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Biology Alevel > Exchange (exhchange Between Organisms And Their Enviroment) > Flashcards

Exchange (exhchange Between Organisms And Their Enviroment) Flashcards

1
Q

What is surface area to volume ratio

A

The ratio between surface area and volume of an object

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2
Q

What is the ratio when an animal is very small

A

When a animal is very small it has a larger surface area when compared to its volume which means it has a larger surface area to volume ratio

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3
Q

What is the ratio when an animal is very large

A

Large animals have a smaller surface area compared to its volume therefore a smaller surface area to volume ratio

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4
Q

What ways do humans adapt their exchange surfaces

A

Alveoli In lungs
Villi in the small intestine

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5
Q

What have large organisms evolved

A

Large organisms have evolved one or more of the following features
-a flattened shape so that no cell is ever far from the surface (eg a leaf)
-specialised exchange surfaces with large areas to increase the surface area to volume ratio eg lungs in mammals and gills in fish

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6
Q

What is rate of diffusion dependent on

A

Surface area - rate of diffusion is directly proportional to the surface area. As the surface area increases the rate of diffusion increases
Concentration gradient - rate of diffusion is directly proportional to the difference in concentration across the gas exchange surface . The greater the concentration gradient the faster the diffusion
Thickness of the gas exchange surface - rate of diffusion is inversely proportional to the thickness of the gas exchange surface. The thicker the surface the slower the diffusion

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7
Q

What’s the structure of a leaf

A

Wax cuticle , palisade mesophyll , spongy mesophyll , lower epidermis , wax cuticle

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8
Q

What gases move in and out

A

Co2 diffuses in for photosynthesis and oxygen mainly moves into the air

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9
Q

What do plants need the gases for

A

Oxygen for respiration and carbon dioxide for photosynthesis

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10
Q

How do they diffuse into the leaf

A

The gases diffuse into the intercellular spaces of the leaf through pores which are normally on the underside of the leaf called stomata . Opening and closing of stomata is controlled by guard cells

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11
Q

What are the adaptations of a plant leaf for efficient gas exchange

A

-leaves are flat and often large to give a large surface area for gas exchange from the outside of the leaf
- thin leaves providing a short diffusion distance
-many stomata providing a short diffusion distance
-air spaces mean the gases can readily come in contact with mesophyll cells
-cells are very close to the external air , and therefore a source of oxygen and carbon dioxide
-mesophyll cells are vertical so more can fit also they have a large surface area for rapid diffusion of gases for photosynthesis

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12
Q

What happens to the leaf at night and day

A

When photosynthesis is taking place although some carbon dioxide comes from respiration of cells , most of it is obtained from the external air . In the same way some oxygen from photosynthesis is used in respiration but most of it diffuses out of the plant

When photosynthesis is not occurring for example in the dark , oxygen diffuses into the leaf because it is constantly being used by cells during respiration and co2 produced diffuses out

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13
Q

What is the function of the air spaces in the leaf

A

Move co2 and o2 through the leaf

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14
Q

What is the function of the palisade mesophyll

A

They have many chloroplasts than other plant cells to produce glucose . They are layed out vertical so many of them can be produced into the top layer of the leaf

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15
Q

What is the function of the xylem and phloem

A

Xylem moves water from roots to leaves ( absorbed from the soil through root hair cells and it is transported through the xylem vessels up the stem to the leaves ), phloem moves food substances from leaves to the rest of the plant . Both of these are rows of cells that make continuous tubes running the full length of the plant .

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16
Q

What’s the function of the stomata and guard cells

A

They open and close the stomata in the leaf this may occur when the plant has lost an excessive amount of water . They help regulate the rate of water loss . Gases diffuse through the stomata

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17
Q

What is the function of the spongy mesophyll

A

Not packed tightly together which allows carbon dioxide and oxygen to reach the palisade cells where they are needed in photosynthesis. Not much light

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18
Q

What is the function of the waxy cuticle

A

Thin , waxy covering to prevent water loss within the leaf by evaporation

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19
Q

What are some adaptations of cacti

A

They have large stems that can hold and store water for photosynthesis
Some have flowers to promote pollination
Thick waxy cuticle to reduce water loss
Less stomata to minimise water loss while still allowing for gas exchange for photosynthesis
Spines instead of leaves to deter predators
Widespread roots to obtain water From farther away

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20
Q

What is the transpiration stream

A

The movement of water from the roots through the xylem and out of the leaves

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21
Q

What are xerophytes

A

plants that are adapted to living in areas where water is in short supply . Without these adaptations plants would become desiccated and die

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22
Q

What is the main way of surviving in habitats where there is a high rate of water loss and limited supply of water

A

Reduce the rate at which water can be lost through the leaves ( evaporation / transpiration)

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23
Q

How is water lost through a plant

A

Photosynthesis requires a large leaf surface area for the capture of light and for the exchange of gases , this leads to water being lost because more leaf area means more stomata water is lost through

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24
Q

What do terrestrial plants have

A

A waterproof covering over parts of the leaves and the ability to close stomata when necessary

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25
Q

What are the 8 adaptations that xerophytes have

A
  • a thick cuticle - this increases diffusion distance and the less water can escape from the leaves by evaporation eg in holly leaves
    -rolling of leaves / rolled leaves - traps a region of moist air therefore trapping water vapour within a leaf , reducing the water potential gradient between the inside and outside of the leaf eg in marram grass
    -hairy leaves/ hairs - ( especially on the lower epidermis ) traps still moist air next to the leaf surface , trapping water vapour and therefore the water potential gradient is reduced eg heather plant
    -a reduced surface area to volume ratio of the leaves - by having small /circular leaves the rate of water loss by evaporation is reduced ( and normally reducing number of stoma and this is balanced with the need for a sufficient area for photosynthesis) eg pine trees
    -longer network of roots to reach more water
    -spines which reduces surface area to volume ratio ( as smaller than leaves )
  • stoma in pits or grooves - these trap still moist air therefore water vapour next to the leaf and reduce the water potential gradient
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26
Q

Suggest appropriate units the student should use to compare the distribution of stomata on leaves

A

Stomata per cm2

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27
Q

The leaf tissue examined was very thin explain why this is important

A

To see a single layer of cells so light can pass through

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28
Q

Give two reasons why it was important that the student counted the number of stomata in several parts of each piece of leaf tissue

A

To obtain a reliable mean
To get a representative sample

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29
Q

Suggest two reasons why the rate of water uptake by a plant might not be the same as the rate of transpiration

A

1) water is used in photosynthesis ( so uptake will be higher )
2) water produced in respiration ( so uptake will be lower )

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30
Q

Describe a method you could use to find the surface area of a leaf

A

Draw around leaf on graph paper , count the squares and multiply by 2

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31
Q

What features do fish have

A

Fish have a waterproof and therefore gas tight outer covering
Being relatively large they also have a small surface area to volume ratio

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32
Q

What are fish specialised internal gas exchange surface

A

The gills

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33
Q

What is the structure of the gills

A

Made up of gill filaments which are stacked in a pile . They have lamellae at right angles to the filaments to increase the surface area further

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34
Q

how do the fish get o2

A

water and blood flow through the lamellae in oppositte directions (antiparallel) this ensures that a steep concentration gradient is maintained across the entire length of the gill lamellae( this is known as countercurrent)

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35
Q

what features do the gills have

A
  • many lamellae so large surface area
    -large number of capillaries therefore maintains a diffusion gradient
    -thin lamellae walls therefore provides a short diffusion pathway
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36
Q

a disease causes lamellae to become thicker and to fuse together . agd recues the efficiency of gas exchange in fish . give two reasons why

A

1) surface area is decreased as lamellae fuse
2)thicker lamellae so greater diffusion distance

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37
Q

the volume of water passing over the gills increases if the temperature of the water increases suggest why

A

less oxygen dissolved in the water and incresed metabolism

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38
Q

suggest one advantage the fish have from the one way flow

A

less energy is needed

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39
Q

why is the countercurrent arrangement important for efficient oxygen uptake

A

to maintain a steep concentration gradient of oxygen across the whole length of lamelle therefore diffusin occurs across the whole length of gill

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40
Q

what features do single celled organisms have (insects)

A
  • single celled organisms have a large surface area to volume ratio
  • o2 and co2 are absorbed by diffusion across their body surface
    -where a living cell is surrounded by a cell wall this is no aditional barrier to the diffusion of gases
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41
Q

what gas exchange system do insects have

A

insects have evolved an internal network of tubes called tracheae which are supported by strengthened rings (cartilage) to prevent them from collapsing . the tracheae divide into smaller tubes called tracheoles which extend throughout all the body tissues of the insect. in this way oxygen is brought directly to the respiring tissues gases enter and leave tracheae through tiny pores called spiracles which run along the body surface

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42
Q

how is the air brought in quickly

A

atmospheric air is brought directly to the respiring tissues as there is a short diffusion pathway from a tracheole to any body cell

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43
Q

how do the respiratory gases move in and out of the tracheal system

A

in 3 ways
1) down a diffusion gradient - when cells are respiring 02 is used up so its concentration towards the ends of the tracheoles falls . this creates a concentration gradient between inside and outside of the insect so oxygen can diffuse by simple diffusion along the tracheae and tracheoles to the cells. carbon dioxide is produced by respiration creating a concentration gradient in the oppositte direction which therefore diffuses into the atmosphere
2) mass transport - muscles in abdomen contract and relax which can pump gases in and out
3)pressure changes - when insects are flying or carrying out activity muscle cells respire producing lactate lowering water potential therefore water moves from tracheoles into cells by osmosis . providing lower pressure in tracheoles and therefore gas from atmosphere diffuses into tracheal system

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44
Q

what are some features of terrestrial insects exoskeleton

A

have an exoskeleton made of hard fibrous material , chitin for protection and a lipid layer to prevent water loss

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45
Q

how do insects limit water loss

A
  • having a thin permeable surface with a large surface area is great for gas exchange , however these features conflict with the need to conserve water .
    they have evolved the following to reduce water loss
    1) small surface area to volume ratio where water can evapourate (spiracles)
    2)waterproof exoskeleton - chitin , water can only evapourate from spiracles
    3) spiracles - where gases can enter and exit or water can evapourate , can open and close to reduce water loss
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46
Q

what increases transpiration rate

A

windier / hotter conditions

47
Q

what are alveoli

A

the site of gas exchange

48
Q

which tube carries oxygen away from the alveoli

A

pulmonary vein

49
Q

what tube carries deoxygenated blood to the alveoli

A

pulmonary artery

50
Q

what are the adaptations of the alveoli

A

1) large surface area of the alveoli and and capillaries
2) extensive capillary network means that once oxygen diffuses into the blood its rapidly carried away from the alveoli this ensures there is always a steep concentration gradient for oxygen
3)alveolar epithelium - only one cell thick - therefore a short diffusion distance between air and blood
4) red blood cells are compressed against capillary wall to give a short diffusion distance
5) ventillation maintains steep concentration gradient
6) moist lining to promote rapid diffusion of gases
7)cells lining the alveoli and capillaries are flattened

51
Q

the volume of oxygen that has to be absorbed and the volume of carbon dioxide that must be removed are large in mammals because

A
  • they are relatively large organisms with a large volume of living cells
  • they maintain a high body temperature which is realted to them having a high metabolic and respiratory rate
52
Q

why are the lungs located inside the body

A

-because air is not dense enough to support and protect these delicate structures
-the body would then lose alot of water
-whereas gills are located on the outside as water is denser so can protect gills

53
Q

what adaptations does the nasal cavity have

A

when air passes through the nasal cavity hairs and mucus trap dust particles and pathogens .

54
Q

how is air constantly replenished

A

the lungs are ventillated by a tidal stream of air

55
Q

what is the wind pipe called

A

trachea

56
Q

what adaptations does the trachea have

A

1) supported by rings of cartilage , firm but flexible material which prevents the walls of the trachea collapsing when we inhale as the pressure falls
2) trachea walls lined with celiated epithelia and goblet cells which secrete mucus which traps dust particles and pathogens , cilia move this up towards the throat

57
Q

what are the 2 branches of the trachea called

A

right bronchus and left bronchus

58
Q

what are the smaller branches and air sacs

A

bronchioles and alveoli

59
Q

what do the bronchi do

A

carry air into the lungs , contain cartilage , celiated epithelia and golblet cells

60
Q

what do the bronchioles do

A

are made of muscle lined with epithelial cells , the muscle allows them to constrict so they can control air flow

61
Q

what is the proctective layer of the lungs called

A

ribs / ribcage

62
Q

what are the muscles called

A

externnal intercostal muscles ( over ribs )
internal intercostal muscles (under ribs )

63
Q

state two reasons why humans need to absorb large volumes of oxygen from the lungs

A
  • high metabolic rate
  • need to maintain a high body temperature
  • large volume of cells
64
Q

explain how the cells lining the trachea and bronchus protect the alveoli from damage

A
  • epithelial and goblet cells secrete mucus which traps dust and pathogens , the cilia on these cells moves the debris up the trachea and into the stomach . preventing pathogens getting into the alveoli and causing disease / infection
65
Q

what is ventilation

A

ventilation is the movement of gases in and out of the lungs, this maintains the diffusion of gases across the alveolar epithelium / alveoli

66
Q

describe inspiration

A

when air pressure of the atmosphere is greater than in the lungs , air is forced into the lungs

67
Q

describe expiration

A

when air pressure in the lungs is greater than the atmosphere , air is forced out of the lungs

68
Q

what are the internal intercostal muscles

A

whose contraction leads to expiration

69
Q

what are the external intercostal muscles

A

whose contraction leads to inspiration

70
Q

what is the diaphragm

A

a sheet of muscle that seperates the thorax from the abdomen

71
Q

what is pulmonary ventilation rate

A

total volume of air thats moved into the lungs during 1 minute
calculated by tidal volume x breathing rate

72
Q

whats tidal volume

A

normal volume of air displaced between normal inhilation and exhalation when extra effort is not applied

73
Q

describe what happens during inspiration ( breathing in)

A

1) the external intercostal muscles contract , while the internal intercostal muscles relax ribs move out
2) the volume of the thorax increases ( as airs coming in )
3) diaphragm contracts causing it to flatten
4) increased volume of the thorax results in reduction of pressure in the lungs
5) atmospheric pressure is now greater than in the lungs so air is forced in

74
Q

what happens during expiration

A

1) the external intercostal muscles relax , while the internal intercostal muscles contract
2) volume of the thorax decreases
3) diaphragm relaxes
4) decreased volume of the thorax results in an increase of pressure in the lungs
4) atmospheric pressure is now lower than in the lungs so air is forced out

75
Q

What is the role of the mouth

A

Physically chew and break down large food molecules into smaller ones

76
Q

What is the role of the salivary glands

A

Saliva contains salivary amylase which starts to hydrolyse carbohydrates into glucose

77
Q

What is the role of the oesophagus

A

Involves contraction and relaxation of the muscles (peristalsis) which moves the food from the mouth to the stomach

78
Q

What is the role of the liver

A

Produces bile which is an alkali and can neutralise acid from the stomach and emulsify fats

79
Q

What is the role of the gall bladder

A

Stores bile

80
Q

What is the role of the pancreas

A

Produces and releases digestive enzymes into the small intestine including pancreatic amylase and protease , lipases

81
Q

What is the role of the stomach

A

Contains muscle tissue which churns up food . It also releases protease from the glandular tissue which hydrolyses proteins . The optimum ph of protease is provided by HCl and kills any pathogens within the food

82
Q

What is the role of the large intestine

A

Water is absorbed here

83
Q

What is the rocks of the small intestine

A

Absorption of food molecules by digestive enzymes ,

84
Q

What is the definition for digestion

A

During digestion , large biological molecules are hydrolysed into smaller molecules that can be absorbed across cell membranes

85
Q

What is physical breakdown

A

If the food is large , it is broken down into smaller pieces by means of structures such as the teeth . This provides a large surface area for chemical digestion

86
Q

What is chemical digestion

A

This process hydrolyses large insoluble molecules into smaller soluble ones . It is carried out by enzymes which are specific si more than one is needed to hydrolyse a large molecule

87
Q

What are the 3 different types of digestive enzymes and there roles

A

Carbohydrases - hydrolyse carbohydrates (polysaccharides ) into monosaccharides
Lipases - hydrolyse lipids (fats and oils ) into glycerol and fatty acids
Proteases - hydrolyse proteins into amino acids

88
Q

What is the importance of bacteria in the digestive system

A

Can digest some substances that humans cannot digest
Reduce the chances of harmful bacteria multiplying and causing disease
Produce some vitamins that humans need such as vitamins b and k

89
Q

What is the process called when lipases digest

A

Emulsification and increases the surface area of the lipids so that the action of lipases is quicker

90
Q

Why do endopeptidases work

A

They increase the surface area for exopeptidases by creating more ends

91
Q

What are the carbohydrases and the steps to breakdown starch

A

Salivary amylase is used in the mouth and made in the salivary gland , it breaks down starch into disaccharide maltose . It hydrolyses the alternate glycosidic bonds in starch
Pancreatic amylase is used in the small intestine and produced in the pancreas , it breaks down starch into disaccharide maltose
Then maltase hydrolyses maltose into alpha glucose monosaccharides in the ileum / gut

92
Q

What are the other 2 carbohydrases

A

Sucrase - secreated in the small intestine and hydrolyses sucrose into glucose and fructose monosaccharides
Lactase - made in small intestine , hydrolyses lactose into galactose and glucose monosaccharides

93
Q

What’s lipase role

A

Lipases are produced in the pancreas and used in the small intestine. They break down lipid molecules into fatty acids and monoglycerides . Hydrolyse ester bonds found in triglycerides

94
Q

What are the protease enzymes

A

Endopeptidases - made in stomach or pancreas and used in the small intestine , hydrolyse proteins into a series of peptide molecules , hydrolyse peptide bonds between amino acids in the central region of a protein molecule to increase surface area for exopeptidases
Exopeptidases - made in stomach or pancreas and used in small intestine . Hydrolyse peptide bonds on the end amino acids / terminal amino acids after endopeptidases to produce dipeptides and amino acids
Dipeptidases- membrane bound - part of cell surface membrane of the epitheilial cells lining the ileum these hydrolyse the peptide bonds between two amino acids to. Produce amino acids

95
Q

Where does absorption take place

A

In the small intestine with hair like projections (villi)

96
Q

What are the sections of the small intestine

A

Duodenum , jejunum , ileum

97
Q

Where are villi

A

Villi are situated at the interface between the lumen and the blood . Each villi has microvilli to increase the surface area even more

98
Q

How do villi’s properties and adaptations increase the efficiency of absorption

A
  • they increase the surface area for diffusion
    -they are very thin walled (1 cell thick) providing a short diffusion distance
    -they contain muscle which allows them to move which helps to maintain concentration gradients by moving the contents of the ileum
    -well supplied with blood vessels which maintain a diffusion gradient
    They have microvilli which further increase the surface area
99
Q

How are monosaccharides and amino acids absorbed

A

Amino acids and monosaccharides are the products of digestion of carbohydrates and proteins and they are absorbed by diffusion and co transport

100
Q

What are the steps to lipid digestion

A

1)physical - emulsification and Micelle formation by bile salts
2) chemical - lipase

101
Q

What does emulsify mean

A

Break down

102
Q

What’s the first step

A

Bile is produced in the liver from cholesterol and stored in the gall bladder . It’s secreted into the small intestine from the liver
Bile salts emulsify large fat globules into tiny fat droplets
The bile salts contain hydrophobic and hydrophilic regions , they surround them which stops them re connecting

103
Q

What’s the advantage of bile salts

A

Many small droplets provide a larger surface area and therefore a faster hydrolysis action by lipase

104
Q

What’s the next step

A

Once the tiny lipid droplets are formed , lipase then hydrolyses the lipids into monoglycerides and fatty acids . These both remain in association with bile salts that initially emulsified the lipid droplets these structures are called micelles

105
Q

What are micelles

A

A sphere (vesicle) made up of phospholipids , monoglycerides, fatty acids , bile salts and glycerol ( as they cannot travel through the small intestine by themselves )

106
Q

What is the next step

A

Once the micelles are formed they come into contact with the epithelial cells lining the villi of the ileum , here the micelles break down releasing the monoglycerides and fatty acids which diffuse across the cell surface membrane into the epithelial cells as they are non polar

107
Q

What’s the next step

A

Once inside the epithelial cells , monoglycerides and fatty acids are transported to the smooth endoplasmic reticulum / Golgi apparatus where they are reformed into triglycerides and these associate with cholesterol and lipoproteins to form chylomicrons and then once packaged by the Golgi apparatus the chylomicrons move out of the epithelial cells by exocytosis and enter lymphatic capillaries called lacteals which are found at the centre of each villus

108
Q

What’s the last step

A

The chylomicrons travel via lymphatic vessels around the body and eventually drain into the blood system . The triglycerides in the chylomicrons are hydrolysed by an enzyme in the endothelial cells of the blood capillaries they then diffuse into cells

109
Q

What does the Golgi apparatus do

A

Processes triglycerides and then combines them with proteins which are packaged for exocytosis

110
Q

Describe the processes involved in the absorption and transport of digested lipid molecules from the ileum into lymph vessels

A

Micelles form and contain bile salts , fatty acids and monoglycerides
These make monoglycerides and fatty acids more soluble in water and carry them to the lining of the ileum
The fatty acids and monoglycerides are absorbed by diffusion
The triglycerides are reformed in cells
And the chylomicrons move to cell membrane by exocytosis

111
Q

What is a tissue

A

A group of similar cells organised into a structural unit that serves a particular function

112
Q

What is an organ

A

A group of tissues

113
Q

What’s an organ system

A

A group of organs that work together to perform one or more functions

114
Q

Explain three ways in which an insects tracheal system is adapted for efficient gas exchange

A
  • tracheoles have thin walls so short diffusion distance to cells
    -large number of tracheoles so large surface area for gas exchange
    -fluid in the end of tracheoles that moves out into tissues during exercise so faster diffusion through the air to the gas exchange surface

Biology Alevel (13 decks)

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