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a level biology > UNIT 3 - Exchange and Transport Systems > Flashcards

UNIT 3 - Exchange and Transport Systems Flashcards

1
Q

what is the general trend between an organisms volume and surface area

A

as aorganisms increase in volume surface area decreases

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2
Q

explain how single celled organisms exhcnage substances

A

simple diffusion as the large SA:V ratio is large and therefore a short diffusion pathwat

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3
Q

explain why large organsism need adaptations for exhcnage of substances

A

the diffusion pathway is too large for efficient gas exchange to occur as there is a smaller SA:V ratio for absorbption of nutrients and exchnage of gases O2 and CO2

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4
Q

what is metabolic rate

A

the amount of energy expended by that organism within a given period

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5
Q

what is the basal metabolic rate

A

the metabolic rate of an organism when at rest

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6
Q

how can metabolic rate be measured

A

oxygen consumption
carbon dioxide production
heat production

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7
Q

what is ficks law

A

rate of diffusion= (surface area x concentration difference) / thickness of membrane

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8
Q

how are insects adapted for gas exchange

A

They have spiracles that lead into a large network of trachea and tracheoles which run to muscle fibres.

A concentration gradeint is created as oxygen is used by the tissue fibres allowing more to move in through the spiracles.

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9
Q

what do very active insects do to get the supply of oxygen they demand if they cant get it through spiracles

A

they close the spiracles and use muscles to create a pumping movement for ventilation

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10
Q

what does anaerobic repsiration cause to happen in an insects gas exchnage system

A

produces lactic acid which lowers the water potential of the muscle fibres causing water at the end of the tracheoles to move into the muscle cells by osmosis and therefore diffusion of oxygen is made easier by the diffusion pathway being made shorter and therefore aerobic respiration can start again

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11
Q

how are fish adapted for gas exchange

A

series of gills on each side of the head that have stacks of filaments and on the surface of the filaments are rows of lamellae, Blood flow and water flow are in oppsite direction in a countercurrent system maintaining gas exchnage as theres a constant gradient

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12
Q

how are plants adapted to gas exchange

A

the guard cells can go turgid and the stomata remains open allowing air to enter the leaf and rapidly diffuse across the air spaces in the spongy mesohpyll and once the CO2 reaches photosynthesising tissues it is immediately used up to maintain the concentration gradient

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13
Q

how do insect counterbalance water loss

A

posses a waterproof exoskeleton that prevents water loss as it has a waxy coating which makes gas exchange difficult and stop

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14
Q

how to plants counterbalance waterloss like cacti and maram grass

A

cacti: thick cuticle, shalloe deep roots, leaves have become spines that can no longer photosynthesise

maram grass: leaves can roll up reducing exposure to wind protecting the stomata, exposed surface has a thick cuticle and no stomata, the inner surface of the leaf possesses a large amount of hairs

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15
Q

how are alveoli adapted

A

short diffusion pathway: walls are one cell thick, flattened
maintaining concentration gradient: constant blood flow
large surface area: large number of them in the lungs

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16
Q

describe what happens in inspiration

A

external intercostal mucles contract, the diaphram contracts and goes flat the ribs go out and up leading to an increase in volume in the thorax which causes a lower pressure which causes a pressure gradient so air from outside rushes into the thorax

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17
Q

describe what happens in expiration

A

internal intercostal muscles contract pulling the ribs down and in and the diaphram relaxes and becomes domed shaped so the volume in the thorax decreases and so the pressure increases so air is forced out of the lungs

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18
Q

what is the equation for pulmonary ventilation rate

A

PVR= tidal volume x breathing rate

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19
Q

what is the need for a circulatory system

A

so that the large organisms can supply their cells with desired substances

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20
Q

what is the structure and bonds of haemoglobin

A

globular protein made up of four polypeptide chains held together by disulphide bonds arranged so that their hydrophillic R groups points outwards and be soluble in water

The haem group contains an iron (II) ions which can reversibly with oxygen forming oxyhaemoglobin

Each haemoglobin with four haem groups can therfore carry 4 O2 molecules

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21
Q

explain the oxygen dissociation curve

A

The far left of the graph is when the haem groups are all unbound and therefore the affininty is at its lowest

As the partial pressure increases and the saturation of haemoglobin increases the affininty increases as the strcuture of haemoglobin gets looser and the shape of it changes

As the haemoglobun gets more and more saturated there is a levelling off of the curve as it takes longer for the 4th oxygen to bind as there is a shortage of remaining binding sites

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22
Q

what is the Bohr shift and explain it

A

changes in teh dissociation curve as a reult of CO2 levels are known as the Bohr shift effect

when the partial pressyre of CO2 in the blood is gigh the haemoglobins affninity for oxygen is reduced due to the CO2 lowering the pH of the blood as the CO2 binds with the water to from carbonic acid

on the dissociation cirve the curve shifts to the right when CO2 levels increase

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23
Q

what is the equation for cardiac output

A

cardiac output= heart rate x stroke volume

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24
Q

how do animals adapt to high altitudes

A

the partial pressure in oxyven is lower at higher altitudes and therfore have haemoglobin that is adapted to these conditions

For example, llamas have haemoglobin that binds much more readily in oxygenn which is important as it allows them to obtain sufficient level of oxygen saturation in thier blood when the partial pressure of oxygen is low

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25
Q

how are foetus’s adapted to get sufficient oxygen into the body

A

they have higher affinity for oxygen than adults and this is vital as it allows foetus to obtain oxygen from its mothers blood at the placenta

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26
Q

what is the basic structure of the heart

A

the heart is divided into four chambers the top two being the atris and the bottom two being the ventricles

the left and rught sides are seperated by a wall called the septum

there are two blood vessels taking bloof to the heart and they are the vena cava and the pulmonary vein

there are two blood vessel taking blood away from the heart and these are called the aorta and the pulmonary artery

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27
Q

explain the layout of the valves in the heart

A

the right hand side of the hearts right atrium and ventricle are seperated by the tricuspid valve

the left hand sides atrium and ventricle are seperated by the bicuspid valve

the left ventricle and the aorta and seperated by the aortic valve

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28
Q

what are the roles of valves

A

valves are important from keeping the blood flowing in the right direction and not backwards

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29
Q

what are the roles of coronary arteries

A

the coronary arteries are responsible for giving the blood its own blood supply so that it can contract

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30
Q

explain the structure of the ventricles and how is helps with their function

A

the walls are thicker due to the fact ventricles have to contract and squeeze blood inwards to create enough pressure for the semi- lunar valves to open and blood to be forced through

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31
Q

explain the structure of the atria and how is helps with their function

A

The muscular walls of the atria and thinner than those of the ventricles since the atria don’t have to generate as much force when their walls contract but enough so that there is enough force that the blood is forced down into the ventricle and through the atrioventricular valves.

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32
Q

what is the definition of the cardiac cycle

A

The cardiac cycle is the series of events that take place in one heart beat including mucle contraction known as systole and relaxation known as diastole

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33
Q

what happens in atrial systole

A

The walls of the atria contract so volume decreases and pressure increase

The pressure increases above that in the ventricles forcing the atrioventricular ventricles to open

Blood is forced into the ventricles

34
Q

what happens in ventricle systole

A

The walls of the ventricle contract increasing pressure as volume decreases

The pressure in the ventricle rises above that in the atria so the AV valves close to stop backflow of blood

The pressure rises above that in the aorta/pulmonary artery forcing the semilunar valves open, so blood is forced into the arteries

35
Q

what is diastole and explain what is happening in the heart when it is occuring

A

The ventricle and atria are both relaxed

The pressure in the ventricles drops below that in the aorta/pulmonary artery forcing the SL valves to close

The atria continue to fill with blood as blood returns to the heart via the vena cava and pulmonary vein

Pressure in the atria rises above that in the ventricles as the AV valves open

Blood flows passively into the ventricles without the need of atrial systole

The cycle begins again with atrial systole

36
Q

what is an arteries strcuture and how is it related to its function

A

The wall of the artery is relatively thick with layers of collagen and smooth muscles and elastic fibres

The elastic fibres allow the artery to expand around blood surging through at high pressure when the heart contract these fibres recoil when the heart relaxes. This helped maintain a high blood pressure

37
Q

what is a veins structure and how is it related to its function

A

The wall of the vein is relatively thin with the thinner layers of collagen smooth muscle and elastic fibres

The lumen of the vein is which larger than the lumen of an artery

The veins have valves that prevent backflow of blood helping return blood to the heart

38
Q

what is an arterioles strcuture and how is it related to its function

A

Can contact and partially cut off blood flow to specific organs

Have a much lower proportion of elastic fibres and many muscle cells

The presence of muscle cells allows them to contract and close their lumen to stop blood flow

39
Q

how are capillaries adapted

A

Very small diameter which forced the blood to travel slowly which provides more opportunity for diffusion to occur

Capillaries branch between cells which helps substances diffuse between blood and cells quickly as there is a short diffusion pathway

The walls of the capillaries are made from a single layer of endothelial cells so that the diffusion pathway is reduced for oxygen and carbon dioxide between blood and tissues of the body. The cells of the wall have pores which allow blood plasma to leak out and from tissue fluids

40
Q

what is digestion

A

the process in which larger molecules are hydrolysed by enzymes into small molecules which can be absorbed and assimilated

41
Q

what is the physical breakdown part of digestion and what occurs

A

large food is broken down into smaller pieces making it easier to ingest the food

the larger surface area helps the next stage which is chemical digestion

example include:
churning of food by the stomach wall
chewing

42
Q

what does chemical digestion do and what carries it out

A

chemical digestion hydrolyses larger insoluble molecules into smaller soluble ones

it is carried out by large range of enzymes that are specific

43
Q

what are the three things hydrolysed by digestion and what enzymes do it and what are the products

A

carbohydrase hydrolyses carbohydrates into monosaccarides

lipases hydrolyse lipids into fatty acids and glycerol

proteases hydrolyse proteins into amino acids

44
Q

what is the mechanism of hydrolysing carbohydrates and what happens at each stage

A
  1. saliva enters the mouth and it contains amylase which contains salts that maintain pH for the amylase to work
  2. HCL in the stomach denatures the amylase so no further hydrolysis takes place
  3. pancreatic amylase continues to hydrolyse by hydrolysing alternate glycosidic bonds of starch to produce disaccharides of maltose and alkaline salts are produces to maintain the pH so it can function
  4. small intestine epithelial cells produce disaccharidase maltase that hydrolyse maltose
45
Q

what disaccharides are hydrolysed in digestion and by what enzyme

A

maltose is hydrolysed by maltase to produce glucose

sucrose is hydrolysed by sucrase to produce glucose and fructose

lactose is hydrolysed by lactase to produce glucose and galactose

46
Q

how are lipids digested
what reaction type is it
where is the enzyme stored
what are the products

A

lipids are hydrolysed by enzymes called lipase which are produced in the pancreas and hydrolyse ester bonds to form fatty acids and monoglycerides

47
Q

how are bile salts crucial in lipid digestion

A

lipids are split into micelles by bile salts produced by the liver and this is called emulsification and it increases the surface area increasing the rate of digestion

48
Q

what are proteins hydrolysed by and what are the three different types and where are they used in the protein chain and where are they produces

A

proteins are hydrolysed by peptidases

  1. in the stomach protease enzymes
    hydrolyses peptide bonds creating smaller sized proteins secreted alongside HCL
  2. pancreas neutralises acid mixture and contains endopeptidases and exopeptidases which further hydrolyse peptide bonds to produce dipeptides
  3. membrane bound dipeptidase is used to hydrolyse the bonds of dipeptides into amino acids in the epithelial cells of the ileum in the small intestine
  4. amino acids are released into the cytoplasm of the cell
49
Q

what is the structure of the ileum

A

the wall of the ileum is folded and has finger like projections called villi on the folds then microvilli are on the villi

50
Q

how is the villi adapted

A

thin walls lined with epithelial cells and a rich network of blood capillaries

51
Q

what is the mechanism for the absorption of fatty acids and glycerol

A
  1. monoglycerides and fatty acids remain in association with bile salts meaning there are still micelles
  2. these micelles come into contact with the epithelial cells lining the villi of the ileum and this causes the micelles to break down releasing monoglycerides and fatty acids again
  3. monoglycerides and fatty acids are non polar and therefore diffuse across the cell membrane into the epithelial cells and are then recombined at the RER to from triglycerides and are moved to the Golgi
  4. at the Golgi the triglycerides are associated with cholesterol and lipoproteins to form CHYLOMICRONS
  5. the chylomicrons move out of the epithelial cells by exocytosis and enter the lacteals found at the centra of the villi
  6. chylomicrons then pass via the lymphatic system into the blood system
52
Q

how do plants obtain water

A

plants absorb water from their roots and the root hair cells in th3 roots and water is transported up the stem away from the roots in the xylem vessel

53
Q

what is the structure of a xylem vessel

A

hollow thick walled tubes

54
Q

what is the movement of water up the stem called

A

transpiration

55
Q

what is transpiration and what is the mechanisms of it

A

Water evaporates at the stomata on the leaves lowering the pressure

water from the xylem moves up to take its place as there is a pulling action on the water column behind it due to the cohesion of water due to hydrogen bonds between them and the adhesion of water to the xylem

as the water is pulled up it makes the xylem tube narrower as it creates tension and this increases capillary action

56
Q

how does the cohesion tension theory

A

Water molecules form hydrogen bonds between one another causing cohesion as water forms a continuous unbroken column up the xylem

adhesion is when the water can stick to the walls of the xylem and this is due to the narrowness of the xylem

root pressure- as water moves into the root by osmosis it increases the pressure in the roots which gives a push action to the water above it

57
Q

what are the evidence examples for cohesion theory

A
  1. The diameter of a tree trunk changes due to the rate of transpiration
    —>During the day when transpiration is at its greatest there is more tension in the xylem, and this pulls the walls inwards and causes the tree to shrink in diameter
    —-> At night when transpiration is at its lowest there is less tension in the xylem and so the diameter of the trunk increases
  2. Broken xylem vessels have air enter
    —->If a xylem vessel is broken and air enters it the tree can no longer draw up water this is because the continuous column of water is broken and so the water molecules can no longer stick together
  3. Broken xylem vessels don’t have water leak out
    —->When a xylem vessel is broken water does not leak out as would happen if it were under pressure instead air is drawn in which is consistent with it being under tension
58
Q

what is translocation

A

The process by which organic molecules and some mineral ions are transported from one part of the plant to another

59
Q

what is the structure of phloem

A

Phloem is made of sieve tube elements, long thin structures arranged end to end, and their end walls are perforated to form sieve plates. The sieve plates are associated with companion cells to help keep the phloem cells alive.

60
Q

what is a source and a sink

A

A source is a site where a plant produces sugars during photosynthesis (e.g. leaf)

A sink is anywhere the products made by the source are being used and the products are transported to sinks to be used or stored by the plant ( e.g. growing cells)

61
Q

why is it important that the phloem are multidirectional

A

Sinks can be anywhere in a plant sometimes above and sometimes below the source and it follows the translocation of molecules in phloem can be either direction and this is why phloem are multidirectional otherwise the products couldn’t be transported to the sinks

62
Q

what substances are transported by the phloem

A

Sucrose

Amino acids

Inorganic ions: potassium ions, chloride ions, phosphate ions, magnesium ions

63
Q

how do micelles help with digestion

A
  1. make the fatty acids more soluble in water
  2. carry fatty acids to epithelium cells lining the ileum
  3. maintain a higher concentration of fatty acids compared to the epithelial cells lining the ileum as it groups a lot of the fatty acids together
64
Q

why can fatty acids enter the epithelial cells by simple diffusion

A

they are nonpolar

65
Q

what happens when the fatty acids and monoglycerides that have been digested enter the cell

A

assembled back into triglycerides inside of the golgi body or RER and sometimes added to a protein to form a chylomicron which exits the cell by exocytosis

66
Q

what happens once chylomicrons leave the cell

A

a vesicle containing the triglyceride or chylomicron heads towards the cell membrane and are released by exocytosis and absorbed by the lacteal where is enters near the aorta back into the blood

67
Q

what is a micelle

A

a water soluble vesicle made up of bile salts, fatty acids, glycerol and monoglycerides

68
Q

what is the role of endopeptidases

A

hydrolyse peptide bonds between amino acids in the middle of the polymer chain

69
Q

what is the role of exopeptidases

A

hydrolyse peptide bonds between amino acids at the end of the polymer chain

70
Q

what is the role of dipeptidases

A

hydrolyses peptide bonds between 2 amino acids

71
Q

where does protein digestion start and go from there

A

starts in the stomach

continues in the duodenum

finally digested in the ileum

72
Q

describe the stages of protein digestion

A
  1. hydrolyse peptide bonds between amino acids
  2. endopeptidases hydrolyse peptide bonds between amino acids in the middle of the polypeptide chains to make smaller chains
    3.exopeptidases hydrolyse peptide bonds at the terminal amino acids
  3. dipeptidases hydrolyse dipeptides into amino acids
73
Q

describe how starch is completely broken down

A

amylases produced by the salivary glands hydrolyse starch into maltose (disaccharide)

pancreas releases amylases into duodenum for further hydrolyses

membrane bound dissaccharidase maltase hydrolyses matlose into glucose (monosaccharides)

74
Q

what is tissue fluid

A

fluid containing water, glucose, amino acids, fatty acids, ions and oxygen which bathes cells

75
Q

how is tissue fluid formed

A
  1. as blood enters the cappilleries at the arteriole end it results in a high hydrostatic pressure so water, ions, glucose, amino acids, fatty acids and oxygen are forced out in a process called ultrafiltration and the larger molecules remain in the capillery
76
Q

how is tissue fluid reabsorbed

A

there is now a water potential gradient as the water potential is higher outside of the capillary than inside it

towards the venule end of the capillary the hydrostatic pressure decreases so water re-enters the capillary by osmosis

77
Q

how is lymph formed

A

when an equilibrium is reached at the venule end the water that wont move down the concentration gradient by osmosis is absorbed into the lymphatic system and eventually drained back into the bloodstream near the heart

78
Q

what factors effect the rate of transpiration and why

A

light intensity- higher light intensity causes more stomata to open and therefore a larger SA for evaporation

temp- increase as more kinetic energy for the water molecules and therefore more evaporation

humidity- decreases transpiration as it reduced the water potential gradient

wind - increases transpiration as it will carry away the water vapour around the leaf increasing the water potential gradient

79
Q

what is transpiration

A

the loss of water vapour from the stomata

80
Q

why are companion cells important for phloem

A

provides the ATP required for the active transport of organic substances

81
Q

outline the mass flow hypothesis

A
  1. photosynthesis occuring in the chloroplasts of leaves creates organic substances
  2. sucrose is actively transported into the sieve tube elements via the companion cell and its ATP
  3. the increase in sucrose lowers the water potential in the sieve tube elements and as a result water moves into the sieve tube elements via osmosis from the xylem causing a high hydrostatic pressure forcing this liquid to a lower area of hydrostatic pressure
  4. sucrose is used in respiration at the sink cells or it is being stored as starch
  5. sucrose is actively transported from the sieve tube element into the sink cell causing the water potential to decrease and this results in osmosis of water from the sieve tube elements into the sink cells
  6. now a lower volume in the sieve tube elements and therefore a decrease in hydrostatic pressure
82
Q

how can you identify phloem in a plant

A

Tracers- radioactively labelling carbon that is used to create sugars and then thin slices from the stems are cut and places on an x-ray film and this shows where sugars are transported in the phloem

ringing experiment- bark and phloem are peeled and removed off of a tree trunk and this causes the trunk to swell above and this shows that sugars cant be transported without phloem and the sugary solution builds up and you can take samples of the liquid and prove it is sugars

a level biology (8 decks)

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