alveoli stretches
  • pressure in alveoli decreases below atmospheric and air flows in down pressure gradient
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13
Q

Describe expiration

A
  • diaphragm relaxes and domes up
  • external intercostal muscles relax and internal intercostal muscles contract to pull ribs in and down
  • decreases volume of thorax and lungs - elastic walled alveoli shrinks by elastic recoil
  • pressure in alveoli increased and air flows out down gradient
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14
Q

Describe and explain the adaptations of the alveoli

A
  • many and small rounded alveoli, increases surface area
  • many branching capillaries, increases surface area
  • single layer of flattened epithelial cells, so short diffusion pathway
  • ventilation and circulation of blood ensures a gradient of O2 and CO2
  • RBC’s have a larger diameter than capillary so they squeeze through - slow blood flow=more time for exchange
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15
Q

What do fill filaments have?

A

Each fill filament has many lamellae which are covered in capillaries and made of a single layer of epithelial cells

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16
Q

Describe and explain gas exchange in fish

A
  • the fish breathes in water through the mouth, it flows over the gills
  • deoxygenated blood flows across each gill filament and then across the lamellae through capillaries
  • O2 diffuses from water into blood at the lamellae
  • blood and water flow in opposite directions - the counter current mechanism. It ensures blood continually meets with a higher oxygen concentration so diffusion can occur across the whole length of the lamellae
  • oxygenated blood flows along hill filaments to body cells
  • CO2 diffused from blood to water
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17
Q

How do insects prevent water loss?

A
  • waterproof exoskeleton
  • hairs around spiracles go reduce evaporation
  • close spiracles if they lose too much
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18
Q

Describe gas exchange in insects (overall view)

A
  • when spiracles are open, air diffuses into trachea
  • trachea branched into smaller tracheoles which are directly connected to cells (no blood system)
  • gas exchange occurs where air tubes meet cells
  • oxygen diffuses down a concentration gradient to respiring cells and CO2 diffuses out
  • insects use rhythmic abdominal movements to move air in and out of spiracles
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19
Q

Describe gas exchange in insects (at rest)

A
  • water fills ends of tracheoles
  • oxygen travels slower in water so decreases surface area over which oxygen can diffuse into muscle cells as there’s less contact with muscle cells
  • less oxygen diffuses in
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20
Q

Describe gas exchange in insects (during flight)

A
  • respiration is high - cells release substances such as lactate which are soluble and lower the water potential in the muscle
  • water moves from the tracheoles to the muscles cells by osmosis
  • increases surface area over which diffusion of oxygen can take place
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21
Q

How do the stomata open and close?

A
  • water enters the guard cells to make them turgid which opens the stomata
  • if the plant starts getting dehydrated, the guard cells lose water, become flaccid, stomata closes
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22
Q

What increases and decreases gas exchange in plants?

A
  • waxy waterproof cuticle allows very little gas exchange
  • numerous stomata with small diameter increases rate of diffusion
  • leaves are thin providing a short diffusion pathway
  • respiration and photosynthesis maintain concentration gradients for CO2 and O2
  • numerous Mesopotamia cells provide an increased surface area
  • mesophyll cells have air spaces around them so gases can diffuse faster - diffuse across cell wall and cell membrane of mesophyll cells
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23
Q

Describe gas exchange in plants in day, and night

A

Day:
- CO2 diffuses into cells for photosynthesis
- respiration also occurs
- rate of photosynthesis is greater than rate of respiration

Night:
- no photosynthesis as no light available
- oxygen diffuses in for respiration and CO2 diffuses out as a waste product

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24
Q

Why do the arteries have high pressure blood flowing through them?

A

High pressure due to left-ventricle contraction, and small lumen

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25
Q

What prevents the arteries bursting under high pressure?

A

Thick elastic tissue expands and lowers blood pressure

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26
Q

How is blood pressure maintained in the arteries?

A
  • pressure is maintained by the elastic tissue recoiling
  • expanding and recoil action smooths pressure surfers from the besting heart
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27
Q

Why do veins have low blood pressure?

A
  • low pressure due to loss of pressure at capillaries, and large lumen
  • have thinner layer of elastic tissue as blood pressure is low so much expansion isn’t needed
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28
Q

How do veins prevent back flow?

A
  • contain semi lunar valves
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29
Q

How is blood returned to the heart in the veins?

A
  • veins have low BP so blood is returned with muscle contraction (venous return)
  • when the skeletal muscles relax, BP decreases, blood flows down forcing semi lunar valves shut-down prevents back flow
  • when a person is standing, the skeletal muscles contract and squeeze the vein, BP increases which causes blood to flow upwards and semi lunar valves to open
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30
Q

Describe the pores in capillaries

A
  • pores allow gas exchange
  • materials leaking in and out causes a drop in pressure
31
Q

Describe and explain the structural adaptations of capillaries

A
  • numerous and highly branched so large surface area
  • single layer of cells so short diffusion pathway
  • pores allow gas exchange
  • small lumen so RBCs squeeze through in single file, rate of blood flow decreases so time for exchange increases
  • increases cross sectional area - increased frictional resistance
32
Q

Describe vasoconstriction in arterioles

A
  • smooth muscle contracts
  • lumen size decreases
  • less blood flows through capillaries
33
Q

Describe vasodilation in arterioles

A
  • smooth muscle tissue relaxes
  • lumen size increases
  • more blood flows through capillaries
  • when exercising, arterioles near muscles vasodilate, so more blood flows so muscles can respire more
  • arterioles near skin’s surface also dilate so heat is lost through radiation
34
Q

Describe arterioles

A
  • have large amounts of smooth muscle
  • control blood flow to capillaries
35
Q

Where is the xylem found?

A

Found in:
- roots
- stems
- leaves

36
Q

What is the xylem?

A

Long, hollow tubes which transport water over long distances

37
Q

Describe and explain features of the xylem

A
  • made of dead tissue, so doesn’t require energy and won’t be affected by temperature and respiratory inhibitors
  • hollow, so minimal resistance to flow of water and ions
  • strengthened by lignin
  • no end walls, no interruptions to the flow of water and ions
  • bordered pits (holes), allows water and ions to move laterally to adjacent vessels. Advantage if xylem is damaged, water and ions can still move through plant
38
Q

What is lymph fluid?

A

Fluid in lymphatic vessels

39
Q

What is tissue fluid?

A

Fluid surrounding cells

40
Q

What is plasma?

A

Fluid in blood vessels

41
Q

Name three types of cardiovascular disease we need to know

A
  • atheroma
  • thrombosis
  • aneurysm
42
Q

Describe the formation of an atheroma

A
  • high saturated fat/cholesterol diet
  • builds up within artery wall and forms a hardened plaque
  • narrows lumen and increased blood pressure
43
Q

Describe the formation of thrombosis

A
  • (formation of a blood clot)
  • ruptured atheroma damages artery wall and leaves a rough surface so platelets accumulate
  • high cholesterol diet / smoking - nicotine makes RBCs sticky
44
Q

Describe how aneurysms form

A
  • atheroma may weaken artery wall and cause swelling
  • it’s a ballon like swelling of arteries which can rupture and lead to haemorrhage
45
Q

How does CHD form?

A

Coronary heart disease occurs when coronary arteries have lots of atheromas

46
Q

How does a myocardial infarction take place?

A

Blockage in coronary arteries can lead to reduced blood flow to the heart muscle

47
Q

Describe the speed of blood flow

A
  • number of arteries is lower than the number of capillaries
  • arteries have a lower total cross sectional area
  • causes frictional resistance to be lower
  • increases speed of blood flow in arteries so blood pressure increases
48
Q

Where does excess tissue fluid go?

A
  • excess tissue fluid is absorbed into the lymphatic vessels
  • lymphatic vessels eventually drain back into the subclavian veins in the neck and go back into the blood stream - semi lunar valves prevent back flow
49
Q

Describe the tissue fluid process

A
  • increased hydrostatic pressure at arterioles end due to concentration of left ventricle
  • forces plasma out of capillaries forming tissue fluid which bathes the tissues
  • capillaries contain plasma proteins which are soluble and lower the water potential - tissue fluid has high water potential so water tries to move in by osmosis
  • hydrostatic pressure is higher than osmotic pressure so plasma is still forced out
  • as fluid leaves, hydrostatic pressure is lowered - lowered in venule end
  • also an increasing concentration of plasma proteins so water potential is even lower
  • osmotic pressure is now greater so water (filtered tissue fluid) moved back into capillary by osmosis
50
Q

What is translocation?

A

Translocation is the transport of organic substances - mainly sucrose in the phloem

51
Q

What type of cells is the phloem made from?

A

Many living cells called sieve tubes / sieve elements

52
Q

Describe features of phloem

A
  • sieve elements don’t have a nucleus and have few organelles so sugars are able to flow more easily
  • there’s are sieve plate between each sieve tube
  • each sieve tube had a companion cell beside it - carries out living functions for the sieve elements
53
Q

Where is the sucrose in the phloem transported?

A

Transported up and down the stem to where they’re needed: respiring cells which don’t carry out photosynthesis, growing areas, storage areas (roots, fruits).

54
Q

Describe transport of substances in the phloem

A
  • the leaf (source) carries out photosynthesis and produces glucose
  • glucose is converted to sucrose
  • companion cells actively transport sucrose in the phloem against a concentration gradient
  • this lowers the water potential in the phloem so water from the xylem moves into the phloem by osmosis
  • this created a high hydrostatic pressure/turgor pressure inside the sieve tubes at the source end of the phloem
  • at the sink end of the phloem, sugars move in to be used in respiration/ stored as starch
  • this increased the water potential inside the phloem so water moves in by osmosis
  • this creates lowered hydrostatic pressure at the sink end, a pressure gradient is formed - mass flow
55
Q

Describe the physical models of mass flow

A
  • source - not a good model as bag can’t photosynthesise so sugar was put in
  • sink - not a good model because won’t be able to store and use the sugar
  • phloem - no sieve tubes, no companion cells
  • xylem- good representation as xylem isn’t live
56
Q

State four pieces of evidence for translocation

A
  • ringing experiments
  • radioactive tracers
  • aphid mouth parts
  • respiratory inhibitor
57
Q

Describe ringing experiments (evidence for translocation)

A
  • a complete ring of phloem is removed so sucrose moving down can’t pass through
  • the sugar accumulates above the ring, shows there can’t be a downwards movement of sugars
58
Q

Describe how radioactive tracers are evidence for translocation

A
  • two plants of the same species at similar stages of growth are taken
  • the stem of one plant is grilled
  • a leaf below the griddle and at a similar position on the other plant is supplied with radioactive ^14CO2 or injected either radioactive ^14C6H12O6 (glucose with a carbon 14)
59
Q

Describe how aphid mouth parts show evidence for translocation

A
  • aphid pierce the phloem and their bodies are removed allowing sap to flow out
  • can be used to investigate pressure
  • sap flows out quicker nearer the leaves than further down, shows there’s a pressure gradient in mass flow
60
Q

Describe how a respiratory inhibitor can be evidence for translocation

A
  • stops respiration therefore ATP production and then mass flow, shows it requires ATP
61
Q

Describe the evidence against mass flow

A
  • sugar travels to many different sinks and not just one with the highest water potential
  • sieve plates would create a barrier to mass flow - a lot of pressure would be needed for solutes to get through
62
Q

Describe haemoglobin

A
  • made of four polypeptide chains which form a quaternary structure
    Each chain is linked to a harm group containing Fe2+, each can bind one oxygen molecule
63
Q

State three situations in which haemoglobin adapts

A
  • size of an organism
  • low O2 environments (e.g. underground environments/high altitudes)
  • fetal haemoglobin
64
Q

How does haemoglobin adapt to the size of an organism?

A
  • smaller animals have a larger SA:vol so lose heat quickly
  • have high metabolic rate to generate heat so have a high oxygen demand
  • haemoglobin will have lower affinity for oxygen so can be dissociated quickly
65
Q

How does haemoglobin adapt to low O2 environments, such as underground or high altitudes?

A
  • can have haemoglobin that had greater affinity for oxygen so more binds and is delivered to cells
  • if affinity is lower it would make dissociation easier so more respiration can occur
  • if person goes up mountain slowly, body adjusts= altitude acclimatisation
  • more haemoglobin caused the carrying capacity to increase, but blood becomes thicker and requires more pressure to pump
66
Q

How is foetal haemoglobin adapted?

A
  • foetus gets 02 by diffusion from mother’s placenta
  • foetal haemoglobin has higher affinity for O2 than maternal
    Foetal haemoglobin associates at low pO2
67
Q

What does increased respiration lead to in terms of oxygen dissociation?

A

Increased respiration leads to a greater partial pressure of CO2, so a lower pH, greater haemoglobin shape change, more dissociation, more oxygen for respiration, more respiration also causes a temperature increase as respiration produced heat

68
Q

What does the CO2 dissolving in plasma do?

A

Produces carbonic acid so lowers pH

69
Q

Describe and explain oxygen dissociation in lungs

A
  • increased partial pressure of oxygen
  • higher oxygen affinity
  • more association
70
Q

Describe and explain oxygen dissociation in respiring tissue

A
  • decreased partial pressure of oxygen and increased partial pressure of carbon dioxide
  • lower oxygen affinity
  • more dissociation
71
Q

What does the binding of an oxygen molecule do to haemoglobin

A
  • binding of one oxygen molecule changed the quaternary structure and makes it easier for others to bind = positive cooperativity
72
Q

Describe and explain changes in the shape of an oxygen dissociation curve

A
  • CO2 causes haemoglobin’s affinity for oxygen to decrease
  • shifts the curve to the right - Bohr effect
  • the greater the pO2, the greater the reduction in affinity and more that dissociates

More to left:
- higher affinity
- associates readily

More to right:
- greater reduction in affinity
- dissociates readily

73
Q

What does a low partial pressure of oxygen mean for oxygen binding rates?

A
  • at low pO2 levels, little O2 binds
  • high pO2 = high oxygen affinity
  • low pO2 = low oxygen affinity
74
Q

Explain how water from tissue fluid is returned to the circulatory system (4 marks)

A
  1. (Plasma) proteins remain;
    Accept albumin/globulins/fibrinogen for (plasma) protein
    2.(Creates) water potential gradient
    OR
    Reduces water potential (of blood);
    3.Water moves (to blood) by osmosis;
    4.Returns (to blood) by lymphatic syste

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